Geochemistry, zircon U-Pb analysis, and fluid inclusion Ar-40/Ar-39 geochronology of the Yingchengzi gold deposit, southern Heilongjiang Province, NE China

摘要

The Yingchengzi gold deposit, located 10 km west of Shalan at the eastern margin of the Zhangguangcai Range, is the only high commercially valuable gold deposit in southern Heilongjiang Province, NE China. This study investigates the chronology and geodynamic mechanisms of igneous activity and metallogenesis within the Yingchengzi gold deposit. New zircon U-Pb data, fluid inclusion Ar-40/Ar-39 dating, whole-rock geochemistry and Sr-Nd isotopic analysis is presented for the Yingchengzi deposit to constrain its petrogenesis and mineralization. Zircon U-Pb dating of the granite and diabase-porphyrite rocks of the igneous complex yields mean ages of 471.7 +/- 5.5 and 434 +/- 15Ma respectively. All samples are high-K calc-alkaline or shoshonite rocks, are enriched in light rare earth elements and large ion lithophile elements, and are depleted in high field strength elements, consistent with the geochemical characteristics of arc-type magmas. The Sr-Nd isotope characteristics indicate that the granite formed by partial melting of the lower crust, including interaction with slab-derived fluids from an underplated basaltic magma. The primary magma of the diabase-porphyrite was likely derived from the metasomatized mantle wedge by subducted slab-derived fluids. Both types of intrusive rocks were closely related to subduction of the ocean plate located between the Songnen-Zhangguangcai Range and Jiamusi massifs. However, fluid inclusion Ar-40/Ar-39 dating indicates that the Yingchengzi gold deposit formed at similar to 249 Ma, implying that the mineralization is unrelated to both the granite (similar to 472 Ma) and diabase-porphyrite (similar to 434 Ma) intrusions. Considering the tectonic evolution of the study area and adjacent regions, we propose that the Yingchengzi gold deposit was formed in a late Palaeozoic-Early Triassic continental collision regime following the closure of the Paleo-Asian Ocean. In addition, the Yingchengzi deposit could be classified as a typical orogenic-type gold deposit occuring in convergent plate margins in collisional orogens, and unlikely an intrusion-related gold deposit as reported by previous studies. Copyright (C) 2015 John Wiley & Sons, Ltd.