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1
Rodrigues, Rodrigo Antonio de Freitas, Juliana Pertille, Fernanda Gervasoni, et al. "Tonian Continental Arc Magmatism of the Porongos Complex, Dom Feliciano Belt, Southern Brazil." Geologia USP. Série Científica 23, no. 3 (2023): 19–45. http://dx.doi.org/10.11606/issn.2316-9095.v23-208078.
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This study provides new information on the deformation, metamorphism, and tectonic setting of the metavolcanic rocks of the southern portion of the Porongos Complex, southern Brazil. The structural analysis enabled the identification of three deformational phases, formed under ductile to semi-ductile conditions. D1 progressed through deformation partitioning, comprising closed to isoclinal folds and an axial plane foliation. Then, simple shear prevailed, resulting in isoclinal folds, sigma-type porphyroclasts, foliation transposition, and mylonitic rocks. D2 comprises open to gentle folds and an axial plane cleavage. The formation of shear bands is ascribed to the semi-ductile D3. The mineral assemblage represented by phengite + chlorite + clinozoisite-epidote + actinolite + albite + quartz associated with the temperatures obtained through the chlorite geothermometer (316°C) indicates greenschist facies conditions. The protoliths of these metavolcanic rocks are geochemically discriminated as calc-alkaline, dacite-to-rhyodacite, with peraluminous compositions. The bulk trace element compositions show enrichment in large-ion lithophile elements and light rare-earth elements and depletion in heavy rare-earth elements. Also, negative Nb, P, Ti, and Ta anomalies are observed in the multielement diagram. All these geochemical features are typical of rocks formed in continental magmatic arcs. Geochemical comparison with other pre-collisional Tonian orthometamorphic rocks from the Dom Feliciano Belt demonstrates strong similarities, which corroborates the prior interpretation of a continental arc setting for the origin of these Tonian rocks.
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Prokopyev, I. R., A. G. Doroshkevich, M. D. Varchenko, D. V. Semenova, I. A. Izbrodin, and M. N. Kruk. "MINERALOGY AND ZIRCON AGE OF CARBONATITES OF THE SREDNYAYA ZIMA COMPLEX (EASTERN SAYAN)." Geodynamics & Tectonophysics 15, no. 2 (2024): 0749. http://dx.doi.org/10.5800/gt-2024-15-2-0749.
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The Srednyaya Zima alkaline-ultramafic carbonatite complex is located in the Eastern Sayan and is a part of the area of manifestation of Neoproterozoic rare-metal alkaline-carbonatite magmatism along the southern and southeastern margins of the Siberian craton. Mineralogical studies of calciocarbonatites of the Srednyaya Zima complex have shown the presence of primary magmatic mineral phases of calcite, biotite (annite-phlogopite), ilmenite, and fluorapatite. Pyrochlore, zircon, burbankite, magnetite, rutile, titanite, strontianite, and barite were identified of the accessory minerals. The chemical composition of the magmatic minerals of the Srednyaya Zima carbonatites is similar to the mineral composition of the closely aged carbonatite complexes Belaya Zima and Arbarastakh. The rare-element and structural analysis of zircon from carbonatites showed the presence of two zones – a magmatic core and areas of recrystallization. U-Pb dating of igneous zircon showed the age interval of its crystallization – 637±4 Ma, which coincides with the geochronology of the formation of alkali-ultramafic rare-metal complexes along the southern margin of the Siberian craton. The formation of Neoproterozoic alkaline-carbonatite complexes is associated with tectonic events of the breakup of the Rodinia supercontinent.
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Belenitskaya, G. A. "On the participation of natural salts in alkaline magmatism. Article 3. Genetic aspects of the model of salt-alkaline interactions." LITHOSPHERE (Russia) 21, no. 2 (2021): 172–97. http://dx.doi.org/10.24930/1681-9004-2021-21-2-172-197.
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Research subject. An analysis of regional and global geological material characterizing the spatio-temporal relationships between alkaline magmatic and saline complexes allowed the author to propose and justify a new geological-genetic model of alkaline magmatism. This model considers saline complexes, located along the paths of the upward movement of deep magmas, as additional sources of alkaline and volatile components.Materials and methods. Three articles are devoted to the discussion and justification of this model. Two articles were devoted to geological aspects of the problem. The prerequisites and signs of the participation of ancient saline complexes in alkaline magmatism were characterized. It was shown that the presence of saline rocks in the deep zones of the earth's crust along the paths of the upward movement of deep magma flows is a geologically natural and common phenomenon. Natural alkaline-salt associations (spatio-temporal combinations of alkaline and salt objects) were indicated; their tectonic types were distinguished. A global overview of their different-age analogues (neo- and paleogeodynamic) was given.Results and discussion. The collected data made it possible to evaluate older (than magmas) salt-bearing complexes (deeply buried in the substrate) as a possible important and active participant in the ontogenesis of alkaline complexes, to give a positive assessment of the geological aspects of the “magma halocontamination” model and salt-magmatic interactions; to formulate the main geological-genetic provisions of this model.Conclusion. This article focuses on the discussion of the genetic aspects of the proposed model with an assessment of the probable role and significance of various halophilic components in the formation of alkaline magmas and their features. For this purpose, the similarity features in the spatial and quantitative distribution of halophilic and foydaphilic components in salt and alkaline rocks are considered; the probable role of various halophilic components in the formation of alkaline specialization of magmas, in the emergence of a rich set of unusual features of alkaline rocks (material, structural, morphological, etc.) is discussed. The probability of participation of the complex of paragenic (non-salt) members of the halophilic community (dolomites, anhydrites, black shales and associated ore components) in the interaction with hot magma is estimated. A comparative analysis of some basic provisions of the model under consideration with other geological-genetic models of alkaline petrogenesis is performed. The advantages of this model and its predictive capabilities are evaluated. A number of ideas have been proposed by the author for the first time, thus requiring further elucidation.
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Grebennikov, A. V., S. A. Kasatkin, and A. I. Khanchuk. "ISOTOPIC AND GEOCHEMICAL ZONALITY OF THE PALEOCENE MAGMATISM IN THE ASIA-PACIFIC TRANSITION ZONE." Tikhookeanskaya Geologiya 43, no. 5 (2024): 54–73. http://dx.doi.org/10.30911/0207-4028-2024-43-5-54-73.
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The diversity of the tholeiitic, alkali or calc-alkali, high-silica, and adakitic rocks (I-, FG- and А-types) in the northeastern margin of Asia often leads to controversial conclusions about the character of magmatism and the active margin evolution in the West Pacific during the Late Mesozoic–Cenozoic. In addition, paleogeodynamic reconstructions of the Asia-Pacific region can only be made based on the synthesis of patterns identified in compositions of magma sources, evolution and character of magmatism, and strain and kinematic analysis of fault tectonics of all parts of the eastern margin of the paleo-Asian continent. The paper presents new isotopic, geochemical, and structural data on one of the largest early Paleogene structures located at the continental margin of the southern Sikhote-Alin. Based on the new and previously published [49, 52] data we have concluded that the tectonic and magmatic settings of the region were shaped by oblique interaction of continental and oceanic plates during the Late Cretaceous-early Paleogene. The igneous products of the frontal (FG-type), in respect to the trench, and intracontinental (А-type) parts of the area are characterized by isotopic-geochemical variations caused by thermal changes in upwelling asthenosphere and by interaction with lithospheric components. These processes accounted for the formation of initial magmas similar to the IAB- or OIB-type mantle source, respectively.
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Bortolozzo, Rômulo, Rafael Rodrigues de Assis, Lorenzzo Cassaro, and Lays Helmer Mengal. "Metallogenic characterization of the Aguinaldo structurally-controlled Epithermal gold occurrence, Alta Floresta Gold Province (Brazil)." Geologia USP. Série Científica 24, no. 4 (2024): 39–62. https://doi.org/10.11606/issn.2316-9095.v24-194388.
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In the eastern-southeast sector of Alta Floresta Gold Province (Amazon Craton), the 1.78 – 1.77 Ga calc-alkaline magmatism is interpreted as answerable for ore-forming processes responsible for its disseminated, vein-type, and filonar gold occurrences hosted in 2.05 – 1.77 Ga units. The Aguinaldo structurally-controlled gold occurrence exhibits ore zones hosted in 0.5 – 1.5m thick quartz + sulfide ± carbonate veins crosscutting the porphyroblastic mylonite orthogneiss, with SHRIMP U-Pb-zircon concordia crystallization age of 1,984.9 ± 5.2 Ma. Distal to ore zones are observed high temperature, intensive, and pervasive (1) albite-rich alteration, followed by (2) K-Feldspar alteration, telescoped by lower temperature pervasive alterations: (3) sericite-muscovite alteration, (4) silicification and silica infills; (5) carbonate alteration, (6) chlorite alteration, and (7) late veinlet-type quartz. The silica injection represents one of the major hydrothermal stages due to generating barren quartz veins and quartz ± carbonate vein with chalcopyrite + pyrite ± gold ± silver ± sphalerite ± galena ± bismuthinite veins. Although the veins are partially deformed, local comb-quartz texture remains preserved. Gold occurs as small inclusions or in contact with pyrite and chalcopyrite, and subordinately, in sphalerite. Electron microprobe analysis indicates chlorite of brunsvigite composition formed between 242° and 420° C, whereas white mica shows low phengite contents. The polymetallic veins signature, the high chalcopyrite contents with galena and sphalerite inclusions, the comb-texture quartz veins, together with the hydrothermal alteration sequence, suggest low to moderate temperature, neutral to slightly alkaline pH, and moderate ƒO2 and ƒS2 conditions, possibly triggered by boiling process. This scenario indicates intermediate-sulfidation epithermal ore-forming processes as the responsible for the genesis of Aguinaldo gold occurrence.
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Lebedev, V. A., G. T. Vashakidze, A. V. Parfenov, and A. I. Yakushev. "The origin of adakite-like magmas in the modern continental ollision zone: evidence from pliocene dacitic volcanism of the Akhalkalaki lava plateau (Javakheti highland, Lesser Kaucasus)." Петрология 27, no. 3 (2019): 327–51. http://dx.doi.org/10.31857/s0869-5903273327-351.
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The paper reports the isotope-geochronological and petrological-geochemical studies of the Pliocene moderately-acid volcanism of the Akhalkalaki Plateau in the central part of the Lesser Caucasus (Javakheti highland, Georgia). K-Ar dating showed that young dacitic lavas and pyroclastic rocks were formed in the Mid-Pliocene (3.28 ± 0.10 Ma) in relation with the explosive–effusive eruptions of small composite volcanic cones and formation of minor extrusive domes confined mainly to the eastern margin of the region. Isotope-geochronological data in the combination with results of structural drilling indicate that the considered short-term pulse of the volcanic activity occurred during a short gap between two phases of the Pliocene–Early Pleistocene mafic magmatism widespread within the Akhalkalaki plateau. The studied Pliocene dacites were erupted at the post-collisional stage of the evolution of the Lesser Caucasus, but bear petrological-geochemical affinity of adakitic series. They are characterized by the steady presence of amphibole phenocrysts, the elevated contents of Sr, Ba, LILE and the lowered contents of Y, Nb, Ta, and HREE, and have depleted Sr isotopic composition (87Sr/86Sr < 0.7045). Analysis of petrogenetic models earlier proposed to explain the generation of adakite-like magmas in the modern collision zones showed that the origin of the Pliocene dacitic lavas of the Akhlkalaki plateau is best described by the crystallization differentiation of watersaturated calc-alkaline basaltic melts with removal of common mafic rock-forming minerals (first of all, amphibole and pyroxene) and accessory phases (apatite, titanite, Ti-magnetite) as cumulus minerals. Crustal assimilation of evolved magmas only insignificantly contributed to the petrogenesis of the dacites.
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Slaman, L. R., S. M. Barr, C. E. White, and D. van Rooyen. "Age and tectonic setting of granitoid plutons in the Chéticamp belt, western Cape Breton Island, Nova Scotia, Canada." Canadian Journal of Earth Sciences 54, no. 1 (2017): 88–109. http://dx.doi.org/10.1139/cjes-2016-0073.
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Geological mapping in the Chéticamp granitoid belt in combination with petrographic and geochemical studies and U–Pb (zircon) dating by laser ablation inductively coupled plasma mass spectrometry have resulted in major reinterpretation of the geology in the western part of the Ganderian Aspy terrane of Cape Breton Island. Nine new U–Pb (zircon) ages show that the former “Chéticamp pluton” consists of 10 separate plutons of five different ages: late Neoproterozoic (ca. 567 Ma), Cambrian–Ordovician (490–482 Ma), Ordovician–Silurian (442–440 Ma), mid-Silurian (ca. 428 Ma), and late Devonian (366 Ma). The three late Neoproterozoic granodioritic to monzogranitic plutons are older than the adjacent metavolcanic and metasedimentary rocks of the Jumping Brook Metamorphic Suite, whereas the tonalitic to quartz dioritic Cambrian–Ordovician plutons intruded those metamorphic rocks. Petrographic characteristics and approximately 100 whole-rock chemical analyses show that with the exception of the mid-Silurian Grand Falaise alkali-feldspar granite, which has A-type within-plate characteristics, the plutonic units have calc-alkaline affinity and were emplaced in a volcanic-arc tectonic setting. These results are evidence that fragments of a long history of episodic subduction-related magmatism and terrane collision are preserved in this small part of Ganderia. Eight new Sm–Nd isotopic analyses are consistent with the Ganderian affinity of the Chéticamp plutonic belt. The ca. 490–482 Ma plutons are the first direct evidence in Cape Breton Island for the Penobscottian event recognized in the Exploits Subzone of central Newfoundland and in New Brunswick. However, the structural relationship of the Chéticamp plutonic belt to the rest of the Aspy and Bras d’Or terranes remains enigmatic, as is the apparent absence of effects of Devonian deformation and metamorphism in the older plutonic units.
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Baluev, A. S., Yu V. Brusilovsky, and A. N. Ivanenko. "The crustal structure of Onega-Kandalaksha paleorift identified by complex analysis of the anomalous magnetic field of the White Sea." Geodynamics & Tectonophysics 9, no. 4 (2018): 1293–312. http://dx.doi.org/10.5800/gt-2018-9-4-0396.
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Geological and geophysical studies recently conducted in the White Sea and the adjacent territory have provided new data on the deep structure of this region. Our study aims to conduct complex analysis of the anomalous magnetic field and the geological and geophysical data on the Onega-Kandalaksha paleorift located in the White Sea basin and the adjacent southeastern land area, and to develop a model showing its deep structure. The basis for analysing the magnetic field is the anomalous magnetic field (AMF) map constructed by the authors using the magnetic survey data consolidated by the Marine Arctic Geological Expedition (MAGE) in 2003–2008 and supplemented by the survey data of the Institute of Oceanology RAS in 2001–2004. The parameters of the magnetically active layer are estimated by the independent complementary methods of quantitative interpretation developed by the Laboratory of Geophysical Fields, P.P. Shirshov Institute of Oceanology RAS. This article describes a model showing the structure and formation of the magnetically active layer of the White Sea paleorift. Our study shows that the magnetically active layer of the paleorift system has a complex structure reflecting all the main stages in the evolution of tectonic activity in the White Sea region, from the Middle and Late Riphean to the last glaciation of the Quaternary period. The model includes three structural layers, each corresponding to a certain stage. The bottom structural layer is the base of the magnetically active layer, which reflects the continental rifting stage in the evolution of the White Sea mobile belt in the Middle and Late Riphean. The middle structural layer reflects the Middle Paleozoic (Late Devonian) stage of rifting reactivation, which is characterized by alkaline-ultrabasic magmatism and represented by swarms of alkaline dykes and diatremes, including kimberlite pipes. The top structural layer reflecting a high-frequency component of the AMF is related to the highly magnetic sources of anomalies located in the upper part of this structural layer. The characteristics of the top structural layer suggest that it formed in the Late Pleistocene – Holocene and developed during the final stage the tectonic activation of this region. The deep crustal structure of the White Sea basin is specified in our model showing the magnetically active layer for the low-frequency component of the AMF. In the southeastern part of the basin, magmatism products of the basic (Riphean – Vendian) and alkaline-ultrabasic (Middle Paleozoic) composition are abundant in the crust and provide for a strong magnetic source of anomalies, the lower edges of which are traced at the depths to 30 km. This probably reflects the most active plume-lithospheric interaction. Wedging and uplifting of the magnetically active layer northwestward along the Onega-Kandalaksha rift is related to the White Sea (Belomorsky) deep fault. This fault is a long-lived conduit that channels magma from the central portion of the plume, as evidenced by the igneous bodies of the basic composition in the basement and central parts of the sedimentary wedge in the Kandalaksha graben. The complex analysis of the AMF in the White Sea region suggests the presence of morphologically different igneous bodies in the upper crust in the study region.
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Lawali Idi Chamsi, Sanda Chékaraou Mahamane Moustapha, Ibrahim Maharou Hassane, Hamza Mayaki Issoufou, and Ahmed Yacouba. "Structural relationships of the younger granites of Tirmini (Damagaram south-east, Niger)." World Journal of Advanced Research and Reviews 21, no. 3 (2023): 2201–6. http://dx.doi.org/10.30574/wjarr.2024.21.3.0853.
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The Tirmini anorogenic ring complex is located approximately 25 km west of the town of Zinder, in the pan-African province of Damagaram-Mounio, the southeastern terminus of the Benin-Nigeria Shield. The aim of this study is to characterise the anorogenic deformation affecting the Tirmini younger granites. The petrography of Tirmini evolves from rhyolites to microgranites, granites and quartz alkaline syenite emplaced during anorogenic magmatism in the Permian (295 Ma). Very little structural data is available on the Tirmini complex. Only a cursory study of deformation has been carried out, without characterisation of the stages of anorogenic deformation or structural interpretation. The aim of this study is to characterise the structural evolution of the Tirmini younger granites. The methodology used is based on the exploitation of satellite imagery and mapping, supported by an analysis of deformation carried out in the field using Canvas software. The geological structures revealed include 360° schistosities, fracture schistosities, detachments (dexter and sinistral) anµ diaclases. The rheology of these structures has revealed two chronologically marked stages of anorogenic deformation (i) semi-ductile to brittle, Sd1, and (ii) frankly brittle, Sd2. The first stage of deformation is contemporaneous with magmatic activity, producing 360° schistosities linked to magma swelling and fracture schistosities (S1: N45°-N60° and S2: N75°-N95°) associated with the emplacement of granites and syenite. The second brittle stage, Sd2, is characterised by a system of conjugate dextral and sinistral detachments and two families of diaclases (F1: N45°-N60° and F2: N120°-N150°) associated with the emplacement of the pluton and the cooling of the magma.
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Lawali, Idi Chamsi, Chékaraou Mahamane Moustapha Sanda, Maharou Hassane Ibrahim, Mayaki Issoufou Hamza, and Yacouba Ahmed. "Structural relationships of the younger granites of Tirmini (Damagaram south-east, Niger)." World Journal of Advanced Research and Reviews 21, no. 3 (2024): 2201–6. https://doi.org/10.5281/zenodo.14175438.
Full textAbstract:
The Tirmini anorogenic ring complex is located approximately 25 km west of the town of Zinder, in the pan-African province of Damagaram-Mounio, the southeastern terminus of the Benin-Nigeria Shield. The aim of this study is to characterise the anorogenic deformation affecting the Tirmini younger granites. The petrography of Tirmini evolves from rhyolites to microgranites, granites and quartz alkaline syenite emplaced during anorogenic magmatism in the Permian (295 Ma). Very little structural data is available on the Tirmini complex. Only a cursory study of deformation has been carried out, without characterisation of the stages of anorogenic deformation or structural interpretation. The aim of this study is to characterise the structural evolution of the Tirmini younger granites. The methodology used is based on the exploitation of satellite imagery and mapping, supported by an analysis of deformation carried out in the field using Canvas software. The geological structures revealed include 360° schistosities, fracture schistosities, detachments (dexter and sinistral) anµ diaclases. The rheology of these structures has revealed two chronologically marked stages of anorogenic deformation (i) semi-ductile to brittle, Sd1, and (ii) frankly brittle, Sd2. The first stage of deformation is contemporaneous with magmatic activity, producing 360° schistosities linked to magma swelling and fracture schistosities (S1: N45°-N60° and S2: N75°-N95°) associated with the emplacement of granites and syenite. The second brittle stage, Sd2, is characterised by a system of conjugate dextral and sinistral detachments and two families of diaclases (F1: N45°-N60° and F2: N120°-N150°) associated with the emplacement of the pluton and the cooling of the magma.
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Maylin Marisel Mendoza Mondragon. "Lithogeochemical Characterization and Alteration Model to Determine its Implication in the Controls of the Mineralization of the VMS Cerro Lindo Deposit." Journal of Information Systems Engineering and Management 10, no. 12s (2025): 157–65. https://doi.org/10.52783/jisem.v10i12s.1770.
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The objective of this study is to characterize, using lithogeochemistry, the magmatic series and the enclosing rock that took place in the formation of the Cerro Lindo VMS; At the same time, alteration lithogeochemistry was performed to determine the relationship between mineralogy, lithogeochemistry and intensity of alteration, obtaining as a result, vectors towards the center of the system. The primary purpose is to bring this 2D information from the lithogeochemical diagrams to a 3D approach, and thus establish correlations with other mineral occurrence controls (structural, geophysical, geochemical, and lithological). From the analysis and interpretations it was determined that Cerro Lindo belongs to a calc-alkaline magmatic series with high K content, the box rock definitely corresponds to felsic volcanic with degree of differentiation from andesite to rhyodacite according to the degree of proximity to economic zones; that is to say, the deposit is located in the oldest bimodal felsic level of the Casma basin, and it is these first stages of rupture that are usually better enriched in economic mineralization contents, mainly of base elements, followed by the presence of Ag*-Au, It is precisely this location that makes it much more powerful than the other VMS in the area. The SerK+ChlFe (Py) alteration halo has greater potency and dominance in deep, lower-angle faults, which have brought economic Zn-Cu mineralization (NW-SE and NE-SW), faults related to high- grade bodies and to high chargeability areas; while the shallow NW-SE faults, with greater angles, which bring low-grade mineralization and related to low chargeability edge bodies, would correspond to the Ser-Chl alteration and towards the most distal zones of the system, the SerNa-Chl alteration appears. Chl Mg.
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Kalashnyk, G. A. "Results of geological and geophysical research on the Subotska structure of Ingulskiy megablock of the Ukrainian shield." Мінеральні ресурси України, no. 4 (December 28, 2020): 4–12. http://dx.doi.org/10.31996/mru.2020.4.4-12.
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The article presents the results of diamond prospecting studies in the Subotska structure of the Inhulskyi megablock of Ukrainian Shield. For the results, it is indicated that the Subotska structure is mimicked by crater rocks and in some cases by manifestations of the vent facies with signs of kimberlitic-lamproitic magmatism. The typical local features of manifestations of explosive structures from maar volcanism in Subotska area are determined. The article presents the results of petrographic and mineralogical study of the core material from exploratory wells on the Subotska structure, the results of study of material composition of the clay fraction, X-ray diffraction analysis of the pellet fraction. Data of the X-ray structural analysis of the pellet fraction of samples taken from the core material from exploratory wells on the Subotska structure indicates the obvious mechanical sum, the head folder of such is calciferous montmorilonite, and also saponite, nontronite, hydromica and kaolinit. The availability of the nontronite and saponite is confirmed by the results of electronic-microscopic reports. Also the article presents the results of studying the secondary lithochemical halos of Cr, Ni, Mg, Co, Ti, V, Fe, covering the geochemical spectrum inherent in alkaline-ultrabasic rocks and their weathering crust. These halos are combined with negative gravitational anomalies associated with the explosive structures in the Subotska area. The structural control of the great part of the detected geochemical anomalies, geochemical halos are determined. According to the degree of manifestation of the complex of criteria five potential diamond-prospective structures are discovered on the Subotska area. There were developed recommendations for further research on the Subotska area.
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Deng, Shiqi, and Yang Wang. "The Indosinian Granitoids of the Songpan–Garze–West Kunlun Orogenic Belt, China: Distribution, Petrochemistry, and Tectonic Insights." Minerals 14, no. 11 (2024): 1060. http://dx.doi.org/10.3390/min14111060.
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During the Indosinian orogeny, the Songpan–Garze–West Kunlun orogenic belt experienced significant tectonic and magmatic activity, leading to the widespread emplacement of granitoid bodies. This study provides a detailed petrochemical and geochemical analysis of these granitoids, offering new insights into their tectonic settings and magmatic evolution. The granitoids of this belt are systematically categorized into arc calc-alkaline and arc tholeiitic granitoids (ACG and ATG), cordierite peraluminous and muscovite peraluminous granitoids (CPG and MPG), potassium calc-alkaline granitoids (KCG), and peralkaline granitoids (PAG) suites. ACG and ATG types dominate early magmatism (230–190 Ma), reflecting a convergent tectonic setting, while KCG and MPG types magmatism, respectively, emerged 10–20 Myr and 15–25 Myr later, during post-collisional extensional phases. Geochemical analyses show that ACG and ATG granitoids follow calcic and calc-alkalic trends, while KCG and MPG display alkalic characteristics. These findings align with the region’s tectonic transition from the closure of the Paleo–Tethys Ocean to Late Triassic transpressional deformation. This study enhances the understanding of granitoid petrogenesis and provides valuable implications for regional tectonic evolution and mineral exploration.
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A.M, Shuaibu. "STRUCTURAL ANALYSIS, PETROGRAPHIC STUDY AND GEOCHEMICAL ASSESSMENT OF PAN-AFRICAN GRANITOID, GUSAU SHEET 54SE NORTHWEST NIGERIA." Malaysian Journal of Geosciences 7, no. 1 (2023): 50–63. http://dx.doi.org/10.26480/mjg.01.2023.50.63.
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The study area is underlain by migmatite-gneiss quartzite rock suits with infolding mica schist which is intruded by batholitic Pan-African granitoids. Petrographic studies revealed quartz, orthoclase, hornblende and biotite as major minerals which are common to all members of rock units. The geochemical result of gneissic rock shows SiO2 content that range between 77.04%.wt to 80%.wt while mica schist depicts SiO2 content of 74.42 to 77.42%.wt. this implies silicious protolith for the both rock units. On the discrimination diagram gneiss and mica schist plot mainly in High-K calc-alkaline to calc-alkaline fields. Whereas, bivariate diagram of TiO2 versus SiO2 revealed that both gneissic rock and mica schist have sedimentary progenitors. High Rb, La and Th and low Nb, Sr, and Ti values shown by both gneiss and mica schist are compatible with typical crustal melts and suggest evolution from partial melting of crustal materials. The Pan-African granitoids has similar geochemical relationships. Geochemical studies shows that the rock units have limited variation in their major element compositions and give a decrease in CaO wt. %, and increasing Ba/Sr, Zr/Y ratios, K2O wt. % with increasing silica. The rocks are distinctly peraluminous, calc-alkaline as they plot in the High-K calc-alkaline and calc-alkaline, syn-collision fields on various discrimination diagrams. The characteristics suggest that the Basement rocks of the study area were formed from the fractional crystallization of a calc-alkaline magma in a syn- collision tectonic terrain.
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Zhuravlev, A. I., A. V. Okrugin, B. B. Gerasimov, et al. "Native gold from placers of the Evotinskii region (Aldano-Stanovoy Shield): mineralogical and geochemical features, and possible primary sources." Arctic and Subarctic Natural Resources 29, no. 4 (2024): 511–26. https://doi.org/10.31242/2618-9712-2024-29-4-511-526.
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The Evotinskii Ore and Placer Region (EOR) is located in the central part of the Aldano-Stanovoy Shield and is characterized by a significant presence of gold-bearing placers, many of which have undergone extensive mining activities. Despite geological investigations that have been conducted since the 1930s, the main sources of numerous placers remain largely unidentified. This study employed traditional mineralogical and geochemical methods, along with LA-ICP-MS analysis, to investigate placer gold within the Evotinskii Ore and Placer Region. The findings indicate that native gold within the placers of the EOR is predominantly represented by particles measuring between 0.1 and 1.2 mm, which primarily exhibit forms of cementation, fracture, and interstitial characteristics. The degree of roundness varies, and high-fineness shells and intergranular high-fineness veins are not uncommon. Structural etching revealed a multi-phase, granular, concentric, and vaguely zonal internal structure of the native gold. Furthermore, granulation and twinning structures were also identified. The LA-ICP-MS analysis of the native gold from the placers indicated a diverse array of trace element impurities within the particles. These extensive investigations suggest that the primary sources of placer gold are likely to be ore occurrences similar to the P. Pinigin deposit, as well as sulfide and epithermal occurrences associated with alkaline Mesozoic magmatism, which are prevalent in the Central-Aldan ore region. The possibility of a certain amount of gold originating from mineralizations associated with porphyry systems and iron ore deposits cannot be excluded. The discovery of ore-like particles may signify the proximity of bedrock sources and enhances the potential of the region for the discovery of previously unidentified ore occurrences.
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Goodenough, K. M., B. N. Young, and I. Parsons. "The minor intrusions of Assynt, NW Scotland: early development of magmatism along the Caledonian Front." Mineralogical Magazine 68, no. 4 (2004): 541–59. http://dx.doi.org/10.1180/0026461046840207.
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AbstractThe Assynt Culmination of the Moine Thrust Belt, in the northwest Scottish Highlands, contains a variety of Caledonian alkaline and calc-alkaline intrusions that are mostly of Silurian age. These include a significant but little-studied suite of dykes and sills, the Northwest Highlands Minor Intrusion Suite. We describe the structural relationships of these minor intrusions and suggest a classification into seven swarms. The majority of the minor intrusions can be shown to pre-date movement in the Moine Thrust Belt, but some appear to have been intruded during the period of thrusting. A complex history of magmatism is thus recorded within this part of the Moine Thrust Belt. New geochemical data provide evidence of a subduction-related component in the mantle source of the minor intrusions.
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Fyson, W. K., and H. Helmstaedt. "Structural patterns and tectonic evolution of supracrustal domains in the Archean Slave Province, Canada." Canadian Journal of Earth Sciences 25, no. 2 (1988): 301–15. http://dx.doi.org/10.1139/e88-032.
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A new plate-tectonic model accounts for lithological relations and regional structural patterns in late Archean supracrustal domains of the Slave Province. Multiple dykes and pillowed mafic flows, most common in the western part of the province, suggest sea-floor spreading. The mafic volcanics, lying in narrow homoclinal belts stratigraphically below more extensive turbidites, are viewed as megaxenolithic remnants of oceanic crust preserved on the periphery of granitoid plutons and blocks of sialic crust. Closure of an oceanic basin was marked by emplacement of the granitoid plutons and coeval felsic volcanics, the latter predominating over mafic volcanics in northeastern domains. The felsic calc-alkaline magmas may have risen from a shallow-dipping subduction zone. Westerly verging folds, westerly convex fold arcs, and inclinations of later foliations, particularly in lower level rocks of higher metamorphic grade, are in accord with underthrusting to the east. The zone of underthrusting shifted progressively westward, and calc-alkaline magmatism swept across the western part of the province. Plutons followed crustal fracture systems, some of which were inherited from initial rifts, producing a rectilinear zigzag pattern of contacts between plutons, and mafic volcanics. The fracture systems and rising plutons redirected stresses, resulting in distinctive sets of regional and local foliations that reflect crustal compression only indirectly related to the sense of subduction.
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Widana, Kurnia Setiawan, and Bambang Priadi. "Karakteristik Unsur Jejak Dalam Diskriminasi Magmatisme Granitoid Pulau Bangka." EKSPLORIUM 36, no. 1 (2015): 1. http://dx.doi.org/10.17146/eksplorium.2015.36.1.2766.
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Geologi Pulau Bangka disusun oleh variasi granit sebagai Granitoid Klabat yang tersebar di berbagai lokasi. Unsur jejak dapat diaplikasikan dalam diskriminasi magmatisme dalam pembentukan granitoid tersebut. Tujuan penelitian ini adalah mengetahui karakteristik granitoid yang tersebar di Pulau Bangka berdasarkan geokimia unsur jejak untuk diaplikasikan dalam mempelajari magmatisme, sumber dan situasi tektoniknya.Metode analisis geokimia yang diaplikasikan dengan menggunakan Analisis Aktivasi Neutron (AAN) dan portableX-Ray Fluorescence (pXRF) untuk analisis kualitatif dan kuantitatif pada 27 sampel dari Granitoid Klabat di Pulau Bangka.Hasil penelitian ini menyimpulkan Granitoid Bangka Utara (Belinyu) dan Bangka Tengah sebagai percampuran kerak-mantel dengan afinitas Calc-Alkaline, karakteristik Tipe I sedangkan Granitoid Bangka Selatan dan Barat asal kerak dengan afinitas High-KCalc-Alkaline sebagai Tipe S. Diharapkan diskrimasi magmatisme granitoid bermanfaat dalam memberikan panduan eksplorasi bahan galian nuklir di Pulau Bangka. Geology of Bangka Island consists by variation of granite as Klabat Granitoid scattered in various locations. Trace elements can be applied in magmatism discrimination of granitoid.The purpose of this study was to determine the characteristics Bangka Island granitoid based on trace element geochemistry to be applied in the study of magmatism, source and tectonic situation. Geochemical analyses method used are the Neutron Activation Analysis (NAA) and portableX-Ray Fluorescence (pXRF) for qualitative and quantitative analyses on 27 samples of Klabat granitoid on Bangka Island. This study concluded granitoid East Bangka (Belinyu) and Central Bangka as crust-mantle mixing with affinityCalc-Alkaline, characteristic of I Type while South and West Bangka granitoid crust origin with affinity high K Calc-Alkaline as S Type. Expectedmagmatismdiscrimination ofgranitoidhelpfulin providingradioactive mineral explorationguidein BangkaIsland.
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Percival, J. A., V. McNicoll, and A. H. Bailes. "Strike-slip juxtaposition of ca. 2.72 Ga juvenile arc and >2.98 Ga continent margin sequences and its implications for Archean terrane accretion, western Superior Province, Canada." Canadian Journal of Earth Sciences 43, no. 7 (2006): 895–927. http://dx.doi.org/10.1139/e06-039.
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The North Caribou terrane of the western Superior Province attained continental thickness (~35 km) by 2997 Ma. It records a subsequent 300 million years history of continental fragmentation, arc magmatism, and terrane accretion. At Lake Winnipeg the ~2978 Ma Lewis–Storey quartzite–komatiite–iron formation assemblage marks Mesoarchean breakup. Unlike the relatively continuous 2980–2735 Ma stratigraphic record of the Red Lake and Birch–Uchi greenstone belts to the east, little of this interval is recorded at Lake Winnipeg. Rather, two belts of younger, juvenile rocks are tectonically juxtaposed: the Black Island assemblage of isotopically depleted, 2723 Ma basalt, and calc-alkaline andesite; and Rice Lake greenstone belt of basalt, calc-alkaline andesite, and dacite (2731–2729 Ma). Collectively these terranes represent a short-lived island-arc–back-arc system that docked with the southwestern North Caribou margin along a northwest-trending, dextral, transpressive, D1 suture. This zone is marked by the highly deformed coarse clastic Guano Island sequence (<2728 Ma) that contains detritus of North Caribou affinity and is interpreted as a strike-slip basin deposit. Younger clastic sequences, including the Hole River (<2708 Ma), San Antonio (<2705 Ma), and English River (<2704 Ma) assemblages, occur in east–west belts that may have been deposited during the terminal collision (D2, D3) between the North Caribou terrane and continental crust of the Winnipeg River terrane to the south. Several terrane docking events within a framework of north-dipping subduction and continental arc magmatism appear necessary to explain structural and stratigraphic relationships in the 2735–2700 Ma interval.
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Xu, Nan, Cai-lai Wu, Yuan-Hong Gao, Min Lei, Kun Zheng, and Dong Gao. "Tectonic evolution of the South Altyn, NW China: constraints by geochemical, zircon U–Pb and Lu–Hf isotopic analysis of the Palaeozoic granitic plutons in the Mangya area." Geological Magazine 157, no. 7 (2020): 1121–43. http://dx.doi.org/10.1017/s0016756820000126.
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AbstractThe South Altyn Orogenic Belt (SAOB) is one of the most important orogenic belts in NW China, consisting of the South Altyn Continental Block and the Apa–Mangya Ophiolitic Mélange Belt. However, its Palaeozoic tectonic evolution is still controversial. Here, we present petrological, geochemical, zircon U–Pb and Lu–Hf isotopic data for the Mangya plutons with the aim of establishing the Palaeozoic tectonic evolution. We divide the Early Palaeozoic magmatism in the Apa–Mangya Ophiolitic Mélange Belt into four episodes and propose a plate tectonic model for the formation of these rocks. During 511–494 Ma, the South Altyn Ocean (SAO) was in a spreading stage, and some shoshonite series, I-type granitic rocks were generated. From 484 to 458 Ma, the oceanic crust of the SAO subducted northward, accompanied by large-scale magmatic events resulting in the generation of vast high-K calc-alkaline series, I-type granitic rocks. During 450–433 Ma, the SAO closed, and break-off of the subducted oceanic slab occurred, with the generation of some high-K calc-alkaline series, I–S transitional type granites. The SAOB was in post-orogenic extensional environment from 419 to 404 Ma, and many A-type granites were generated.
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Cui, Yao, and J. K. Russell. "Magmatic origins of calc-alkaline intrusions from the Coast Plutonic Complex, southwestern British Columbia." Canadian Journal of Earth Sciences 32, no. 10 (1995): 1643–67. http://dx.doi.org/10.1139/e95-131.
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Major element, trace element, and rare earth element data are presented for Permian to Tertiary calc-alkaline plutonic and volcanic rocks along a transect across the southern Coast Plutonic Complex from Vancouver to Anderson Lake. Late Jurassic to Late Cretaceous plutons are divided into two compositional suites based on mineralogy: (1) the hornblende intrusive suite (tonalite, quartz diorite, diorite, and gabbro) characterized by abundant modal hornblende and little or no K-feldspar, and (2) the K-feldspar intrusive suite (mainly granite and granodiorite) containing significant modal K-feldspar and less hornblende. Compositions of hornblende intrusive suite rocks are effectively portrayed on Pearce element-ratio diagrams utilizing axes X1 = [0.8571 Si−0.1429(Fe + Mg) + 1.2857 Ca + 1.8574 K]/Zr and Y1 = 1.1428 Ti + Al + Fe + Mg + Ca + 1.5714 Na + 0.4762 P]/Zr, because the diagram accounts for the stoichiometry of PI ± Hbl ± Bt ± Ep ± Ttn + Ap. Rocks from the K-feldspar intrusive suite are studied on diagrams using the element-ratio pair X2 = [2 Ti + Al + 3.3333 P]/Zr and Y2 = [2 Ca + Na + K]/Zr, which creates a linear trend of compositional variations controlled by the phases PI ± Kfs ± Bt ± Ttn + Ap. Mean intercepts of model trends on the element-ratio diagrams suggest differences among plutons that relate to source-region processes. For example, samples belonging to the hornblende intrusive suite represent a minimum of six batches of magma. Mean intercept values for plutons west of the Owl Lake–Harrison fault zone are significantly higher than those situated east of this structural break. These systematic differences allude to fundamental differences in the nature of Mesozoic magmatism in Wrangellia (and Harrison) terrane compared with that in Cadwallader, Bridge River, and Methow terranes, and probably in the Intermontane superterrane east of the structural break.
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Abdelfadil, Khaled M., Sherif Mansour, Asran M. Asran, et al. "Composite Granitic Plutonism in the Southern Part of the Wadi Hodein Shear Zone, South Eastern Desert, Egypt: Implications for Neoproterozoic Dioritic and Highly Evolved Magma Mingling during Volcanic Arc Assembly." Minerals 14, no. 10 (2024): 1002. http://dx.doi.org/10.3390/min14101002.
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The Abu Farayed Granite (AFG), located in the southeastern desert of Egypt, was intruded during the early to late stages of Pan-African orogeny that prevailed within the Arabian–Nubian Shield. The AFG intrudes an association of gneisses, island arc volcano–sedimentary rocks, and serpentinite masses. Field observations, supported by remote sensing and geochemical data, reveal a composite granitic intrusion that is differentiated into two magmatic phases. The early granitic phase comprises weakly deformed subduction-related calc–alkaline rocks ranging from diorite to tonalite, while the later encloses undeformed granodiorite and granite. Landsat-8 (OLI) remote sensing data have shown to be highly effective in discriminating among the different varieties of granites present in the area. Furthermore, the data have provided important insights into the structural characteristics of the AFG region. Specifically, the data indicate the presence of major tectonic trends with ENE–WSW and NW–SE directions transecting the AFG area. Geochemically, the AFG generally has a calc–alkaline metaluminous affinity with relatively high values of Cs, Rb, K, Sr, Nd, and Hf but low contents of Nb, Ta, P, and Y. The early magmatic phase has lower alkalis and REEs, while the later phases have higher alkalis and REEs with distinctly negative Eu anomalies. The AFG is structurally controlled, forming a N–S arch, which may be due to the influence of the wadi Hodein major shear zone. The diorite and tonalite are believed to have been originally derived from subduction-related magmatism during regional compression. This began with the dehydration of the descending oceanic crust with differential melting of the metasomatized mantle wedge. Magma ascent was long enough to react with the thickened crust and therefore suffered fractional crystallization and assimilation (AFC) to produce the calc–alkaline diorite–tonalite association. The granodiorite and granites were produced due to partial melting, assimilation, and fractionation of lower crustal rocks (mainly diorite–tonalite of the early stage) after subduction and arc volcanism during a late orogenic relaxation–rebound event associated with uplift transitioning to extension.
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Ariani, Rizky Putri, and Hari Wiki Utama. "Petrogenesis and Geological Structure of Tantan Granitoid in Sungai Manau District, Merangin Regency, Jambi Province." EKSPLORIUM 43, no. 2 (2023): 79. http://dx.doi.org/10.17146/eksplorium.2022.43.2.6415.
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Tantan granitoids are Late Triassic–Early Jurassic age intrusive rocks that are quite extensive and can be partially found in Sungai Manau Sub-district, Merangin Regency, Jambi Province. Tantan granitoids are found in the Barisan Hills physiography, a magmatic arc line on Sumatra Island. Tantan granitoids are interesting to observe to explain rock formation. The petrographic and XRF analyses can provide insight into the intrusive rock type, its relationship to the tectonic framework, and magmatism. The trend of potential mineral resources can be interpreted based on the granitoid-type approach. The Tantan Granitoid Intrusion has two types of rocks: granite and quartz monzodiorite. Granite and quartz monzodiorite are sub-alkaline magma types, with the granitoid type being I-type metaluminous, which tends to have potential with base metal minerals associated with hornblende minerals from observations or petrographic analysis. Based on the TAS diagram of Na2O+K2O vs. SiO2 shows that the sub-alkaline magma type is a calc-alkaline series type in the K2O vs. SiO2 diagram and a calc-alkaline type in the AFM diagram. This data analysis shows that the tectonic formation of the Tantan Granitoid magma was formed from orogenic results in the form of a Continental Arc. This type can be associated with Meso-Thetic subduction activities against the West Sumatra Sundablock during the Late Triassic–Early Jurassic. Structures in the study area include northwest-southeast trending horizontal faults, including Batang Tantan Fault, Tiangko Fault, Sei Tengko Fault, and Serik Fault, then northeast–southwest trending regional faults, and relatively downward trending faults, namely Serik Fault and Betung Fault. The formation of fault structures is believed to result from subduction tectonic processes during this period.
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Wang, Kun, Dan Yang, Ke-Jun Hou, and Qian Wang. "In Situ LA-ICP-MS U-Pb Geochronology, Sr-Nd-Hf Isotope and Trace Element Analysis of Volcanic Rocks from the Gacun Volcanic-Hosted Massive Sulfide Deposit in Sichuan, China." Minerals 13, no. 7 (2023): 881. http://dx.doi.org/10.3390/min13070881.
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The Gacun deposit is a typical Volcanic Hosted Massive Sulfide (VHMS) associated with Late Triassic seafloor calc-alkaline felsic volcanics. Studies of zircon ages, petrology, major and trace element geochemistry, and Sr-Nd-Hf isotope geochemistry of volcanic rocks from the Northern Yidun arc were undertaken in this paper. We reshaped the Gacun magmatic system activity time, defined the origin of magma evolution, and proposed a metallogenic model of the deposit. Whole-rock major element compositions of the magmatic rocks in the Northern Yidun island arc indicate that they are a complete basalt–andesite–dacite–rhyolite assemblage, showing three obvious stages of composition evolution. They are enriched in large-ion lithophile and light rare earth elements, but depleted in high field-strength and heavy rare earth elements, with weak-to-negligible Eu anomalies (obvious in rhyolite). These geochemical features indicate that the Northern Yidun island arc is a magmatic arc based on ancient continental crust. The Ganzi–Litang oceanic subduction induced mantle melting and produced calc-alkaline basaltic magma, while the MASH processes at the bottom of the crust produced andesitic magma. Part of the andesite magma erupted to form andesite lava. The remaining part was mixed with magma produced via anatexis of ancient crust (approximately 20%–40% of the ancient crustal component), forming the ore-bearing rhyolite. Zircon U-Pb age data defines Gacun magmatic–hydrothermal mineralization sequence of events: At 238 Ma, arc magmatism led to the formation of andesite in the eastern part of the deposit. At 233 Ma, in the arc zone (the western part of Gacun deposit), a large-scale bimodal magmatism formed the main ore-bearing rock series of Gacun deposit, rhyolitic volcanic rocks. At 221 Ma, volcanic eruptions tended to end and sub-volcanic intrusion occurred, forming a lava dome, which was located under the ore-bearing rhyolitic volcanic rocks. The lava dome acted as a thermal engine and promoted hydrothermal circulation. The hydrothermal activity reached a peak at 217 ± 1 Ma, and the Gacun VHMS deposit was formed.
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Korovin, Dmitriy Dmitrievich. "Geochemical features of the devonian plutonic rocks of the Reftinsky massif (Middle Urals)." NEWS of the Ural State Mining University 1, no. 1 (2022): 13–21. http://dx.doi.org/10.21440/2307-2091-2022-1-13-21.
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This article examines the Devonian plutonic rocks of two massifs – Khomutinsky and Yuzhno-Khomutinsky, which are located in the western part of the Reftinsky massif. The rocks of the Khomutinsky and Yuzhno-Khomutinsky massifs are divided into gabbroid and granitoid associations. Their chemical composition, the content of pertrogenic, rare and trace elements were studied. Based on the data obtained, the rocks were assigned to the calc-alkaline series, according to the ratio of sodium and potassium, they are rocks with a sodium type of alkalinity. The peculiarity of the studied formations lies in the differences in the nature of alkalinity, thus the rocks of the gabbroid association in terms of the K2 O content are transitional from low to moderate potassium varieties, and the rocks of the granitoid association are characterized by a sufficiently high potassium content and correspond to the high potassium calc-alkaline series. Comparative analysis with basalts and granites of island arcs allows us to conclude that the Khomutinsky and YuzhnoKhomutinsky massifs were formed in an island arc geodynamic setting. Relevance. The geochemical features of the rocks of the Devonian intrusions in the Eastern zone of the Middle Urals have been studied very poorly to date, which makes it difficult to restore the geodynamic conditions of their formation and compare the processes of magmatism in the East of the Middle Urals with other regions of the mobile belt. The data presented in the work will make it possible to fill the existing gap to some extent and thereby help to clarify the patterns of magmatism evolution and the history of the formation of the Urals. The purpose of the work. Study of the contents of petrogenic, rare and trace elements of the Khomutinsky and Yuzhno-Khomutinsky massifs. Comparison of the geochemical features of the rocks of these intrusions with similar formations formed in island-arc geodynamic conditions. Research methodology. The chemical composition of rocks was studied by the X-ray fluorescence method, which was performed on a multichannel spectrometer SRM-35 with the determination of losses on ignition by the gravimetric method and the determination of the content of ferrous iron by the titrimetric method. Analysis of the content of rare and trace elements in rocks was carried out on inductively coupled plasma mass spectrometers ELAN 9000 and NexION 300S. Analytical data are presented in the form of discrimination diagrams. Results. The rocks of the Khomutinsky and Yuzhno-Khomutinsky massifs are divided into gabbroid and granitoid associations. Based on the obtained geochemical data, the rocks were assigned to the calc-alkaline series. According to the ratio of sodium and potassium, they are rocks with a sodium type of alkalinity. It is shown that the rocks of the gabbroid and granitoid associations differ in the character of alkalinity. The former in terms of K2O content are transitional from low to moderate potassium varieties, the latter are characterized by a fairly high content of potassium and correspond to the high potassium calc-alkaline series. Conclusion. Comparison of the studied rocks in terms of geochemical features with basalts and granites of island arcs allows us to conclude that the Khomutinsky and Yuzhno-Khomutinsky massifs were formed in an island-arc geodynamic setting.
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Muhtar, M. N., Chang-Zhi Wu, M. Santosh, et al. "Late Paleozoic tectonic transition from subduction to post-collisional extension in Eastern Tianshan, Central Asian Orogenic Belt." GSA Bulletin 132, no. 7-8 (2019): 1756–74. http://dx.doi.org/10.1130/b35432.1.
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Abstract Late Paleozoic large-scale transcurrent tectonics and synkinematic intrusions are prominent features in the Eastern Tianshan segment of the southwestern Central Asian Orogenic Belt. However, the spatial and temporal relationship between synkinematic intrusions and crustal-scale shear zones remains unclear. Here we report petrology, geochemistry, and geochronology of the Qiziltag pluton associated with the Kanggur-Huangshan Shear Zone (KHSZ) with a view to characterize the spatial and temporal relationship between synkinematic intrusions and large-scale transcurrent shearing. Field relations and zircon U-Pb ages indicate that the Qiziltag pluton was formed through two stages of magmatism, with earlier stage granitoids (gneissic biotite granite: 288.9 ± 1.9 Ma, biotite monzogranite: 291.5 ± 1.7 Ma, K-feldspar granite: 287.9 ± 3.1 Ma), and later stage bimodal intrusions (biotite quartz monzonite: 278.5 ± 1.8 Ma, gabbro: 278.1 ± 2.3 Ma). The earlier stage granitoids are high-K calc-alkaline, enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs; e.g., Rb, Th, and U), and depleted in high field strength elements (HFSEs; e.g., Nb, Ta, and Ti). Combined with their depleted isotopic compositions (εNd(t) = +6.29 to +7.48) and juvenile model ages (TDM2 = 450–610 Ma), we infer that the granitoids were derived from juvenile lower crust in a post-collisional tectonic transition (from compression to extension). The structural and temporal features indicate that the earlier stage (ca. 290 Ma) granitoids formed prior to the regional large-scale dextral strike slip. The later stage bimodal intrusions are dominated by biotite quartz monzonite as the felsic member and gabbro as the mafic component. The biotite quartz monzonite is high-K calc-alkaline with enriched LREEs and LILEs (e.g., Rb, Th, and U), and depleted HFSEs (e.g., Nb, Ta, and Ti), whereas the gabbro is subalkalic with depleted LREEs and HFSEs (e.g., Nb and Ta), resembling normal mid-ocean ridge basalt features. The bimodal intrusions show similar isotopic compositions (εNd(t) = +6.41 to +6.72 and εHf(t) = +9.55 to + 13.85 for biotite quartz monzonite; εNd(t) = +9.13 to +9.69 and εHf(t) = +4.80 to +14.07 for gabbro). These features suggest that the later stage (ca. 280 Ma) bimodal intrusions were derived from partial melting of depleted mantle and anatectic melting of lower crust materials induced by synchronous underplating of basaltic magma in a post-collisional extension. The structural features of the bimodal intrusions indicate that the later stage (ca. 280 Ma) magmatism was coeval with the development of the KHSZ. In conjunction with spatial and temporal evolution of magmatism and sedimentary records of Eastern Tianshan, we infer that transition between the northward closure of the North Tianshan Ocean and subsequent collision between the Central Tianshan Massif and the Qoltag Arc belt occurred at ca. 300 Ma.
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Kilias, Adamantios. "The Alpine Geological History of the Hellenides from the Triassic to the Present—Compression vs. Extension, a Dynamic Pair for Orogen Structural Configuration: A Synthesis." Geosciences 14, no. 1 (2023): 10. http://dx.doi.org/10.3390/geosciences14010010.
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In this paper, the Hellenic orogenic belt’s main geological structure and architecture of deformation are presented in an attempt to achive a better interpretation of its geotectonic evolution during Alpine orogeny. This study was based not only on recent research that I and my collaborators conducted on the deformational history of the Hellenides but also on more modern views published by other colleagues concerning the Alpine geotectonic reconstruction of the Hellenides. The structural evolution started during the Permo–Triassic time with the continental breaking of the supercontinent Pangea and the birth of the Neotethyan ocean realm. Bimodal magmatism and A-type granitoid intrusions accompanied the initial stages of continental rifting, followed by Triassic–Jurassic multiphase shallow- and deep-water sediment deposition on both formed continental margins. These margins were the Apulian margin, containing Pelagonia in the western part of the Neotethyan Ocean, and the European margin, containing continental parts of the Serbo-Macedonian and Rhodope massifs in the eastern part of the Neotethyan ocean. Deformation and metamorphism are recorded in six main deformational stages from the Early–Middle Jurassic to the present day, beginning with Early–Middle Jurassic Neotethyan intra-oceanic subduction and ensimatic island arc magmatism, as well as the formation of a suprasubduction oceanic lithosphere. Compression, nappe stacking, calc-alkaline magmatism, and high-pressure metamorphic events related to subduction processes alternated successively over time with extension, orogenic collapse, medium- to high-temperature metamorphism, adakitic and calc-alkaline magmatism, and partial migmatization related to the uplift and exhumation of deep crustal levels as tectonic windows or metamorphic core complexes. A S- to SW-ward migration of dynamic peer compression vs. extension is recognized during the Tertiary Alpine orogenic stages in the Hellenides. It is suggested that all ophiolite belts in the Hellenides originated from a single source, and this was the Neotethyan Meliata/Maliac-Axios/Vardar ocean basin, parts of which obducted during the Mid–Late Jurassic on both continental margins, Apulian (containing Pelagonia) and European (containing units of the Serbo-Macedonian/Rhodope nappe stack), W-SW-ward and E-NE-ward, respectively. In this case, the ophiolite nappes should be considered far-traveled nappes on the continental parts of the Hellenides associated with the deposition of Middle–Late Jurassic ophiolitic mélanges in basins at the front of the adjacent ophiolite thrust sheets. The upper limit of the ophiolite emplacement are the Mid–Upper Jurassic time(Callovian–Oxfordian), as shown by the deposition of the Kimmeridgian–Tithonian Upper Jurassic sedimentary carbonate series on the top of the obducted ophiolite nappes. The lowermost Rhodope Pangaion unit is regarded as a continuation of the marginal part of the Apulian Plate (External Hellenides) which was underthrust during the Paleocene–Eocene time below the unified Sidironero–Kerdylia unit and the Pelagonian nappe, following the Paleocene–Eocene subduction and closure of a small ocean basin in the west of Pelagonia (the Pindos–Cyclades ocean basin). It preceded the Late Cretaceous subduction of the Axios/Vardar ocean remnants below the European continental margin and the final closure of the Axios/Vardar ocean during the Paleocene–Eocene time, which was associated with the overthrusting of the European origins Vertiskos–Kimi nappe on the Sidironero–Kerdylia nappe and, subsequently, the final collision of the European margin and the Pelagonian fragment. Subsequently, during a synorogenic Oligocene–Miocene extension associated with compression and new subduction processes at the more external orogenic parts, the Olympos–Ossa widow and the Cyclades, together with the lower-most Rhodope Pangaion unit, were exhumed as metamorphic core complexes.
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HaraHap, Bhakti H. "Magma Genesis in Kabanjahe Region Continental Margin Arc of Sumatra." Indonesian Journal on Geoscience 6, no. 2 (2011): 105–27. http://dx.doi.org/10.17014/ijog.6.2.105-127.
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DOI: 10.17014/ijog.v6i2.120Volcanic rocks in Kabanjahe region, Karo Regency, North Sumatra Province, are products of old Toba Caldera, Sibayak Volcano, and Sipiso-piso Volcano. Rhyolitic tuff is the main lithology distributed over a large area in this region. Others are basaltic, basaltic andesitic, andesitic, dacitic, and rhyolitic lavas. Data show that the rock was originated from magma of a continental origin formed at a subduction zone environment. Petrogenetic modelling suggests that the range in composition was mainly controlled by a fractional crystallization of plagioclase, clinopyroxene, hornblende, and biotite. Harker’s variation diagram of major and trace elements show a continuous range that indicates they are cognate. The lava in this area belongs to a high-K, calc-alkaline series, with particular high Nb concentrations. The composition of these high-Nb lavas is more similar to those of intra plate basalts rather than those of calc-alkaline or arc-tholeiitic basalt. The high anomaly of Nb which is accompanied by high Th, Rb, and normative corundum suggests that the source may also be enriched in incompatible elements, a characteristic feature of alkali magmatism. The similarity of the trace element of volcanic rocks to the within-plate basalts indicates that the convecting mantle wedge above subducted slabs contains variable proportions of MORB-source and OIB-source components; fluids added were derived from the subducted slab. Hence, it is interpreted that the high Nb concentration of volcanic rocks from Kabanjahe region were generated from subduction modified OIB source components. Alternatively, a deep seated faulting conduit magma from the lower mantle resulted in the alkaline enrichment of the volcanics. This article performs a petrological aspect, especially based on geochemical analysis including major elements, trace elements, and rare earth elements. The results are plotted into a general and specific classification used in petrology.
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Wang, Wenyi, Shuang Tan, Jianjun Wan, Xuelian Hu, Haoyang Peng, and Chengdong Liu. "Insights from Dikes for Multistage Granitic Magmatism in the Huayangchuan Uranium Polymetallic Deposit, Qinling Orogen." Minerals 14, no. 3 (2024): 261. http://dx.doi.org/10.3390/min14030261.
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The Huayangchuan U-polymetallic deposit in the Qinling Orogen is a newly verified carbonatite-hosted deposit on the southern margin of the North China Craton (NCC) in Central China. Granitic magmatism is extensively developed in the Huayangchuan deposit area and is lacking analysis on the reasons for these situations; however, its ages, petrogenesis, and relationship with uranium mineralization are not well constrained. Zircon U–Pb ages for the hornblende-bearing granite porphyry and medium-fine-grained biotite granites in close proximity to carbonatite rocks are 229.8 ± 1.1 and 135.3 ± 0.6 Ma, respectively. High-K calc-alkaline series and weakly peraluminous Triassic hornblende-bearing granite porphyry are slightly enriched in light rare earth elements (LREE) with flat heavy rare earth element (HREE) patterns, enriched in Ba and Sr, and depleted in Nb, Ta, P, and Ti, i.e., geochemical characteristics similar to those of adakite-like rocks. The Early Cretaceous medium-fine-grained biotite granites are characterized by LREE enrichment and flat HREE patterns, which belong to high-K calc-alkaline series, and metaluminous belong to weakly peraluminous I-type granite, with U and large ion lithophile element (LILE) enrichment and high field strength element depletion. The high initial 87Sr/86Sr ratios and enriched Nd (εNd(t) = −10.7 to −9.5 and −19.9 to −18.9, respectively) and Hf (εHf(t) = −21.8 to −13.0 and −30.5 to −19.0, respectively) isotopes revealed that both granitic rocks from the Huayangchuan deposit mainly originated from lower crustal materials, generated by partial melting of the ancient basement materials of the Taihua Group. Triassic hornblende-bearing granite porphyry is significantly different from the mantle origin of the contemporaneous U-mineralization carbonatite. In combination with tectonic evolution, we argue that the Qinling Orogenic Belt was affected by the subduction of the North Mianlian Ocean during the Late Triassic. The ongoing northward subduction of the Yangtze Craton resulted in crustal thickening, forming large-scale Indosinian carbonatites, U-polymetallic mineralization, and contemporaneous intermediate-acid magmatism. Additionally, due to the tectonic system transformation caused by Paleo-Pacific Plate subduction, intracontinental lithosphere extension and lithospheric thinning occurred along the southern NCC margin in the Early Cretaceous. Intense magma underplating of the post-orogeny created a large number of magmatic rocks. The tremendous heat could have provided a thermal source and dynamic mechanism for the Yanshanian large-scale U-polymetallic mineralization events.
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MacLachlan, Kate, and Greg Dunning. "U-Pb ages and tectono-magmatic evolution of Middle Ordovician volcanic rocks of the Wild Bight Group, Newfoundland Appalachians." Canadian Journal of Earth Sciences 35, no. 9 (1998): 998–1017. http://dx.doi.org/10.1139/e98-050.
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The Wild Bight Group and spatially associated South Lake Igneous Complex form one of the Ordovician oceanic terranes of the central mobile belt of the Newfoundland Appalachians. An integrated study of these rocks, involving detailed mapping, geochemistry, Sm-Nd isotopic analyses and U-Pb geochronology, has shown that there are two temporally and genetically distinct volcanic sequences within the Wild Bight Group. The younger sequence comprises a lower volcanic succession associated with coarse volcaniclastic rocks and an upper volcanic succession interbedded with argillite, chert, and minor greywacke. The lower volcanic succession has calc-alkaline affinties, and isotopic evidence for minor crustal contamination. It is interpreted to represent a volcanic arc formed in proximity to the Gondwanan margin, above an east-dipping subduction zone. The age of this volcanic sequence is confined to 472 ± 3 Ma by felsic tuffs which occur stratigraphically above and below it. The upper volcanic unit has predominantly enriched tholeiitic to alkaline geochemical characteristics with isotopic signatures indicative of little or no crustal contamination, and is interpreted to represent arc rifting. The age of this sequence was determined indirectly by dating two geochemically related gabbro sills (472+2-9 Ma and 471 ± 4 Ma). This work shows that despite different lithologies and stratigraphic and structural relationships between Early and Middle Ordovician sequences in the northern and southern Exploits Subzone, they have undergone essentially the same tectono-magmatic events. The age constraints on the magmatic events in the Wild Bight Group provide evidence for the timing of "obduction" of Early Ordovician oceanic sequences and the reversal of subduction polarity along the Gondwanan margin, suggested by previous workers.
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Kuzmenkova, O. F., A. G. Laptsevich, and A. A. Nosova. "The upper devonian magmatic complexes of the South-East Belarus." Doklady of the National Academy of Sciences of Belarus 64, no. 5 (2020): 599–608. http://dx.doi.org/10.29235/1561-8323-2020-64-5-599-608.
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For the first time, the authors determined lateral-temporal series of magmatic complexes of the Late Frasnian-Early Famennian Pripyat-Dnieper Magmatic Area according to the results of petrological and geochemical study of rocks of the Pripyat-Dnieper Magmatic Area (north-western part of the Pripyat-Dnieper-Donetsk Magmatic Province) in the southwest of the East European Platform using the principles of structural-material analysis and taking into account previous studies. The series consists of four complexes, formed during stages of magmatic activity, separated by time intervals: Zhlobin Complex (Rechitsa Time, the beginning of the Late Frasnian), Uvarovichi complex (Late Voronezh Time, the middle of the Late Frasnian), Pripyat Complex (Skolodin (Skolodin-Chernin?) Time, the end of the Late Frasnian) and Loev complex (Yelets (Yelets- Petrikov?) Time, Early Famennian). The rocks of the Zhlobin Complex belong to the alkaline-ultramafic (carbonatite-kimberlite-nephelinite) formation; Uvarovichi Complex - to the alkaline-mafic formation (basaltoids and phonolites); Pripyat Complex - to the alkaline-mafic-salic formation (trachyandesites); Loev Complex - to the alkaline-ultramafic (nepheline) formation.
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BOZKURT, ERDİN, JOHN A. WINCHESTER, MUHARREM SATıR, QUENTIN G. CROWLEY, and CHRISTIAN J. OTTLEY. "The Almacık mafic-ultramafic complex: exhumed Sakarya subcrustal mantle adjacent to the İstanbul Zone, NW Turkey." Geological Magazine 150, no. 2 (2012): 254–82. http://dx.doi.org/10.1017/s0016756812000556.
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AbstractThe Almacık Mountains in northwestern Turkey expose an upper-amphibolite-facies complex consisting of alternating ultramafic (harzburgitic and websteritic) and mafic (metagabbroic) rock types. In the eastern part of this complex are island arc meta-tholeiites and transitional to calc-alkaline metabasites that are chemically quite similar to those of the Permo-Triassic Çele mafic complex north of Bolu, and this suggests an equivalence. However, much of the section exposes structurally deeper and chemically different mafic and ultramafic rocks, which have no equivalent in the Çele mafic complex, and isotopic dating has suggested that these rocks also formed during the Permian period and underwent Triassic and Jurassic metamorphism. Furthermore, sparse inherited ages, unlike those from İstanbul Zone granitoids, suggest a link with North African-derived Armorican-type basement (and hence the Sakarya Zone), rather than Amazonia-derived Avalonian basement. Alternating mafic and ultramafic rocks suggest structural repetition, supported by the exposure of discrete high-strain zones or poorly exposed shattered rock west of each outcrop of ultramafic rocks. The high grade of metamorphism, and the absence of either extrusive lavas or sheeted dyke rocks, suggests that the Almacık complex was not an ophiolite, but formed instead as subcontinental lower crust and subjacent mantle. Dominantly calc-alkaline geochemistry suggests that it formed the basement to an active continental margin bounding the north side of the Sakarya Continent, with S-dipping subduction of Palaeotethys. The Almacık complex was uplifted as a late result of compression against the southern margin of the İstanbul Zone in the Jurassic period. Lack of coeval high-grade metamorphism in the İstanbul Zone indicates that the latter was overthrust southwards over the Sakarya margin, and that there was therefore a change of subduction polarity in the Triassic period. The evidence further casts doubt on the existence of a Mesozoic Intra-Pontide Ocean in northwestern Turkey and suggests that the latest Permian magmatism, with subsequent Triassic and Jurassic metamorphism, was instead related to the closure of the Palaeotethyan Ocean.
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Hamdy Ahmed Mohamed, AWAD, ALI Ibrahim Abu El-Leil, NASTAVKIN Aleksey Valer’evich, et al. "Geological and Tectonic Setting of Andesitic Rock in Central Eastern Desert, Egypt." NEWS of the Ural State Mining University, no. 2 (June 15, 2021): 7–15. http://dx.doi.org/10.21440/2307-2091-2021-2-7-15.
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Objective. The current study aims to detect the geologic features, geochemical characteristics and tectonic setting of the investigated rock using field observations and geochemical analyses. Research methods. This work contains both field work (Collection samples and drawing of a new geological map) and laboratory work (preparation of thin sections for petrographic studies by polarizing microscope), X-ray Fluorescence analysis (XRF) in Institute of Biology, Southern Federal University and Mass-Spectrometer with Inductively Coupled Plasma (ICPMS) at the central Laboratory of Russian Geological Institute. Result. Investigated andesitic rock belongs to Dokhan volcanic that located in the Central Eastern Desert of Egypt a long Qena-Safaga Road. It is considered as one of the most important shear zones in Eastern Desert that includes distinctive rocks and economic mineral deposits. The investigated rock belongs to late to post tectonic magmatism of the East African Orogeny (EAO). Petrographically: Dokhan volcanic is represented by andesite according to petrographical studies. It consists of plagioclase, quartz, in addition to mafic minerals. Geochemically, the investigated andesite samples plotted in calk-alkaline nature. Conclusion. Tectonically, andesite samples fall in arc lava and continental fields. They are enriched in Ba, Sr, Rb, K, Nb and Ce with marked depletion in the most HFSEs like those of island arc calc-alkaline series.
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Kang, Wenbin, Kai Weng, Kai Cao, Xiaojian Zhao, and Yongwei Gao. "Petrogenesis of Carboniferous-Permian Granitoids in the Kumishi Area of Tianshan, China: Insights into the Geodynamic Evolution Triggered by Subduction and Closure of the South Tianshan Ocean." Minerals 14, no. 8 (2024): 811. http://dx.doi.org/10.3390/min14080811.
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Late Carboniferous–Early Permian granitoids are widespread in the Tianshan area and their tectonic setting is controversially discussed. Our research presents fresh whole-rock geochemical and Pb isotopic data, along with zircon U-Pb ages and Hf isotopic data for representative monzonitic and granitic intrusions in the Kumishi area. The aim is to decipher their magma sources and illuminate their geodynamic evolution. Zircon U-Pb dating results reveal that biotite monzonites in the Central Tianshan Belt were emplaced at 312.7 ± 2.9 Ma, while the quartz-monzonites and syenogranites in the South Tianshan Belt were formed at 284.5 ± 2.4 Ma and 283.4 ± 3.9 Ma, respectively. The biotite monzonites generally exhibit metaluminous and high-K calc-alkaline characteristics. They have a positive εHf(t) value (+4.9–+14.1), and are enriched in LREEs and LILEs but depleted in HREEs and HFSEs. These characteristics indicate that they were derived from a mixed magma source of the lower crust and the input of components derived from the mantle wedge above the subduction zone. The quartz-monzonites and syenogranites are high-K calc-alkaline to shoshonitic I-type granites, with εHf(t) values of +14.9–+15.5 and +6.6–+14.9, respectively. They are enriched in LREEs but depleted in HFSEs (e.g., Nb, Ta, and Ti), displaying relatively flat HREE patterns and negative Eu anomalies. The genesis of these rocks is attributed to a partial melting of the lower crust in which mantle-derived magmas participated, which was triggered by an upwelling asthenosphere in a post-collisional extensional geodynamic setting. These granitoids, together with regional analysis of other magmatism in the study area, suggest that the Kumishi area has experienced an evolution from subduction to post-collision from the Late Carboniferous to the Early Permian, which constrains the local closure of the Paleo-Asian Ocean.
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He, Tongtong, Yuxi Wang, Jing Yan, et al. "The Orogeny Transition of the Southern Beishan Orogenic Belt During the Early–Middle Devonian: Evidence from the Wudaomingshui Volcanic Rocks and Granite." Minerals 15, no. 6 (2025): 632. https://doi.org/10.3390/min15060632.
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The Southern Beishan Orogenic Belt (SBOB), an integral part of the Southern Central Asian Orogenic Belt (CAOB), is characterized by extensive Late Paleozoic magmatism. These igneous rocks are the key to studying the tectonic evolution process and the ocean–continent tectonic transformation in the southern margin of the CAOB and Paleo-Asian Ocean. We present zircon U-Pb chronology, in situ Lu-Hf isotopes, and whole-rock geochemistry data for Early–Middle Devonian volcanic rocks in the Sangejing Formation and granites from the Shuangyingshan-Huaniushan (SH) unit in the SBOB. The Wudaomingshiu volcanic rocks (Ca. 411.5 Ma) are calc-alkaline basalt-basaltic andesites with low SiO2 (47.35~55.59 wt.%) and high TiO2 (1.46~4.16 wt.%) contents, and are enriched in LREEs and LILEs (e.g., Rb, Ba, and Th), depleted in HREEs and HFSEs (Nb, Ta, and Ti), and weakly enriched in Zr-Hf. These mafic rocks are derived from the partial melting of the depleted lithosphere metasomatized by subduction fluid and contaminated by the lower crust. Wudaomingshui’s high-K calc-alkaline I-type granite has a crystallization age of 383.6 ± 2.2 Ma (MSWD = 0.11, n = 13), high Na2O (3.46~3.96 wt.%) and MgO (1.25~1.68 wt.%) contents, and a high DI differentiation index (70.69~80.45); it is enriched in LREEs and LILEs (e.g., Rb, Ba, and Th) and depleted in HREEs and HFSEs (e.g., Nb, Ta, and Ti). Granites have variable zircon εHf(t) values (−2.5~3.3) with Mesoproterozoic TDM2 ages (1310~1013 Ma) and originated from lower crustal melting with mantle inputs and minor upper crustal assimilation. An integrated analysis of magmatic suites in the SBOB, including rock assemblages, geochemical signatures, and zircon εHf(t) values (−2.5 to +3.3), revealed a tectonic transition from advancing to retreating subduction during the Early–Middle Devonian.
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Johnson, Susan C., Leslie R. Fyffe, Malcolm J. McLeod, and Gregory R. Dunning. "U–Pb ages, geochemistry, and tectonomagmatic history of the Cambro-Ordovician Annidale Group: a remnant of the Penobscot arc system in southern New Brunswick?1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology." Canadian Journal of Earth Sciences 49, no. 1 (2012): 166–88. http://dx.doi.org/10.1139/e11-031.
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The Penobscot arc system of the northeastern Appalachians is an Early Cambrian to early Tremadocian (ca. 514–485 Ma) ensialic to ensimatic arc–back-arc complex that developed along the margin of the peri-Gondwanan microcontinent Ganderia. Remnants of this Paleozoic arc system are best preserved in the Exploits Subzone of central Newfoundland. Correlative rocks in southern New Brunswick are thought to occur in the ca. 514 Ma Mosquito Lake Road Formation of the Ellsworth Group and ca. 497–493 Ma Annidale Group; however in the past, the work that has been conducted on the latter has been of a preliminary nature. New data bearing on the age and tectonic setting of the Annidale Group provides more conclusive evidence for this correlation. The Annidale Group contains subalkaline, tholeiitic to transitional, basalts to basaltic andesites, picritic tuffs and calc-alkaline to tholeiitic felsic dome complexes that have geochemical signatures consistent with suprasubduction zone magmatism that was likely generated in a back-arc basin. New U–Pb ages establish that the Late Cambrian to Early Tremadocian Annidale Group and adjacent ca. 541 Ma volcanic rocks of the Belleisle Bay Group in the New River belt were affected by a period of younger magmatism ranging in age from ca. 479–467 Ma. This provides important constraints on the timing of tectonism in the area. A ca. 479 Ma age for the Stewarton Gabbro that stitches the faulted contact between the Annidale and Belleisle Bay groups, demonstrates that structural interleaving and juxtaposition occurred during early Tremadocian time, which closely coincides with the timing of obduction of Penobscottian back-arc ophiolites onto the Ganderian margin in Newfoundland.
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Kilias, Ad, A. Vamvaka, G. Falalakis, et al. "The Mesohellenic trough and the Thrace Basin. Two Tertiary molassic Basins in Hellenides: do they really correlate?" Bulletin of the Geological Society of Greece 47, no. 2 (2017): 551. http://dx.doi.org/10.12681/bgsg.11082.
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Based on lithostratigraphic and structural data, as well as geological mapping, the mollasic Thrace Basin (ThB) in NE Greece (including the Paleogene deposits of the Axios Basin) was compared with the Mesohellenic Trough (MHT) in NW Greece. Both basins are characterized by a thick sedimentary sequence of molassic-type strata (3-5km thickness) of Tertiary age, overlain unconformably by Miocene- Pliocene and Quaternary deposits. Molassic sedimentation started almost simultaneously in both areas during the Mid-Upper Eocene but it finished in different time, in the Mid-Upper Miocene for the MHT and the Upper Oligocene for the ThB, respectively. Sedimentation in ThB was also linked with an important calc-alkaline and locally shoshonitic magmatism of Eocene-Oligocene age. We interpreted the MHT as a polyhistory strike-slip and piggy-back basin, above westward-emplacing ophiolites and Pelagonian units on the cold Hellenic accretionary prism. In contrast to MHT, the ThB evolved as a Paleogene supra-detachment basin above the strongly extended during the Eocene-Oligocene Hellenic Hinterland. The syn-depositional magmatic products, linked possibly with subduction processes in Pindos or Axios ocean(s). In any case, MHT and ThB are related to inferred oblique convergence of the Apulia plate and the internal Hellenic units.
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Teng, Chao, Meiling Dong, Xinjie Yang, et al. "Zircon U-Pb Geochronology and Geochemical Constraints of Tiancang Granites, Southern Beishan Orogenic Belt: Implications for Early Permian Magmatism and Tectonic Evolution." Minerals 15, no. 4 (2025): 426. https://doi.org/10.3390/min15040426.
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The Beishan Orogenic Belt, situated along the southern margin of the Central Asian Orogenic Belt, represents a critical tectonic domain that archives the prolonged subduction–accretion processes and Paleo-Asian Ocean closure from the Early Paleozoic to the Mesozoic. Early Permian magmatism, exhibiting the most extensive spatial-temporal distribution in this belt, remains controversial in its geodynamic context: whether it formed in a persistent subduction regime or was associated with mantle plume activity or post-collisional extension within a rift setting. This study presents an integrated analysis of petrology, zircon U-Pb geochronology, in situ Hf isotopes, and whole-rock geochemistry of Early Permian granites from the Tiancang area in the southern Beishan Orogenic Belt, complemented by regional comparative studies. Tiancang granites comprise biotite monzogranite, monzogranite, and syenogranite. Zircon U-Pb dating of four samples yields crystallization ages of 279.3–274.1 Ma. These granites are classified as high-K calc-alkaline to calc-alkaline, metaluminous to weakly peraluminous I-type granites. Geochemical signatures reveal the following: (1) low total rare earth element (REE) concentrations with light REE enrichment ((La/Yb)N = 3.26–11.39); (2) pronounced negative Eu anomalies (Eu/Eu* = 0.47–0.71) and subordinate Ce anomalies; (3) enrichment in large-ion lithophile elements (LILEs: Rb, Th, U, K) coupled with depletion in high-field-strength elements (HFSEs: Nb, Ta, P, Zr, Ti); (4) zircon εHf(t) values ranging from −10.5 to −0.1, corresponding to Hf crustal model ages (TDMC) of 1.96–1.30 Ga. These features collectively indicate that the Tiancang granites originated predominantly from partial melting of Paleoproterozoic–Mesoproterozoic crustal sources with variable mantle contributions, followed by extensive fractional crystallization. Regional correlations demonstrate near-synchronous magmatic activity across the southern/northern Beishan and eastern Tianshan Orogenic belts. The widespread Permian granitoids, combined with post-collisional magmatic suites and rift-related stratigraphic sequences, provide compelling evidence for a continental rift setting in the southern Beishan during the Early Permian. This tectonic regime transition likely began with lithospheric delamination after the Late Carboniferous–Early Permian collisional orogeny, which triggered asthenospheric upwelling and crustal thinning. These processes ultimately led to the terminal closure of the Paleo-Asian Ocean’s southern branch, followed by intracontinental evolution.
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Macdonald, Ray, and Douglas J. Fettes. "The tectonomagmatic evolution of Scotland." Transactions of the Royal Society of Edinburgh: Earth Sciences 97, no. 3 (2006): 213–95. http://dx.doi.org/10.1017/s0263593300001450.
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ABSTRACTScotland has a magmatic record covering much of the period 3100–50 Ma. In this review, we pull together information on Scotland's igneous rocks into a continuous story, showing how magmatic activity has contributed to the country's structural development and assessing whether the effects of older magmatic events can be recognised in later episodes.The oldest igneous rocks are part of supracrustal sequences within the Lewisian Gneiss Complex, formed when Scotland was part of the supercontinent Kenorland. The supracrustal rocks were intruded between 3100 and 2800 Ma by granodiorites and tonalites, which were metamorphosed and deformed in a major tectonothermal event between 2700 and 2500 Ma. The break-up of Kenorland (2400–2200 Ma) was marked by the intrusion of mafic dyke swarms of tholeiitic affinity. The convergence of continental masses to form the supercontinent Columbia resulted, at ∼1900 Ma, in a series of subduction-related volcanic rocks and gabbro–anorthosite masses. Subsequent continent–continent collision formed a series of granite–pegmatite sheets at ∼1855 Ma and ∼1675 Ma and reworked much of the earlier rocks in the amphibolite facies. Columbia was breaking up by 1200 Ma, an event marked by remnants of basaltic magmatism in the NW of the country. Re-assembly of the continental fragments to form the supercontinent Rodinia resulted in the Grenville Orogeny, which in Scotland was marked by basement reworking but no confirmed magmatic activity. Early attempts to split Rodinia produced a rift-related, bimodal, mafic–felsic sequence in the Moine Supergroup of the Northern Highlands, at least some of the mafic rocks having mid-ocean ridge basalt affinities. Crustal thickening during a disputed orogenic event, the Knoydartian, may have caused regional migmatisation. The final break-up of Rodinia occurred in Scotland at ∼600 Ma, when very extensive tholeiitic magmatism characterised the later parts of the Dalradian Supergroup, while a series of granites intruded the Moine and Dalradian successions.Ordovician and Silurian times saw the closure of the Iapetus Ocean and the convergence of Laurentia, Avalonia and Baltica. The collision of a major arc system with Laurentia caused the Grampian event (480–465 Ma) of the Caledonian Orogeny, marked by ophiolite obduction, the generation of (largely) anatectic granites, volcanism in the Midland Valley and Southern Uplands, and intrusion of a major gabbro–granite suite in the NE. The late-Caledonian events (435–420 Ma) were largely post-collisional and were marked by the emplacement of alkaline igneous intrusions in the NW, calc-alkaline granitic intrusions over much of the country, widespread volcanic activity and regional dyke swarms. Laurentia, Avalonia and Baltica amalgamated to form the supercontinent Laurussia. Magmatic activity recommenced at 350 Ma, when intra-plate alkaline magmatism affected much of southern Scotland, in particular, through into Permian times. The alkaline magmatism was interrupted at ∼295 Ma by a short-lived event in which tholeiitic magmas were intruded as sills and dykes in a swarm ∼200 km wide. In the early Palaeogene, lithospheric attenuation related to proto-North Atlantic formation and the splitting of Pangaea was complemented by the arrival of the Iceland mantle plume. Huge volumes of mafic magma were emplaced as lava fields, central complexes and regional swarms, locally increasing crustal thickness by 30%
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El-Desoky, Hatem M., Andongma W. Tende, Ahmed M. Abdel-Rahman, et al. "Hydrothermal Alteration Mapping Using Landsat 8 and ASTER Data and Geochemical Characteristics of Precambrian Rocks in the Egyptian Shield: A Case Study from Abu Ghalaga, Southeastern Desert, Egypt." Remote Sensing 14, no. 14 (2022): 3456. http://dx.doi.org/10.3390/rs14143456.
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This study evaluates the geological attributes of rocks within the Abu Ghalaga area using spatial, geochemical, and petrographic approaches. ASTER and Landsat imagery processed using band ratio and principal component analysis were used to map hydrothermal alterations, while a regional tectonic evaluation was based on automated extraction of lineaments from a digital elevation model. Geochemical and petrographic analyses were then employed for discrete scale evaluation of alteration patterns of rocks across the study location. Based on satellite image processing, alteration patterns across the study area are widespread, while evidence from lineament analysis suggests a dominant NW–SE tectonic trend accompanied by a less dominant ENE–WSW direction. The different rock units exposed in the studied district are arranged chronologically from oldest to youngest as arc metavolcanic group (basalt and rhyolite), arc metagabbro–diorite, gneissose granite (granodiorite and tonalite), and dykes (aplite and felsite). Various types of igneous and metamorphic rocks have propylitic, phyllic, and argillic zones. Geochemical data indicate that the studied rocks are classified into granite, granodiorite, gabbroic diorite, and gabbro. Geochemically, the rocks have a sub-alkaline magma type. The granodiorite–tonalite is derived from the calc–alkaline magma nature, while gabbro and diorite samples exhibit tholeiitic to calc–alkaline affinity. The tectonic setting of the studied rocks trends toward volcanic arc granite (VAG). Based on petrographic, geochemical, and remote analyses, sericitization, chloritization, epidotization, kaolinitization, carbonatization, and silicification are the main alteration types present in the study area. As a result of lineaments analysis, the existing fractures and structural planes form valid flow paths for mineral-bearing hydrothermal solutions.
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Martínez, Amancay, Adrian Gallardo, Melisa Mulé, Aldo Giaccardi, Esteban Crespo, and David Aguilera. "New insights into the Permian-Triassic magmatism of southern Cerro Cacheuta, Argentina." Earth Sciences Research Journal 27, no. 4 (2024): 343–54. http://dx.doi.org/10.15446/esrj.v27n4.107538.
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The igneous rocks of Cerro Cacheuta are considered a typical expression of the Permian-Triassic magmatism within the Andes Precordillera of Mendoza, Argentina. In particular, the southwestern margin of this hilltop is characterised by intermediate volcanic and felsic intrusives from the Choiyoi Group, one of the most extensive volcano-sedimentary suites of southern South America. The Choiyoi magmatism is widely associated with dramatic tectonic and environmental changes in the Gondwana supercontinent. Therefore, a better characterisation of the igneous facies of Cerro Cacheuta is critical to understand the evolution of Gondwana and recognise the multiple events that occurred towards the end of the Permian. This paper presents new data about the mineralogy, petrography, and geochemistry of the plutonic and volcanic units of Cerro Cacheuta, which enables authors to draw additional conclusions about the genesis and evolution of the magmatism in the region. Microscope observations indicate that the volcanic rocks are largely consistent with intermediate facies dominated by a porphyry texture with plagioclase and sanidine phenocrystals within a trachytic groundmass. Coetaneous breccias of possible hydrothermal origin and geodes with cryptocrystalline silica, limonite, and quartz are also recognised in outcrops. Geochemical analysis suggests that the lavas would likely correspond to andesites from a calc-alkaline magmatic arc. Furthermore, trace elements show enrichment in LREE/HREE, a slight negative anomaly in Eu, and concentration ratios compatible with crustal extension during the initial stages of the Choiyoi Group. Based on their chemical similarities, the monzonites of the Boca del Río Pluton would correlate with the lower section of the Choiyoi Group, of Permian age. In contrast, granites of the Cacheuta Pluton show a signature typically recognised in units from the Triassic and, therefore, would be comparable to the upper member of the Choiyoi Group.
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Nogueira, Bruna Karine Correa, Paulo Sergio de Sousa Gorayeb, Elton Luiz Dantas, Rafael Estumano Leal, and Marco Antonio Galarza. "Rhyacian evolution of the eastern São Luís Craton: petrography, geochemistry and geochronology of the Rosário Suite." Brazilian Journal of Geology 47, no. 2 (2017): 275–99. http://dx.doi.org/10.1590/2317-4889201720160114.
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ABSTRACT: The São Luís Cráton comprises an area between northeast Pará state and northwest Maranhão that exposes Paleoproterozoic granitic suites and meta-volcanosedimentary sequences. In the east of this geotectonic unit, about 70 km south of São Luís, there is a portion of the São Luís Craton, represented by the intrusive Rosario Suite (RS). This work is focused on rocks of this suite, including petrographic, lithochemical and geochronological studies to understand the crustal evolution of these granitoid rocks. The rock spectrum varies from tonalitic to granodioritic, quartz dioritic and granitic compositions, and there are partial structural and mineralogical changes related to deformation along transcurrent shear zones. The geochemical studies show granitic metaluminous compositions of the calc-alkaline series with I-type affinity typical of magmatic arc. Rare earth elements show marked fractionation and slight Eu positive or negative anomalies (Eu/Eu* = 0.82 to 1.1). Zircon U-Pb data provided consistent ages of 2165 ± 7 Ma, 2170 ± 7 Ma, 2170 ± 7 Ma, 2161 ± 4 Ma and 2175 ± 8 Ma, dating emplacement of these granitoids as Paleoproterozoic (Rhyacian). Sm-Nd isotopic data provided model ages (TDM) of 2.21 to 2.31 Ga with positive values of εNd +1.9 to +3.2 (t = 2.17 Ga), indicating predominantly Rhyacian crustal sources for the parental magmas, similar to those ones found in other areas of the São Luís Craton. The data, integrated with published geological and geochronological information, indicate the occurrence of an important continental crust formation event in this area. The Paleoproterozoic evolution between 2.17 and 2.15 Ga is related to the Transamazonian orogeny. The granitoids of the Rosario Suite represent the main phase of continental arc magmatism that has continuity in other parts of the São Luís Craton and can be correlated with Rhyacian accretionary magmatism in the northwestern portion of the Amazonian Craton that amalgamated Archean terrains during the Transamazonian orogeny.
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Petterson, M. G. "The plutonic crust of Kohistan and volcanic crust of Kohistan–Ladakh, north Pakistan/India: lessons learned for deep and shallow arc processes." Geological Society, London, Special Publications 483, no. 1 (2018): 123–64. http://dx.doi.org/10.1144/sp483.4.
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AbstractThe Kohistan–Ladakh terrane, northern Pakistan/India, offers a unique insight into whole-arc processes. This research review presents summaries of fundamental crustal genesis and evolution models. Earlier work focused on arc sequence definition. Later work focused on holistic petrogenesis. A new model emerges of an unusually thick (c. 55 km) arc with a c. 30 km-thick batholith. Volatile-rich, hornblende ± garnet ± sediment assimilation-controlled magmatism is predominant. The thick batholith has a complementary mafic–ultramafic residue. Kohistan crustal SiO2 contents are estimated at >56%. The new-Kohistan, silicic-crust model contrasts with previous lower SiO2 estimates (c. 51% SiO2 crust) and modern arcs that imply <35 km crustal thicknesses and arc batholith thicknesses of c. 7 km. A synthetic overview of Kohistan–Ladakh volcanic rocks presents a model of an older, cleaved/deformed Cretaceous volcanic system at least 800 km across strike. The Jaglot–Chalt–Dras–Shyok volcanics exhibit predominant tholeiitic-calc-alkaline signatures, with a range of arc-related facies/tectonic settings. A younger, post-collisional, Tertiary silicic volcanic system (the Shamran–Dir–Dras-2–Khardung volcanics) lie unconformably upon Cretaceous basement, and erupted within an intra-continental tectonic setting. Kohistan–Ladakh tectonic model controversies remain. In essence, isotope-focused researchers prefer later (Tertiary) collisions, whilst structural field-geology-orientated researchers prefer an older (Cretaceous) age for the Northern/Shyok Suture.
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Kamali, Amin Allah, Mohsen Moayyed, Nasir Amel, et al. "Mineralogy, mineral chemistry and thermobarometry of post-mineralization dykes of the Sungun Cu–Mo porphyry deposit (Northwest Iran)." Open Geosciences 12, no. 1 (2020): 764–90. http://dx.doi.org/10.1515/geo-2020-0009.
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AbstractThe Sungun copper–molybdenum porphyry deposit is located in the north of Varzaghan, northwestern Iran. The Sungun quartz-monzonite is the oldest mineralized intrusive body in the region and was emplaced during the Early Miocene. Eight categories of the late and unmineralized dykes, which include quartz diorite, gabbrodiorite, diorite, dacite, microdiorite and lamprophyre (LAM), intrude the ore deposit. The main mineral phases in the dykes include plagioclase, amphibole and biotite, with minor quartz and apatite and secondary chlorite, epidote, muscovite and sericite. The composition of plagioclase in the quartz diorite dykes (DK1a, DK1b and DK1c) varies from albite-oligoclase to andesine and oligoclase to andesine; in the diorite, it varies from andesine to labradorite; in the LAM, from albite to oligoclase; and in the microdiorite (MDI), it occurs as albite. Amphibole compositions are consistent with classification as hornblende or calcic amphibole. Based on their AlIV value (less than 1.5), amphibole compositions are consistent with an active continental margin affinity. The average percentage of pistacite (Ps) in epidotes formed from alteration of plagioclase and ferromagnesian minerals is 27–23% and 25–30%, respectively. Thermobarometric studies based on amphibole and biotite indicate approximate dyke crystallization temperature of 850–750℃, pressure of 231–336 MPa and high fO2 (>nickel-nickel-oxide buffer). The range of mineral compositions in the postmineralization dyke suite is consistent with a genetic relationship with the subduction of the Neotethys oceanic crust beneath the continental crust of the northwest part of the Central Iranian Structural Zone. Despite the change from calc-alkaline to alkaline magmatism, the dykes are likely related to the late stages of magmatic activity in the subduction system that also generated the porphyry deposit.
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Derbeko, I. M. "Late Mesozoic Adakite Granites in the Northern Framing of the Eastern Flank of the Mongol–Okhotsk Orogenic Belt." Геохимия 68, no. 1 (2023): 69–82. http://dx.doi.org/10.31857/s0016752523010028.
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The examination of original and available petrochemical, geochemical, and isotope (Sm-Nd, Rb-Sr) data showed that subalkaline granitoids in the northern framing of the eastern flank of the Mongol–Okhotsk orogenic belt belong to the adakite series. The granitoids are characterized by high Sr/Y, Sr, Al2O3, and LREE, extremely low HREE concentrations, and the absence of negative Eu anomalies. The results obtained and the analysis of the geodynamic setting of their formation made it possible to assume that the granitoids were formed at a depth of more than 45 km through melting of garnet-bearing (20–50% garnet) rocks, which are likely represented by lower crustal Precambrian complexes widespread in the southern framing of the Siberian craton. The source of parental melts involved both mantle and crustal matter. This likely occurred in a subduction setting through melting of frontal or lateral parts of oceanic slab in subduction “windows”. The Late Jurassic–Early Cretaceous Chubachin adakite complex (149–138 Ma) was distinguished. Its formation preceded the initiation of suprasubduction differentiated calc-alkaline magmatism (140–122 Ma) in the northern framing of the eastern flank of the Mongol–Okhotsk orogenic belt.
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Martinez, Amancay, Adrian Gallardo, Laura Giambiagi, and Laura Tobares. "The Choiyoi Group in the Cordón del Plata range, western Argentina: structure, petrography and geochemistry." Earth Sciences Research Journal 24, no. 2 (2020): 121–32. http://dx.doi.org/10.15446/esrj.v24n2.79515.
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The Choiyoi Group from the Permo-Triassic, is one of the most conspicuous volcano-sedimentary suites of southern South America, considered critical to understand the geological evolution of the western margins of Gondwana. In this regard, petrography, geochemistry, and structural data were examined to better elucidate the physical character and emplacement conditions of the unit in the Cordon del Plata range, within the Frontal Cordillera of Mendoza, Argentina. The site is representative of the magmatism and deformation through different Andean cycles. Results of the study indicate three lithological facies of increasing acidity upwards. Mafic units consist of basalts, andesite and andesitic breccias at the base of the sequence. Felsic rocks such as rhyodacites, granites and welded tuffs are predominant above. The fault zone of La Polcura – La Manga is the most prominent structural feature in the region, which presumably controlled the emplacement of breccias and ignimbrites within the middle and upper members. These compositional variations suggest a magma evolution from subduction to a rifting environment after the San Rafael orogeny in the Late Palaeozoic. In this line, the Lower Choiyoi was observed to overlie the San Rafael structures indicating thus, that compression ceased before the volcanic extrusion. Geochemistry data indicate that mafic rocks are mostly high-potassium, calc-alkaline volcanics derived from the mantle wedge above the subduction zone. In contrast, the felsic rocks range from high-potassium rhyolites to shoshonites, typically depleted in Eu. This indicate partial melting of a lithospheric mantle in an average to thin crust.
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Bergman, Stefan, and Pär Weihed. "Chapter 3 Archean (>2.6 Ga) and Paleoproterozoic (2.5–1.8 Ga), pre- and syn-orogenic magmatism, sedimentation and mineralization in the Norrbotten and Överkalix lithotectonic units, Svecokarelian orogen." Geological Society, London, Memoirs 50, no. 1 (2020): 27–81. http://dx.doi.org/10.1144/m50-2016-29.
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AbstractTwo lithotectonic units (the Norrbotten and Överkalix units) occur inside the Paleoproterozoic (2.0–1.8 Ga) Svecokarelian orogen in northernmost Sweden. Archean (2.8–2.6 Ga and possibly older) basement, affected by a relict Neoarchean tectonometamorphic event, and early Paleoproterozoic (2.5–2.0 Ga) cover rocks constitute the pre-orogenic components in the orogen that are unique in Sweden. Siliciclastic sedimentary rocks, predominantly felsic volcanic rocks, and both spatially and temporally linked intrusive rock suites, deposited and emplaced at 1.9–1.8 Ga, form the syn-orogenic component. These magmatic suites evolved from magnesian and calc-alkaline to alkali–calcic compositions to ferroan and alkali–calcic varieties in a subduction-related tectonic setting. Apatite–Fe oxide, including the world's two largest underground Fe ore mines (Kiruna and Malmberget), skarn-related Fe oxide, base metal sulphide, and epigenetic Cu–Au and Au deposits occur in the Norrbotten lithotectonic unit. Low- to medium-pressure and variable temperature metamorphic conditions and polyphase Svecokarelian ductile deformation prevailed. The general northwesterly or north-northeasterly structural grain is controlled by ductile shear zones. The Paleotectonic evolution after the Neoarchean involved three stages: (1) intracratonic rifting prior to 2.0 Ga; (2) tectonic juxtaposition of the lithotectonic units during crustal shortening prior to 1.89 Ga; and (3) accretionary tectonic evolution along an active continental margin at 1.9–1.8 Ga.
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Mills, Andrea, and Hamish Sandeman. "Lithostratigraphy and lithogeochemistry of Ediacaran alkaline basaltic rocks of the Musgravetown Group, Bonavista Peninsula, northeastern Newfoundland, Canada: an extensional volcanogenic basin in the type-Avalon terrane." Atlantic Geology 57 (August 5, 2021): 207–34. http://dx.doi.org/10.4138/atlgeol.2021.010.
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Volcanic rocks of the Ediacaran Musgravetown Group on Bonavista Peninsula, Avalon terrane, Newfoundland, include basal ca. 600 Ma calc-alkaline basalt succeeded by continental tholeiite and alkaline rhyolite of the ca. 592 Ma Plate Cove volcanic belt (Bull Arm Formation), indicating a change from subduction-related to extensionrelated tectonic regimes during that interval. Alkalic basalts on northeastern (Dam Pond area) and southwestern (British Harbour area) Bonavista Peninsula occur below and above, respectively, the ca. 580 Ma glacial Trinity facies. Dam Pond basalt occurs in a structural dome intercalated with and flanked by fine-grained, siliciclastic deposits (Big Head Formation) overlain by Trinity facies. The British Harbour basalt occurs above the Trinity facies, in an upward- coarsening sandstone sequence (Rocky Harbour Formation) overlain by red beds of the Crown Hill Formation (uppermost Musgravetown Group). The Rocky Harbour and Big Head formations are likely stratigraphically interfingered proximal and distal deposits, respectively, derived from erosion of the Bull Arm Formation and older Avalonian assemblages.The Big Head basalts have lower SiO2, Zr, FeOT, P2O5, TiO2 and higher Mg#, Cr, V, Co and Ni contents, and are therefore more primitive than the more FeOT-, TiO2-, and P2O5-rich British Harbour basalts. Large-ionlithophile and rare-earth-element concentrations and ratios indicate that both suites originated from low degree partial melts of deep, weakly garnet-bearing, undepleted asthenospheric peridotite sources, with magma conduits likely focused along regional extensional faults. The protracted and episodic extension-related volcanic activity is consistent with a geodynamic setting that evolved from a mature arc into extensional basins with slowly waning magmatism, possibly involving slab rollback and delamination followed by magmatic underplating. The duration and variation of both volcanism and sedimentation indicate that the Musgravetown Group should be elevated to a Supergroup in order to facilitate future correlation of its constituent parts with other Avalonian basins.
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Ge, Mao-Hui, Jin-Jiang Zhang, Long Li, and Kai Liu. "Ages and geochemistry of Early Jurassic granitoids in the Lesser Xing’an–Zhangguangcai Ranges, NE China: Petrogenesis and tectonic implications." Lithosphere 11, no. 6 (2019): 804–20. http://dx.doi.org/10.1130/l1099.1.
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Abstract Early Jurassic granitoids are widespread in the Lesser Xing’an–Zhangguangcai Ranges, providing excellent targets to understand the late Paleozoic to early Mesozoic tectonic framework and evolution of Northeast China, especially the Jiamusi block and its related structural belts. In this paper, we present new geochronological, geochemical, and isotopic data from the granitoids in the Lesser Xing’an–Zhangguangcai Ranges to constrain the early Mesozoic tectonic evolution of the Mudanjiang Ocean between the Jiamusi and Songnen blocks. Our results show that the granitic intrusions in the Lesser Xing’an–Zhangguangcai Ranges are mainly composed of syenogranite, monzogranite, granodiorite, and tonalite, which have crystallization ages from 196 to 181 Ma. Their geochemical features indicate that these Jurassic intrusions are all high-K calc-alkaline I-type granites with metaluminous to weakly peraluminous compositions. These granitoids are characterized by enrichments in large ion lithophile elements (e.g., Ba, Th, U) and light rare earth elements and depletions in high field strength elements (e.g., Nb and Ta) and heavy rare earth elements, which are typical for continental arc–type granites. The sources of these granitoids were likely derived from juvenile Mesoproterozoic to Neoproterozoic crustal materials (e.g., metabasaltic rocks). Integrated with data from regional coeval magmatism, metamorphism, metallogeny, and structure, our new data suggest that the granitoids in the Lesser Xing’an–Zhangguangcai Ranges were probably formed in an active continental margin setting, which fits well in our previous model of Early Jurassic westward subduction of the Mudanjiang Ocean between the Jiamusi and Songnen blocks.
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Chen, Jingsheng, Dexin Tian, Bin Li, et al. "Permian Granitic Plutons from the Northern Margin of the North China Craton: Implications for the Tectonic Evolution of the Central Asian Orogenic Belt." Minerals 13, no. 12 (2023): 1554. http://dx.doi.org/10.3390/min13121554.
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As the world’s largest accretionary orogen, the Central Asian Orogenic Belt (CAOB) underwent continuous juvenile crustal growth in the Phanerozoic. The northern margin of the North China Craton (NCC) and its adjacent area form the eastern segment of the CAOB, which is a key area for learning about the geological evolution of the Paleo-Asian Ocean (PAO). In the Permian, the west of the northern margin of the NCC was a post-collision extensional environment, while the east was in a subduction stage. As a connecting area, the Permian evolution of the PAO in the middle of the northern margin of the NCC has not been systematically studied. In order to fill the gap and understand the continuous temporal and spatial evolutionary process of the PAO, this paper focuses on the Permian granitic rocks in the Chifeng area. Zircon U-Pb dating and the geochemical analysis of whole-rock major and trace elements were conducted to build a granite chronological framework, and to discuss the genesis and tectonic background of the granitic rocks, along with tectono-magmatic evolutionary history in the Chifeng area. The respective LA-ICP-MS zircon U-Pb dating results from eight samples are 269 ± 1, 268 ± 3, 260 ± 4, 260 ± 1, 260 ± 1, 255 ± 2, 254 ± 2 and 256 ± 1 Ma, respectively. These results, combined with previous data, revealed that the Permian granitic rocks had undergone three events of magmatism: (1) monzogranitic-syenitic phase (294–284 Ma; Cisuralian); (2) monzogranitic phase (269–260 Ma; Guadalupian) and (3) late monzogranitic-syenitic phase (256–254 Ma; Lopingian). From the Early Permian (294–284 Ma) to the Middle Permian (269–260 Ma), granites with fine-medium-grained locally porphyritic texture and massive structure showed a high-potassium calc-alkaline series formed in a compressional setting, indicating a continuous collision between the Xing’an-Mongolian Orogenic Belt (XMOB) and the NCC. During the Late Permian-Early Triassic (256–248 Ma), granites with massive structure and medium-grained texture in the Chifeng area were magmatism dominated by A- and I-type granites of high-potassium calc-alkaline series, combined with the coeval basic rocks, which constituted a typical “bimodal” rock assemblage. This suggests that the Chifeng area was located in an extensional setting where the subducting slab broke off during the collision between the XMOB and NCC. These granitic plutons from the Permian are believed to have been generated by the subduction-collision of the Paleo-Asian oceanic crust beneath the NCC, according to emplacement time and occurrence location. Our findings provide strong evidence for Permian continuous temporal and spatial tectonic evolution and the characterization of the eventual closure of the PAO in Chifeng area at the northern margin of the NCC.