Magmas Erupted during the Main Pulse of Siberian Traps Volcanism were Volatile-poor

Sibik, Svetlana and Edmonds, Marie and Maclennan, John and Svensen, Henrik (2015) Magmas Erupted during the Main Pulse of Siberian Traps Volcanism were Volatile-poor. Journal of Petrology, 56 (11). pp. 2089-2116. ISSN Print ISSN 0022-3530 - Online ISSN 1460-2415 DOI 10.1093/petrology/egv064

[img]
Preview
Text
J. Petrology-2015-Sibik-2089-116.pdf - Published Version
Available under License Creative Commons Attribution.

Download (3MB) | Preview
Official URL: http://petrology.oxfordjournals.org/content/56/11/...

Abstract

The eruption of the Siberian Traps Large Igneous Province (SLIP) at the Permo-Triassic boundary was synchronous with environmental degradation and the largest known mass extinction in the geological record. The volatile emissions associated with these eruptions have been linked to the environmental change yet we understand little of their source and magnitude and how they varied with time. There are a number of possible sources for the volatiles that were emitted during the eruptions: the mantle (including metasomatized lithosphere), volatile-rich sediments (through metamorphism or direct assimilation) and the crustal basement. To assess the relative importance of these sources (with the exception of the metamorphic outgassing source), we have conducted a geochemical study of melt inclusions hosted by clinopyroxene in Siberian Traps low-Ti tholeiitic lavas and sills of the Khakanchansky, Ayansky and Khonnamakitsky Formations. The magmas were not emplaced into or erupted onto evaporite deposits, in contrast to samples studied previously. The trace element compositions of the melt inclusions are highly variable compared with the uniform whole-rocks, exhibiting a wide range of La/Yb ratios from 0·7 to 9·5. The melt geochemistry is consistent with relatively large degrees of partial melting of a dominantly peridotite mantle source. A negative Nb anomaly indicates a degree of crustal contamination, but there is no evidence for contamination by volatile-rich evaporites. Enrichment of some of the melts in large ion lithophile elements (Ba, Sr) indicates their interaction with a fluid. We suggest that, consistent with the observed depletion in other incompatible trace elements in the melt inclusions, the volatile concentrations in the melts were relatively low, and that subsequently the melts underwent variable degrees of degassing in the crust. Overall, the melts are more volatile-poor than those reported previously from the SLIP and were erupted after the first “pulse” of more volatile-rich magmas described by Sobolev et al. (2015). These volatile-poor magmas may have been widespread across the region during the Siberian Traps eruptions once a pyroxenite component in the mantle source had been exhausted.

Item Type: Article
Uncontrolled Keywords: 2015AREP; IA70
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
07 - Gold Open Access
Journal or Publication Title: Journal of Petrology
Volume: 56
Page Range: pp. 2089-2116
Identification Number: 10.1093/petrology/egv064
Depositing User: Sarah Humbert
Date Deposited: 28 Apr 2016 13:06
Last Modified: 22 Jul 2016 15:33
URI: http://eprints.esc.cam.ac.uk/id/eprint/3640

Actions (login required)

View Item View Item

About cookies