Peraluminous Sapphirine from the Aileron District, Arunta Block, Central Australia

R. G. Warren and B. J. Hensen
Bureau of Mineral Resources, GPO Box 378, Canberra, 2601, Australia
Department of Applied Geology, University of New South Wales, Kensingston, 2033, Australia

Abstract: Specimens collected from a small lens of phlogopite-rich rock in the granulite-facies terrain of the Arunta Block, central Australia, have unusual bulk compositions and mineral assemblages. One sample consists of phlogopite enclosing blue spinel (mg 96) with minute granules of corundum and sapphirine at the margins; a second of phlogopite enclosing porphyroblasts of corundum and peraluminous sapphirine. In the first the sapphirine is close to the 7 : 9 : 3 composition; in the other it is markedly peraluminous, e.g. (Mg1.628Fe0.028)Al4.714Si0.636O10, intermediate between the 7 : 9 : 3 and 3 : 5 : 1 members. The texture suggests that this sapphirine is a stable phase in equilibrium with eastonitic phlogopite and corundum. The very potassic, very magnesian bulk composition of the rocks is attributed to potassium metasomatism of a protolith consisting of magnesian chlorite and quartz.

Keywords: sapphirine • phlogopite • corundum • Arunta Block • Australia

Mineralogical Magazine; September 1987 v. 51; no. 361; p. 409-415; DOI: 10.1180/minmag.1987.051.361.07
© 1987, The Mineralogical Society
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