The Petrogenesis Studies Of The Mesozoic Xiangyuan Tungstentin Deposit And Related Granites In Hunan Province

The Jiuyishan area is located in the southwest of southern Hunan and the junction of Hunan and Guangdong near the junction of Cathaysian plate and Yangtze plate.It is one of the important tungsten and tin mineralization prospects in Nanling area.The Jiuyishan granitic pluton is a granitic complex composed of the Caledonian and Yanshanian granites,and the granitic pluton is spread from west to east.In order to determine the age,genesis and evolution of Xiangyuan tungsten-tin deposit?Daao tungsten-tin deposit and Shizitou tungsten-tin deposit?and related granites?Jinjiling pluton and Pangxiemu pluton?,this paper analyzes the granite,greisen and quartz veins study by mineralogy,petrology,rock geochemistry and isotopic geochemistry have been carried out to find out the formation age of the ore body and surrounding rock,the division of diagenetic and mineralization period,which explores the genesis of the deposits and provides an important basis for the prospecting of the ore deposits and the further study of the regional metallogenic regularity and guiding the regional prospecting.LA-ICP-MS zircon U-Pb dating results show that the age of Jinjiling pluton formation is 156.4 ± 0.80 Ma 159.0 ± 0.45 Ma,and the age of Pangxiemu pluton is 146.0 ± 0.86 Ma 151.0 ± 0.61 Ma.Using the Ar-Ar isotope dating,the plateau age of the muscovite in the greisen of the Daao tungsten-tin deposit was 157.5 ± 0.98 Ma,and the isochron age of the Shizitou tungsten-tin deposit was 140.2 ± 1.5Ma by the Re-Os isotope dating method.It can be seen that the Jinjiling pluton and Daao tungsten-tin deposit,the Pangxiemu pluton and Shizitou tungsten-tin deposit have the same diagenetic and metallogenic age,there is no obvious time gap between rock and ore formation.Jinjiling pluton and Pangxiemu pluton granites are highly evolved peraluminous granite,and they can use the composition changes of mica and feldspar in granite to indicate their magmatic evolution and the process of change.With the evolution of magma,the content of F and Rb₂O in mica gradually increased,and the contents of TiO₂,FeO and P₂O₅ decreased,and the contents of SiO₂,Na2O and Al₂O₃ in feldspar gradually increased,and the content of TiO₂,K₂O and CaO decreased.K-feldspar gradually evolved into albite,plagioclase closer to Ab Endmember components,alkaline feldspar is closer to Or Endmember components.The content of compatible elements Rb,Cs,Nb and Ta in the mica gradually increased,while the contents of incompatible elements Y,Th and REE decreased,and the Pangxiemu pluton was much higher in Rb/Sr Ratio and significantly lower Nb/Ta,Zr/Hf ratio.It can be seen that the Pangxiemu pluton experienced a more intense and more complete magmatic differentiation process than the Jinjiling pluton,which obviously had higher magmatic evolution.The Sr-Nd isotopic results show that the two-stage model of the Jinjiling pluton and the Pangxiemu pluton granites are both mesoproterozoic and the products of the ancient crustal remelting with high maturity.H-O isotopic results show that the diagenetic and ore-forming fluids should be homologous,both of which are mixed with magmatic water and atmospheric precipitation.The results of Re content analysis in the monomallite of the molybdenite from the Shizitou tungsten-tin deposit show that the metallogenetic material may be mainly derived from the material of the earth's crust,which is the same as the source of diagenetic material.In summary,the composition of the major and trace elements in the Jinjiling pluton and the Pangxiemu pluton has a consistent change,and the Rb/Sr ratio and 87Sr/86 Sr of the Pangxiemu pluton are much higher than those of the Jinjiling pluton The pluton has almost identical initial Sr isotopic compositions with approximately the same negative ?Nd?t?values and the same Nd mode age T2DM;these characteristics indicate that the two rock mass are the product of the same parent magma separation crystallization,which comes from the elemental and Isotopic composition of the same magmatic source area,but the late Pangxiemu pluton has a higher degree of evolution.