Metallogenic characteristics of Shitoukengde intrusion and its implications for Ni-Co-(Cu)sulfide mineralization in East Kunlun

Xiarihamu deposit is the only super-large Ni-Co deposit found in East Kunlun orogenic belt(EKOB)until present.Shitoukengde(STKD)intrusion is considered to have the potential to become a large Ni-Co deposit in East Kunlun.In order to discuss the metallogenic potential,this study present petrographical,geochemical data,and zircon U-Pb dating for the STKD intrusion.The STKD intrusion is hosted within mafic-ultramafic rocks which contain peridotite,pyroxenite and gabbro,and mainly intruded into the marble of the Paleoproterozoic Jinshuikou Group.Harzburgite and orthopyroxenite are the main country rocks for the Cu-Ni sulfide mineralization.Combine with the positiveε_(Hf)(t)values(+1.1 to+8.6)of zircons,the enrichment of LILEs,depletion of HFSEs,and lower Ce/Pb ratios of whole rocks indicate that the parental magma was originated from the depleted asthenospheric mantle and experienced 5%–15%crustal contamination.Troctolite formed during the Early Devonian and it has weighted mean^(206)Pb/^(238)U age of 412 Ma.Regional background information has indicated that the post-collisional extension setting has already existed during the Early Devonian,leading to the formation of STKD intrusion and Cu-Ni sulfide mineralization.STKD intrusion may have the potential to be one economic Cu-Ni sulfide deposit but seems unlikely to be a super-large one.

Mafic-ultramafic magma activity and copper-nickel sulfide metallogeny during Paleozoic in the Eastern Kunlun Orogenic Belt,Qinghai Province,China

The Eastern Kunlun Orogenic Belt(EKOB)has a complex geological structure and diverse magmatic activities,which are closely related to the Qaidam Basin and the Tethys tectonic evolution.There are at least 3 stages mafic-ultramafic rocks occurred in the Early Paleozoic in EKOB.The first stage is the Later-Silurian to Early Devonian,represented by the giant Xiarihamu super large magmatic Cu-Ni deposit,containing about 1.18 million metric tons(Mt)of nickel with average grades of 0.65%Ni,and its age of ore-forming pyroxene peridotite is 411 Ma;The second stage is the Early Carboniferous,represented by the large Shitoukengde magmatic Cu-Ni sulfide deposit,and its ore-forming age of the olivine websterite is 334 Ma;The third stage of mafic-ultramafic rocks occurred mainly during the Middle-Late Triassic,represented by Xiaojianshan,Lalinggaoli,and Kaimuqi complexes,and no economical ore bodies have been found in this period.The authors summarized the difference between the ore-bearing and the nonmineralized mafic-ultramafic rocks in the EKOB.The olivine of the ore-bearing complexes contains higher MgO and SiO2 content but lower FeO and CaO contents,and the clinopyroxene of ore-bearing complexes contains lower FeO and CaO contents.Crustal sulfur contamination is key to the formation of the giant Xiarihamu Ni deposit,and crustal sulfur contamination degree of the giant magmatic Ni deposit is higher than that of large Ni deposit.The above indicators could guide the exploration and evaluation of similar deposits in the EKOB.