Petrogenesis And Solidification Condition Of Early Cretaceous Mapeng Pluton In The North Taihang Mountain

Fuping Mapeng pluton located in the North Taihang Mountain,has close relationships with mineralization of the Shihu gold deposit.It intruded the Archean Fuping Complex,and is composed of quartz-diorite,granodiorite,and porphyritic monzogranite from the peripheral to central facies.All of them host mafic microgranular enclaves(MME).So far,the petrogenesis of the Mapeng pluton is still an argument of magma mixing,differentiation and partial melting of lower crust.It is significant for the genesis and magmatic process of zoned intrusions to study the genesis and relationships among every facies of Mapeng pluton.Likewise,as the metallogenic geologic body of Shihu gold deposit,whose genesis is crucial to understand the characteristics of gold mineralization in Early Cretaceous.We draw some major conclusions through petrography,zircon U-Pb geochronology,geochemistry,mineral chemistry,and Sr-Nd isotopic as followings:1.Petrographic observation shows that there are many typical textures in the host granite and MMEs,which can be explained by magma mixing.Such as acicular shape of the apatites and amphiboles,hyperthermal dissolution of the zircons in MMEs,resorption of quartzes in host granite as well as myrmekites composed of plagioclase and quartz.Geochemical and mineral chemical features of the host granite and MMEs indicate the petrogenesis of magma mixing which is further supported by the simulation of Sr-Nd isotopic.2.Compared with geochemical features of typical Adakites,Mapeng pluton shouldn't be defined as Adakite but High Ba-Sr granite.3.Cooling and solidification condition of each facies estimated by Zircon saturation Thermometer,amphibole-plagioclase thermometer,Al-in-amphibole barometer,amphibole-biotite thermobarometer and biotite oxygen fugacity calculation.The results show the conditions of pressure and temperature are decreased while the oxygen fugacities are increased gradually,impling that the Mapeng pluton is solidified sequentially from the peripheral to the central facies.4.Considering the plutons exposed in the North Taihang Mountains,their emplacement pressures decrease gradually from north to south.It is likely that the varieties of ore deposit can be attributed to the emplacement depth of relevant plutons.