Petrogenesis of Mesoproterozoic K-rich granitoids, southern Mt Angelay igneous complex, Cloncurry district, northwest Queensland

Author： Mark G.

Publisher： Taylor & Francis Ltd

ISSN： 0812-0099

Source： Australian Journal of Earth Sciences, Vol.46, Iss.6, 1999-12, pp. : 933-949

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Abstract

The K‐rich granitoids of the southern Mt Angelay igneous complex belong to the younger phases of the Williams and Naraku Batholiths ( 2 the granitoids vary from alkaline to subalkaline, and exhibit a decrease in TiO 2 , Al 2 O 3 , Fe 2 O 3 *, MnO, MgO, CaO, P 2 O 5 , Cu, Sr, Zr, LREE and Eu, with an increase in Na 2 O, K 2 O, Rb, Pb, Th, U, Y and HREE. This suite of relatively oxidised granitoids ( 960°C) and foliated felsic (>900°C) granitoids formed zones of mingled and mixed monzonite and quartz monzonite to monzogranite containing abundant rapakivi K‐feldspar. These intrusions are interpreted to have been derived from source rocks of different compositions, and probably by different degrees of partial melting. The unfoliated felsic granitoids are considered to represent the fractionated equivalents of older foliated felsic granitoids. All granitoids possess a Sr‐depleted and Y‐undepleted signature, which suggests that the source material probably contained plagioclase and no garnet, restricting magma production to