The Taqian–Zhuxi–Fuchun metallogenic belt in northeastern Jiangxi Province contains significant ore deposits that are closely associated with the Gaohushan granites. The Gaohushan granites predominantly consist of two-mica granites and have been dated using zircon U-Pb isotopic dating to be 129.4 ± 1.9 Ma (MSWD = 3.8). These granites have high SiO₂, ranging from 73.79% to 76.04% and low CaO and MgO contents (ranging from 0.24% to 0.59% and from 0.03% to 0.1%, respectively). The Gaohushan granites also exhibit high FeO^T/MgO ratios from 9.00 to 27.55 with an average of 17.55. The total alkali contents (Na₂O + K₂O) range from 7.08% to 8.43%, and the K₂O/Na₂O ratios range from 1.07 to 2.00 with an average of 1.47. These rocks are peraluminous series with A/CNK ratios (or ASI index) ranging from 1.19 to 1.47 and an average of 1.30. The Gaohushan granites have low rare earth element (REE) contents (∑REE = 2.33~23.50) with strongly negative Eu anomalies (δEu from 0.02 to 0.32) and a distinctive differentiation between heavy rare earth elements (HREEs) and light rare earth elements (LREEs) (LREE/HREE = 1.99~7.79). The normalized distribution pattern of REE in Gaohushan granite exhibits a right-dipping feature classified A-type; these rocks range from 1.06 to 2.71. The spider diagram shows that these rocks are characterized by depletion of Ba, Th, La, Sr, Nd, and Ti and enrichment of Rb, U, Ta, Nb, and P. The Gaohushan granites are classified as A-type granite and were emplaced during an anorogenic extensional event that occurred in the late Yanshannian period, driven by mantle-derived magma underplating. It is these granites or their analogues that have the potential for hosting tungsten, tin, niobium, and tantalum deposits, making them a promising target for mineral exploration. Full article

Large-scale Mesozoic granitoids are exposed in the Greater Khingan Mountains. Their relationship with the Mongolia–Okhotsk and the Paleo-Pacific Ocean is still under discussion and a matter of debate. In this study, field observations were made and a total of 18 granitoids exposed in the vicinity of the Heihe–Baishilazi area in the northern part of the Greater Khingan Mountains were sampled for petrological, geochronological, and geochemical research. In addition, to complement this study, 90 granitic samples from the Xinghua, Dajinshan, Yili, Chabaqi, and Sankuanggou areas in the Greater Khingan Mountains were compiled in order to reveal rock assemblages, magma sources, and then inquire into the tectonic background. Zircon LA–ICP–MS U–Pb dating indicates that two samples from the Heihe area were formed in the Early Jurassic period (194.2 ± 1.4 Ma and 183.1 ± 1.3 Ma), and the εHf(t) values and TDM₂ of the zircons were mainly +5.8 to +10.7 and 528 Ma to 834 Ma, respectively, with a large variation range. The intrusive rocks from the Greater Khingan Mountains (108 in total) belonging to the T₁T₂G₁G₂ assemblage contained tonalites (T₁), trondhjemites (T₂), granodiorites (G₁), and granites (G₂). These granitoids are presented as subalkaline series in a plot of total alkali versus SiO₂ (TAS diagram), medium-K calc-alkaline and high-K calc-alkaline series on SiO₂ versus K₂O diagram, with metaluminous to peraluminous characteristics on an A/CNK versus A/NK diagram. These are shown as a MA (magnesium andesite) series and LMA (lower (or non) magnesium andesite) series on a SiO₂ versus MgO diagram, which can be further divided into the higher-pressure TTG subtype of the MA (corresponding to high-SiO₂ adakite (HSA)) series and the lower-pressure TTG subtype of LMA (corresponding to typical calc-alkaline suprasubduction zone rocks). In addition, granitoids were enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depleted in heavy rare earth elements (HREEs) and high-field-strength elements (HFSEs), corroborating a suprasubduction zone environment. Regional correlations as well as geochemical characteristics indicate that the rocks from the Greater Khingan Mountains formed in a subduction zone environment during the Early Jurassic; primary magma had presumably originated from the melting of young and hot oceanic crust under eclogite to amphibolite facies conditions. According to the spatial variation in rock assemblages (T₁T₂G₁ to G₁G₂ and G₂), we speculate that the northeastern Heihe, Baishilazi, and Xinghua areas as well as the westward Dajinshan area were adjacent to the ocean and formed an outer subduction zone, whereas the southwestward Sankuanggou, Yili, and Chabaqi areas were adjacent to the continent, forming an inner subduction zone. The distribution sites of the inner and outer subduction zones indicate southward and southwestward ocean subduction. Therefore, we propose a direct connection with southward subduction of the Mongolia–Okhotsk Ocean. Full article

Several gold ore-concentrated areas have been recognized in the destruction zone of the North China Craton (NCC). However, the deposits in the western part of the destruction zone have received less attention. Miaoan, a typical Au-polymetallic deposit in the northern Taihang Mountain, provides a good sample for deepening our understanding of the genesis of gold deposits in the western destruction zone. In this study, detailed ore geology, pyrite Rb-Sr age, trace element and S-C-O isotopes of Au-bearing ores were conducted to constrain the source of ore-forming materials and their tectonic setting. The pyrites obtain an Rb-Sr isochron age of 129.5 ± 2.5 Ma, consistent with those of magmatic rocks in this deposit, suggesting their genetic relationship. The δ³⁴S values ranging from −5.5‰ to 1.6‰ and the high Co/Ni and Y/Ho ratios of pyrites indicate the mantle-crust mixing characteristics of ore-forming fluids. The δ¹³C (−6.3‰ to −2.0‰) and δ¹⁸O (9.3‰ to 17.6‰) values of Au-bearing ores and calcites suggest mixing characteristics as well. Geochronologically, the Miaoan Au-polymetallic deposit was formed during the destruction of the NCC. We propose that the Miaoan Au-polymetallic deposit is a decratonic gold deposit and that its ore-forming materials have a mixed source of mantle and crust. Full article

As an important part of the northern Huaiyang tectonic belt, the Mesozoic Xiaotian basin hosts a series of gold and alunite deposits. However, the ages of these deposits remain unclear, constraining the further understanding of the genesis of these deposits. In this work, zircon LA–ICP-MS and alunite ³⁹Ar/⁴⁰Ar isotopic dating studies were carried out on the andesitic porphyrite and alunite of the Saozhouhe alunite deposit, respectively. LA–ICP-MS zircon U–Pb dating for the Saozhouhe andesitic porphyrite yields a weighted average age of 122.8 ± 0.9 Ma (MSWD = 1.8), indicating that these volcanic rocks were formed in the Early Cretaceous period. The alunite 39Ar/40Ar dating yields a plateau age of 121.0 ± 1.1 Ma (MSWD = 4.4) and an isochron age of 121.2 ±1.9 Ma (MSWD = 8.5), indicating that the alunite was also formed in the Early Cretaceous period. Our finding confirms that the formation of the Saozhouhe alunite deposit is genetically related to the Cretaceous volcanic magmatism, which has great significance in the metallogenetic regularity of and further ore prospecting in the Xiaotian basin. Full article

The cassiterite–sulfide mineralization occurs within quartz veins and greisenized Precambrian Older Granite around the Gindi Akwati region at the Ropp complex’s western boundary, north-central Nigeria. The intrusion of Jurassic Younger granite porphyry sheared the marginal parts of the Older Granite and the mylonitized zone created pathways for fluids that escaped during the late-stage consolidation of Jurassic biotite granite. The biotite granites are highly differentiated (K/Rb < 200), peraluminous (A/CNK > 1), high-K, and have high Sn concentrations (average = 117 ppm). The intrusion of Jurassic granite porphyry forced Older Granite interaction with ore-bearing fluid that escaped from Jurassic biotite granite under low oxygen fugacity at or below the NNO buffer. The above fluid–rock interaction caused mass changes in host granite during greisenization and redistributed ores in the vicinity of the shears. This suggests that chloride ions take the form of significant complex-forming ligands and efficiently sequestrate, transport, and deposit ore metals (Sn, Zn, Fe, and Cu) locally within the greisenized granites and quartz veins. The redox potential of the ores probably gave a false impression of metal zoning with a relatively higher abundance of the oxide ore than the sulfides at the surface. The alteration mineralogy (quartz-, topaz-, lepidolite-, and fluorite-bearing assemblages) coupled with S isotope and fluid inclusion systematic data suggests the hydrothermal history of “greisens” and veins started with hot (homogenization temperature ≥300 °C), low to moderate salinity (average = 4.08 wt. % NaCl), low density (≤0.6 g/cm³) fluids and ≥ 200 bar trapping pressure. The sulfide isotopic composition (δ³⁴S_V-CDT = −1.30 to + 0.87 ‰) is very similar to typical magmatic fluids, indicating late-magmatic to early post-magmatic models of mineralization related to the anorogenic granite intrusions. Full article

The Dahutang tungsten deposit is one of the largest deposits in the Jiangnan tungsten belt. The Jiningian pluton is widely distributed in the orefield, which is considered an ore-bearing wall rock and Ca source for scheelite mineralization. The Jiningian granodiorite samples near ore have high W contents (average 93 ppm). Moreover, their SiO₂ and P₂O₅ contents are positively correlated in Harker diagrams, and the A/CNK values vary between 1.18–1.71, suggesting that the Jiningian granodiorite is high fractionated S-type granites and has the potential for W mineralization. The zircon U-Pb ages of the Jiningian granodiorite samples (17SWD-1, 17SWD-2) are 845 ± 21 Ma (MSWD = 1.7) and 828.7 ± 7.5 Ma (MSWD = 1.0), respectively, representing the formation ages of the Jiningian pluton. The U-Pb age of hydrothermal zircons (~140 Ma) in the Jiningian granodiorite samples is consistent with the mineralization age (150–139 Ma), indicating the strong superimposed modification of the Yanshanian mineralizing fluids. The positive correlation between Ca and W molarity in the Jiningian granodiorite samples demonstrates that they provide considerable Ca and W during Yanshanian mineralization. The W activation migration due to sodium alteration can be inferred from the inverse correlation between Na and W molarity. The study tries to provide a new perspective on the origin of mineralized material in the world-class Dahutang tungsten deposit. Full article

The Tianshui-Sunjiaxia area is located in the connection zone of West Qinling Orogen and North Qilian Orogen, which could provide great insights into the amalgamation processes between the northern and southern blocks of China. Three subduction- and rift-related rocks gneissic granite from North Qilian arc-interarc belt (NQAI) granite and metabasalt from North Qinling back-arc basin (NQBA) are distinguished across the connection zone. The gneissic granite was generated by melts from older crustal materials of Longshan Group with the addition of a relatively juvenile basaltic source from the lower crust during the collision process. The Liwanxincun metabasalt reflects the mixing of the partial melting of the shallow asthenospheric mantle and the metasomatized mantle in a back-arc extension setting. The LA-ICP-MS zircon U-Pb dating of gneissic granite (068, 069) yields crystallization ages of 457.0 ± 1.6 Ma and 445.9 ± 2.1 Ma. The study area is divided into six tectonic units in Early Paleozoic time involving NQAI (Yanjiadian-Xinjie) continental arc, interarc rift basin (Maojiamo-Xiwali), continental arc (Chenjiahe-Wangjiacha); NQBA back-arc rift basin (Huluhe-Hongtubao), island arc and ophiolitic melange belt (North Qinling-Shangdan). A tectonic model is proposed in which the NQAI continental arc (Yanjiadian-Xinjie) might represent the early period of subduction of North Qilian Ocean (NQO) and the interarc rift is the product of the extension triggered by southward subduction of NQO. The ongoing subduction of NQO then leads to the formation of Chenjiahe-Wangjiacha continental arc, as well as the Hongtubao back-arc spreading ridge in NQBA back-arc basin (Huluhe). The tectonic evolution of the connection zone is closely associated with the closure of the North Qilian Ocean and North Qinling-Shangdan Ocean in the context of the convergence process of micro-continental blocks, including North China block, Longshan group and North Qinling Terrane. Full article

The Fanchang volcanic basin (FVB) is located in the Middle and Lower Yangtze Metallogenic Belt (MLYMB) between the ore districts of Ningwu and Tongling. The existing ore deposits in the FVB are relatively small in scale and related to late Mesozoic A-type granites. In this paper, the crystallization age, major and trace element composition, and Sr-Nd and Hf isotope compositions of the A-type granites are summarized from the literature; in addition, the magnetite composition, H and O isotopes of fluid inclusions, and sulfur isotope composition of metal sulfides in some typical ore deposits in the FVB are also summarized to give insights into the petrogenesis and mineralization of the A-type granites intruding into the FVB. The results show that: (1) Orthopyroxene, plagioclase, K-feldspar, and biotite are the main fractionating minerals controlling the evolution of the magmas of A-type granites in the FVB and other areas in the MLYMB. (2) The whole-rock Sr-Nd and zircon Hf isotopic characteristics show that the source of A-type granite magma is complex and includes the enriched mantle, lower crust, and upper crust, probably with stronger participation of Archaean–Paleoproterozoic crustal materials in the FVB granites than in other regions of the MLYMB. (3) The ores in the FVB are dominated by skarn and hydrothermal deposits. H and O isotopes of fluid inclusions indicate that ore-forming fluids have been derived from mixtures of magmatic hydrothermal fluid, meteoric waters, and deep brine related to gypsum layers. S isotopes of metal sulfides indicate that the sulfur may be a mixture of magmatically derived sulfur and sulfur originating from the Triassic gypsum-bearing layers. The deposit and ore characteristics of the main deposits in the FVB are also illustrated, and the evaluation of metal resources indicates that the skarn and hydrothermal iron–zinc ores in the FVB also have potential as sources of Cd, Ga, and Se. In addition, in terms of the oxygen fugacity, rock type, and geochemical characteristics of magmatic rocks, the metallogenic characteristics and potential of the A-type granites in the FVB are evaluated. It is considered that in addition to the dominant constituents of iron and zinc and the minor constituents listed above, the FVB could have the potential for providing copper, gold, molybdenum, uranium, and other metals as well. Full article