Compositional Characteristics and Existing Forms of Major, Trace and Rare-earth Elements in Cassiterite, Dupangling Tin Ore Field, Guangxi

Trace elements in cassiterite, including Ta, W, Fe, Mn, Ti, Zr, V, Sc, Si, kl, In, Ga, Ge, Be,Bi, Ag, Sb, As, Cu, Pb, Zn, Co and REE, have been studied by many workers (Shan Zhenhua etal., 1988; Huang Zhou Tianren et al., 1987; Wu Qingsheng et al., l988; Hu Zening, 1988, Li Zhong-qing 1988 MingZhi et al.,1988; Wang Lihua et al., 1988, Liu Kanghuai, 1990). Up to now, however,most of the previous studiesareconcerned with tracoelement variations in cassiterites of diffirent occur-rences and colors from diffirent types of ore deposits, Data concerning the modes of occurrence of’ these trace elements are rare, except for the contention that Nb-Ta, F.2+-M.-F.3+ and W-F.3+ maysubstitute 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 compositionaI characterishcs as well as the modes ofoccurrence of trace elements in cassiterites from quartz veins and greisens in the Dupangling tin field,Guangxi, based on mu1tivariate statistical analys es.Tin mineralization in the Dupang1ing area is found associated with the medium-to fine-grainedprotolithionite-albite granite and its outer contacts. Cassiterite occurs, with wolframite, both inquartz veins in the contact and in greisens within the granite.’ ) Spatially, greisens become dominantover 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 thegranite are rich in quartz and the chambered greisens always constitute rich ores and contain abun-dant topaz or mica. Genetically, Sn, W ndneralizations associated with the protolithionite-albite gran-ite are considered to have been formed from fluid melt derived from the ore-forming magma re-sponsible for the granite