Study On The Geological Characteristics And Genesis Of Katebasu Au-cu Deposit,in West Tianshan,xinjiang

The West Tianshan Orogen in Xinjiang is North Asia orogenic belt between Tarim Platform,Siberian Platform,the eastern European Platform and Karakum Platform,had undergone complex tectonic evolutional processes,is the convergent zone of Karakum-Tarim plate and Kazakhstan-Junggar Plate. Studies have shown that the Nalati Plate had finished the docking with Atbash-Yineiliqiete and Jieersikeyi- Cara fault. Right now,the super-large gold deposits,such as Muruntau,Daugyztau,Amantaitau,Zarmitan,Kumtor,Takdybulak Lev,Jilau,Makmal,Dal’neye,Ishtamberdy,Unkertash,have been discovered in the West Tianshan’s neighbors. The West Tianshan in our country,with the similar metallogenic environment, should have the potential to be large gold deposit.The discovery of Shawayaerdun and Kateba’asu deposits can prove this point.This paper is based on the “Integrated exploration and dynamic tracking comprehensive evaluation in northwest,number 1212011220861” and “The study of typical deposits along the copper gold deposit in Xinjiang Nalati mountain, number 12120114007401”, in the basis of previous studies using observation and comprehensive,this paper deeply studies the Kateba’asu large Au-Cu deposit. From the above research the following conclusions could be drawn:1.The Kateba’asu large Au-Cu deposit is located in the Central Asian Orogenic Belt,the north margin of Middle Tianshan.Fault developed in this region most of those are secondary fault affected by the fault zone along the northern edge of Nalati. The structural fracture zone between F5 and F6 is the main prolific zone of Kateba’asu deposit.The joint structure is divided into three stages, the second stage is mineralization, and the third stage is post-mineralization,which is fracturing ore body without mineralization.2.Monzogranite in the Kateba’asu Au-Cu deposit,which belongs to high K Calc alkaline series,shows the special feature of I-typed granite. The content of CaO,MgO,TiO2,or Al2O3 was significantly negatively related with SiO2.Rare earth elements show the characteristics of enrichment in light REE but deficit in heavy REE. The REE experienced relative intense fractionation with Eu negative abnormality,which related to separation and crystallization of plagioclase. These trace elements display the features of island-arc type granite with enrichment in LILE( as Rb,Ba) and HFSE( as La,Zr,Hf),but deficit in elements such as Nb,Ta,Ti. Then formed an island arc environment by subduction,which was the dynamics background to form monzogranite in the Kateba’asu Au-Cu deposit.3.The Kateba’asu Au-Cu deposit is rich in monzogranite,followed by plagioclase granite and diorite porphyrite. Mineralization-related alteration,such as pyritization,jarositized,chalcopyrite, malachite, K feldspathization, silication, chloritization, epidotization,sericitization and carbonation,is widely developed in the rock.Determination of Gold existed mainly in the form of native gold and electrum. Native gold are mainly hosted in pyrite,followed by chalcopyrite. Occurrence of natural gold in the ore is observed included-gold,embedded-gold and fissure-filled gold.4. The Kateba’asu Au-Cu deposit is found to be composed of gold bearing pyrite with fluid inclusions of gas-liquid two-phase and CO2-H2 O.The ore-forming fluids in ores are characteristic of medium- high heat,low-middle salinity and metamorphic fluids rich in CO2.The H and O isotope compositions of ores show similarity to magmatic water.5. The determination of the U-Pb age of rocks is 91 Ma later than mineralization age, and this is a big age differences. So the metallogenic substance should not come from monzogranite.Sulfur isotopes of pyrite is 5.8‰~11.0‰,the average is 8.7‰. The enrichment of δ34S has become a notable feature of pyrite isotopes composition. It is apparently different from mantle derived sulfur,reduced sulfursulfate sulfur and ocean water sulfur.The sulfur origin should come from acidic-magmatic hydrothermal or formation. According to the structure model oflead isotopes,the setting point falls nearby upper crust and orogenic belt evolution curve.The metallogenic substance mainly comes from two-source, which is metamorphic rocks and magmatic hydrothermal in the post-collision stage.6. The formation of gold deposits is comprehensive controlled by metamorphic rocks and magmatic hydrothermal.The regional metamorphic rocks offer most metallogenic substance for mineralization.The geological structure provide a good place for ore fluid gushing and containing ore,and the magmatic hydrothermal provide dynamic condition for mineralization as the main metallogenic material source.The genetic type belongs to constructure altered rock type deposit controlled by rocks,geological structure and magmatic hydrothermal.The geodynamic setting of the Kateba’asu Au-Cu deposit is Intracontinental extension tectonics of the Premian post-collision stage.