Age and tectonic setting of vein-type mineralization of Hongtaiping copper polymetallic deposit in Yanbian area, Jilin Province, NE China

The Hongtaiping copper polymetallic deposit in Yanbian area, Jilin Province of Northeast China, is tectonically located in the east margin of the Xing' an-Mongolian Orogenic Belt (XMOB). Two types of ore bodies have been identified in this deposit, including the stratiform Cu polymetallic ore body hosted by the Late Paleozoic volcanic sedimentary rocks, and the vein-type Pb-Zn ore body controlled by the intrusion and structures. To determine the mineralization age and tectonic setting of the vein-type ore body, LA-ICP-MS zircon U-Pb dating and petrogeochemical studies were carried out on the dacite associated with the vein-type mineralization, and Rb-Sr isotope dating of metal sulfides in the vein-type ore body was conducted. The isotope dating results indicate that the Pb-206/U-238 weighted mean age of the 28 zircon grains in the dacite is 204. 1 +/- 2. 0Ma (MSWD =0. 24), and the Rb-Sr isochron age of 4 metal sulfide samples is 206. 8 +/- 9. 0Ma (MSWD = 2. 0). Two groups of ages are nearly consistent and indicate that the vein-type Pb-Zn mineralization was formed at the end of Late Triassic Period. The dacite associated with the vein-type mineralization is characterized by the enrichment of light rare earth elements (LREEs), and fractional distillation of light and heavy rare earth elements [(La/Yb)(N) = 7. 59 similar to 8. 28], as well as weak Eu anomalies (delta Eu = 0. 65 similar to 0. 68). Trace elements in the dacite samples are characterized by the enrichment of large ion lithophile elements (LILEs: Rb, Ba and K) and incompatible elements (U and Th), the depletion of high field strength elements (HFSEs: Nb, Ta, P and Ti), indicating that the primary magma is originated from the crust-mantle mixed materials. The initial Sr isotope ratio (Sr-87/Sr-86), of 4 metal sulfide samples from the vein-type ore body is 0. 705954 to 0. 707101 (averaged at 0. 706390), implying that the ore-forming materials are derived from the crust-mantle mixed source. In the Rb-(Y + Nb) and La/Yb-Th/Yb diagrams, the tectonic environment of the dacite can be determined as the active continental margin. The dacite and vein-type Pb-Zn mineralization can be attributed to the tectonic-magmatism-mineralization event during the Late Triassic to the Early Jurassic (T-3-J(1)) resulted from the subduction of the Paleo-Pacific plate to beneath the Eurasia plate.