| The south Miaomiaojing W-Be deposit is located in the Beishan mountain system at the border of Gansu Province and Xinjiang Province, and is located in the northern margin of Liuyuan Rift active belt of Dunhuang Block, Tarim Plate.There are few reports on magmatic diagenesis and mineralization in this region. In order to find out the mineralization characteristics of Miaomiaojing south deposit, the types, genesis and source characteristics of granite, clarify the diagenesis and mineralization age, explore the relationship between diagenesis and mineralization, and reveal the metallogenic dynamic background, In this paper, a systematic study of lithography, chronology, petrogeochemistry, zircon Lu-Hf, Nd-Pb isotopes and so on has been carried out on the granite in the south Miaomiaojing mining area. The results show that the exposed rock mass is mainly monzonitic granite, and the zircon U-Pb age is 411~404Ma, which is late Paleozoic and early Devonian magmatic rock. Enrichment of Si and Al elements, A/CNK ranges from 0.89 to 0.99, quasi-aluminous rocks, Ritman index 2~2.6, belong to high potassium calc alkaline series; Large ion-lithophilic elements (LILE) such as Rb and U are enriched in trace elements, and high field-strength elements (HFSE) such as Nb and Ti are depleted to varying degrees. The distribution curve of rare earth elements is skewed to the right, that is, light rare earth is enriched (LREE) and heavy rare earth is depleted (HREE), with strong negative Eu anomaly. Ziron (176Hf/177Hf)i ranges from 0.282466 to 0.282914, εHf(t) ranges from -2.78 to +12.78, with an average value of 6.36 and a median value of 6.40. TDM2 ranges from 559-1544Ma. (143Nd/144Nd)i ranges from0.512092 to 0.512210, εNd(t) values from -0.5 to +1.8 with an average value of 0.37, (206Pb/204Pb)i=16.793 to 18.516, (207Pb/204Pb)i=15.540 to 15.642, (208Pb/204Pb)i=36.882~38.484. The isotope test results show that the granite may be derived from the partial melting of the new lower crust with the characteristics of depleted mantle, and mixed with the old crust of the Palaeoproterozoic Beishanite group during the ascent. Comprehensive studies show that the granite in Miaomiaojing South mining area belongs to high differentiation type I granite, and its genesis may be related to the subduction-collision of Zoolen Ocean and Beishan orogenic belt in the south of Central Asia orogenic belt in the Early and Middle Devonian of Late Paleozoic. The whole area is in the backarc extension-tectonic background, the asthenosphere upsurge, providing a lot of heat, resulting in partial melting of the new lower crust, basic-neutral magma continuously invading along the fault, and contact metasomatism with carbonate rock surrounding rock to form skarn-type W-Be deposit. |