Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite
The late Aptian (118–115 Ma) continental flood basalts of the Rajmahal Volcanic Province (RVP) are part of the Kerguelen Large Igneous Province, and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin. The lower one-third of the Rajmahal volcanic succession c...
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ftleicester:oai:lra.le.ac.uk:2381/38056 2023-05-15T13:31:55+02:00 Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite Ghose, Naresh C. Chatterjee, Nilanjan Windley, Brian F. 2016-09-13T09:05:17Z http://www.sciencedirect.com/science/article/pii/S1674987116300639 http://hdl.handle.net/2381/38056 https://doi.org/10.1016/j.gsf.2016.06.007 en eng Elsevier on behalf of China University of Geosciences (Beijing) Geoscience Frontiers, 2016, in press 1674-9871 http://www.sciencedirect.com/science/article/pii/S1674987116300639 http://hdl.handle.net/2381/38056 doi:10.1016/j.gsf.2016.06.007 Copyright © the authors, 2016. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. CC-BY-NC-ND Journal Article Article 2016 ftleicester https://doi.org/10.1016/j.gsf.2016.06.007 2019-03-22T20:21:52Z The late Aptian (118–115 Ma) continental flood basalts of the Rajmahal Volcanic Province (RVP) are part of the Kerguelen Large Igneous Province, and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin. The lower one-third of the Rajmahal volcanic succession contains thin layers of plant fossil-rich inter-trappean sedimentary rocks with pyroclasts, bentonite, grey and black shale/mudstone and oolite, whereas the upper two-thirds consist of sub-aerial fine-grained aphyric basalts with no inter-trappean material. At the eastern margin and the north-central sector of the RVP, the volcanics in the lower part include rhyolites and dacites overlain by enstatite-bearing basalts and enstatite-andesites. The pyroclastic rocks are largely felsic in composition, and comprise ignimbrite as well as coarse-grained tuff with lithic clasts, and tuff breccia with bombs, lapilli and ash that indicate explosive eruption of viscous rhyolitic magma. The rhyolites/dacites (>68 wt.%) are separated from the andesites (<60 wt.%) by a gap in silica content indicating their formation through upper crustal anatexis with only heat supplied by the basaltic magma. On the other hand, partially melted siltstone xenoliths in enstatite-bearing basalts suggest that the enstatite-andesites originated through mixing of the upper crust with basaltic magma, crystallizing orthopyroxene at a pressure-temperature of ∼3 kb/1150 °C. In contrast, the northwestern sector of the RVP is devoid of felsic-intermediate rocks, and the volcaniclastic rocks are predominantly mafic (basaltic) in composition. Here, the presence of fine-grained tuffs, tuff breccia containing sideromelane shards and quenched texture, welded tuff breccia, peperite, shale/mudstone and oolite substantiates a subaqueous environment. Based on these observations, we conclude that the early phase of Rajmahal volcanism occurred under predominantly subaqueous conditions. The presence of grey and black shale/mudstone in the lower one-third of the succession across the entire Rajmahal basin provides unequivocal evidence of a shallow-marine continental shelf-type environment. Alignment of the Rajmahal eruptive centers with a major N–S mid-Neoproterozoic lineament and the presence of a gravity high on the RVP suggest a tectonic control for the eruption of melts associated with the Kerguelen plume that was active in a post-Gondwana rift between India and Australia-Antarctica. Peer-reviewed Publisher Version Article in Journal/Newspaper Antarc* Antarctica University of Leicester: Leicester Research Archive (LRA) Kerguelen Indian Geoscience Frontiers 8 4 809 822 |
institution |
Open Polar |
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University of Leicester: Leicester Research Archive (LRA) |
op_collection_id |
ftleicester |
language |
English |
description |
The late Aptian (118–115 Ma) continental flood basalts of the Rajmahal Volcanic Province (RVP) are part of the Kerguelen Large Igneous Province, and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin. The lower one-third of the Rajmahal volcanic succession contains thin layers of plant fossil-rich inter-trappean sedimentary rocks with pyroclasts, bentonite, grey and black shale/mudstone and oolite, whereas the upper two-thirds consist of sub-aerial fine-grained aphyric basalts with no inter-trappean material. At the eastern margin and the north-central sector of the RVP, the volcanics in the lower part include rhyolites and dacites overlain by enstatite-bearing basalts and enstatite-andesites. The pyroclastic rocks are largely felsic in composition, and comprise ignimbrite as well as coarse-grained tuff with lithic clasts, and tuff breccia with bombs, lapilli and ash that indicate explosive eruption of viscous rhyolitic magma. The rhyolites/dacites (>68 wt.%) are separated from the andesites (<60 wt.%) by a gap in silica content indicating their formation through upper crustal anatexis with only heat supplied by the basaltic magma. On the other hand, partially melted siltstone xenoliths in enstatite-bearing basalts suggest that the enstatite-andesites originated through mixing of the upper crust with basaltic magma, crystallizing orthopyroxene at a pressure-temperature of ∼3 kb/1150 °C. In contrast, the northwestern sector of the RVP is devoid of felsic-intermediate rocks, and the volcaniclastic rocks are predominantly mafic (basaltic) in composition. Here, the presence of fine-grained tuffs, tuff breccia containing sideromelane shards and quenched texture, welded tuff breccia, peperite, shale/mudstone and oolite substantiates a subaqueous environment. Based on these observations, we conclude that the early phase of Rajmahal volcanism occurred under predominantly subaqueous conditions. The presence of grey and black shale/mudstone in the lower one-third of the succession across the entire Rajmahal basin provides unequivocal evidence of a shallow-marine continental shelf-type environment. Alignment of the Rajmahal eruptive centers with a major N–S mid-Neoproterozoic lineament and the presence of a gravity high on the RVP suggest a tectonic control for the eruption of melts associated with the Kerguelen plume that was active in a post-Gondwana rift between India and Australia-Antarctica. Peer-reviewed Publisher Version |
format |
Article in Journal/Newspaper |
author |
Ghose, Naresh C. Chatterjee, Nilanjan Windley, Brian F. |
spellingShingle |
Ghose, Naresh C. Chatterjee, Nilanjan Windley, Brian F. Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite |
author_facet |
Ghose, Naresh C. Chatterjee, Nilanjan Windley, Brian F. |
author_sort |
Ghose, Naresh C. |
title |
Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite |
title_short |
Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite |
title_full |
Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite |
title_fullStr |
Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite |
title_full_unstemmed |
Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite |
title_sort |
subaqueous early eruptive phase of the late aptian rajmahal volcanism, india: evidence from volcaniclastic rocks, bentonite, black shales, and oolite |
publisher |
Elsevier on behalf of China University of Geosciences (Beijing) |
publishDate |
2016 |
url |
http://www.sciencedirect.com/science/article/pii/S1674987116300639 http://hdl.handle.net/2381/38056 https://doi.org/10.1016/j.gsf.2016.06.007 |
geographic |
Kerguelen Indian |
geographic_facet |
Kerguelen Indian |
genre |
Antarc* Antarctica |
genre_facet |
Antarc* Antarctica |
op_relation |
Geoscience Frontiers, 2016, in press 1674-9871 http://www.sciencedirect.com/science/article/pii/S1674987116300639 http://hdl.handle.net/2381/38056 doi:10.1016/j.gsf.2016.06.007 |
op_rights |
Copyright © the authors, 2016. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. |
op_rightsnorm |
CC-BY-NC-ND |
op_doi |
https://doi.org/10.1016/j.gsf.2016.06.007 |
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