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The Bangbu gold deposit is a large orogenic gold deposit in Tibet formed during the Alpine-Himalayan collision. Ore bodies (auriferous quartz veins) are controlled by the E-W-trending Qusong-Cuogu-Zhemulang brittle-ductile shear zone. Quartz veins at the deposit can be divided into three types: pre-metallogenic hook-like quartz veins, metallogenic auriferous quartz veins, and post-metallogenic N-S quartz veins. Four stages of mineralization in the auriferous quartz veins have been identified: (1) Stage S1 quartz+coarse-grained sulfides, (2) Stage S2 gold+fine-grained sulfides, (3) Stage S3 quartz+carbonates, and (4) Stage S4 quartz+ greigite. Fluid inclusions indicate the ore-forming fluid was CO2-N2-CH4 rich with homogenization temperatures of 170–261°C, salinities 4.34–7.45 wt% NaCl equivalent. δ18Ofluid (3.98‰–7.18‰) and low δDV-SMOV (–90‰ to –44‰) for auriferous quartz veins suggest ore-forming fluids were mainly metamorphic in origin, with some addition of organic matter. Quartz vein pyrite has δ34SV-CDT values of 1.2‰–3.6‰ (an average of 2.2‰), whereas pyrite from phyllite has δ34SV-CDT 5.7‰–9.9‰ (an average of 7.4‰). Quartz vein pyrites yield 206Pb/204Pb ratios of 18.662–18.764, 207Pb/204Pb 15.650–15.683, and 208Pb/204Pb 38.901–39.079. These isotopic data indicate Bangbu ore-forming materials were probably derived from the Langjiexue accretionary wedge. 40Ar/39Ar ages for sericite from auriferous sulfide-quartz veins yield a plateau age of 49.52 ± 0.52 Ma, an isochron age of 50.3 ± 0.31 Ma, suggesting that auriferous veins were formed during the main collisional period of the Tibet-Himalayan orogen (∼65–41 Ma).

Lithium separation technique for three reference materials has been established together with precise determination of lithium isotope using a Neptune multi collector-inductively coupled plasma mass spectrometry (MC-ICP-MS). The solutions of lithium element standard reference materials, potassium, calcium, sodium, magnesium and iron single element, were used to evaluate analytical methods applied. Three separate stages of ion-exchange chromatography were carried out using organic cation-exchange resin (AG 50W-X8). Lithium was enriched for the three stages using different eluants, which are 2.8 M HCl, 0.15 M HCl and 0.5 M HCl in 30% ethanol, respectively. The columns for the first and second stages are made of polypropylene, and those for the third stage are made of quartz. Total reagent volume for the entire chemical process was 35 mL for three reference materials. The recovery yielded for the three stages is 98.9-101.2% with an average of 100.0%, 97.6-101.9% with an average of 99.9%, and 99.8-103.3% with an average of 100.6%, respectively. The precision of this technique is conservatively estimated to be ±0.72-1.04‰ (2σ population), which is similar to the precision obtained by different authors in different laboratories with MC-ICP-MS. The δ7 Li values ( 7 Li/ 6 Li relative to the IRMM-016 standard) determined for andesite (AGV-2) and basalt (BHVO-2) are 5.68‰ (n=18), 4.33‰ (n=18), respectively. The δ7 Li value ( 7Li/6Li relative to the L-SVEC standard) determined for IRMM-016 is -0.01‰ (n=15). All these analytical results are in good agreement with those previously reported. In addition, the results for the same kinds of samples analyzed at the MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, are consistent with those obtained at the Plasma Laboratory, University of Maryland, within analytical uncertainty. According to these experiment results, it is concluded that this proposed procedure is a suitable method for determining the lithium isotopic composition of natural samples.

The middle-lower Yangtze area underwent a series of complex tectonic evolution, such as Hercynian extensional rifting, Indosinian foreland basining, and Yanshanian transpression-transtension, resulting in a large distinctive Cu-Fe-Au metallogenic belt. In the tectonic evolution, large-scale migration and convergence of fluids toward foreland basins induced during the collisional orogeny of the Yangtze and North China continental blocks were of vital importance for the formation of the metallogenic belt. Through geological surveys of the middle-lower Yangtze area, three lines of evidence of large-scale fluid migration are proposed: (1) The extensive dolomitic and silicic alteration penetrating Cambrian-Triassic strata generally occurs in a region sandwiched between the metallogenic belt along the Yangtze River and the Dabie orogenic belt, and in the alteration domain alternately strong and weak alteration zones extend in a NW direction and are controlled by the fault system of the Dabie orogenic belt; it might record the locus of the activities of long-distance migrating fluids. (2) The textures and structures of very thick Middle-Lower Triassic anhydrock sequences in restricted basins along the river reveal the important contribution of the convergence of regional hot brine in restricted basins and the chemical deposition or their formation. (3) Early-Middle Triassic syndepositional iron carbonate sequences and Fe-Cu-Pb-Zn massive sulfide deposits alternate with anhydrock sequences or are separated from the latter, but all of them occur in the same stratigraphic horizon and are intimately associated with each other, being the product of syndeposition of high-salinity hot brine. According to the geological surveys, combined with previous data, the authors propose a conceptual model of fluid migration-convergence and mineralization during the Dabie collisional orogeny.

The Tongling area is one of the 7 ore-cluster areas in the Middle-Lower Yangtze metallogenic belt, East China, and has tectonically undergone a long-term geologic history from the late Paleozoic continental rifting, through the Middle Triassic continent-continent collision to the Jurassic-Cretaceous intracontinental tectono-magmatic activation. The Carboniferous sedimentary-exhalative processes in the area produced widespread massive sulfides with ages of 303–321 Ma, which partly formed massive pyrite-Cu deposits, but mostly provided significant sulfur and metals to the skarn Cu mineralization associated with the Yanshanian felsic intrusions. To understand the Carboniferous submarine hydrothermal system, an area of about 1046 km2 was chosen to carry out the geological fluid mapping. Associated with massive sulfide formation, footwall sequences 948 m to 1146 m thick, composed of the Lower Silurian-Upper Devonian sandstone, siltstone and thin-layered shale, were widely altered. This hydrothermal alteration is interpreted to reflect large-scale hydrothermal fluid flow associated with the late Paleozoic crustal rifting and subsidence. Three hydrothermal alteration types, i.e., deep-level semiconformable silicification (S1), fracture-controlled quartz-sericite-pyrite alteration (S2–3), and upper-level sub-discordant quartz-sericite-chlorite alteration (D3), were developed to form distinct zones in the mapped area. About 50-m thick semiconformable silicification zones are located at ∼1-km depth below massive sulfides and developed between an impermeable shale caprock (S1) and the underlying Ordovician unaltered limestone. Comparisons with modern geothermal systems suggest that the alteration zones record a sub-seafloor aquifer with the most productive hydrothermal fluid flow. Fracture-controlled quartz-sericite-pyrite alteration formed transgressive zones, which downward crosscut the semiconformable alteration zones, and upwards grade into sub-discordant alteration zones that enveloped no economic stringer-stockwork zones beneath massive sulfides. This transgressive zone likely marks an upflow path of high-flux fluids from the hydrothermal aquifer. Lateral zonation of the sub-discordant alteration zones and their relationship to overlying massive sulfide lenses suggest lateral flows and diffusive discharging of the hydrothermal fluids in a permeable sandstone sequence. Three large-sized, 14 middle-small massive sulfide deposits, and 40 massive sulfide sites have been mapped in detail. They show regional strata-bound characters and two major styles, i.e., the layered sheet plus strata-bound stringer-style and the mound-style. Associated exhalite and chemical sedimentary rock suites include (1) anhydrite-barite, (2) jasper-chert, (3) Mg-rich mudstone-pyrite shale, (4) barite lens, (5) siderite-Fe-bearing dolomite, and (6) Mn-rich shale-mudstone, which usually comprise three sulfide-exhalite cyclic units in the area. The spatial distribution of these alteration zones (minerals) and associated massive sulfides and exhalites, and regional variation in δ34S of hydrothermal pyrite and in δ18O-δ34C of hanging wall carbonates, suggest three WNW-extending domains of fluid flow, controlled by the basement faults and syn-depositional faults. Each fluid domain appears to have at least two upflow zones, with estimated even spacing of about 5–8 km in the mapped area. The repeated appearance of sulfide-sulfate or sulfide-carbonate rhythmic units in the area suggests episodically venting of fluids through the upflow conduits by breaking the overlying seals of the hydrothermal aquifer.

Numerical simulation of fluid migration during the ore-forming process of the Carboniferous exhalation-sedimentary (Sedex) massive sulfide deposits in the Tongling district shows that fluid and thermal activities in lying-wall rocks were limited to a small area around the main draining passage, which led to weak mineralization and alteration in the lying-wall rock. Temperature and fluid fields indicate that mineralization and alteration in the lying-wall rock of the Sedex-type deposits are usually weaker than those of volcano-hosted massive sulfide deposits. Fluid migration involves the following processes: seawater penetrating and leaching the lying-wall rocks, then mixing with ascending hydrothermal fluids in the main draining passage, and finally jetting into seafloor. Although fluid activity-influenced area is rather small, the content of metals leached out from the lying-wall rocks is high enough to form large-scale ore deposits. Tensional contemporaneous faults accompanied with strong heat flows controlled the formation and distribution of Sedex deposits. The tensional tectonic regime on the northern margin of the Yangtze block during the Hercynian provided Sedex deposits with a prerequisite geodynamic condition.

The Shangmanggang red clay-type gold deposit was discovered in West Yunnan in the early 1990s, which is strictly controlled by the Shangmanggang fault, belonging to a new type of gold deposits. Its red clay profile, about 20 m thick, is divided into six zones: topsoil zone, slope-wash zone, travertine zone, eluvium zone, saprolite zone, and unweathered bedrocks. The degree of laterization is relatively high in the eluvium zone where gold is very rich. Ore minerals mainly consist of quartz, goethite, and clay minerals. Sand and silt fractions are mainly composed of quartz and goethite with minor feldspar; clay fractions comprise illite, kaolinite, quartz, a small quantity of goethite, feldspar, and hydrargillite. The variation of gold content in the red clays is similar to that of sand fractions. Gold is probably closely associated with iron nodules developed in the red clays. At the same time, gold is well correlated with clay minerals and Fe, Mn oxides. Gold exists mostly in the form of dissociated gold and microfine gold, which is adsorbed on the surface or in the cracks of quartz, clay minerals, and goethite. Geochemistry characteristics of the major elements, trace elements, and REEs in the red clays of the Shangmanggang red clay-type gold deposit in West Yunnan were studied in detail. The results show that Al2O3, Fe2O3, and K2O were migrated and precipitated together in the red clay profile, but the case is not true for SiO2. As a whole, SiO2 is high in content, desilication is incomplete, and the degree of laterization is low in the red clays, except for a high degree of laterization in the eluvium zone. In contrast with the sedimentary rocks and altered rocks, the red clays come from the Mengga Formation mudstone with laterization. Au, Hg, As, Sb, Cu, Pb, Zn, and Mo are coextensive trace elements in the red clay profile and are significantly enriched in the eluvium zone where laterization is relatively complete. The crust-normalized large-ion-lithophile element patterns in the red clays are similar to those of both altered rocks and the Mengga Formation. The chondrite-normalized REEs patterns in the red clays are also similar to those of both altered rocks and the Mengga Formation. The LREEs are enriched, and gold is concentrated in the location where REE fractionation is strong. Our work reveals that gold comes mainly from the altered rocks, and the red clays are mainly derived from the Mengga Formation and altered rocks.