Chapter 5.4b Marie Byrd Land and Ellsworth Land: petrology

Author:

Panter K. S.1ORCID,Wilch T. I.2,Smellie J. L.3,Kyle P. R.4ORCID,McIntosh W. C.5ORCID

Affiliation:

1. School of Earth, Environment and Society, Bowling Green State University, Bowling Green, OH 43403, USA

2. Department of Geological Sciences, Albion College, Albion, MI 49224, USA

3. School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK

4. Department of Earth and Environmental Sciences, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA

5. New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, Socorro, NM 87801, USA

Abstract

AbstractIn 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 elevated87Sr/86Sriratios. Most basalts are silica-undersaturated and enriched in incompatible trace elements (e.g. La/YbN>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/YbN<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 (206Pb/204Pb >20) materials. Geophysical studies indicate a deep thermal anomaly beneath central Marie Byrd Land, suggesting a plume influence on volcanism and tectonism.

Publisher

Geological Society of London

Subject

Geology

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