Clumped isotope geochemistry of carbonatites in the north-western Deccan igneous province: Aspects of evolution, post-depositional alteration and mineralisation

Fosu, BR and Ghosh, P and Viladkar, SG (2020) Clumped isotope geochemistry of carbonatites in the north-western Deccan igneous province: Aspects of evolution, post-depositional alteration and mineralisation. In: Geochimica et Cosmochimica Acta, 274 . pp. 118-135.

	PDF geo_cos_act_274_118-135_2020.pdf - Published Version Restricted to Registered users only Download (4MB) | Request a copy
Preview	PDF 1-s2.0-S0016703720300326-mmc1.pdf - Published Supplemental Material Download (634kB) | Preview
	Microsoft Excel 1-s2.0-S0016703720300326-mmc2.xls - Published Supplemental Material Download (170kB)

Abstract

Carbonatites crystallise along a wide range of solidus temperatures and are commonly affected by post-magmatic textural re-equilibration and diagenesis. Further insights into the formation and modification of carbonatites are provided using carbon, oxygen and clumped isotope (�47) data of rocks from spatially associated Amba Dongar and Siriwasan alkaline complexes in the north-western Deccan igneous province, India. We derive apparent equilibrium blocking temperatures to help constrain the thermal evolution of the different rock types found within the alkaline complexes in a petrographic context. The apparent temperatures for the carbonatites are significantly low but are consistent with reports on other global carbonatites and model predictions. Rapidly cooled Oldoinyo Lengai natrocarbonatite yielded similar low temperatures, even in the absence of bulk isotopic alteration. The isotopic proxies and petrographic observations favour both isotopic exchange reactions and diagenesis in altering �47 values in calciocarbonatites. Diagenetic reactions are however strongly favoured, as secondary calcites in nephelinites and ferrocarbonatites record much lower temperatures than in the calciocarbonatites, highlighting the effect of fluids and diagenetic reactions in 13Csbnd18O bond ordering in carbonatites. Variations in the CsbndO isotope data reveal the coupling of fractional crystallisation and post-magmatic fluid-rock interactions on bulk rock composition. After emplacement, the resetting of clumped isotope signatures in carbonatites is facilitated by post-magmatic processes in both open and closed systems. © 2020 Elsevier Ltd

Item Type:	Journal Article
Publication:	Geochimica et Cosmochimica Acta
Publisher:	Elsevier
Additional Information:	The copyright of this article belongs to Elsevier
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences Division of Mechanical Sciences > Divecha Centre for Climate Change
Date Deposited:	10 Mar 2020 08:00
Last Modified:	10 Mar 2020 08:00
URI:	http://eprints.iisc.ac.in/id/eprint/64793

Actions (login required)

View Item