Petrogenesis And Metallogenesis Of The Dalaku’an Mafic-ultramafic Intrusion In South Of Tarim Plate

Dalaku’an intrusion is located in the south Tarim massif,30km southeast of A’qiang,Qiemo, the joint of Altun Mountains and Kunlun Mountains, which is part of South Kunlunmagmatic arc. Most basic-ultrabasic rocks lies in the south Tarim massif, north of KunlunMountains had been classified as magnesia peridotite during1:250,000regional geologicalsurvey. However, Dalaku’an intrusion has abundant types of rocks, belongs to ferruginousultramafic intrusion, ore mainly occurrence in peridotite, the highest-grade of single sample ofNi and Cu are0.65%and1.4%, has a good prospecting foreground and potentiality. Based onthe situation, this thesis will take Dalaku’an as a example, discuss the character of magmasource, quality of primary magma, assimilation fractional crystallization and ore-formingpotential by doing researches on geochronology, petrography, mineragraphy, mineralogy,geochemistry and Nd-Sr-Pb-Re-Os isotopes. The achievements obtained as follows:1Magma differentiationed well, mainly comprised of lherzolite, harzburgite, wehrlite,pyroxenite, gabbro, anorthosite. The rocks are mainly composed of olivine, clinopyroxene,orthopyroxene, plagioclase. Zircons U-Pb ages from gabbro of Dalaku’an is332.9±1.2Ma,pertain to Carboniferous.2The m/f values of most ultramafic rocks range from3.20to5.14, so Dalaku’an is aferruginous ultrabasic intrusion. The concentration of r are earth elements and trace elementsranges from9.89×10-6～88.59×10-6. The (La/Yb)Nvalues of all samples range from1.32×10-6~11.40×10-6, the (La/Sm)Nvalues of all samples range from1.08×10-6~4.26×10-6,and diversified lack of Eu negative variation with LREE weak enriched,LILE abundance and HFSE depletion.3The primary magma is high MgO tholeiite basalt. εNd(t) and εSr(t) respectively are-8.72~-5.03and26~167, displayed enriched-mantle feature. Re/Os mean value of samples is12.85, γOs(t)=242.53-1181.19, proved primary magma has been strongly assimilated andcontaminated during ascend and migration.4Cu-Ni sulfide occurrence in peridotite and ore structure mainly is disseminated and spongesiderite. Olivines in all litho-facies of Dalaku’an intrusion lack of Ni, Cu/Pd of samples are 4925～11181(mean8829)，higher than Cu/Pd of primitive mantle(7690)，proved the primarymagma had sulfide liquation during early evolution.5In consideration of rock mass characteristics, structure, feature of sulfide liquation and massbalance, Dalaku’an intrusion has good mineralize conditions and ore potential in deep.