Mineral Deposits And Mineralization Backgrounds Of Katbasu Au-Cu Deposit

Katbasu Au-Cu deposit, this thesis discussed, is located in Western Tianshan Mountains in Xinjiang region, East part of "Asian Gold Belt",which is a world-class metallogenic belt in Central Asia. Due to the deposit is in the detailed exploration stage, deposit research work is still at an early stage, no one has studied the geological features of this deposit systematically, and the genetic type has not been determined. In this thesis, which is intended to solve those problems and provide a theory for surrounding prospecting work of Katbasu deposit in the further stage, Mineral deposits and mineralization backgrounds of Katbasu gold-copper deposit are detailedly discussed. In this thesis, basing on "Trinity"(i.e., mineralization geological body, metallogenic structural andstructural surface, mineralizational characteristic symbol) prospecting model as theoretical guidance, by collecting geological reports and papers, deposit field geological survey, identified monzonitic granite and diorite as ore-bearing rock body; by analyzing the relationship between altered mineral and ore minerals, relationship between the Zonal features of mineralization and alteration in space, relationship between magmatism and alteration, alteration type of wall rock is determined, and identified that this deposit has two phases of hydrothermal alteration and mineralization, mineralization is divided into three stages; by analyzing rock geochemical data the structure of the diagenesis and mineralization background deposits is determined.The main results achieved are as follows:1. Mineralization phases of Katbasu Au-Cu deposit can be divided into three stages: the first stage is mainly gold mineralization, which is related to hydrothermal mineralization after monzonitic granite magmatism, geological ore-bearing body is monzonitic granite; the second stage is related to Au-Cu hydrothermal mineralization after the dioritic magmatism, geological ore-bearing body is diorite; the third stage is supergene mineralization.2. The structure, represented by fault fracture zone and joint construction, is extremely developed in the deposit area. Secondary tectonic fracture zones of Nalati north rim fracture structure controls the distribution of the deposit belt, ore mineralization is distributed between fault F5 and F6, joints systems of this area is divided into two systems: Joint structure system during mineralization, the space between breccias in the fracture zone and conjugate shear joints developed beside the fracture zone provide ore-bearing space for the early mineralization; structure after mineralization, mineralization can’t be seen in this set of fracture system, which only destroyed ore-formation formed earlier.3. Ore texture includes: idiomorphic-hypidiomorphic granular texture, allotriomorphic granular texture, metasomatic texture, metasomatic relict texture, poikilitic texture, cataclastic texture, etc. ore structure includes: Fine vein structure, veinlet-disseminated structure, Massive porphyritic structure, dense massive structure, brecciated structure, loose powdered structure and miarolitic structure, etc.4. Alteration is intensive distributed in the wall rocks. alteration types from the center to the rim of the western and eastern part of the deposit change sequentially in the order : potassic alteration, silicification- sericitization, chloritization, carbonatization, kaolinitization,etc; skarn alteration is distributed in the internal or external contact zone of marble and western part of the deep rock body, the zonation of alteration from the center to the rim in the external contact zone can be seen in the order: garnet zone, diopside zone, Tremolite – actinolite zone, epidotization zone, marble zone.5. Major elements data indicates Katbasu metallogenic granite rock body belongs to mid-high potassium and calc-alkaline granitic series formed in an island-arc environment; REE characteristics shows Ce weak negative abnormality and Eu negative abnormality. Enrichment of LILE and depletion of HFSE reflects the volcanic arc granite element characteristics. Graphics of Rb-Yb + Nb and Rb-Yb + Ta show that the granite of this region mainly formed in an island arc environment.6. Deposit type of Katbasu Au-Cu deposit can be classified as superposed mineralizational deposit, according to the relationship between mineralization and skarn; be classified as calcium skarn deposit type by the composition of original rock,which formed skarn; be classified as altered rock type of fractured zone – skarn superimposed deposit; according to superposed mineralization types and genesis of deposits; skarn Au-Cu deposit is mainly distributed in the contacting skarn zone of intrusion rock and marble formations; altered rock type of fractured zone Au-Cu deposit are mainly distributed in fractured zone in monzogranite rock.