Mineral chemistry of the Qitianling granitoid and the Furong tin ore deposit in Hunan Province, South China: implication for the genesis of granite and related tin mineralization

Authors: Zhao, Kui-Dong; Jiang, Shao-Yong; Jiang, Yao-Hui; Wang, Ru-Chen

Source: European Journal of Mineralogy, Volume 17, Number 4, August 2005 , pp. 635-648(14)

Publisher: E. Schweizerbart'sche Verlagsbuchhandlung

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Abstract:

The Qitianling granitic stock is a stanniferous granite located in Hunan Province, China. Recently, the Furong tin ore deposit was found in this stock, with a tin reserve of approximately 600,000 tons. The main rock-forming minerals including amphibole, biotite, plagioclase and ore minerals including cassiterite and rutile were analysed chemical compositions by electron microprobe. The biotite is Fe-rich annite, and has high Ti and Cl concentration. The biotite has high Fe³⁺/(Fe²⁺+Fe³⁺) ratios and the oxygen fugacity calculated by biotite compositions is above Ni-NiO (NNO), and near the Fe₂O₃-Fe₃O₄ (MH). The amphiboles are ferropargasite and ferro-edenite hornblende. The pressure of the granite estimated by Al-in-hornblende barometer is 3.6 ± 0.9 kbar. An amphibole-plagioclase thermometry and a semiquantitative hornblende thermometer yield a forming temperature of 750 sim

820°C. The chlorite from the orebody has negligible K₂O, Ti₂O, F, and Cl, but shows similar Fe/(Fe+Mg) ratios with amphibole and biotite. Cassiterite is observed closely associated with rutile disseminated in chlorite alteration veins and envelopes. The ore-forming temperature is estimated to be 290 sim

405°C from chlorite geothermometry.

The Qitianling granite contains Sn-rich hornblende and biotite, and shows a high oxygen fugacity for the magma, which is slightly different from the common S-type stanniferous granites worldwide. Fractional crystallization of the magma and tin deposition directly from exsolved magmatic-hydrothermal fluids may not be the major mechanism for the tin mineralization in this deposit. Instead, we suggest that post-magmatic hydrothermal alteration of the granite may have released tin and other metals (e.g., Ti) from the Sn-bearing biotite and hornblende in the granite. Then cassiterite and rutile precipitated together with chlorite when the physical and chemical condition of the Sn- and Ti-rich fluids changed.

Keywords: GRANITE; TIN DEPOSIT; OXYGEN FUGACITY; CHLORITIZATION; SOUTH CHINA

Document Type: Research article

DOI: http://dx.doi.org/10.1127/0935-1221/2005/0017-0635

Publication date: 2005-08-01

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