| The Yuansha Mo deposit is a newly discovered Mo polymetallic ore deposit in Zhangping city,Fujian Province.The deposit is located at the junction of the Zhenghe-Dapu and Lianjiang-Yongding fault zone,centre part of the Southwestern Fujian Depression Belt?SFDB?,eastern Cathaysia Block.The SFDB occurred the large-scale emplacement of granitic magma during the early stage of the Cretaceous?140Ma130Ma?,which may result from the extension tectonic setting of the South China triggered by the subduction direction changes of the Pacific plate.In this paper,we present the Re-Os isotopic dating results for molybdenite,the Geochronologic and whole-rock geochemical data for the ore-related granitoid,which provide insights into the relationship between the magmatism and the mineralization in the SFDB.The igneous rocks in Yuansha Mo deposit are dominated by the porphyritic granite and fine-grained quartz diorite,and the former is the major Mo-bearing rocks.the LA-ICPMS zircon U-Pb results show the porphyritic granite and fine-grained quartz diorite were formed at 131±1.9Ma and 126±1.9Ma,respectively.They all belong to metaluminous,high K calc-alkaline I-type granites.They share the similar REE patterns and trace elements characteristics that LREE-enriched,HREE-deplted,weak negative Eu anomalies,enriched in LILE?e.g.K,Rb,Th,Cs,Pb,U?,depleted in HFSE?e.g.Nb?Ta?P?Ti?.Comparatively,the porphyritic granite have higher SiO2contents,ranging from 70.64 wt.%72.79 wt.%,indicating they experience higher fractional crystallization.Moreover,it occurred numerous dioritic mafic microgranular enclaves?MMEs?.The origin of the porphyritic granite may dominated by the partial melting of the crustal rocks mixing with minor mantle materials,and later experience higher degrees of fractional crystallization.The quartz diorite posses relative lower SiO2 contents,which ranges from 56.34 wt.%59.48 wt.%.We suggest the quartz diorite was formed by mixing of mantle magma and some continental crust components.The Mo contents in the porphyritic granite is largely higher than that of granitoid rocks in SFDB,revealing the Mo may originated from the host porphyritic granite.The Re contents in molybdenite ores are 16.75×10-6,suggesting the ore-forming materials were dominated by the crustal origins.Comparison with coeval granite-related deposits in SFDB,we suggest the Mo mineralization are of multistage in Yuansha Mo deposit,and close related to the emplacement of granitic magma at ca.131Ma.The intrusion of the late dioritic magma?Ca.126Ma?may supply the heat for the secondary mineralization event. |
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