Compositional characteristics and existing forms of major, trace and rare-earth elements in cassiterite, Dupangling tin ore field, Guangxi

Abstract

Trace elements in cassiterite, including Ta, W, Fe, Mn, Ti, Zr, V, Sc, Si, Al, In, Ga, Ge, Be, Bi, Ag, Sb, As, Cu, Pb, Zn, Co and REE, have been studied by many workers (Shan Zhenhua et al., 1988; Huang Zhou Tianren et al., 1987; Wu Qingsheng et al., 1988; Hu Zening, 1988, Li Zhongqing 1988 Mingzhi et al., 1988; Wang Lihua et al., 1988; Liu Kanghuai, 1990). Up to now, however, most of the previous studies are concerned with trace-element variations in cassiterites of different occurrences and colors from different types of ore deposits, Data concerning the modes of occurrence of these trace elements are rare, except for the contention that Nb-Ta, Fe2+-Mn-Fe3+ and W-Fe3+ may substitute isomorphously for Sn as pointed out by Zhou Tianren et al. (1987) and Moller et al. (1988). In this paper we are concerned with the compositional characteristics as well as the modes of occurrence of trace elements in cassiterites from quartz veins and greisens in the Dupangling tin field, Guangxi, based on multivariate statistical analyses. Tin mineralization in the Dupangling area is found associated with the medium-to fine-grained protolithionite-albite granite (γ 5 2b) and its outer contacts. Cassiterite occurs, with wolframite, both in quartz veins in the contact and in greisens within the granite. Spatially, greisens become dominant over quartz veins in going from the contact to the interior of the granite and with increasing depth. The greisens are of various shapes. The vein-shaped and the sheet-shaped greisens at the top of the granite are rich in quartz and the chambered greisens always constitute rich ores and contain abundant topaz or mica, Genetically, Sn, W mineralizations associated with the protolithionite-albite granite (γ 5 2b) are considered to have been formed from fluid melt derived from the ore-forming magma responsible for the granite (γ 5 2b).