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Modelling basalt weathering at elevated CO2 concentrations: implications for terminal to post-magmatic rifting in the Deccan Traps, Kachchh, India

By
Kaushik Mitra
Kaushik Mitra
Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur 721 302, India
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Souvik Mitra
Souvik Mitra
Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur 721 302, India
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Saibal Gupta
Saibal Gupta
Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur 721 302, India
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Satadru Bhattacharya
Satadru Bhattacharya
Space Applications Centre, Indian Space Research Organization, Ahmedabad 380 015, India
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Prakash Chauhan
Prakash Chauhan
Space Applications Centre, Indian Space Research Organization, Ahmedabad 380 015, India
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Nirmala Jain
Nirmala Jain
Space Applications Centre, Indian Space Research Organization, Ahmedabad 380 015, India
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Published:
January 01, 2018

Abstract:

Deccan volcanism was synchronous with rifting along the west coast of India. Pre- and synmagmatic rifting has been widely reported in the Deccan Volcanic Province, but extension post-dating magmatism, and predating India–Eurasia collision, is less well known. A recent study in the Kachchh area of western India documented weathering of basalts to kaolinite at the base of Cenozoic rift basins, with rift flanks relatively less altered to smectites, and this was attributed to post-magmatic rifting. This study models basalt weathering under open- and closed-system conditions to simulate rainwater interacting with basalts either on topographical slopes (within rifts) or on flat-topped hills (flow tops). Both systems were modelled under pCO2 conditions ranging from low, present-day values to higher values more appropriate for the end-Cretaceous–early Paleocene time, after basalt emplacement. The results show that if pCO2 exceeded values of 10−2.5, basalts would be altered to kaolinite in both open and closed systems. Existing pCO2 estimates in the aftermath of Deccan volcanism fall below this value, implying that the differential basalt weathering was more likely to have been caused by terminal to post-magmatic rifting. This indicates that extensional tectonics along the Indian west coast in the Kachchh region continued even after cessation of Deccan volcanism.

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Geological Society, London, Special Publications

Large Igneous Provinces from Gondwana and Adjacent Regions

S. Sensarma
S. Sensarma
University of Lucknow, India
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B. C. Storey
B. C. Storey
University of Canterbury, New Zealand
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The Geological Society of London
Volume
463
ISBN electronic:
9781786203441
Publication date:
January 01, 2018

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