Mineralogical Characteristics And The Mineralization Process From The Nannihu Mo-W Polymetallic Deposit In Luanchuan, Henan

Henan Nannihu Mo-W deposit is the representative porphyry-skarn deposit inChina. It is located at the southern tip of the North China Craton and the middle ofEast Qinling Mountains. To carry out detailed ore petrology, mineralogy, andgeological characteristics of the deposit study has the great significance for not only fthe Nannihu deposit, but also the similar deposits. Based on the detailed geology fieldobservation, indoor hand specimen, indoor optical microscope, electron probeanalysis, we have study geological characteristics of the deposit, wall rock alterationof the deposit, the mineralization process, and the characteristics of minerals.The result of the investigation shows that the deposit evolution process is dividedinto four stages:(1) the first stage is thermal conact metamorphic stage, surroundingrock occur metamorphism-formatting hornfels by intrusive rocks. The main lithologycontained: biotite felsic hornfels and diopside and plagioclase hornfels.(2)Contactmetasomatism metamorphic stage, with no ore silicic fluid contact metasomatic on thesurrounding rock, partial residual marble and hornfels through the late hydrothermalmetasomatism, forming veined skarn. The main lithology is calcareous skran,magnesian skarn, and diopside plagiochase hornfels.(3) the quartz-sulfide stage:Quartz-sulfide stage is the main metallogenic stage of the molybdenite, the emergenceof a large number of quartz molybdenite vein and quartz pyrite veins. Local thermalfluid and wall rock reaction is consumed to generate diopside, tremolite, actinolite andso on, molybdenite and scheelite originating in newborn skarn veins;(4) Retrogradealteration stage: mainly generating a large number of hydrated silicate minerals, suchas, actinolite, iron actinolite, epidote, phlogopite, chlorite, carbonate and fluorite.Skarn minerals are generated in the processes of mineralization. Garnet isandradite-grossular serie. Pyroxene is mainly diopside. Amphiboles can be dividedinto tremolite actinolite and iron actinolite. The formation of mica mineral isphlogopites. Epidote group minerals is epidote-zoisite series. Chlorite is brunsvigite.The skarn type is a complex skarn. Magnesium skarn minerals and calcium skarnminerals have be largely developed. Crystallization of skarn mineral assemblages and mineral formation characteristics indicate that, from early to late, the mineralizationenvironment have changed from oxidation to reduction, acidic to alkaline, the hightemperature to low temperature. The ratio of Mn/Fe and Mg/Fe in diopside indicatethat, the deposite has polymetallic mineralization is possible.