Geochemical Characteristics And Ore-forming Potential Of The Turkubantao Mafic-Ultramafic Complex, Xinjiang

Kekesentao-Qiaoxiahaka metallogenic Belt located in the Altay region of northwesternXinjiang, main mineral are porphyry copper deposit, Cu-Ni sulfide deposit of magmaticsegregation and alteration-type gold deposit of structure-controlled. Tuerkubantaomafic-ultramafic complex is located in the northwestern margin of this metallogenic Belt,along with the Ertixi fault, and tectonic position belongs to the northwest margin of Junggarplate. This paper study systematically Tuerkubantao complex through research on thepetrology, mineralogy, geochemical and isotope chronology etc, expounds the geologicalcharacteristics and the properties of magma source with original magma, and discussesmagmatic evolution process and assimilation-hybridization. And comparing withmetallogenetic rock between mafic-ultramafic Intrusions of Kalatongke and HuangshanRegion, we have evaluated the potential of Cu-Ni sulfide deposit mineralization. Based onthese researches, we get some understanding as follows:1.Tuerkubantao complex consists of diorite, gabbro, olivine gabbro, peridotite pyroxeniteand a few peridotite. The main rock-forming minerals are olivine, clinopyroxene,orthopyroxene, hornblende and plagioclase, the accessory minerals are magnetite, ilmeniteand titanite. The olivine is chrysolite, Fo value is84.10~85.33; The species of clinopyroxeneand orthopyroxene are bronzite and diopside respectively; The plagioclase mainly arelabradorite, bytownite and a few andesine.2.The rock chemical compositions consists of iron mafic-ultramafic rocks andmagnesium ultramafic, m/f is0.51~7.68；The REE total content reduces with the increasing ofbasic degree， the degree of fractionation between the LREE and HREE elements is weak,LREE is right type of slightly enriched; Samples enrich LILE, with deficit of Nb,Ta.The rockgeochemistry characteristic indicated that in the magmatic evolution process has the weakassimilation hybridism.3.The results of La-ICP-MS zircon U-Pb date shows that the age of biotite Granites is370.5±1.4Ma, diorite and gabbro are380.0±2.2Ma and382.7±1.6Ma respectively, these areall formed in the Paleo-Asian Ocean to subduction of Siberia under the background of themiddle-late Devonian period.4.Cu-Ni mineralizes of The surface of Tuerkubantao complex is not obvious, and themineralization phenomenon mainly are found in the gabbro face, next is the peridotite face,and displays the broken rock, alters intensely and so on. Metal minerals include ilmenite,chalcopyrite, pyrite, magnetite and violarite, etc. which contents are all low,especially violarite. 5.The MgO lower limiting value of the primary magma is7.77%, which belongs to highmagnesium tholeiitic magma. Geochemical characteristics show that the magma has weakupper crust assimilation hybridism. In magmatic evolution process, olivine and orthopyroxeneare mainly fractional crystallization, and is accompanied by the few clinopyroxene and theplagioclase.6.Comparing with the known Cu-Ni sulfide deposits, especially with Kalatongke depositcomparative study: Tuerkubantao complex in the geochemistry characteristic of majorelements, the mineralization characteristic, REE and the geochemistry characteristic of traceelement, the rock formation age and so on, have shown difference with known copper-nickelsulfide deposits in north of Xinjiang. Its copper nickel sulfide ore deposit mineralizationcondition is not superior, considering to search the potential of such deposits.