Geothermal profile and crust-mantle transition beneath east-central Queensland

Volcanology, xenolith petrology and seismic data

W. L. Griffin*, F. L. Sutherland, J. D. Hollis

*Corresponding author for this work

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Geothermobarometry of garnet granulite and garnet websterite xenoliths in basalts from numerous localities in east-central Queensland gives P-T points that fall along the geotherm previously defined for southeastern Australia. This elevated geotherm is ascribed to the advective transport of heat by Tertiary-Recent magmas ponded at the crust-mantle boundary. The lower crust in this region consists dominantly of mafic granulites, representing frozen basaltic melts and cumulates. Spinel lherzolite becomes a dominant rock type at depths of ca. 30 km, and persists, interlayered with pyroxenites, to depths of ca. 55 km. Seismic reflection profiles show a "layered lower crust" between depths of 20 and 36 km depth. The lithologically defined crust-mantle boundary lies within this zone, at least 6 km above the seismically defined Moho. This interpretation is consistent with the observed velocity (Vp) gradient downward through the layered zone. The constructed geotherm implies that the bottom of the lithosphere beneath eastern Australia is shallower than ca. 100 km. This makes it unlikely that the diamonds of eastern Australia are derived from local intrusions, unless these are > 200 Ma old.

Original languageEnglish
Pages (from-to)177-203
Number of pages27
JournalJournal of Volcanology and Geothermal Research
Volume31
Issue number3-4
DOIs
Publication statusPublished - 1987
Externally publishedYes

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