Geochemical Characteristics And Metallogenic Potential Of The Cretaceous Complex Pluton In The Xiongba Of The Bangong Co-Nujiang Metallogenic Belt

The Xiongba Basin is located in the western part of the Lhasa block south of the Bangong Co-Nujiang suture zone and can be classified as the Bangong Co-Nujiang metallogenic belt in a broad sense.The object of this study is a complex pluton exposed in the Xiongba Basin.It attempts to reflect the rock's geochemical characteristics through detailed field surveys,indoor petrographic observations,and isotope geochronology and geochemistry.Forecast the metallogenic potential of the Xiongba Basin.The exposed area of the Xiongba complex pluton is 33 square kilometers.The quartz porphyry was later covered by unconformable eruptions of the volcanic rocks of the Linzizong Group and Yulinshan Group.The LA-MC-ICP-MS zircon U-Pb dating,Whole rock geochemistry test obtained the following result:?1?The Xiongba complex pluton consists of two stages of magmatic rocks:granite porphyry and quartz porphyry,zircon ²⁰⁶Pb/²³⁸U concordia age was 149.7±1.3 Ma and 90.2±1.2 Ma.?2?The major element and trace element characteristics show that the Xiongba complex pluton granite porphyry is a highly fractionated"S"type granite,and the Xiongba complex pluton quartz porphyry is an unfractionated"S"type granite.?3?The map of original mantle standard spider net and the?La/Yb?_N-La correlation diagram of the quartzite porphyry and granite porphyry in the Xiongba complex pluton indicate that it may have undergone crystallization of plagioclase+K-Feldspar and accessory minerals apatite,rutile,allanite separation and crystallization process.?4?The Xiongba complex pluton granite porphyry may form in the background of the Neo-Tethyan ocean northward-subduction.The quartz porphyry may form in the short stress relaxation stage after the collision between the Lhasa block and the southQiangtang terrane.The geochemical study of the Xiongba complex pluton indicates that the conditions of the formation of highly-fractionated granites in the Xiongba Basin may form W-Sn-Nb-Ta polymetallic deposits related to high-fractional granites.