Re–Os Pyrite Geochronological Evidence of Three Mineralization Styles within the Jinchang Gold Deposit, Yanji–Dongning Metallogenic Belt, Northeast China

Abstract

The Jinchang gold deposit is located in the eastern Yanji–Dongning Metallogenic Belt in Northeast China. The orebodies of the deposit are hosted within granite, diorite, and granodiorite, and are associated with gold-mineralized breccia pipes, disseminated gold in ores, and fault-controlled gold-bearing veins. Three paragenetic stages were identified: (1) early quartz–pyrite–arsenopyrite (stage 1); (2) quartz–pyrite–chalcopyrite (stage 2); and (3) late quartz–pyrite–galena–sphalerite (stage 3). Gold is hosted predominantly within pyrite. Pyrite separated from quartz–pyrite–arsenopyrite cement within the breccia-hosted ores (Py1) yield a Re–Os isochron age of 102.9 ± 2.7 Ma (MSWD = 0.17). Pyrite crystals from the quartz–pyrite–chalcopyrite veinlets (Py2) yield a Re–Os isochron age of 102.0 ± 3.4 Ma (MSWD = 0.2). Pyrite separated from quartz–pyrite–galena–sphalerite veins (Py3) yield a Re–Os isochron age of 100.9 ± 3.1 Ma (MSWD = 0.019). Re–Os isotopic analyses of the three types of auriferous pyrite suggest that gold mineralization in the Jinchang Deposit occurred at 105.6–97.8 Ma (includes uncertainty). The initial 187Os/188Os values of the pyrites range between 0.04 and 0.60, suggesting that Os in the pyrite crystals was derived from both crust and mantle sources.

Ore Genesis at the Jinchang Gold–Copper Deposit in Heilongjiang Province, Northeastern China: Evidence from Geology, Fluid Inclusions, and H–O–S Isotopes

“…The age of mineralization should be slightly younger, or similar to, the age of the igneous rocks. The newest radiometric age data for pyrite minerals, using the Re-Os method, give an isochron age of 102 Ma [18]. The geochronological data demonstrate that magmatism and hydrothermal activity were contemporaneous, which suggests that the granodiorite played an important role in gold mineralization.…”

“…From west to east, Northeast China can be further separated into the Erguna, Xing'an, Songnen, and Jiamusi-Xingkai blocks ( Figure 1A). The Jinchang district is within the Xingkai Block, which abuts against the eastern margin of the Songnen Block to the south of the Jiamusi Block [18]. The region records the prolonged tectonomagmatic evolution of the Paleo-Asian Ocean during the Paleozoic, and the subsequent Mesozoic subduction of the paleo-Pacific Plate [19].…”

“…The Re-Os isotopic compositions of 15 pyrite samples from breccia, vein, and stockwork mineralization yield Re concentrations of 1185-10,475 ppt and Os concentrations of 3-15 ppt. The 187 Re/ 188 Os ratios range from 3527 to 42,853, and the initial 187 Os/ 188 Os ratio ranges from 0.04 to 0.60 [18], indicating that the ore-forming materials were a mixture of crust-and mantle-derived fluids.…”

“…The study area forms part of the Pacific Ocean tectonic domain, and mineralization of the Jinchang deposit occurred during the Early Cretaceous [18]. During this period, the Izanagi Plate was being subducted beneath the Eurasian Plate.…”

“…187 Re/ 188 Os ratios range from 3527 to 42,853, and the initial 187 Os/ 188 Os ratio ranges from 0.04 to 0.60 [18], indicating that the ore-forming materials were a mixture of crust-and mantle-derived fluids.…”