Geochemistry of cassiterite and its inclusions and exsolution products from tin and tungsten deposits in Portugal

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Authors:Neiva, A. M. R.
Author Affiliations:Primary:
University of Coimbra, Department of Earth Sciences, Coimbra, Portugal
Volume Title:Canadian Mineralogist
Source:The Canadian Mineralogist, Vol.34(Part 4), p.745-768. Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada. ISSN: 0008-4476
Publication Date:1996
Note:In English. 51 refs.; illus., incl. 11 tables, geol. sketch map
Summary:Euhedral cassiterite from Sn-bearing granitic pegmatites and stanniferous quartz veins in Portugal show alternating sequences of darker and lighter zones. The darker zones are strongly pleochroic, oscillatorily zoned and have more Nb, Ta and Fe than the lighter zone, which are virutally pure SnO2. Darker zones show exsolved columbite-tantalite and ixiolite, rarely ferrotapiolite, rutile and, locally, ilmenite, which are less abundant in the lighter zones. Rare inclusions of columbite-tantalite have combined Ti, Sn and W contents less than in the exsolved columbite-tantalite. Cassiterite from W-Sn-bearing quartz veins is generally zoned, and has inclusions of rutile and locally of ilmenite. Exsolved rutile has similar or higher combined contents of Nb, Ta, Sn, W, Fe and Mn than included rutile. Euhedral to massive cassiterites from a volcanogenic deposit are slightly pleochroic, their colour deepening from yellow to dark brown with increasing Fe content; such cassiterite is devoid of inclusions and exsolution products. [R.A.H.]
Subjects:Cassiterite; Columbite; Electron microscopy; Exsolution; Framework silicates; Geochemistry; Granites; Igneous rocks; Ilmenite; Inclusions; Ixiolite; Metals; Niobates; Ordovician; Oxides; Paleozoic; Pegmatite; Plutonic rocks; Quartz; Rutile; Silica minerals; Silicates; Silurian; Tantalates; Tantalite; Tapiolite; Tungstates; Tungsten; Veins; Wolframite; Zoning; Europe; Iberian Peninsula; Portugal; Southern Europe; Neves Corvo Mine; Niobotantalates
Abstract Numbers:97M/1967
Record ID:2000027832
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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