Hydrothermal Vein Deposits Research Articles

Distribution of indium and gallium in sphalerite from skarn and hydrothermal vein deposits in the Hwanggangri mineralized district, South Korea

The geochemistry of sphalerite from seven metallic ore deposits in the Hwanggangri mineralized district in South Korea was studied, with a special focus on the concentrations of In and Ga. The chemical compositions were analyzed using laser ablation-inductively coupled plasma-mass spectroscopy and compared based on deposit type (skarn and hydrothermal vein) and ore species (W, Mo, Zn–Pb, and W–Zn–Pb). In hydrothermal W and W–Zn–Pb vein deposits, In was highly concentrated, with averages of up to 696 ppm, whereas Mo and Zn–Pb skarn deposits produced low concentrations below 43 ppm on average. In contrast, the Ga concentrations were quite low throughout the deposits and did not exceed 16 ppm on average. Indium showed a clear positive correlation with Cu and was strongly associated with the development of chalcopyrite-disease, with Ag and Sn potentially playing subordinate roles in the substitution. The binary correlations between trace elements suggested that principal coupled substitutions, such as 3Zn2+ ↔ 2(Cu, Ag)+ + Sn4+ and 2Zn2+ ↔ Cu+ + In3+, prevailed in In-bearing sphalerite. A discernable weak positive correlation is observed between In and Cd, mostly in the W-bearing deposits, implying that Cd, a common constituent in sphalerite, could be used as an exploration proxy in some cases. The general tendency of high In and low Ga concentrations in the sphalerites from the Hwanggangri mineralized district indicates relatively high temperature of mineralizing fluids, generally above 250 °C, which favored the prevalence of In-chloride complexes over Ga-hydroxide complexes. Additionally, the In enrichment in the hydrothermal vein ores rather than the skarn ores emphasizes the importance of the direct contribution of magmatic fluids to ore mineralization under high temperature conditions with little influence from the host rock.

Indosinian W–Sn mineralization in the Dupangling area, Western Nanling: Cassiterite U–Pb dating and trace element data for the Maoershi Sn polymetallic deposit

Nanling is located in central South China and contains the most important area of W–Sn polymetallic deposits worldwide. However, a lack of geochronological data hinders our understanding of the timing and mechanisms of W–Sn mineralization in the Dupangling area of western Nanling. The Maoershi Sn polymetallic deposit is located in the western body of Dupangling complex pluton, and is a significant hydrothermal vein deposit. Cassiterite U–Pb dating shows that the Maoershi Sn mineralization occurred during the Late Triassic (206.2 ± 2.6 Ma). This age is different from the age of granite in the western Dupangling pluton and similar to the age of the eastern Dupangling pluton. The cassiterite is enriched in Sc (4.5105–18.4049 ppm), V (37.2267–88.9671 ppm), Nb (62.0104–194.1846 ppm), Ta (11.1965–85.6881 ppm), Hf (22.0511–30.7650 ppm), U (2.8870–17.9187 ppm), Th (0.0005–0.0908 ppm), Ti (3873–6170 ppm), and other high-field-strength elements. Based on Nb/Ta and Y/Ho ratios, and the W–Fe discriminant diagram, Sn and the other mineralizing materials were mainly derived from hidden Indosinian granitic rocks. Tungsten–Sn mineralization in the Dupangling pluton exhibits a clear spatial–temporal relationship with Indosinian granitic magmatism, and occurred in an extensional setting after the continent–continent collision that marked the late Indosinian Orogeny.

Multistage fluorite mineralization in the southern Black Forest, Germany: evidence from rare earth element (REE) geochemistry

Abstract. The Black Forest hosts a wide range of hydrothermal mineralization, including fluorite–barite vein deposits. In a detailed investigation of the Finstergrund and Tannenboden deposits in the Wieden mining district (southern Black Forest), the diversity, geochemical evolution and relative chronology of multistage fluorite precipitation is tracked on the basis of rare earth element (REE) geochemistry, geologic field relationships and crystal zoning. Geochemical discrimination and mathematical λ coefficients suggest a total of seven fluorite REE groups, at least three distinguishable post-Variscan fluid mobilization events and independent formation histories for the deposits despite their spatial proximity. Fluorite vein mineralization at the Finstergrund deposit evolved over three fluid generations, was derived from gneissic source aquifers and comprises five distinct fluorite REE groups: the first fluid generation is characterized by fluorite precipitation above 200 ∘C (“group III”), below 200 ∘C (“group I”) and after fractional crystallization (“group IV”); the second generation comprises remobilized fluorite (“group II”); and the third generation revealed fluorite precipitation by meteoric water mixing (“group V”). Fluorite vein formation at the Tannenboden deposit is associated with two distinct fluorite REE patterns derived from the same fluid generation: fluorite precipitation above 200 ∘C (“group VII”) and after cooling below 200 ∘C (“group VI”). Its fluid source aquifer lithology best matches migmatites contrary to previous models that suggest either gneissic or granitic aquifer rocks for fluorite vein precipitation in the Black Forest. The decoupled formation history between the deposits is tectonically controlled as suggested by a new genetic model for the Wieden mining district. The model argues for a change in the local fluid percolation network and the termination of hydrothermal activity at the Tannenboden deposit after the first fluid mobilization event. The geochemical evolution of multistage fluorite mineralization, as exemplified by the Tannenboden and Finstergrund deposits in combination with other fluorite mineralizations in the Black Forest, provides unique insights into the lithospheric origin and precipitation behaviour of fluorite by various fluid–rock interaction processes occurring in large hydrothermal systems. The local diversity of REE patterns emphasizes the need for detailed investigations of individual hydrothermal vein deposits.

Genetic Environments at the Ssangjeon Tungsten-bearing Hydrothermal Vein Deposit

Genetic Environments at the Ssangjeon Tungsten-bearing Hydrothermal Vein Deposit

Au-Ag-bearing Ore Mineralization at the Geochang Hydrothermal Vein Deposit

Au-Ag-bearing Ore Mineralization at the Geochang Hydrothermal Vein Deposit

Antlers of European roe deer (Capreolus capreolus) as monitoring units to assess lead pollution in a floodplain contaminated by historical metal ore mining, processing, and smelting in the Harz Mountains, Germany

Lead concentrations in hard antlers of adult European roebucks (Capreolus capreolus) were analyzed to assess lead exposure of roe deer roaming the floodplain of the Innerste River, a river system contaminated due to historical metal ore mining, processing, and smelting in its upper reaches. Antler lead concentrations of roebucks culled in the period 1939–2018 within or close to the Innerste floodplain ranged between <0.17 mg Pb/kg (limit of detection) and 51.5 mg Pb/kg (air-dry weight). Median lead concentration in antlers of roebucks culled within the floodplain was 11.1 mg Pb/kg, compared to 2.3 mg Pb/kg in antlers of bucks culled in the floodplain vicinity (P < 0.01). Sampling year had no significant effect on antler lead concentrations (P = 0.748). Lead isotope ratios of antlers from the Innerste downstream area (206Pb/207Pb: 1.179–1.181; 208Pb/206Pb: 2.083–2.085) fell within the range of those reported for hydrothermal vein deposits from the upper catchment area of the Innerste River in the Harz Mountains. Our study demonstrates the long-lasting impact of the historical metal ore mining, processing, and smelting in the Harz Mountains on lead pollution in floodplains of rivers draining this area and the lead exposure of wild herbivores inhabiting the floodplains. Furthermore, it highlights the suitability of roe deer antlers for monitoring environmental lead levels and the usefulness of lead isotope signatures in antlers for source apportionment of lead pollution.

Basement aquifer evolution and the formation of unconformity-related hydrothermal vein deposits: LA-ICP-MS analyses of single fluid inclusions in fluorite from SW Germany

The main ore stage of three similar unconformity-related vein systems in the Schwarzwald, SW Germany spanning a period of activity of ~150 Ma, was investigated to understand the details of fluid penetration from overlying sediments/marine environment into the basement, their evolution as well as the processes involved in vein formation. To investigate temporal and spatial variations of the hydrothermal fluids responsible for mineralization, over 1650 fluid inclusions were analyzed by microthermometry. Of these, a total of 108 fluid inclusions (mainly in fluorite) were successfully analyzed by LA-ICP-MS. The fluid inclusions reveal a binary mixing trend between a CaCl2- and a NaCl-rich endmember. Independent of major element composition, the fluids are metal-bearing (e.g., up to ~100 mg/kg Ba, Pb, Zn, Ni and up to 10 mg/kg Ag), show high As (up to 1000 mg/kg) and low S (below the detection limit in most analyses). Over time, the mixed fluid shows a gradual decrease in CaCl2 and increase in NaCl with slightly decreasing total salinity.Based on earlier studies and geochemical arguments, the veins formed by anisothermal binary fluid mixing of two fluids, which both were originally derived from seawater and chemically modified through interaction with the basement and sedimentary rocks in different ways. This produced a gradual stratified basement fluid reservoir comprising a modified bittern/halite dissolution brine. The fluids involved in the vein formation are sourced from different depths of this modified bittern/halite dissolution basement brine reservoir: fluid A, a CaCl2-dominated, KCl-poor, deeper seated brine with a salinity of ~25 wt% CaCl2 + NaCl, and fluid B, an NaCl-dominated and KCl-richer brine situated at shallower depths in the crystalline basement with salinities of ~22 wt% NaCl+CaCl2. Based on the Na-Ca-K and NaK thermometers and on Rb/Cs systematics, fluid A records alteration of the Na-, K- and Ca-bearing feldspars of the host rocks; progressive alteration led to consumption of mainly Ca-rich plagioclase in contact with these basement brines. Accordingly, fluid B that subsequently entered the basement was only in equilibrium with alkali feldspars and clay minerals. This scenario produced a gradual change of fluid composition with depth that was pushed to greater depth over time.The source temperatures are estimated to ~250 °C while vein formation occurred at 100–170 °C, based on fluid inclusion homogenization temperatures. Thus, significant fluid cooling without abundant fluid mixing (and without major mineralization) must have occurred during fluid ascent (3–7 km, depending on the assumed geothermal gradient). Fluid mixing then resulted in the formation of the major gangue minerals fluorite, quartz, barite and calcite, while the locally confined sulfides must have formed due to an influx of sulfide into the binary mixed fluid. The process of fluid mixing is a rapid and turbulent process. This is recorded by a great diversity of fluid compositions (including ones close to the mixing endmembers) trapped within the same crystal. Compositional variations are even visible within individual fluid inclusion trails.

Alteration Mapping for Lead-Zinc-Barium Mineralization in Parts of the Southern Benue Trough, Nigeria, Using ASTER Multispectral Data

The lead-zinc-barium deposits of the southern Benue Trough, Nigeria belong to a suite of clastic dominated fracture filling hydrothermal vein deposits. The alteration types and spread are poorly known yet required to aid exploration. Band ratio composites (BRC), Principal Component Analysis (PCA), and Minimum Noise Fraction (MNF) were applied to a full scene Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery covering the study area. Spectral analysis of sulphide minerals known in the area led to the development of the (B1+B3)/2 ratio, which provided a highly effective sulphide discriminant. PCA and MNF bands with high eigenvectors in the absorption features of target minerals qualified as colour composite candidates for alteration mapping. This study demonstrated the effectiveness of combining the BRC, PCA and MNF techniques in the discrimination of ferric-ferrous/sulphide and silica alteration zones in the Southern Benue Trough.

Combining Ion Chromatography and Total Reflection X-ray Fluorescence for Detection of Major, Minor and Trace Elements in Quartz-Hosted Fluid Inclusions

The crush-leach technique is a frequently used method to determine the bulk composition of fluid inclusions trapped in a range of geological samples. We present a modified crush-leach technique combining ion chromatography (IC) and total reflection X-ray fluorescence spectroscopy (TXRF) which allows to determine a range of major, minor and trace elements out of one leachate. To date, trace element detection by means of TXRF is barely used in geosciences, although it combines the advantages of low to very low detection limits (µg/L to ng/L range), small sample amount needed (µL-range) and a fast and inexpensive analytical procedure. Previously described problems of adsorption of polyvalent cations at sample surfaces have been overcome by using acidified water as a leachate. Instead, it has been demonstrated that, for example, the syringe filter type used for IC measurements influences contamination and/or adsorption for a number of elements. The proposed method combination was evaluated for accuracy, reproducibility and system blanks and subsequently applied to quartz samples from hydrothermal vein deposits of the Schwarzwald ore district, SW Germany.

Geochemical characteristics of Late Carboniferous mineralization in the East Tianshan: A case study of the Meiling deposit in the Kalatage area

The Meiling deposit in the Kalatage area of the East Tianshan, which is the most recently identified Late Carboniferous hydrothermal vein deposit, is located in a series of basic-intermediate-acidic volcanic-pyroclastic rocks and contains ore bodies composed of single quartz-sulfide veins and quartz-sulfide vein groups in a stockwork/en-échelon arrangement with Cu as the primary ore-forming element and Zn, Au and Ag as secondary ore-forming elements. This study examines the geochemical characteristics of sub-volcanic rocks and analyses fluid inclusions and stable isotopes (H, O and S) to determine the metallogenic characteristics of the Meiling deposit and discusses the pattern and geological significance of the mineralization in the Kalatage area. The quartz porphyry, dacite porphyry and granite porphyry from the Meiling deposit, which are closely related to the mineralization, are calc-alkaline magmatic rocks that formed in an island arc setting. Most of the primary quartz fluid inclusions are liquid-rich two-phase FIs with homogenization temperatures mainly of 154–251 °C and salinities of 3.1–5.6% NaCl equivalent and the sphalerite fluid inclusions are liquid-rich two-phase FIs characterized by omogenization temperatures mainly of 156–263 °C and salinities of 2.4–5.3% NaCl equivalent, which are low temperature and low salinity. H and O isotope analysis show that in the polymetallic sulfide-quartz stage, the δD values ranged from −79.3‰ to −54.0‰, the δ18OH2O values ranged from −8.99‰ to −2.57‰, and the primary ore-forming fluids were mixtures of a dominant meteoric water phase with minor amounts of magmatic fluid. S isotope analysis shows that in the polymetallic sulfide-quartz stage, the δ34S values of the main sulfides were distributed between −1.6‰ and 5.2‰, similar to the range of a homogenous sulfur source. These results, together with the S-isotopic characteristics of the wall rocks from the Meiling deposit, demonstrate that the ore-forming metals might have originated from the volcanic-subvolcanic wall rocks. These results show that the metallogenic characteristics of the Meiling deposit are consistent with those of low temperature epithermal deposits and clearly demonstrate that the Meiling deposit is a low temperature epithermal deposit that formed in an island arc setting. The Kalatage area provides a natural laboratory for studying the characteristics of geological mineralization during the arc-basin system transformation process.

Ore Genesis of the Chuduoqu Pb-Zn-Cu Deposit in the Tuotuohe Area, Central Tibet: Evidence from Fluid Inclusions and C–H–O–S–Pb Isotopes Systematics

The Chuduoqu Pb-Zn-Cu deposit is located in the Tuotuohe area in the northern part of the Sanjiang Metallogenic Belt, central Tibet. The Pb-Zn-Cu ore bodies in this deposit are hosted mainly by Middle Jurassic Xiali Formation limestone and sandstone, and are structurally controlled by a series of NWW trending faults. In this paper, we present the results of fluid inclusions and isotope (C, H, O, S, and Pb) investigations of the Chuduoqu deposit. Four stages of hydrothermal ore mineralization are identified: quartz–specularite (stage I), quartz–barite–chalcopyrite (stage II), quartz–polymetallic sulfide (stage III), and quartz–carbonate (stage IV). Two types of fluid inclusions are identified in the Chuduoqu Pb-Zn-Cu deposit: liquid-rich and vapor-rich. The homogenization temperatures of fluid inclusions for stages I–IV are 318–370 °C, 250–308 °C, 230–294 °C, and 144–233 °C, respectively. Fluid salinities range from 2.07 wt. % to 11.81 wt. % NaCl equivalent. The microthermometric data indicate that the fluid mixing and cooling are two important mechanisms for ore precipitation. The H and O isotopic compositions of quartz indicate a primarily magmatic origin for the ore-forming fluids, with the proportion of meteoric water increasing over time. The C and O isotopic compositions of carbonate samples indicate that a large amount of magmatic water was still involved in the final stage of mineralization. The S and Pb isotopic compositions of sulfides, demonstrate that the ore minerals have a magmatic source. On a regional basis, the most likely source of the metallogenic material was regional potassium-enriched magmatic hydrothermal fluid. Specifically for the Chuduoqu Pb-Zn-Cu deposit, the magmatic activity of a syenite porphyry was the likely heat source, and this porphyry also provided the main metallogenic material for the deposit. Mineralization took place between 40 and 24 Ma. The Chuduoqu deposit is a mesothermal hydrothermal vein deposit and was formed in an extensional environment related to the late stage of intracontinental orogenesis resulting from India–Asia collision. The determination of the deposit type and genesis of Chuduoqu is important because it will inform and guide further exploration for hydrothermal-type Pb and Zn deposits in the Tuotuohe area and in the wider Sanjiang Metallogenic Belt.

Fluid Inclusions and H-O-C-S Isotopes of the Wushan Copper Polymetallic Deposit in the Suizao Area, Hubei Province: Implications for Ore Genesis

The Wushan copper polymetallic deposit is located in the Tongbai-Dabie orogenic belt in central China. Two small granitoid stocks (Donggushan and Xigushan) occur in the deposit, which is next to the largest Qijianfeng Granite Complex in the Suizao area. The mineralization of Wushan copper polymetallic deposit is mainly composed of ore-bearing quartz veins and quartz stockworks. Two hydrothermal stages are identified as the quartz-sulfide stage (early stage) and the barren quartz stage (late stage). A detailed petrographic study shows four types of fluid inclusions in quartz, including the aqueous fluid inclusions (L+V/V+L), the aqueous-carbonic fluid inclusions (L+V+CO2), the pure carbon dioxide fluid inclusions (pure CO2), and the daughter mineral-bearing multiphase fluid inclusions (S). The daughter mineral-bearing multiphase fluid inclusions (S) are further divided into three subclasses according to their different solid mineral assemblages, including (1) S1: L+V+Hal, (2) S2: L+V+CO2+S (chalcopyrite), and (3) S3: L+V+S (calcite, chalcopyrite, and hematite)±Hal. A laser Raman spectroscopic analysis shows that the main components of fluid inclusions are water and carbon dioxide. The solid minerals of the S-type fluid inclusions include halite, calcite, chalcopyrite, and hematite. The homogenization temperatures of fluid inclusions are 377 to 468°C for the early stage, with a salinity of 11.1 to 34.1 wt.% NaCl equivalent (11.1 to 17.4 wt.% NaCl equivalent and 28.4 to 34.1 wt.% NaCl equivalent, respectively) and an estimated pressure of 89 to 137 MPa. The homogenization temperatures of fluid inclusions in the late stage are 267 to 380°C with salinity of 7.0 to 12.1 wt.% NaCl equivalent and an estimated pressure of 46 to 115 MPa. Therefore, the temperature, salinity, and pressure of the fluid show a decreasing trend from the early to the late stage. In the early stage, the fluid is immiscible, which leads to the precipitation of sulfides. Pyrite shows a δ34S of approximately 0 (-1.8 to +3.4‰), and chalcopyrite also shows a similar δ34S of approximately 0 (+1.5 to +2.4‰), which indicates that the sulfur in the ore-forming fluid is mainly derived from deep-seated magma. Combined with C-H-O isotopic compositions, the initial ore-forming fluid is likely magmatic water, but with the addition of meteoric water in the late stage. By comparing with the typical characteristics of magmatic hydrothermal vein deposit and orogenic deposit related to shear zones, we suggest that the Wushan copper polymetallic deposit is most likely a magmatic hydrothermal vein deposit, which is of great significance for the further exploration work in the Wushan and surrounding areas. This new finding also fills the gap that no magmatic hydrothermal vein type Cu deposits have been found in the Suizao area or even in the Qinling-Dabie orogenic belt in central China.

FTIR microspectroscopy of carbonaceous matter in ~\u20093.5 Ga seafloor hydrothermal deposits in the North Pole area, Western Australia

Carbonaceous matter in ~ 3.5 Ga hydrothermal vein deposits from the Dresser Formation, Western Australia, was analyzed using Fourier transform infrared (FTIR) microspectroscopy. Based on the spectroscopy, the carbonaceous matter was mainly composed of disordered aromatic structures, with minor aliphatic C–H functional groups. Spatially resolved analysis supports that the aliphatic C–H signatures are derived from kerogenous macro-molecule and not from free bitumen or other artificial sources. The intensity ratios of the asymmetric aliphatic CH3 to the asymmetric aliphatic CH2 (R3/2 value) in the carbonaceous clots range from 0.22 to 0.51. Thermal alteration may increase or not change the R3/2 value of organic matter, as suggested by previous experiments, but it is unlikely to be the cause of the substantially lower R3/2 values when compared with those of primary organic matter. In particular, the low R3/2 values (< ~ 0.4) suggest that the carbonaceous matter mainly contains aliphatic C–H bonds derived from bacterial cells. The carbonaceous clots may have been possibly produced by abiotic reaction such as Fischer-Tropsch-type (FTT) synthesis. However, the organic matter source only produced by the FTT synthesis is inconsistent with the R3/2 values for the analyzed carbonaceous clots. The results obtained by combining these spectroscopic features of the carbonaceous clots together with the previously reported isotopic features may possibly suggest that both bacteria and archaea were colonized in the ~ 3.5 Ga Dresser hydrothermal system.

Factor analysis characterization of minor element contents in sulfides from Pb–Zn–Cu–Ag hydrothermal vein deposits in Portugal

We studied minor element contents in galena, sphalerite and chalcopyrite from Pb–Zn–Cu–Ag hydrothermal vein deposits in Portugal and applied factor analysis to describe the dispersion and modes of association of these elements in the host minerals. For this purpose, a large suite of minor elements was analyzed through electronic microprobe (EPMA-WDS) in the aforementioned minerals, and then the data were processed and compiled through the use of appropriate statistical software.Factor analysis (FA) was conducted in an adequate way as described in the paper, and then applied to the minor element data. This allowed us to distinguish between deposits, groups of deposits and deposit districts. Also clues about different mineral generations were obtained by this method, namely different generations of galena in some deposits, relating to earlier and later stages of crystal growth, which are often not microscopically identifiable. FA allowed us to characterize the deposit districts by principal factors describing the galenas, the sphalerites and the chalcopyrites, providing a new insight into the studied Portuguese deposits. Our study shows that factor analysis applied to minor elements in sulfides is a powerful tool in discriminating deposits and metallogenic regions.

Zeku County Longquna-Donggerina Gold Deposit Geologic Feature and Metallogenic Regularities

Longquna-Donggerina gold deposit of Kuze county in Qinghai province that has development value in the Langqin area in recent years,which is prospecting achievements by the sustained regional heavy mineral anomaly. By analysis on metallogenic geological setting and regional heavy mineral anomaly feature, combined with the ditailed mining area geological data , gold deposit occurs mainly sandstone and slate, and the degree of mineralization has positive correlation with magmatic activity and tectonization. Lonquna-Donggerina gold deposit had been preliminary identified that belongs to the low temperature hydrothermal fissure filling type vein deposit.

Mesozoic molybdenum deposits in the East Xingmeng orogenic belt, northeast China: characteristics and tectonic setting

Numerous molybdenum (Mo) ore deposits have been discovered in the East Xingmeng orogenic belt (East Central Asian orogenic belt), over the past 10 years, and this region is becoming one of the world's most important Mo production areas. It contains 6.18 Mt of proven Mo metal reserves, which accounts for 30% of the total proven Chinese Mo reserves. The ore district includes 37 deposits and 15 occurrences, with three major Mo ore types, that is porphyries, skarns, and hydrothermal veins. The latter can be subdivided into quartz- and volcanic hydrothermal-vein types. With the exception of the Ordovician Duobaoshan porphyry Cu–Mo deposit (477 Ma), all the East Xingmeng Mo deposits formed during the Mesozoic. Re–Os dating of molybdenite has documented three episodes of Mo mineralization: Early Triassic (248–242 Ma), Jurassic (178–146 Ma), and Early Cretaceous (142–131 Ma). Early Triassic Mo deposits are distributed along the northern margin fault of the North China Craton (NCC) and include porphyry and quartz vein types. They are characterized by the association of Mo + Cu. Jurassic Mo deposits are mainly distributed in the eastern area and include porphyry, quartz vein, and skarn types. They are typified by Mo alone and/or the association of Mo, Pb, and Zn. Cretaceous Mo deposits are distributed in all areas and include porphyry and volcanic hydrothermal vein types. Similar to the Jurassic ores, they are simple Mo or Mo + Pb + Zn deposits. Volcanic hydrothermal vein deposits are characterized by an association of molybdenum and uranium. The Triassic Mo deposits formed in a syn-collision setting between the Siberian and North China plates. The Jurassic Mo deposits formed in a compressional setting, which was probably triggered by the westward subduction of the palaeo-Pacific plate. The Early Cretaceous Mo deposits are linked to a tectonic regime of lithosphere thinning, which was caused by delamination of thickened lithosphere. However, the Mo deposits in the Erguna terrane of the northwest Xingmeng orogenic belt may be related to the evolution of the Okhotsk Ocean.

Chemical compositon of chlorite with special reference to the iron vs. manganese variation, from some hydrothermal vein deposits, Japan

Chemical compositon of chlorite with special reference to the iron vs. manganese variation, from some hydrothermal vein deposits, Japan

Metal deposits in the Da Hinggan Mountains, NE China: styles, characteristics, and exploration potential

The Da Hinggan Mountains mineral province (DHMP), northeastern China, is divided into three tectonic units and corresponding metallogenic belts. The tectonic units of the Da Hinggan Mountains are the Erguna fold zone on the northwest, the Hercynian fold zone on the north, and the Hercynian fold zone on the south. The corresponding metallogenic belts are the Erguna Cu-Pb-Zn-Ag-Mo-Au belt of the NW DHMP, the Cu-Pb-Zn-Mo-Fe-Au belt of the northern DHMP, and the Pb-Zn-Ag-Cu-Sn-Fe-Mo belt of the southern DHMP. Distinct ore bodies, mostly associated with Mesozoic granites and volcanics, comprise (1) hydrothermal vein deposits including Pb-Zn-Ag-(Cu) and W‐Sn-Cu, (2) exhalative (Pb-Zn-Ag, Cu) deposits, (3) porphyry (Cu, Au, Mo), (4) skarn (Fe, Zn, Cu), and (5) epithermal Au-Ag deposits. The hydrothermal veins are hosted by a range of different rock types, whereas the exhalative ores are confined to Permian strata. The porphyry deposits occur within granite porphyries. The epithermal deposits are related to Mesozoic volcanic-subvolcanic rocks and occur within superjacent igneous structures. The first type, represented by the Bairendaba deposit, shows many characteristics of hydrothermal deposits. The second type occurs in a Permian clastic-chemical sedimentary sequence. Most Fe-Zn-Cu deposits related to granites and granodiorites are skarns. Granodiorite and granite-related deposits are typical porphyry ores, formed during Hercynian and Mesozoic time. Promising metallogenic conditions and the recent discovery of many large metal deposits indicate that this mineral province has a great exploration potential.

Mineralogical characterization of Ishiagu (Nigeria) complex sulphide ore

A combination of SEM (Scanning Electron Microscopy) combined with Energy-Dispersive X-ray analysis (EDX), X-ray diffractometry (XRD), X-Ray Fluorescent (XRF) and Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) was used to characterize a bulk complex sulphide ore deposit in Ishiagu, in Ebonyin State, South Eastern part of Nigeria. A semi-geological study revealed characteristic hydrothermal vein deposits of the complex sulphide ore. Mineralogical analysis revealed the presence of siderite, sphalerite, galena, quartz, and traces of pyrite and copper bearing minerals. X-ray diffractometry showed that sphalerite mineral in the ore occurs as ferrous sphalerite with varied percentages of Zn and Fe within the various sizes. Scanning Electron Microscopy showed that the ore consist of fine to coarse grains, with less complex intergrowths of the constituent crystalline phases both at the interstitials and the boundaries with low interpenetrations.

A km-scale illite alteration zone in sedimentary wall rocks adjacent to a hydrothermal fluorite vein deposit

AbstractIn a study of wall-rock alteration in the 1.4 km long Würmtal adit at the Käfersteige hydrothermal vein deposit (northern Black Forest, Germany) illite was found to be the only clay mineral within the Bunter sandstone and intercalated claystone. Illite occurs mainly as a detrital mineral in the claystone, whereas it is hydrothermally neoformed in the sandstone, either in the pores or as an alteration product of K-feldspar. The extensive occurrence of authigenic illite along the entire 1.4 km long profile confirms that the fluids migrated far into the sandstone.The authigenic illite formed during a first pulse of high-temperature fluids (Th of ~220°C) with a low salinity (~1 wt.% NaCleq). These fluids also dissolved Sr and Rb from detrital illite of the claystones at the vein. A later hydrothermal pulse with a lower temperature (~70–150°C) and higher salinity (21–28 wt.% NaCleq) silicified the sandstone adjacent to the vein and caused partial substitution of OH- by F- in the structure of the detrital and neoformed illite along the profile.Within analytical error, the K-Ar dates for the neoformed illite of the &lt;2 µm fraction are the same along the profile (~150 Ma). During this hydrothermal process, the age of the detrital illite within the claystone was reset from 310 to 190 Ma. The illite-rich &lt;0.2 µm fractions yield ages of ~142 Ma (sandstone) indicating a Jurassic origin. The uniform age data for illite in the sandstone and in the claystone are probably due to extensive migration of hot fluids through the wall rocks.The hydrothermal fluids are attributed to recycled meteoric water and brines that ascended from the basement into the cover rocks during the opening of the North Atlantic and/or the nearby Tethys area.