Regional Metallogeny Research Articles

The main features of regional metallogeny of the Zimbabwe Craton

The main features of regional metallogeny of the Zimbabwe Craton

Carboniferous magmatic activity in the Aqishan–Caixiashan polymetallic ore cluster, eastern Tianshan, NW China: implications for tectonic evolution and regional metallogeny

Carboniferous magmatic activity in the Aqishan–Caixiashan polymetallic ore cluster, eastern Tianshan, NW China: implications for tectonic evolution and regional metallogeny

Sulfur and Carbon–Oxygen Isotopic Geochemistry and Fluid Inclusion Characteristics of the Yolindi Cu-Fe Skarn Mineralization, Biga Peninsula, NW Turkey: Implications for the Source and Evolution of Hydrothermal Fluids

The current study sought to investigate the physiochemical conditions and fluid evolution within the Yolindi Cu-Fe skarn mineralization located in the Biga Peninsula, NW Turkey. This was accomplished through a comprehensive investigation of geological and mineralogical data, along with isotopic analyses of sulfur (δ34S), carbon (δ13C), and oxygen (δ18O) of sulfide and calcite minerals, respectively, as well as fluid inclusion data pertaining to various minerals (e.g., andradite, quartz, and calcite). The Yolindi area features a complex geological framework, including the Paleozoic Kalabak Group (which includes the Torasan, Yolindi, and Sazak formations) and the Triassic Karakaya Complex. These formations were subsequently intruded via Early Miocene Şaroluk granitoids and Hallaçlar volcanics. Skarn formation is zoned into endoskarn and exoskarn types (being categorized into proximal, intermediate, and distal zones), with distinct mineral assemblages indicating concentric and contact metamorphic alteration patterns around the western part of Şaroluk granitoid intrusion in contact with the Torasan formation. The ore mineralogy and paragenesis suggest three distinct stages of evolution: an initial phase of prograde metasomatism characterized by the formation of magnetite and pyrite alongside anhydrous calc-silicate minerals; a subsequent phase of retrograde alteration marked by the formation of epidote, actinolite, and scapolite, accompanied by the occurrence of chalcopyrite and specular hematite; and finally, a post-metasomatic stage involving oxidation processes that led to the development of secondary mineral assemblages containing cerussite, covellite, and malachite. Sulfur isotopes (δ34S) of sulfides from endoskarn (from +0.27 to +0.57‰VCDT) to intermediate exoskarn (from −9.44 to −5.46‰VCDT) zones indicate a diverse sulfur source, including magmatic, sedimentary, and possibly organic matter. δ34S values in hydrothermal fluids suggest a magmatic–hydrothermal origin, with endoskarn and proximal zone fluids showing a slight negative signature and intermediate zone fluids indicating a strong influence from organic-rich or metamorphic sulfur reservoirs. Carbon and oxygen isotopic compositions (δ13C and δ18O) of calcite revealed a progression from marine carbonate signatures in marble samples (from +1.89 to +2.23‰VPDB; from +21.61 to +21.73‰VSMOW) to depleted values in prograde (from −6.0 to +0.09‰VPDB; from +6.22 to +18.14‰VSMOW) and retrograde skarns (from −3.8 to −2.25‰VPDB; from +0.94 to +3.62‰VSMOW), reflecting interactions with high-temperature magmatic fluids and meteoric water mixing. The fluid inclusions in prograde minerals generated under the conditions of fluid boiling exhibited high temperatures, reaching up to 412 °C, and salinities up to 26 wt.% NaCl equivalent. Conversely, the fluid inclusions in retrograde minerals, which were generated due to fluid mixing, exhibited lower temperatures (with an average of 318 °C) and salinities with an average of 4.9 wt.% NaCl equivalent. This indicated that the cooler and more diluted fluids mix with meteoric waters and interact with organic materials in the host rocks. This suggests a multifaceted origin involving various sources and processes. Therefore, this study concluded that the skarn mineralization in the Yolindi area resulted from complex interactions between magmatic, metamorphic, and meteoric fluids, reflecting a dynamic ore-forming environment with implications for the regional metallogeny of Cu-Fe skarn deposits.

Two episodes of carbonatite-related rare-earth element mineralization in the Nam Xe deposit, northwestern Vietnam: Implications for ore genesis and regional metallogeny

Carbonatite-related rare-earth element (REE) deposits are developed in large areas of southwestern China and northwestern Vietnam on the SW margin of the South China block. The ages of REE deposits and their host carbonatite-alkaline rocks in southwestern China have been tightly constrained in the 35–10 Ma interval, but those in northwestern Vietnam remain poorly understood. In this paper, we present new Th–Pb dating results to constrain the timing of mineralization of the Nam Xe REE deposit in northwestern Vietnam, and to reveal its possible relationship to the well-studied REE deposits in southwestern China. The Nam Xe deposit consists of three types of REE ores: Type 1, fine-grained disseminated ores; Type 2, coarse-grained, taxitic ores; and Type 3, REE veinlets. The mineral assemblages and their close relations to hydrothermal alteration, combined with the trace element patterns of the ore minerals, indicate a hydrothermal origin for all the three ore types. Laser ablation-inductively coupled plasma-mass spectrometry Th–Pb dating of monazite yielded weighted-mean Th–Pb ages of 45–44 Ma for type 1 ores and 35–32 Ma for type 2 and 3 varieties, whereas the LA-ICPMS dating of bastnäsite has ages of 35–31 Ma for types 2 and 3, revealing two REE mineralization events at 45–44 and 35–31 Ma in the Nam Xe deposit. The age of type 1 ores overlaps the main-collision period of India-Asia collisional orogeny (65–41 Ma) which confirms carbonatite-related REE mineralization could form in the main-collisional geological setting. The ages of types 2 and 3 ores are consistent with those of the Mianning–Dechang REE metallogenic belt in southwestern China that formed under a late-collision extensional setting (40–26 Ma). Combined with existing geochronological data, results presented here suggest that the Nam Xe REE deposit formed both in the main- and late-collisional settings and represents the southern extension of the Mianning–Dechang REE metallogenic belt.

Crustal architecture and metallogeny associated with the Paleo-Tethys evolution in the Eastern Kunlun Orogenic Belt, Northern Tibetan Plateau

The Eastern Kunlun Orogenic Belt (EKOB) in the Northern Tibet Plateau hosts a wide variety of metal deposits related to the Late Paleozoic to Mesozoic magmatism. In this study, we investigate the spatio-temporal distribution of the Late Paleozoic to Mesozoic granitic rocks and associated metal deposits in the EKOB and provide a comprehensive compilation of the geochronological, geochemical and isotopic data on these rocks. We compute regional zircon Hf isotope and crustal thickness maps from the data, based on which a comprehensive model is proposed involving subduction (ca. 270–240 Ma), continental collision (ca. 240–224 Ma), and post-collisional extension (ca. 224–200 Ma) for the Late Paleozoic to Mesozoic Paleo-Tethys evolution in the EKOB.Zircon Hf isotopic and crustal thickness mapping of Late Paleozoic to Mesozoic magmatic rocks was carried out to evaluate their spatio-temporal and genetic links with the regional metallogeny. The polymetallic Fe-skarn and porphyry Cu (Mo) deposits in the EKOB are located above the Moho uplift region, featuring a comparatively thin crust. Granites associated with porphyry Cu (Mo) and polymetallic Fe skarn mineralization are commonly characterized by high εHf(t) and younger TDMc values, whereas granite related to Cu-Mo-Sn skarn deposits exhibit more variable εHf(t) values, TDMc ages, and the crust thickness, which suggest that more crustal materials contributed to the formation of Cu-Mo-Sn skarn deposits than those for porphyry Cu (Mo) and polymetallic Fe skarn mineralization. In contrast, vein-type Au deposits are located primarily where the Moho surface displays a depression, i.e., where the continental crust is relatively thick. The magmatic rocks associated with Au mineralization are characterized by low εHf(t) and high TDMc values, representing reworked ancient crustal components, similar to those associated with porphyry Mo and epithermal Ag-Pb-Zn-(Au) deposits. Our study indicates that the emplacement of magmatic-hydrothermal deposits was controlled by the crustal structure and magma sources.

The ~1.1 Ga St. Ignace Island complex, Northern Ontario, Canada: Evidence for magma mixing and crustal melting in the generation of Midcontinent Rift-related bimodal magmas and implications for regional metallogeny

Abstract The St. Ignace Island complex in Northern Ontario is a package of dominantly felsic rocks emplaced within the upper portions of the Osler Volcanic rocks of the ~1.1 Ga Midcontinent Rift System. The Osler volcanic rocks are predominantly tholeiitic basalts intercalated with rare interflow sediments and rhyolites. The St. Ignace Island complex is a ~26 km2 stock with a felsic core of quartz-feldspar-phyric rhyolites and dacites and an outer ring of anorthosite and gabbro. Textures at a variety of scales within the rocks of the complex show clear evidence of the mingling and mixing of partially crystallized mafic and felsic liquids. Two multigrain (zircon/baddeleyite) fractions from a sample of the gabbro define a Discordia line with an upper intercept date of 1107±8.9 Ma. The core of the complex consists of dacites and rhyolites with similar REE abundances with negative Nb anomalies whereas the surrounding mafic rocks are gabbros to monzogabbros that are less LREE-enriched than the felsic rocks but with similar HREE. Felsic units have a narrow range of 87Sr/86Sri (0.7032-0.7045) and 143Nd/144Ndi (0.51051-0.51057) whereas the mafic end members have similar 87Sr/86Sri (0.7040-0.7061) but more radiogenic 143Nd/144Ndi (0.51067-0.51085). Very well-preserved silicate melt inclusions (MI), many completely glassy, were observed in quartz, clinopyroxene and some plagioclase phenocrysts from the complex. These represent some of the oldest unrecrystallized silicate melt inclusions described to date. Melt inclusions within quartz from the felsic volcanics are broadly rhyolitic in composition whereas MI from plagioclase in the mafic volcanics range from basalt to basaltic andesite; these felsic and mafic melt compositions are interpreted to represent the end-member liquids in the system and bulk rock analyses affirm mixtures of the two. Concentrations of Cu and Ag (in both mafic and felsic MI), and Mo (in felsic MI), are up to an order of magnitude higher in the mafic and felsic MI than in continental crust. Bulk rock metal concentrations are also significantly lower than in the MI, suggesting that the melt inclusions may preserve pre-eruptive metal tenors that were subsequently modified by sulfide saturation, degassing, or post-solidus hydrothermal alteration. The whole rock and MI geochemistry of the St. Ignace complex are broadly similar to the Central Osler Group and, given the broad similar ages, suggests they may have been derived from a similar mantle source, but distinct from the source of rhyolites in the Black Bay Peninsula. The negative Nb anomalies and negative εNd values for the St. Ignace complex are consistent with mixing with older continental crust during ascent and emplacement. The rocks of the St. Ignace Island complex likely formed as the result of emplacement of a large mafic magma chamber at the base of the Osler volcanic pile that triggered partial melting to generate the rhyolite end members. The felsic melts ascended to shallower levels in the crust where they mixed with mafic magmas derived directly from the deeper chamber. Generally, melt inclusions in the complex have very high Cu and Ag contents, similar to those observed in arc-related and extremely oxidized early rift-related rocks and may account for the world-class volcano-sediment-hosted Cu-(Ag) deposits within the rift and the presence of small porphyry-style deposits.

Insights into Regional Metallogeny from Detailed Compositional Studies of Alluvial Gold: An Example from the Loch Tay Area, Central Scotland

Compositional features of a total of 1887 gold alluvial particles from six localities to the south of Loch Tay in central Scotland were interpreted to establish different types of source mineralization. Populations of gold particles from each locality were grouped according to alloy and inclusion signatures. Inclusion suites provided the primary discriminant with gold from Group 1 localities showing a narrow range of simple sulphide and sulphoarsenide inclusion species, whereas a wide range of minerals including molybdenite, bornite and various Bi and Te- bearing species were identified in gold from Group 2 localities. Whilst the range of Ag in alloys in all populations was similar, higher incidences of measurable Hg and Cu were detected in Group 1 and Group 2 gold samples respectively. The application of compositional templates of gold from other localities worldwide indicated that Group 1 gold is orogenic and Group 2 gold is a mixture of porphyry and epithermal origin; a result that is sympathetic to the spatial relationships of sample localities with local lithologies. This approach both provides an enhanced level of understanding of regional gold metallogeny where in situ sources remain undiscovered, and permits clearer targeting of deposit types during future exploration.

Petrogenesis and metal fertility of Yinzu pluton in the Daye district, eastern China: Insights from whole-rock and mineral (zircon, apatite and amphibolite) geochemistry

The Daye district in eastern China is featured by numerous granitoid intrusions of Early Cretaceous ages that intrude Paleozoic to Early Triassic marine carbonate and clastic rocks. Several dozen skarn Cu-Fe-Au deposits occur along the intrusive contact zones of the Echeng, Tieshan, Jinshandian, Lingxiang, Tongshankou and Tonglushan intrusions. However, no economic skarn mineralization has been recognized in other intrusions and whether or not these intrusions are metal fertile remain unresolved. In this paper, we use whole-rock and mineral (zircon, apatite and amphibole) geochemistry to provide significant new insights into the petrogenesis and metal fertility of the Yinzu granitoid pluton.The Yinzu pluton mainly consists of quartz diorite and diorite phases that have zircon U-Pb ages of 148.4 ± 1 Ma and 146.6 ± 1.6 Ma, respectively. Whole-rock Sr-Nd isotopic compositions ((87Sr/86Sr)i = 0.70635 to 0.70741; εNd(t) = −8.74 to −3.73) and zircon hafnium isotopes (εHf(t) = −9.1 to −4.8) overlap with values of the Cu-fertile Tongshankou and Tonglushan granitoids, implying a common enriched lithospheric mantle source. The whole-rock geochemical data suggest that both the diorite and quartz diorite have experienced variable degrees of fractional crystallization of olivine, amphibole, titanite and magnetite. The Ce4+/Ce3+ ratios (16–445) and oxygen fugacity (logfO2) calculated using trace element concentrations of zircon (ΔFMQ = +0.2 to +2.4) suggest that both intrusive phases crystalized from oxidized melts similar to Cu-fertile magmas in the world, with the quartz diorite being well comparable to the Tongshankou and Tonglushan granitoids. Based on available melt-apatite partitioning models, the estimated S and Cl contents for the magmas parental to the Yinzu pluton are akin to those of the Cu-fertile granitoids in the Daye district. Rocks of the Yinzu pluton display high apatite Sr/Y (0.38–3.01) and Eu/Eu* (0.35–0.71) ratios as well as high zircon Eu/Eu* (0.51–0.86) and 10000*(Eu/Eu*)/Y (2–27) ratios, indicating significant fractionation of amphibole with limited plagioclase fractionation and high magmatic water contents (>4 wt% H2O). This view is consistent with the calculated melt H2O content of 4.3–6.1 wt% based on the amphibole compositions.Collectively, results presented here indicate that magmas generating the Yinzu pluton are hydrous, oxidized and S-rich, characters similar to the Cu-fertile granitoids in Daye and elsewhere. Thus, the Yinzu pluton is considered to be Cu-(Au) fertile. This consideration is partially supported by occurrences of several vein-type Cu prospects within and disseminated Au ores in Silurian clastic sedimentary rocks immediately to the southeast of this pluton. Based on the regional metallogeny and results of this study, we suggest that the Yinzu pluton is a promising target of future Cu-(Au) exploration.

Metallogeny of the Hunjiang basin, northeastern North China block

The Hunjiang basin in the northeastern North China block is host to a wide range of ore deposit types that are currently exploited by more than 100 past and producing mines. Extensive field and laboratory investigations were conducted to summarize the regional metallogeny, classify the different deposit types, and to place the deposits within a regional geologic and tectonic context. The Archean basement of the basin is host to magnetite deposits that have been affected by high-grade metamorphism. In addition, Proterozoic magmatic Cu-Ni deposit and orogenic Au deposits that are likely of Mesozoic age are located in the metamorphic basement rocks. Polymetallic Co-Cu and Ni-Co-Cu deposits are located in Proterozoic schists within the basin and are of pre- to syn-metamorphic origin. However, most deposits in Hunjiang basin can be related to Mesozoic igneous activity. This includes porphyry Cu and Cu-Mo deposits as well as associated skarns and carbonate replacement deposits. Economically most significant are Au deposits hosted in Proterozoic limestone and dolomite that are located distal to the Mesozoic igneous intrusive centers. This includes the White Mountain deposit near Baishan City, which contains an endowment of more than 50 tonnes Au. There are no known high-sulfidation epithermal deposits within the Hunjiang basin, which is consistent with fluid inclusion evidence demonstrating that emplacement of the porphyry intrusions occurred at significant depth below the paleosurface. Geochronological constraints indicate that Mesozoic igneous activity and associated deposit formation in the Hunjiang basin occurred as a result of Jurassic subduction processes and subsequent extension after slab rollback and lithospheric delamination under the Eastern North China Block in the Cretaceous. Future mineral exploration efforts in the Hunjiang basin should focus on the distal sedimentary rock-hosted Au deposits associated with Mesozoic intrusions, with special emphasis on the northern part of the basin where these deposits occur preferentially at the intersection of extensional faults with a vanished evaporite unit that is distinctly enriched in Fe oxides providing a chemical trap.

New insights about the origin of the Shilu Fe-Cu-Co deposit, Hainan Island, South China, with emphasis on the regional metallogeny

New insights about the origin of the Shilu Fe-Cu-Co deposit, Hainan Island, South China, with emphasis on the regional metallogeny

The link between Paleo-Tethys subduction and regional metallogeny in the SW Yangtze Block: New evidence from the Zubu carbonate-hosted F-Pb-Zn deposit

The lead–zinc mineralization belt along the southwestern margin of the Yangtze Block is one of the important source for lead, zinc, germanium and silver in China. More than 50% of the deposits in the region occur in carbonate rocks ranging in age from late Ediacaran to early Cambrian. Here we investigate the large Zubu F-Pb-Zn deposit located in the southwestern margin of the Yangtze Block. The ore bodies strike nearly NS in the dolomite fracture zone in the second member of the Cambrian Longwangmiao Formation and discontinuously extend for 0.7 km long. We present Sm-Nd isotopic data on the fluorite ore that yield an isochron age of 211 ± 11 Ma. Fluid inclusions in the fluorite show homogenization temperature between 88 and 247 °C with a peak at 130–180 °C, with salinity ranging between 0.18 and 22.23 wt% NaCl eqv. (average of 9.24 wt% NaCl eqv.), the ore-forming fluid has the characteristics of medium–low temperature and medium–low salinity. The rare earth element (REE) signature of fluorite display positive Eu anomaly and negligible negative to weak positive Ce anomaly. The δ18OV-SMOW values range from 0.6 − 4.7 ‰, δDV-SMOW values range from −41.1–27.6 ‰, fluorite Sr isotopic values range from 0.710668 to 0.711585, and galena Pb isotope ratios with the value of 206Pb/204Pb = 18.551–18.564, 207Pb/204Pb = 15.676–15.693, 208Pb/204Pb = 38.869–38.809. The field, petrologic, geochemical and isotopic data from our study lead to the following salient findings. (1) The ore-forming fluid of the F-Pb-Zn deposit was derived from the mixture of metamorphic water flowing through the basement with basin hot brine and meteoric water. (2) The ore-forming material of the deposit comes from the basement and sedimentary strata. (3) In conjunction with the geochronological data of regional ore deposits, the large-scale mineralization is inferred to have formed during a transitional stage from compression to extension setting related to the Indosinian orogeny after the closure of the late Triassic-early Jurassic (220–190 Ma) Paleo-Tethys Ocean.

The fractionation of iron isotope and its constraints on the sources of ore-forming materials in the Jinchanghe skarn polymetallic deposit in Sanjiang region, Southwest China

金厂河矿床是西南三江成矿省保山地块最具代表性的远端矽卡岩型多金属矿床之一，查明其成矿金属来源对理解该类矿床成因以及区域成矿规律具有重要意义。本文通过分析不同成矿阶段代表性含铁矿物的铁同位素组成，探讨其在成矿过程中的分馏机制，从而示踪成矿金属的源区特征。金厂河矽卡岩型矿床中成矿前阶段未蚀变的石榴子石和氧化物成矿阶段的磁铁矿均相对富集铁的重同位素，其δ⁵⁶Fe值分别为0.05‰~0.16‰和0.07‰~0.18‰，而硫化物成矿阶段的黄铁矿和黄铜矿则相对富集铁的轻同位素，其δ⁵⁶Fe值分别为-0.12‰~0.17‰和-0.54‰~-0.38‰，整体显示出从高氧逸度的成矿前阶段向低氧逸度的硫化物成矿阶段演化过程中矿物δ⁵⁶Fe值逐渐降低的趋势，指示Fe³⁺富集铁的重同位素，Fe²⁺富集铁的轻同位素。同时，金厂河矿床各阶段矿物的δ⁵⁶Fe值均显著低于碳酸盐围岩，而接近全球花岗岩的δ⁵⁶Fe值，表明成矿的铁不是由围岩贡献，而是来自于隐伏的中酸性岩体。;Jinchanghe is a representative distal skarn polymetallic deposit in Baoshan block in the Sanjiang metallogenic province, finding out the sources of ore-forming metals is of great significance to understand the genesis of deposit and regional metallogeny. In this study, we analyzed the iron isotopic compositions of Fe-bearing minerals from different stages, to investigate the fractionation mechanism of iron in ore-forming process, and to trace the sources of ore-forming metals. The unaltered garnet from pre-ore stage and magnetite from oxide-ore stage in Jinchanghe skarn deposit are relatively rich in heavy isotopes of iron, with δ⁵⁶Fe values of 0.05‰~0.16‰ and 0.07‰~0.18‰, respectively. Whereas, the pyrite and chalcopyrite from sulfide-ore stage are relatively rich in light isotope, with δ⁵⁶Fe values of -0.12‰~0.17‰ and -0.54‰~-0.38‰, respectively. All results show that, from pre-ore stage of high oxygen fugacity to sulfide-ore stage of low oxygen fugacity, the δ⁵⁶Fe values of minerals gradually decrease, indicating that the heavy isotope of iron is enriched in Fe³⁺, but the light isotope of iron is enriched in Fe²⁺. Furthermore, the iron isotopes of minerals from different stages in Jinchanghe are significantly lower than that of carbonate wall rock, and close to that of global granite, implying that the ore-forming iron are not contributed by wall rock, but from the concealed granitic rocks.

A New Approach to Characterizing Deposit Type Using Mineral Inclusion Assemblages in Gold Particles

Abstract Mineral inclusions within native gold are features of lode gold occurrences that are preserved in detrital particles. Inclusion assemblages in populations of gold particles in placers from specific localities are revealed through inspection of polished sections, and assimilation of robust data sets permits reconstruction of the lode source mineralogy. Inclusion assemblages differ considerably according to the source deposit type, and various approaches have been employed to graphically represent inclusion mineralogy. We present a simple method for depicting and comparing inclusion assemblages using a single standardized radar diagram template that illustrates the proportions of 11 metal and five nonmetal (and metalloid) elements in each inclusion assemblage. The Canadian Cordillera hosts many different gold-bearing deposit types and is an ideal terrane in which to develop a globally applicable methodology. Although placer gold is widespread, the location and nature of source mineralization is commonly unclear. This study is based on the inclusion suites recorded in 37 sample sets of gold particles from both placer and lode localities. Radar diagrams describing inclusion assemblages show clear generic differences according to deposit type. Diagnostic signatures have been established and act as templates against which samples of unknown origin may be compared. This approach permits differentiation between populations of gold particles formed in different magmatic systems (low-sulfidation epithermal, calc-alkalic porphyry, and alkalic porphyry), which may all be distinguished from gold formed in orogenic (amagmatic) mineralization. Metallic element signatures are most useful in differentiating gold from different magmatic hydrothermal systems, whereas nonmetallic elements allow for classification of orogenic gold subtypes. Comparisons of mineral inclusion signatures from gold in the Canadian Cordillera to samples from similar geologic settings worldwide suggest that this approach to gold fingerprinting is globally applicable. Therefore, the geochemical signatures of inclusion assemblages provide a robust indication of deposit type and may be applied in exploration to illuminate regional metallogeny in areas where relationships between placer deposits and their source(s) may be unclear.

Origin of the post-collisional carboniferous granitoids associated with the Azhahada Cu-Bi deposit in Inner Mongolia, Northeast China and implications for regional metallogeny

The Azhahada quartz vein-type Cu-Bi deposit is located in the Erenhot-East Ujimqin polymetallic metallogenic belt, on the western part of the Great Xing’an Range, Inner Mongolia, northeast China. The Cu-Bi veins are hosted by volcanic and metasedimentary rocks in the Devonian Niqiuhe Formation and Carboniferous felsic intrusions (monzogranite, syenogranite, and granite). Three hydrothermal ore stages (I-III) for Cu-Bi formation at Azhahada have been identified. Chalcopyrite and bismuthinite are the dominant ore minerals and mainly occur in vein stage II (quartz–pyrite ± chalcopyrite ± bismuthinite veins). New LA-ICP-MS zircon U-Pb dating indicates the monzogranite, syenogranite, and granite emplaced between 313.9 ± 1.7 and 308.4 ± 1.5 Ma. The monzogranite, syenogranite, and granite show the same geochemical affinity with I-type granites, which are characterized by high SiO2, K2O, and Al2O3 contents, low MgO, TiO2, and P2O5 contents, negative Eu anomalies (EuN/EuN* = 0.04–0.57), and strong enrichment in Rb, K, Pb, and Nd. Moreover, these granitic intrusions have low Mg# values of 22 to 39, low (87Sr/86Sr)i ratios (0.7023 to 0.7053), εNd(t) values between −0.8 and +0.4, positive εHf(t) values of +1.6 to +10.4, suggesting that their parental magmas were most likely derived from partial melts from the lower crust involving some mantle materials in a post-collisional tectonic setting. Sulfide samples from Azhahada have 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios similar to those of granitic intrusions. The silicon isotope compositions of the quartz samples (−0.3 to −0.1‰) are highly consistent with values of the granitic intrusions (−0.4 to −0.1‰), indicating that the silicon was derived from the granitic magma. Combined our whole-rock geochemical and Sr–Nd–Hf–Pb–Si isotopic data with previous investigation of regional tectonic evolutions, we suggest that the Azhahada granitoids genetically associated with the Cu-Bi mineralization were generated by the postorogenic lithospheric extension and magmatic underplating during the Late Carboniferous. A post-collisional extensional event coupled with the rising of hot mantle derived melts triggered partial melting of the lower crust, as well as provided metals (Cu and Bi).

Inspiration of magma source and intrusion of Niukutou polymetallic ore area: evidence from audio frequency magnetotelluric(AMT)

Niukutou research area is located in the north slope of Qimantage mountain in the east Kunlun, which is an important part of the lead, zinc, copper and iron metallogenic belt. The regional mineralization is inseparable from Indosinian magmatism. However, the research area is covered by Quaternary stratum area and the trace of magmatic activity is difficult to find. In order to further understand the underground structure, the spatial distribution characteristics of magmatic rocks and the relationship with polymetallic mineralization of the research area, the audio-frequency magnetotelluric (AMT) survey is deployed. Through the comprehensive analysis based on the electrical structure, we found that the granites encountered in the research area are from the magma source corresponding to the deep F3 channel, the granites are occurred as the veins from multi-channels. There are no granites base in the profiles and the regional metallogeny are controlled by the magma activity and the fault F3.In geologic modeling process of groundwater system, block modeling needs to be established.

Geology, Geochemistry and Re-Os Age of the Qiaoxiahala Deposit in NW China: Evidence of an Overprinted Fe(-Cu/Au) Deposit

Overprinting of an earlier formed deposit may obscure the nature of the deposit and hinder our understanding of regional metallogeny. The Qiaoxiahala Fe(-Cu/Au) deposit in eastern Junggar, NW China, is characterized by magnetite mineralization later replaced by sulfide minerals such as chalcopyrite. To reveal the genesis of Qiaoxiahala, we conducted Re-Os dating on post-magnetite molybdenite separated from chalcopyrite and rare earth elements (REEs) for basaltic volcanic rock, magnetite, chalcopyrite and diorite. An isochron age of 377±7 Ma was obtained together with a weighted mean age of 375±3 Ma, which is indistinguishable from mineralization ages determined in previous studies. Rare earth element (REE) data for basaltic volcanic rocks hosting the ore are comparable to that of the magnetite, while the REE signatures of chalcopyrite from the Cu ore and local intrusive diorite share a similar pattern. These suggest that two distinct fluid sources are responsible for the deposition of Fe and Cu in the Qiaoxiahala deposit. According to these experimental results, we consider that the iron mineralization in Qiaoxiahala is the result of fluid exsolution from basaltic volcanism which was further overprinted by fluids that deposited copper and gold, which may have been sourced from nearby dioritic intrusions.

Mineralogy, temporal and spatial distribution of Mo mineralization in Guilinzheng Mo-W deposit, Jiangnan W mineralization belt and its significance

安徽桂林郑钼钨矿床位于江南钨矿带北部，是目前区内唯一钼储量达到大型的钼钨矿床。本文在对该矿床地质特征和已有成果总结基础上，详细观察了各代表性矿化蚀变样品的岩相学特征，提出该矿床具镁质矽卡岩矿床特征，是桂林郑花岗斑岩熔体与奥陶系白云质灰岩地层交代的产物。矿石类型可分为靠近岩体（<100m）浸染状矿石和远离岩体（>100m）的条带状矿石，分别赋存在接触交代矽卡岩和层控矽卡岩中。桂林郑矿床的矿石矿物为富钼白钨矿（钼钙矿-白钨矿系列），可分为三个世代，分别形成于无水矽卡岩阶段（Sch-I）和含水矽卡岩-氧化物阶段（Sch-II和Sch-III），辉钼矿仅在浸染状矿石富钼白钨矿（Sch-III）边部少量发育。不同矿石类型、不同世代富钼白钨矿的电子探针成分分析显示，富钼白钨矿的钼含量（MoO₃%）在5.75%~71.02%之间，均值为46.00%（n=224），总体具有超常富钼的特点；从无水矽卡岩阶段到含水矽卡岩-氧化物阶段（早→晚）、从浅部的条带状矿石到深部的浸染状矿石（浅→深），富钼白钨矿MoO₃含量有降低趋势。桂林郑钼钨矿床是首个以富钼白钨矿为主要矿石矿物的钼-多金属矿床，这一特殊钼钨矿床的发现深化了矽卡岩钼钨矿床的成因认识，同时对江南钨矿带内区域成矿规律与找矿勘探工作的推进提供了依据。;The Guilinzheng Mo-W deposit is located in the northern sector of the Jiangnan W mineralization belt (JWB), which is the largest molybdenum-poly-metallic deposit in JWB at present. Based on the understanding of the geological background and previous studies of the Guilinzheng Mo-W deposit, the authors systematically observed the petrographic characteristics of various mineralization and alteration samples, which showed that it is a Mg-rich skarn deposit. This deposit was formed by metasomatism between the Guilingzheng granite porphyry melt and Ordovician dolomitic limestones. It can be classified as disseminated and banded ore types, which occur in the contact metasomatic skarn (<100m to the granite porphyry) and strata bound skarn (>100m to the granite porphyry), respectively. The main ore mineral is Mo-rich scheelite (powellite-scheelite series), which can be subdivided into 3 stages in order:the first-stage Mo-rich scheelite (Sch-I) was formed during anhydrous skarnization; the two later ones (Sch-II and Sch-III) were both formed during hydrous skarnization. There are some molybdenite occurring in the edges and gaps of the Sch-III grains. The EPMA results of those different types Mo-rich scheelite showed that the MoO₃ contents varied from 5.75% to 71.02%, with an average value of 46.00% (n=224), indicating an extremely high-Mo ore mineral. Decreasing MoO₃ contents of Mo rich scheelite in Guilinzheng deposit is observed from shallow banded ore to deep disseminated ore spatially, and from early anhydrous skarn stage to late hydrous skarn stage temporally. Guilinzheng Mo-W deposit is the firstly reported Mo deposit with Mo-rich scheelite, instead of molybdenite as the main ore mineral. Systematic studies of this ore deposit can deepen the genetic understanding of the powellite-scheelite mineralization and promote researches on the regional metallogeny and prospecting indicators in JWB.

Typomorphic features of placer gold from the Bystrinsky ore field with Fe-Cu-Au skarn and Mo-Cu-Au porphyry mineralization (Eastern Transbaikalia, Russia)

Eastern Transbaikalia is one of the oldest gold-producing regions in Siberia, and for over 300 years it has been the largest source of the most important raw minerals in Russia. A large number of gold, gold-bearing complex, antimony, mercury and other mineral deposits are known within this region. The orogenic, intrusion-related, and epithermal deposits are important in the balance of gold reserves and gold production. Au-Cu-Fe-skarn deposits are located mainly in the northeastern and southeastern parts of the area, wherein the skarn Kultuma, Lugokan, and skarn- porphyry Bystrinsky deposits are the largest deposits.Herein, we studied the the Bystraya River gold placers and tributaries, which are located to the east of the Bystrinsky massif near the Bystrinsky deposit. In this study, a microchemical characterization technique was applied to gold grains to facilitate the classification of alluvial gold localities in terms of the style or styles of source mineralization, thereby permitting a comprehensive interpretation of regional gold mineralization. In total, 55 samples were collected from four placers and processed for more than 1500 analyses of the native gold.In the alluvial placers of the Bystrinsky deposit areas, weakly rounded native gold either prevails or is significantly present. A low portion of supergenically transformed of gold grains in the placers indicates that the placers formed directly from endogenous gold mineralization. The native gold from the Bystraya River catchment can be divided into 3 types and 1 subtype: (1) Cu-bearing gold grains with a fineness of 800 − 995‰, and a copper impurity of up to 0.73%; (2) Hg-bearing gold grains with a fineness of 800 − 995‰, and an impurity of Hg up to 4.68%; (2.1) Hg-poor gold grains with a fineness of 800 − 995‰, containing the same mineral microinclusions assemblages as the Type 2 gold grains; and (3) gold with a fineness of 400 − 770‰, containing up to 8.5% Hg.The distinguished types of gold grains are manifested to varying degrees at the Bystraya, Left, and Right placers. At at the Yakovlevsky placer, there is no Hg-bearing low fineness and poorly occurring Cu-bearing native gold. Comparing of the obtained data with gold grain composition data from the hypogene deposits allows us to infer bedrock sources. The Cu-bearing high-fineness type of placer gold can be compared with the Cu-bearing native gold of the Bystrinsky, Lugokan, and Kultuma deposits. Hg-bearing low-fineness placer gold grains related to erosion of the Au-bearing base metal mineralization occurred at the Novoshirokinsky and Kultuma deposits. However, Hg-bearing high-fineness gold grains, which most widely occurring in the studied placers, are absent in the in-situ mineralization. Therefore, we suppose that the bedrock source of this gold grain type is linked to the completely eroded upper levels of the Bystrinsky deposit. Thus, our study shows that it is possible to speculate on the nature of eroded material from the gold particle signature. Hense, this generic approach informs regional metallogeny in a way that even detailed field-based classical geology/geochemistry cannot.

Mineral deposits of Latin America and the Caribbean. Preface

The region that encompasses Latin America and the Caribbean is a preferential destination for mining and mineral exploration, according to the Mineral Commodity Summaries 2020 of the US Geological Survey (https://www.usgs.gov/centers/nmic/). The region contains important resources of copper, gold, silver, nickel, cobalt, iron, niobium, aluminum, zinc, lead, tin, lithium, chromium, and other metals. For example, Chile is the world’s largest copper producer and the second largest lithium producer. Brazil is the world’s leading niobium producer, the second largest producer of iron ore, and the third-ranked producer of tantalum. Cuba contains some of the largest reserves of nickel and cobalt in the world, associated with lateritic Ni-Co deposits. Mexico is traditionally the largest silver producer and contains the two largest mines in this commodity and, along with Peru, Chile, Bolivia and Argentina, accounts for more than half of the total amount of global silver production. The region also hosts several world-class gold mines (e.g., Pueblo Viejo in the Dominican Republic, Paracotu in Brazil, Veladero in Argentina, and Yanacocha in Peru). Also, Bolivia and Brazil are among the world’s leading producers of tin. The region hosts a variety of deposit types, among which the most outstanding are porphyry copper and epithermal precious metal, bauxite and lateritic nickel, lateritic iron ore from banded iron-formation, iron-oxide-copper-gold (IOCG), sulfide skarn, volcanogenic massive sulfide (VMS), Mississippi Valley type (MVT), primary and weathering-related Nb-bearing minerals associated with alkaline–carbonatite complexes, tin–antimony polymetallic veins, and ophiolitic chromite. This special issue on Mineral Deposits of Latin America and the Caribbean in the Boletín de la Sociedad Geológica Mexicana contains nineteen papers. Contributions describe mineral deposits from Mexico, Panama, Cuba, Dominican Republic, Colombia, Venezuela, Ecuador, Chile, and Argentina. This volume of papers covers four mineral systems (mafic-ultramafic orthomagmatic mineral systems, porphyry-skarn-epithermal mineral systems, iron oxide copper-gold mineral systems, and surficial mineral systems). This special issue also includes papers on industrial minerals, techniques for ore discovery (predictive modelling of mineral exploration using GIS), regional metallogeny and mining history.

Mineral deposits of Latin America and the Caribbean. Preface

The region that encompasses Latin America and the Caribbean is a preferential destination for mining and mineral exploration, according to the Mineral Commodity Summaries 2020 of the US Geological Survey (https://www.usgs.gov/centers/nmic/). The region contains important resources of copper, gold, silver, nickel, cobalt, iron, niobium, aluminum, zinc, lead, tin, lithium, chromium, and other metals. For example, Chile is the world’s largest copper producer and the second largest lithium producer. Brazil is the world’s leading niobium producer, the second largest producer of iron ore, and the third-ranked producer of tantalum. Cuba contains some of the largest reserves of nickel and cobalt in the world, associated with lateritic Ni-Co deposits. Mexico is traditionally the largest silver producer and contains the two largest mines in this commodity and, along with Peru, Chile, Bolivia and Argentina, accounts for more than half of the total amount of global silver production. The region also hosts several world-class gold mines (e.g., Pueblo Viejo in the Dominican Republic, Paracotu in Brazil, Veladero in Argentina, and Yanacocha in Peru). Also, Bolivia and Brazil are among the world’s leading producers of tin. The region hosts a variety of deposit types, among which the most outstanding are porphyry copper and epithermal precious metal, bauxite and lateritic nickel, lateritic iron ore from banded iron-formation, iron-oxide-copper-gold (IOCG), sulfide skarn, volcanogenic massive sulfide (VMS), Mississippi Valley type (MVT), primary and weathering-related Nb-bearing minerals associated with alkaline–carbonatite complexes, tin–antimony polymetallic veins, and ophiolitic chromite. This special issue on Mineral Deposits of Latin America and the Caribbean in the Boletín de la Sociedad Geológica Mexicana contains nineteen papers. Contributions describe mineral deposits from Mexico, Panama, Cuba, Dominican Republic, Colombia, Venezuela, Ecuador, Chile, and Argentina. This volume of papers covers four mineral systems (mafic-ultramafic orthomagmatic mineral systems, porphyry-skarn-epithermal mineral systems, iron oxide copper-gold mineral systems, and surficial mineral systems). This special issue also includes papers on industrial minerals, techniques for ore discovery (predictive modelling of mineral exploration using GIS), regional metallogeny and mining history.