The origin of the world class tin-polymetallic deposits in the Gejiu district, SW China: constraints from metal zoning characteristics and ⁴⁰Ar-³⁹Ar geochronology

Cheng, Yanbo, Mao, Jingwen, Chang, Zhaoshan, and Pirajno, Franco (2013) The origin of the world class tin-polymetallic deposits in the Gejiu district, SW China: constraints from metal zoning characteristics and ⁴⁰Ar-³⁹Ar geochronology. Ore Geology Reviews, 53. pp. 50-62.

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Abstract

The Gejiu tin-polymetallic deposits in the Western Cathaysia Block of South China comprise the world's largest primary tin district, with a total resource of approximately 300 million metric ton ores, at an average grade of 1 wt percent Sn. Tin polymetallic mineralization occurs in five deposits and has four ore types, i.e., greisen, skarn, stratabound cassiterite-sulfide (mostly oxidized) and vein type ore. In each deposit the orebodies typically occur in an extensive hydrothermal system centered on a shallow Late Cretaceous granitoid cupola. Metal zoning is well developed both vertically and horizontally over the entire district, from W + Be + Bi ± Mo ± Sn ores inside granite intrusions, to Sn + Cu-dominated ores at intrusion margins and farther out to Pb + Zn deposits in the surrounding host carbonate. This zoning pattern is similar to that of other hydrothermal deposits in other parts of the world, indicating a close genetic relationship between magmatism and mineralization. In this paper, we dated thirteen mica samples from all types of mineralization and from the five deposits in the Gejiu district. The ages range from 77.4 ± 0.6 Ma to 953 ± 0.7 Ma and are similar to the existing zircon U-Pb age of the granitic intrusions (77.4 ± 2.5-85.8 ± 0.6), indicating a genetic relationship between the mineralization and the intrusions. Geological characteristics, metal zoning patterns and new geochronological data all indicate that the tin-polymetallic ores in the Gejiu district are hydrothermal in origin and are genetically related to the nearby granitic intrusions. It is unlikely that the deposits are syngenetic, as has been proposed in recent years.

Item ID: 28339
Item Type: Article (Research - C1)
ISSN: 1872-7360
Keywords: deposit geology, metal zoning, ⁴⁰Ar-³⁹Ar dating, Ore genesis, Gejiu
Funders: National Natural Science Foundation of China, Yunnan Tin Group
Projects and Grants: 40930419, 2010-04A
Date Deposited: 17 Jul 2013 05:33
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 @ 10%
84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840102 Copper Ore Exploration @ 60%
84 MINERAL RESOURCES (excl. Energy Resources) > 8401 Mineral Exploration > 840108 Zinc Ore Exploration @ 30%
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