Granites of Edward VII Peninsula, Marie Byrd Land: anorogenic magmatism related to Antarctic-New Zealand rifting

Weaver, S.D.; Adams, C.J.; Pankhurst, R.J.; Gibson, I.L.. 1992 Granites of Edward VII Peninsula, Marie Byrd Land: anorogenic magmatism related to Antarctic-New Zealand rifting. Transactions of the Royal Society of Edinburgh: Earth Sciences, 83 (1-2). 281-290. https://doi.org/10.1017/S0263593300007963

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Abstract/Summary

Syenogranites and monzogranites of Edward VII Peninsula, Marie Byrd Land, represent magmatism associated with continental rifting and the separation of New Zealand from W Antarctica in the mid-Cretaceous. These coarse-grained, leucocratic, subsolvus biotite granites occur as five small plutons cutting Lower Palaeozoic metasediments. Petrographic features include the predominance of microcline perthite over albite, bipyramidal smoky quartz, red-brown biotite and accessory ilmenite, zircon, apatite, monazite and fluorite. Enclaves are absent and miarolitic cavites are rare.The granites are a weakly peraluminous, potassic, and highly fractionated suite with high concentrations of Rb, Nb, Y, HREE and F in the most evolved compositions. REE patterns vary from LREE-enriched (CeN/YbN = 8·4), to flat REE patterns (CeN/YbN = 1·1) with large negative Eu anomalies (Eu/Eu* = 0·02). Initial 87Sr/86Sr ratios are 0·7116-0·7206 and initial εNd values are −5·5 to −7·7. Generalised fractionation trends for the suite are explicable in terms of the modal mineralogy. Monazite crystallisation exerted a predominant control on LREE concentrations.The geochemistry of the Edward VII Peninsula granites suggests an infracrustal I-type source, and regionally available Devonian-Carboniferous I-type granodiorites and tonalites satisfy the isotopic constraints. The granites classify as A-type (preferred term A-subtype) and Within-Plate Granites on standard diagrams, but the least fractionated rocks clearly indicate the I-type, Volcanic Arc Granite geochemical signatures of their inferred crustal sources.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1017/S0263593300007963
ISSN:	0263-5933
Additional Keywords:	A-subtype, Cretaceous, fractionation trends, granodiorite-tonalite source, isotopes, I-type, monzogranite, petrogenesis, syenogranite
NORA Subject Terms:	Earth Sciences
Date made live:	25 Jan 2018 11:03 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/519103

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