Age, sediment source and tectonic setting of the ore-hosting Jinwozi Formation at the Jinwozi gold deposit in Beishan Orogen, NW China: Evidence from detrital zircon U-Pb ages and Lu-Hf isotopes

摘要

The Jinwozi deposit is the most economically important gold (Au) deposit in the Beishan Orogen (Eastern Xinjiang, NW China). The Au orebodies occur as quartz veins or altered lodes in the Jinwozi Formation clastic rocks and the Jinwozi granite. The age, detrital source and tectonic setting of the Jinwozi Formation, however, have not been well understood. In this paper, we reported new LA-ICP MS detrital zircon U-Pb ages and Lu-Hf isotopes of ore-hosted clastic rock of the Jinwozi Formation. Detrital zircons from three samples yield 334 U-Pb ages varied from 330 to 2598 Ma, showing complex detrital sources. The youngest detrital zircon population suggests that the Jinwozi Formation deposited no earlier than 330 Ma in the Late Carboniferous or Permian. The majority of the detrital zircons (291 out of 334) have ages between 330 and 533 Ma, suggesting a dominant Paleozoic detrital source. Much of these age data (282 out of 334) range from 470 to 370 Ma, broadly coeval with the zircon U-Pb ages of the Jinwozi granite. Zircon Hf isotope data also implicate their similar origin to the Jinwozi granite. The source rocks, as well as the Jinwozi granite, may have formed in the Early Paleozoic Caledonian Orogeny, during which the supercontinents of Gondwana and Laurasia assembled. This orogeny process may have provided plenty of detritus for the clastic rocks of the Jinwozi Formation. Precambrian detrital zircon ages from the Jinwozi Formation cluster around 2400-2600 Ma, 1800-2100 Ma, 800-1300 Ma, which corresponds to the supercontinent assembly events of Kenor, Columbia and Rodinia, respectively. The age populations of 2200-2300 Ma and 600-660 Ma are possibly related to the breakup of Kenor and Rodinia supercontinents. This understangding is supported by zircon Hf isotope data.