Geological Characteristics And Ore-Bearing Evaluation Of (Super) Mafic Rock Mass In The West Of Shalong,East Tianshan

Cu-Ni sulfide deposits related to Permian magmatic activities are widely developed in the eastern Tianshan area of Xinjiang,which has become an important Cu Ni metal production area in China.The total proved Ni reserves are more than 1 million tons,accounting for 12%of the national total.Under the influence of tectonic movement,regional deep and large faults and ductile shear zones are formed.The tectonic direction is northeast,mainly from south to north,there are XINGXINGXIA fault,azikekuduk SHAQUANZI fault,KANGGUL Huangshan fault(East extension section is called Dacaotan)and secondary small faults derived from its shear.There are copper and nickel deposits of turaergen,Huangshan,Xiangshan,baixintan and Lubei related to(ultramafic)rocks,and no mineralized and ore-free rocks of turaergen 3,Dacaotan and tuwudong.A large number of scholars have made a detailed study on the origin and genesis of these Cu Ni bearing rocks and reached a consensus:the eastern Tianshan(super)mafic rocks formed in the Late Carboniferous Early Permian,and the eastern Tianshan(super)mafic rocks entered the post collisional tectonic evolution stage in the early Permian,and the(super)mafic rocks intruded along the deep fault zone in the region,forming a Cu Ni deposit.However,the rock bodies produced in the same structural zone are quite different in terms of ore bearing property.The form of ore bearing rock bodies,ore bearing lithofacies and mineralization type,the proportion of ultramafic rocks,lithofacies differentiation and other factors lack systematic comparative study on whether the rock bodies form copper nickel ore.In this paper,the baixintan,Lubei,turaergen,Huangshan,Xiangshan copper nickel deposits and Dacaotan,tuwudong,turaergen No.3(super)mafic rocks are selected to the west of kumtagshalong in the East Tianshan Mountains,and the differences in ore-bearing properties of the rocks such as geological characteristics,mineralogy and petrochemistry are summarized.In this paper,the geological and geochemical characteristics of the(super)mafic rocks such as baixintan,Lubei and Dacaotan are analyzed in detail.At the same time,the East(super)mafic rocks of Tuwu are selected for testing,analysis and research,and the ore-bearing characteristics of the rocks are extracted.The main achievements are as follows:1.The ore bearing rock bodies are mainly distributed in(ultramafic)mafic lithofacies,and the typical altered minerals are orthopyroxene,hornblende and mica,with strong alteration.The rock mass is characterized by high Mg,low alkali,low silicon and low titanium,with high Mg~#and M/F values ranging from 2 to 6.5.Olivine fo values are mostly concentrated in 80-85,and the values of fo and Mg are closer,which is conducive to mineralization.The magmas of the(ultramafic)mafic ore-bearing bodies are mainly calc alkaline basalts,and tend to transit from tholeiites to calc alkaline basalts.Amphibole and mica water bearing minerals indicate that mantle derived magma metasomatism occurred in the early stage of oceanic crust subduction.SR Nd isotopes show that the source region of the studied area is dominated by depleted mantle,which experienced metasomatism and assimilation in the process of emplacement.2.The East Tuwu rock body is dominated by gabbro facies,lacking(super)mafic facies and poor magmatic differentiation.The primary magma of Cu Ni(super)mafic body in the study area is high Mg tholeiitic magma,and the diagenetic age of olivine gabbro is 289.7±1.4ma.The source area of the rock mass is dominated by depleted mantle,which may have suffered from the addition of enriched lithospheric mantle components or the contamination of crustal materials by a small amount of subduction fluid transformation.The value of olivine fo is lower than the average value of ore body fo in the area,and the ratio of Cu/Zr is less than 1.The olivine has experienced partial sulfide melting in the deep part.The tuwudong rock body does not have the metallogenic potential of Cu Ni deposit.