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M A Malapur - One of the best experts on this subject based on the ideXlab platform.
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petrography and geochemistry of the neoarchaean Greywackes from central part of the dharwar shimoga greenstone belt western dharwar craton
International journal of Earth Sciences and Engineering, 2017Co-Authors: T B Manuvachari, A G Ugarkar, Chandan B Kumar, M A MalapurAbstract:Greywackes are the most dominant of litho units in the central part of the Dharwar-Shimoga greenstone belt of the Western Dharwar Craton. They are texturally immature with angular to subangular detrital sand grains with 25 to 60% matrix. Quartz forms the main detrital component and is mostly monocrystalline with distinct undulatory extinction. Amongst feldspars, plagioclase feldspar exceeds K-feldspar. Micas occur as large and small flakes that are oriented. Biotite is the main mica mineral. The phyllite, chert, quartzite and felsic volcanic rock fragments are common. The matrix is generally made up of chlorite, sericite, clay to silt-sized quartz and feldspar. In Q-F-L classification diagram, these rocks plot in the fields of quartz wackes and quartzose wackes. The silica content varies between 60.93 and 68.07 wt% and alkalies between 3.69 and 5.21 (Table 2), and compositionally they are comparable to andesite and dacite. Moderately higher values of Fe 2 O 3 (av. 8.16 wt%), MgO (av. 7.89 wt%) and K 2 O/Na 2 O (av. 1.65) indicate a matrix with an abundance of chlorite, biotite, clays and iron oxides. The petrographic and geochemical evidence suggests that these Greywackes were derived from the source which had felsic to intermediate composition, with a moderate relief exposed to arid and dry palaeoclimatic conditions. As compared to Greywackes of the northern part of the Dharwar-Shimoga greenstone belt, the Greywackes of the present study area (central part) have higher values of MgO, Fe 2 O 3 +MgO, K 2 O/Na 2 O, Al 2 O 3 /Na 2 O and lower values of Al 2 O 3 , Na 2 O, and SiO 2 /MgO.
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petrography and geochemistry of archaean Greywackes from northern part of the dharwar shimoga greenstone belt western dharwar craton implications for nature of provenance
Journal of The Geological Society of India, 2017Co-Authors: A G Ugarkar, Chandan B Kumar, M A Malapur, T B Manuvachari, Andrew C KerrAbstract:Greywackes (Dharwar Greywackes) are the most abundant rock types in the northern part of the Dharwar-Shimoga greenstone belt of the western Dharwar craton. They are distinctly immature rocks with poorly-sorted angular to sub-angular grains, comprising largely quartz, plagioclase feldspar and lithic fragments of volcanics (mafic+felsic), chert and quartzite, with subordinate biotite, K-feldspar and muscovite. They are characterized by almost uniform silica (59.78-67.96 wt%; av. 62.58), alkali (4.62-7.35 wt%; av. 5.41) contents, SiO2/Al2O3 (3.71-5.25) ratios, and compositionally are comparable to the andesite and dacite. As compared to Ranibennur Greywackes, located about 100 km south of Dharwad in the Dharwar-Shimoga greenstone belt, the Dharwar Greywackes have higher K2O, CaO, Zr, Y, ΣREE, Th/Sc, Zr/Cr, La/Sc and lower Sr, Cr, Ni, Sc, Cr/Th values. The chondrite normalized patterns of Dharwar Greywackes are characterized by moderately fractionated REE patterns with moderate to high LREE enrichment, with almost flat HREE patterns and small negative Eu anomalies, suggesting felsic dominated source rocks in the provenance. The frame work grains comprising felsic and mafic volcanics, feldspars and quartz suggest a mixed source in the provenance. The moderate CIA values ranging between 57 and 73, indicate derivation of detritus from fresh basement rocks and from nearby volcanic sources.The mixing calculations suggest that the average REE pattern is closely matching with a provenance having 40% dacite, 30% granite, 20% basalt and 10% tonalite. These Greywackes were deposited in a subduction related forearc basin than a continental margin basin. Their La/Sc ratios are high (av. 4.07) compared to the Ranibennur Greywackes (1.79), suggesting that the Greywackes of the northern part of the basin received detritus from a more evolved continental crust than the Greywackes of the central part of the Dharwar-Shimoga basin.
Prosun Bhattacharya - One of the best experts on this subject based on the ideXlab platform.
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petrology and geochemistry of Greywackes from the aravalli supergroup rajasthan india and the tectonic evolution of a proterozoic sedimentary basin
Precambrian Research, 1994Co-Authors: D M Banerjee, Prosun BhattacharyaAbstract:The Proterozoic Aravalli Supergroup in south-central Rajasthan, western India is predominantly composed of coarse, low-grade meta-arenites, carbonates, Greywackes, interbedded fine-grained silty arenites and metapelites resting on an Archaean basement complex of gneisses, schists and high-grade metasediments. We have differentiated four lithofacies (A, B, C and D) within the greywacke suite, each with characteristic QFL composition, grain size and major, trace and rare earth element concentrations. Tectonic setting for each facies type could only be discriminated using QmFLt plots. Greywackes of facies A and D were derived from a recycled orogen and facies B was derived from arc-related andesitic source rocks. A continental block provenance is indicated for the silty arenites of facies C. This petrofacies-based interpretation shows good agreement with environmental reconstructions based on lithofacies and sedimentary structure analyses. The only exception is facies B, whose andesitic parentage as deduced from petrofacies analysis could not be demonstrated at its outcrop. These provenance discriminations were tested through tectonic setting interpretations based on major, trace and rare earth elements. The geochemical data broadly confirmed the tectonic interpretations made on the basis of the petrological attributes. Use of these laboratory-based methods in conjunction with field measurements of primary sedimentary structures allow us to discriminate provenance and tectonic setting fairly precisely. A Proterozoic plate model with subduction to the west has been proposed to explain the sedimentological variation in the Aravalli Supergroup.
T B Manuvachari - One of the best experts on this subject based on the ideXlab platform.
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petrography and geochemistry of the neoarchaean Greywackes from central part of the dharwar shimoga greenstone belt western dharwar craton
International journal of Earth Sciences and Engineering, 2017Co-Authors: T B Manuvachari, A G Ugarkar, Chandan B Kumar, M A MalapurAbstract:Greywackes are the most dominant of litho units in the central part of the Dharwar-Shimoga greenstone belt of the Western Dharwar Craton. They are texturally immature with angular to subangular detrital sand grains with 25 to 60% matrix. Quartz forms the main detrital component and is mostly monocrystalline with distinct undulatory extinction. Amongst feldspars, plagioclase feldspar exceeds K-feldspar. Micas occur as large and small flakes that are oriented. Biotite is the main mica mineral. The phyllite, chert, quartzite and felsic volcanic rock fragments are common. The matrix is generally made up of chlorite, sericite, clay to silt-sized quartz and feldspar. In Q-F-L classification diagram, these rocks plot in the fields of quartz wackes and quartzose wackes. The silica content varies between 60.93 and 68.07 wt% and alkalies between 3.69 and 5.21 (Table 2), and compositionally they are comparable to andesite and dacite. Moderately higher values of Fe 2 O 3 (av. 8.16 wt%), MgO (av. 7.89 wt%) and K 2 O/Na 2 O (av. 1.65) indicate a matrix with an abundance of chlorite, biotite, clays and iron oxides. The petrographic and geochemical evidence suggests that these Greywackes were derived from the source which had felsic to intermediate composition, with a moderate relief exposed to arid and dry palaeoclimatic conditions. As compared to Greywackes of the northern part of the Dharwar-Shimoga greenstone belt, the Greywackes of the present study area (central part) have higher values of MgO, Fe 2 O 3 +MgO, K 2 O/Na 2 O, Al 2 O 3 /Na 2 O and lower values of Al 2 O 3 , Na 2 O, and SiO 2 /MgO.
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petrography and geochemistry of archaean Greywackes from northern part of the dharwar shimoga greenstone belt western dharwar craton implications for nature of provenance
Journal of The Geological Society of India, 2017Co-Authors: A G Ugarkar, Chandan B Kumar, M A Malapur, T B Manuvachari, Andrew C KerrAbstract:Greywackes (Dharwar Greywackes) are the most abundant rock types in the northern part of the Dharwar-Shimoga greenstone belt of the western Dharwar craton. They are distinctly immature rocks with poorly-sorted angular to sub-angular grains, comprising largely quartz, plagioclase feldspar and lithic fragments of volcanics (mafic+felsic), chert and quartzite, with subordinate biotite, K-feldspar and muscovite. They are characterized by almost uniform silica (59.78-67.96 wt%; av. 62.58), alkali (4.62-7.35 wt%; av. 5.41) contents, SiO2/Al2O3 (3.71-5.25) ratios, and compositionally are comparable to the andesite and dacite. As compared to Ranibennur Greywackes, located about 100 km south of Dharwad in the Dharwar-Shimoga greenstone belt, the Dharwar Greywackes have higher K2O, CaO, Zr, Y, ΣREE, Th/Sc, Zr/Cr, La/Sc and lower Sr, Cr, Ni, Sc, Cr/Th values. The chondrite normalized patterns of Dharwar Greywackes are characterized by moderately fractionated REE patterns with moderate to high LREE enrichment, with almost flat HREE patterns and small negative Eu anomalies, suggesting felsic dominated source rocks in the provenance. The frame work grains comprising felsic and mafic volcanics, feldspars and quartz suggest a mixed source in the provenance. The moderate CIA values ranging between 57 and 73, indicate derivation of detritus from fresh basement rocks and from nearby volcanic sources.The mixing calculations suggest that the average REE pattern is closely matching with a provenance having 40% dacite, 30% granite, 20% basalt and 10% tonalite. These Greywackes were deposited in a subduction related forearc basin than a continental margin basin. Their La/Sc ratios are high (av. 4.07) compared to the Ranibennur Greywackes (1.79), suggesting that the Greywackes of the northern part of the basin received detritus from a more evolved continental crust than the Greywackes of the central part of the Dharwar-Shimoga basin.
Chandan B Kumar - One of the best experts on this subject based on the ideXlab platform.
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petrography and geochemistry of the neoarchaean Greywackes from central part of the dharwar shimoga greenstone belt western dharwar craton
International journal of Earth Sciences and Engineering, 2017Co-Authors: T B Manuvachari, A G Ugarkar, Chandan B Kumar, M A MalapurAbstract:Greywackes are the most dominant of litho units in the central part of the Dharwar-Shimoga greenstone belt of the Western Dharwar Craton. They are texturally immature with angular to subangular detrital sand grains with 25 to 60% matrix. Quartz forms the main detrital component and is mostly monocrystalline with distinct undulatory extinction. Amongst feldspars, plagioclase feldspar exceeds K-feldspar. Micas occur as large and small flakes that are oriented. Biotite is the main mica mineral. The phyllite, chert, quartzite and felsic volcanic rock fragments are common. The matrix is generally made up of chlorite, sericite, clay to silt-sized quartz and feldspar. In Q-F-L classification diagram, these rocks plot in the fields of quartz wackes and quartzose wackes. The silica content varies between 60.93 and 68.07 wt% and alkalies between 3.69 and 5.21 (Table 2), and compositionally they are comparable to andesite and dacite. Moderately higher values of Fe 2 O 3 (av. 8.16 wt%), MgO (av. 7.89 wt%) and K 2 O/Na 2 O (av. 1.65) indicate a matrix with an abundance of chlorite, biotite, clays and iron oxides. The petrographic and geochemical evidence suggests that these Greywackes were derived from the source which had felsic to intermediate composition, with a moderate relief exposed to arid and dry palaeoclimatic conditions. As compared to Greywackes of the northern part of the Dharwar-Shimoga greenstone belt, the Greywackes of the present study area (central part) have higher values of MgO, Fe 2 O 3 +MgO, K 2 O/Na 2 O, Al 2 O 3 /Na 2 O and lower values of Al 2 O 3 , Na 2 O, and SiO 2 /MgO.
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petrography and geochemistry of archaean Greywackes from northern part of the dharwar shimoga greenstone belt western dharwar craton implications for nature of provenance
Journal of The Geological Society of India, 2017Co-Authors: A G Ugarkar, Chandan B Kumar, M A Malapur, T B Manuvachari, Andrew C KerrAbstract:Greywackes (Dharwar Greywackes) are the most abundant rock types in the northern part of the Dharwar-Shimoga greenstone belt of the western Dharwar craton. They are distinctly immature rocks with poorly-sorted angular to sub-angular grains, comprising largely quartz, plagioclase feldspar and lithic fragments of volcanics (mafic+felsic), chert and quartzite, with subordinate biotite, K-feldspar and muscovite. They are characterized by almost uniform silica (59.78-67.96 wt%; av. 62.58), alkali (4.62-7.35 wt%; av. 5.41) contents, SiO2/Al2O3 (3.71-5.25) ratios, and compositionally are comparable to the andesite and dacite. As compared to Ranibennur Greywackes, located about 100 km south of Dharwad in the Dharwar-Shimoga greenstone belt, the Dharwar Greywackes have higher K2O, CaO, Zr, Y, ΣREE, Th/Sc, Zr/Cr, La/Sc and lower Sr, Cr, Ni, Sc, Cr/Th values. The chondrite normalized patterns of Dharwar Greywackes are characterized by moderately fractionated REE patterns with moderate to high LREE enrichment, with almost flat HREE patterns and small negative Eu anomalies, suggesting felsic dominated source rocks in the provenance. The frame work grains comprising felsic and mafic volcanics, feldspars and quartz suggest a mixed source in the provenance. The moderate CIA values ranging between 57 and 73, indicate derivation of detritus from fresh basement rocks and from nearby volcanic sources.The mixing calculations suggest that the average REE pattern is closely matching with a provenance having 40% dacite, 30% granite, 20% basalt and 10% tonalite. These Greywackes were deposited in a subduction related forearc basin than a continental margin basin. Their La/Sc ratios are high (av. 4.07) compared to the Ranibennur Greywackes (1.79), suggesting that the Greywackes of the northern part of the basin received detritus from a more evolved continental crust than the Greywackes of the central part of the Dharwar-Shimoga basin.
A G Ugarkar - One of the best experts on this subject based on the ideXlab platform.
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petrography and geochemistry of the neoarchaean Greywackes from central part of the dharwar shimoga greenstone belt western dharwar craton
International journal of Earth Sciences and Engineering, 2017Co-Authors: T B Manuvachari, A G Ugarkar, Chandan B Kumar, M A MalapurAbstract:Greywackes are the most dominant of litho units in the central part of the Dharwar-Shimoga greenstone belt of the Western Dharwar Craton. They are texturally immature with angular to subangular detrital sand grains with 25 to 60% matrix. Quartz forms the main detrital component and is mostly monocrystalline with distinct undulatory extinction. Amongst feldspars, plagioclase feldspar exceeds K-feldspar. Micas occur as large and small flakes that are oriented. Biotite is the main mica mineral. The phyllite, chert, quartzite and felsic volcanic rock fragments are common. The matrix is generally made up of chlorite, sericite, clay to silt-sized quartz and feldspar. In Q-F-L classification diagram, these rocks plot in the fields of quartz wackes and quartzose wackes. The silica content varies between 60.93 and 68.07 wt% and alkalies between 3.69 and 5.21 (Table 2), and compositionally they are comparable to andesite and dacite. Moderately higher values of Fe 2 O 3 (av. 8.16 wt%), MgO (av. 7.89 wt%) and K 2 O/Na 2 O (av. 1.65) indicate a matrix with an abundance of chlorite, biotite, clays and iron oxides. The petrographic and geochemical evidence suggests that these Greywackes were derived from the source which had felsic to intermediate composition, with a moderate relief exposed to arid and dry palaeoclimatic conditions. As compared to Greywackes of the northern part of the Dharwar-Shimoga greenstone belt, the Greywackes of the present study area (central part) have higher values of MgO, Fe 2 O 3 +MgO, K 2 O/Na 2 O, Al 2 O 3 /Na 2 O and lower values of Al 2 O 3 , Na 2 O, and SiO 2 /MgO.
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petrography and geochemistry of archaean Greywackes from northern part of the dharwar shimoga greenstone belt western dharwar craton implications for nature of provenance
Journal of The Geological Society of India, 2017Co-Authors: A G Ugarkar, Chandan B Kumar, M A Malapur, T B Manuvachari, Andrew C KerrAbstract:Greywackes (Dharwar Greywackes) are the most abundant rock types in the northern part of the Dharwar-Shimoga greenstone belt of the western Dharwar craton. They are distinctly immature rocks with poorly-sorted angular to sub-angular grains, comprising largely quartz, plagioclase feldspar and lithic fragments of volcanics (mafic+felsic), chert and quartzite, with subordinate biotite, K-feldspar and muscovite. They are characterized by almost uniform silica (59.78-67.96 wt%; av. 62.58), alkali (4.62-7.35 wt%; av. 5.41) contents, SiO2/Al2O3 (3.71-5.25) ratios, and compositionally are comparable to the andesite and dacite. As compared to Ranibennur Greywackes, located about 100 km south of Dharwad in the Dharwar-Shimoga greenstone belt, the Dharwar Greywackes have higher K2O, CaO, Zr, Y, ΣREE, Th/Sc, Zr/Cr, La/Sc and lower Sr, Cr, Ni, Sc, Cr/Th values. The chondrite normalized patterns of Dharwar Greywackes are characterized by moderately fractionated REE patterns with moderate to high LREE enrichment, with almost flat HREE patterns and small negative Eu anomalies, suggesting felsic dominated source rocks in the provenance. The frame work grains comprising felsic and mafic volcanics, feldspars and quartz suggest a mixed source in the provenance. The moderate CIA values ranging between 57 and 73, indicate derivation of detritus from fresh basement rocks and from nearby volcanic sources.The mixing calculations suggest that the average REE pattern is closely matching with a provenance having 40% dacite, 30% granite, 20% basalt and 10% tonalite. These Greywackes were deposited in a subduction related forearc basin than a continental margin basin. Their La/Sc ratios are high (av. 4.07) compared to the Ranibennur Greywackes (1.79), suggesting that the Greywackes of the northern part of the basin received detritus from a more evolved continental crust than the Greywackes of the central part of the Dharwar-Shimoga basin.
