Contrast Study Between Xiongcun Copper-gold Deposit And The Dongga Gold Deposit, Tibet

The Xiongcun copper-gold deposit and the Dongga gold deposit are located in south of eastern Gangdisi tectonic belt.The region is experienced an evolution history including subduction orogeny of oceanic crust,collision orogeny and intra-continental orogeny since late Jurassic,every time,the tectonism produced its own tectonic-magmatic activities,and came along with mineralization.So,it will be very prospective to find more deposits in the region.This thesis takes Xiongcun copper-gold deposit and Dongga gold deposit as its research objects.Through analyzing the two deposits characteristics which include geological,orebody,geochemical and the genesis,the author carries out comparative research between two deposits.Through the contrast study of two deposits of geological characteristics,the author considers that the times and the types of volcanic (sedimentary)-magma activity in two deposits are similar;The author find mineralizational porphyry in the east of Dongga deposit.Through the comparative research of two deposits of orebody characteristics,the author considers that the Xiongcun deposit is a bed or like a bed orebody,which is controlled by stratum-lithology and porphyry,the Dongga deposit is to be composed of the veined orebody,which is controlled by the fracture-crack and stratum-lithology;the fabric and components of the ore in two deposits are same;the Xiongcun deposit has the typical porphyry deposit hydrothermal alteration and zonation,the alteration which is related to mineralization is demonstrated by biotite,K-feldspar,andalusite-secondary quartz,silicification,muscovite.The hydrothermal alteration of Dongga deposit is weaker,the alteration which is related to mineralization is demonstrated by silicification and quartz-sericite alteration around the silicification, the silicification occasionally shows as chalcedony-sulfide veins,the Dongga deposit shows the characteric of epithermal deposit.Through the comparative research of two deposits characteristics of macroelements,fluid inclusion characteristics, oxyhydrogen isotope, sulfur isotope,lead isotope,the author considers that the tuff and porphyry belongs to calc-alkalic to tholeiitic rock type;The inclusion characteristics of Dongga deposit are same as the inclusion characteristics of later period gold (silver)-Polymetallic mineraliztion of Xiongcun deposit;The oxyhydrogen isotope of the two deposits is similar,which shows the metallogenic fluid originating from atmosphere precipitation; The sulfur isotope of two deposits is similar,which reflects deep source sulfur characteristic.Through the genesis study of two deposits,the author considers that the Xiongcun deposit is a porphyry deposit, the Dongga deposit is a epithermal deposit, and the two deposits are belonged to porphyry-epithermal metallogenic system.