Marie Byrd Land and Ellsworth Land: petrology

In Marie Byrd Land and Ellsworth Land 19 large polygenetic volcanoes and numerous smaller centres are exposed above the West Antarctic ice sheet along the northern flank of the West Antarctic rift system. The Cenozoic (36.7 Ma to active) volcanism of the Marie Byrd Land Volcanic Group (MBLVG) encomp...

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Bibliographic Details
Main Authors: K.S. Panter, T.I. Wilch, J.L. Smellie, P.R. Kyle, W.C. McIntosh
Format: Article in Journal/Newspaper
Language:unknown
Published: Geological Society of London 2020
Subjects:
Geology
FOS Earth and related environmental sciences
Antarctic
West Antarctic Ice Sheet
Byrd
Marie Byrd Land
Ellsworth Land
Antarc*
Ice Sheet
Online Access:https://dx.doi.org/10.6084/m9.figshare.c.5233171.v1
https://geolsoc.figshare.com/collections/Marie_Byrd_Land_and_Ellsworth_Land_petrology/5233171/1
Description
Summary:In Marie Byrd Land and Ellsworth Land 19 large polygenetic volcanoes and numerous smaller centres are exposed above the West Antarctic ice sheet along the northern flank of the West Antarctic rift system. The Cenozoic (36.7 Ma to active) volcanism of the Marie Byrd Land Volcanic Group (MBLVG) encompasses the full spectrum of alkaline series compositions ranging from basalt to intermediate (e.g. mugearite, benmoreite) to phonolite, peralkaline trachyte, rhyolite and rare pantellerite. Differentiation from basalt is described by progressive fractional crystallization; however, to produce silica-oversaturated compositions two mechanisms are proposed: (1) polybaric fractionation with early-stage removal of amphibole at high pressures and (2) assimilation–fractional crystallization to explain elevated 87 Sr/ 86 Sr i ratios. Most basalts are silica-undersaturated and enriched in incompatible trace elements (e.g. La/Yb N > 10) indicating small degrees of partial melting of a garnet-bearing mantle. Mildly silica-undersaturated and rare silica-saturated basalts, including tholeiites, are less enriched (La/Yb N <10), a result of higher degrees of melting. Trace elements and isotopes (Sr, Nd, Pb) reveal a regional gradient explained by mixing between two mantle components, subduction-modified lithosphere and HIMU-like plume ( 206 Pb/ 204 Pb >20) materials. Geophysical studies indicate a deep thermal anomaly beneath central MBL suggesting a plume influence on volcanism and tectonism.

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