Journal articles: 'Granite Geology, Stratigraphic Geochemistry'

1

Chandler, Val W., and Kelley Carlson Malek. "Moving‐window Poisson analysis of gravity and magnetic data from the Penokean orogen, east‐central Minnesota." GEOPHYSICS 56, no. 1 (January 1991): 123–32. http://dx.doi.org/10.1190/1.1442948.

Full text

Abstract:

Analytical correlation of gravity and magnetic data through moving‐window application of Poisson's theorem is useful in studying the complex Precambrian geology of central Minnesota. Linear regression between the two data sets at each window position yields correlation, intercept, and slope parameters that quantitatively describe the relationship between the gravity and magnetic data and, in the case of the slope parameter, are often accurate estimates of magnetizatons‐to‐density ratios (MDR) of anomalous sources. In this study, gridded gravity and magnetic data from a 217.6 × 217.6 km area in central Minnesota were analyzed using a 8.5 × 8.5 km window. The study area includes part of the Early Proterozoic Penokean orogen and an Archean greenstone‐granite terrane of the Superior Province. The parameters derived by the moving‐window analysis show striking relationships to many geologic features, and many of the MDR estimates agree with rock property data. Inversely related gravity and magnetic anomalies are a characteristic trait of the Superior Province, but moving‐window analysis reveals that direct relationships occur locally. In the Penokean fold‐and‐thrust belt, gravity and magnetic highs over the Cuyuna range produce a prominent belt of large MDR estimates, which reflect highly deformed troughs of iron‐formation and other supracrustal rocks. This belt can be traced northeastward to sources that are buried by 3–5 km of Early Proterozoic strata in the Animikie basin. This configuration, in conjunction with recent geologic studies, indicates that the Animikie strata, which may represent foreland basin deposits associated with the Penokean orogen, unconformably overlie parts of the fold‐and‐thrust belt, and that earlier stratigraphic correlations between Cuyuna and Animikie strata are wrong. The results of this study indicate that moving‐window Poisson analysis is useful in the study of Precambrian terranes.

APA, Harvard, Vancouver, ISO, and other styles

2

Dörr, W., P. A. Floyd, and B. E. Leveridge. "U–Pb ages and geochemistry of granite pebbles from the Devonian Menaver Conglomerate, Lizard peninsula: provenance of Rhenohercynian flysch of SW England." Sedimentary Geology 124, no. 1-4 (March 1999): 131–47. http://dx.doi.org/10.1016/s0037-0738(98)00124-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Gardiner, N. J., J. A. Mulder, C. L. Kirkland, T. E. Johnson, and O. Nebel. "Palaeoarchaean TTGs of the Pilbara and Kaapvaal cratons compared; an early Vaalbara supercraton evaluated." South African Journal of Geology 124, no. 1 (March 1, 2021): 37–52. http://dx.doi.org/10.25131/sajg.124.0010.

Full text

Abstract:

Abstract The continental crust that dominates Earth’s oldest cratons comprises Eoarchaean to Palaeoarchaean (4.0 to 3.2 Ga) felsic intrusive rocks of the tonalite-trondhjemite-granodiorite (TTG) series. These are found either within high-grade gneiss terranes, which represent Archaean mid-continental crust, or low-grade granite-greenstone belts, which represent relic Archaean upper continental crust. The Palaeoarchaean East Pilbara Terrane (EPT), Pilbara Craton, Western Australia, and the Barberton Granite-Greenstone Belt (BGGB), Kaapvaal Craton, southern Africa, are two of the best exposed granite-greenstone belts. Their striking geological similarities has led to the postulated existence of Vaalbara, a Neoarchaean-Palaeoproterozoic supercraton. Although their respective TTG domes have been compared in terms of a common petrogenetic origin reflecting a volcanic plateau setting, there are important differences in their age, geochemistry, and isotopic profiles. We present new zircon Hf isotope data from five granite domes of the EPT and compare the geochemical and isotopic record of the Palaeoarchaean TTGs from both cratons. Rare >3.5 Ga EPT evolved rocks have juvenile εHf(t) requiring a chondritic source. In contrast, younger TTG domes developed via 3.5 to 3.4 and 3.3 to 3.2 Ga magmatic supersuites with a greater range of εHf(t) towards more depleted and enriched values, trace element signatures requiring an enriched source, and xenocrystic zircons that reflects a mixed source to the TTGs, which variously assimilates packages of older felsic crust and a more juvenile mafic source. EPT TTG domes are composite and record multiple pulses of magmatism. In comparison, BGGB TTGs are less geochemically enriched than those of the EPT and have different age profiles, hosting coeval magmatic units. Hafnium isotopes suggest a predominantly juvenile source to 3.2 Ga northern Barberton TTGs, limited assimilation of older evolved crust in 3.4 Ga southern Barberton TTGs, but significant assimilation of older (Hadean-Eoarchaean) crust in the ca. 3.6 Ga TTGs of the Ancient Gneiss Complex. The foundation of the EPT is younger than that for the oldest components of the Eastern Kaapvaal. Although the broader prevailing Palaeoarchaean geologic framework in which these two cratons formed may reflect similar a geodynamic regime, the superficial similarities in dome structures and stratigraphy of both cratonic terranes is not reflected in their geochemical and age profiles. Both the similarities and the differences between the crustal histories of the two cratons highlights that they are formed from distinct terranes with different ages and individual evolutionary histories. Vaalbara sensu lato represents typical Palaeoarchaean cratonic crust, not in the sense of a single homogeneous craton, but one as diverse as the continents are today.

APA, Harvard, Vancouver, ISO, and other styles

4

Vovna, G. M., M. A. Mishkin, A. M. Lennikov, R. A. Oktyabrsky, V. F. Polin, Z. G. Badredinov, and T. A. Yasnygina. "Geochemistry, origin, and nature of metamorphic rocks of the Batomga granite-greenstone terrane (Aldan Shield)." Russian Journal of Pacific Geology 8, no. 1 (January 2014): 56–64. http://dx.doi.org/10.1134/s1819714014010059.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Martinez-Landa, Lurdes, Jesús Carrera, Andrés Pérez-Estaún, Paloma Gómez, and Carmen Bajos. "Structural geology and geophysics as a support to build a hydrogeologic model of granite rock." Solid Earth 7, no. 3 (June 1, 2016): 881–95. http://dx.doi.org/10.5194/se-7-881-2016.

Full text

Abstract:

Abstract. A method developed for low-permeability fractured media was applied to understand the hydrogeology of a mine excavated in a granitic pluton. This method includes (1) identifying the main groundwater-conducting features of the medium, such as the mine, dykes, and large fractures, (2) implementing this factors as discrete elements into a three-dimensional numerical model, and (3) calibrating these factors against hydraulic data . A key question is how to identify preferential flow paths in the first step. Here, we propose a combination of several techniques. Structural geology, together with borehole sampling, geophysics, hydrogeochemistry, and local hydraulic tests aided in locating all structures. Integration of these data yielded a conceptual model of the site. A preliminary calibration of the model was performed against short-term (< 1 day) pumping tests, which facilitated the characterization of some of the fractures. The hydraulic properties were then used for other fractures that, according to geophysics and structural geology, belonged to the same families. Model validity was tested by blind prediction of a long-term (4 months) large-scale (1 km) pumping test from the mine, which yielded excellent agreement with the observations. Model results confirmed the sparsely fractured nature of the pluton, which has not been subjected to glacial loading–unloading cycles and whose waters are of Na-HCO3 type.

APA, Harvard, Vancouver, ISO, and other styles

6

Staněk, Martin, and Yves Géraud. "Granite microporosity changes due to fracturing and alteration: secondary mineral phases as proxies for porosity and permeability estimation." Solid Earth 10, no. 1 (February 4, 2019): 251–74. http://dx.doi.org/10.5194/se-10-251-2019.

Full text

Abstract:

Abstract. Several alteration facies of fractured Lipnice granite are studied in detail on borehole samples by means of mercury intrusion porosimetry, polarized and fluorescent light microscopy, and microprobe chemical analyses. The goal is to describe the granite void space geometry in the vicinity of fractures with alteration halos and to link specific geometries with simply detectable parameters to facilitate quick estimation of porosity and permeability based on, for example, drill cuttings. The core of the study is the results of porosity and throat size distribution analyses on 21 specimens representing unique combinations of fracture-related structures within six different alteration facies basically differing in secondary phyllosilicate chemistry and porosity structure. Based on a simple model to calculate permeability from the measured porosities and throat size distributions, the difference in permeability between the fresh granite and the most fractured and altered granite is 5 orders of magnitude. Our observations suggest that the porosity, the size of connections and the proportion of crack porosity increase with fracture density, while precipitation of iron-rich infills as well as of fine-grained secondary phyllosilicates acts in the opposite way. Different styles and intensities of such end-member agents shape the final void space geometry and imply various combinations of storage, transport and retardation capacity for specific structures. This study also shows the possibility to use standard mercury intrusion porosimetry with advanced experimental settings and data treatment to distinguish important differences in void space geometry within a span of a few percent of porosity.

APA, Harvard, Vancouver, ISO, and other styles

7

Janots, Emilie, Alexis Grand'Homme, Matthias Bernet, Damien Guillaume, Edwin Gnos, Marie-Christine Boiron, Magali Rossi, Anne-Magali Seydoux-Guillaume, and Roger De Ascenção Guedes. "Geochronological and thermometric evidence of unusually hot fluids in an Alpine fissure of Lauzière granite (Belledonne, Western Alps)." Solid Earth 10, no. 1 (January 28, 2019): 211–23. http://dx.doi.org/10.5194/se-10-211-2019.

Full text

Abstract:

Abstract. A multi-method investigation into Lauzière granite, located in the external Belledonne massif of the French Alps, reveals unusually hot hydrothermal conditions in vertical open fractures (Alpine-type clefts). The host-rock granite shows sub-vertical mylonitic microstructures and partial retrogression at temperatures of < 400 ∘C during Alpine tectonometamorphism. Novel zircon fission-track (ZFT) data in the granite give ages at 16.3 ± 1.9 and 14.3 ± 1.6 Ma, confirming that Alpine metamorphism was high enough to reset the pre-Alpine cooling ages and that the Lauzière granite had already cooled below 240–280 ∘C and was exhumed to < 10 km at that time. Novel microthermometric data and chemical compositions of fluid inclusions obtained on millimetric monazite and on quartz crystals from the same cleft indicate early precipitation of monazite from a hot fluid at T > 410 ∘C, followed by a main stage of quartz growth at 300–320 ∘C and 1.5–2.2 kbar. Previous Th-Pb dating of cleft monazite at 12.4 ± 0.1 Ma clearly indicates that this hot fluid infiltration took place significantly later than the peak of the Alpine metamorphism. Advective heating due to the hot fluid flow caused resetting of fission tracks in zircon in the cleft hanging wall, with a ZFT age at 10.3 ± 1.0 Ma. The results attest to the highly dynamic fluid pathways, allowing the circulation of deep mid-crustal fluids, 150–250 ∘C hotter than the host rock, which affect the thermal regime only at the wall rock of the Alpine-type cleft. Such advective heating may impact the ZFT data and represent a pitfall for exhumation rate reconstructions in areas affected by hydrothermal fluid flow.

APA, Harvard, Vancouver, ISO, and other styles

8

Nyaban, Christian Emile, Théophile Ndougsa-Mbarga, Marcelin Bikoro-Bi-Alou, Stella Amina Manekeng Tadjouteu, and Stephane Patrick Assembe. "Multi-scale analysis and modelling of aeromagnetic data over the Bétaré-Oya area in eastern Cameroon, for structural evidence investigations." Solid Earth 12, no. 4 (April 6, 2021): 785–800. http://dx.doi.org/10.5194/se-12-785-2021.

Full text

Abstract:

Abstract. This study was carried out in the Lom series in Cameroon, at the border with Central African Republic, located between the latitudes 5∘30′–6∘ N and the longitudes 13∘30′–14∘45′ E. A multi-scale analysis of aeromagnetic data combining tilt derivative, Euler deconvolution, upward continuation, and 2.75D modelling was used. The following conclusions were drawn. (1) Several major families of faults were mapped. Their orientations are ENE–WSW, E–W, NW–SE, and N–S with a NE–SW prevalence. The latter are predominantly sub-vertical with NW and SW dips and appear to be prospective for future mining investigations. (2) The evidence of compression, folding, and shearing axis was concluded from superposition of null contours of the tilt derivative and Euler deconvolution. The principal evidence of the local tectonics was due to several deformation episodes (D1, D2, and D4) associated with NE–SW, E–W, and NW–SE events, respectively. (3) Depths of interpreted faults range from 1000 to 3400 m. (4) Several linear structures correlating with known mylonitic veins were identified. These are associated with the Lom faults and represent the contacts between the Lom series and the granito-gneissic rocks; we concluded the intense folding was caused by senestral and dextral NE–SW and NW–SE stumps. (5) We propose a structural model of the top of the crust (schists, gneisses, granites) that delineates principal intrusions (porphyroid granite, garnet gneiss, syenites, micaschists, graphite, and garnet gneiss) responsible for the observed anomalies. The 2.75D modelling revealed many faults with a depth greater than 1200 m and confirmed the observations from reduced-to-Equator total magnetic intensity (RTE-TMI), tilt derivative, and Euler deconvolution. (6) We developed a lithologic profile of the Bétaré-Oya basin.

APA, Harvard, Vancouver, ISO, and other styles

9

Nevolin, P. L., V. P. Utkin, and A. N. Mitrokhin. "The Tafuinsky granite massif, southern Primorye region: The structures and geodynamics of longitudinal compression." Russian Journal of Pacific Geology 4, no. 4 (August 2010): 331–46. http://dx.doi.org/10.1134/s1819714010040056.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Vladimirov, A. G., P. A. Balykin, Phan Luu Anh, N. N. Kruk, Ngo Thi Phuong, A. V. Travin, Tran Trong Hoa, et al. "The Khao Que-Tam Tao gabbro-granite massif, Northern Vietnam: A petrological indicator of the Emeishan plume." Russian Journal of Pacific Geology 6, no. 5 (September 2012): 395–411. http://dx.doi.org/10.1134/s1819714012050065.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Selvadurai, Patrick, Paul A. Selvadurai, and Morteza Nejati. "A multi-phasic approach for estimating the Biot coefficient for Grimsel granite." Solid Earth 10, no. 6 (November 15, 2019): 2001–14. http://dx.doi.org/10.5194/se-10-2001-2019.

Full text

Abstract:

Abstract. This paper presents an alternative approach for estimating the Biot coefficient for the Grimsel granite, which appeals to the multi-phasic mineralogical composition of the rock. The modelling considers the transversely isotropic nature of the rock that is evident from both the visual appearance of the rock and determined from mechanical testing. Conventionally, estimation of the compressibility of the solid material is performed by fluid saturation of the pore space and pressurization. The drawback of this approach in terms of complicated experimentation and influences of the unsaturated pore space is alleviated by adopting the methods for estimating the solid material compressibility using developments in theories of multi-phase materials. The results of the proposed approach are compared with estimates available in the literature.

APA, Harvard, Vancouver, ISO, and other styles

12

Polzunenkov, G. O. "Evaluation of P–T and fO2 Conditions of Crystallization of Monzonitic Rocks of the Velitkenay Granite–Migmatite Massif (Arctic Chukotka) Based on Mineral Thermobaro- and Oxybarometry." Russian Journal of Pacific Geology 12, no. 5 (September 2018): 429–42. http://dx.doi.org/10.1134/s1819714018050081.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Pereira, Manuel Francisco, Cristina Gama, Ícaro Dias da Silva, José Brandão Silva, Mandy Hofmann, Ulf Linnemann, and Andreas Gärtner. "Chronostratigraphic framework and provenance of the Ossa-Morena Zone Carboniferous basins (southwest Iberia)." Solid Earth 11, no. 4 (July 9, 2020): 1291–312. http://dx.doi.org/10.5194/se-11-1291-2020.

Full text

Abstract:

Abstract. Carboniferous siliciclastic and silicic magmatic rocks from the Santa Susana–São Cristovão and Cabrela regions contain valuable information regarding the timing of synorogenic processes in SW Iberia. In this region of the Ossa-Morena Zone (OMZ), late Carboniferous terrigenous strata (i.e., the Santa Susana Formation) unconformably overlie early Carboniferous marine siliciclastic deposits alternating with volcanic rocks (i.e., the Toca da Moura volcano-sedimentary complex). Lying below this intra-Carboniferous unconformity, the Toca da Moura volcano-sedimentary complex is intruded and overlain by the Baleizão porphyry. Original sensitive high-resolution ion microprobe (SHRIMP) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb zircon are presented in this paper, providing chronostratigraphic and provenance constraints since available geochronological information is scarce and only biostratigraphic ages are currently available for the Santa Susana–São Cristovão region. Our findings and the currently available detrital zircon ages from Paleozoic terranes of SW Iberia (Pulo do Lobo Zone – PLZ – South Portuguese Zone – SPZ – and OMZ) were jointly analyzed using the K–S test and multidimensional scaling (MDS) diagrams to investigate provenance. The marine deposition is constrained to the age range of ca. 335–331 Ma (Visean) by new U–Pb data for silicic tuffs from the Toca da Moura and Cabrela volcano-sedimentary complexes. The Baleizão porphyry, intrusive in the Toca da Moura volcano-sedimentary complex, yielded a crystallization age of ca. 318 Ma (Bashkirian), providing the minimum age for the overlying intra-Carboniferous unconformity. A comparison of detrital zircon populations from siliciclastic rocks of the Cabrela and Toca de Moura volcano-sedimentary complexes of the OMZ suggests that they are derived from distinct sources more closely associated with the SPZ and PLZ than the OMZ. Above the intra-Carboniferous unconformity, the Santa Susana Formation is the result of the recycling of distinct sources located either on the Laurussian side (SPZ and PLZ) or Gondwanan side (OMZ) of the Rheic suture zone. The best estimate of the crystallization age of a granite cobble which was found in a conglomerate from the Santa Susana Formation yielded ca. 303 Ma (Kasimovian–Gzhelian), representing the maximum depositional age for the terrestrial strata. The intra-Carboniferous unconformity seems to represent a stratigraphic gap of approximately 12–14 Myr, providing evidence of the rapid post-accretion and collision uplift of the Variscan orogenic belt in SW Iberia (i.e., the OMZ, PLZ, and SPZ).

APA, Harvard, Vancouver, ISO, and other styles

14

Larin, A. M. "Rapakivi granites in the geological history of the earth. Part 1, magmatic associations with rapakivi granites: Age, geochemistry, and tectonic setting." Stratigraphy and Geological Correlation 17, no. 3 (June 2009): 235–58. http://dx.doi.org/10.1134/s0869593809030010.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Mężyk, Miłosz, Michał Malinowski, and Stanisław Mazur. "Imaging the East European Craton margin in northern Poland using extended correlation processing of regional seismic reflection profiles." Solid Earth 10, no. 3 (May 21, 2019): 683–96. http://dx.doi.org/10.5194/se-10-683-2019.

Full text

Abstract:

Abstract. In NE Poland, Eastern European Craton (EEC) crust of Fennoscandian affinity is concealed under a Phanerozoic platform cover and penetrated by sparse, deep research wells. Most of the inferences regarding its structure rely on geophysical data. Until recently, this area was covered only by the wide-angle reflection and refraction (WARR) profiles, which show a relatively simple crustal structure with a typical three-layer cratonic crust. ION Geophysical PolandSPAN™ regional seismic programme data, acquired over the marginal part of the EEC in Poland, offered a unique opportunity to derive a detailed image of the deeper crust. Here, we apply extended correlation processing to a subset (∼950 km) of the PolandSPAN™ dataset located in NE Poland, which enabled us to extend the nominal record length of the acquired data from 12 to 22 s (∼60 km of depth). Our new processing revealed reflectivity patterns, which we primarily associate with the Paleoproterozoic crust formed during the Svekofennian (Svekobaltic) orogeny, that are similar to those observed along the BABEL and FIRE profiles in the Baltic Sea and Finland, respectively. We propose a mid- to lower-crustal, orogeny-normal lateral flow model to explain the occurrence of two sets of structures that can be collectively interpreted as kilometre-scale S–C′ shear zones. The structures define a penetrative deformation fabric invoking ductile extension of hot orogenic crust in a convergent setting. Localized reactivation of these structures provided conduits for subsequent emplacement of gabbroic magma that produced a Mesoproterozoic anorthosite–mangerite–charnockite–granite (AMCG) suite in NE Poland. Delamination of thickened orogenic lithosphere may have accounted for magmatic underplating and fractionation into the AMCG plutons. We also found sub-Moho dipping mantle reflectivity, which we tentatively explain as a signature of the crustal accretion during the Svekofennian orogeny. Later tectonic phases (e.g. Ediacaran rifting, Caledonian orogeny) did not leave a clear signature in the deeper crust; however, some of the subhorizontal reflectors below the basement, observed in the vicinity of the AMCG Mazury complex, can be alternatively linked with lower Carboniferous magmatism.

APA, Harvard, Vancouver, ISO, and other styles

16

Lindh, Anders. "The geochemistry of the Sorvik granite—a TIB-1 granite." GFF 130, no. 3 (September 2008): 139–52. http://dx.doi.org/10.1080/11035890809453229.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Lindh, Anders. "The geochemistry of the Sorvik granite — a TIB-1 granite." GFF 130, no. 3 (September 1, 2008): 139–52. http://dx.doi.org/10.1080/11035890801303139.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Spruzeniece, L., and S. Piazolo. "Strain localization in brittle–ductile shear zones: fluid-abundant vs. fluid-limited conditions (an example from Wyangala area, Australia)." Solid Earth 6, no. 3 (July 24, 2015): 881–901. http://dx.doi.org/10.5194/se-6-881-2015.

Full text

Abstract:

Abstract. This study focuses on physiochemical processes occurring in a brittle–ductile shear zone at both fluid-present and fluid-limited conditions. In the studied shear zone (Wyangala, SE Australia), a coarse-grained two-feldspar–quartz–biotite granite is transformed into a medium-grained orthogneiss at the shear zone margins and a fine-grained quartz–muscovite phyllonite in the central parts. The orthogneiss displays cataclasis of feldspar and crystal-plastic deformation of quartz. Quartz accommodates most of the deformation and is extensively recrystallized, showing distinct crystallographic preferred orientation (CPO). Feldspar-to-muscovite, biotite-to-muscovite and albitization reactions occur locally at porphyroclasts' fracture surfaces and margins. However, the bulk rock composition shows very little change in respect to the wall rock composition. In contrast, in the shear zone centre quartz occurs as large, weakly deformed porphyroclasts in sizes similar to that in the wall rock, suggesting that it has undergone little deformation. Feldspars and biotite are almost completely reacted to muscovite, which is arranged in a fine-grained interconnected matrix. Muscovite-rich layers contain significant amounts of fine-grained intermixed quartz with random CPO. These domains are interpreted to have accommodated most of the strain. Bulk rock chemistry data show a significant increase in SiO2 and depletion in NaO content compared to the wall rock composition. We suggest that the high- and low-strain microstructures in the shear zone represent markedly different scenarios and cannot be interpreted as a simple sequential development with respect to strain. Instead, we propose that the microstructural and mineralogical changes in the shear zone centre arise from a local metasomatic alteration around a brittle precursor. When the weaker fine-grained microstructure is established, the further flow is controlled by transient porosity created at (i) grain boundaries in fine-grained areas deforming by grain boundary sliding (GBS) and (ii) transient dilatancy sites at porphyroclast–matrix boundaries. Here a growth of secondary quartz occurs from incoming fluid, resulting in significant changes in bulk composition and eventually rheological hardening due to the precipitation-related increase in the mode and grain size of quartz. In contrast, within the shear zone margins the amount of fluid influx and associated reactions is limited; here deformation mainly proceeds by dynamic recrystallization of the igneous quartz grains. The studied shear zone exemplifies the role of syn-deformational fluids and fluid-induced reactions on the dominance of deformation processes and subsequent contrasting rheological behaviour at micron to metre scale.

APA, Harvard, Vancouver, ISO, and other styles

19

Nickschick, Tobias, Christina Flechsig, Jan Mrlina, Frank Oppermann, Felix Löbig, and Thomas Günther. "Large-scale electrical resistivity tomography in the Cheb Basin (Eger Rift) at an International Continental Drilling Program (ICDP) monitoring site to image fluid-related structures." Solid Earth 10, no. 6 (November 14, 2019): 1951–69. http://dx.doi.org/10.5194/se-10-1951-2019.

Full text

Abstract:

Abstract. The Cheb Basin, a region of ongoing swarm earthquake activity in the western Czech Republic, is characterized by intense carbon dioxide degassing along two known fault zones – the N–S-striking Počatky–Plesná fault zone (PPZ) and the NW–SE-striking Mariánské Lázně fault zone (MLF). The fluid pathways for the ascending CO2 of mantle origin are one of the subjects of the International Continental Scientific Drilling Program (ICDP) project “Drilling the Eger Rift” in which several geophysical surveys are currently being carried out in this area to image the topmost hundreds of meters to assess the structural situation, as existing boreholes are not sufficiently deep to characterize it. As electrical resistivity is a sensitive parameter to the presence of conductive rock fractions as liquid fluids, clay minerals, and also metallic components, a large-scale dipole–dipole experiment using a special type of electric resistivity tomography (ERT) was carried out in June 2017 in order to image fluid-relevant structures. We used permanently placed data loggers for voltage measurements in conjunction with moving high-power current sources to generate sufficiently strong signals that could be detected all along the 6.5 km long profile with 100 and 150 m dipole spacings. After extensive processing of time series for voltage and current using a selective stacking approach, the pseudo-section is inverted, which results in a resistivity model that allows for reliable interpretations depths of up than 1000 m. The subsurface resistivity image reveals the deposition and transition of the overlying Neogene Vildštejn and Cypris formations, but it also shows a very conductive basement of phyllites and granites that can be attributed to high salinity or rock alteration by these fluids in the tectonically stressed basement. Distinct, narrow pathways for CO2 ascent are not observed with this kind of setup, which hints at wide degassing structures over several kilometers within the crust instead. We also observed gravity and GPS data along this profile in order to constrain ERT results. A gravity anomaly of ca. −9 mGal marks the deepest part of the Cheb Basin where the ERT profile indicates a large accumulation of conductive rocks, indicating a very deep weathering or alteration of the phyllitic basement due to the ascent of magmatic fluids such as CO2. We propose a conceptual model in which certain lithologic layers act as caps for the ascending fluids based on stratigraphic records and our results from this experiment, providing a basis for future drillings in the area aimed at studying and monitoring fluids.

APA, Harvard, Vancouver, ISO, and other styles

20

Jelsma, H. A., R. W. Nesbitt, and C. M. Fanning. "Exploring our current understanding of the geological evolution and mineral endowment of the Zimbabwe Craton." South African Journal of Geology 124, no. 1 (March 1, 2021): 279–310. http://dx.doi.org/10.25131/sajg.124.0020.

Full text

Abstract:

Abstract A.M. Macgregor (1888-1961) is remembered for his enormous contribution to geology. His maps changed the course of geological thinking in southern Africa. Following in his footsteps we examine aspects of our current understanding of the geological evolution of the Zimbabwe Craton and, using new SHRIMP U-Pb ages of zircons from felsic volcanic and plutonic rocks from northern Zimbabwe and unpublished data related to the seminal paper by Wilson et al. (1995), a synthesis is proposed for the formation of the Neoarchaean greenstones. The data suggest marked differences (lithostratigraphy, geochemistry and isotope data, mineral endowment and deformational history), between Eastern and Western Successions, which indicate fundamentally different geodynamic environments of formation. The Eastern Succession within the southcentral part of the craton, largely unchanged in terms of stratigraphy, is reminiscent of a rift-type setting with the Manjeri Formation sediments and overlying ca. 2 745 Ma Reliance Formation komatiite magmatism being important time markers. In contrast, the Western Succession is reminiscent of a convergent margin subduction-accretion system with bimodal mafic-felsic volcanism and accompanying sedimentation constrained to between 2 715 and 2 683 Ma. At ca. 2 670 Ma, a tectonic switch likely marks the onset of deposition of Shamvaian felsic volcanism and sedimentation. The Shamvaian resembles pull-apart basin successions and is dominated by deposition of a coarse clastic sedimentary succession, with deposition likely constrained to between 2 672 and 2 647 Ma. The late tectonic emplacement of small, juvenile multiphase stocks, ranging in composition from gabbroic to granodioritic was associated with gold ± molybdenum mineralisation. Their emplacement at 2 647 Ma provides an upper age limit to the timespan of Shamvaian deposition. Amongst the youngest granites are the extensive, largely tabular late- to post-tectonic ca. 2 620 to 2 600 Ma Chilimanzi Suite granites. These granites are characterised by evolved isotopic systems and have been related to crustal relaxation and anatexis following deformation events. After their emplacement, the Zimbabwe Craton cooled and stabilised, with further deformation partitioned into lower-grade, strike-slip shear zones, and at ca. 2 575 Ma the craton was cut by the Great Dyke, its satellite dykes and related fractures.

APA, Harvard, Vancouver, ISO, and other styles

21

Hutchinson, Peter J., and Maggie H. Tsai. "Stratigraphic Analysis with Refraction Tomography." Environmental and Engineering Geoscience 25, no. 3 (August 2, 2019): 245–54. http://dx.doi.org/10.2113/eeg-2127.

Full text

Abstract:

ABSTRACT Near-surface seismic refraction tomography imaged the basal contact of the Upper Cambrian silica-rich Mount Simon Formation with that of the underlying Precambrian granite in central Wisconsin. The discrimination between the Mount Simon and underlying non-conformable contact with Precambrian rocks was based upon a p-wave velocity of 1,700 m/s. Refraction tomography imaged deep, broad tidal channels within the Mount Simon consistent with the inference that Mount Simon was deposited in a high-energy near-shore, probably fluvial environment. The Mount Simon is an arenite that has high commercial value.

APA, Harvard, Vancouver, ISO, and other styles

22

RYAN, PAUL D., and N. JACK SOPER. "Modelling anatexis in intra-cratonic rift basins: an example from the Neoproterozoic rocks of the Scottish Highlands." Geological Magazine 138, no. 5 (September 2001): 577–88. http://dx.doi.org/10.1017/s0016756801005696.

Full text

Abstract:

The Neoproterozoic metasediments of northwestern Scotland were deformed during the 470 Ma Grampian orogeny. Their pre-Ordovician history has proved difficult to elucidate, due to conflicting evidence. While the stratigraphic record indicates deposition in intracontinental rift basins associated with the break-up of Rodinia, isotopic dates in the range 870–780 Ma from granite gneiss, early pegmatites and metamorphic garnets have been attributed to a Neoproterozoic ‘Knoydartian’ orogeny. Stratigraphic evidence for this orogeny is lacking, and it is not represented elsewhere on the Laurentian margin. An alternative interpretation is that much of the Knoydartian history can be related to extensional, not collisional processes. Specifically, it has been proposed that the 870 Ma West Highland granite gneiss that is intruded into the Moine rocks of northwestern Scotland is not the product of synorogenic anatexis but represents a suite of granite sheets that were generated during extensional rifting and were subsequently deformed and gneissified during the Grampian orogeny. This contribution presents numerical models of extension-related anatexis to test this hypothesis.We first develop a methodology to estimate stretch values and the duration of extension and thermal subsidence for the Moine rift basins. A thermal model is then constructed for these basins using transient finite element techniques. This model shows that lithospheric extension sufficient to produce major rift basins, even if they are filled with feldspathic sediment with Neoproterozoic heat production characteristics, will not lead to crustal anatexis. However, a regional suite of mafic dykes in the more easterly (Loch Eil) Moine suggests that stretching led to decompression melting of the mantle. We model the effect of advecting heat into the extending lithosphere by the introduction of a modest volume of basaltic magma, and show that substantial granitic melt can be generated in the basement beneath the basin. The amount of anatexis varies with the locus of basalt intrusion. Some 30% more granite is generated by dykes emplaced along basin-bounding faults than by either dykes emplaced beneath the centre of the basin, or by underplating sills. The spatial distributions of the West Highland gneiss and of the mafic suite are compatible with this finding. There is clear field evidence that the protolith of the West Highland gneiss consisted of a suite of pre-tectonic granite sheets, and our modelling demonstrates that they could have been generated during the later stages of extensional rifting and Moine sedimentation.

APA, Harvard, Vancouver, ISO, and other styles

23

Orajaka, I. P. "Geochemistry of Kaffo Valley albite-riebeckite-granite, Liruei Granite ring-complex, northern Nigeria." Chemical Geology 56, no. 1-2 (July 1986): 85–92. http://dx.doi.org/10.1016/0009-2541(86)90112-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Hay, William W. "Automated stratigraphic correlation." Marine Geology 118, no. 3-4 (May 1994): 335–36. http://dx.doi.org/10.1016/0025-3227(94)90093-0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Swain, F. M. "Quantitative stratigraphic correlation." Marine Geology 65, no. 3-4 (June 1985): 354–55. http://dx.doi.org/10.1016/0025-3227(85)90067-2.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

RAO, V. "The Ghingee Granite, Tamil Nadu, South India: Geochemistry and Petrogenesis." Gondwana Research 2, no. 1 (January 1999): 117–26. http://dx.doi.org/10.1016/s1342-937x(05)70132-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Singh, Santosh K., and Satyendra Singh. "Geochemistry and Tungsten Metallogeny of the Balda Granite, Rajasthan, India." Gondwana Research 4, no. 3 (July 2001): 487–95. http://dx.doi.org/10.1016/s1342-937x(05)70348-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Azzouni-Sekkal, Abla, and Jean Boissonnas. "Geochemistry of the Tioueine Pan-African granite complex (Hoggar, Algeria)." Geological Journal 22, S2 (1987): 213–24. http://dx.doi.org/10.1002/gj.3350220616.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Hu, Fei, Wei Huang, Zeli Yang, Simon A. Wilde, Harald Furnes, Mansheng Luo, and Kexin Zhang. "Geochemistry and zircon U–Pb–Hf isotopes of the Mante Aobao granite porphyry at East Ujimqin Banner, Inner Mongolia: implications for petrogenesis and tectonic setting." Geological Magazine 157, no. 7 (November 18, 2019): 1068–86. http://dx.doi.org/10.1017/s0016756819001274.

Full text

Abstract:

AbstractWe present detailed petrography, geochemistry and zircon U–Pb–Hf isotopes of the Mante Aobao granite porphyry in East Ujimqin Banner, Inner Mongolia, with the aim of determining its age and petrogenesis, important for understanding the early Palaeozoic tectonic evolution of the Xing’an–Mongolian Orogenic Belt. The Mante Aobao granite porphyry consists of plagioclase, quartz and minor biotite, but without amphibole. Zircon U–Pb analyses yield ages of 450 ± 1 Ma and 445 ± 2 Ma for the granite porphyry, indicating that it formed during Late Ordovician time. The granite porphyry is metaluminous to slightly peraluminous (aluminous saturation index A/CNK = 0.98–1.11) with high SiO2, K2O and Na2O concentrations and differentiation index (DI = 85–90). Chondrite-normalized rare earth element (REE) patterns display enrichment of light REEs (LREEs) with high ratios of (La/Yb)N and negative Eu anomalies. In the mantle-normalized multi-element variation diagrams, all samples are characterized by depletions of high-field-strength elements (HFSEs; Nb, Ta and Ti) and enrichments of large-ion lithophiles (LILEs; Rb, Th, U and K). These geochemical features indicate that the granite porphyry is a highly fractionated I-type granite and formed in a subduction-related setting. Zircon grains have positive εHf(t) values of +9.2 to +11.2, and TDM2(Hf) ages of 691–821 Ma, suggesting that the granite porphyry was generated by partial melting of Neoproterozoic juvenile crust with involvement of fractional crystallization during magmatic evolution. It is likely that underplating of mantle-derived magmas during Late Ordovician time provided the necessary heat to partially melt this juvenile crust. Combined with the regional geological data, we infer that the Mante Aobao granite porphyry was emplaced in an active continental margin setting that was probably related to the northwards subduction of the Paleo-Asian Plate beneath the South Mongolian Terrane along the Sonid Zuoqi–Xilinhot axis.

APA, Harvard, Vancouver, ISO, and other styles

30

Ranta, Jukka-Pekka, Eero Hanski, Holly Stein, Matthew Goode, Timo Mäki, and Atte Taivalkoski. "Kivilompolo Mo mineralization in the Peräpohja belt revisited: Trace element geochemistry and Re-Os dating of molybdenite." Bulletin of the Geological Society of Finland 92, no. 2 (December 15, 2020): 131–50. http://dx.doi.org/10.17741/bgsf/92.2.004.

Full text

Abstract:

The Kivilompolo molybdenite occurrence is located in the northern part of the Peräpoh jabelt, within the lithodemic Ylitornio nappe complex. It is hosted within a deformed porphyritic granite belonging to the pre-orogenic 1.99 Ga Kierovaara suite. The minerali-zation occurs mostly as coarse-grained molybdenite flakes in boudinaged quartz veins, with minor chalcopyrite, pyrite, magnetite, and ilmenite. In this study, we report new geochemical data from the host-rock granite and Re-Os dating results of molybdenite from the mineralization. For the whole-rock geochemistry, the mineralized granite is similar to the Kierovaara suite granites analyzed in previous studies. Also, the ca. 2.0 Ga Re-Os age for molybdenite is equal, within error, to the U-Pb zircon age of the Kierovaara suite granite. In addition, similar molybdenite and uraninite ages have been reported from the Rompas-Rajapalot Au-Co occurrence located 30 km NE of Kivilompolo. We propose that the magmatism at around 2.0 Ga ago initiated the hydrothermal circulation that was responsible for the formation of the molybdenite mineralization at Kivilompolo and the primary uranium mineralization associated with the Rompas-Rajapalot Au-Co occurrence or at least, the magmas provided heating, and in addition potentially saline magmatic fluids and metals from a large, cooling magmatic-hydrothermal system.

APA, Harvard, Vancouver, ISO, and other styles

31

Wilkin, Richard T., and Theodore J. Bornhorst. "Geology and geochemistry of granitoid rocks in the Archean Northern complex, Michigan, U.S.A." Canadian Journal of Earth Sciences 29, no. 8 (August 1, 1992): 1674–85. http://dx.doi.org/10.1139/e92-132.

Full text

Abstract:

The Northern complex, located in the Upper Peninsula of Michigan, is an Archean greenstone–granite terrane that lies at the southern margin of the Superior Province. The origin of the plutonic suites in the Northern complex can be interpreted within a plate tectonic model proposed for the Superior Province and related to northward-directed subduction and subsequent collision along the Great Lakes tectonic zone. The following plutonic suites are recognized based on intrusive relationships, as well as textural and compositional differences: (i) gneissic tonalite suite; (ii) foliated tonalite suite; (iii) trondhjemite–granite suite; (iv) hornblendite–syenite suite; and (v) late granite dike suite. Rocks in the gneissic and foliated tonalite suites have lithologic and geochemical characteristics typical of Archean trondhjemite–tonalite–granodiorite assemblages exposed elsewhere in the Superior Province. They were emplaced during a primary deformation event and are interpreted to represent partial melts that formed during north-directed subduction of oceanic crust just prior to collision along the Great Lakes tectonic zone. During a second deformation event, stocks and plugs of the trondhjemite–granite suite, derived by intracrustal melting of amphibolite associated with collision and tectonic thickening, intruded both interior and exterior to a preexisting volcanic portion of the Northern complex. The hornblendite–syenite suite, composed of hornblende-rich syenites to monzodiorites with geochemical features that include high Mg numbers, and elevated Cr and Ni content, was derived from partial melting of the mantle during collision along the Great Lakes tectonic zone. The late granite dike suite, comprising late-stage, muscovite- and biotite-bearing quartz – alkali feldspar pegmatite and finer grained granitic lithologies, represents the last magmatic event in the Northern complex emplaced after collision.

APA, Harvard, Vancouver, ISO, and other styles

32

SWEETMAN, T. M. "The geochemistry of the Blackstairs Unit of the Leinster Granite, Ireland." Journal of the Geological Society 144, no. 6 (November 1987): 971–84. http://dx.doi.org/10.1144/gsjgs.144.6.0971.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

SIMPSON, A. L., and A. F. COOPER. "Geochemistry of the Darwin Glacier region granitoids, southern Victoria Land." Antarctic Science 14, no. 4 (December 2002): 425–26. http://dx.doi.org/10.1017/s0954102002000226.

Full text

Abstract:

The Darwin Glacier region is located between the Carlyon and Darwin glaciers in southern Victoria Land, Antarctica (Fig. 1). Previous work on Ross Orogeny granitoids of the Darwin Glacier region is mutually conflicting. Haskell et al. (1965) mapped three plutons, the Carlyon Granodiorite, Mount Rich Granite and Hope Granite, Felder & Faure (1990) did not recognise the Hope Granite, and Encarnación & Grunow (1996) interpreted the entire area as underlain by a single intrusion, the Brown Hills pluton. Fieldwork during the 2000 field season and subsequent geochemical and geochronological analysis described here indicates the presence of three distinctive granitic suites, emplaced during Cambrian times. These include the Foggy Dog Granite (FDG) suite, the Darwin calcic suite and the Cooper Granodiorite.

APA, Harvard, Vancouver, ISO, and other styles

34

Sennikov, N. V., O. T. Obut, N. G. Izokh, R. A. Khabibulina, T. A. Shcherbanenko, and T. P. Kipriyanova. "THE REGIONAL STRATIGRAPHIC CHART FOR THE ORDOVICIAN OF TYVA (NEW VERSION)." Geology and mineral resources of Siberia, no. 9c (2021): 37–60. http://dx.doi.org/10.20403/2078-0575-2021-9c-37-60.

Full text

Abstract:

A new version of the Regional stratigraphic chart for the Ordovician of Tyva and explanatory note, compiled in accordance with the Russian Stratigraphic Code, introduce changes, additional and specified data in comparison with the previous (third edition) chart. The Interdepartmental stratigraphic meeting held at Novosibirsk in 1979 approved the old version of the chart and later it was validated by the USSR Interdepartmental Stratigraphic Committee as the official stratigraphic base for all types of the regional geologic activities. Since 1979 meeting, the stages of the Ordovician chart were changed. Volumes of the lower, middle and upper series were also changed. For the present version of the stratigraphic chart the new standard Ordovician stages were used.

APA, Harvard, Vancouver, ISO, and other styles

35

Sennikov, N. V., O. T. Obut, N. G. Izokh, and T. P. Kipriyanova. "THE REGIONAL STRATIGRAPHIC CHART FOR THE ORDOVICIAN OF THE WESTERN SAYAN (NEW VERSION)." Geology and mineral resources of Siberia, no. 9c (2021): 4–14. http://dx.doi.org/10.20403/2078-0575-2021-9c-4-14.

Full text

Abstract:

A new version of the Regional stratigraphic chart for the Ordovician of the Western Sayan and explanatory note, compiled in accordance with the Russian Stratigraphic Code 2006, introduce changes, additional and specified data in comparison with the previous (first edition) chart. The Interdepartmental stratigraphic meeting held at Novosibirsk in 1964 approved the old version of the chart and later it was validated by the USSR Interdepartmental Stratigraphic Committee as the official stratigraphic base for all types of the regional geologic activities. Since 1964 meeting, the stages of the Ordovician chart were changed. Thus, instead of the traditional British stages (Tremadocian, Arenigian, Llanvirnian, Llandeilian, Caradocian, Ashgillian) the following units were adopted by the International Stratigraphic Chart – Tremadocian, Floian, Dapingian, Darriwilian, Sandbian, Katian, Hirnantian. Volumes of the lower, middle and upper series were also changed. For the present version of the stratigraphic chart the new standard Ordovician stages were used.

APA, Harvard, Vancouver, ISO, and other styles

36

Beskin, S. M., and Yu B. Marin. "Granite Systems with Rare-Metal Pegmatites." Geology of Ore Deposits 62, no. 7 (December 2020): 554–63. http://dx.doi.org/10.1134/s107570152007003x.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Sennikov, N. V., O. T. Obut, N. G. Izokh, R. A. Khabibulina, and T. P. Kipriyanova. "THE REGIONAL STRATIGRAPHIC CHART FOR THE SILURIAN OF THE WESTERN SAYAN (NEW VERSION)." Geology and mineral resources of Siberia, no. 9c (2021): 15–36. http://dx.doi.org/10.20403/2078-0575-2021-9c-15-36.

Full text

Abstract:

A new version of the Regional stratigraphic chart for the Silurian of the Western Sayan and explanatory note, compiled in accordance with the Russian Stratigraphic Code, introduce changes, additional and specified data in comparison with the previous (first edition) chart. The Interdepartmental stratigraphic meeting held at Novosibirsk in 1964 approved the old version of the chart and later it was validated by the USSR Interdepartmental Stratigraphic Committee as the official stratigraphic base for all types of the regional geologic activities. Since 1964 meeting, the stages of the Silurian chart were changed. Thus, former stages Llandovery, Wenlock, Ludlow and Pridoli become series. New stages Rhuddanian, Aeronian, Telychian, Sheinwoodian, Homerian, Gorstian and Ludfordian were adopted for the three former series. For the presented stratigraphic chart the new standard Silurian stages were used.

APA, Harvard, Vancouver, ISO, and other styles

38

Brewer, Aaron, Fang-Zhen Teng, and David Dethier. "Magnesium isotope fractionation during granite weathering." Chemical Geology 501 (November 2018): 95–103. http://dx.doi.org/10.1016/j.chemgeo.2018.10.013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Moyen, Jean-François, and Gordon R. Watt. "Pre-Nagssugtoqidian crustal evolution in West Greenland: geology, geochemistry and deformation of supracrustal and granitic rocks north-east of Kangaatsiaq." Geological Survey of Denmark and Greenland (GEUS) Bulletin 11 (December 5, 2006): 33–52. http://dx.doi.org/10.34194/geusb.v11.4915.

Full text

Abstract:

The area north-east of Kangaatsiaq features polyphase grey orthogneisses, supracrustal rocks and Kangaatsiaq granite exposed within a WSW–ENE-trending synform. The supracrustal rocks are comprised of garnet-bearing metapelites, layered amphibolites and layered, likewise grey biotite paragneisses. Their association and geochemical compositions are consistent with a metamorphosed volcano-sedimentary basin (containing both tholeiitic and calc-alkali lavas) and is similar to other Archaean greenstone belts. The Kangaatsiaq granite forms a 15 × 3 km flat, subconcordant body of deformed, pink, porphyritic granite occupying the core of the supracrustal synform, and is demonstrably intrusive into the amphibolites. The granite displays a pronounced linear fabric (L or L > S). The post-granite deformation developed under lower amphibolite facies conditions (400 ± 50°C), and is characterised by a regular, NE–SW-trending subhorizontal lineation and an associated irregular foliation, whose poles define a great circle; together they are indicative of highly constrictional strain. The existence of a pre-granite event is attested by early isoclinal folds and a foliation within the amphibolites that is not present in the granite, and by the fact that the granite cuts earlier structures in the supracrustal rocks. This early event, preserved only in quartz-free lithologies, resulted in high-temperature fabrics being developed under upper amphibolite to granulite facies conditions.

APA, Harvard, Vancouver, ISO, and other styles

40

Li, Jin-Xiang, Wei-Ming Fan, Li-Yun Zhang, Lin Ding, Ya-Hui Yue, Jing Xie, Fu-Long Cai, Qiu-Yun Quan, and Kyaing Sein. "Biotite geochemistry deciphers magma evolution of Sn-bearing granite, southern Myanmar." Ore Geology Reviews 121 (June 2020): 103565. http://dx.doi.org/10.1016/j.oregeorev.2020.103565.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Jenkins, D. G., R. D. Beckinsale, D. Q. Bowen, J. A. Evans, G. T. George, N. B. W. Harris, and I. G. Meighan. "The origin of granite erratics in the Pleistocene Patella beach, Gower, South Wales." Geological Magazine 122, no. 3 (May 1985): 297–302. http://dx.doi.org/10.1017/s0016756800031514.

Full text

Abstract:

AbstractRare pebbles of granite have been discovered in the raised Patella beach at Butterslade, Gower, South Wales. Their petrography, trace element geochemistry and the Rb/Sr whole rock age of 55 ± 5 Ma confirm that they are derived from the Lundy granite which is about 49 km to the southwest of Gower. Amino acid analyses of fossil gastropods in the Patella beach have provided an age of 210000 years. Various hypotheses of transportation of pebbles from Lundy and Pembrokeshire to Butterslade are considered. Erratics from Pembrokeshire were probably transported by Pleistocene ice into the area while clasts of Lundy granite were moved by progradation of beach deposits northeastwards towards Gower during glacio-eustatic marine transgressions in the Pleistocene.

APA, Harvard, Vancouver, ISO, and other styles

42

Zellman, Mark S., Christopher B. DuRoss, Glenn D. Thackray, Stephen F. Personius, Nadine G. Reitman, Shannon A. Mahan, and Cooper C. Brossy. "Holocene Rupture History of the Central Teton Fault at Leigh Lake, Grand Teton National Park, Wyoming." Bulletin of the Seismological Society of America 110, no. 1 (November 19, 2019): 67–82. http://dx.doi.org/10.1785/0120190129.

Full text

Abstract:

ABSTRACT Prominent scarps on Pinedale glacial surfaces along the eastern base of the Teton Range confirm latest Pleistocene to Holocene surface-faulting earthquakes on the Teton fault, but the timing of these events is only broadly constrained by a single previous paleoseismic study. We excavated two trenches at the Leigh Lake site near the center of the Teton fault to address open questions about earthquake timing and rupture length. Structural and stratigraphic evidence indicates two surface-faulting earthquakes at the site that postdate deglacial sediments dated by radiocarbon and optically stimulated luminescence to ∼10–11 ka. Earthquake LL2 occurred at ∼10.0 ka (9.7–10.4 ka; 95% confidence range) and LL1 at ∼5.9 ka (4.8–7.1 ka; 95%). LL2 predates an earthquake at ∼8 ka identified in the previous paleoseismic investigation at Granite Canyon. LL1 corresponds to the most recent Granite Canyon earthquake at ∼4.7–7.9 ka (95% confidence range). Our results are consistent with the previously documented long-elapsed time since the most recent Teton fault rupture and expand the fault’s earthquake history into the early Holocene.

APA, Harvard, Vancouver, ISO, and other styles

43

Ehlers, Carl, Alf Lindroos, and Olavi Selonen. "The late Svecofennian granite-migmatite zone of southern Finland—a belt of transpressive deformation and granite emplacement." Precambrian Research 64, no. 1-4 (December 1993): 295–309. http://dx.doi.org/10.1016/0301-9268(93)90083-e.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Boerboom, Terrence J., and Robert E. Zartman. "Geology, geochemistry, and geochronology of the central Giants Range batholith, northeastern Minnesota." Canadian Journal of Earth Sciences 30, no. 12 (December 1, 1993): 2510–22. http://dx.doi.org/10.1139/e93-217.

Full text

Abstract:

The Giants Range batholith is a large composite granitoid body that intrudes deformed supracrustal rocks in the western part of the Wawa Subprovince of the Archean Superior Province. Peak fabric development in the supracrustal rocks coincides with D2 deformation, the product of regional transpression across the southern Superior Province. U–Pb zircon ages on two phases of the Giants Range batholith bracket D2 deformation to an interval between 2685 and 2669 Ma. Two well-exposed components of the central part of the Giants Range batholith are the pre- to syn-D2 Britt granodiorite, which contains a linear D2 metamorphic fabric, and the syn- to post-D2 Shannon Lake granite, which cuts deformation fabrics in the Britt granodiorite and the supracrustal rocks. Geochemical discrimination plots imply emplacement of the Britt granodiorite in an arc environment and the Shannon Lake granite in a collision setting. Zircons yield U–Pb ages of 2681 ± 4 and 2685 ± 4 Ma for the Britt granodiorite and 2674 ± 5 and 2674 ± 27 Ma for the Shannon Lake granite. Timing of D2 deformation near the Giants Range batholith corresponds well with similar rocks exposed along strike 170 km to the east near Shebandowan Lake, Ontario, where the end of D2 deformation has been bracketed between 2692 and 2681 Ma. The slightly younger ages for D2 deformation in Minnesota reflect later volcanic-arc development and associated plutonism than at Shebandowan Lake, possibly due to oblique convergence along a westward-migrating tectonic front.

APA, Harvard, Vancouver, ISO, and other styles

45

Luan, Xiwu, and Peter Lunt. "Eocene to Miocene stratigraphic controls in the far East Java Sea: Implications for stratigraphic studies." Marine Geology 436 (June 2021): 106479. http://dx.doi.org/10.1016/j.margeo.2021.106479.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Tian, Mao-Jun, Huan Li, Landry Soh Tamehe, and Zhen Xi. "Geochronology and Geochemistry of the Zengudi and Tuobake Granite Porphyries in the Sanjiang Region, SW China: Petrogenesis and Tectonic Significance." Minerals 11, no. 4 (April 12, 2021): 404. http://dx.doi.org/10.3390/min11040404.

Full text

Abstract:

The boundary between the Gondwana and Yangtze plate is still controversial. In southwest China, the Sanjiang region marks the collision zone which accreted several blocks coming from the northern Gondwana margin. In this region, subduction of the Paleo-Tethys Ocean and associated continental blocks during the Triassic Period led to the formation of an N–S trending complex involving intrusive and volcanic rocks. The intrusive rocks are important for constraining the evolution of the Paleo-Tethyan in southwestern China. This study presents new geochronological, geochemical, and Sr-Nd-Hf isotopic data of granite porphyries from northern Lancangjiang, in order to discuss the origin of these granites and their tectonic significance. Representative samples of the Zengudi and the Tuobake granite porphyries from the Yezhi area yielded weighted mean 206Pb/238U ages of 247–254 Ma and 246 Ma, respectively. The Zengudi granite porphyries display zircon ԐHf(t) values of −12.94 to −2.63, ԐNd(t) values of −14.5 to −9.35, and initial 87Sr/86Sr ratios of 0.708 to 0.716. The Tuobake granite porphyries have zircon ԐHf(t) values of −14.06 to −6.55, ԐNd(t) values of −10.9 to −9.41, and initial 87Sr/86Sr ratios of 0.716 to 0.731. Both the Zengudi and Tuobake granite porphyries exhibit strongly peraluminous signatures with high A/CNK nAl2O3/(K2O + Na2O + K2O) ratios (1.07–1.86 and 0.83–1.33, respectively). These granites are enriched in Rb and Th, and depleted in Ti, Nb, Ta, Sr, and P, with negative Eu anomalies (Eu/Eu* < 0.61). These geochemical and isotopic data indicate that the primary magma of the granite porphyries originated from partial melting of ancient continental crust as a result of basaltic magma underplating and underwent fractionation crystallization during their emplacement. We propose that the Triassic subduction of the Paleo-Tethys Ocean led to crust shortening and thickening in the Sanjiang region, while the northern Lancangjiang area was involved in the continental collision after the subduction of the Paleo-Tethys Ocean before 254 Ma.

APA, Harvard, Vancouver, ISO, and other styles

47

Mohamed, F. H., M. A. Hassanen, G. Matheis, and M. H. Shalaby. "Geochemistry of the Wadi Hawashia Granite Complex, northern Egyptian Shield." Journal of African Earth Sciences 19, no. 1-2 (July 1994): 61–74. http://dx.doi.org/10.1016/0899-5362(94)90038-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Leonov, M. G., Yu G. Tsekhovskii, E. S. Przhiyalgovskii, A. V. Poleshchuk, and E. V. Lavrushina. "Polygenic nature of granite clastites: Communication 1. Exogenic and tectonic postmagmatic disintegration of granite massifs." Lithology and Mineral Resources 49, no. 1 (January 2014): 81–102. http://dx.doi.org/10.1134/s0024490213060060.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Esteban, J. J., J. Cuevas, and J. M. Tubía. "Geochemistry and origin of zircon in chlorite schists of the Ronda peridotites (Betic Cordilleras, southern Spain)." Lithosphere 11, no. 6 (November 4, 2019): 855–67. http://dx.doi.org/10.1130/l1088.1.

Full text

Abstract:

Abstract This work deals with scarce chlorite schists scattered through the Ronda peridotites (Betic Cordilleras, Spain). These schists have unusually high zircon contents, which contrast with the usual lack of this mineral in ultramafic rocks. From field data and detailed petrographic, geochemical, and geothermometric studies, we focused on the origin of the zircon, a relevant issue for the interpretation of geochronological results. The chlorite schists appear as concordant sheets with granite dikes and as blackwall zones between dikes and serpentinized peridotites. As the intrusion age of the dikes and chlorite schist zircon crystallization (ca. 22 Ma) is slightly older than the age of serpentinization and related chlorite schist formation (ca. 19 Ma), we propose that the chlorite schists are tied to the intrusion of the granite dikes and the subsequent serpentinization of peridotites. Trace and rare earth elements alone are not indicative of the magmatic or hydrothermal origin of the zircon, but the combination of information about zircon morphology, melt inclusions, geothermometry, and the structural relationships between granite dikes and chlorite schists points to late magmatic melts for the zircon origin. We suggest that high-temperature melts saturated in F and Cl acted as Zr carriers under low-pH conditions. A change of the pH conditions, due to hydrothermal alkaline fluids incoming for the concomitant peridotite serpentinization, would have led to zircon crystallization and concentration at the apical zones of the dikes, and to rodingitization before the extensive observed chloritization.

APA, Harvard, Vancouver, ISO, and other styles

50

Nironen, M., and O. T. Rämö. "The Oripää granite revisited: Elemental geochemistry, Nd isotopes, and implication to terrane boundary." Bulletin of the Geological Society of Finland 83, no. 2 (December 2011): 115–22. http://dx.doi.org/10.17741/bgsf/83.2.003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Granite Geology, Stratigraphic Geochemistry'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles