Journal
LITHOS
Volume 119, Issue 1-2, Pages 47-60Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.lithos.2010.04.013
Keywords
Silicic magmatism; Daly gap; Fractionation; Crustal melting; End-Guadalupian mass extinction; Emeishan large igneous province
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Funding
- Natural Science Foundation of China [40721063]
- CAS/SAFEA [KZCX2-YW-t004]
- National Science Council of Taiwan
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The Emeishan large igneous province in SW China comprises a bimodal mafic-siliac suite with the silicic rocks occurring at the uppermost part of the thick lava sequence The silicic rocks have an age of 257263 Ma, and are thus roughly coeval with the Guadalupian-Loping (G-L) boundary event. Most silicic rocks (trachyte and rhyolite) from the Emeishan province have rather uniform epsilon(Nd) values ( +1 to +2 9) that are comparable with the uncontaminated high-Ti basalts. This fact and the remarkably narrow ranges of incompatible element ratios (e.g. Zr/Nb) of the basalt-silicic suite indicate a genetic relationship between basalt and silicic members. The significant difference between the Emeishan rocks and the experimental melts of hydrated basaltic crust, suggests the fractional crystallization of basaltic magma, rather than crustal melting, as the major petrogenetic process for the formation of silicic rocks Indeed, their major and trace element trends can be modeled by fractionation of the observed mineral phases (feldspar, clinopyroxene, Fe-Ti oxide and apatite). In contrast to the virtually closed system differentiation processes associated with trachytes, the rhyolites may have experienced interaction with upper crustal material during ascent The geochemical characteristics and recent assessment of timing of the Emeishan volcanism suggest the Emeishan rhyolites as the potential source of the widespread clay bed at the G-L boundary in south China This enhanced the causal link between the Emeishan eruption and the end-Guadalupian biological crisis. (C) 2010 Elsevier B.V. All rights reserved.
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