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The Angouran deposit is the second-largest Zn–Pb deposit in Iran with 4.7 Mt sulfide ore (27.7% Zn, 2.4% Pb, and 110 g/t Ag) and 14.6 Mt nonsulfide ore (28.1% Zn, 4.4% Pb). Various models have been proposed to explain the genesis of sulfide ore in this deposit. Moreover, the mineralization type of its primary sulfide ores remains controversial. The major and trace element concentrations and sulfur isotopic composition of the two stages of sphalerite have been analyzed to constrain mineralization conditions and the genesis. The Angouran deposit, which contains discordant orebodies, is hosted in a Neoproterozoic/Cambrian schist-marble sequence. Two stages of sphalerite have been distinguished: early-stage (S1) red-brown sphalerite and late-stage (S2) honey-yellow sphalerite. Our result shows that, relative to the S2 sphalerite, the S1 sphalerite has higher contents of Fe, Mn, Co, Cu, Ag, Sn, Ga, Sb and In, but lower contents of As and Tl. Time-resolved depth profiles in these sphalerites determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses indicate that Fe, Cd, Co, Hg, Mn, Ge, and In are mainly present in solid solution and that Ag, Cu, Pb, As, Ni, Ga, Tl, Sb, and Sn are present in both solid solution and mineral inclusions. Correlation analyses reveal the occurrence of direct substitution mechanisms, such as Zn2+ ↔ (Fe2+, Cd2+) and 2Zn2+ ↔ Ge4++□ (vacancy) as well as coupled substitutions, such as 2Zn2+ ↔ Cu+ + Ga3+, 2Zn2+ ↔ (Cu+, Ag+) + Sb3+, 3Zn2+ ↔ Pb2+ + Tl+ + As3+, 4Zn2+ ↔ Pb2+ + 2As3++□(vacancy) or (Zn2+, Pb2+) ↔ Tl+ + As3+, and 4Zn2+ ↔ Cu+ + (Ga3+, In3+) + Sn4++□(vacancy). Geothermometer studies suggest that sphalerite in the Angouran deposit precipitated from a low-temperature (

The investigation of epigenetic carbonate-hosted Pb-Zn deposits from China and Europe in the Eastern and Western orogens of the Tethyan Domain, have provided a new perspective on the range of processes operating in this deposit class globally. However, improved metallogenic models require new constraints on the timing of mineralization throughout the Domain. To address this need, we applied Re-Os pyrite dating to the world class Irankuh Zn-Pb deposit, Iran. The Irankah deposit is located in the thrust belt of the Malayer-Esfahan Pb-Zn Metallogenic Belt (MEMB) in the Zagros Orogen, Iran. Mineralization is hosted by the Goushfil Main Fault and adjacent dolomitized limestones. The hydrothermal mineral assemblage comprises sphalerite, galena, pyrite, minor chalcopyrite and sulfosalt minerals, together with dolomite, barite and abundant quartz. Pyrite associated with main-stage sphalerite mineralization has low concentrations of 3 to 37 ng/g Re and 6 to 49 pg/g Os that are typical of low-level highly radiogenic (LLHR) sulfides. Nonetheless, vein and replacement pyrites from the Goushfil orebody yielded a 5-point isochron age of 66.5 ± 1.6 Ma that is interpreted as the main Zn-Pb mineralization age. The new mineralization age confirms an epigenetic origin for the Irankuh Zn-Pb deposit and supports an early onset for compressional deformation in the Zagros Orogen. The geochronological data support textural evidence that mineralization in veins occurred during regional compression in an active tectonic environment. Therefore the possibility that magmatic fluids and/or heat contributed to the mineralizing system should be incorporated into regional exploration models. Further work is required to test the extent to which epigenetic carbonate-hosted Pb-Zn deposits in the thrust and fold belt settings of the Central and Eastern Tethys differ from those in the Western Tethys and classic Mississippi Valley Type ore deposits.

Hydrous and anhydrous isothermal experiments on n-pentane and n-octadecane were conducted at 300–375℃ for durations up to 1094 h to evaluate the cracking and hydrolysis of hydrocarbons, using fused silica capillary capsules as micro-reactors. The chemical compositions of the gaseous products during cracking of n-octadecane at 350 and 375℃ were methane, ethane, propane, and n-butane. The aqueous product in the hydrolysis of n-pentane and n-octadecane at 300–375℃ was alcohol. Alkenes and hydrogen were not detected throughout all the isothermal experiments. Results showed that the gaseous yields were characterized by higher contents of wet gas than those in natural gas accumulations. Mechanisms regulating the enrichment of methane in reservoirs should be further studied. The hydrolysis and oxidation of hydrocarbon were relatively limited in the absence of iron-bearing mineral buffers, suggesting that hydrocarbons might be more stable in iron-poor reservoirs (e.g. carbonate and quartz arenite) than in iron-bearing-mineral-rich ones (e.g. mudstone and arkose) under deep burial conditions. The absence of hydrogen was ascribed to its high diffusion rate in fused silica than in gold tube; any hydrogen produced in the reaction tends to diffuse out of the fused silica capsule with no or limited hydrogen accumulation, similar to those in geological environment. The diffusion of hydrogen should be considered during calculating the volume and pressure changes in the thermal cracking of oil to gas in reservoirs, because the loss of hydrogen would result in a decrease in the conversion rate of oil to gas.

Fault zones control the locations of many ore deposits, but the ore-forming processes in such fault zones are poorly understood. We have studied the deformation and ore textures associated with fault zones that controlled the lead–zinc mineralization of the Dongmozhazhua deposit, central Tibet, ∼100 km southwest of Yushu City. Geological mapping shows that the structural framework of the Dongmozhazhua area is defined by NW–SE-trending reverse faults and superposed folds that indicate at least two stages of deformation. The first stage is characterized by tight nearly E–W-striking folds that formed during the closure of the Jinshajiang Paleo-Tethyan Ocean in the Triassic. The second stage of deformation produced NW–SE-trending reverse faults and related structures of the Fenghuoshan–Nangqian fold-and-thrust belt associated with India–Asia collision in the late Eocene to Oligocene. Scanline surveys along the ore-controlling fault zones show an internal structure that comprises a damage zone, a breccia zone with clasts that have become rounded, and a breccia zone with lenticular clasts, and this complex architecture was formed during at least two compressional substages of deformation. The Pb–Zn mineralization in the Dongmozhazhua area occurs exclusively close to NW–SE-trending reverse fault zones. Microtextural observations reveal that mineralization occurred as veinlets and disseminated blebs in limestone clasts, and as continuous bands and cements in fractured rocks. Cataclastic sulfide grains also can be seen in the matrix of some fault zones. The types of mineralization differ with structural position. The fillings of the ore-bearing veinlets typify the products of hydraulic fracture and both types of mineralization took place concurrently with regional contraction. We consider, therefore, that the ore-bearing fluids in the Dongmozhazhua deposit were concentrated in fault zones during regional compression and that the ore minerals were precipitated during hydraulic fracturing of host rocks. Subsequent fault activity pulverized some pre-existing sulfide material into cataclastic grains in the matrix of a tectonic breccia that developed in the same faults.

The newly discovered Chaqupacha Mississippi Valley-type (MVT) Pb–Zn deposit in central Tibet has been found to be helpful for understanding MVT ore formation relative to tectonic evolution of a foreland fold and thrust belt. The deposit lies in the Tuotuohe area of the western Fenghuo Shan-Nangqian fold and thrust belt of the India–Asia continental collision zone. It contains NNW-striking and folded Late Permian strata including an upper clastic unit and an underlying limestone unit. The strata overlie late Oligocene clastic rocks through a south-dipping reverse fault that is associated with regional northward thrusting during the Paleogene. The Late Permian and late Oligocene strata are unconformably overlain by flat-lying early Miocene marl and mudstone of the Wudaoliang Formation. Lead and zinc ores are mainly hosted by pre-ore dissolution and collapse breccias in the Late Permian limestone. The style of mineralization is epigenetic, as shown by replacement of the pre-ore dissolution breccia matrix and open-space-fill by galena, sphalerite, calcite, and minor barite and pyrite. δ34S values of the main sulfide galena range from − 27.5‰ to + 12.6‰. These features, together with the lack of magmatic activity during the mineralization, suggest that Chaqupacha is an MVT deposit. Subordinate mineralization is also present in the early Miocene Wudaoliang Formation marl and the paleokarst breccia which contains matrix compositionally equivalent to strata of the Wudaoliang Formation. The mineralization shares similar mineral associations and textures with the pre-ore dissolution breccia-hosted mineralization. Thus, the Pb and Zn mineralization in the entire deposit probably resulted from the same mineralizing event, which is younger than the youngest ore-hosting rocks (i.e., the early Miocene Wudaoliang Formation). Considering that thrusting in the Tuotuohe area had ceased prior to deposition of the Wudaoliang Formation host rocks, the mineralization at Chaqupacha post-dated the regional deformation. The Chaqupacha deposit thus provides a good example of MVT mineralization in a foreland fold and thrust belt that post-dates regional thrusting.

A significant belt of carbonate-hosted Pb–Zn mineralization occurs in the Himalayan–Zagros collisional orogenic system. Three differing types of these Pb–Zn deposits within this belt have been identified based on variations in gangue mineral assemblages, leading to the classification of carbonate-, quartz- and fluorite-rich classes of Pb–Zn deposits. The third Pb–Zn mineralization (fluorite-rich) type is common in this orogenic system, but little research has been undertaken on it. Here, we focus on the Mohailaheng deposit, a large-sized fluorite-rich carbonate-hosted Pb–Zn deposit (> 100 Mt Pb + Zn ores with average grade of 2.18%–4.23%); the deposit is located in the Sanjiang Cenozoic thrust-fold belt, an important part of the Himalayan–Zagros collisional orogenic system and an area that formed during the early Tertiary India–Eurasia collision. The main orebodies in this deposit are stratabound and are hosted by Carboniferous limestones that are located along secondary faults associated with a regional thrust fault. The main assemblage is a sphalerite + galena + pyrite sulfide assemblage associated with a calcite + fluorite + barite + quartz + dolomite gangue assemblage. Detailed field and experimental work indicates that the deposit formed during three distinct phases of hydrothermal activity. Studies on fluid inclusion and stable isotopes of gangue minerals indicate that two dominant distinct fluids involving the deposit formation. They include (1) a low-temperature (130–140 °C), high-salinity (23–24 wt.% NaCl equivalent) basinal brine containing Na + –K + –Mg 2 + –Ca 2 + –Cl − ions and abnormally high SO 4 2 − concentrations, which probably derived from Tertiary basins in the regional district, and (2) a low- to moderate-temperature (170–180 °C) and moderate- to high-salinity (19–20 wt.% NaCl equivalent) metamorphic fluid containing Na + –K + –Mg 2 + –Cl – –SO 4 2 − ions and abnormally high F − and organic matter concentrations, that probably formed during regional metamorphism. Some evaporated seawaters and meteoric fluids were also identified in mixtures with these two dominant fluids. The Pb–Zn mineralization at Mohailaheng formed during three distinct stages, consistent with the regional tectonic history. The first stage involved the formation of favorable lithological and structural traps at Mohailaheng during regional thrusting, leading to the migration of compressed metamorphic waters at depth along a detachment zone, sequestering metals from sediments within the region. Basinal brines at the surface also began to infiltrate down along the secondary faults, dissolving gypsum from the underlying sediments. The second stage was associated with the cessation of thrusting and the onset of strike-slip movements along these thrust faults. Metamorphic fluids containing high concentrations of halogen ions, organic gases, and metals ascended into the structural traps at Mohailaheng along the reactivated thrust faults, causing fluorite, calcite, and some sulfide precipitation. Then, basinal brines rich in SO 4 2 − quickly descended into the structural traps along the reactivated faults, causing reduction of SO 4 2 − by organic matter, and producing significant amounts of H 2 S. The reduced sulfur then reacted with the metals in the fluids, causing significant sulfide precipitation. The third stage was associated with metal-depleted fluids, which only resulted in the precipitation of calcite from the diluted basinal brines. Combining these findings with research results on other fluorite-rich carbonate-hosted Pb–Zn deposits in the Himalayan–Zagros orogenic system suggests that this type of carbonate-hosted Pb–Zn deposits can also be classified as Mississippi Valley-type (MVT) deposits, and that the origin of the fluorite in these deposits may be related to multiple hydrothermal fluids involved in the mineralization evolution.

The Dongmozhazhua deposit, the largest Pb–Zn deposit in south Qinghai, China, is stratabound, carbonatehosted and associated with epigenetic dolomitization and silicification of Lower–Middle Permian—Upper Triassic limestones in the hanging walls of a Cenozoic thrust fault system. The mineralization is localized in a Cenozoic thrust-folded belt along the northeastern edge of the Tibetan plateau, which was formed due to the India–Asia plate collision during the early Tertiary. The deposit comprises 16 orebodies with variable thicknesses (1.5–26.3 m) and lengths (160–1820 m). The ores occur as dissemination, vein, and breccia cement. The main sulfide assemblage is sphalerite + galena + pyrite + marcasite ± chalcopyrite ± tetrahedrite, and gangue minerals consist mainly of calcite, dolomite, barite, and quartz. Samples of pre- to post-ore stages calcite yielded d13C and d18O values that are, respectively, similar to and lower than those yielded by the host limestones, suggesting that the calcite formed from fluids derived from carbonate dissolution. Fluid inclusions in calcite and sphalerite in the polymetallic sulfidization stage mostly comprise liquid and gas phases at room temperature, with moderate homogenization temperatures (100–140°C) and high salinities (21–28 wt% NaCl eq.). Micro-thermometric fluid inclusion data point to polysaline brines as ore-forming fluids. The dD and d18O values of ore fluids, cation compositions of fluid inclusions, and geological information suggest two main possible fluid sources, namely basinal brines and evaporated seawater. The fluid inclusion data and regional geology suggest that basinal brines derived from Tertiary basins located southeast of the Dongmozhazhua deposit migrated along deep detachment zones of the regional thrust system, leached substantial base metals from country rocks, and finally ascended along thrust faults at Dongmozhazhua. There, the base-metal-rich basinal brines mixed with bacterially-reduced H2S-bearing fluids derived from evaporated seawater preserved in the Permo–Triassic carbonate strata. The mixing of the two fluids resulted in Pb–Zn mineralization. The Dongmozhazhua Pb–Zn deposit has many characteristics that are similar to MVT Pb–Zn deposits worldwide.

Cenozoic economic Zn–Pb–Cu–Ag ore deposits occur in the Lanping foreland fold belt (Lanping basin) of the Eastern Indo-Asian collision zone (EIACZ), eastern margin of the Tibetan plateau. They are sediment-hosted and controlled by two Cenozoic thrust–nappe systems developed in the western and eastern segments of the Tertiary basin, respectively, where thrusting was towards the centre of the basin in an approximately E–W direction and juxtaposes Triassic–Cretaceous over Tertiary strata. In the western system, Cu deposits occur as veins in the root zone, hosted by ~ NS-striking faults in Jurassic intense folds. Zn deposits occur in its front zone, controlled by second-order faults of major thrust faults and thrust-related strike-slip faults. In the eastern system, Zn–Pb–Cu–Ag deposits are located in the front zone, controlled by an E-dipping thrust fault and its second-order faults. The giant Jinding Zn–Pb deposit is controlled by a trap structure related to regional thrusting. Homogenization temperatures of fluid inclusions from these deposits are predominately δ 34 S CDT values ranging from − 30.4‰ to 11.2‰. H–O isotopes of fluid inclusions are similar to those of basinal brines, and C–O isotopes of hydrothermal carbonate minerals are partly close to those of carbonates and sedimentary organisms. These data suggest that the ore-forming fluids and materials mainly derive from the fluids and various rocks of the basin, respectively. The sediment-hosted Zn–Pb–Cu–Ag deposits in the Lanping foreland fold belt share some similarities with MVT-, SST-, SSC-, and SEDEX-type deposits in that there is a lack of any igneous affinity and instead must relate to activities of basinal fluids. The deposits show, however, a set of unique features: (1) they were formed in a strongly deformed foreland basin within a continent collision orogen and (2) closely related to regional thrust–nappe structure; (3) they are fault-controlled, commonly without strong selection for type of host rocks; and (4) contain a variety of metals including Zn, Pb, Cu, Ag, and minor Sr, Co, etc. It is suggested that the Zn–Pb–Cu–Ag deposits controlled by the thrust systems in the Lanping foreland belt are a new sub-type within the family of sediment-hosted base metal deposits.