Typomorphism And Significance Of Apatite From The Granite In The Jiaodong And Xiaoqinling Regions

Apatite,as a kind of accessory mineral,exists widely in magmatite.Because of its early crystallization time,it is not easily affected by late geological processes,so it has great significance in the study of the source of magma,the redox degree ofmagma,the activity of magma fluid,and the mineralization of pluton.Many large and super-large gold deposits were formed in north China craton in Mesozoic,amongwhich jiaodong and xiaoqinling gold mining areas are the first and second largest gold mining areas in China.Most of the gold deposits in these areas were formed in early cretaceous,and magmatite of similar age were formed in or near the miningareas.Therefore,many scholars believe that the NCC gold mineralization is closelyrelated to the magmatite in this area.In order to know the characteristics of magmatite in the north China craton,this article selects Guojialing,Linglong,Wenyv,Huashan plutons;we use the mineralogical and geochemical characteristics of apatite as anindicator mineral,discussing the genetic characteristics of four plutons,comparing the similarities and differences of the Mesozoic granites related to gold mineralization in two gold mining areas,and analyzing the gold-forming potential of granites.Through the study of apatite in four plutons,it is found that they all belong to magmatic apatite.The P₂O₅ of apatite in Guojialing and Linglong plutons at jiaodong gold mining area is higher than the CaO of apatite is lower,while the P₂O₅ of apatite in Wenyu and Huashan plutons at Xiaoqinling gold mining area is lower but the CaO of apatite is higher.Petrographic characteristics of apatite and Li elements,?La/Gd?_N and?Gd/Yb?_N ratio and the characteristics of the halogen elements show thatGuojialing,Wenyv and Huashan plutons have strong fluid activity during thecrystallization of apatite,however,the fluid inactive during the crystallization of apatite in the Linglong pluton.The variable elements such as Eu,Ce,Mn,Ga and V in apatite can characterize the redox environment of plutons.Calculating with the Mn element,we found the average oxygen fugacity of Guojialing pluton is-10.54,Linglong pluton is-13.53,Wenyu pluton is 12.28,and the oxygen fugacity of huashan pluton except HS-4samples is-12.02,while the HS-4 samples is-16.32.The oxygen fugacity ofGuojialing,Wenyu and Huashan pluton except HS-4 samples all fell between in HM and NNO,Linglong and HS-4 samples fell between in NNO and FMQ.Combing the characteristics of other elements,it is indicated that Guojialing,Wenyu and Huashan pluton except HS-4 samples are all formed in a more oxidized environment,while Linglong and HS-4 samples are formed in a more reduced environment.In addition,the rare earth elements and Sr elements in apatite can characterize the magma source of the pluton and the fractionation process.Thechondrite-normalized rare earth elements patterns,Sr/Th and La/Sm all show that Guojialing,Wenyu and Huashan pluton except HS-4 samples are crust-mantlemixed-source granite,while the Linglong and HS-4 samples are belong tocrust-source granite.The ratio of?La/Sm?_N,?La/Yb?_N and?Sm/Yb?_N with Sr content in the apatite show that the apatite in the Guojialing and Huashan plutons arecrystallized together with the plagosclase,and the apatite in Linglong and wenyu plutons may be crystallized before or after the plagosclase.Analyzing the apatite mineralogy characteristics,main trace elements ofGuojialing and Linglong plutons show that apatite can be use to indicate the goldmineralization potential of pluton.So appling in Xiaoqinling gold province,we found that the Wenyu and Huashan plutons except HS-4 samples have similar potential,but the HS-4 samples reduce the gold mineralization potential of huashan pluton.