The Fissure-vien Systerm Of Pulang Copper Deposit

Pulang copper deposit is the biggest porphyry deposit in Sanjiang area，and alsothe typical representative of Porphyry copper deposit in Indosinian. This paperthrough data analysis, field investigation, indoor appraisal, geostatistical andgeochemical testing methods to dicuss relationship between fissure-vein andmineralization in Pulang copper deposit, then, analysed structure-fluid couplingprocess and metallogenic mechanism under the background of late Triassicsubduction, understanding and progress achieved as followed:1. Affected by subduction towards west of Ganzi-Litang and Jinshajiang oceancrust in late Triassic, this area is in the nearly EW to oblique subduction-sheardynamics mode;2. Divided fissure-vein into three metallogenic stages: early stage, main stageand late stage. Early stage vein include biotite veins, quartz veins, K-feldspar-quartzveins, and fissure fillings of quartz, biotite, nearly upright occurrence. Main stageinclude quartz-sulfide veins, typical group is quartz-pyrrhotite-chalcopyrite veins,fissures fillings of chalcopyrite, pyrite, quartz, etc., echelon-like, feather crackdistribution. Late stage veins mainly include quartz-calcite veins, calcite-quartz-pyriteveins, fissures fillings of chlorite, epidote, calcite, distribute around the ore body.Main stage fissure-vein is mainly distribute in quartz monzonite porphyry, extremecenter exist at Horizontal plane and vertical plane. In the southern orebody, the leftand right sides have different distribution, may be associated with post-granodioriteporphyry intrusion;3. On the basis of summarizing the fissure-vein spatial structure, the paperanalyze relationship between fissure-vein and mineralization, which tensionalfissure-vein is most important to mineralization, and mineralization from south of theore body is better than the north, the deep is better than in the shallow;4. Discussed the evolution of mineralization process in fissure-vein: during themigration process, the fluid change from early stage of high-temperature, high-salinitymagmatic hydrothermal to late stage of medium-low temperature, medium-lowsalinity magmatic hydrothermal, ore-forming fluid have large amount of reducingcompositions, such as CO2, CO and CH4,The copper solubility in reduced fluid islower than that in the oxidized fluid, but the gold solubility is not affected, that makesCu grade low but with massive Au ineralization;5. Through the stuy of fissure-vein system, summarizes the Pulang copperdeposit of regional tectonics and fluid coupling mechanism in shear mode. Pulangcopper deposit formed in island arc environments under subduction orogenicbackground, fissures-veins provides space and migration path for forming of ore body.Pulang copper deposit is controlled together by regional shearing and magmaticoverhand stoping, The coupling between NNW-shearing and reducing of magmatichydrothermal controlled the formation and distribution of ore bodies.