Evolution Of Regional Tectonic And Metallogenic Regularity Of Cu-Au Ore Deposits In East Junggar, Xinjiang

Locating in the north—eastern region of Xinjiang, East Junggar, geotectoni-cally, sits in the southern of Altay massif of the Siberian Plate. As a transition areabetween the Siberian Plate and the Kazakhstanian Plate, it is bounded by Karameili—suture in the south in conjunction with the Kazakhstanian Plate.Upper Paleozoic Erathem developed perfectly in East Junggar. Intruding inmiddle—late Variscan period, the granitoids are mainly orogenic granite series.The evolution of regional tectonic can be divided into 4 stages:â‘ Presinianperiod—ancient craton stage;â‘¡Sinian～Cambrian Period—stable cover stage;â‘¢Lower Paleozoic Era—ancient craton breakup stage;â‘£Upper Paleozoic Era—ex-pansion and compression in ture stage, including;â… ) D～C₁¹, expansive oceanbasin to compressive ocean basin;â…¡) C₁², ocean basin closure and rifting trenchexpansion;â…¢)C₁³, collision and orogeny;â…£) C_2-3, partial expansion after up-heaval;â…¤) P, intraplate evolution.According to the metallogenic environments and the characteristics of the wall—rocks, regional Cu—Au multimetal ore deposits can be divided into 6 types:â‘ Cu—Ni sulfide deposits related—to basic complex;â‘¡skarn—type and porphyry—type deposits related—to medium—acid intrusion;â‘¢hydrothermal deposits related —to metamorphic rocks, which include turbidite—type, basic—ultrabasic forma-tion type, and volcaniclastic—sedimentary formation type;â‘£magma hydrother-mal Au deposits related—to diroritoids;⑤epithermal ore deposits in land—faciesvolcanics;â‘¥hydrothermal vein deposits concerning volcanic—sedimentary.Systematic studies of geological—geochemical characteristics and mechanism inSorkuduk Cu deposit are made. The wall—rocks are mainly tuffaceous sand rocksand andesites, in stead of carbonate rocks. The ore—forming fluids mainly comefrom magma water, and the mineralized material is from deep—source. The min-eralized temperature is from 560℃to 140℃. The salinity changes in two ranges(4～14 wtï¼…Nacl and 30～34 wtï¼…NaCl), and the pressure is about 35～70MPa. The hydrothermal solution belongs to KCl—NaCl—H₂O system. All thesechuracteristics show that Sorkuduk Cu deposit belongs to skarnoid type, being dis-tinct from contact metasomatic skarn deposits.The study of the deposits related—to the metamorphic rocks, shows that themineralization includes 4 stages;â‘ source bed forming;â‘¡regional metamor-phism, making Au enrichment;â‘¢dynamometamorphism (ductile shear zone,fracture zone etc. ), resulting in Au remobilization, enrichment, and mineraliza-tion;â‘£secondary enrichment.Regional metallogenic epoches are in middle—late Variscan period (325Ma±to 255Ma±). and the main metallogenic environments are the rifting trench, sub-duction orogenic zone, and suture. The matallogenic zone can be divided into 3zones, and 7 subzones, including 5 prospective areas.In addition, the study of the Nanmingshui group to which major Au depositsrelated, shows that the Au content is not very high. As a source bed, the stratamust be rich in the organic anthrinoid, or the mafic—ultramafic rock mass, ormedium—acid intrusion providing Au—origin. The necessary prerequisites give theclues of prospection and prediction of Au deposits concerning metamorphic rocks.