Ore Belt Research Articles

Metallogenesis and the minerogenetic series in the Gangdese polymetallic copper belt

The Gangdese is a newly explored porphyry Cu ore belt in China. In fact, except for the porphyry Cu deposits there are a lot of other deposits, forming a polymetallic copper belt in the southern Gangdese (SG, i.e., southern Lhasa terrane) and Gangdese back–arc fault uplift belt (GBAFUB, also called Lungar–Nyainqêntanglha arc). The Gangdese polymetallic copper belt contains porphyry Cu(–Mo–Au), Cu–Au and Mo(–Cu), skarn Cu(–Mo–Au–W), Pb–Zn(–Ag), Fe(–Cu) and Mo–W, breccia-type and hydrothermal vein-type Pb–Zn(–Ag) deposits. The porphyry Cu–Au mineralization occurred at the Xiongcun area of SG during the Middle Jurassic (175–160Ma) and was associated with island arc magmatism related to the northward subduction of the Neo–Tethyan oceanic slab. The Cretaceous (ca. 112Ma) skarn Fe(–Cu) mineralization appeared at the Nixiong area of GBAFUB and was generated in a back arc extensional setting related to the Neo–Tethyan oceanic subduction beneath the Lhasa terrane. The Paleocene–Eocene (65–51Ma) porphyry Mo(–Cu), skarn Mo–W, and skarn Pb–Zn(–Ag) deposits are located in the eastern part of GBAFUB and related to granitoids originating from the partial melting of the old crust with contributions from the mantle. In contrast, the Paleocene–Eocene (60–45Ma) porphyry Cu, skarn-, breccia-, and hydrothermal-vein-type Pb–Zn(–Ag), and skarn Fe–Cu deposits at the Namling area were associated with granitoids derived from the partial melting of the mantle with some input of the old crust. The Oligocene (30–23Ma) porphyry–skarn Cu–Mo–W–Au mineralization occurred at the Zedong area adjacent to north of the Indus–Yarlung–Zangbo suture zone in a post collisional setting. The intensified Miocene (21–13Ma) porphyry–skarn Cu(–Mo–Au), and skarn–hydrothermal-vein-type Pb–Zn(–Ag) deposits formed in the SG, whereas the porphyry Mo(–Cu) and skarn–hydrothermal-vein-type Pb–Zn(–Ag) deposits formed in the GBAFUB. The porphyry Mo(–Cu) mineralization have more substantial contributions from the old crust, in addition to the mantle, than those with porphyry Cu(–Mo–Au) mineralization. The source region of the high Sr/Y intrusions associated with post collisional porphyry Cu(–Mo–Au) mineralization is probably the arc magmas that were generated at the subduction stage and have remained stalled at the boundary between the crust and mantle since the Neo–Tethyan Ocean closed. The early subduction of the Neo–Tethyan oceanic lithosphere played a crucial role in the generation of ore deposits formed in collisional and post collisional settings. Six minerogenic series (or groups) can be recognized in the Gangdese polymetallic copper belt: (1) Jurassic porphyry Cu–Au minerogenic series related to island arc magmatism, (2) Cretaceous skarn Fe(–Cu) minerogenic series in back arc extensional setting, (3) Paleocene–Eocene granitoids-related polymetallic minerogenic series in collisional setting, (4) Oligocene porphyry–skarn Cu–W–Mo–Au minerogenic series in post collisional setting, (5) Miocene Cu–Mo–Au–Pb–Zn–Ag minerogenic series related to granitoids with substantial contributions from the mantle in post collisional setting, and (6) Miocene Mo–Cu–Pb–Zn minerogenic series related to granitoids with significant contributions from the old crust in post collisional setting. During mineralization, some deposits underwent superimposed mineralization, such as the Jiru porphyry Cu deposit where the Eocene and Miocene porphyry-type Cu mineralization occurred. The minerogenic series can be applied to ore prospecting. For example, when either Pb–Zn(–Ag) veins or porphyry–skarn Mo(–W–Cu) orebodies are known in an area, one of them could provide a useful exploration vector for the other.

Processing and Analysis of Hyperspectral Fingerprints to Characterise Haematite of Singbhum Iron Ore Belt, Orissa, India

Abstract. The demand for iron ore has been increasing in the recent years, thereby requiring the adoption of fast and accurate approaches to iron ore exploration and its grade-assessment. It is in this context that hyperspectral sensing is deemed as a potential tool. This paper examines the potential of hyperspectral fingerprints in the visible, NIR and SWIR regions of the EMR to assess the grades of haematite of the western Singhbhum iron ore belt of Orissa, eastern India, in a rapid manner. Certain spectro-radiometric measurements and geochemical analysis were carried out and the results have been presented. From the spectral measurements, it is seen that the strength of reflectance and absorption at definite wavelength regions is controlled by the chemical composit ion of the iron ores. It is observed that the primary spectral characteristics of these haematites lie in the 650–750 nm, 850 to 900 nm and 2130–2230 nm regions. The laboratory based hyperspectral fingerprints and multiple regression analysis of spectral parameters and geochemical parameters (Fe% and Al2O3%) predicted the concentration of iron and alumina content in the haematite. A very strong correlation (R2 = 0.96) between the spectral parameters and Fe% in the haematite with a minimum error of 0.1%, maximum error of 7.4% and average error of 2.6% is observed. Similarly, a very strong correlation (R2 = 0.94) between the spectral parameters and Al2O3% in the iron ores with a minimum error of 0.04%, maximum error of 7.49% and average error of 2.5% is observed. This error is perhaps due to the presence of other components (SiO2, TiO2, P2O etc.) in the samples which can alter the degree of reflectance and hence the spectral parameters. Neural network based multi-layer perception (MLP) analysis of various spectral parameters and geochemical parameters helped to understand the relative importance of the spectral parameters for predictive models. The strong correlations (Iron: R2 = 0.96; Alumina: R2 = 0.94) indicate that the laboratory hyperspectral signatures in the visible, NIR and SWIR regions can give a better estimate of the grades of haematite in a rapid manner.

The Analysis of Geological Characteristics and the Genesis of the Deposit for Iron Ore Belt in Tengchong County, Yunnan Province, China

The Analysis of Geological Characteristics and the Genesis of the Deposit for Iron Ore Belt in Tengchong County, Yunnan Province, China

Petrography and geochemistry of Mesoarchaean komatiites from the eastern Iron Ore belt, Singhbhum craton, India, and its similarity with ‘Barberton type komatiite’

The Mesoarchaean supracrustals of the Gorumahishani–Badampahar belt, eastern India record sedimentation–volcanism like most other contemporary greenstone belts over the world. The current study reports unambiguous komatiitic rocks from Tua-Dungri hill, Gorumahishani–Badampahar belt, Jharkhand and presents a petrological and geochemical inventory of these very interesting rocks. The Tua-Dungri komatiites are characterised by a well distinguishable cumulate, platy and random spinifex zone. These Tua-Dungri komatiites are rich in SiO2 (47–50wt%) like Barberton type komatiite or modern day boninite. Their Al depleted nature (Al2O3=1.36–2.95wt%) with very low Al2O3/TiO2 (3.4–6.5) and high CaO/Al2O3 (2–3), high LREE/HREE ratios show further resemblance with the Barberton komatiite. The Tua Dungri komatiite data along with published geochemical, sedimentological and stratigraphic data from the Iron Ore Group of rocks suggest mantle plume activity during the Mesoarchaean on the Singhbhum craton.

Mineralogical characteristics of the karstic bauxite deposits in the Xiuwen ore belt, Central Guizhou Province, Southwest China

The karstic bauxite deposits in the Xiuwen ore belt of Central Guizhou Province are hosted by the Lower Carboniferous Jiujialu Formation and show parallel unconformity with the overlying and underlying strata. The ore-bearing rock series that exhibits a typical “coal–bauxite–iron” structure is divided into three segments from the bottom upward, namely, an iron layer, a bauxite layer, and a coal layer. Based on the textural features and iron abundances, the bauxite ores occurring in the middle segments are divided into three types of ores—clastic, compact, and high-iron. The bauxite ores primarily comprise diaspore, boehmite, kaolinite, illite, and hematite with minor zircon, pyrite, rutile, and feldspar. The existence of rutile within diaspore lumps, which were inherited from laterization, suggests that diaspore was transformed from gibbsite and that karstic bauxite was transformed from laterite bauxite. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe X-ray microanalyses (EPMA) suggest that diaspore and boehmite differ with regard to appearance and element abundance: diaspore (2–10μm) displays short prismatic or platy shapes and contains low SiO2 abundances (ranges from 0.2 to 0.51wt.%), whereas boehmite (0.2–5μm) exhibits granular or irregular shapes and contains high contents of SiO2 that vary between 2.71 and 10.4wt.%. The Fe–Cu–Pb–Zn–Ba sulfide and sulfate mineral assemblages associated with cryptocrystalline kaolinites are discovered in the Xiaoshanba deposit from the Xiuwen ore belt. Mineralogical and geochemical studies reveal that the genesis of these assemblages is controlled by the decomposition processes of organic matter and the activities of microorganisms within the ore-bearing rock series. Geochemical data suggest that elements rich in high-organic cryptocrystalline kaolinite are produced from the adsorption effect of organic matter, whereas the low concentration of these elements in pure kaolinite can be attributed to the scavenging effect during kaolinite crystallization. In addition, coexisting organic matter, cryptocrystalline kaolinite, and sulfide and sulfate minerals (see sample XSB-14) indicate that the forming environment of the bauxite was hot, humid tropical or subtropical climates.

Origin of the Tudun Cu–Ni sulfide deposit in the eastern Tianshan, NW China: Constraints on the geochemistry of platinum group elements

This study documents the geochemistry of sulfide ores of the Tudun Cu–Ni sulfide deposit, located at the western end of the Huangshan–Jing'erquan ore belt in the northern part of eastern Tianshan. The ores have been classified as (1) disseminated sulfide ores, (2) net-textured sulfide ores, and (3) massive sulfide ores.The geochemistry of barren rocks shows Ni and Cu contents ranged 889–1330ppm and 145–253ppm, respectively. The rocks generally contained ~0.10ppb Rh, Ir, Ru and Os, and ~1ppb Pt and Pd, as well as high Cu/Pd ratios (133–246). The contents of Cu, Ni and PGEs in sulfide ores were calculated on a 100% sulfide basis. Total PGEs on a 100% sulfide basis ranged from 13.2ppb to 443ppb (average=144ppb), which were lower than the values in the Huangshandong deposit (average=186ppb) in the eastern Tianshan ore belt, one order of magnitude lower than the Jinchuan deposit, and two orders of magnitude lower than the Noril'sk–Talnakh deposit. The R factor value ranged from 168 to 1810 in sulfide ores of the Tudun deposit, indicating Cu and Ni enrichment, although PGEs enrichment did not reach recoverable grades.In the Tudun deposit, the Pd/Ir ratio of sulfide ores was less than 100, showing weak hydrothermal fluid alteration. The massive sulfide ores exhibited less primitive mantle-normalized PGEs patterns, which are depleted in PPGEs and different from PPGEs-rich intrusions, as well as disseminated and net-textured sulfide ores. In addition, the massive sulfide ores exhibit a strong negative Pt anomaly. This may be due to fractionation of Pt–Fe alloys in the magma batches prior to its intrusion into the staging chamber. It could also be caused by selective Pt leaching from the sulfides by hydrothermal fluids during remobilization within the Tudun chamber.

A review on the Huoqiu banded iron formation (BIF), southeast margin of the North China Craton: Genesis of iron deposits and implications for exploration

The Huoqiu iron ore field in northwest Anhui Province is located in the North China Craton (NCC). As a large banded iron formation (BIF) iron ore field, ore bodies occur in a middle-high grade of Neoarchean metamorphic formation, forming a banded silicon–iron series from north to south. The main ore bodies can be divided into two sub-belts from bottom to upper layers, i.e. the A+B ore belt consisting of leptynite–schist–magnetite–quartz formation, and the D ore belt consisting of schist–marble–hematite–quartz formation. Based on a dataset from geological settings, geophysical and geochemical exploration, ore-forming conditions and structural analysis of the iron deposit, we discuss structural types, sedimentary environments, deep tectonic and ore-controlling factors as well as characteristics and distribution of this colossal BIF ore field in the Huoqiu region.Using LA-ICP-MS techniques, we obtained the oldest U–Pb age of ca. 2.7Ga for plagioclase amphibolite as its original rock, and 1.8Ga for magmatic granite in the Huoqiu Group. The Hf isotopes of zircon were also determined, resulting in the oldest Hf model age of 3.5Ga.Geochemical data indicate that the protolithes of amphibolites belong to a series of subalkaline rocks with enrichments of large ion lithophile elements and depletions of high field strength elements, which are typical volcanic arc rocks. The amphibolites have low K2O concentrations with low ratios of Ti/V (22.7 to 25.9 averaging 24.5), similar to island arc tholeiite. This suggests that the iron deposit and BIF are of the Superior type in the Huoqiu region.

Structure of the Outokumpu ore district and ophiolite-hosted Cu–Co–Zn–Ni–Ag–Au sulfide deposits revealed from 3D modeling and 2D high-resolution seismic reflection data

The Outokumpu district within the North Karelia Schist Belt in eastern Finland hosts a number of Cu–Co–Zn–Ni–Ag–Au sulfide deposits that are associated with Palaeoproterozoic ophiolitic metaserpentinites derived from depleted mantle peridotites that were subsequently tectonically interleaved with allochthonous metaturbidites. The metaperidotites have been extensively metasomatized to quartz–carbonate–calc–silicate rocks of the Outokumpu assemblage. The Outokumpu area has been affected by a multiple-phase tectonic history comprising various phases of folding and shearing followed by several faulting events. Future exploration has to expand the search into deeper areas and requires knowledge of the subsurface geology. In order to unravel the complex structure 3D geologic models of different scales have been built using a variety of information including geological aeromagnetic and gravity maps, digital terrain models, and mine cross sections as well as data like drill core logs combined with observations from underground mine galleries, structural measurements, aeromagnetic data, and seismic surveys. For crustal structures, data from seismic surveys lines have been reprocessed for our purpose. Both deposit-scale and regional-scale models allow the reconstruction of a sequence of structural events. The mined ore has formed during remobilization of a proto-ore and is closely related to shear zones (thrusts) that truncate the Outokumpu assemblage. Later faults dismembered the ore explaining the variable depth of the different ore bodies along the Outokumpu ore zone. On larger scale at least four km-scale thrust sheets, separated by major listric shear zones can be identified in the ore belt, which are internally further imbricated by subordinate shear zones. These thrusts separate a number of lens-shape metaperidotite bodies that are probably surrounded by Outokumpu assemblage rocks. Thrust stacking was followed by at least three stages of faulting that divided the ore belt into fault-bounded blocks with heterogeneous displacements: (i) faulting along NW-dipping faults with unresolved kinematics, (ii) reverse faulting along c. 50°–60° SE-dipping faults, and (iii) SW–NE to SSW–NNE striking faults which may have formed at an earlier stage and have been reactivated.The specific Outokumpu alteration assemblage around metaperidotite bodies combined with shear zones acting as path ways for fluids are the main vectors to mineralization. Seismic reflection data do not provide a simple tool to directly detect the sites of Outokumpu assemblage bodies at depth but they identify strong reflector zones which are characteristic for though not exclusive to the assemblage, shear zones can be recognized as curved dislocations in the seismic lines. Our study shows that 3D modeling, when used in combination with surface geology and other geophysical data and good knowledge about the structural evolution clearly improves the interpretation of reflectors and enables the identification of strong reflector packages as Outokumpu assemblage that, due to absent geological control, have first been mapped as “unknown reflector”. It thus enhances the chances for locating potentially economic horizons at depth and to delineate target areas for detailed exploration.

The mineral wealth of the Tethyan volcanic belts

In the short and medium term, gold and copper mining in the volcanic belts of the Tethyan Mediterranean Basin, as well as in the Pacific ore belt, will grow against the positive dynamics of world prices for these metals, the increasing financial backing of prospecting, and large investments in the construction of new mines. Mining companies are paying increasingly greater attention to countries with several large deposits that have been discovered, explored, and prepared for development, and whose commissioning is hindered only by the environmental factor. The total potential of gold and copper mining in the Tethyan volcanic belts could increase by 1.5–2 times in the near future.

LA-ICP-MS trace element analysis of pyrite from the Chang'an gold deposit, Sanjiang region, China: Implication for ore-forming process

The Chang'an gold deposit, Yunnan province is one of five large gold deposits in the Ailaoshan gold belt that is the most important ore belt of the Sanjiang Tethyan metallogenic domain. Geochemical study of pyrite in the deposit was conducted using laser ablation inductively coupled plasma mass spectroscopy. Three types of hydrothermal pyrite were identified in the ores and wall rocks, i.e., the coarse euhedral crystals in syenite (Py1), the coarse grains disseminated in altered sandstones or sandstone ores (Py2), and the fine-grained euhedral pyrite in sandstone ores (Py3). Their trace elements exhibit different concentrations, associations and rim–core zoning, implying different geneses and crystallization processes. The cores of Py1 were formed by magmatic fluids and have the lowest concentrations of Au, As, Cu and Zn. The cores of Py2 were formed by metamorphic fluids and have relatively high Au, Ag, Ni, Pb and Cu concentrations. The Py3 grains and the growth rims of Py1 and Py2 show consistently high contents of Au, As, Pb and Co, suggesting that all of them were rapidly deposited from a mixing fluid system that was probably composed of fluids of metamorphic and magmatic origins. This interpretation is supported by the observation that the high-grade ores generally contain lots of Py2 and Py3. Hence we consider that the deposit was formed during India–Asia collision, slightly postdate the 33–35Ma tectono-magmatism.

Petrogenesis of Early Cretaceous post-collisional granitoids at Shapinggou, Dabie Orogen: Implications for crustal architecture and porphyry Mo mineralization

The Shapinggou molybdenum deposit is located in the Qinling–Tongbai–Hong'an–Dabie Orogen, which accommodates the largest molybdenum ore belt in the world. New laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon U–Pb dating, geochemical and Sr–Nd–Hf isotope data for the granitoids at Shapinggou are presented in this paper. Two stages of Early Cretaceous magmatism, 138–128Ma and 116–114Ma, took place at Shapinggou in a post-collisional setting. These granitoids can be divided into four groups, including the early-stage granites (134–129Ma, SiO2=62.33 to 76.27%) and intermediate rocks (129–128Ma, SiO2=52.41 to 60.72%) and the late-stage quartz syenite (116Ma, SiO2=64.09 to 65.12%) and Mo-bearing granite porphyry (114Ma, SiO2=74.95 to 77.26%). The early-stage granites have high Sr contents, Sr/Y and LaN/YbN ratios, but low Y, Yb and MgO contents, showing low-Mg adakitic chemical features. They were possibly generated by partial melting of the thickened mafic lower continental crust. The early-stage intermediate rocks have relatively high MgO contents (2.71 to 4.84%) and Mg# values (46 to 60), but low Sr/Y and LaN/YbN ratios, which were likely derived from a hybrid mantle metasomatized by melts from foundered eclogitic lower continental crust and subsequent fractional crystallization. The late-stage quartz syenite shows chemical features of metaluminous A-type granites, including high abundances of alkalis, HFSE (Zr, Nb), and trivalent REE. The late-stage Mo-bearing granite porphyry displays high SiO2, alkalis, Zr, Ce contents, and A/CNK ratios, but low Ba, Sr, P and Ti, showing affinity to highly fractionated I-type granites. The late-stage quartz syenite and granite porphyry were possibly produced by partial melting of intermediate compositions of middle crust. Our results support the conclusion that there were three-layer continental crusts in the Dabie Orogen prior to Early Cretaceous magmatism and suggest that post-collisional granitoids in the Dabie Orogen were derived from not only lower crust but also middle crust. The giant Shapinggou porphyry Mo deposit was most likely formed by effective transport of volatiles and Mo in a convecting granitic magma column, rather than by direct melting of Mo-enriched sources. The Mo-bearing rocks at Shapinggou are characterized by a high degree of magma differentiation, close associations with A-type granite, and formation at the end of regional magmatism.

The occurrence of gold in pyrite from the Liulincha gold ore belt, western Hunan Province, China

In this study, an electron microprobe analyzer (EMPA) was used to map the spatial distribution and the occurrence of invisible gold in pyrite from the Liulincha gold ore belt. EPMA data show that gold mainly occurs as submicroscopic-microscopic inclusions. From the contrast of the major guide elements of pyrite from the Liulincha gold ore belt and those from four hydrothermal-type gold deposits in the Jiaodong region, we can see the pyrites were formed in two stages: the pyrite from wall rock is mainly sedimentogenic, with simple structure; and the pyrite from ore body experienced early sedimentary process to late hydrothermal activity, the pyrite is regular in crystal form and exhibits fractured structure.

Distribution of porphyry deposits in the Eurasian continent and their corresponding tectonic settings

In the Eurasian continent there are three huge metallogenic belts of Cu and Mo porphyry deposits, comprising the Paleozoic Central Asian Ore Belt in the north, the Tethyan Eurasian Ore Belt of Jurassic to Cenozoic age in the southwest, and the East Margin Ore Belt of the Eurasian Continent of Jurassic to Cretaceous age in the east. The latter is considered to be part of the vast Circum-Pacific ore belt. Some of the main features of the spatial–temporal distribution of Cu and Mo porphyry systems and related geodynamic processes of the three metallogenic belts are described. In particular, the key role of post-subduction – related porphyry ore systems is emphasized, comprising collisional and post-collisional Cu–Mo porphyry deposits during the geological history of the Eurasian continent. The recurrent feature of these ore systems and related felsic rocks is their derivation from partial melting of stagnant or residual oceanic slabs, and mixing with a variable amount of crustal material during magma ascent to shallower levels.

Geology and sulfur isotope geochemistry of Dafulou tin-polymetallic deposit in Dachang orefield, Guangxi, China

No. 22 ore of Dafulou deposit was systematically analyzed for sulfur isotopes. The results show that the δ34S values of sulfide minerals, ranging from −0.154 to +0.218% and with an average value of +0.114 1%, are mostly positive and characterized by rich sulfur (S) content. This suggests that the sulfur of the Dafulou ore deposit is derived from magma and relates to the Longxianggai concealed granite, which points to the important role of magma during mineralization and implyies the product of the active continental margin. By comparison between the Dafulou and the Kengma tin deposit, significant differences exist in the sulfur isotope composition. In the Kengma deposit, the sulfur isotope composition is characterized by the high negative value, which is different from the Dafulou tin-polymetallic deposit. The difference of the enrichment and fractionation of the sulfur isotope is the synthesized result of the metallogenic conditions. It also has the difference in the metallogenic environment and metallogenic characteristics of the deposit in the same ore belt.

Delineation of geochemical anomalies using factor analysis and multifractal modeling based on stream sediments data in Sarajeh 1:100,000 sheet, Central Iran

The aim of this study is to delineate the Cu, Au, and Pb anomalies in Sarajeh 1:100,000 sheet located in Urumieh-Dokhtar ore belt, central Iran. The analyzed elements of stream sediment samples taken in the area can be classified into six groups (factors) by factor analysis. The concentration–area and number–size multifractal inverse distance weighted models were applied for recognition of the elemental thresholds which are similar in both used multifractal models. According to the thresholds, the elemental concentration distribution for Cu, Au, and Pb were divided to three lithological classifications, namely mainly c alkaline porphyry with Cu–Au mineralization, mafic and sedimentary rocks. The results illustrate that the major anomalies of Cu, Au, Pb and related factors are mostly located around intrusions, volcanics, and along NW–SE faults.

Economic implications of epithermal gold-silver deposits

Gold and silver production in epithermal deposits of the Pacific ore belt has grown sharply over the last several years. In this context, the forecasting, study, and appraisal of these deposits in volcanogenic belts of Eastern Russia are among the most topical tasks of widening the available mineral resources of noble metals in the region.

Lead isotope composition and constraints on origin of Dafulou ore deposit, Guangxi, China

To discuss the material source and tectonic setting, the lead isotope composition was analyzed based on the samples from the latest tunnel of the Dafulou deposit. The lead isotope values are 17.478-18.431, 15.440-15.717, and 37.556-38.839 for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb, respectively. The values of Φ, μ, and Th/U are 0.592-0.638, 9.26-9.69 and 3.74-3.97. By comparing the lead isotope composition of the different ore belts, it indicates that the lead source of the west belt may be more single than the other ore belts. The lead isotope value in the middle and east belts are the maximum and minimum, respectively. In the Dachang ore district, the lead sources are comprised of the upper crust lead, the mixed crust and mantle subduction zone lead and the orogenic lead. The tectonic distinguish model suggests that the ore lead derived from both the mantle and crust. And, the upper crust and magmatism played an important role during the mineralization. The orogenesis also supplied a minority of ore lead. The ore deposit should be the result of the crust-mantle interaction and maybe had been formed in the orogenic environment.

Two geodynamic–metallogenic events in the Balkhash (Kazakhstan) and the West Junggar (China): Carboniferous porphyry Cu and Permian greisen W-Mo mineralization

This study focuses on the geochronology and elemental and Nd isotopic geochemistry of the Baogutu Cu deposit and the newly discovered Suyunhe W-Mo deposit in the southern West Junggar ore belt (Xinjiang, China), as well as the geology of the newly discovered Hongyuan Mo deposit in the southern West Junggar ore belt and the Kounrad, Borly, and Aktogai Cu deposits and the East Kounrad, Zhanet, and Akshatau W-Mo deposits in the North Balkhash ore belt (Kazakhstan). The aim is to compare their petrogenesis, tectonic setting, and mineralization and to determine the relationship between the southern West Junggar and North Balkhash ore belts. Based on our newly acquired results, we propose that the Kounrad, Borly, Aktogai, and Baogutu deposits are typical porphyry Cu deposits associated with calc-alkaline magmas and formed in a Carboniferous (327–312 Ma) subduction-related setting. In contrast, the East Kounrad, Zhanet, Akshatau, Suyunhe, and Hongyuan deposits are quartz-vein greisen or greisen W-Mo or Mo deposits associated with alkaline magmas and formed in an early Permian (289–306 Ma) collision-related setting. Therefore, two geodynamic–metallogenic events can be distinguished in the southern West Junggar and North Balkhash ore belts: (1) Carboniferous subduction-related calc-alkaline magma – a porphyry Cu metallogenic event – and (2) early Permian collision-related alkaline magma – a greisen W-Mo metallogenic event. The North Balkhash ore belt is part of the Kazakhstan metallogenic zone, which can be extended eastward to the southern West Junggar in China.

Geology, C–H–O–S–Pb isotope systematics and geochronology of the Yindongpo gold deposit, Tongbai Mountains, central China: Implication for ore genesis

The Yindongpo gold deposit is located in the Weishancheng Au–Ag-dominated polymetallic ore belt in Tongbai Mountains, central China. The ore bodies are stratabound within carbonaceous quartz–sericite schists of the Neoproterozoic Waitoushan Group. The ore-forming process can be divided into three stages, represented by early barren quartz veins, middle polymetallic sulfide veinlets and late quartz–carbonate stockworks, with most ore minerals, such as pyrite, galena, native gold and electrum being formed in the middle stage. The average δ18Owater values changed from 9.7‰ in the early stage, through 4.9‰ in the middle stage, to −5.9‰ in the late stage, with the δD values ranging between −65‰ and −84‰. The δ13CCO2 values of ore fluids are between −3.7‰ and +6.7‰, with an average of 1.1‰. The H–O–C isotope systematics indicate that the ore fluids forming the Yindongpo gold deposit were probably initially sourced from a process of metamorphic devolatilization, and with time gradually mixed with meteoric water. The δ34S values range from −0.3‰ to +5.2‰, with peaks ranging from +1‰ to +4‰. Fourteen sulfide samples yield 206Pb/204Pb values of 16.990–17.216, 207Pb/204Pb of 15.419–15.612 and208Pb/204Pb of 38.251–38.861. Both S and Pb isotope ratios are similar to those of the main lithologies of the Waitoushan Group, but differ from other lithologic units and granitic batholiths in the Tongbai area, which suggest that the ore metals and fluids originated from the Waitoushan Group. The available K–Ar and 40Ar/39Ar ages indicate that the ore-forming process mainly took place in the period of 176–140Ma, during the transition from collisional compression to extension and after the closure of the oceanic seaway in the Qinling Orogen. The Yindongpo gold deposit is interpreted as a stratabound orogenic-style gold system formed during the transition phase from collisional compression to extension.The ore metals in the Waitoushan Group were extracted, transported and then accumulated in the carbonaceous sericite schist layer. The carbonaceous sericite schist layer, especially at the junction of collapsed anticline axis and fault structures, became the most favorable locus for the ore bodies.

SHRIMP U-Pb DATING ON HYDROTHERMAL ZIRCONS: EVIDENCE FOR AN EARLY CRETACEOUS EPITHERMAL EVENT IN THE MIDDLE JURASSIC DEXING PORPHYRY COPPER DEPOSIT, SOUTHEAST CHINA

The Dexing porphyry copper deposit, part of the circum-Pacific porphyry copper ore belt, is the largest porphyry copper deposit in China (1,500 million tonnes [Mt] of ore at 0.43% Cu, 0.02% Mo, and 0.16 grams per tonne Au, approximately equivalent to 6.45 Mt Cu, 0.25 Mt Mo, and 24 tonnes Au). We report results of sensitive high resolution ion microprobe (SHRIMP) U-Pb dating on zircons separated from a thick (~20-cm-wide) pyrite-chalcopyrite-quartz vein in this deposit, which is mineralogically and texturally different from the porphyry-related ore-bearing thin quartz veins. The zircons from the thick quartz vein are unzoned and nonluminescent (black) in the cathodoluminescence images. They show relatively flat light rare-earth element patterns and have high La content and low (Sm/La)N and Ce/Ce* values. These features are typical of hydrothermal zircons. SHRIMP U-Pb dating on these hydrothermal zircons yielded weighted mean 206Pb/238U ages of 106.5 ± 0.9 and 100.9 ± 3.5 Ma, which are ca. 70 m.y. younger than the ages (172–171 Ma) of the ore-bearing porphyries and the molybdenite Re-Os ages (170.9 ± 1.1 Ma) of the porphyry-related disseminated and veinlet (usually <1 cm in width) ores. This suggests the occurrence of a younger, distinct Cu (Au?) hydrothermal event superimposed on the porphyry Cu-Mo-Au mineralization at Dexing. The mineralogical features and age of this hydrothermal event suggest that it could belong to the metallogenic event responsible for the formation of the late Early Cretaceous to early Late Cretaceous (110–95 Ma) epithermal Cu-Au-Ag deposits in southeast China.