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Khairul Amri Kamarudin, Mohd, Musa Garba Abdullahi, Mohd Hariri Arifin, Roslan Umar, Muhammad Hafiz Md Saad, and Iya Garba. "Investigation of Road Bank Failures based on Mineralogical Composition Studies in Kano-Abuja Road Northern, Nigeria." International Journal of Engineering & Technology 7, no. 4.34 (December 13, 2018): 167. http://dx.doi.org/10.14419/ijet.v7i4.34.23852.
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This article investigated the general compositions of the areas (the road) including the geology, mineralogy, and geochemistry to explore the reason for the road failure. The zone is underlain basement (storm cellar) and sedimentary rocks of different textures, mineralogy, and geochemistry. The results implies that the areas that is most stable along the road portions is underlain by the granite-gneiss, granites, amphibole schist and quartz, schist and small sandstone while portions with the failures are underlain by mica schist, phyllite, and coarse-grained granite. It is apparently sure from this study that poor quality metasedimentary rocks constitute the formation of the failed portions. However, the high numbers of the sediment and sandstone present in the area that can easily be weathered due to the climate variation have increased the failure. In conclusion, the result will help the engineers during reconstruction of these parts need to be excavating deeply and replace with granite-gneiss, granites, amphibole schist and quartz for better result.
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STEPANYUK, L. M., S. I. KURYLO, O. V. KOVTUN, T. I. DOVBUSH, and O. B. VYSOTSKY. "Uranium-Lead Geochronology of Two-Feldspar Granites of the Inhul Megablock (Ukrainian Shield) by Monazite." Mineralogical journal 43, no. 2 (2021): 49–57. http://dx.doi.org/10.15407/mineraljournal.43.02.049.
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In the area of the Novooleksandrivka village, the valley of the Bokovenka river crosses a powerful strip of metamorphic rocks of the Inhulo-Inhulets series with numerous small granitoid bodies of the Kirovohrad complex. In the right bank of the river valley north of Novooleksandrivka there are almost continuous rock outcrops of porphyry-like, mostly coarse-grained garnet-biotite granites, which are cut by veins of aplite-pegmatoid and pegmatoid granites. Uranium-lead isotope systems of accessory monazites from porphyry-like granite, layered body of uneven-grained granite and from veined body of aplite-pegmatoid granite have been studied. The age of the first two, more coarse-grained granite varieties, is 2043.2 ± 2.6 and 2041 ± 2.3 million years, respectively. Significantly younger are the monocytes from the vein of aplite-pegmatoid granite - 2030 ± 0.3 million years. In granites in this sequence, in addition to structural and textural characteristics (in general, decrease in grain size), there is a decrease in the amount of SiO2 (from 73.14 to 70.93%) connected with a significant increase in K2O (from 3.96 to 7.58%), (their inverse correlation coefficient is 0.98), a significant decrease in the CaO content from 2.04 to 0.97%, and a slight decrease in the MgO content from 1.14% to 0.82%. These changes are probably caused by the crystallizational differentiation of the original granite melt.
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Houle, Gilles, and Donald L. Phillips. "The Soil Seed Bank of Granite Outcrop Plant Communities." Oikos 52, no. 1 (March 1988): 87. http://dx.doi.org/10.2307/3565986.
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Wang, Li Chao, and Ping Gen Zhou. "The Stability Analysis on Reservoir Bank Slope of Granite Stained Subgrade." Advanced Materials Research 250-253 (May 2011): 1711–16. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.1711.
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The limit equilibrium method for rigid body is used to analyze the stability of subgrade reservoir bank slope of granite stained. The sliding of subgrade reservoir bank slope reinforced by dynamic compaction along the interface will not be happened. In the most unfavorable conditions , the sliding surface will be formed inside the stained subgrade, which threatened to the safety operation of the expressway.
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Usman, Ediar. "THE GEOCHEMICAL CHARACTERISTIC OF MAJOR ELEMENT OF GRANITOID OF NATUNA, SINGKEP, BANGKA AND SIBOLGA." BULLETIN OF THE MARINE GEOLOGY 30, no. 1 (February 15, 2016): 45. http://dx.doi.org/10.32693/bomg.30.1.2015.74.
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A study of geochemical characteristic of major elelemnt of granitoid in Western Indonesia Region was carried out at Natuna, Bangka, Singkep and Sibolga. The SiO2 contents of the granites are 71.16 to 73.02 wt%, 71.77 to 75.56wt% and 71.16 to 73.02wt% at Natuna, Bangka, and Singkep respectively, which are classified as acid magma. While in Sibolga the SiO2 content from 60.27 to 71.44wt%, which is classified as intermediate to acid magma. Based on Harker Diagram, the granites from Natuna, Bangka and Singkep as a co-genetic. In other hand the Sibolga Granite show as a scatter pattern. Granites of Natuna, Bangka and Singkep have the alkaline-total (Na2O + K2O) between 6.03 to 8.51 wt% which are classified as granite and alkali granite regime. K2O content ranges from 3.49 to 5.34 wt% and can be classified as calc-alkaline type. The content of alkaline-total of Sibolga granite between 8.12 to 11.81 wt% and classified as a regime of syenite and granite. The range of K2O is about 5.36 to 6.94wt%, and assumed derived from high-K magma to ultra-potassic types. Granites of Natuna, Bangka and Singkep derived from the plutonic rock types and calc-alkaline magma, while Sibolga granite magma derived from K-high to ultra-potassic as a granite of islands arc. Based on the chemical composition of granite in Western Indonesian Region can be divided into two groups, namely Sibolga granite group is representing the Sumatera Island influenced by tectonic arc system of Sumatera Island. Granites of Bangka and Singkep are representing a granite belt in Western Indonesian Region waters which is influenced by tectonic of back arc.Keywords: magma, geochemical characteristic, major element and Western Indonesian Region Kajian karakteristik geokimia dari unsur utama granitoid di Kawasan Barat Indonesia telah dilakukan di daerah Natuna, Bangka, Singkep dan Sibolga. Kandungan SiO2 granit Natuna antara 71,16 - 73,02%, Bangka antara 71,77 - 75,56%, Singkep antara 72,68 - 76,81% termasuk dalam magma asam. Granit Sibolga memiliki kandungan SiO2 antara 60,27 - 71,44% termasuk dalam magma menengah - asam. Berdasarkan Diagram Harker, granit Natuna, Bangka dan Singkep mempunyai asal kejadian yang sama (ko-genetik), sedangkan granit Sibolga membentuk pola pencar. Granit Natuna, Bangka dan Singkep mengandung total alkalin (K2O+Na2O) antara 6,03 - 8,51% termasuk dalam jenis rejim granit dan alkali granit. Berdasarkan kandungan K2O antara 3,49 - 5,34 %berat, bersifat kalk-alkali. Granit Sibolga mengandung total alkali antara 8,12 - 11,81% termasuk dalam rejim syenit dan granit, dan berdasarkan kandungan K2O antara 5,36 - 6,94% berasal dari jenis magma K-tinggi sampai ultra-potassik. Granit Natuna, Bangka dan Singkep berasal dari jenis batuan beku dalam dan magma kalk-alkalin yang berhubungan dengan penunjaman, sedangkan granit Sibolga berasal dari jenis magma K-tinggi - ultra-potassik sebagai granit busur kepulauan. Berdasarkan komposisi unsur kimia utama, granit di Kawasan Barat Indonesia dapat dibagi dalam dua, yaitu granit Sibolga yang mewakili P. Sumatera, dipengaruhi oleh sistem tektonik busur P. Sumatera. Granit Bangka dan Singkep dapat mewakili suatu jalur granit di perairan Kawasan Barat Indonesia yang dipengaruhi oleh tektonik busur belakang. Kata kunci: jenis magma, karakteristik geokimia, unsur utama, dan Kawasan Barat Indonesia
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Burrows, Neil D. "Fire dependency of a rock-outcrop plant Calothamnus rupestris (Myrtaceae) and implications for managing fire in south-western Australian forests." Australian Journal of Botany 61, no. 2 (2013): 81. http://dx.doi.org/10.1071/bt12240.
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Granite outcrops embedded in south-western Australian forests provide habitat for unique biotic assemblages and refugia for fire-sensitive taxa. Discontinuous vegetation and natural barriers to fire spread enable outcrops to function as fire refugia, provided fires in the surrounding forest are not of high intensity. In Summer 2003, lightning started a fire in jarrah forest that had not been burnt for almost 20 years. The high-intensity fire burned the vegetation on Mount Cooke, a large granite outcrop, providing an opportunity to study the response of Calothamnus rupestris Schauer, a fire-sensitive serotinous plant. The population was killed by the fire, but readily regenerated from seed stored in woody capsules. The post-fire population reached maturity after ~7.5 years, whereas the seed bank is unlikely to recover to the pre-fire level until ~14 years. The likelihood of intense forest wildfires affecting outcrop communities can be reduced by frequent low-intensity prescribed burning in the surrounding forests to reduce fuel hazard and quantity. Low-intensity forest fires are unlikely to be lethal to sensitive granite-outcrop communities.
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Lu, Shu Qiang, and Mo Xu. "The Stability Analysis of Over-Dip Stratoid Structure Rock Slope." Advanced Materials Research 446-449 (January 2012): 1963–66. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.1963.
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The rock mass structure of granite is massive, so the stability of granite slope is good. Massive rock become stratoid structure when the rock mass contain discontinuities such as joints and faults. The deformation and destruction of the slope rock mass is controlled by the behaviour and orientation of the discontinuities. Especially, the over-dip discontinuities controlled the slope stability. In this paper, based on the abundant field investigation on the slope in left bank diversion tunnel inlets of Nuozadu power station in Lancang River, the types of rock mass structures and the combination between structural planes and slope surface are studied in detail so as to analyze the slope deformation mechanism. Finally, the slope stability is researched systematically by limit equilibrium method and FLAC numerical simulation analysis. A set of technical and methodological system on stability research of over-dip stratoid structure rock slope will hoped to be established.
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Beaman, Robin J., James J. Daniell, and Peter T. Harris. "Geology - benthos relationships on a temperate rocky bank, eastern Bass Strait, Australia." Marine and Freshwater Research 56, no. 7 (2005): 943. http://dx.doi.org/10.1071/mf04306.
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To better understand the possible relationships between the geology of the seabed and the associated biological communities, a multibeam sonar survey over New Zealand Star Bank in the eastern Bass Strait was conducted. A hierarchical method of benthic habitat mapping was applied to the secondary biotope and biological facies levels at the site (<10 km) scale. Four secondary biotopes and four biological facies have been defined on the basis of geomorphology revealed by the bathymetry model and the results of statistical analysis of the sediment and underwater video transect data over the bank. The major differences that control the distribution of biological communities in the New Zealand Star Bank area appear to be related to variations in substrate. (1) Hard-ground features related to high-relief granite outcrops are associated with diverse and abundant sessile and motile fauna. These faunal communities may be biologically modified to patchy barrens habitat by grazing urchins. (2) Unconsolidated sediment on a flat seabed is associated with sparse small sponges on the inner shelf. On the middle shelf and seaward of bank, the flat and muddy seabed supports a community dominated by infauna. (3) Unconsolidated sediment on a low-relief seabed is associated with an increase in the density and sizes of sponges concentrated on any low-relief feature raised above the surrounding flat seabed.
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Yu, Zhi-Feng, Qi-Ming Peng, Zheng Zhao, Ping-An Wang, Ying Xia, Yu-Qi Wang, and Hao Wang. "Geochronology, Geochemistry, and Geodynamic Relationship of the Mafic Dykes and Granites in the Qianlishan Complex, South China." Minerals 10, no. 12 (November 29, 2020): 1069. http://dx.doi.org/10.3390/min10121069.
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The Qianlishan complex, located in Hunan Province of South China, is closely associated with intense W-dominated polymetallic mineralization. The Qianlishan complex is composed of three phases: the main-phase porphyritic and equigranular granites, granite porphyry, and mafic dykes. Geochronologically, the zircon U-Pb dating results show that the porphyritic and equigranular granites have ages of approximately 159 and 158 Ma, respectively, similar to those of mafic dykes (approximately 158 Ma), while the granite porphyry was formed later at approximately 145 Ma. Geochemically, the mafic dykes are characterized by calc-alkaline high-Mg andesite (HMA) with high MgO, TiO2, Mg#, and CA/TH index. They exhibit significantly depleted εNd(t) and εHf(t) with high Ba/La, La/Nb, and (La/Yb)N, indicating that they formed from mixing melts of depleted asthenospheric mantle and metasomatized subcontinental lithospheric mantle (SCLM). The main-phase granites are peraluminous and are characterized by high SiO2, low (La/Yb)N ratios, and relative depletion in Ba, Sr, Ti, and Eu. They also display negative correlations between La, Ce, Y, and Rb contents, suggesting that they are highly fractionated S-type granites. Furthermore, they show high εNd(t) and εHf(t), CaO/Na2O ratios, HREE, and Y contents, indicating that they were produced by parental melting of ancient basement mixed with mantle-derived components. In contrast, the granite porphyry shows A-type signature granites, with higher εNd(t) and εHf(t) and CaO/Na2O ratios than the main-phase granites but similar Zr/Nb and Zr/Hf ratios to the mafic dykes, suggesting that they are the products of partial melting of a hybrid source with ancient basement and the mafic dykes. We thus infer that the slab roll-back led to generation of Qianlishan back-arc basalt and HMA and further triggered the formation of the Qianlishan granite.
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Wang, Jun. "Research on the Optimization of Dam Foundation Seepage Control System." Advanced Materials Research 594-597 (November 2012): 1143–48. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.1143.
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The starting time of Dragonite hydropower station in Dadu River Sichuan delayed, which led to the depth of the cofferdam cut-off wall reduced in actual construction. In order to adapt to this situation, it’s necessary to optimize the processing scheme of sand layer dam foundation which is put forward in the feasibility study stage. Combined with the characteristics of engineering, considering to reduce or cancel the curtain grouting in coarse grain granite foundation of riverbed on the right bank in the feasibility stage design, this paper is aimed to study on the optimization design of Dragonite hydropower station dam foundation. The paper has not only a great guiding significance in engineering construction process, but also gives references to the similar earth-rock dam project for treatment of sand layer dam foundation and the arrangement of dam foundation seepage control system.
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Collins, William J., Hui-Qing Huang, Peter Bowden, and A. I. S. Kemp. "Repeated S–I–A-type granite trilogy in the Lachlan Orogen and geochemical contrasts with A-type granites in Nigeria: implications for petrogenesis and tectonic discrimination." Geological Society, London, Special Publications 491, no. 1 (May 3, 2019): 53–76. http://dx.doi.org/10.1144/sp491-2018-159.
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AbstractThe classical S–I–A-type granites from the Lachlan Orogen, SE Australia, formed as a tectonic end-member of the accretionary orogenic spectrum, the Paleozoic Tasmanides. The sequence of S- to I- to A-type granite is repeated at least three times. All the granites are syn-extensional, formed in a dominantly back-arc setting behind a single, stepwise-retreating arc system between 530 and 230 Ma. Peralkaline granites are rare. Systematic S–I–A progressions indicate the progressive dilution of an old crustal component as magmatism evolved from arc (S-type) to proximal back-arc (I-type) to distal back-arc (A-type) magmatism. The alkaline and peralkaline A-type Younger granites of Nigeria were generally hotter and drier than the Lachlan A-type granites and were emplaced into an anhydrous Precambrian basement during intermittent intracontinental rifting. This geodynamic environment contrasts with the distal back-arc setting of the Lachlan A-type granites, where magmatism migrated rapidly across the orogen. Tectonic discrimination diagrams are inappropriate for the Lachlan granites, placing them in the wrong settings. Only the peralkaline Narraburra suite of the Lachlan Orogen fits the genuine ‘within-plate’ setting of the Nigerian A-type granites. Such discrimination diagrams require re-evaluation in the light of an improved modern understanding of tectonic processes, particularly the role of extensional tectonism and its geodynamic drivers.
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Huraiová, Monika, Patrik Konečný, and Vratislav Hurai. "Niobium Mineralogy of Pliocene A1-Type Granite of the Carpathian Back-Arc Basin, Central Europe." Minerals 9, no. 8 (August 15, 2019): 488. http://dx.doi.org/10.3390/min9080488.
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A1-type granite xenoliths occur in alkali basalts erupted during Pliocene–Pleistocene continental rifting of Carpathian back-arc basin (Central Europe). The Pliocene (5.2 Ma) peraluminous calc-alkalic granite contains unusually high concentrations of critical metals bound in Nb, Ta, REE, U, Th-oxides typical for silica-undersaturated alkalic granites, and syenites: columbite-Mn, fergusonite-Y, oxycalciopyrochlore, Nb-rutile, and Ca-niobate (fersmite or viggezite). In contrast, it does not contain allanite and monazite—the main REE-carriers in calc-alkalic granites. The crystallization of REE-bearing Nb-oxides instead of OH-silicates and phosphates was probably caused by strong water deficiency and low phosphorus content in the parental magma. Increased Nb and Ta concentrations have been inherited from the mafic parental magma derived from the metasomatized mantle. The strong Al- and Ca-enrichment probably reflects the specific composition of the mantle wedge modified by fluids, alkalic, and carbonatitic melts liberated from the subducted slab of oceanic crust prior to the Pliocene-Pleistocene rifting.
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Mitropoulos, P., A. Katerinopoulos, and A. Kokkinakis. "Occurrence of primary almandine-spessartine-rich garnet and zinnwaldite phenocrysts in a Neogene rhyolite on the island of Chios, Aegean Sea, Greece." Mineralogical Magazine 63, no. 4 (August 1999): 503–10. http://dx.doi.org/10.1180/002646199548673.
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AbstractPrimary almandine and spessartine-rich garnet and zinnwaldite phenocrysts occur along with feldspar (plagioclase and sanidine) phenocrysts, in the rhyolite of Profitis Ilias, which is located on the SE coast of the island of Chios, Greece. The distinctive mineralogical composition of this rhyolite is described. Although formed in the back-arc tectonic environment of the Aegean volcanic arc, the Profitis llias rhyolite shows significant trace element compositional differences when compared with typical arc or back-arc volcanic rocks of the area. It shows extreme depletion in Sr and Ba and enrichment in Nb and Mn, and has much more affinity with A-type granites and particularly Li-mica granites.Apparently, both zinnwaldite and spessartine-rich garnet can be generated as primary phases from a granite melt enriched in volatile constituents at low P–T. This granite melt could be the residual product of an un-exposed, earlier formed, typical back-arc granite of the area, enriched in volatile constituents from a subcrustal source above the active mantle of the eastern Aegean area.The extensive and deep faulting in the broad eastern Aegean lithosphere section would have facilitated the rapid ascent of that volatile-enriched granite melt, the parent of the Profitis Ilias rhyolite.
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Mashavakure, Nilton, Arnold B. Mashingaidze, Robert Musundire, Edson Gandiwa, and Ezekia Svotwa. "Germinable weed seed-bank response to plant residue application and hand weeding under two contrasting tillage systems in a granite-derived clay loam soil in Zimbabwe." South African Journal of Plant and Soil 37, no. 3 (May 26, 2020): 227–35. http://dx.doi.org/10.1080/02571862.2020.1723721.
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Jofré, Gabriela, Christopher Reading, and Ismael di Tada. "Habitat selection in the Pampa de Achala toad, Bufo achalensis." Amphibia-Reptilia 28, no. 1 (2007): 129–38. http://dx.doi.org/10.1163/156853807779799126.
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AbstractHabitat selection in adult and juvenile Bufo achalensis was studied at La Ciénaga Stream, Pampa de Achala, Central Argentina from December 1998 to October 2001. Habitat preference was evaluated by comparing the observed use of each habitat type with its availability. Juveniles were surveyed on 32 occasions between January 1999 and March 2001 using 13 permanent transects. The effect of cattle on larval survivorship was also evaluated. Most adult and juvenile B. achalensis occurred within 300 m of each side of the breeding site stream. No correlation was found between body size and distances moved. Juveniles and adults selected granite outcrops after the breeding season and avoided the heavily grazed areas. Adults also selected the stream and used tall tussock grassland in proportion to its availability. Juveniles used loose, flat, relatively small stones as shelters whilst adults used larger rocks. The presence of cattle at the breeding sites directly reduced larval survivorship by trampling, and indirectly through sediment deposition at the breeding sites resulting from increased stream bank erosion. The habitat preferences of B. achalensis suggest that long term cattle grazing also affects them adversely through deterioration of their transition habitat from tall tussock grassland to short sward. Future conservation management plans for B. achalensis must include the protection of the breeding sites and the surrounding terrestrial area if they are to be effective.
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Hurai, Vratislav, Monika Huraiová, and Patrik Konečný. "REE Minerals as Geochemical Proxies of Late-Tertiary Alkalic Silicate ± Carbonatite Intrusions Beneath Carpathian Back-Arc Basin." Minerals 11, no. 4 (March 31, 2021): 369. http://dx.doi.org/10.3390/min11040369.
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The accessory mineral assemblage (AMA) of igneous cumulate xenoliths in volcanoclastic deposits and lava flows in the Carpathian back-arc basin testifies to the composition of intrusive complexes sampled by Upper Miocene-Pliocene basalt volcanoes. The magmatic reservoir beneath Pinciná maar is composed of gabbro, moderately alkalic to alkali-calcic syenite, and calcic orthopyroxene granite (pincinite). The intrusive complex beneath the wider area around Fiľakovo and Hajnáčka maars contains mafic cumulates, alkalic syenite, carbonatite, and calc-alkalic granite. Both reservoirs originated during the basaltic magma underplating, differentiation, and interaction with the surrounding mantle and crust. The AMA of syenites is characterized by yttrialite-Y, britholite-Y, britholite-Ce, chevkinite-Ce, monazite-Ce, and rhabdophane(?). Baddeleyite and REE-zirconolite are typical of alkalic syenite associated with carbonatite. Pyrochlore, columbite-Mn, and Ca-niobates occur in calc-alkalic granites with strong peralkalic affinity. Nb-rutile, niobian ilmenite, and fergusonite-Y are crystallized from mildly alkalic syenite and calc-alkalic granite. Zircons with increased Hf/Zr and Th/U ratios occur in all felsic-to-intermediate rock-types. If rock fragments are absent in the volcanic ejecta, the composition of the sub-volcanic reservoir can be reconstructed from the specific AMA and zircon xenocrysts–xenolith relics disintegrated during the basaltic magma fragmentation and explosion.
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Horishnyj, Pavlo, and Anastasia Pavelchuk. "RELIEF OF THE QUARRIES OF THE MIDDLE POBUZHZHIA (ON THE EXAMPLE SABARIV QUARRY)." PROBLEMS OF GEOMORPHOLOGY AND PALEOGEOGRAPHY OF THE UKRANIAN CARPATHIANS AND ADJACENT AREAS, no. 09 (01) (September 25, 2019): 101–16. http://dx.doi.org/10.30970/gpc.2019.1.2805.
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Abstract. The twenty-seven active quarries for the extraction of building materials are located on the territory of the Middle Pobuzhzhia. The quarries of the crystalline rocks (granite, migmatite, granodiorite, charnockite, etc.) are dominant. Also, there are loam and less often sand quarries. They are concentrated in the western part of the Middle Pobuzhzhia, near city Vinnytsia. Most of the them are the type of closed stepped quarries. The quarries of the crystalline rocks are predominantly rectangular in shape with narrow benches of working benches and a flat pit floor without heaped forms of relief. Loam quarries are usually gradually declining, some of them are now inactive having internal sheating dumps. The length of such quarries is 300 – 450 m, with one working highwall. Sand quarries are partially active and covered with turf. The length of these quarries is usually 300 – 350 m, with up to 2 – 3 highwalls, also there are external sheating dumps. The Sabariv granite quarry, located 1 km south of city Vinnytsia on the right bank of the Southern Bug River is carefully surveyed. The extraction of useful rocks dates back to 1958. Mining is carried out by one overburden and three extraction highwalls. The maximum length of the quarry is 620 m, width – 370 m, depth – 54 m. The length of extraction benches is 14 m. The quarry has the excavated (denudation) and heaped (accumulative) forms of relief. The excavated relief consists of a mine floor, benches of the overburden stratum and extraction highwalls. The mine floor has a shape close to the rectangle. It is made of the third production horizon of the quarry where currently the mining works are carrying out and of the insubstantial part of the second extraction highwalls toe. The shape of a surface of the mine floor is generally aligned. The mine floor is bounded by the little changed and worked out northern, western and eastern mine walls, western part of the southern wall and significantly changed eastern part of the southern wall. The quarry has the one overburden and three extraction highwalls. Benches are located between the benches of different levels. Their maximum width is 50 m. At least, the benches of three levels can be traced. The heaped relief of the Sabariv quarry is presented predominantly by external sheating dumps of the overburden strata. They do not have a specific location. The dumps are terrace-like and have a shape of elongated embankments. They are located at elevations of 260–271 meters. The height of the dry dump is 10–15 m. The dumps of the overburden strata are recultivated. The forest melioration is carried out throughout the territory. The inner quarry dumps are located on the mine floor. Such dumps are not widespread and have low capacity. Key words: quarry; mining relief; excavated relief; heaped forms; Middle Pobuzhzhia.
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Broska, Igor, and Igor Petrík. "Variscan thrusting in I- and S-type granitic rocks of the Tribeč Mountains, Western Carpathians (Slovakia): evidence from mineral compositions and monazite dating." Geologica Carpathica 66, no. 6 (December 1, 2015): 455–71. http://dx.doi.org/10.1515/geoca-2015-0038.
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AbstractThe Tribeč granitic core (Tatric Superunit, Western Carpathians, Slovakia) is formed by Devonian/Lower Carboniferous, calc-alkaline I- and S-type granitic rocks and their altered equivalents, which provide a rare opportunity to study the Variscan magmatic, post-magmatic and tectonic evolution. The calculatedP-T-Xpath of I-type granitic rocks, based on Fe-Ti oxides, hornblende, titanite and mica-bearing equilibria, illustrates changes in redox evolution. There is a transition from magmatic stage atTca. 800–850 °C and moderate oxygen fugacity (FMQ buffer) to an oxidation event at 600 °C between HM and NNO up to the oxidation peak at 480 °C and HM buffer, to the final reduction at ca. 470 °C at ΔNN= 3.3. Thus, the post-magmatic Variscan history recorded in I-type tonalites shows at early stage pronounced oxidation and low temperature shift back to reduction. The S-type granites originated at temperature 700–750 °C at lower water activity and temperature. TheP-Tconditions of mineral reactions in altered granitoids at Variscan time (both I and S-types) correspond to greenschist facies involving formation of secondary biotite. The Tribeč granite pluton recently shows horizontal and vertical zoning: from the west side toward the east S-type granodiorites replace I-type tonalites and these medium/coarse-grained granitoids are vertically overlain by their altered equivalents in greenschist facies. Along the Tribeč mountain ridge, younger undeformed leucocratic granite dykes in age 342±4.4 Ma cut these metasomatically altered granitic rocks and thus post-date the alteration process. The overlaying sheet of the altered granites is in a low-angle superposition on undeformed granitoids and forms “a granite duplex” within Alpine Tatric Superunit, which resulted from a syn-collisional Variscan thrusting event and melt formation ~340 Ma. The process of alteration may have been responsible for shifting the oxidation trend to the observed partial reduction.
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Tao, Lu, Fa-Bin Pan, Rong Liu, Chong Jin, Bao-Jian Jia, and Xiaobo He. "Petrogenesis of the Cretaceous granitoids in Zhejiang, northeast South China Block and their implications for episodic retreat and roll-back of the Paleo-Pacific Plate." GSA Bulletin 132, no. 7-8 (November 20, 2019): 1514–36. http://dx.doi.org/10.1130/b35426.1.
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Abstract Two Cretaceous granitoid belts (i.e., the northwest and southeast belts) have been identified in Zhejiang, northeast South China Block. In this study, seven granitoid plutons from both the two belts were collected for zircon U-Pb dating, whole-rock geochemistry, Sr-Nd isotope, and zircon Hf isotope analyses. Chronologically, the Longyou (132 Ma), Sucun (136 Ma), Shanghekou (131 Ma), and Huangshitan (ca. 126 Ma) plutons from the northwest belt display older magma crystallization age than those of the Xiaoxiong (100 Ma), Zhujiajian (108 Ma), and Qingbang island (108 Ma) plutons from the southeast belt. The Sucun quartz monzonite and the Longyou, Shanghekou, Zhujiajian, and Qingbang island granites therein are fractionated I-type granites (i.e., partial melting of meta-igneous rocks) with relatively moderate-low Zr saturation temperature (723–823 °C) and pronouncedly evolved Nd and Hf isotopic compositions (εNd(t) = –8.17 to –5.67 and εHf(t) = –15.07 to –5.67), indicating that they are derivatives of ancient crustal melt-dominated magmas. The Huangshitan granite shows A-type granitic (i.e., granites that are alkaline and anhydrous and from anorogenic setting) features with high Ga/Al (3.47–5.58), rare earth element (REE) content (271–402 ppm), and Zr saturation temperature (781–889 °C). It holds less enriched Nd and Hf isotopic compositions (εNd(t) = –4.13 to –3.60 and εHf(t) = –5.90 to –2.16) and is attributed to partial melting of mature crustal materials with minor basaltic magma incorporation. The Xiaoxiong (quartz) syenitic porphyry is characterized by moderate SiO2 content (60.68–69.92 wt%), high alkali (9.03–11.66 wt%) and REE contents with fractionated REE pattern [(La/Yb)N = 13.8–26.1]. Its relatively depleted Nd and Hf isotopic compositions (εNd(t) = –3.67 to –3.42 and εHf(t) = –5.76 to –2.25) imply that it could be a derivative of basaltic magma from K-rich metasomatized mantle. Available geochronological data indicate that there were two episodic magmatic pulses at ca. 140–120 Ma and ca. 110–85 Ma associated with the Paleo-Pacific Plate underthrusting beneath the northeast South China Block. Here we put forward an episodic slab retreat and roll-back model to account for generation of these magmatic rocks. Firstly, the subducting Paleo-Pacific slab roll-back initiated at ca. 140 Ma and reached climax at ca. 130–120 Ma, which led to formation of the Longyou, Sucun, and Shanghekou I-type granites and the Huangshitan A-type granite, respectively. Subsequently, a flat slab subduction stage occurred with eastward trench retreat, causing a period of magmatic quiescence from ca. 120 to 110 Ma. The following second slab roll-back started at ca. 110 Ma and reached climax at ca. 100 Ma, giving rise to the earlier Zhujiajian and Qingbang island I-type granites and the later Xiaoxiong (quartz) syenitic porphyry.
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Yan, Changgen, Tong Yuan, and Kai Wang. "Unloading Phenomena Characteristics in Brittle Rock Masses by A Large-Scale Excavation in Dam Foundation." Open Civil Engineering Journal 8, no. 1 (September 4, 2014): 177–82. http://dx.doi.org/10.2174/1874149501408010177.
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Xiaowan Hydropower station’s dam located in south west of China is the second highest arch dam in the world (h = 292 m), its foundation is based on brittle rocks of biotite granite gneiss and amphibolites plagioclase gneiss. A large-scale excavation around the foundation of the dam was conducted, near to 90 meters horizontal depth excavation and 130 meters vertical depth excavation, so the foundation dam was marked by a significant deformation and a severe damage near the excavation zone, namely excavation distributed zone (EDZ). This damage was caused by the unloading process. According to the in situ investigation, the characteristics of unloading rock masses were described. With the acoustic wave velocity monitoring method, the unloading rock masses characteristics of time effect and space distribution are summarized. Usually the unloading process causes fractures in rock masses along two perpendicular directions in the plane of the bank slope, one is parallel to the dam base slope, and the other is parallel to the river with steep-dip angle. Near to the excavation surface, the excavation damage are more serious, and from the high elevation area to low elevation area, the damage caused by unloading are becoming stronger and stronger, and the bottom of dam base is most damaged. The unloading deformation has a direct temporal dependence; in general, after the excavation, the unloading deformation increases quickly during the firsts 90 days, and increase by a slow rate from 90 to 180 days and after that the unloading deformation will be small enough to be neglected.
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T. N. Harrison, I. Parsons, and P. E. Brown. "Mineralogical evolution of fayalite-bearing rapakivi granites from the Prins Christians Sund pluton, South Greenland." Mineralogical Magazine 54, no. 374 (March 1990): 57–66. http://dx.doi.org/10.1180/minmag.1990.054.374.05.
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AbstractThe Prins Christians Sund rapakivi granite pluton in South Greenland is a member of the early Proterozoic ‘Rapakivi Suite’ and is emplaced into early Proterozoic Ketilidian migmatites. The pluton is composed predominantly of black or dark brown monzonites and quartz monzonites (collectively, rapakivi granites), although a localised white facies is developed adjacent to metasedimentary xenoliths. The back rapakivi granites are extremely fresh and have an anhydrous primary mafic mineralogy of olivine and orthopyroxene, with rare inverted pigeonite and clinopyroxene; minor amounts of biotite and amphibole occur in most fayalite-bearing rapakivi granites. Feldspars in these rocks are black and non-turbid. The white rapakivi granites have a wholly hydrous mafic silicate assemblage and turbid, white or cream-coloured feldspars. Electron microprobe analyses of the mafic silicates in the black rapakivi granites show that they are Fe-rich, comprising fayalite (Fa93−96.5), orthopyroxene (Fs77−81), ferro-pargasitic and ferro-edenitic hornblende (Fe/(Fe + Mg) = 0.72−0.93), and biotite (Fe/(Fe + Mg) = 0.77−0.88). Both biotite and amphibole crystallised subsolidus, and often adopt symplectic morphologies. Biotite has formed in response to a fayalite-consuming reaction at temperatures below 650–700°C and fO2, of 10−16.5 to 10−17.5 bars, and continued to grow under reducing conditions below the QFM buffer to temperatures below 450–500°C. Orthopyroxene formed in response to a low-pressure fayalite-consuming reaction in the melt. The correlation of black, pristine feldspar with anhydrous mafic silicates, and of turbid feldspar with hydrous phases suggests either that the feldspars reflect the anhydrous nature of the parent magma, or more likely that the mafic mineralogy of the white rapakivi granites is secondary.
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Nayaju, Ajay Babu, and Naresh Kazi Tamrakar. "Evaluation of fine aggregates from the Budhi Gandaki-Narayani River, central Nepal for mortar and concrete." Journal of Nepal Geological Society 58 (June 24, 2019): 69–81. http://dx.doi.org/10.3126/jngs.v58i0.24575.
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Huge amounts of construction materials are required to fulfill construction works, which are being undertaken by local and Government levels. In this regard, searching for good quality construction materials is a tough job. The Budhi Gandaki-Narayani River is rich in carrying natural fine aggregates from the Higher and the Lesser Himalayas, which are extensively exposed along its bank. Currently ongoing and future hydro power projects, will require a tremendous amount of fine aggregates. In light of this, the present study was made to evaluate fine aggregates of the Budhi Gandaki-Narayani River. The gradation curves of fine aggregates from this river varied from well graded to uniform graded. Compositional analysis shows that quartz is dominant over other minerals. Rock fragments are composed of gneiss, schist, quartzite, metasandstone, phyllite, shale, granite, etc. Deleterious materials excluding organic matter range from 0.3 % to 1.5 % and organic matter present in range from 0.57 % to 1.11 %. The trend of presence of inorganic deleterious material and organic matter is increasing towards southern segments of the river, but they remain below 2%. Mean roundness of particles ranges from 1.88 to 2.54. Bulk dry density of fine aggregate is below 2 gm/cm³. Similarly, the specific gravity ranges between 1.49 and 1.79. Fineness modulus ranges between 1.36 and 3.50 showing that, coarse, medium, fine and very fine sediments are distributed along the stretch of river. Water absorption value of fine aggregate ranges from 0.48 % to 2.87 %. When using fine aggregates from southern segments of the Budhi Gandaki-Narayani River, reduction of mica and beneficiation process will enhance and provide better result for smooth plastering, rendering and screeding.
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JIANG, YAO-HUI, SHAO-YONG JIANG, KUI-DONG ZHAO, and HONG-FEI LING. "Petrogenesis of Late Jurassic Qianlishan granites and mafic dykes, Southeast China: implications for a back-arc extension setting." Geological Magazine 143, no. 4 (April 26, 2006): 457–74. http://dx.doi.org/10.1017/s0016756805001652.
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A late Mesozoic belt of volcanic-intrusive complexes occurs in Southeast China. The Qianlishan granites are distributed in the northwest of the belt. The pluton is composed of porphyritic biotite granite (153 Ma) and equigranular biotite granite (151 Ma) and was intruded by granite-porphyry dykes (144 Ma) and mafic dykes such as lamprophyre and diabase (142 Ma). The granitic rocks, consisting mainly of K-feldspar, plagioclase, quartz and Fe-rich biotite, have SiO2 contents of 72.9–76.9%, and are enriched in alkalis, rare earth elements (REE), high field strength elements (HFSE) and Ga with high Ga/Al ratios, but depleted in Ba, Sr and transition metals. Trace-element geochemistry and Sr–Nd isotope systematics further imply that the Qianlishan granitic magmas were most probably derived by partial melting of Palaeo- to Mesoproterozoic metamorphic lower-crustal rocks that had been granulitized during an earlier thermal event. These features suggest an A-type affinity. The Qianlishan lamprophyre and neighbouring coeval mafic dykes (SiO2 = 47.9–53.8 wt%) have high MgO and compatible element contents. These rocks also have high K2O contents and are enriched in alkalis, light REE, large ion lithophile elements, and depleted in HFSE. They have low initial εNd values and relatively high initial 87Sr/86Sr ratios. We suggest a subduction-modified refractory lithospheric mantle (phlogopite-bearing harzburgite or lherzolite) for these high-Mg potassic magmas. The Qianlishan diabases (SiO2 = 48.4–48.7 wt%) are alkaline and have high TiO2 and total Fe2O3 contents, together with the positive initial εNd value, suggesting derivation from fertile asthenopheric mantle (phlogopite-bearing lherzolite). A back-arc extensional setting, related to subduction of the Palaeo-Pacific plate, is favoured to explain the petrogenesis of the Qianlishan granites and associated mafic dykes. Between 180 and 160 Ma, Southeast China was a continental arc, forming the 180–160 Ma plutons of the late Mesozoic volcanic-intrusive complex belt, and the lower-crust was granulitized. Since 160 Ma the northwestern belt has been in a back-arc extensional setting as a consequence of slab roll-back, resulting in the lithosphere thinning and an influx of asthenophere. The upwelling asthenosphere, on the one hand, induced the local lithospheric mantle to melt partially, forming high-Mg potassic magmas, and on the other hand it underwent decompression melting itself to form alkaline diabase magma. Pulsatory injection of such high-temperature magmas into the granulitized crustal source region induced them to partially melt and generate the A-type magmas of the Qianlishan granitic rocks.
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Mohammadi, Nadia, Christopher R. M. McFarlane, and David R. Lentz. "U–Pb Geochronology of Hydrothermal Monazite from Uraniferous Greisen Veins Associated with the High Heat Production Mount Douglas Granite, New Brunswick, Canada." Geosciences 9, no. 5 (May 15, 2019): 224. http://dx.doi.org/10.3390/geosciences9050224.
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A combination of in situ laser ablation inductively coupled plasma–mass spectrometry (LA ICP–MS) analyses guided by Scanning Electron Microscope–Back-Scattered Electron imaging (SEM–BSE) was applied to hydrothermal monazite from greisen veins of the Late Devonian, highly evolved, uraniferous Mount Douglas Granite, New Brunswick, Canada. Understanding the uraniferous nature of the suite and characterizing the hydrothermal system that produced the associated mineralized greisen veins were the main goals of this study. The uraniferous nature of the Mount Douglas Granite is evident from previous airborne radiometric surveys, whole-rock geochemical data indicating high U and Th (2–22 ppm U; 19–71 ppm Th), the presence of monazite, zircon, xenotime, thorite, bastnaesite, and uraninite within the pluton and the associated hydrothermal greisen veins, as well as anomalous levels of U and Th in wolframite, hematite, and martite within greisen veins. New U–Pb geochronology of hydrothermal monazite coexisting with sulfide and oxide minerals yielded mineralization ages ranging from 344 to 368 Ma, with most of them (90%) younger than the crystallization age of the pluton (368 ± 3 Ma). The younger mineralization age indicates post-magmatic hydrothermal activities within the Mount Douglas system that was responsible for the mineralization. The production of uraniferous greisen veins by this process is probably associated with the High Heat Production (HHP) nature of this pluton, resulting from the radioactive decay of U, Th, and K. This heat prolongs post-crystallization hydrothermal fluid circulation and promotes the generation of hydrothermal ore deposits that are younger than the pluton. Assuming a density of 2.61 g/cm3, the average weighted mean radiogenic heat production of the Mount Douglas granites is 5.9 µW/m3 (14.1 HGU; Heat Generation Unit), in which it ranges from 2.2 µW/m3 in the least evolved unit, Dmd1, up to 10.1 µW/m3 in the most fractionated unit, Dmd3. They are all significantly higher than the average upper continental crust (1.65 µW/m3). The high radiogenic heat production of the Mount Douglas Granite, accompanied by a high estimated heat flow of 70 mW/m2, supports the assignment of the granite to a ‘hot crust’ (>7 HGU) HHP granite and highlights its potential for geothermal energy exploration.
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Luan, Shuai, Fenglai Wang, Tiehong Wang, Zhao Lu, and Weihou Shui. "Characteristics of Gravelly Granite Residual Soil in Bored Pile Design: An In Situ Test in Shenzhen." Advances in Materials Science and Engineering 2018 (October 16, 2018): 1–13. http://dx.doi.org/10.1155/2018/7598154.
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Granite residual soil is widely distributed in south China and is treated as a special soil. Its design parameters in rotary drilling bored piles are a matter of debate due to lack of in-situ pile load tests. Back-analysis of test piles is a reliable means of studying the geotechnical capacity of granite residual soil for pile design. In this study, a series of in situ tests was conducted comprising six full-scale instrumented test piles in gravelly granite residual soil in Shenzhen to consider the effects of different construction methods. The six piles were constructed with three different rotary drilling methods. Two commonly used design methods were investigated in the back-analysis: the SPT and effective stress methods. The results of the loading tests and strain gauges were used to obtain the back-analyzed parameters of the ultimate shaft resistance and ultimate base resistance for gravelly granite residual soil with these two design methods.
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Le, Phuc Duc, Hung Phu Tran, and Thang Dai Tran. "MINERAL - PETROGRAPHICAL, PETROCHEMICAL CHARACTERISTICS OF XUAN THU GRANITOID MASSIF, QUANG NGAI PROVINCE." Science and Technology Development Journal 12, no. 10 (May 28, 2009): 119–31. http://dx.doi.org/10.32508/stdj.v12i10.2306.
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The first time, Xuanthu granitoid massif was researched and arranged into component of Bana complex in project of 1/50,000 scale geological mapping and minerals prediction of Quangngai sheets (Than Duc Duyen et al, 1999). The investigations carried out within area of Nuocnhieu stream, SE corner of Xuanthu massif which has displayed mainly plutonic formations, such as biotite granite, medium - coarse granular 2 mica granite, fine granular granite and fine granular 2 mica granite. Vein phases are commonly aplite, pegmatoid, porphyry granite.... This paper is mainly to research on mineral - petrography and petro - geochemical characteristics as well as to make more clearly about material component, mineral forming order, forming original explaining and related mineralizations of Xuanthu granitoid massif.
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Schroeter, B., T. G. A. Green, and R. D. Seppelt. "The history of Granite House and the western geological party of Scott's Terra Nova expedition." Polar Record 29, no. 170 (July 1993): 219–24. http://dx.doi.org/10.1017/s0032247400018520.
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ABSTRACTIn summer 1911—1912, during Robert Falcon Scott's Terra Nova expedition (1910–1913) a field party of four men led by the geologist Griffith Taylor surveyed the coast and hinterland of Victoria Land, Antarctica. During their stay at Cape Geology (77°00'S, 162°35'E), Granite Harbour, the members of the ‘western geological party’ built Granite House, a rock shelter used as a kitchen. The field party finished its work in the Granite Harbour region in the second week of January 1912, but heavy sea ice prevented Terra Nova from reaching the prearranged meeting point at the entrance to the bay. Faced with the possibility of being trapped for the winter, the party left Granite Harbour and travelled overland back toward the winter quarters on Ross Island. One month later the party was picked up by Terra Nova and was returned safely to Cape Evans. During an expedition to Granite Harbour in January-February 1992, the authors discovered an 80-year-old note left by the field party in a cigarette tin in the vicinity of Granite House. Dated 14 January 1912, the note was written by Taylor to Lieutenant H.L.L. Pennell, the skipper of Terra Nova, to let him know that the party had left for Cape Roberts. Granite House is a significant relic of the ‘heroic era’ and merits protection.
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Carozzi, Albert, and Marguerite Carozzi. "Franz Joseph Märter, Travel Companion of Johann David Schöpf in a Journey From Philadelphia to Florida and the Bahamas in 1783-1784." Earth Sciences History 13, no. 1 (January 1, 1994): 5–20. http://dx.doi.org/10.17704/eshi.13.1.60757v173568t071.
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Two years before Johann David Schöpf (1752-1800) published his Beyträge … (1787), Franz Joseph Märter (1753-1827) sent letters from Pennsylvania, Virginia, South Carolina, and East-Florida to Ignaz von Born, describing plants, animals, and geological features of the newly independent states. These letters were speedily printed in Physikalische Arbeiten … in Vienna (1785). A last letter sent from the Bahamas appeared in the same periodical in 1786. Märter's geological observations are translated and analyzed here for the first time. His descriptions of various rocks along the Schuylkill River, upstream from Philadelphia (granites, limestones, marble quarries, widespread weathered iron ores), and his interpretation of the fossiliferous sandstones in the Appalachian mountains are very similar to those by Schöpf. So are Märter's observations of shell banks, either exposed in ditches many miles from the sea, or in cliffs at Yorktown, Virginia, and Wilmington, North Carolina, as well as his description of granite and of a large coal mine near Richmond, Virginia. Finally, both travelers noticed that the rocky cliffs in the Bahamas consisted of limestone formed by Muschelsand [beachrock]. We established that Märter and Schöpf traveled together from Philadelphia to the Bahamas (November 1783 to March 1784). But neither acknowledged the influence, or at least the presence of the other, probably for political reasons.
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Martin, C. Derek, Neil A. Chandler, and Rodney S. Read. "The role of convergence measurements in characterizing a rock mass." Canadian Geotechnical Journal 33, no. 2 (May 8, 1996): 363–70. http://dx.doi.org/10.1139/t96-014.
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Convergence measurements were taken during the construction of a circular shaft in massive granite. The convergence results were used to back-calculate the in situ horizontal stress orientation and magnitudes. The results from the convergence method were supported by other measurement techniques and numerical modelling. Key words: convergence, in situ stress, back-analysis.
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Okada, Katsuya, and Satoru Nakashima. "Combined Microspectroscopic Characterization of a Red-Colored Granite Rock Sample." Applied Spectroscopy 73, no. 7 (February 7, 2019): 781–93. http://dx.doi.org/10.1177/0003702818823555.
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Combined microspectroscopic mapping have been conducted on a red-colored Tenzan granite sample by using an original visible–fluorescence–Raman microspectrometer together with a low vacuum scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) without coating. Visible darkfield reflectance spectra were converted to L*a*b* color values and Kubelka–Munk (KM) spectra. Large a* value (red) positions correspond to large band areas at 500–560 nm, possibly due to hematite-like iron oxide, while large b* value (yellow) positions to large band areas at 450–500 nm, due to epidote-like mineral. Scanning electron microscopy–energy dispersive spectrometry analyses indicated that the reddish parts are Na and K-feldspars with low Fe contents (<0.5 wt%). Raman microspectroscopy could not detect hematite-like minerals. Since some hematite-like minerals were only identified by transmission electron microscope, they are considered to be submicron microcrystals disseminated in feldspar matrices. The KM spectra for prehnite-like minerals show a weak broad band around 430 nm due possibly to a ligand field band of Fe3+ without clear Fe2+–Fe3+ inter-valence charge transfer (IVCT) bands around 720 nm. Therefore, Fe in prehnite is not considered to be present as hematite-like iron oxide, but can be mainly present as Fe3+ replacing Al3+ in the crystal structure. Since determination of physicochemical states of Fe such as valence and coordination states (Fe2+ or Fe3+, oxide or in crystal lattice, etc.) and their distributions are extremely difficult, especially in complex colored materials such as rocks, the combined microspectroscopic methods are useful for their nondestructive characterization.
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Wang, Tianzuo, Linxiang Wang, Fei Xue, and Mengya Xue. "Identification of crack development in granite under triaxial compression based on the acoustic emission signal." International Journal of Distributed Sensor Networks 17, no. 1 (January 2021): 155014772098611. http://dx.doi.org/10.1177/1550147720986116.
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To explore the development mechanism of cracks in the process of rock failure, triaxial compression tests with simultaneous acoustic emission monitoring were performed on granite specimens using the MTS rock mechanics test system. The frequency-domain information of the acoustic emission signal was obtained by the fast Fourier transform. The Gutenberg–Richter law was used to calculate the acoustic emission signals and obtain the b-value dynamic curve in the loading process. Combined with the stiffness curve of granite specimens and acoustic emission signal in the time domain and frequency domain, the crack development characteristics in different stages were analyzed. The results showed that the acoustic emission signals of granite samples under triaxial compression can be divided into four stages: quiet period 1, active stage 1, quiet period 2, and active stage 2. b-value attained its maximum value in the active phase 2 when it is close to the sample loss, and then drops rapidly, which means the propagation of cracks and the formation of large cracks. The acoustic emission signal’s dominant frequency was not more than 500 kHz, mostly concentrated in the medium-frequency band (100–200 kHz), which accounted for more than 80%. The proportion of signals in each frequency band can reflect the distribution of the three kinds of cracks, while the change in low-frequency signals can reflect the breakthrough of microcracks and the formation time of macrocracks in granite samples. By fully analyzing the characteristics of acoustic emission signals in the time domain and frequency domain, the time and conditions of producing large cracks can be determined accurately and efficiently.
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Ager, C. M., and N. M. Milton. "Spectral reflectance of lichens and their effects on the reflectance of rock substrates." GEOPHYSICS 52, no. 7 (July 1987): 898–906. http://dx.doi.org/10.1190/1.1442360.
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Rock outcrops in arid and semiarid regions frequently have abundant lichen cover. We collected lichens and their granite, slate, and hornfels substrates in the Extremadura region of Spain and measured spectral reflectance in the 400–2500 nm region in the laboratory. Lichen cover as low as 30 percent masks the spectral features of spectrally flat rocks such as slate and hornfels. The sharp spectral features of granite are obscured at 60–80 percent lichen cover. The strong reflectance peak at 2220 nm in lichens interferes with recognition of the 2200 nm absorption band in hydroxyl‐bearing minerals that is used to locate hydrothermally altered and potentially mineral‐rich areas. However, lichen spectra are characterized by distinctive absorption features that occur in few minerals and can thus be used to identify lichen presence. From computer modeling of laboratory spectra, we conclude that Landsat Thematic Mapper (TM) band ratios of 3 : 4 and 5 : 2 best minimize lichen effects in TM image analysis.
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Amitrano, David, and Jean Schmittbuhl. "Fracture roughness and gouge distribution of a granite shear band." Journal of Geophysical Research: Solid Earth 107, B12 (December 2002): ESE 19–1—ESE 19–16. http://dx.doi.org/10.1029/2002jb001761.
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Prieto, B., P. Sanmartín, C. Silva, D. Vázquez-Nion, and B. Silva. "Deleterious effect plastic-based biocides on back-ventilated granite facades." International Biodeterioration & Biodegradation 86 (January 2014): 19–24. http://dx.doi.org/10.1016/j.ibiod.2013.06.018.
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Qin, Jin-hua, Cui Liu, and Jin-fu Deng. "Geochronology and geochemistry of igneous rocks in the southeastern Lesser Xing’an Range, northeastern China: petrogenesis and implications for the early Mesozoic tectonic evolution." Canadian Journal of Earth Sciences 57, no. 4 (April 2020): 506–23. http://dx.doi.org/10.1139/cjes-2018-0198.
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We present systematic U–Pb age data collected by laser ablation multi-collector inductively coupled plasma mass spectrometry, precise geochemical data, and Nd isotope data for igneous rocks from the southeastern Lesser Xing’an Range (SE LXR). The results indicate that the formation ages as follows: Maojiatun alkaline granite, 207.2 ± 0.84 Ma and 204.6 ± 0.93 Ma; Diorite porphyrite, 164.5 ± 0.97 Ma; and Tieli syenogranite, 186.7 ± 1.50 Ma. The alkaline granite has high silicon, potassium, alkali, and FeOT contents; it is enriched in high field strength elements, Zr, Hf, Th, Rb, and U; is depleted in Ba, Sr, Nb, Ta, P, Ti, etc.; and has high ratios of 10000Ga/Al. It shows an A2-type granite affinity. The Tieli alkali-feldspar granite has high total alkali contents and is enriched in high field strength elements and rare earth elements and depleted in Sr, Ba, Ti, and P, and shows varying degrees of alkalinity. Rocks from SE LXR display similar εNd (t) values with corresponding to Nd model ages of 1095 to 813 Ma. The igneous rocks from the SE LXR are proposed to be derived from melting of the Neoproterozoic lower crust and potential magma mixing with ancient crystalline basement. The formation of the Maojiatun alkaline granite occurred in response to a postorogenic event following the closure of the Paleo-Asian Ocean. However, the SE LXR exhibited an extensional back-arc tectonic setting in the Early Jurassic. The Middle Jurassic diorite porphyrite could be related to the temporary stagnation of the westward subduction of the Paleo-Pacific plate.
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Brown, Michael. "The mechanism of melt extraction from lower continental crust of orogens." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, no. 1-2 (March 2004): 35–48. http://dx.doi.org/10.1017/s0263593300000900.
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ABSTRACTMelt extraction is a process with a length scale that spans many orders of magnitude. Studies of residual migmatites and granulites suggest that melt has migrated from grain boundaries to networks of leucosome-filled structures to steeply inclined cylindrical or tabular granites inferred to have infilled ascent conduits. For example, in anatectic rocks from southern Brittany, France, during decompression-induced biotite-breakdown melting, melt is inferred to have been expressed from foliation-parallel structures analogous to compaction bands to dilation and shear bands, based on location of residual leucosome, and from this network of structures to ascent conduits, preserved as dykes of granite. The leucosome-filled deformation band network is elongated parallel to a sub-horizontal lineation, suggesting that mesoscale melt flow was focused primarily in the plane of the foliation along the lineation to developing dilatant transverse structures. The leucosome network connects with petrographic continuity to granite in dykes; however, the orientation of dykes discordant to fabric anisotropy suggests that their formation was controlled by stress, which indicates that the process is a fracture phenomenon. Blunt fracture tips and zigzag propagation paths indicate that the dykes represent ductile opening-mode fractures; these are postulated to have formed by coalescence of melt pockets. The structures record a transition from accumulation to draining; quantitative volume fluxes are calculated and presented for the generalised extraction process. The anatectic system may have converged to a critical state at some combination of melt fraction and melt distribution that enabled formation of ductile opening-mode fractures, but fractal distribution of inferred mesoscale melt-filled structures has not been demonstrated; this may reflect the inherent anisotropy and/or residual nature of the drained source. Melt extraction has been modelled as a self-organised critical phenomenon, but the mechanism of extraction is not described and the relationship between these models and the spatial and temporal granularity of lower continental crust is not addressed. Self-organised critical phenomena are driven systems involving ‘avalanches’ with a fractal frequency-size distribution; thus, the distribution of melt batch sizes might be expected to be fractal, but this has not yet been demonstrated in nature.
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Griesmeier, Gerit E. U., Christoph Iglseder, Ralf Schuster, and Konstantin Petrakakis. "Polyphase deformation along the South Bohemian Batholith-Moldanubian nappes boundary – The Freyenstein Fault System (Bohemian Massif/Austria)." Austrian Journal of Earth Sciences 113, no. 1-2 (June 1, 2020): 139–53. http://dx.doi.org/10.17738/ajes.2020.0009.
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Abstract This work describes the Freyenstein Fault System, which extends over 45 km in the southeastern part of the Bohemian Massif (Lower Austria). It represents a ductile shear zone overprinted by a brittle fault located at the eastern edge of the South Bohemian Batholith towards the Moldanubian nappes. It affects Weinsberg- and a more “fine-grained” granite, interlayered aplitic granite and pegmatite dikes as well as paragneiss of the Ostrong Nappe System. The ductile shear zone is represented by approximately 500 m thick greenschist-facies mylonite dipping about 60° to the southeast. Shear-sense criteria like clast geometries, SCC`-type shear band fabrics as well as abundant microstructures show top to the south/ southsouthwest normal shearing with a dextral strike-slip component. Mineral assemblages in mylonitized granitoid consist of pre- to syntectonic muscovite- and biotite-porphyroclasts as well as dynamically recrystallized potassium feldspar, plagioclase and quartz. Dynamic recrystallization of potassium feldspar and the stability of biotite indicate upper green-schist-facies metamorphic conditions during the early phase of deformation. Fluid infiltration at lower greenschist-facies conditions led to local sericitization of feldspar and synmylonitic chloritisation of biotite during a later stage of ductile deformation. Finally, a brittle overprint by a north-south trending, subvertical, sinistral strike-slip fault that shows a normal component is observed. Ductile normal shearing along the Freyenstein Shear Zone is interpreted to have occurred between 320 Ma and c. 300 Ma. This time interval is indicated by literature data on the emplacement of the hostrock and cooling below c. 300°C inferred from two Rb-Sr biotite ages measured on undeformed granites close to the shear zone yielding 309.6 ± 3 Ma and 290.9 ± 2.9 Ma, respectively. Brittle sinistral strike-slip faulting at less than 300°C presumably took place not earlier than 300 Ma. Early ductile shearing along the Freyenstein Fault System may be genetically, but not kinematically linked to the Strudengau Shear Zone, as both acted in an extensional regime during late Variscan orogenic collapse. A relation to other major northeast-southwest trending faults of this part of the Bohemian Massif (e.g. the Vitis-Pribyslav Fault System) is indicated for the phase of brittle sinistral movement.
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Wang, Z. H., Y. L. Tan, S. M. Li, T. Z. Wang, and X. C. Wu. "Experimental and Numerical Study on Mechanical Properties and Deformation Behavior of Beishan Granite considering Heterogeneity." Advances in Civil Engineering 2021 (April 22, 2021): 1–13. http://dx.doi.org/10.1155/2021/6622958.
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Disposal of high-level radioactive waste (HLW) deep underground is one of the most challenging research subjects in rock engineering. In China, Beishan granite is usually chosen as host rock for the construction of the HLW repository. In this study, mechanical tests are conducted on Beishan granite and the stress-strain state during the complete failure process is analyzed by numerical simulation. The results show that the tensile strength and uniaxial compressive strength of Beishan granite are 8.66 and 162.9 MPa, respectively. Dilatancy appears when the stress reaches about 81% of the peak strength. Heterogeneity is introduced by Weibull distribution in numerical simulation. With the increase of homogenization degree, the degraded elements are more easily to concentrate locally. Based on experimental and numerical simulation results, it is noticeable that the sample volume is basically in the state of compaction before reaching the peak strength. The elements are more likely to show expansion, and the splitting failure dominates the destroy mode when the confining pressure is relatively low. With increasing confining pressure, more and more degraded elements are concentrated in the shear band, which develops from the surface to the interior of the sample during loading. Therefore, the granite shows ductile mechanical response characteristics when the confining pressure is relatively high. The results are instructive for the construction of the repository.
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Enrique Chico Frias, Angel, and Edwin Javier Santamaría Freire. "Financial shielding that Bitcoin grants to capitals in the world." Investment Management and Financial Innovations 16, no. 3 (August 2, 2019): 49–61. http://dx.doi.org/10.21511/imfi.16(3).2019.06.
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Market forces are not the only influence on currency exchange rates. They can change due to monetary and fiscal policies among other international repercussions. Bitcoin, for its independence from all the central banks worldwide, has a natural shield that will change the direction in the economic policy of the industrialized countries. The research aim is to analyze the influence that indicators and financial assets can have on Bitcoin. The study tries to confirm the reasons why it has begun to be the solution in economies with unstable currencies.The behavior of the different agents appears as the core of the study. It is creating a backward 5-year work horizon. The data are continuous values, and they are the numerical variables for Pearson correlation analysis. The time series in fixed periods are the basis for the study of projections. Besides, the Relative Strength Index or Relative Strength Index called Welles Wilder is useful in the research. Bitcoin does not get influenced by the Dow Jones, gold price, and Gross Domestic Product (GDP). The independence in the creation of this cryptocurrency could in the long term end up turning it into a currency of world use. As a result, the understanding and management of this cryptocurrency could generate new ways of building the future monetary system. The new direction of the economy will be registered in the blockchain and not in a central bank.
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Manby, G. M. "The petrology of the Harkerbreen Group, Ny Friesland, Svalbard: protoliths and tectonic significance." Geological Magazine 127, no. 2 (March 1990): 129–46. http://dx.doi.org/10.1017/s0016756800013820.
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AbstractThe late Precambrian–early Palaeozoic rocks of Ny Friesland, which have been subjected to Caledonian deformation and metamorphism, constitute part of the Eastern Province or Terrane of Svalbard. The Harkerbreen group and other divisions of the Stubendorffbreen supergroup form a high-grade and intensely deformed core complex to this terrane which is bounded to the west by the Billefjorden Fault Zone and to the east by a major north–south shear zone. The Stubendorffbreen rocks exhibit two gneissic foliations, one axial planar to a large scale, F1 fold nappe closing to the east and the other axial planar to kilometre-scale upright F2 folds subsidiary to the Atomfjella Arch. Metamorphism in the mid-amphibolite facies range coincided with generation of these folds, and F3.crenulation folding was accompanied by waning P–T conditions. A significant proportion of the gneisses within the Harkerbreen group display silica–major element covariation patterns consistent with their position in the granodiorite field on the AFM plot. Incompatible, immobile element ratios Zr/Ti v. Nb/Y indicate affinities with rhyolites to rhyodacites which is also suggested by their REE profiles. Normalized multi-element plots of the gneisses are similar to those of granites from attenuated within-plate settings such as Mull and Skaergaard. The amphibolites which were intruded in the D1–D2 interval appear to be derivatives of fractionated basalts. They plot across the calk-alkaline tholeiite boundary on the AFM diagram, and the calc-alkaline character of some of the amphibolites is further suggested by their Yb-normalized Ce-Ta abundances. Zr-Ti-Y and REE abundances would support their derivation from a related suite of fractionated basalt liquids. On the Zr/Y v. Zr discrimination diagram the amphibolites appear to have compositions transitional between Mid Ocean Ridge and Within-Plate basalts whilst the Zr-Nb-Ta plot indicates Volcanic Arc Basalt affinities. Th-Hf-Ta and multi-element plots, however, indicate a marginal to back-arc basin setting possibly above a mature subduction zone. The late Caledonian Chydenius granite is an adamellite with mixed within-plate and syn-orogenic characteristics typical of post-collisional granites.
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Hu, Liang, Zheng, Zhou, Yang, and Zhu. "Tectonic Transformation and Metallogenesis of the Yanshan Movement during the Late Jurassic Period: Evidence from Geochemistry and Zircon U-Pb Geochronology of the Adamellites in Xingcheng, Western Liaoning, China." Minerals 9, no. 9 (August 28, 2019): 518. http://dx.doi.org/10.3390/min9090518.
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The Yanshan Movement occurred mainly during the Middle-Late Jurassic, and gave rise to NE trending structures, magmatic events, volcanism and mineral resources. The transformation and evolution of the movement during the Middle-Late Jurassic were investigated from the rock assemblage, geochemistry, and chronology in adamellites which were exposed in the Xingcheng area, western Liaoning. Two types of adamellites were recognized—biotite adamellites with the formation age of 172–168 Ma and garnet-bearing adamellites of 158–152 Ma. All the samples of the two types of adamellites displayed enriched characteristics with high content of SiO2 (66.86–75.55 wt.%) and total alkali (Na2O + K2O = 7.56–8.71 wt.%), high large ion lithophile element (LILE: K, Rb, Sr), and low high field strength element (HFSE: Ce, Ta, P, Ti). The biotite adamellites belong to metaluminous-peraluminous I-type granites, and show volcanic arc granite characteristics, and were formed by partial melting of the ancient crust in the compressional setting that resulting from the subduction of the Paleo-Pacific plate beneath the north margin of the North China Craton (NCC). The garnet-bearing adamellites are also metaluminous-peraluminous I-type granites, with characteristics of both the compressional and extensional regimes, which were formed at the middle-late stages of the continuing subduction of the Paleo-Pacific plate, while simultaneously, the frontal side of the subduction slab began to roll back, leading to an extensional environment. Combining with regional geophysical studies and our petrological and geochemical studies, we propose that the eastern segment of the northern margin of NCC may have been controlled by the Paleo-Pacific tectonic domain at the latest in the Middle Jurassic, while the initiation of the tectonic regime from a compressional to an extensional environment was during the Late Jurassic (158–152 Ma) as a response of the Yanshan Movement. Simultaneously, geochronological statistics of the ore deposits in western Liaoning show that the Mesozoic endogenetic metalliferous deposits formed in a compressive environment influenced by the subduction of the Paleo-Pacific plate, similar to the magma events in ages, and the magmatism provided the thermodynamic condition and the source of metallogenic hydrothermal fluid for mineralization.
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Liu, Guichun, Guangyan Chen, M. Santosh, Xin Qian, Zaibo Sun, Jian-Wei Zi, Tianyu Zhao, Qinglai Feng, and Shen Ma. "Tracking Prototethyan assembly felsic magmatic suites in southern Yunnan (SW China): evidence for an Early Ordovician–Early Silurian arc–back-arc system." Journal of the Geological Society 178, no. 4 (March 2, 2021): jgs2020–221. http://dx.doi.org/10.1144/jgs2020-221.
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Early Paleozoic trondhjemites, gneissic granites and alkali granites in southern Yunnan preserve important records of the tectonic evolution of the Prototethyan Ocean and regional correlations. Zircon ages suggest that these granitoids were emplaced from 476 to 436 Ma. The trondhjemites are characterized by high Na2O and low K2O contents, with εNd(t) values of −1.9 to −3.5 and εHf(t) values of −2.8 to +3.9. The trondhjemites were derived from an amphibolite source with a juvenile mafic component. The gneissic granites belong to the metaluminous low-K calc-alkaline series with an εNd(t) value of −6.2 and εHf(t) values of −5.0 to −0.4. The alkali granites belong to the high-K calc-alkaline series and yield εNd(t) values of −10.1 to −10.7 and εHf(t) values of −7.9 to −2.3. The gneissic granites were derived from an ‘ancient' lower mafic crust, whereas the alkali granites were derived from a meta-sedimentary source. These granitoids were formed during the subduction of the Prototethyan Ocean beneath the Simao Block and can be compared with similar igneous rocks from the Truong Son and Tam Ky-Phuoc Son zones in southern Laos. Our study, along with Early Paleozoic igneous suites from southern Laos, central Vietnam and the Malay Peninsula, suggests an arc–back-arc system along the northern margin of Gondwana.Supplementary material: Tables of zircon U–Pb and in-situ Hf and geochemical data are available at https://doi.org/10.6084/m9.figshare.c.5322386
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Le, Phuc Duc. "PETROGRAPHIC, MINERAL, GEOCHEMICAL CHARACTERISTICS OF BA NA GRANITOID." Science and Technology Development Journal 12, no. 7 (April 15, 2009): 58–71. http://dx.doi.org/10.32508/stdj.v12i7.2267.
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Ba Na granitoid is isometric shape, with exposure of 30 sqa km area. Petrographic composition is mainly coarse - medium grained biotite granite, included in the first phase. The fine grained leuco rock of the second phase is small massif in shape, distributed along fault in NE-SW direction. SiO, content of Bana granitoid is variation from 73.74% to 76.24%. Total of K2O +Na2O is from 7.32% to 8.33%. Ratio of K2O/Na2O: 1.66 - 2.07. This is S-Granite. Value of 147Sm/144Nd = 0,1249 is nearly stable crust material. Ratio of Sm/Nd is low. ena has negative value and very small proved that Ba Na granitoid must derive from crust source or mantle source which rich (EM). The age of source regional forming calculated from isotopic of Sm, Nd is 1.06 Ba (according to model of chondrite mantle source region) or 1.74 Ba (according to model of poor mantle source). The prospects of related mineralization of Ba Na granitoid is Sn (W, Nb, Ta) with amsemblage of topaz - cassiterite - tourmaline - quartz (sometime is Ta - Nb). The result of isotopic analysis of U Pb in zircon of Ba Na biotite granite sample at lab of Tasmania University, Australia, age of Ba Na is 242.9 +1.5 Ma and 240.6 2.2 Ma.
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Næraa, Tomas, Jens Konnerup-Madsen, Bjørn Hageskov, and Lalu Prasad Paudel. "Structure and petrology of the Dadeldhura Group, far western Nepal, Himalaya." Journal of Nepal Geological Society 35 (December 31, 2007): 21–28. http://dx.doi.org/10.3126/jngs.v35i0.23631.
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The granites, phyllites, schists, and gneisses of the Dadeldhura Group exhibit a significant Himalayan metamorphic imprint. The rocks of the group constitute a synform and the group is delimited by thrusts. The North Dadeldhura Thrust (NDT) zone is dominated by granitic mylonite with subordinate quartzite, quartz-chlorite schist, and amphibolite. In the quartz-chlorite schist from the NDT zone, relict kyanite is observed, which together with recrystallisation textures in the granitic mylonite indicate that low-temperature syn-tectonic retrogression has affected the thrust zone. Prograde garnets with spiral structures from a zone 2–4 km structurally above the base of the NDT are associated with mylonite-like rocks, and indicate distinct prograde shear zones in this area. This suggested that prograde thrust stacking has affected about 4 km wide north belt of the Dadeldhura Group. Rim thermobarometry from the garnet holding rocks shows that the minerals were re-equilibrated at 440–550 °C and 6.5–9.5 kbar. In the southern part of the Dadeldhura Group, textures in quartz and feldspar from the Saukhark Granite-Gneiss indicate that temperatures during recrystallisation were around 450–550 °C. These P–T estimates suggest that most of the now exposed rocks in the Dadeldhura Group experienced prograde epidoteamphibolite facies metamorphism during early orogenic build up and thrusting of the Dadeldhura Nappe. A subsequent syntectonic retrograde phase is observed in the NDT zone as low temperature recrystallisation of quartz and feldspar in mylonitic rocks, and chlorite and quartz in chlorite-grade rocks holding relict kyanite. Retrograde trusting was also focused along a distinct “back thrusting” zone within the northern part of the group.
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Helhel, Selcuk, Atalay Kocakusak, and Merve Sunel. "Determining loss tangent values of dry granite for potential S‐band applications." Microwave and Optical Technology Letters 62, no. 11 (June 15, 2020): 3476–84. http://dx.doi.org/10.1002/mop.32494.
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Karimzadeh, Z., and M. H. Tangestani. "APPLICATION OF WORLDVIEW-3 DATA IN ALTERATION MINERAL MAPPING IN CHADORMALU AREA, CENTRAL IRAN." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-4/W18 (October 18, 2019): 589–96. http://dx.doi.org/10.5194/isprs-archives-xlii-4-w18-589-2019.
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Abstract. WorldView-3 (WV-3), launched in August 2014, is a commercial imaging satellite with high spatial resolution that measures reflected radiation in VNIR-SWIR regions in 16 bands. The main objective of this study was to discriminate the alteration minerals in Chadormalu iron deposit area, central Iran, using band ratio techniques on the selected bands of this satellite. To identify the appropriate band ratios the spectral bands of WV-3 were investigated and assessed. Regarding to Fe3+, Fe2+, Al-OH, Fe-OH, Mg-OH and CO32− spectral absorption features, band ratios B5/B2, B13/B9, B13/B14 and B14/B16 were proposed for enhancement of ferrous and ferric iron bearing minerals, sericite, epidote, chlorite, and dolomite. Combination of field observations, geological map and high resolution spectra of rock samples were used to verify the results. Band ratio B5/B2, B13/B9, B13/B14 gray scale images respectively illustrated that Fe3+-rich minerals are occurring in granite, the Fe2+-rich minerals are enhanced in iron ore, green schist, and diorite units, and sericite is occurring in hydrothermally altered granite and iron ore. Since the Fe/Mg-OH vibrational mode in chlorite-epidote and spectral absorption feature of CO32− in dolomite occur in B16, the B14/B16 ratio highlighted chlorite-epidote-rich green schist, diorite and dolomitic marble. The false color composite image of B13/B14, B13/B9, and B14/B16 as RGB produced a large scale map which successfully discriminated the rock types and accompanying alteration minerals. This study demonstrated that WV-3 data have efficient spectral resolution to discriminate alteration minerals with Fe3+, Fe2+, Al-OH and Fe/Mg-OH or CO32− spectral absorption features.
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Cawood, Peter A., Chris J. Hawkesworth, Sergei A. Pisarevsky, Bruno Dhuime, Fabio A. Capitanio, and Oliver Nebel. "Geological archive of the onset of plate tectonics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, no. 2132 (October 2018): 20170405. http://dx.doi.org/10.1098/rsta.2017.0405.
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Plate tectonics, involving a globally linked system of lateral motion of rigid surface plates, is a characteristic feature of our planet, but estimates of how long it has been the modus operandi of lithospheric formation and interactions range from the Hadean to the Neoproterozoic. In this paper, we review sedimentary, igneous and metamorphic proxies along with palaeomagnetic data to infer both the development of rigid lithospheric plates and their independent relative motion, and conclude that significant changes in Earth behaviour occurred in the mid- to late Archaean, between 3.2 Ga and 2.5 Ga. These data include: sedimentary rock associations inferred to have accumulated in passive continental margin settings, marking the onset of sea-floor spreading; the oldest foreland basin deposits associated with lithospheric convergence; a change from thin, new continental crust of mafic composition to thicker crust of intermediate composition, increased crustal reworking and the emplacement of potassic and peraluminous granites, indicating stabilization of the lithosphere; replacement of dome and keel structures in granite-greenstone terranes, which relate to vertical tectonics, by linear thrust imbricated belts; the commencement of temporally paired systems of intermediate and high dT/dP gradients, with the former interpreted to represent subduction to collisional settings and the latter representing possible hinterland back-arc settings or ocean plateau environments. Palaeomagnetic data from the Kaapvaal and Pilbara cratons for the interval 2780–2710 Ma and from the Superior, Kaapvaal and Kola-Karelia cratons for 2700–2440 Ma suggest significant relative movements. We consider these changes in the behaviour and character of the lithosphere to be consistent with a gestational transition from a non-plate tectonic mode, arguably with localized subduction, to the onset of sustained plate tectonics. This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics'.
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Northrup, C. J., C. Isachsen, and S. A. Bowring. "Field relations, U-Pb geochronology, and Sm-Nd isotope geochemistry of the Point Lake greenstone belt and adjacent gneisses, central Slave craton, N.W.T., Canada." Canadian Journal of Earth Sciences 36, no. 7 (July 1, 1999): 1043–59. http://dx.doi.org/10.1139/e99-004.
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Data from the Point Lake area, central Slave craton, suggest an intimate tectonic and paleogeographic association between volcano-sedimentary supracrustal rocks and adjacent gneisses. Granite plutons and orthogneisses yield U-Pb zircon crystallization ages ranging from ca. 3230 to 2818 Ma. Numerous mafic dykes cut the gneisses, and two have been dated by U-Pb zircon geochronometry at 2673 ± 3 and 2690 ± 3 Ma, ages similar to those of volcanic rocks in the Point Lake greenstone belt. Although high-strain zones form the greenstone-gneiss in most places, a structural repetition of granite about 4 km east of Keskarrah Bay is cut by numerous mafic dykes and apparently overlain depositionally(?) by pillow basalt. Mafic volcanic and plutonic rocks from Point Lake have initial (2.7 Ga) εNd values ranging from about +2.2 to -6.3, significantly lower than the depleted mantle at that time. The Nd data suggest either derivation from a more isotopically evolved reservoir, or assimilation of crust similar to the granite gneiss at Point Lake. We infer from the presence of mafic dykes of appropriate age in the basement and the low initial εNd values of some pillow basalts that the volcanic sequence developed on the older granitic crust. The supracrustal rocks may have been deposited in a back-arc basin floored at least in part by attenuated continental material. Closure of the basin, bulk east-west shortening, and sinistral oblique or strike-slip faulting then obscured the original relations between the volcanic and gneissic rocks.
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Ryazantsev, A. V., A. V. Pilitsina, I. A. Novikov, and K. E. Degtyarev. "CARBONIFEROUS 40Ar/39Ar AGE OF THE RARE METAL-ENRICHED RHYOLITES AND IGNIMBRITES IN THE SAKMARA ALLOCHTHON OF THE SOUTHERN URALS, THEIR GEOCHEMICAL FEATURES AND GEODYNAMIC SETTING." Proceedings of higher educational establishments. Geology and Exploration, no. 3 (June 25, 2018): 23–32. http://dx.doi.org/10.32454/0016-7762-2018-3-23-32.
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In the structure of the Sakmara allochthon of the Southern Uralssequence with rhyolites and ignimbrites locally occures. They have Nb-Zr-REE geochemical specialization. This sequence unconformably overlays folded Paleozoic complexes, including the Devonian ones. Rhyolite contains K-feldspar and quartz phenocrysts, K-feldspar glomeroporphyrites and granite xenolith. Geochemical features of the rhyolites show intraplate-originated affinities and A-type granite composition.40Ar/39Ar age of the felsitic matrix of the rhyolites of 303±2 Ma defines the age of the volcanic complex origin. For feldspar phenocrysts the age of 306±3 Ma and 337±3 Ma is obtained. The first value coincides to the matrix age and connected with formation of the volcanic complex. The second value belongs, apparently, to xenogenic material. Obtained age values reflect the evolution of Carboniferous active continental margin magmatism, widespread in different structural zones of the Urals. Rare-metal rhyolites characterize the final late Carboniferous intraplate (rift-related) back-arc magmatism at the active continental margin. Volcanism preceded to a collision-related ophiolitic thrust nappes emplacement.
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Valverde-Vaquero, Pablo, Greg R. Dunning, and Cees R. van Staal. "The Margaree orthogneiss: an Ordovician, peri-Gondwanan, mafic-felsic igneous complex in southwestern Newfoundland." Canadian Journal of Earth Sciences 37, no. 12 (December 1, 2000): 1691–710. http://dx.doi.org/10.1139/e00-053.
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The igneous protoliths of the Margaree orthogneiss intruded the peri-Gondwanan rocks of the Port-aux-Basques Complex, in the southwestern corner of the Hermitage Flexure, prior to regional deformation and metamorphism. Field relationships and UPb geochronology indicate that the Margaree orthogneiss represents a 20 km long, mafic-felsic intrusive complex formed by amphibolite, dioritic orthogneiss, 474+14-4 Ma hornblende-bearing tonalitic orthogneiss with mafic enclaves, 472 ± 2.5 Ma and 465 ± 3 Ma biotite-bearing granitic orthogneiss, and minor ultramafic rocks. Most amphibolite have the chemistry of volcanic-arc tholeiite and are interpreted to be coeval with the intrusion of tonalitic and granitic magma with volcanic-arc geochemical signatures. Locally, mafic magmatism continued after the intrusion of the 465 Ma granite. The Margaree orthogneiss and its country rock were overprinted by upper amphibolite-facies metamorphism and deformation associated with the final closure of the Iapetus Ocean. A late-synkinematic granite dates the late stages of the high-temperature regional deformation at 417+7-4 Ma, while metamorphic titanite (411 ± 2 Ma) is interpreted to date extensive recrystallization under amphibolite-facies conditions as Early Devonian. The Margaree orthogneiss is broadly coeval with the plutons that postdate the Early Ordovician Penobscottian arc passive margin imbrication in central and southern Newfoundland. It also coincides with the extensive late Arenig early Llanvirn back-arc rifting event along the entire peri-Gondwanan margin of the northern Appalachians. The external position of the Port-aux-Basques Complex with respect to the back-arc elements in the Hermitage Flexure, coupled with the rock types and geochemistry of the orthogneiss, suggest formation of the Margaree orthogneiss in an arc and (or) back-arc transitional setting.