Study On Geological Characteristics And Prospecting Potential Of The Podong Cu-Ni Sulfide Deposit,Northeast Margin Of The Tarim Plate

Ruoqiang county has attracted attention for discoverying large number of magmatic sulfide nickel deposits.Poyi nickel deposit is an ultra-large magma sulfide deposit that has been recently discovered.The ore body hosted by peridotite consists mainly of disseminated sulfides with low Ni grade.The new ore body was discovered at the east of the Poyi deposit during recent exploration,and was named the Podong Cu-Ni sulfide deposit,which was characterized by net-textured sulfides with high Ni grade hosted by gabbro-norite,providing new clues for exploration object.The previous researches on the slope north rock mass have been extensively and deeply,but mainly focused on the study of Poyi and Poshi deposit,and the research on the slope east deposit is weak.There are still controversies on geological setting,petrogenesis and metallogenic mechanism of the Pobei complex.This paper is focus on exploration drilling samples and latest in detail the microscopic identification of Podong which from the aspects of petrography,mineralogy,geochemistry and so on.The paper focusing on systematic petrography and mineralography of the slope,mineral crystallochemistry,chronology,rock geochemistry and isotopic geochemical to discuss the scientific problems of metallogenic geological background,magmatic origin,magmatic evolution and ore-forming process which to provide a right direction of next step prospecting in Pobei area.The paper mainly made the following progress:?1?The petrographic composition of Podong deposit are Iherzolite facies,Gabbonorite facies,Gabbro facies.The main rock-forming minerals are olivine,orthopyroxene,clinopyroxene,amphibole and plagioclase.We obtain the development sequences of minerals is olivine?clinopyxene?plagioclase?orthopyroxene?amphibole??2?The results of gabbro zircon SHRIMP U-Pb age was 274.5±1.8Ma,and the same age as Poyi,which shows that temporally related to the²75 Ma Tarim Large Igneous Province,and was derived from depleted mantle source with OIB-like signature,affected by fluid metasomatism in magma source.?3?The m/f,?Nd_?t?values of whole rock and Fo values of olivine from the Podong gabbro-norite,are distinctly lower than that of the Poyi deposit,which indicate relatively high magma evolution degrees for the Podong ore-forming petrofacies,and the higher of magma evolution the more intensive of crustal contamination affect.?4?The ore body is occurrence in the gabbro facies in the Podong deposit.we think the Podong deposit is formed by sulfide segregation from basic magma,and the sulfide saturation was caused by magma crystallization and crustal contamination.However,the ore body is occurrence in the ultrabasic facies in the Poyi deposit,we think that is formed by sulfide segregation from ultrabasic magma caused by magma crystallization itself,as the sulfur solubility decreases along with the olivine and chromite crystallization.?5?Most ore-forming indicator of Podong are good,and only a few is different from typical deposits.So the next step should be carried out rock mass attention when looking for rich ore gabbronorite facies especially the lithofacies diversity in rock mass and vein rocks and marble residue area in Pobei.