Depositional age and provenance of ore-hosting strata in the Dabaoshan copper polymetallic deposit,northern Guangdong Province:Implication on ore genesis
The Dabaoshan deposit is a large-sized polymetallic deposit in northern Guangdong province,South China,and consists mainly of porphyry-and skarn-type Mo-W mineralization and adjacent stratiform Cu-Pb-Zn mineralization.It has been debated for a long time whether the stratiform Cu-Pb-Zn mineralization is related to a Jurassic porphyry Cu-Mo system,or to a Devonian exhalative event with Jurassic overprinting.One of the key issues is that the depositional age of the ore-hosting strata and petrogenetic relationship to the layered volcanic rocks were not well constrained.In this paper,we conducted LA-ICP-MS zircon U-Pb dating and Hf isotope study for the ore-hosting strata in the Dabaoshan deposit.The results show that the youngest ages of detrital zircon from two ore-hosting strata samples yield 430±8 Ma and 431±4 Ma,whereas those from two footwall rocks samples of the layered volcanic rocks yield 239±3 Ma and 189±3 Ma,respectively.It suggests that the depositional age of the ore-hosting strata and footwall rocks of the layered volcanic rocks belongs to the Middle Devonian and the Early Jurassic,respectively.They were mainly derived from Neo-to Meso-proterozoic(1200～750 Ma)and Paleozoic(440～420 Ma)crust with minor input of Paleo-proterozoic(2500～1600 Ma)and Pan-African(650～520 Ma)material.In addition,the footwall rocks include the Late Paleozoic to the Early Mesozoic detrital zircons(340～210 Ma).The Hf isotopic signature suggests that these materials were mainly originated from recycled ancient crust and the Proterozoic juvenile crust.All above mentioned were the response to the early micro-continental evolution of the Cathaysia Block,amalgamation between the Yangtze Craton and the Cathaysia Block and their Phanerozoic evolution.The layered volcanic rocks were unconformable overlaid by the ore-hosting Devonian rocks,and they were both thrusting on the Jurassic clastic rocks.The stratiform Cu-Pb-Zn orebodies were suffering from the Devonian sedimentary exhalative,then overprinted by the Yanshanian magmatic-hydrothermal activity.
ore-hosting stratadetrital zirconU-Pb ageHf isotopecopper polymetallicDabaoshanGuangdong Province
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