Guo-Guang Wang

Spatiotemporal reconstruction of Late Mesozoic silicic large igneous province and related epithermal mineralization in South China: Insights from the Zhilingtou volcanic-intrusive complex

Silicic large igneous provinces (SLIPs) generally reflect large-scale melting of lower crustal materials and represent significant metal reservoirs. The South China Block-Coastal Region (SCB-CR) SLIP hosts several large epithermal deposits. To better understand these deposits, we document the spatio-temporal framework of the host SLIP across the SCB-CR. Using zircon U-Pb dating and geochemical and isotopic analysis, we identify four stages of emplacement. Stage 1 felsophyre (ca. 149 Ma) shows a chemical affinity to highly fractionated I-type granites. Stages 2 and 3 of low-Mg felsic volcanics (ca. 128 to 111 Ma) and stage 4 felsite (ca. 100 Ma) have higher eHf(t) and eNd(t) values than stage 1 felsophyre, suggesting a significant contribution of newly underplated juvenile crust to the magma sources. Stage 4 diabase (ca. 101 Ma) was likely produced by melting of subduction˗metasomatized asthenospheric mantle. Together with reliable published data, we build a new spatio-temporal framework of volcanics and infer that the majority of the SCB-CR SLIP was related to the gradual northwestward subduction of the Izanagi plate beneath South China in a continental arc setting during ca. 170 to 110 Ma, and minor contribution was from the eastward retreat of the subducting slab in a back-arc setting during ca. 110 to 90 Ma. We conclude that the large scale epithermal mineralization was generated by melting of the metal-rich, thin (30-40 km), newly underplated hydrous juvenile crust during the tectonic transition from arc to back-arc settings.

The Evolution of Ore‐forming Fluid of Maoping Lead‐Zinc Deposit, Zhaotong in Northeast Yunnan: the Evidence of Sphalerite‐hosted Fluid Inclusions

The Maoping zinc-lead deposit is one of the typical zinc-lead deposits in Northeast Yunnan District, located in the sagged Yunnan basin at the middle end of the Yangtze platform. This district has been the focus of extensive and intensive research for more than 40 years on its geology, geochemistry, geochronology, tectonics, ore-genesis and ore-prospecting. As ore-prospecting on deep orebody at recent years, the deposit has been a large-type one in this district. Prior to this study, many papers have been published on ore-prospecting, geology, tectonics, fluid inclusion studies of the Maoping lead-zinc deposit (Zou et al., 2004; Han et al., 2007; Hu et al., 2003; Hu Bin, 2004; Wang et al., 2009; Shentu et al., 2011). The fluid inclusion study was restricted to quartz, dolomite and calcite which paragenetic with ore minerals (Han et al., 2007).

Mapping of fluid, alteration and soil geochemical anomaly as a guide to regional mineral exploration for the Dehua gold orefield of Fujian Province, southeast China

The Dehua gold ore-field, located in the central-eastern Fujian Province, SE China, is an important part of the renowned Dehua-Youxi-Yongtai gold ore production area. The ore-field contains several low-intermediate sulphidation epithermal gold deposits and numerous gold-bearing mineralized bodies. The extensive presence of intensely altered rocks, suitable structural environment, acidic intrusions and volcanic-subvolcanic rocks indicates an important potential for epithermal gold mineralization. In this work, fluid inclusion homogenization temperature and alteration mapping was carried out by fluid inclusion microthermometry in quartz and identification of alteration minerals closely related to the known mineralization. The result shows the trend of temperature contour curves as well as the shape of low argillic alteration zones implying that the area north of Qiucun might be profitable for future mineral exploration. The fluid and alteration mapping, in combination with soil geochemical mapping, defines the architecture of the epithermal-porphyry ore-forming system in the Dehua ore-field. Finally, the presence of intensely altered areas, high value zones of hydrothermal fluid flows and combined anomaly areas of multi-element association indicate that the region north of Qiucun has an important potential as a preferred target area for gold prospecting in the Dehua ore-field.

Constraints on the genesis of the Jiande polymetallic copper deposit in South China using fluid inclusion and O-H-Pb isotopes

The Jiande copper deposit is located in the Qin-Hang metallogenic belt, South China. The deposit is dominated by “stratiform-like” ores, which are hosted in the dolomite of the Upper Carboniferous Huanglong Formation. These ore bodies were previously proposed to be Carboniferous sedimentary exhalative (Sedex) style mineralization, but they also appear to be related to the Late Mesozoic granodiorite porphyry at Jiande. Three stages of mineralization can be observed. The prograde skarn minerals garnet and diopside were formed in the pre-ore stage. The “stratiform-like” ores, with minor quartz-polymetallic veins, were formed in the main mineralization stage. The post-ore stage is characterized by quartz-calcite ± pyrite veins. Fluid inclusions in quartz from the pre-ore skarn, the main stage of mineralization, and post-ore quartz–calcite ± pyrite veins were studied. Fluid inclusion petrography shows that two-phase liquid-rich (Type I), two-phase vapor-rich (Type II), and halite-bearing (Type III) fluid inclusions can be identified in the studied hydrothermal quartz samples. Primary Type II and Type III fluid inclusions only occur in quartz from the the main stage, whereas Type I fluid inclusions are present in all three stages of hydrothermal quartz.Type I fluid inclusions in pre-ore stage have homogenization temperatures of 290-368°C and salinities of 2.6-8.8 wt.% NaCl equiv. Type II and coexisting Type III fluid inclusions in the main stage share similar homogenization temperatures of 293 to 334 °C and 290 to 326 °C,but have two contrasting salinity ranges of 1.2 to 2.2 wt.% and 31.87 to 38.16 wt.% NaCl equiv, respectively. The coexistence of Type II and Type III fluid inclusions and their similar homogenization temperatures but contrasting salinities suggest that fluid boiling processes occurred. Type I fluid inclusions in the post-ore quartz–calcite veins have homogenization temperatures of 202-278 °C and salinities of 0.2-6.5 wt.% NaCl equiv. The hydrogen and oxygen isotopes (δD ranges from -78 ‰ to -61 ‰, δ18OH2O calculated from quartz are from 8.1 ‰ to 10.6 ‰) of fluid inclusions in quartz imply that ore fluids were principally derived from magmatic water. The lead isotopes of sulfide from the ores are close to the orogenic Pb evolution curve and are also similar to those of the Jiande Jurassic igneous rocks, suggesting that the metals were sourced mostly from the Jurassic igneous rocks. The skarn alteration, inferred boiling fluid inclusion assemblages, stable isotopic features of magmatic fluids, and metal source imply that the main stages of mineralization in the Jiande polymetallic copper deposit is of skarn-type, related to Jurassic granodiorites.

Fluid Inclusions and Isotopes Constraining the Ore Genesis of the Neoproterozoic Jinshan Orogenic Gold Deposit, South China

The Jinshan gold deposit is located in the famous Dexing copper-gold polymetallic district in eastern China. This polymetallic district consists of the Neoproterozoic Jinshan gold deposit (180 tons of Au), the Middle Jurassic Dexing porphyry Cu-Au-Mo deposits (6 Mt of Cu and 138 tons of Au) and the Middle Jurassic Yinshan Cu-Au-PbZn-Ag deposit (1.0 Mt of Cu and 107 tons of Au). Ore genesis of the Jinshan gold deposit is hotly debated. Some researchers proposed that it was a typical Neoproterozoic orogenic gold deposit (Li et al., 2010), but others pointed out that it belonged to Jurassic Dexing porphyryepithermal ore system (Mao et al., 2011).