Study On Granite And Skarn In Tungsten Polymetallic Mining Area Of ​​Xiaoshan Dam, Wenshan, Yunnan Province

A discuss on the intrusion, skarn and geology of Xiaopingba deposit has been carried out based on the application of modern mineral deposit geology, petrology and geochemistry and geological investigation, sample analysis. The following are main result:Metallogenic geological conditions:The initial enrichment of ore-forming elements in shallow marine shelf facies-clastic rock of littoral facies carbonate formations of the Late Paleozoic renders few material; Carbonate rocks laid a advantage surrounding rock conditions for the formation of skarn deposits. In terms of construction:the NE, NW faults, contact zone are advantageous space for the ore fluid migration, accumulation and mineral precipitation. At the magmatic type, Xiaopingba deposit is located in the eastern edge of Bozhushan acidic rock.The ore-forming rock is the medium grained biotites monzogranite of the first intrusion of Bozhushan. It’s enriched in SiO2, Al2O3 and the A/CNK>1, belongs to highly-enriched kalium cale-alkaline and peraluminous granite. The trace elements are characterized by enrichment of LILE(La, Zr, Pb, Rb, U, Th), depletion of HFSE(Nb, Ta) and incompatible elements(Sr, Ba, Ti). It has highly total rare earths element and the negative Eu anomalies are a little strong. LA-ICP-MS zircon U-Pb isotopic age of the mineralization granite is between 84Ma-93Ma, it is approaching to the main mineralization age of Late Cretaceous magmatic belt of western South China. It belongs to S-type granite, formed by the magma of argillite rocks in a continental collision tectonic setting. The content of ore-forming element is high, mainly be the source of the orebodies.Skarn in the Xiaopingba deposit is produced in the contract or the fracture and fissures in the upper layer wall rocks. It can be fall into scheelite skarn, banded skarn and Pb-Zn metallized skarn based on the position and mineralization. Their major elements, mineral composition and the structure are different. But the feature of rare earth, trace elements are similar to the granite. Geochemical characteristics show that magmatic hydrotherm has significant material exchange with carbonate rock in the process of ore-forming granite intrusion. Si, Fe, Al, REE and ore-forming element Sn, Co, V, Zn, Ni, W transferred into the carbonatite, Ca, Mg in the carbonatite moved into the fluid and gathering. Scheelite skarn or ore, banded skarn and Pb-Zn mineralized skarn were formed in the double metasomatism process. Meanwhile, HFSE(Ta, Hf, Zr, Nb) and LILE(K, Ba, Cs, Pb, U, Rb, Sr) were gathered in the hydrotherm. The intensity of Skarn is mainly controlled by the granite and the atmospheric precipitation infiltration. Around the granite, the metallization was mainly affected by the pyrogenic rock. But as the distance increase, the function of meteoric water was enhanced.