Clarke, Gavin W. (2009) Element partitioning in the formation of a microgranite sill with associated Mo +/- W deposits in the Herberton district, North-east Queensland, Australia. In: Proceedings of the 10th Biennial Meeting of the the SGA 2009 (1) pp. 210-212. From: 10th Biennial Meeting of the SGA 2009, 17-20 August 2009, Townsville, QLD, Australia.

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Abstract

Within the Herberton district of N.E. Queensland, the Cattle Camp Granite pluton contains a texturally zoned sill that grades upwards from porphyritic microgranite, through aplite, to (pegmatitic) miarolitic granophyre wherein Mo +/- W mineralised quartz pods/pies/veins occur intermittently. This textural zoning signifies the upward accumulation of an aqueous fluid phase in the residual melt which would have promoted crystallisation from the base upwards. Geochemical trends for the most part suggest crystal-melt fractionation was the principal process controlling elemental distribution. However, trend reversals evident in progression from the usual apical miarolitic granophyre to that which lies immediately adjacent a mineralised quartz pod/pipe imply other processes were also involved. The presence of fluorine-bearing minerals, coupled with the distribution of fluorophile elements, particularly HREE, indicate fluorine enrichment in the emergent aqueous fluid phase exerted a strong influence on the chemical compositions of granite forms crystallised, and of the components concentrated in the associated mineralised quartz pods/pipes/veins.

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