Constraints on the timing and genetic link of the large-scale accumulation of proximal W-Sn-Mo-Bi and distal Pb-Zn-Ag mineralization of the world-class Dongpo orefield, Nanling Range, South China

摘要

The world-class Dongpo orefield, located in the Nanling Range, South China, is famous for its large-scale accumulation of W-Sn-Mo-Bi-Pb-Zn-Ag deposits, which includes the giant Shizhuyuan W-Sn-Mo-Bi, Jinchuantang Sn-Bi, Yejiwei Sn-Cu and Congshuban Pb-Zn-Ag deposits. The polymetallic mineralization around the Qianlishan pluton exhibits systematic zoning and comprises proximal W-Sn-Mo-Bi skam-greisen and distal Pb-Zn-Ag veins. However, the timing and genetic link of its proximal skam-greisen W-Sn-Mo-Bi and distal vein-type Pb-Zn-Ag mineralization are not well constrained. Here, we present systematic geochronological data to constrain the geochronological framework and genetic model of the giant Dongpo orefield. The muscovite Ar-40-Ar-39 age of the greisen-type ore in the Shizhuyuan W-Sn-Mo-Bi deposit is 151 +/- 1 Ma, which is consistent with the formation of the skarn-type ore and the Qianlishan pluton, thus indicating that they are genetically related and both formed contemporaneously at similar to 151 Ma. The large-scale accumulation of W-Sn-Mo-Bi in the Shizhuyuan deposit may have occurred in a short duration of similar to 1 Ma. The muscovite Ar-40-Ar-39 ages (155.5 +/- 1.1 and 156.8 +/- 1.1 Ma) and molybdenite Re-Os age (153.8 +/- 4.2 Ma) of the Ma'naoshan W-Sn-Fe-Mn-Pb-Zn deposit, as well as the zircon U-Pb age (152.7 +/- 0.9 Ma) of the Yejiwei Sn-Cu deposit in the Dongpo orefield, are consistent with the age of the Qianlishan pluton, thus indicating that the proximal skam-greisen W-Sn-Mo-Bi mineralization in the Dongpo orefield is genetically related to the Qianlishan pluton. In addition, the Rb-Sr dating of sphalerite indicates that the vein-type Pb-Zn-Ag mineralization in the Congshuban area formed at 152 +/- 2Ma, which is consistent with the LA-MC-ICP-MS zircon U-Pb age (156-155 Ma) of the equigranular biotite granite, indicating that the distal vein-type Pb-Zn-Ag mineralization is genetically associated with the Qianlishan equigranular biotite granite. By integrating the high-precision geochronological data of this study with those of previous studies, the new genetic model of the large-scale accumulation of W-Sn-Mo-Bi-Pb-Zn-Ag in the Dongpo orefield suggests that the proximal skarn-greisen W-Sn-Mo-Bi and distal vein Pb-Zn-Ag mineralization in the Dongpo orefield are genetically related to the Qianlishan pluton and that the mineralization type is mainly controlled by the characteristics of the wall rock.