Recycling of palaeo-Pacific subducted oceanic crust related to a Fe–Cu–Au mineralization in the Xu-Huai region of North Anhui-Jiangsu, East China: Geochronological and geochemical constraints

ABSTRACT

In this study, Early Cretaceous skarn deposits and genesis of their host diorite/monzodiorite porphyry in the Xuzhou-Huaibei (Xu-Huai) region, northern Anhui-Jiangsu have been discussed by detailed geochemical work. In-situ zircon U–Pb dating of the diorites related to Fe–Cu–Au deposits shows that they were formed between 131.4 ± 1.5 Ma and 130.8 ± 1.8 Ma. Geochemical data indicate a depletion of high field strength elements (HFSE) in the diorite porphyry with similarity to that of arc-related igneous rocks. The diorite porphyry was probably derived from typical arc magmas related to continental margin subduction characterized by light rare earth elements (LREEs) enrichment and HFSE depletion. REEs compositions of apatite in the diorite porphyry indicate that the dioritic magma was produced from the metasomatized subcontinental mantle by slab-derived fluids. The magma was proven to be a high oxygen fugacity; thus, it was particularly conducive to the precipitation of Fe, Cu, Au and other ore-forming elements. The δ³⁴S values of pyrite and chalcopyrite of Fe–Cu–Au ores range from −0.2‰ to 2.8‰, indicating that the sulphur in the ore was probably derived from deep-seated magmas. Integrated with geochronological and geochemical analyses, we suggest that the Early Cretaceous igneous suites associated with Fe–Cu–Au deposits in the Xu-Huai region are related to recycling subduction of Pacific oceanic crust.

KEYWORDS:

• Diorite
• monzodiorite
• zircon U–Pb dating
• Fe–Cu–Au deposit
• Xu-Hai region
• palaeo-Pacific subduction

Acknowledgements

This study was supported by DREAM Project of MOST of China (number 2016YFC0600404) and the National Natural Science Foundation of China (numbers 41372087, 41673040).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by DREAM Project of MOST of China (number 2016YFC0600404) and the National Natural Science Foundation of China (numbers 41372087, 41673040).