Geology and vein tin mineralization in the Dadoushan deposit, Gejiu district, SW China

Cheng, Yanbo, Mao, Jingwen, and Yang, Zongxi (2012) Geology and vein tin mineralization in the Dadoushan deposit, Gejiu district, SW China. Mineralium Deposita, 47 (6). pp. 701-712.

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Abstract

Vein-type tin mineralization in the Dadoushan deposit, Laochang ore field, Gejiu district, SW China, is predominantly hosted in Triassic carbonate rocks (Gejiu Formation) over cupolas of the unexposed Laochang equigranular granite intrusion. The most common vein mineral is tourmaline, accompanied by skarn minerals (garnet, diopside, epidote, phlogopite) and beryl. The main ore mineral is cassiterite, accompanied by minor chalcopyrite, pyrrhotite, and pyrite, as well as scheelite. The tin ore grade varies with depth, with the highest grades (similar to 1.2 % Sn) prevalent in the lower part of the vein zone. Muscovite ⁴⁰Ar-³⁹Ar dating yielded a plateau age of 82.7 ± 0.7 Ma which defines the age of the vein-type mineralization. Measured sulfur isotope compositions (δ³⁴S = -4.1 to 3.9 ‰) of the sulfides (arsenopyrite, chalcopyrite, pyrite, and pyrrhotite) indicate that the sulfur in veins is mainly derived from a magmatic source. The sulfur isotope values of the ores are consistent with those from the underlying granite (Laochang equigranular granite, -3.7 to 0.1 ‰) but are different from the carbonate wall rocks of the Gejiu Formation (7.1 to 11.1 ‰). The calculated and measured oxygen and hydrogen isotope compositions of the ore-forming fluids (δ¹⁸O(H₂O) = -2.4 to 5.5 ‰, δD = -86 to -77 ‰) suggest an initially magmatic fluid which gradually evolved towards meteoric water during tin mineralization.

Item ID: 23645
Item Type: Article (Research - C1)
ISSN: 0026-4598
Keywords: tin deposits, Dadoushan, Gejiu, China
Date Deposited: 10 Oct 2012 05:27
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040307 Ore Deposit Petrology @ 100%
SEO Codes: 84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840199 Mineral Exploration not elsewhere classified @ 100%
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