Fluid evolution and large-scale gold metallogeny during Mesozoic tectonic transition in the Jiaodong Peninsula, eastern China

Abstract

The Jiaodong Peninsula or eastern Shandong Province, the most important gold producing in region China, is located in the southeastern margin of the North China Craton. The gold deposits in the Jiaodong Peninsula are divided into three gold belts, from west to east, the Zhaoyuan–Laizhou, Penglai–Qixia and Muping–Rushan belts. The deposits occur as gold-bearing quartz veins and disseminated- and stockwork-style ores adjacent to fault zones. Most of the gold deposits can be classified in four stages: stage I, quartz–(minor) pyrite; stage II, pyrite–quartz–gold; stage III, quartz–base metal sulphide minerals; stage IV, quartz–carbonate. Ar–Ar ages, Rb–Sr isochrons, and hydrothermal zircon sensitive high-resolution ion microprobe U–Pb ages obtained from these deposits suggest a gold mineralization time of 120±10 Ma. The Sr–Nd isotopic compositions of pyrites and the associated rocks suggest that the ore-forming materials were probably derived from a mixed source. Fluid inclusion studies show that ore-forming fluids of gold deposits are consistent throughout the Jiaodong Peninsula, with similar mineralizing temperature and pressure conditions. Ore-forming fluids are characterized by H2O–CO2–NaCl±CH4. The optimal mineralizing temperature and pressure ranges are 170–335 °C and 0.7–2.5 kbar. Oxygen and hydrogen isotope data show that ore fluids are of magmatic origin. Gold deposits in the Jiaodong Peninsula formed in the same mineralizing–geodynamic conditions, and are related to the Mesozoic tectonic transition in the eastern North China Craton. Gold metallogeny is only one expression of the Mesozoic tectonic transition.

Rb-Sr Isotopic Geochronology and Geological Implications of Dongfeng Gold Deposit in Jiaodong Area

“…In recent studies, by using Rb-Sr, Ar-Ar, and SHRIMP U-Pb isotope system of ore minerals, the ages of the representative deposits in the Jiaodong gold-centralized area have been obtained (Table 3). The statistical results show that the ages of representative deposits are similar and range from 128 to 115Ma, indicating these deposits mainly formed from the late Jurassic to early Cretaceous, which is consistent with the previous conclusions of the time of the large scale gold metallogeny in the Jiaodong area (Fan et al, 2005;Chen et al, 2004). The Rb-Sr isochron age of the beresite from the Dongfeng gold deposit in this study is 125.5±6.7 Ma.…”

“…The Rb and Sr isotopic analysis are an effective tool to discuss the source of ore-forming materials (Fan et al, 2005;Medford et al, 1983;Bell et al, 1989;Darbyshire et al, 1996). Also, the Isr value is considered as an important indicator to discriminate the properties of the source of ore-forming materials (Tu et al, 1982;Wang and Zhou, 2002); the Isr value is less than 0.705 for the mantle source, the Isr value is more than 0.709 for the crustal source.…”

“…Based on the studies of the gold deposit geochronology, , Wang et al (2000) and Chen et al (2004) implied that gold mineralization occurred in the Mesozoic and concentrated from 128 to 115 Ma. Regarding the ore-forming fluids, Fan et al (2005) suggested that ore-forming fluids of gold deposits were consistent throughout the whole Jiaodong area under similar mineralizing temperature and pressure conditions and the fluids were characterized by H2O-CO2-NaCL±CH4, with low salinity and low-to-moderate temperature. Moreover, Mao et al (2005) pointed out that mantle fluids were associated with the gold mineralization.…”

Fluid evolution in the Rushan lode gold deposit of Jiaodong Peninsula, eastern China

“…Nature of ore fluids at Rushan deposit is similar to that of gold deposits from other belts in the Jiaodong Peninsula (Fan et al, 2005). The consistency of oreforming fluid nature and mineralization ages suggests that Rushan gold deposit was formed at the same single metallogenic event as other gold deposits in the Jiaodong Peninsula at 120 ± 10 Ma, and also validates the model on tectonic regime inversion, lithosphere thinning, and large-scale metallogeny .…”

Tectonic evolution of the North China Block: from orogen to craton to orogen

“…Widespread 147-112 Ma magmatism included the intrusion of adakites, reflecting subduction of perhaps as many as three distinct slabs (Xu 1990;Zhang, L. C., et al 2000;Davis et al 2001;Wang et al 2001;Zhang, Q., et al 2001;Wei et al 2002;Davis, 2003;see also Castillo 2006). The formation of China's most important gold vein deposits occurred at the same time along the northern, eastern, and southern margins of the Eastern Block (Mao et al 1999;Zhou et al 2002;Yang, J.-H. et al 2003;Fan et al 2007). Unroofing of many metamorphic core complexes (c. 140-105 Ma), products of SE-NE extension (Niu 2005;Zhang et al 1994;Zheng et al 1998Zheng et al , 2001Zhang, Y. Q. et al 1998;Webb et al 1999;Zhang, Q., et al 2001;Davis et al 2002;Darby et al 2006;, and major animal extinctions were also significant in this period (Chen et al 1997;Wang et al 2001).…”