Metallogenic Model Of The Xishan Tungsten-tin Deposit In Yangchun Basin, Guangdong Province

Located in the western Guangdong Province,Yangchun Basin is one of the important polymetallic mineralized concentration area in Guangdong Province and one of the five state-level exploration areas in Guangdong Province.More than 20large and middle ore deposits have been found in the basin,such as copper,iron,lead-zinc,and tungsten-tin,and there are large number of ore spots and mineralized anomaly spots,indicating that Yangchun Basin still has good ore-finding prospecting.This article relies on the geological research project of the China Geological Survey Bureau,“Research on ore-finding prospecting on the special mapping and technological application demonstration of copper polymetallic ore exploration areas in Yangchun,Guangdong province.”(No.12120114015801).Taking the Xishan W-Sn deposit as a typical deposit,use the theory of"Trinity"metallogenic model as a guide,through systematic geological reconnaissance in the field and structural alteration mapping,and systematic sample collection and analysis.The metallogenic geological bodies features,the metallogenic structure,the characteristics of the metallogenic structural surface,the mineralization characteristics and signs of the deposit are systematically studied,and the following main results and understandings have been obtained:(1)Metallogenic geological bodies:The rock mass related to the Xishan tungsten-tin deposit is a granite and granite porphyry rock series of high K Calc alkaline series-shoshonite series.The Si O₂content of the rock mass is 69.35%?79.5%.The content of(Na₂O+K₂O)is6.53%?11.69%.In all the three types of lithology,there are a significant or obvious enrichment of B and Mo and a significant enrichment of the ore-forming element W,which is 5?7 times of the average value of the Vickers granite,and The?REE content of the rock mass is quite different,and the fractionation of light and heavy rare earth elements is not obvious.There is a significant negative Eu anomaly and it shows the characteristics of S-type(A-type)granites with diagenetic ages of about 103 Ma and80 Ma,respectively.(2)Metallogenic structure and metallogenic structural surfaceThe metallogenic structure and metallogenic structural surface of Xishan deposit mainly consist of fault structure,two stages intrusive rock mass interface,structural fracture zone,joint and fissure in the rock mass.The near SN fault zone at the top of Xishan Mountain is the main rock controlling fault and ore-controlling fault structure in this area.Various kinds of rock compressional lens bodies are developed in this structural belt,and the quartz vein is developed in the same direction as the tectonic belt.The contact zone of the two-stage intrusive rock mass is the main ore-hosting structure of the contact zone orebody.The joints in the rock mass and the fissure zone are the ore-controlling structures of the vein-like and net-vein orebodies.(3)Metallogenic characteristics:1)According to the mineralization style and metallogenic element combination,the deposit has internal and external binary structure.A vein W-Sn orebody is produced near the interface between the early and late rock masses in the rock body,and lenticular,near bedded shapes skarn type Cu-Pb-Zn-Sn ore body is produced at the contact between the rock mass and the carboniferous carbonate formation.2)The ore textures mainly include idiomorphic or hypidiomorphic granular texture,columnar texture,metasomatic and metasomatic dissolution texture and filling texture.The ore structures mainly consist of comb,massive and disseminated structures.The main metallic minerals in the deposit are cassiterite,wolframite,sphalerite,pyrrhotite,pyrite,chalcopyrite,bismuth,molybdenum,etc.The gangue and non-metallic minerals are quartz,topaz,fluorite,Muscovite,feldspar,ferromanganese,etc.Kaolin,etc.3)The alteration of the surrounding rock in the deposit is developed,and the common ones are quartz,silicification,albite,fluorinization,skarnization,hornstone,marble and so on.Among them,the most closely related to mineralization are mainly quartzite,skarnization and hornstone alteration.4)The metallogenic process can be divided into three important stages:Metallogenic early stage:this stage belongs to the local metallogenic stage of contact between rock body and carbonate rock,mainly forming skarn combination and a small amount of magnetite.The metallogenic stage consists of high temperature hydrothermal metallogenic stage and medium temperature hydrothermal mineralization stage.The high temperature metallogenic stage is the formation stage of quartz-oxide,which forms the quartz-cassiterite-tungsten mineral assemblage.The mesothermal metallogenic stage is the formation stage of quartz-sulfide,forming a metal mineral mainly composed of cassiterite,pyrite,chalcopyrite,sphalerite,galena and molybdenum.The late stage of metallogenic stage:in the middle and low temperature hydrothermal stage,the main form of quartz-carbonate is formed,which consists of the metal minerals,which are mainly chalcite,sphalerite,galena,and iron diamond.5)the metallogenic process of the deposit is continuous and lasts for a long time.The range of temperature and salinity is roughly between 158?and 446?and between2.2 wt%Na Cl?49.68 wt%Na Cl;6)The hydrogen and oxygen isotopic compositions of quartz inclusions in the deposit are as follows:?D_V-SMOWis between-53.2‰and-98.1‰,the average is-68.4‰,?¹⁸Owater is 4.66‰(7.74‰),and the average is 5.64‰.Indicating that the ore-forming fluid is mainly supplied by magmatism,but also have mixed products of magmatic differentiated water and formation water of surrounding rock.7)The metallogenic age of the deposit is 80Ma±,which is almost the same as the Yingwu-ling deposit.Tungsten tin deposit in Xishan is composed of the geological body,metallogenic tectonic and metallogenic structure,mineralization features mark coupling results from the characteristics of construction of the Xishan deposit"three-in-one"metallogenic model,the above understanding has a great guiding significance to Yangchun basin for W-Sn mineral prospecting.