rare element pegmatites gsod20 feb20 96x200 · 2020. 3. 16. · Ÿrare-element pegmatites have...

www.dmirs.wa.gov.au Geological Survey of Western Australia Government of Western Australia Department of Mines, Industry Regulation and Safety RARE-ELEMENT PEGMATITES FEBRUARY 2020 Rare-element pegmatites are a new addition to the GSWA Mineral Systems Atlas Ÿ This poster provides a mineral systems analysis for rare-element pegmatites Ÿ Introduction Rare-element pegmatites are important hosts for Li, Cs, and Ta mineralization in Western Australia, with examples including the Greenbushes, Pilgangoora, and Wodgina deposits. What are rare-element pegmatites? They are further divided into: Ÿ ¡ Lithium–Cesium–Tantalum (LCT) pegmatites The simplest classification scheme divides granitic pegmatites Ÿ into common pegmatites and rare-element pegmatites ¡ Niobium–Yttrium–Fluorine (NYF) pegmatites Rare-element pegmatites have anomalous contents of Be, Li, Ÿ Ta, Sn, and Cs Pegmatite occurrences in the WAROX field observational Ÿ database show their wide distribution and correspondence to greenstone belts (Fig. 1) Rare-element pegmatites represent <1% of all pegmatites Ÿ Pegmatites in Western Australia Fertile granitic magmas are a source of fluids and Ÿ metals (Fig. 2) Fertile granites are identified by the presence of fluorite, Ÿ cordierite, tourmaline, garnet, white potassium feldspar and green muscovite Fertile granites (source) S-type granites that undergo extreme fractionation are Ÿ enriched in Li, Cs, Ta, Rb, Sn, F, Be, Nb, Ga, Fe, Ti and REE (Fig. 3) Pegmatites are opportunistic and use a variety of structural pathways, including faults, fractures, foliation or bedding planes in country rocks Magma pathways (structural architecture) Trapping conditions for mineralization Cooling and chemical diffusion of fractionating granitic Ÿ melts result in rapid crystallization (over days to years) Pegmatites located within 10 km of fertile granites, and Ÿ particularly roof zones, are more favourable sites (Fig. 2) Figure 1. Pegmatites and operating mines Figure 2. Schematic profile shows pegmatite zonation patterns around a fertile granite Figure 3. Fertile granites have a high fractionation index, identified by their high Ta/Nb ratios For more information, contact: Paul Duuring ([email protected]) Mt Cattlin Mt Cattlin Mt Cattlin Operating mines (MINEDEX) Ta/Nb 0.004 – 0.090 0.090 – 0.120 0.120 – 0.200 0.200 – 53.244 Granite fertility (WACHEM) Greenbushes Greenbushes Greenbushes Mt Marion Mt Marion Mt Marion Sinclair Sinclair Sinclair Pilgangoora Pilgangoora Pilgangoora Operating mines (MINEDEX) Rare-element pegmatites (MINEDEX) All pegmatites (WAROX) Mt Marion Mt Marion Mt Marion Sinclair Sinclair Sinclair Greenbushes Greenbushes Greenbushes Mt Cattlin Mt Cattlin Mt Cattlin Pilgangoora Pilgangoora Pilgangoora

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www.dmirs.wa.gov.au Geological Survey ofWestern AustraliaGovernment of Western AustraliaDepartment of Mines, Industry Regulation and Safety

RARE-ELEMENTPEGMATITES

FEBRUARY 2020

Rare-element pegmatites are a new addition to the GSWA Mineral Systems AtlasŸThis poster provides a mineral systems analysis for rare-element pegmatitesŸ

IntroductionRare-element pegmatites are important hosts for Li, Cs, and Ta mineralization in Western Australia, with examples including the Greenbushes, Pilgangoora, and Wodgina deposits.

What are rare-element pegmatites?

They are further divided into:Ÿ¡ Lithium–Cesium–Tantalum (LCT) pegmatites

The simplest classification scheme divides granitic pegmatites Ÿinto common pegmatites and rare-element pegmatites

¡ Niobium–Yttrium–Fluorine (NYF) pegmatites

Rare-element pegmatites have anomalous contents of Be, Li, ŸTa, Sn, and Cs

Pegmatite occurrences in the WAROX field observational Ÿdatabase show their wide distribution and correspondence to greenstone belts (Fig. 1)

Rare-element pegmatites represent