Study On Genesis And Ore Control Of Dewu Copper Deposit In Hezuo City,Gansu Province

The West Qinling is located in Qinqikun metallogenic domain,Xiahe-Yawan Indosinian-Yanshanian gold-mercury-antimony metallogenic belt in the southwest,and Yanshanian copper-gold-lead-arsenic-tungsten-zinc-iron metallogenic belt in Ganjia-Zhangxian in the northeast.The overall distribution direction of the regional strata is northwest,which is consistent with the regional tectonic line.From north to south,they are Carboniferous,Permian,Triassic,Paleogene and Quaternary.Magmatic activity is mainly of intermediate-acid intrusion,NW-trending,narrow in the West and wide in the east,distributed in the Lower Kaga-Meiwu,Dewulu-Auntie Mountains.Obviously controlled by regional tectonics.The lithology is mainly composed of quartz diorite and quartz two long diorite,and a small amount is granodiorite.The U-Pb isotopic age of the de URU rock mass is 239.2 + 3.2Ma,belonging to Indosinian epoch.The ore deposit is controlled by surface exposure and drilling.The surface copper-bearing skarn belt is only a small amount of exposed in the middle of the belt.The ore types are mainly fissure-filled vein-like ore and SKARN-TYPE ore.The wall rocks are affected by contact metamorphism,but the degree is different.At the same time,there is hydrothermal alteration.The geological characteristics,mineral paragenesis,mineral structure characteristics,occurrence state and metasomatism of the deposit are comprehensively discussed.After a comprehensive study of metallogenic geological processes(geotectonic location,strata,intrusive rocks,host country rocks,host structures,genesis of deposits,metallogenic epochs,etc.)and mineralization characteristics,the main metallogenic elements are summarized.The metallogenic elements can be divided into three categories: necessary,important and secondary.By summarizing the main metallogenic elements,the comprehensive prospecting model of Dewulu copper deposit is preliminarily established as follows: carbonate formation + NW and NE trending faults + intermediate-acid intrusive rock + skarnization,hornblending,marbling,epidoterization,etc.+ Cu,Pb,Ag,Zn element anomalous assemblages.Dewulu granodiorite is rich in Cu,Au,Ag,Pb,Zn and other metallogenic elements,which provides the primary source conditions for the formation of Dewulu copper deposit.After the magma rich in ore-hydrothermal fluid intruded into the Permian sandstone and slate intercalated carbonate sedimentary strata along the fault zone,the elements of the rocks first crystallized to form the "Dewulu granodiorite main body" and contacted with the surrounding rocks(slate,sandstone,limestone,etc.),resulting in bimetasomatism.Skarn,skarn and other rocks.In the process of rock condensation and diagenesis,the Cu-bearing hydrothermal metasomatism wall rocks formed SKARN-TYPE copper mineralization(Liu Shengyou,2015).Some hydrothermal fluids are enriched and precipitated,forming a "hydrothermal" copper vein.Oxidized minerals,such as malachite,blue copper and limonite,occur in the contact between intermediate-acid intrusive rocks and Permian marine clastic rocks or endogenic rocks,which are direct prospecting indicators.The NWW and NE trending regional faults open up magmatic upwelling channels and emplacement spaces of intrusive rocks,and the Indosinian intermediate-acid magma intrudes into metasomatic wall rocks.Ore bodies occur mainly in the intrusive rocks' internal and external contact zones and secondary fault tectonic zones.Further,due to the emplacement of intermediate acid magma,the skarn type copper deposit is formed.