Geological Characteristics And Metallogenic Mechanisms Of Xingyuanchong Copper Deposit At Wanzai County, Jiangxi

Xingyuanchong copper deposit at Wanzai is located in the west segment of NEEYifeng-Jingdezhen deep fault in the northeast of Qinhang metallogenic belt, and the westsection of South Jiuling large copper polymetallic ore-concentrated area-Huangmao. It isa potential deposit found recently, and according to the analyses of metallogenicgeological features and geophysical and geochemical anomalies, it is expected to bemedium sized ore deposit through further exploration. While due to the low researchefforts, it is not sufficient to accurately grasp the metallogenic features and summarizethe metallogenic regularity in the region, so further research work is badly needed to becarried out. On the basis of former researches, by studying the regional geologicalbackground, geological features of the deposit and the orebody, fluid geochemicalcharacteristics, and carbon, oxygen and sulfide isotopic geochemical features of the oredeposit, genesis and metallogenic mechanisms of the ore deposit are analyzed, andmetallogenic model of the deposit is preliminarily established. Six major understandingsare as follows:(1) By the analysis of geological features and the geological and geochemical studyof the ore deposit, Xingyuanchong copper deposit is considered to be amagmametamorphic epithermal-mesothermal copper deposit, controlled by the NEElarge nappe(slip) structures, and closely relates with Yifengyan Formation in Jixianian.(2) According to the typical ore fabric features and mineral assemblage, metallogenyof the deposit can be divided into three ore-forming periods: submarine extrusivedeposition, hydrothermal process and supergenetic period. And the hydrothermal periodcan be furthering divided into quartz-pyrite stage, chalcopyrite-bornite stage andgalena-sphalerite stage. Finally, the mineral genetic sequence of the deposit is generallydefined.(3) Homogenization temperatures of fluid inclusions vary in the range of75~440℃, mainly in two sections:110~190℃and210~290℃, showing the feature of lowmedium temperatures; salinity values range from1.74wt%～22.58wt%, suggestingmedium high salinity. The homogenization temperature-salinity figure indicates themetallogeinic fluids are mainly submarine extrusive hydrothermal fluids and fluidsrelated with diagenesis, and a small part of magmatic fluids.(4) δ13CVPDBvalues of carbonates in this area is in the range of-5.4‰～1.9‰,0.6‰on average, whereas δ18OSMOWvalues range from9.0‰～13.8‰,10.9‰on average,indicating that carbonates in this copper deposit are mainly marine carbonates; carbonand oxygen isotopic diagram shows carbon is mainly from the deep earth, beingmetamorphosed in high temperatures and altered in low temperatures. The abovediscussion indicates the metallogenic fluids of the deposit might be the mixture ofsubmarine extrusive hydrothermal fluids, magmatic fluids and later metamorphosedfluids. except two higher values of δ34S, most sulfur isotopic values vary in the range of1.0‰～6.2‰, and in comparison with other similar deposits, sulfur in this deposit ischaracterized by submarine exhalation sedimentation and later magmatichydrothermalsuperposition.(5) By combining the above discussion, we can conclude that Xingyuanchongcopper deposit is the result of multi-periods, multi-stages, and multi-ore formingactivities. And the metallogenic process mainly underwent submarine volcanic sedimentsor protore layer formed in Mesoproterozoic and the pre-existing protore wasdiplogeneticaly alternated by the hydrothermal fluids and metamorphism mainly derivedfrom Jinning orogenic period in Late Proterozoic.