Paleozoic rapid denudation of the Proterozoic Jinchuan Ni-Cu-PGE sulfide deposit, NW China: Insights from single-grain zircon (U-Th)/He thermochronology

Abstract

The Proterozoic Jinchuan Ni-Cu-PGE sulfide deposit is one of the three largest magmatic sulfide deposits on the earth which was formed in either the Mesoproterozoic or Neoproterozoic. After mineralization of the giant Jinchuan Ni-Cu-PGE orebody, orogenic movements occurred frequently and strongly in a large-scale area. However, less is known on how the deposit denudated after mineralization yet. In this study, we report a new finding of the rapid uplift and denudation event during Late Paleozoic which is supported by single-grain zircon (U-Th)/He dating of 7 samples with elevations ranging between 1453 m and 2180 m collected from a vertical profile in the Jinchuan area. The numerical dating results cluster within 341.08 ± 14.63 – 262.60 ± 29.10 Ma for 7 samples with elevations ranging between 2180 and 1453 m, and 154.74 ± 11.54 Ma for the lherzolite with elevation of 1220 m. Confined with the published 40Ar-39Ar data, the inverse modelling results support that the Jinchuan deposit underwent a rapid cooling at ∼320 Ma. The numerical dating and inverse modelling results obtained in this study support that the Jinchuan deposit and adjacent area experienced a rapid uplift during 341 – 262 Ma (Late Paleozoic). The rapid denudation during the Late Paleozoic is likely a response to the southward subduction of the Paleo-Asian Ocean, inferred from the regional orogenic movements and magmatism in the adjacent areas. Besides, the zircon (U-Th)/He age of 154.74 ± 11.54 Ma obtained from lherzolite supports a cooling event which is to be further studied.