GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
Zircon U–Pb geochronology and geochemistry of copper-bearing monzogranite in the Rexiang hydrothermal Cu deposit in the central Yidun Island Arc, northeastern Tibet
Guangchun FeiYouguo LiJin ChenWei Luo
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2015 Volume 49 Issue 2 Pages 195-205

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Abstract

The Rexiang hydrothermal Cu deposit, a newly discovered medium-sized deposit, is located in the central Yidun Island Arc (YIA) in northeastern Tibet. Zircon LA-ICP-MS U–Pb dating for a Rexiang copper-bearing monzogranite sample gives a crystallization age of 79.3 ± 0.7 Ma (MSWD = 3.8). Geochemical data indicate that Rexiang copperbearing monzogranite has high-K calc-alkaline to shoshonitic compositions, moderate A/CNK values (lying primarily within 1.02–1.06), high differentiation index (DI = 86–94), and moderate amounts of corundum (0.34–2.19%), indicating an affinity to weakly peraluminous and highly fractionated I-type granite. REE patterns show enrichment in LREE relative to HREE. The monzogranite is characterized by moderately negative Eu anomalies (δEu = 0.22–0.77), strong enrichment in Rb, Th, U and Ta, depletion in Ba, Sr and P, and higher initial 87Sr/86Sr ratios (0.70957–0.7114). Combined with the analysis of its tectonic setting, the monzogranite is interpreted as resulting from partial melting of supracrustal rocks in the postorogenic stage after the collision orogenesis of the YIA in the Late Yanshanian. A Late Cretaceous porphyry (hydrothermal) Cu–Mo-polymetallic mineralization event not only exists in the southern segment of the YIA (the Zhongdian arc) but also in the central segment of the YIA.

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© 2015 by The Geochemical Society of Japan
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