GEOLOGICAL CHARACTERISTICS AND METALLOGENIC AGE OF THE LARGE SILVER-LEAD-ZINC DEPOSIT IN HALASHENG OF MANZHOULI AREA, INNER MONGOLIA

This Ag-Pb-Zn deposit is occurred in the Halasheng volcanic dome, with mineralization closely related to volcano-magmatism. The drilling and high-precision magnetic data show that the volcanic basement is the Ergunahe Formation, with subvolcanic body as the core of the dome and the volcanic-sedimentary cap rocks of Tamulangou and Manketouebo formations as ore-host rocks. The delineated 11 orebodies in the northeast of the dome are controlled by the N-S-trending extensional fault/fracture with steep occurrence. The four main orebodies are 500-1400 m long with an average thickness of 1-3 m and general depths of 500-900 m. The geochemical anomaly element assemblages from the rock body to surrounding rocks are in the order of Bi(-Pb-Ag-As-Mo)→Ag-Pb-Mo-Cu→Pb-Zn-As→Ag-Pb-Zn-Sb→Ag-Pb-Zn-Sb. The mineralized element associations are Cu (-Mo-Pb-Zn)→Pb-Zn-Ag→Pb-Ag in sequence. The wallrock alterations from inside to outside of the rock body are silicification→potash feldspathization→quartz sericitization→skarnization→chalcedonization→epidotization→chloritization→ carbonation successively. The zircon U-Pb isotopic age of 3 magmatic rock samples is 161-142 Ma. Combined with the research of regional typical deposits, it is believed that the diagenesis and mineralization occurred in Late Jurassic to Early Cretaceous with a metallogenic age of 142 Ma.