Journal article

ARGON ISOTOPIC ZONING IN MANTLE PHLOGOPITE

D PHILLIPS, TC ONSTOTT

GEOLOGY | GEOLOGICAL SOC AMERICA | Published : 1988

Abstract

Incremental-heating and laser-probe 40 Ar/ 39 Ar analyses were performed on phlogopite extracted from a garnet-lherzolite mantle nodule entrained by the Precambrian (1200 Ma) Premier kimberlite, South Africa. The spatial resolution of the laser probe has enabled the characterization of argon isotopic zoning in a single phlogopite grain. An apparent age contour map records lower ages (1.2 Ga) along grain margins and high apparent ages up to 2.4 Ga) at the core. The latter ages are caused by excess argon contamination and subsequent partial diffusive loss, and have no age significance. Comparison with step-heating results indicates that argon spatial distributions inferred from in-vacuo step-h..

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University of Melbourne Researchers