Field geology, geochronology, and isotope geochemistry of the Luyuangou gold deposit, China: Implications for the gold mineralization in the eastern Qinling Orogen

Gold deposits are closely related to accretionary processes. Gold mineralization in eastern China, however, is usually>100Ma younger than associated collisional orogeny and partly controlled by extensional tectonics. Being controlled by interbedded detachment faults, the Luyuangou hydrothermal deposit is a typical mineralization under extensional tectonic. We present mineral deposit geology, tectonic geology, LA-ICP MS zircon U-Pb age data, and Sr-Nd-Hf isotopic data for the Luyuangou ore vein and porphyritic dyke, with the aim of elucidating the metallogenesis. The morphological features and ages of zircons from the Luyuangou auriferous lode are similar to the anatectic zircons from migmatite within the Qinling Group (a metamorphic complex unit) of the North Qinling Terrane, indicating that the North Qinling Terrane may be one of the provenances. Although the major age peak of 453 +/- 13Ma (MSWD=3.3, N=12) cannot constrain the exact metallogenic timing, the data imply a possible link between the Luyuangou metallization and the North Qinling Terrane. Meanwhile, the weighted-mean age of post-ore porphyritic dyke postdates the Luyuangou gold mineralization at 121.1 +/- 1.5Ma (MSWD=0.21, N=14). The Sr-Nd-Hf isotopes of the Luyuangou auriferous lodes and post-ore porphyritic dyke exhibit prominent differences from those of the Taihua Group and Xiong'er Group and are similar to those of the Qinling Group, implying that the Qinling Group is likely the main ore-forming provenance of the Luyuangou gold deposit. The S-Pb isotopes of the main mineralization stage of the Luyuangou gold deposit indicate a distinct deep-seated source. According to comprehensive analysis, it is proposed that, during the early Mesozoic, the large-scale continental collision between the Yangtze and the North China Craton involved the underthrusting of the North Qinling Terrane beneath the North China Craton that led to intracontinental folding, thrusting, and thickening without inducing extensive mineralization or magmatic activity. During the late Mesozoic, the subduction of the Pacific Plate induced the instability of the thickened continental crust and the development of the regional extensional structures, large-scale crust-mantle magmatism as well as deep-seated or mantle-derived fluids dissolving materials from the Qinling Group that precipitated at the interbedded detachment faults.