Tungsten Mineralization Mechanism Of The Xingjiashan Skarn Deposit In Jiaodong Mesozoic Metallogenic Aera,China

The Xingjiashan W-Mo deposit is the only large-scale skarn-type molybdenum polymetellic deposit in the Mesozonic metallogenic area of Jiaodong.In this paper,the author study the tungsten mineralization in the Xingjiashan deposit,and carry out research work on the Xingfushan Granite and skarn of the ore district.Through a series of analytical methods as petrogeochemistry,mineralogy,fluid inclusions and stable isotopes to trace the characteristics of fluid mineralization and explore the source of ore-forming materials,analysis of the tungsten and molybdenum symbiotic mechanism.The Xingfushan granite is the ore-forming mother rock of the Xingjiashan deposit,which belongs to intermediate-acid igneous rock.The Feature of trace elements show that the Xinfushan granite come from crust-mantle mixed magma.The typical mineralogical characteristics show that the tungsten in the Xingjiashan deposit is mainly found in the scheelite,which is star-like or disseminated with the typical skarn minerals such as garnet and pyroxene.According to the EMPA analysis,the tungsten content in this deposit is a little lower than the theoretical value of scheelite,indicated that some lattice position of the tungsten was replaced by molybdenium.Tungsten-molybdenium ore-forming fluids in the Xingjiashan deposit belongs to a H₂O-Na Cl±CO₂ system,with high temperature,moderate-low salinity.The mainly temperature and salinity ranges in each stage are:360?-406?,6%-10%in the early skarn stage;280?-350?,3.62%-9.98%in the late skarn stage and 239?-288?,5.4%-10.1%in the quartz-scheelite stage,respectively.There are two obvious stages in scheelite metallogenic period.Meanwhile,the results of S isotopes indicate the magmatic origin of the ore forming fluid.Sm-Nd isotopes show the crustal origin of tungsten mineralization.The tungsten was carried by the Xingfushan granite from the deep crust.Because of the changes in the metallogenic environment,the WO₄^2-reacted with Ca²⁺in the carbonate rock led to the formation of scheelite.The formation of tungsten and molybdenum from the similar deep origin showed that the mineralization environment was changing.In addition,H-O isotopes also indicated the addition of atmospheric water in metallogenic stage.