Rare Earth Element and Trace Element Geochemistry of Shalagang Antimony Deposit in the Southern Tibet and Its Tracing Significance 
for the Origin of Metallogenic Elements

Abstract

Abstract:

Shalagang antimony deposit of the southern Tibet occurs in carbonaceous slate, pelitic siltstone and silicalite in the Jiabula Formation of the Lower Cretaceous, and diabase in Yanshanian and gabbro in Himalayanian. The ore bodies are controlled by E-W striking interlayer faults and S-N striking faults. The weakly country rock alteration distributed along the ore bodies with symmetrical plane and zone. Analytic results show the REE patterns of the carbonaceous slate and silicalite are similar to that of the upper crust and shale in Paleozoic and Mesozoic. The REE patterns of the gabbro with LREE depleted, HREE enriched and slightly Eu depleted flat curves are different from that of Yanshanian diabase in the southern Tibet with LREE enriched and without Eu abnormal curves. The strong enrichment and high fractionation of LREE, moderate depletion of Eu and strong depletion of Ce in the Chondritenormalized REE patterns of the antimony ores are different from those of hydrothermal fluid and exhalite from the black- and white- smoker chimney within Mid-Atlantic Ridge, North Atlantic seawater and Woxi Sedex type W-Sb-Au deposit, but the Chondrite-normalized REE patterns of the antimony ores have the strong reversed change with that of Himalayanian gabbro. Furthermore, the characteristics of strongly negative anomaly of Nb and positive anomaly of Ce and Ba in the trace element MORB-normalized spider diagram for antimony ores show the similar to and different from those for Himalayanian gabbro, carbonaceous and silicalite. The sulfur isotopic compositions of sulfides from Shalagang antimony deposit （δ³⁴S）range from-2.6‰ to-4.1‰ besides 10.3‰ and-41.6‰. All above show the metallogenic elements were mostly derived from the Himalayanian magma and less from adjacent rocks. The δD and δ¹⁸O_H2O are-151‰ to-166‰ and 9.4‰ to 12.3‰，respectively, which show the ore-forming fluid was the mixed solution of postmagmatic hydrothermal and underground water.To sum up, Shalagang antimony deposit, which is an epithermal type,formed in Miocene and was related to the formation of the southern Tibet detachment system. The metallogenic elements are mostly derived from Himalayanian gabbroic magma, and less from the adjacent rocks. The water in the metallogenic fluid is derived from Himalayanian postmagmatic solution and underground water.

Key words: southern Tibet, Shalagang antimony deposit, REE and trace element geochemistry, metallogenic element

CLC Number:

P618.66

QI Xue-xiang ，LI Tian-fu，YU Chun-lin. Rare Earth Element and Trace Element Geochemistry of Shalagang Antimony Deposit in the Southern Tibet and Its Tracing Significance
for the Origin of Metallogenic Elements [J]. Geoscience, 2008, 22(2): 162-172.

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