Polyphase scheelite and stanniferous silicates in a W-(Sn) skarn close to Felbertal tungsten mine, Austria

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Marco E. Ciriotti
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Polyphase scheelite and stanniferous silicates in a W-(Sn) skarn close to Felbertal tungsten mine, Austria

Messaggio da Marco E. Ciriotti » sab 06 lug, 2019 11:52

Prossima pubblicazione.

Referenza:
▪ Alexander Ordosch, A., Raith, J.G., Schmidt, S., Aupers, K. (2019): Polyphase scheelite and stanniferous silicates in a W-(Sn) skarn close to Felbertal tungsten mine, Eastern Alps. Mineralogy and Petrology, 113, (in press).

Abstract:
The scheelite exploration target Messelingscharte (Eastern Tyrol, Austria) is located in vicinity of the world-class Felbertal tungsten deposit. W-(Sn) mineralisation occurs in Early Palaeozoic amphibolites (Basal Amphibolite unit) in the Tauern Window of the Eastern Alps. The most important mineralisation type is a Sn-bearing clinozoisite-scheelite skarn of pre-Alpine (Variscan?) age. It occurs as metre-sized irregular pods within amphibolites and amphibole schists. It is composed of major clinozoisite, quartz, plagioclase and scheelite with minor and accessory titanite, calcite and chlorite. Bulk chemical analyses reveal high concentrations of the granitophile elements W (≤7.74 wt% WO3), Sn (≤1254 ppm SnO2), Be (≤41 ppm) and base metals (Cu, Pb, Zn; ∑ ≤ 2500 ppm) in the skarn rock. Three scheelite types are distinguished based on micro-textures, zoning, Mo-content and UV- fluorescence. They show intriguing similarities to scheelite from the Felbertal tungsten deposit where pre-Alpine Mo-bearing scheelite was apparently overprinted by two stages of metamorphism. The unique feature of the investigated W-(Sn) skarn is the association of scheelite with Sn-bearing silicates. Stanniferous clinozoisite and stanniferous titanite were identified as the main Sn carriers (clinozoisite ≤3.00 wt% SnO2; titanite ≤6.48 wt% SnO2); both minerals evidence metamorphic re-crystallisation. Substitution of (Al, Fe)3+ by (Sn, Ti)4+ in clinozoisite is coupled with incorporation of Fe2+. The skarn formed by interaction of fluids of likely magmatic-hydrothermal origin with metabasites. The clinozoisite-dominated calc-silicate rocks are interpreted as a metamorphosed distal W-(Sn) skarn.
Marco E. Ciriotti

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