LA-ICP-MS zircon U-Pb and sericite Ar-40/Ar-39 ages of the Songjianghe gold deposit in southeastern Jilin Province, Northeast China, and their geological significance

摘要

The Songjianghe deposit is a newly discovered altered gold deposit in the southeastern Jiapigou-Haigou Gold Metallogenic Belt (JHGMB) in southeastern Jilin Province of NE China. The host rocks were considered to be the Mesoproterozoic Seluohe Group, and the metallogenic epoch lacked accurate isotopic constraints. To determine the age and metallogenic setting of the deposit, we describe the geologic characteristics of the deposit and present the results of petrographic and geochronologic analyses of the host rocks and ores. The ore bodies are hosted within a suite of amphibolite facies metamorphic rocks superimposed by greenschist facies indicative of retrograde metamorphism. Zircon U-Pb dating results indicate that the host rocks belong to the Jiapigou Group that formed at the end of the Neoarchean (2543-2527 Ma). Subsequently, the rocks successively underwent metamorphism during the late Neoarchean (2521-2506 Ma), retrograde metamorphism caused by the closure of the Paleo-Asian Ocean during the late Permian to Early Triassic (262-250 Ma), and extension after the closure of the Paleo-Asian Ocean during the Late Triassic (231-210 Ma). Sericite Ar-40/Ar-39 dating results suggest that the Songjianghe deposit formed during the Late Jurassic between 157 Ma and 156 Ma. By combining these new insights with those of previous studies, we propose that the Songjianghe deposit is a mesothermal gold deposit and that mineralization occurred during the extensional period in the intermittent stage that followed the first subduction of the Paleo-Pacific Plate. All the gold deposits in the JHGMB formed from the late Permian to Early Cretaceous by multi-stage mineralization events that corresponded temporally with the tectonic evolution of the Paleo-Asian Ocean and the episodic subduction of the Paleo-Pacific Plate.