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The Features Of Magmatic Rocks In Shangwang Gold Mine,Shanxi Province And Its Implication On Gold Mineralization

Posted on:2013-02-24Degree:MasterType:Thesis
Country:ChinaCandidate:H WangFull Text:PDF
GTID:2210330371982338Subject:Mineralogy, petrology, ore deposits
Abstract/Summary:PDF Full Text Request
The Shuangwang gold deposit is an impotant large gold deposit occurs in theWest Qinling area. It is located in the South Qinling gold metallogenic belt betweenthe Shangzhou-Danfeng fault and Fengxian-Zhen'an fault.The deposit is hosted inhydrothermal cryptoexplosive breccia. Through systematic study of geologicalfeatures of deposit, mineralogy, petrology, geochemistry of magmatic rocks inShuangwang gold mine, and comparative study between deposit and magmatic rocks,we have figured out the characteristics and genesis of magmatic rocks around themine, revealing the genetic relationship between magmatic rocks and deposit. Someconclusions have been drawn as below:(1) In Shuangwang gold mine, Xiba granitiod as the most widely distributedmagmatic rocks have two periods. The first phase of the intrusions formed in218~219Ma, are typical of I-type granitic rocks and have the characteristics ofadakitic rocks. The second phase of the intrusions formed in215Ma, are transitionalbetween I-type and A-type granites. The Xiba granites have the same source rockswhich mainly consisted by Proterozoic mafic lower crust(such as Yaolinghe group)with some mafic magma derived from partial melting of mantle lithosphere.Thegranitiods were formed in the tectonic environment of transformation fromcompression to extension in the Qinling orogenic belt. The residual mineralassemblage of the first phase intrusions are consist of hornblend and garnet withoutinvolvement of significant amouts of plagioclase, which implies its source region isvery deep. The residuum of the second phase intrusions are horrnblend, plagioclase,and a small quantity of garnet, which indicate a slightly lighter source depth than thefirst.(2) Granite-porphyry formed between Late Indosinian and early Yanshanian aredifferentiation of I-type granitoid rocks. The diagenetic material are the ancient crustalbasement without mantle material. It was formed in the tectonic environment ofthinning of the crustal thickness, the source region residues are mainly plagioclase andgarnet.Lamprophyre dikes formed in the within-plate setting of Yanshanian. Thelamprophyre formed from the magma derived from partial melting of the mantle withmetasomatism of fluids in subduction zone, and with contamination of crustalmaterials in rising process of the magma.(3) Through the geochronology study of other deposits in the region of Fengtai area. We figure out Shuangwang gold deposit formed in the late Indosinian similar tothe age of Xiba granitiod, had a temporal relationships and close genetic link with themagmatism. Granite-porphyry and lamprophyre are post-ore dikes with no geneticrelationship to gold mineralization.According to study of material composition ofXiba granitiod, ore-hosted stratum, altered rocks, and ore, coupled with hydrogen,oxygen, carbon, sulfur, lead isotopic composition, it is reasonably considered thatore-forming materials were mainly derived from country rocks and underlying rocks.Xiba granitiod provided hydrothermal fluid, heat and some ore-forming materials.
Keywords/Search Tags:Shuangwang gold deposit, magmatic rocks, genesis of magmatic rock, relationships between magmatism and gold mineralization
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