| Yangchun basin,located in the western part of guangdong province,is one of the important polymetallic mineralization concentration areas in guangdong province.It is also one of the five national exploration areas in guangdong province.The Qiguling area is a skarn-type copper-molybdenum-tungsten polymetallic mineralization area that has been discovered in the basin in recent years.The drilling have revealed a total thickness of more than 120 meters of copper polymetallic mineralization.This paper relies on the geological research project of the China Geological Survey Bureau“Special Mapping and Technology Application Demonstration Prospecting Research in Guangdong Yangchun Copper Polymetallic Mining Exploration Area”(No.12120114015801)with the support of scientific research projects.A systematic study of metallogenic geological characteristics,geochemical characteristics,metallogenic physicochemical conditions,diagenesis and metallogenic epochs of the Qiguling skarn-type copper polymetallic mineralization was conducted through the geological route observation of field,drilling records,structural alteration maps,systematic sample collection and analysis.The cause of the deposit was discussed.And the following major achievements and understandings have been obtained:1.The Cu polymetallic mineralization in Qiguling mainly occurs in skarn,skarn marble and calcareous quartz sandstone in the Tianziling group and Maozifeng group of the upper Devonian.Mineralization is closely related to the fault structure and the degree of fracture development of the rock.The surrounding rock alterations have developed,mainly including skarnized,wollastonite,silicification,chloritization,epidotization,pyritized,hornstone and calcitization.Among them,skarnized,pyritized,silicification,and epidotization are important to mineralization.2.The ore structure is mainly composed of the granular structure of the hemi shape and semi self form,the granular structure,the metasomatic silkworm structure and so on.The ore structure is dominated by massive structures,veinlet-like disseminated structures,and network-shaped structures.The main metal minerals in the ore include:chalcopyrite,pyrite,magnetite,malachite,limonite,scheelite,molybdenite,and bismuth ore.Non-metallic minerals mainly include:garnet,diopside,wollastonite,actinolite,tremolite,epidote,quartz,serpentine,calcite and so on.According to rock ore structure and alteration mineral association,the copper-polymetallic mineralization process in Qiguling can be divided into dry skarn stage,wet skarn stage,quartz-oxide stage,quartz-sulfide stage,and carbonate sulfate stage from early to late.3.The study of trace element characteristics shows that with the progress of skarnization,the types and contents of elements enriched in rocks have increased significantly.From pure marble(or limestone)to unmineralized skarn(surrounding rock)to skarn ore,Cu,Mo,W,Bi and other mineralization elements are a process of continuous enrichment.Compared with marble,the enrichment coefficients of Cu,Mo,W and Bi in the skarn ore exceed 30,reflecting that the copper polymetallic mineralization in the area is mainly caused by skarnization.The correlation study of trace elements in ore indicates that the ore-forming element Cu is significantly positively related to Mo,Cr,Zn and other elements,reflecting these elements have similar material sources and migration and precipitation processes in the mineralization process.And the poor correlation between W and Cu and Mo indicates that they may be the products of different mineralization stages.4.Studies on the characteristics of rare earth elements show that the distribution patterns of rare earth elements in surrounding rocks such as limestone,marble,skarn,skarnized marble,and quartzite in the Qiguling mineralized area are basically the same,and they are all gentle right-dip curves.The ore's rare earth distribution curve presents two distinct forms.A distribution curve is consistent with the curve of the surrounding rock,which indicates that the REE composition of the ore has certain succession to the surrounding rock.Another is a flat type,its distribution curve is different from the curve of the surrounding rock.It may reflect that it is more strongly affected by the late hydrothermal fluid transformation.5.The microscopic temperature measurement results of fluid inclusions indicate that the metallogenic temperature in the Qiguling mineralization area can be divided into three stages:the high temperature stage of 302 to 401°C,the medium to high temperature stage of 154 to 396°C,and the low temperature stage of 117 to 269°C.302?401?and 401?154?and 117?269?,the corresponding salinities were 3.87%?3.87%Na Cleqv,1.24%?7.71%Na Cleqv,and 0.88%?0.88%Na Cleqv.In the first stage,skarn mineral garnet,diopside and other high-temperature altered minerals are mainly formed,and the fluid has the characteristics of high temperature and low salinity.The second stage is the main metallogenic stage,producing a large number of metallic minerals.The mineralization of this stage is closely related to fluid mixing and boiling.In the third stage,the fluid is in a strong oxidizing environment,with the participation of atmospheric precipitation and other fluids,mainly forming carbonate minerals,and the mineralization basically ends.6.The study of stable isotopes in the mineralization area shows that the hydrogen and oxygen isotope compositions of the fluid inclusions in the mineralization area are:The average value of the?DV-SMOW is from-58.1‰to-75.2‰with an average of-64.75‰.The average value of the?18Owater is from 3.56‰to 7.63‰with an average of 5.85‰.It is indicated that the metallogenic fluid is mainly provided by the magma,there may be the addition and mixing of part of the formation water.The sulfur isotope composition of pyrite is as follows:the value of the?34S is between 1.4‰and2.5‰,which is close to the zero value.It is indicated that the metal sulfide mainly comes from the original sulfur,which has no obvious sulfur isotope fractionation.The isotopic composition of S,H and O indicates that the metallogenic fluid in the Qiguling mineralization area is mainly derived from the deep magma.7.The study of diagenesis and metallogenic epoch shows that the LA-ICP-MS zircon U-Pb age of granodiorite in the Gangmei rock body,which is adjacent to the south east side of the mining area,is 164.4±1.3 Ma,the weighted average Re-Os age of molybdenite which is in the edge of Gangmei rock is 163.1±1.4 Ma;The weighted mean Re-Os age of molybdenite in the Qiguling polymetallic mineralization zone is 164.54±0.96 Ma.Diagenetic age of Gangmei rock body,the mineralization age of copper molybdenum tungsten in the edge of Gangmei rock body and Qiguling copper polymetallic metallogenic age within the error range is consistent,reflecting the mineralization is closely related to the magmatic event of this period.Therefore,the mineralization of the mine area may be related to the magmatic events of Gangmei rock mass or directly related to Gangmei rock mass.The geological and geochemical characteristics of the skarn-type copper polymetallic ore deposit in Qiguling area indicate that the copper-polymetallic mineralization belongs to the far-source skarn-type polymetallic mineralization controlled by the structure. |
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