1992/01/01 by S. D. Weaver, C.J. Adams, R. J. Pankhurst +1 · 2 citations
Earth and Planetary Sciences · Computer Science · #Geological and Geochemical Analysis #Geochemistry and Geologic Mapping #Geochemistry and Elemental Analysis #Geology #Geochemistry #Monazite #Zircon #Pluton #Continental arc #Biotite #Peralkaline rock #Magmatism #Batholith #Volcanic rock #Paleontology #Volcano #Quartz
paper · doi:10.1017/s0263593300007963
openalex publication_date 1992/01/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
ABSTRACT 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 (Ce N /Yb N = 8·4), to flat REE patterns (Ce N /Yb N = 1·1) with large negative Eu anomalies (Eu/Eu* = 0·02). Initial 87 Sr/ 86 Sr ratios are 0·7116-0·7206 and initial ε Nd 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.