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Saumitra Misra - One of the best experts on this subject based on the ideXlab platform.
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2 8 ga old anorogenic granite Acid Volcanics association from western margin of the singhbhum orissa craton eastern india
Gondwana Research, 2001Co-Authors: P K Bandyopadhyay, A K Chakrabarti, M P Deomurari, Saumitra MisraAbstract:Abstract The Tamperkola granite-Acid Volcanics association occurring at the western margin of the Archaean Singhbhum-Orissa Iron Ore Craton (SOC), eastern India, is intrusive into the Darjing Group which represents a sequence of mobile belt metasediments in this part of the SOC. The Darjing Group rests unconformably on the Bonai Granite (∼3.2 Ga old). Absence of any deformational imprints of the country rock metasediments on the Tamperkola granite Acid Volcanics together with its undeformed and unmetamorphosed nature, its alkali feldspar dominant mineralogy, and its high SiO 2 and Na 2 O + K 2 O and low MgO and CaO contents suggest that this granite-Acid Volcanics association is anorogenic in nature. Two representative samples-one each from the granite and the Acid Volcanics have been dated by in situ 207 Pb/ 206 Pb zircon dating method using a small ion-microprobe. Minimum age of crystallisation of the Acid Volcanics is found to be 2.8 Ga. Strong peak in the 207 Pb/ 206 Pb frequency diagram and equality of the observed and expected errors in radiogenic 207 Pb/ 206 Pb ratios suggest that this age probably represents the true age of formation of the Volcanics. The age data place the deposition and metamorphism of the mobile belt metasediments of the Darjing Group in between 3.2 and 2.8 Ga. Occurrence of 2.9–2.8 Ga old small granitoid plutons, alkali-feldspar granite to syenogranite in composition, is also known from the southern margin of the SOC. Therefore, it appears that around 2.9–2.8 Ga small alkali granite bodies formed at the marginal part of this cratonic block after its stabilisation at ∼3.1 Ga.
Jean Besse - One of the best experts on this subject based on the ideXlab platform.
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evidence for a neoarchean lip in the singhbhum craton eastern india implications to vaalbara supercontinent
Precambrian Research, 2017Co-Authors: Ashwani Kumar, V Parashuramulu, Ravi Shankar, Jean BesseAbstract:Abstract We report eight new Pb-Pb baddeleyite ages and paleomagnetic results on a series of hitherto unknown Neoarchean NNE-SSW trending mafic dyke swarms intruding the Paleoarchean basement rocks in the Singhbhum craton, eastern India. Being the most dominant dyke swarms in the region, they occur over the entire Singhbhum craton with an areal distribution extending to about 30,000 km 2 . Of the eight dyke samples analysed across the entire dyke swarm, six were emplaced at 2762.4 ± 2.0 Ma (weighted mean of 6 dyke ages), two with similar strike directions, yielded older and younger ages of 2800.2 ± 0.7 Ma and 2752.0 ± 0.9 Ma respectively. The older 2800.2 ± 0.7 Ma dyke event appears to be coeval with several other magmatic events reported earlier from the Singhbhum craton. Emplacement of dacite tuffs within the Malaigiri basin, on the southern margin of the craton, the Budhapal and Rengali granite from the south-western and southern parts of the craton, along with the Temperkola granite activity and associated Acid Volcanics in the western part of the craton, and perhaps the Mayurbhanj granite (fine-grained phase) are also contemporaneous, suggesting a fairly wide spread thermal event in the region at this time. Well defined craton-wide magmatic events contemporaneous to the 2762.4 ± 2.0 Ma Singhbhum dyke activity have been reported from the Pilbara. The younger 2752.0 ± 0.9 Ma age dyke event occurring in the Singhbhum is also know from the eastern Pilbara. An older event at 2783 ± 1.2 Ma (Gaborone-Kanye-Plantation Porphyry-Derdepoort-Modipe episode) was identified in the Kaapvaal craton. Comparison of paleomagnetic data obtained on the Singhbhum Neoarchean dyke swarms with the Pilbara and Kaapvaal data, show all these continents were located at steep latitudes and could have been proximal to each other during this time. If Pilbara and Kaapvaal formed supercraton Vaalbara during the Neoarchean time, we propose Singhbhum with similar Archean geology could also have had its ancestry in the same supercraton.
Franz Gerhard - One of the best experts on this subject based on the ideXlab platform.
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The Bajo Pobre Formation Jurassic in the eastern Deseado Massif, Patagonia: Relationship with the Bahía Laura Group
2020Co-Authors: Guido, Diego Martín, Escayola, Mónica Patricia, Raúl Ernesto De ,barrio, Schalamuk, Bernardo Isidoro, Franz GerhardAbstract:Se describen nuevos afloramientos de la Formación Bajo Pobre hallados en el sector oriental del Macizo del Deseado, provincia de Santa Cruz, Patagonia Argentina. Esta unidad, junto con el Grupo Bahía Laura, corresponden al evento más importante magmático-piroclástico del Jurásico medio a superior del Macizo del Deseado. Se trata de lavas melanocráticas porfíricas a afaníticas, con fenocristales de plagioclasa, piroxeno y ocasional biotita, en una pasta de textura intersertal con microlitos de plagioclasa, piroxeno, opacos y en ocasiones con olivina. Las plagioclasas son de composición An53 a An85 (labradorita a bitownita) y los piroxenos son augita (Wo39 En48 Fs13), y pigeonita (Wo11 En54 Fs35) en los microlitos de las rocas con olivina (Fo51-45 Fa49-55). Son rocas intermedias a básicas, de composición andesita basáltica a andesita y con afinidades calcoalcalinas. Se describen lavas de la Formación Bajo Pobre con relaciones estratigráficas infra y suprayacentes respecto de rocas volcánicas ácidas del Grupo Bahía Laura. En las andesitas basálticas suprayacentes al Grupo Bahía Laura se obtuvo una edad K-Ar en roca total de 151,3 ± 3,4 Ma y para las andesitas infrayacentes se asume una edad Ar-Ar en plagioclasa de 177 ± 4 Ma. Estos estudios corroboran la extensión de los afloramientos de la Formación Bajo Pobre hacia la región costera del Macizo del Deseado y la combinación de las observaciones estratigráficas y geocronológicas confirman la relación de coetaneidad y posible intercalación entre las lavas de la Formación Bajo Pobre y las volcanitas ácidas del Grupo Bahía Laura, avalando la bimodalidad del magmatismo jurásico en el Macizo del Deseado.New Bajo Pobre Formation outcrops found in the eastern sector of the Deseado Massif, Santa Cruz province, Patagonia, are described. This unit, together with the Bahía Laura Group, is the most important magmato-pyroclastic event of the Deseado Massif. They are melanocratic, porphyric to aphanitic lava flows, with plagioclase, pyroxene and occasionally biotite phenocrysts in an intersertal matrix with plagioclase, pyroxene, opaque and occasionally with olivine microlites. Plagioclases are An53 to An85 (labradorite – bytownite) and pyroxenes are augite (Wo39 En48 Fs13), and pigeonite microlites (Wo11 En54 Fs35) in the rocks with olivine (Fo51-45 Fa49-55) microlites. They are intermediate to basic rocks, basaltic andesite to andesite in composition with calc-alkaline affinities. Underlying and overlying stratigraphic relationships of the Bajo Pobre Formation lava flows with the Bahía Laura Group Acid Volcanics are described. In the basaltic andesites overlying the Bahía Laura Group it was determined a 151.3 ± 3.4 Ma whole-rock K-Ar age and an assumed plagioclase Ar-Ar age of 177 ± 4 Ma for the underlying andesitic rocks. These studies confirm the extension of the Bajo Pobre Formation outcrops up to the Laura Group it was determined a 151.3 ± 3.4 Ma whole-rock K-Ar age and an assumed plagioclase Ar-Ar age of 177 ± 4 Ma for the underlying andesitic rocks. These studies confirm the extension of the Bajo Pobre Formation outcrops up to the coastal region of the Deseado Massif. The combination of stratigraphic observations and geochronology is in agreement with the coeval and possible interbedding relationship between the Bajo Pobre Formation lavas and the Bahía Laura Group Acid volcanic rocks, supporting the bimodality of the Jurassic magmatism for the Deseado Massif.Facultad de Ciencias Naturales y Muse
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The Bajo Pobre Formation Jurassic in the eastern Deseado Massif, Patagonia: Relationship with the Bahía Laura Group
Asociación Geológica Argentina, 2006Co-Authors: Guido, Diego Martín, Escayola, Mónica Patricia, Schalamuk, Bernardo Isidoro, De Barrio, Raul Ernesto, Franz GerhardAbstract:Se describen nuevos afloramientos de la Formación Bajo Pobre hallados en el sector oriental del Macizo del Deseado, provincia de Santa Cruz, Patagonia Argentina. Esta unidad, junto con el Grupo Bahía Laura, corresponden al evento más importante magmático-piroclástico del Jurásico medio a superior del Macizo del Deseado. Se trata de lavas melanocráticas porfíricas a afaníticas, con fenocristales de plagioclasa, piroxeno y ocasional biotita, en una pasta de textura intersertal con microlitos de plagioclasa, piroxeno, opacos y en ocasiones con olivina. Las plagioclasas son de composición An53 a An85 (labradorita a bitownita) y los piroxenos son augita (Wo39 En48 Fs13), y pigeonita (Wo11 En54 Fs35) en los microlitos de las rocas con olivina (Fo51-45 Fa49-55). Son rocas intermedias a básicas, de composición andesita basáltica a andesita y con afinidades calcoalcalinas. Se describen lavas de la Formación Bajo Pobre con relaciones estratigráficas infra y suprayacentes respecto de rocas volcánicas ácidas del Grupo Bahía Laura. En las andesitas basálticas suprayacentes al Grupo Bahía Laura se obtuvo una edad K-Ar en roca total de 151,3 ± 3,4 Ma y para las andesitas infrayacentes se asume una edad Ar-Ar en plagioclasa de 177 ± 4 Ma. Estos estudios corroboran la extensión de los afloramientos de la Formación Bajo Pobre hacia la región costera del Macizo del Deseado y la combinación de las observaciones estratigráficas y geocronológicas confirman la relación de coetaneidad y posible intercalación entre las lavas de la Formación Bajo Pobre y las volcanitas ácidas del Grupo Bahía Laura, avalando la bimodalidad del magmatismo jurásico en el Macizo del Deseado.New Bajo Pobre Formation outcrops found in the eastern sector of the Deseado Massif, Santa Cruz province, Patagonia, are described. This unit, together with the Bahía Laura Group, is the most important magmato-pyroclastic event of the Deseado Massif. They are melanocratic, porphyric to aphanitic lava flows, with plagioclase, pyroxene and occasionally biotite phenocrysts in an intersertal matrix with plagioclase, pyroxene, opaque and occasionally with olivine microlites. Plagioclases are An53 to An85 (labradorite – bytownite) and pyroxenes are augite (Wo39 En48 Fs13), and pigeonite microlites (Wo11 En54 Fs35) in the rocks with olivine (Fo51-45 Fa49-55) microlites. They are intermediate to basic rocks, basaltic andesite to andesite in composition with calc-alkaline affinities. Underlying and overlying stratigraphic relationships of the Bajo Pobre Formation lava flows with the Bahía Laura Group Acid Volcanics are described. In the basaltic andesites overlying the Bahía Laura Group it was determined a 151.3 ± 3.4 Ma whole-rock K-Ar age and an assumed plagioclase Ar-Ar age of 177 ± 4 Ma for the underlying andesitic rocks. These studies confirm the extension of the Bajo Pobre Formation outcrops up to the Laura Group it was determined a 151.3 ± 3.4 Ma whole-rock K-Ar age and an assumed plagioclase Ar-Ar age of 177 ± 4 Ma for the underlying andesitic rocks. These studies confirm the extension of the Bajo Pobre Formation outcrops up to the coastal region of the Deseado Massif. The combination of stratigraphic observations and geochronology is in agreement with the coeval and possible interbedding relationship between the Bajo Pobre Formation lavas and the Bahía Laura Group Acid volcanic rocks, supporting the bimodality of the Jurassic magmatism for the Deseado Massif.Fil: Guido, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Escayola, Monica Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidade de Brasilia, Instituto de Geociencias; BrasilFil: de Barrio, Raul Ernesto. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Schalamuk, Bernardo Isidoro. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Franz, Gerhard. Universitaet Berlin; Alemani
P K Bandyopadhyay - One of the best experts on this subject based on the ideXlab platform.
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2 8 ga old anorogenic granite Acid Volcanics association from western margin of the singhbhum orissa craton eastern india
Gondwana Research, 2001Co-Authors: P K Bandyopadhyay, A K Chakrabarti, M P Deomurari, Saumitra MisraAbstract:Abstract The Tamperkola granite-Acid Volcanics association occurring at the western margin of the Archaean Singhbhum-Orissa Iron Ore Craton (SOC), eastern India, is intrusive into the Darjing Group which represents a sequence of mobile belt metasediments in this part of the SOC. The Darjing Group rests unconformably on the Bonai Granite (∼3.2 Ga old). Absence of any deformational imprints of the country rock metasediments on the Tamperkola granite Acid Volcanics together with its undeformed and unmetamorphosed nature, its alkali feldspar dominant mineralogy, and its high SiO 2 and Na 2 O + K 2 O and low MgO and CaO contents suggest that this granite-Acid Volcanics association is anorogenic in nature. Two representative samples-one each from the granite and the Acid Volcanics have been dated by in situ 207 Pb/ 206 Pb zircon dating method using a small ion-microprobe. Minimum age of crystallisation of the Acid Volcanics is found to be 2.8 Ga. Strong peak in the 207 Pb/ 206 Pb frequency diagram and equality of the observed and expected errors in radiogenic 207 Pb/ 206 Pb ratios suggest that this age probably represents the true age of formation of the Volcanics. The age data place the deposition and metamorphism of the mobile belt metasediments of the Darjing Group in between 3.2 and 2.8 Ga. Occurrence of 2.9–2.8 Ga old small granitoid plutons, alkali-feldspar granite to syenogranite in composition, is also known from the southern margin of the SOC. Therefore, it appears that around 2.9–2.8 Ga small alkali granite bodies formed at the marginal part of this cratonic block after its stabilisation at ∼3.1 Ga.
Ashwani Kumar - One of the best experts on this subject based on the ideXlab platform.
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evidence for a neoarchean lip in the singhbhum craton eastern india implications to vaalbara supercontinent
Precambrian Research, 2017Co-Authors: Ashwani Kumar, V Parashuramulu, Ravi Shankar, Jean BesseAbstract:Abstract We report eight new Pb-Pb baddeleyite ages and paleomagnetic results on a series of hitherto unknown Neoarchean NNE-SSW trending mafic dyke swarms intruding the Paleoarchean basement rocks in the Singhbhum craton, eastern India. Being the most dominant dyke swarms in the region, they occur over the entire Singhbhum craton with an areal distribution extending to about 30,000 km 2 . Of the eight dyke samples analysed across the entire dyke swarm, six were emplaced at 2762.4 ± 2.0 Ma (weighted mean of 6 dyke ages), two with similar strike directions, yielded older and younger ages of 2800.2 ± 0.7 Ma and 2752.0 ± 0.9 Ma respectively. The older 2800.2 ± 0.7 Ma dyke event appears to be coeval with several other magmatic events reported earlier from the Singhbhum craton. Emplacement of dacite tuffs within the Malaigiri basin, on the southern margin of the craton, the Budhapal and Rengali granite from the south-western and southern parts of the craton, along with the Temperkola granite activity and associated Acid Volcanics in the western part of the craton, and perhaps the Mayurbhanj granite (fine-grained phase) are also contemporaneous, suggesting a fairly wide spread thermal event in the region at this time. Well defined craton-wide magmatic events contemporaneous to the 2762.4 ± 2.0 Ma Singhbhum dyke activity have been reported from the Pilbara. The younger 2752.0 ± 0.9 Ma age dyke event occurring in the Singhbhum is also know from the eastern Pilbara. An older event at 2783 ± 1.2 Ma (Gaborone-Kanye-Plantation Porphyry-Derdepoort-Modipe episode) was identified in the Kaapvaal craton. Comparison of paleomagnetic data obtained on the Singhbhum Neoarchean dyke swarms with the Pilbara and Kaapvaal data, show all these continents were located at steep latitudes and could have been proximal to each other during this time. If Pilbara and Kaapvaal formed supercraton Vaalbara during the Neoarchean time, we propose Singhbhum with similar Archean geology could also have had its ancestry in the same supercraton.
