Zircon U–Pb and pyrite Re–Os age constraints on pyrite mineralization in the Yinjiagou deposit, China

Abstract

We report new zircon U–Pb and pyrite Re–Os geochronological studies of the Yinjiagou poly-metallic deposit, sited along the southern margin of the North China Craton (SMNCC). In this deposit, pyrite, the most important economic mineral, is intergrown/associated with Mo, Cu, Au, Pb, Zn, and Ag. Prior to our new work, the age of chalcopyrite–pyrite mineralization was known only from its spatial relationship with molybdenite mineralization and with intrusions of known ages. The U–Pb and Re–Os isotope systems provide an excellent means of dating the mineralization itself and additionally place constraints on the ore genesis and metal source. Zircons separated from the quartz–chalcopyrite–pyrite veins include both detrital and magmatic groups. The magmatic zircons confine the maximum age of chalcopyrite–pyrite mineralization to 142.0 ± 1.5 Ma. The Re–Os results yield an age of 141.1 ± 1.1 Ma, which represents the age of the chalcopyrite–pyrite mineralization quite well. The common Os contents are notably low (0.5–20.1 ppt) in all samples. In contrast, the Re contents vary considerably (3.0–199.2 ppb), most likely depending on intensive boiling, which resulted in an increase of Re within the pyrite. This study demonstrates that the main chalcopyrite–pyrite mineralization occurred late in the magmatic history and was linked to a deeper intrusion involving dominant mantle-derived materials. This mineralization event might be related to the Early Cretaceous lithospheric destruction and thinning of the SMNCC.

Keywords:

• zircon U–Pb dating
• Re–Os isotopic age
• pyrite
• Yinjiagou deposit
• southern margin of the North China Craton

Acknowledgements

We thank Xianhua Li, Qiuli Li, and Guoqiang Tang for their technical support during the analytical work. Thoughtful suggestions by Editor W.G. Ernst and reviewer Z.Q. Hou greatly helped to improve the article. This research was funded jointly by the National Basic Research Programme (No. 2012CB416601) and NSFC grants (No. 41202066). M.T. Zhu is grateful for the support from the China Postdoctoral Science Foundation grant (No. 2011M500386).