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Does tungsten availability control the presence of tungsten in turbidite-hosted orogenic gold mineralization? Evidence from the meguma and Bendigo-Ballarat Terranes
journal contribution
posted on 2023-05-19, 18:57 authored by Cave, BJ, Ross LargeRoss Large, White, CE, McKnight, STurbidite-hosted orogenic Au deposits are commonly enriched in W, along with a variety of other trace elements. A mineralogical source for W has recently been shown in the Otago Schist of southern New Zealand (Cave et al. 2016), with detrital rutile in the metasedimentary rocks recrystallizing to metamorphic titanite and making W available to be mobilized from the rock mass. In this study, we investigate the availability of W through prograde metamorphic mineral recrystallization in two additional turbidite-hosted orogenic Au provinces, one containing orogenic Au mineralization with associated subordinate W (Meguma Terrane, Canada), and the other containing orogenic Au mineralization without associated W (Bendigo-Ballarat Terrane, Australia). This was undertaken to assess whether W availability during prograde metamorphism is a key process in controlling the presence of W in turbidite-hosted orogenic Au mineralization. Like the Otago Schist, in both terranes detrital rutile is identified as being the most important host mineral for W in the lowest metamorphic grade rocks, and its prograde metamorphic recrystallization (to ilmenite) makes significant amounts of W available for mobilization (0.65 and 1.85 g of W per tonne of rock from the Goldenville and Halifax groups of the Meguma Terrane, respectively, and 0.16 g of W per tonne of rock from the Castlemaine Group of the Bendigo-Ballarat Terrane). This release of W in the Meguma Terrane is likely the source of W in these orogenic Au deposits. The lack of W in the orogenic Au deposits of the Bendigo-Ballarat Terrane suggests that W availability is not the only process controlling the presence of W minerals in turbidite-hosted orogenic Au mineralization. Alternatively, it might reflect a lower greenschist facies metasedimentary (Castlemaine Group) source for these deposits (i.e., a lower metamorphic grade source than the rutile to ilmenite conversion), as has been previously suggested.
History
Publication title
Canadian MineralogistVolume
55Issue
6Pagination
973-999ISSN
0008-4476Department/School
School of Natural SciencesPublisher
Mineralogical Assoc CanadaPlace of publication
Po Box 78087, Meriline Postal Outlet, 1460 Merivale Rd, Ottawa, Canada, Ontario, K2E 1B1Rights statement
Copyright 2017 Mineralogical Association of CanadaRepository Status
- Restricted