Age and geochemistry of granites in Gejiu area, Yunnan province, SW China: constraints on their petrogenesis and tectonic setting

Cheng, Yanbo, and Jingwen, Mao (2010) Age and geochemistry of granites in Gejiu area, Yunnan province, SW China: constraints on their petrogenesis and tectonic setting. Lithos, 120 (3-4). pp. 258-276.

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Abstract

Gejiu is one of the largest polymetallic tin ore districts in the world. Located at the westernmost end of the South China tungsten–tin province (or Nanling tungsten–tin province), it is a granite-related (Gejiu granite) magmatic-hydrothermal system. Nine samples from two phases of Gejiu granitic intrusions have been analyzed by SHRIMP and/or LA-ICPMS zircon U–Pb techniques, yielding ages ranging from 77.4 ± 2.5 Ma to 85.0 ± 0.85 Ma. Whole rock analysis shows that both phases are high-K and alkali-rich granites and their ACNK values fall mainly into a small range of 1.0–1.1. Moreover, Harker diagrams indicate that granites experienced strong fractional crystallization during magmatic evolution. Most granites display relative enrichment in LREE and strong Eu depletion. The whole rock average (εNd(t)) values of the Gejiu granites vary from − 9.3 to − 6.9, whereas a range of − 8.12 < (εHf(t)) < 1.21 is defined by magmatic zircons. Sr–Nd–Hf isotope data indicate that the granites have been mainly derived from crustal melts with minor input of mantle component. Two stage Nd and Hf model ages, together with isotopic characteristics, indicate that the Gejiu granite magmas were possibly derived from partial melting of Mesoproterozoic continental crust, with minor input of mantle-derived melts, followed by extensive fractional crystallization.

Item ID: 29021
Item Type: Article (Research - C1)
ISSN: 1872-6143
Keywords: Gejiu granite; U–Pb zircon ages; geochemistry; Sr–Nd–Hf isotopes; Gejiu; SE China
Funders: National Science Foundation of China, Special Research Funding for the Public Benefits, Research Program of Yunan Tin Group, Research Funds for the Central Universities
Projects and Grants: National Science Foundation of China 40930419, Special Research Funding for the Public Benefits 200911007-12, Research Program of Yunan Tin Group 2010-04A, Research Funds for the Central Universities 2-9-2010-21
Date Deposited: 07 Nov 2013 02:23
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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