Abstract:

The Lanping basin is a significant Pb-Zn-Cu-Ag mineralization belt of the Sanjiang Tethyan metallogenic province in
China. A series of sediments-hosted Himalayan Cu-Ag-Pb-Zn polymetallic deposits have been discovered in the western part of the
basin, which are controlled by a thrust-nappe system. In the thrust-nappe system, the Cu orebodies occur as vein-type deposits in the
western and relatively deep part of the mineralization system (the root zone), mainly including the Jinman Cu-Ag deposit, Liancheng
Cu-Mo deposit, and more than 30 small vein copper deposits, such as Kedengjian, Huangbai, and Enqi. The Pb-Zn-Ag(± Cu)

orebodies mainly occur in the eastern and relatively shallow part of the system (the front zone), including the Baiyangping
Pb-Zn-Ag-Cu ore belt, and some small Ag-bearing Pb-Zn deposits, such as Liziping and Wudichang. To define the metallogenic
history of the Cu-Ag-Pb-Zn polymetallic deposits in western Lanping basin, we dated nine calcite samples associated with copper
sulfide from the Jinman Cu deposit by the Sm-Nd isotopic analysis and five molybdenite samples from the Liancheng Cu-Mo deposit
by the Re-Os isotopic analysis. The nine calcite samples yielded an age of 58.2 ± 5.3 Ma (2σ, MSWD = 0.039). The five molybdenite
samples yielded an isochron age of 47.8±1.8 Ma (2σ, MSWD=7.2). The Sm-Nd isotopic age of calcites from the Jinman deposit (58 ±5 Ma)
and the molybdenite Re-Os age for the Liancheng deposit (48 ± 2 Ma), together with previously published chronological data,
demonstrate that (1) the main Cu-Ag (Mo) mineralization in the root zone took place at ca. 56~48 Ma, corresponding to the
main-collisional stage of the Indo-Asian collision orogeny; Possibly, there was a remobilization or a new phase of Cu mineralization in
the duration from 35 to 47 Ma; (2) The main Pb-Zn-Ag (± Cu) mineralization in the front zone took place at ca. 31~29 Ma,
corresponding to the late-collisional stage of the Indo-Asian collision orogeny.

Key words: Mineralization epoch, Calcite Sm-Nd age, Molybdenite Re-Os dating, Cu-Ag (±Pb-Zn) polymetallic deposits, western
Lanping basin