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[Display omitted] • REE mineralization in the Lala deposit primarily formed at ca. 850 Ma. • The host rocks and contemporaneous felsic magmatic rocks serve as the primary sources of REE metallogenic materials. • Na, CO 2 , and F-rich magmatic waters aid REE mineralization, mixing with meteoric waters, leaching the REE from host rocks and early ores. The Lala deposit in the Kangdian metallogenic province is one of the most important iron oxide copper–gold (IOCG) deposits in South China. Rare earth element (REE) activation, migration, and redistribution occurred during late-stage Cu mineralization in the deposit. However, the geological characteristics of REE mineralization and the genetic mechanism of this deposit remain poorly understood. The goal of this study was to investigate REE mineralization and the ore-forming process in the Lala deposit by employing a comprehensive approach that included techniques in petrography, mineralogy, and geochemistry. Mineralogical analysis indicated that the REE-bearing minerals in this deposit include bastnäsite, monazite, parisite, xenotime, apatite, and fluorite. Apatite was observed to have high concentrations of REE (ΣREE ranging from 7,409 to 18,739 ppm). The results of U-Pb isotope dating of bastnäsite and xenotime suggest that the REE mineralization in the Lala deposit primarily formed at ca. 850 Ma, aligning with the Neoproterozoic magmatism in this region. The chondrite-normalized REE pattern of apatite is similar to that of host rocks and contemporaneous magmatic rocks; the ε Nd(t) values of bastnäsite and xenotime (calculated at ca. 850 Ma) ranged from −12.2 to −7.0, which is comparable to the values obtained for contemporaneous country rock (−8.7 to −6.4) and felsic intrusive rocks (−9.6 to 4.4). This similarity indicates that the host rocks and contemporaneous felsic magmatic rocks serve as the primary sources of REE metallogenic materials. The ∼ 850 Ma REE mineralization overprints the early stage Fe-Cu mineralization and is associated with a Neoproterozoic magmatic event. During this process, Na, CO 2 , and F-rich magmatic water mixes with meteoric water and leaches REE from host rocks and early-stage ores. Under the disintegration of REEs, F-complex in hydrothermal fluids, REE minerals (e.g., monazite, bastnäsite, parisite, and xenotime) precipitate together with apatite and fluorite in the Fe-Cu ores. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two hydrothermal mineralization events in this deposit are identified: quartz-sericite-pyrite-native gold (I) stage and chlorite-quartz-sericite-chalcopyrite-electrum (stage II). • This study provides additional age constraints on the host rocks (Caledonian granitic rocks) in the Hebaoshan area, with ages ranging from 441 to 446 Ma, as well as two mineralization events at approximately 238.46 ± 2.01 Ma and 179.54 ± 7.28 Ma. • The combination of ages and geological evidence suggests that the first mineralization event is associated with the intracontinental orogeny of the Yangtze Block and Cathaysia Block, as well as the flat subduction of the Paleo-Pacific Plate. The second mineralization event is related to the extensional tectonic activity following the collision between the Yangtze Block and Huaxia Block. The Hebaoshan gold deposit (41.5 t Au @ 3.5 g/t) is located in the southeastern region of the South China Block, central part of the Wuyishan metallogenic belt. The ore-hosting rocks in this area are predominantly Precambrian metasedimentary rocks and Caledonian granitic rocks. Two hydrothermal mineralization stages can be distinguished: a quartz-sericite-pyrite-native gold (stage I) and a chlorite-quartz-sericite-chalcopyrite-electrum (stage II), with hydrothermal monazite and rutile are firstly identified in separate stages. The complex geological history of the region has resulted in ongoing debates regarding the age of gold mineralization and the genesis of the major gold deposits in this area. In order to precisely constrain the mineralization age of the deposit and further establish a genetic model for the ore deposit, LA-ICP-MS U-Pb dating and trace element analysis on accessory minerals were conducted. Based on the textures mineral assemblages, and geochemical features of the accessory minerals, magmatic apatite, hydrothermal rutile, and both magmatic and hydrothermal monazite were identified. The U-Pb ages of magmatic apatite and monazite are determined to be 445.3 ± 15.80, 441.3 ± 15.10 Ma and 446.57 ± 1.03 Ma, respectively, suggesting that these ages represent the emplacement ages of the Caledonian intrusive rocks. The ages of hydrothermal monazite and hydrothermal rutile are determined to be 238.46 ± 2.01 Ma (single-mineral analysis), 238.46 ± 2.01 Ma (in-suit analysis) and 179.54 ± 7.28 Ma, respectively, suggesting that represent two mineralization events during the Late Triassic to early Jurassic in the Hebaoshan area. These data provide new constraints on the mineralization process in the Hebaoshan deposit and excludes the link between gold mineralization and the intrusion of the Caledonian granites. Regionally, It is speculated that the two mineralization events at Hebaoshan are respectively associated with intracontinental orogenic movements between the Yangtze Block and Cathaysia Block, the flat-slab subduction of the Paleo-Pacific Plate (stage I), and the subsequent extensional tectonics related to the collision between the Yangtze Block and Cathaysia Block (stage II). Our study indicates that the timing of multiple episodic mineralization can be constrained by analysis of accessory minerals, which provides a geological basis for better genetic model for the deposit and provide geological evidence for unraveling the relationships between magmatic activities and mineralization events in the region. [ABSTRACT FROM AUTHOR]

Representative CL images showing the texture of the Yangla scheelite and corresponding variations in the REE patterns throughout the evolution of the oreforming fluids. [Display omitted] • Three types of scheelite are identified based on their microstructure. • Tungsten mineralization age is significantly later than the Triassic Cu mineralization in the Yangla district. • Source and evolution ore-forming fluids were constrained by scheelite texture and geochemistry. The Yangla Cu-polymetallic deposit is the largest skarn Cu deposit in the Jinshajiang suture zone. Recently, an new W orebody was identified in the depths of the Cu orebodies. However, the genetic relationship between W and Cu orebodies, along with the tungsten ore-forming processes, remains unclear. This study delves into the careful investigation of three types of scheelites focusing on microstructure, trace element compositions and Sr isotope geochemistry. The aim is to elucidate the source and evolution of ore-forming fluids and ore genesis in the multi-episodic metallogenic systems. Primary scheelite (Sch-I) generally displays oscillatory zoning in CL images with the lowest REE (3.8–142 ppm) and highest Sr (604–1480 ppm) contents. Secondary scheelite (Sch-III), commonly precipitated as overprinting rims on primary crystal, has the highest REE (145–1071 ppm) and lowest Sr (376–793 ppm) contents. In contrast, Sch-II represents a transitional stage from primary to secondary, with REE and Sr contents at intermediate levels. Sch-I is characterized by LREE enrichment and a positive Eu anomaly in the chondrite-normalized REE patterns, whereas Sch-III shows MREE-rich patterns with a weak positive Eu anomaly. Scheelite U-Pb dating (30.3 ± 1.5 Ma) indicates that the W mineralization is not genetically related to Triassic granitoids in the Yangla district. Instead, it is likely associated with magmatic activities and tectono-thermal events in the Jinshajiang fault zone during the Cenozoic. The high initial 87Sr/86Sr ratios (0.71771–0.72229) in the scheelite, significantly higher than those of Triassic granites and ore-hosting marble, suggest that the geochemical features of Sch-I are inherited from the parental ore-forming fluids. These fluids are likely derived from the mixed hydrothermal fluids involved by the Neoproterozoic strata and/or concealed magmatism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hongqiling Sn-W polymetallic deposit is a product of granitic magmatism in Late Jurassic. • The elemental composition of primary cassiterite is controlled by the compositions of ore-forming fluid and the rate of crystallization. Hongqiling deposit is one of the most typical hydrothermal vein type Sn-W polymetallic deposits in the Dongpo ore field, southern Hunan. It is an ideal object to study the Sn-W mineralization in the Nanling metallogenic belt and even in the whole South China Block, and to reveal the regional metallogenetic regularity. Based on the detailed investigation of the deposit geology, this paper discusses the mineralization age and processes of the Hongqiling hydrothermal vein type Sn-W polymetallic deposit by LA-MC-ICP-MS in-situ U-Pb dating and trace element geochemistry of cassiterite from the quartz vein type Sn-W ore body. Cathodoluminescence (CL) imaging shows that cassiterite in Hongqiling deposit can be divided into two generations. primary cassiterite (Cst-I) and altered cassiterite (Cst-II). The LA-MC-ICP-MS in-situ U-Pb age of the two groups of Cst-I samples are 158.9 ± 0.7 Ma and 158.4 ± 0.8 Ma, respectively, which are well consistent with the mineralization ages of most Sn-W deposits in the Nanling metallogenic belt, and are also consistent with the ages of middle to late Jurassic magmatic activity represented by the Qianlishan intrusion. This indicates that the Hongqiling deposit, like many Sn-W deposits in the Nanling metallogenic belt, is genetically related to the regional Middle to Late Jurassic granitic magmatic activities. LA-ICP-MS trace element analysis shows that trace elements such as Na and Cs are mainly distributed in fluid inclusions in cassiterite, while the major elements such as Mg, Al, and Si are mainly distributed in the mineral inclusions, and other elements such as W, U, Zr, Hf and Ti are mainly distributed in the cassiterite by isomorphic substitution. The high Fe and W contents in both primary and altered cassiterite indicate that the ore-forming fluid of Hongqiling deposit is mainly derived from granitic magma. The fluctuating variation of Fe, V, Sc, Ti, Zr, Hf, Nb and Ta in the primary cassiterite with the crystalline bands indicates that there are two large-scale pulses of magmatic hydrothermal fluid during the mineralization process, while the altered cassiterite is relatively depleted of Ti, Sc, Zr and U elements, and enriched in Pb which may represent the compositional characteristics of the late-stage fluid. In summary, the Hongqiling hydrothermal vein type Sn-W polymetallic deposit was formed by the pulsating exsolution of magmatic hydrothermal fluid of late Jurassic granitic magmatism. The trace elemental compositions of primary cassiterite are generally controlled by the compositions of ore-forming fluid and the rate of crystallization. [ABSTRACT FROM AUTHOR]

Schematic diagram of textural characteristics, formation process and hydrothermal spatial evolution of garnets at different locations in the Huanggangliang Fe-Sn deposit. [Display omitted] • U-Pb dating of garnet constrains the onset of hydrothermal activity and the formation of skarn. • The hydrothermal physicochemical conditions of the Huanggangliang garnets are constrained. • Garnet trace elements are important in distinguishing different mineralization conditions. • Tin-rich garnet can be used as an indicator mineral for exploration of skarn-type tin deposits. Cu-Fe (Au), W-Sn (Mo), Pb-Zn (Ag) and other element assemblages are common in many skarn deposits, but examples of Fe and Sn coexistence in nature are relatively rare. The Huanggangliang deposit in the southern Great Xing'an Range is the largest Fe-Sn polymetallic deposit in northern China, and there are five main mining areas (SK Ⅰ–SK Ⅴ) distributed along a SW–NE trend. SK Ⅰ and SK Ⅲ are the two larger mining areas in the Huanggangliang deposit, and their mineral assemblages and wall-rocks are significantly different: cassiterite and metal sulfides are duncommon in SK Ⅰ (andesite), while they are widely distributed in SK Ⅲ (marble). Garnet is widely distributed in SK Ⅰ and SK Ⅲ mining areas, and provides a good opportunity to explore the mechanism of Fe-Sn assemblage differentiation. Three types of garnet are distinguishable (Grt 1, Grt 2 and Grt 3) based on their mineral associations, textures and locations, and they mainly belong to the andradite-grossular solid solution series. The LA–ICP–MS U-Pb ages of the garnets from SK Ⅰ and SK Ⅲ are 136.0 ± 1.2 Ma (n = 25, MSWD = 1.9) and 136.2 ± 2.6 Ma (n = 37, MSWD = 1.8), respectively, suggesting that magmatic-hydrothermal activity in these two mining areas began at the same time. Grt 1 (located deep in SK Ⅰ and SK Ⅲ) and Grt 2 (located shallowly in SK Ⅰ) are mainly andradite, while Grt 3 (located shallowly in SK Ⅲ) is mainly grossular. They are all enriched in high field strength elements (HFSEs) and depleted in large ion lithophile elements (LILEs), and their REE patterns are enriched in light rare earth elements (LREEs) and depleted in heavy rare earth elements (HREEs). However, Grt Ⅰ-1a and 1b (deep garnets in SK Ⅰ) exhibit obvious positive Eu anomalies, while the other garnet types exhibit negative or no obvious Eu anomalies. Additionally, Grt 3 has high contents of V, Sn, U, Th, Zn and Y, and low contents of W and Mo. This pattern implies that the garnets in deep SK Ⅰ may have formed under oxidizing conditions with high temperatures, high oxygen fugacity (f O 2) and weak acidity, while the garnets in shallow SK Ⅲ formed under reducing conditions with moderate temperatures, moderate f O 2 and near-neutral pH. The garnets in shallow SK Ⅰ and deep SK Ⅲ may have formed under weak oxidation–reduction conditions at moderate to high temperatures, moderate f O 2 and weakly acidic to neutral pH conditions. Our newly reported field geological, mineralogical, and geochemical data from garnet suggest that the ore-forming fluids of the Huanggangliang were magmatic-hydrothermal fluids mixed with slightly acidic external fluids, chloride complexes may have been the main transport ligands of REEs. The metallogenic environment may be an important factor leading to the difference of mineral assemblages in the Huanggangliang deposit. [ABSTRACT FROM AUTHOR]

The subduction of the Pacific Plate led to asthenospheric upwelling and thus partial melting of the metasomatized mantle occurred. The REE-bearing initial alkaline magmas were evolved to generate the subsequent exsolution of carbonate melts and REE-rich hydrothermal fluids which existed at relatively shallow depth. Notably, two kinds of REE mineralization occur in the Weishan REE deposit: 1) quartz–barite–carbonate vein type and 2) disseminated and veinlet type. [Display omitted] • Zircon U-Pb dating indicates that the alkaline rocks intruded at ∼ 120 Ma; • Molybdenite Re-Os dating corroborates the mineralization age of ∼ 120 Ma; • Ore-forming magmas were mainly derived from an enriched lithospheric mantle; • Asthenospheric upwelling during craton destruction led to the mantle partial melting. The Weishan REE deposit is one of the largest LREE deposits in China, which is hosted by the Weishan alkaline complex (WSAC) and late Archean gneisses. Two types of mineralization including vein-type and disseminated-type occur in this deposit, of which the former is characterized by large quartz-sulfate-calcite-REE mineral veins cutting all kinds of wallrocks, while the latter is featured by REE minerals disseminated in the alkaline rocks. The vein-type mineralization commonly occurs at shallow depths and has been numerously studied. The disseminated-type mineralization typically occurs at deeper depths, which was newly discovered by drilling exploration and has been poorly studied. In this contribution, zircon U-Pb dating and Hf isotopic analysis as well as whole-rock geochemistry and Sr-Nd isotopic analyses were conducted on the deeply drilled alkaline rocks, combined with molybdenite Re–Os dating on the disseminated ore, with the aim to unravel the petrogenesis of the alkaline rocks and their contributions to the REE mineralization. Zircon U–Pb dating suggests an intrusive age of 119.9 ± 0.9 Ma for the WSAC, which is quite consistent the Re–Os age of 120.0 ± 1.8 Ma for the disseminated ore, corroborating their close genetic correlation. The studied alkaline rocks show enrichment of LILEs, depletion of HFSEs and strong fractionation between LREEs and HREEs, indicating a crustal involvement in the magmas or a metasomatized mantle source. They are characterized by higher Hf (εHf(t) = -6.7 to −12.2) and Nd (εNd(t) = -8.8 to −9.7) isotopic compositions compared with those of the contemporaneous subcontinental lithospheric mantle (SCLM). Based on the above features, it is inferred that the parental magmas of the WSAC were mainly derived from an enriched SCLM with some involvement of asthenospheric mantle-derived materials. The mantle source was likely metasomatized by the subducted Paleo-Pacific oceanic plate, leading to the enrichment of REE and carbonate. Rollback of the oceanic slab during the early Cretaceous resulted in an extensional setting in the study region, which was favorable for partial melting of the metasomatized mantle and thus generated the REE-rich alkaline magmas. [ABSTRACT FROM AUTHOR]

[Display omitted] • Garnet U-Pb dating constrains the age of the Lazhushan deposit at ca. 150 Ma. • Fe skarn mineralization in the Edong district started earlier than previously thought. • The Th/U ratio of garnet is a potential redox indicator of ore fluids. Garnet is ubiquitous in skarn deposits. It is a sensitive recorder of physiochemical conditions and also a powerful geochronometer. In this study, we use garnet trace element geochemistry and U-Pb geochronology as well as sulfur isotopes of sulfides to constrain the age and mineralization process of the Lazhushan Fe skarn deposit. Garnets in the Lazhushan Fe skarn belong to the andradite-grossular solution series and yield a compositional range from Adr 47.2 Gro 50.7 to Adr 97.4 Gro 0.9. There are strong correlations between La N /Yb N ratios and andradite contents in garnet, indicating that garnet major element composition exerts a strong control on the REE fractionation. The decrease of HFSEs (Nb, Ta, Zr, Hf, and Ti) and Co, V, and Mn concentrations from prograde to retrograde garnets may reflect increasing water/rock ratio and decreasing temperature during skarn evolution, respectively. Co-precipitation with magnetite may be responsible for the low concentration of V in the retrograde garnets. The Th/U ratio increase from endoskarn garnet to exoskarn counterparts, probably reflecting an increase of fluid f O 2 due to interactions with evaporate sulfate from the wall rocks. The sulfides in this deposit are enriched in δ34S (up to 13 ‰), conforming the involvement of evaporate sulfate during Fe skarn mineralization. The incursion of evaporate sulfate may have played an important role in magnetite mineralization for the Lazhushan deposit by increasing fluid f O 2 and facilitating the oxidation of Fe2+ to precipitate magnetite. LA-ICP-MS U-Pb dating of garnets from 4 garnet-bearing samples yielded ages of 150.8 ± 6.8 Ma (2σ), 150.9 ± 5.3 Ma (2σ), 150.2 ± 7.9 Ma (2σ), and 150 ± 11 Ma (2σ), which are consistent with zircon weighted mean U–Pb ages of 150.1 ± 2.0 Ma (2σ) and 150.5 ± 1.0 Ma (2σ) of the ore-related intrusion. Combined with previously published metallogenetic ages of skarn deposits in the Edong district, we suggest that the Lazhushan deposit may represent the initiation of Fe skarn mineralization for the Edong district during the Late Mesozoic. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Xiaolonghe and Lailishan Sn deposits in the Tengchong-Lianghe tin belt formed in oceanic subduction and continental collisional settings, respectively. • The Sn-related granitoids from the two deposits have very similar magma sources, melting temperatures, evolution processes, redox states, and volatile contents. • The specific mechanism triggering mantle upwelling could be the most significant difference between the formation of Sn-related granitoids in subduction versus collision processes. Magmatic-hydrothermal Sn deposits can develop in both subduction and collision settings. However, a systematic comparison of the geochemical fingerprints and petrogenetic evolution of Sn-related granitoids from both settings is still lacking. The Tengchong-Lianghe tin belt hosts numerous Sn deposits but of different metallogenic ages, such as the Xiaolonghe and Lailishan Sn deposits, which provide an ideal study area for addressing this issue. Zircon U–Pb dating suggests that the Xiaolonghe and Lailishan Sn-related granitoids were emplaced at 74.2–75.5 and 50.0–51.1 Ma, respectively. Given the initial India-Asia collision commenced at ca. 65–60 Ma, these ages, consistent with available Sn metallogenic ages, suggest the formation of the Xiaolonghe and Lailishan Sn deposits in subduction and collisional settings, respectively. New zircon and apatite compositions, and apatite Sr isotopic data, combined with previously reported whole-rock geochemical results, all indicate that the Xiaolonghe and Lailishan Sn-related granitoids share similar magma sources, evolution processes, redox states, and volatile contents. The presence of hornblende, high apatite Nd N /Nd N * (mostly > 1), and whole-rock evolutionary trends, together indicate that they represent fractionated I-type granites. Distinctly elevated apatite 87Sr/86Sr ratios (0.70988–0.71430) suggest that they originated from an ancient lower crust. Subsequently, they underwent an extensive fractional crystallization dominated by feldspar, as revealed by whole-rock, apatite, and zircon elemental variation trends. The low zircon Ce N /Ce N * (mainly < 200) and ΔFMQ (–1.9 to 1.7), together with elevated apatite F content (2.30–3.69 wt%), reveal that they crystallized from reduced and F-rich magmas. The relatively high whole-rock zircon saturation temperatures (mainly > 800 ℃) and Ba/Pb ratios imply that they were produced at a higher temperature by biotite-dehydration melting, which requires additional heat from the mantle. The specific mechanism that triggers mantle upwelling (oceanic slab subduction or break-off) could be the most significant difference between Sn-related granitoids formed during subduction and collision processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • This study is the first attempt of a systematic horizontal skarn profile in Beiya. • Two types of garnet have been distinguished in endoskarn and exoskarn. • The conditions and compositions of hydrothermal fluid in different environments vary. • The skarn mineralization age is restricted by crystallization age of garnet. Garnet is one of the most typical minerals in skarn deposits, and its texture and composition is a proxy for the changing physicochemical conditions. Thus, mineralogical and geochemical characterization of different garnet types can provide important information on the nature and evolution of ore-forming fluids. The Beiya gold-polymetallic deposit is China's largest skarn-type Au deposit with Au reserves of >380 t. Although several studies have addressed the skarn formation mechanism and nature of fluid evolution, a systematic study on the changes in the composition and texture of garnet from wall rocks to ore-related intrusion has not yet been attempted. In this work, we carry out a systematic investigation along a horizonal profile in the open pit of the Beiya deposit. Our results show that the garnet in the profile belongs to grossular-andradite solid solution series with all grains showing well-developed fine oscillatory zoning. The garnets are of two types: the first type (Grt I) formed within the endoskarn, is reddish to red with euhedral-subhedral megacryst structure (>10 mm) and has altered surfaces. The second type (Grt II) occur in the proximal exoskarn, is red to brown–red, euhedral-subhedral, with medium- to fine- grained structure (0.3–4 mm) and displaying oscillatory zoning. Unlike Grt I, hydrous minerals occur in the pores among Grt II garnets, such as calcite, quartz, epidote and chlorite. Also, calcite-chlorite vein, quartz vein and quartz-chalcopyrite-pyrite vein cuts the Grt II garnets. Grt I is dominantly grossular (Adr 14.88-43.58 Grs 55.25-82.87), depleted in the large ion lithophile elements (LILE), relatively enriched in high field strength elements (HFSEs) and enriched in heavy rare earth elements (HREEs) with negative Eu anomalies. Grt II is mostly andradite (Adr 62.18-98.91 Grs 0-36.22), depleted in the LILE and HFSE, enriched in light rare earth elements (LREEs) with slightly positive Eu anomalies. Here we selected Grt II for in-situ LA-ICP-MS U-Pb dating, since Grt I contains negligible uranium. The results yielded a lower intercept 206Pb/238U age of 35.3 ± 1.8 Ma (MSWD = 0.68, n = 23). The calculated oxygen isotopic compositions of hydrothermal fluids in equilibrium with two types of garnets range from 6.46 ‰ to 8.56 ‰ (average 7.89 ‰), which are within the range of values for magmatic fluids. We infer that the physicochemical conditions of the hydrothermal fluid changed from relatively reduced, nearly neutral, and low water/rock ratios to slightly oxidized, slightly acidic, and high water/rock ratios. The chlorine content in the fluid increased during garnet growth. The fluctuating compositions of garnets in the skarn suggest multistage ore-fluid activities and the fluid evolution provide insights into the ore-forming process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two episodes of garnet and Fe mineralization were identified at Jia'erbasidao Fe deposit. • The 1st garnet generation was formed at 270.6 Ma and skarn related. • The 2nd garnet generation was formed at 248.3–246.0 Ma and skarn related. Over a hundred iron ore occurrences have been discovered in the Chinese Altay Orogenic Belt (AOB), which is a key Fe-ore belt in NW China. In the Jia'erbasidao ore district, Fe skarn mineralization was mainly developed along the contact zone between biotite granite and the marble of Altay Formation, which is different from most Fe mineralization (non-skarn contact zone) in the Chinese AOB. Two generations of garnet (Grt1and Grt2) have been identified to be related to the two stages of Fe-ore formation at Jia'erbasidao, and Grt1 and Grt2 can be further divided into Grt1a, 1b and Grt2a, 2b, respectively. Our U-Pb dating indicates that the biotite granite and garnet from prograde skarn stage 1 (Grt1a) were formed at 275.6 ± 3.1 Ma and 270.6 ± 4.4 Ma, respectively. The mineralized biotite granite is metaluminous to peraluminous, LREE-enriched and HREE-depleted. Meanwhile, two Grt2a samples from the prograde skarn stage 2 yielded lower intercept 206Pb/238U ages of 248.3 ± 2.9 Ma and 246.0 ± 6.0 Ma, respectively. Grt1 and Grt2 may have formed from different ore-forming fluids: Grt1a was precipitated from a LREE-depleted, near neutral and low f O 2 fluid (δEu = 1.92–2.84); Grt1b and magnetite (Mag1) were precipitated from the same fluid with higher f O 2 (δEu = mostly 1.22–2.63); Grt2a was precipitated from a fluid with relative LREE enrichment, relatively lower pH and higher f O 2 (δEu = 0.98–1.69); Grt2b and magnetite (Mag2) was formed from a fluid that was HREE-enriched, near neutral, and higher f O 2 (δEu = 0.76–1.09). Our study shows a two-stage Fe mineralization at Ja'erbasidao, including the Early Permian Fe skarn mineralization and the Early Triassic skarn mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Mazhala Au-Sb deposit in South Tibet was constrained at ca. 35 Ma. • Mazhala apatite belongs to fluorapatite having F contents of 2–4%. • Mazhala apatite is rich in MREE but depleted in LREE- and HREE. • Mazhala apatite have δ18O values in the range of 16-19‰. • The Mazhala Au-Sb deposit was mainly precipitated from metamorphic water. Due to lack of suitable datable minerals, timing of the Mazhala Au-Sb deposit in South Tibet remains unresolved. Also, previous geochemical studies suggest an ambiguous conclusion on the source of ore-forming fluid, with diverse viewpoints of magmatic water, mixed magmatic–meteoric water or mixed metamorphic-meteoric water, respectively. In this study, hydrothermal apatite U-Pb dating constrains the Mazhala Au-Sb deposits to have formed at ca. 35 Ma, consistent with the timing of Eocene leucogranite intrusions in South Tibet. The Mazhala Au-Sb mineralization occurred during the main collision stage to late collision stage in Eocene to Oligocene, and predates the Cuonadong Sn mineralization in South Tibet which occurred during the crustal extension stage in Miocene. An EPMA analysis shows the apatite belongs to fluorapatite that have F contents in the dominant range of 2–4%. The Mazhala apatite displays an overall MREE enrichment and LREE- and HREE depletion distribution pattern with positive Eu anomalies, and have δ18O values dominantly in the range of 16-19‰ with a mean δ18O‰ value of 17.74 ± 0.15‰ (2σ), which suggest a relatively homogenous chemical composition for the ore forming fluids with a relatively stable temperature regime. In combination with previous temperature estimates, the ore forming fluids are inferred to have a dominant δ18O fluid value of 13-16‰, which overlap with metamorphic water. The combined age and geochemical data suggest Eocene leucogranite intrusion induced metamorphic fluid circulation within Paleozoic-Mesozoic metamorphic sedimentary rocks around the study area, which prompted precipitation of fluorapatite together with Au-Sb bearing pyrite and arsenopyrite in the Mazhala Au-Sb deposit. This study puts an emphasis on the contribution of metamorphic water as the dominant ore-forming fluid origin in the Mazhala Au-Sb deposit. In contrast, the close spatial and temporal association of the Cuonadong Sn polymetallic mineralization with the Miocene leucogranite intrusion-induced hydrothermal activity in the Cuonadong dome demonstrates that their genetic links, as was also evidenced by C-H-O-S-Pb isotope data that point to a dominant contritution of Miocene leucogranite to ore-forming fluid and materials for the Cuonadong Sn polymetallic ore deposits. As such, from a perspective of ore-forming model in South Tibet it be seen that during the main collision stage to late collision stage ore-forming fluid and materials were mainly derived from metamorphic water, whereas during the crustal extension stage, ore-forming fluid and materials were dominantly sourced from magmatic water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Origins and ore-forming processes of Fe mineralization were revealed by apatite. • The ore-forming fluids were high-fluorine fluids. • The fluorine promoted iron leaching from wallrocks. • Fluid metasomatism contributed to elevate and lower Fe grade, respectively. Apatite commonly contains abundant halogens and trace elements, which can occur in both the magmatic and hydrothermal stages, becoming favorable for recording the magmatic-hydrothermal properties and processes. Skarn-type iron deposits associated with high-Mg diorites are widespread in the Luxi Block, eastern North China Craton. Their ore-forming processes, especially how the different wallrocks (limestones and dolomites) controlled the formation of high-grade iron ores, have been poorly constrained. To unravel the mechanisms, in this contribution, in-situ textural, geochronological (U-Pb dating) and geochemical (halogens and trace elements) analyses by SEM, EPMA and LA-ICP-MS were conducted on apatite from the representative Fe skarn deposits (Jinling and Zhangjiawa deposits) in the Luxi Block. Three generations of apatite were identified in the Jinling deposit, which occur in the feldspathization (Ap1), garnet–pyroxene skarns (Ap2) and massive magnetite ores (Ap3), respectively. One generation of apatite occurring in the massive magnetite ores (Ap-3) was identified in the Zhangjiawa deposit. The Ap2 and Ap-3 apatite grains show patchy textures composed by residual bright zones (Ap2a and Ap-3a) and newly-formed grey to dark zones (Ap2b and Ap-3b), which indicate fluid metasomatism. LA-ICP-MS U-Pb dating shows that the Ap1, Ap2a and Ap3 apatite in the Jinling deposit formed at 130.4 ± 0.9 Ma (2σ), 128.5 ± 2.4 Ma and 128.3 ± 9.2 Ma, respectively, whereas the Ap-3a in the Zhangjiawa deposit formed at 128.1 ± 4.2 Ma. These ages are well consistent with the intrusive ages of the spatially associated high-Mg diorites within errors, corroborating the ore-forming fluids originating from the high-Mg rocks. All the studied apatite grains show F/Cl ratios higher than 1, especially in the early-stage apatite (e.g., 5–19 in Ap1), indicating that the originally exsolved fluids were enriched in F. The high F contents probably played a significant role in leaching Fe from the high-Mg rocks by enhancing rock porosities. The Eu/Eu* ratios of apatite increase from Ap2a to Ap3 while the Ce/Ce* ratios decrease. This suggests an increase of oxygen fugacity. The Sr concentrations in Ap3 are much higher than those in Ap-3a, correlating well with the wallrocks that limestones are developed in the former while dolomites in the latter. The above features indicate that fluid-rock interaction likely led to the increase of oxygen fugacity, which controlled the massive Fe deposition. In the Jinling deposit, the altered apatite grains (Ap2b) show much lower REE + Y but higher F contents than those of the unaltered (Ap2a), not only indicating the REEs being easily mobilized during metasomatism, but also suggesting that the high F contents likely contributed to the formation of high-grade ores by leaching additional Fe from the previously formed Fe-rich skarns. In the Zhangjiawa deposit, the altered apatite grains (Ap-3b) shows lower Cl contents than those of the unaltered (Ap-3a). This probably indicates the mixing of low-salinity fluids (e.g., recycling meteoric water), leading to the loss of Fe and thus lowering the Fe grade. The above results indicate that metasomatism is common in the skarn deposits, which can either elevate or lower the metal grade. The processes can be well recorded by apatite. [ABSTRACT FROM AUTHOR]

[Display omitted] • The age of Gaolong deposit was defined at 156.8 ± 8.3 Ma for the first time. • Ore-forming materials were leached or derived from the deep continental crust. • Apatite geochemistry was inherited from hydrothermal fluids and governed by complexations. • Fingerprints of hydrothermal apatite in sediment-hosted hydrothermal ore systems. Apatite can record the evolution of magmatic–hydrothermal ore systems, but it is unclear whether it is suitable for investigating low-temperature, sediment-hosted hydrothermal ore systems. To fill the knowledge gap. we investigated the Gaolong Carlin-type Au deposit in the Guangxi Zhuang Autonomous Region, southwestern China (Youjiang Basin). Results show that the hydrothermal apatite occurs in quartz–sulfide ores, has an intact crystal form and homogeneous texture, and is F-rich (2.77–3.67 wt%) and Cl-poor (<0.01 wt%). The apatite is enriched in rare earth elements (REEs; ΣREE = 739–2481 ppm) and has middle-REE-enriched chondrite-normalized REE patterns with positive Eu anomalies (δEu = 1.35–2.00). These REE features were inherited from a reducing hydrothermal system in which anion complexation was dominant. The apatite has high Sr contents (up to 0. 9 wt%) and relatively uniform initial 87Sr/86Sr ratios (0.709055–0.709208), suggesting that Sr was leached or derived from the deep continental crust. In situ U–Pb dating of 156.8 ± 8.3 Ma for apatite shows that the Late Jurassic–Early Cretaceous was an important time for the formation of Carlin-type Au deposits in the Youjiang Basin. The Au mineralization was associated with far-field tectonism and deeply sourced hydrothermal ore-forming fluids. Hydrothermal apatite can be used to fingerprint low-temperature, sediment-hosted hydrothermal ore systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Huanggangliang mineralization may have formed from magmatic-hydrothermal fluids. • U-Pb dating of zircon, cassiterite and garnet provide constraining on the deposit initiations. • The physicochemical conditions of hydrothermal fluids for Huanggangliang deposit cassiterite were constrained. • Cassiterite as a speciation mineral to determine the genesis of tin polymetallic deposits. The Huanggangliang Fe-Sn deposit is located in the southern Da Hinggan Range (NE China), and it's one of the most important deposits within the Huanggangliang-Ganzhuermiao Sn polymetallic metallogenic belt. Nearly 90% of the orebodies (stratiform/lenticular) at Huanggangliang are hosted in the Lower Permian andesite or marble. Three ore deposit types were proposed, including: 1) stratabound skarn-type (Yanshanian); 2) exhalative sedimentary (SEDEX)-type (Hercynian); and 3) SEDEX (Hercynian) - hydrothermal (Yanshanian) superimposing-type. Two generations of cassiterite (Cst-1 and Cst-2) were identified based on their microscopic features and CL images: Cst-1 is dark brown with distinct banded texture (euhedral-subhedral), whilst Cst-2 is light brown in color and cut Cst-1 (as veins) or distributed on the Cst-1 margin. They are both replaced by chlorite and quartz. The Huanggangliang cassiterite has relatively high Fe (median 4828 ppm) and W (median 273 ppm), but low Nb 2 O 5 (<0.08 wt%) and Ta 2 O 5 (<0.09 wt%) contents, distinct from SEDEX-type cassiterite but similar to granite-related cassiterite. Cst-1 has higher Fe-W-U contents than Cst-2, which reflects that Cst-1 was formed under relatively high temperature. Meanwhile, Cst-2 is relatively HFSEs-enriched, suggesting that the metallogenic environment had become more acidic. The cassiterite, zircon and garnet samples were U–Pb dated to be 137.10 ± 3.65 Ma, 138.45 ± 0.45 Ma, and 136.03 ± 1.22 Ma, respectively. Considering the Huanggangliang geology, cassiterite geochemistry and published ages from Sn-polymetallic deposits in the southern Da Hinggan Range, we suggest that the regional Sn mineralization occurred mainly in 139–134 Ma, and that the Huanggangliang deposit is best classified as skarn-type, closely related to Yanshanian magmatic-hydrothermal activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Sanhe represents the initial phase of Mesozoic Pb–Zn–Ag mineralization at Argun Massif. • Incursion of unusually metal-rich fluid was critical to the Sanhe ore formation. • The deposit belongs to intermediate sulfidation (IS)-epithermal type. • Fluid mixing was likely the main trigger for mineralization. The Sanhe is a typical medium-size Pb–Zn–Ag deposit in the Argun Massif, NE China. Its Pb–Zn–Ag orebodies are mainly hosted in the Jurassic Tamulangou Formation volcanic rocks. The orebodies occur as quartz vein clusters. The ore-forming quartz porphyry is LA–ICP–MS zircon U–Pb dated to be 165.2 ± 1.2 Ma, and the ore sphalerite yielded a Rb–Sr age of 162.5 ± 4.3 Ma. These ages indicate that the Sanhe represents the oldest Pb–Zn–Ag mineralization in the Argun Massif. Combined with published age data, the Pb–Zn–Ag mineralization of the Argun Massif occurred in three phases at ca. 160 Ma, 140 Ma and 130 Ma. The quartz porphyry shows right-inclining REE ((La/Yb) N = 22.92–40.69) patterns and negative Eu anomalies (δEu = 0.68–0.81), together with enrichments in K, La, Ce, Nd, Zr and Hf but depletions in Ba, Ta, Nb, Sr, P and Ti. Whole-rock geochemistry and Hf isotopes suggest that the quartz porphyry was derived from partial melting of juvenile lower crustal materials during the post–collision extension of the Mongol–Okhotsk orogenic belt. Sulfide S–Pb isotope compositions indicate that the ore-forming materials were derived from the deep magma, whilst He isotopes indicate that the ore fluids were dominantly crustal-derived. Fluid chemical compositions obtained from LA–ICP–MS single fluid inclusion analyses support that mixing of magmatic fluids with meteoric water was an important mineralization trigger at Sanhe. Our new data show that the involvement of unusually metal-rich fluids is a prerequisite to form abundant Pb–Zn–Ag mineralization at Sanhe. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrothermal events of 149–144 Ma revealed in the Yumugou deposit. • Skarn Mo mineralization of the Yumugou deposit was constrained at ca. 147 Ma. • Multiple interactions of melts and hydrothermal fluids for the generation of molybdenite. The Yumugou Mo-W deposit is an important porphyry-skarn deposit hosted in the world-class Luanchuan Mo polymetallic cluster, East Qinling, China. However, the origin and age of skarn Mo mineralization, as well as the temporal evolution, redox conditions and magmatic-hydrothermal processes of the Yumugou porphyry-skarn system remain enigmatic. Hence, we conducted molybdenite Re-Os and titanite U-Pb dating together with titanite geochemical studies on porphyry and skarn from the Yumugou deposit, with major view to resolve the life-cycle and evolution of the Yumugou deposit and to provide insights into the magmatic-hydrothermal evolution of regional Luanchuan porphyry-skarn system. Titanite U-Pb dating of Mo-hosting monzogranite yielded a lower intercept age of 145.0 Ma, consistent with reported zircon (147–141 Ma) and apatite (153–141 Ma) U-Pb ages of the Huangbeiling intrusion, interpreted as rapid post-magma cooling in response to shallow emplacement of granitic porphyries. Titanite U-Pb dating of skarns yielded titanite U-Pb lower intercept ages of 149.0–144.7 Ma, representing the timing of multiple hydrothermal events. Molybdenite Re-Os dating of Mo-hosting skarns yielded a weighted mean age of 147.2 Ma, which we interpret as the age of skarn Mo mineralization. Together with published age data of the Yumugou deposit, we suggest that the Yumugou porphyry-skarn system underwent magma emplacement at ca. 147–141 Ma, contemporaneous skarnization, Mo mineralization and rapid post-magma cooling at ca. 153–141 Ma, and multiple post-mineralization cooling and exhumation at ca. 114–58 Ma. Compiled molybdenite Re-Os isotopic data indicate crust-mantle mixed Mo source for all Mo-W deposits, and coupled with crust-mantle mixed magma and ore-forming materials of granitic porphyries and skarn-hydrothermal Pb-Zn-Ag deposits in the Luanchuan region, we propose that the Luanchuan porphyry-skarn system shares a single source. In addition, titanite textures and geochemical data suggest most titanites from the Yumugou deposit are of hydrothermal origin and mainly formed under reduced conditions. In conjuction with tectonic evolution of the East Qinling Orogen, we argue that the Yumugou Mo-W deposit formed during the tectonic transition from syn- to post-collisional settings (160–130 Ma), via multiple interactions of melt and hydrothermal fluids, Mo4+ aggregates S2– under reduced conditions to precipitate as molybdenites (MoS 2) in granitic porphyries and skarns. Further, we also suggest that similar Mo enrichment processes likely occurred throughout the whole East Qinling Orogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Early Cretaceous Sn mineralization in SGXR is formed under slab roll-back setting. • Cu-rich Sn granites are characterized by higher fO 2 , lower differential degree and ASI than those of Sn-W granites. • Ore-forming process experienced the cooling, increasing volatile contents and fluid-rock reaction. • Injection of oxidized fluids exsolved from mafic magma contributes to the Sn-Cu mineralization. Primary tin deposits usually contain little or no copper due to the distinct geochemistry of Sn and Cu. However, examples of copper-rich tin deposits in many tin provinces around the world are also well known. The genesis of copper-rich tin deposits remains controversial. The Maodeng Sn-Cu polymetallic, a typical Cu-rich Sn deposit in the southern Great Xing'an Range (SGXR) Northeast China, offers an excellent opportunity to reveal the genesis of coupled copper-tin deposits. The ore mineralization is associated with the granite porphyry, complement phase of the Alubaogeshan complex, which emplaced into the volcanic rocks of the Lower Permian Dashizhai Formation. Herein, we report new zircon and cassiterite U-Pb ages and their trace elements compositions, with the aim of constraining the metallogenic chronology framework, and clarifying the indicative effects of the ore-forming fluids on mineralization in different ore-forming stages, and thus establishing the genetic model for the Sn-Cu deposit. LA-ICP-MS U-Pb dating of zircon from the granite porphyry yields a weighted mean U-Pb age of 134.6 ± 0.4 Ma, which consistent to the zircon U-Pb age (ca. 138 Ma) of porphyry monzogranite (main phase of the Alubaogeshan complex) and cassiterite U-Pb ages (137–140 Ma), suggesting an Early Cretaceous Sn-Cu mineralization under the Paleo-Pacific plate slab roll-back setting. Granite porphyry displays more evolved characterisrics, with higher SiO 2 contents (71.5 ∼ 77.4 wt%), Rb/Sr ratios (3.39 ∼ 10.33) and lower Nb/Ta ratios (10.86 ∼ 13.06) compared to those of porphyry monzogranite (SiO 2 contents of 70.4 ∼ 72.1 wt%; Rb/Sr and Nb/Ta ratios of 1.03 ∼ 1.72 and 13.34 ∼ 15.83, respectively). This is further supported by the trace elements contents of zircons from granite porphyry and porphyry monzogranite, because the former has a stronger Eu anomaly, higher Hf concentrations, lower Zr/Hf and Th/U ratios than the latter. Our new data, integrated with previously published geochemical data, suggest that the granites associated with Cu-rich Sn deposits are characterized by higher oxygen fugacity, lower differential degree and aluminum saturation index (ASI) than those of Sn-W deposits. This could also use to address the Sn-Cu deposits usually have relatively small Sn mineralization potential. The trace elements of the cassiterites are characterized by high Fe (up to 3358 ppm), Ti (up to 1894 ppm) and abnormal high In (∼2500 ppm) concentrations, but low Nb, Ta contents. From early to late stage, the W and U contents and Nb/Ta and Zr/Hf ratios are increased, reveal that the ore-forming process experienced the cooling, increasing volatile contents and fluid-rock reaction. Finally, a new metallogenic model was established, which highlight oxidized Cu-rich fluids exsolved from the upwelling mantle magma would add to the reduced, Sn-rich magma chambers. This contribution indicate that, the Cu and Sn metals come from the mantle magma and crustal granitic magma, respectively, and that Cu-rich Sn deposits are more likely a product of spatial coupling. [ABSTRACT FROM AUTHOR]

[Display omitted] • Six types of pyrite formed in two overprinting gold-mineralizing events. • Monazite U-Pb dating constrains the age of early mineralization to ca. 429 Ma. • Distinct δ34S values suggest early metasedimentary and late magmatic origin of sulfur. The Tanjianshan goldfield is the most important gold producer in the North Qaidam, NW China. Genesis of gold deposits in Tanjianshan is enigmatic, primarily because of uncertainties as to timing, mineralization processes and fluid sources. We investigate these uncertainties through a comprehensive study of the texture and geochemistry (LA-MC-ICPMS trace elements and sulfur isotopes) of pyrite and in-situ U-Pb dating of monazite from the Qinglonggou gold deposit. Six types of pyrite with distinct textures, trace element contents and sulfur isotopes have been identified, and provide constraints on two overprinting gold-related hydrothermal events. Stage I consists of Py1, occurring as veinlets parallel to S1 deformation in a schist, is characterized by extremely low Co/Ni ratios with high contents of Ni, and high δ34S values (+14.9 ‰ to +16.1 ‰), and were likely derived from metamorphism of the sedimentary strata in the Tanjianshan and Wandonggou Group. In stage II, Py2 occurs in the pyrite-quartz veins that cut Py1 veinlets. They have similar δ34S (+13.1 ‰ to +17.8 ‰) to Py1, indicating that sulfur was likely derived from the dissolution of Py1. The stage I and II veins formed during an early gold pre-concentration event, which is constrained at 429.1 ± 5.9 Ma by in-situ U-Pb dating of monazite that coexists with Py1. Stage III includes Py3 and Py4 which occur in the altered carbonaceous schist and accompanying quartz veins. Trace metals are highest in Py3 (Ag, Au, Sb, and Bi) which represent the most economic ore stage in the deposit, whereas the following Py4 shows low concentrations of most trace elements due to abundant Py3 precipitation. In contrast, trace elements contents increase in Py5 to similar levels as those seen in Py3, suggesting a new pulse of fluid in stage IV. Minor Py6 grains precipitated in the youngest quartz-calcite veins associated with stage V, and contain low concentrations of trace elements. The δ34S values of Py3 (+5.2 ‰ to +6.0 ‰) and Py4 (+4.2 ‰ to +6.1 ‰) are within the range of magmatic sulfur, suggesting a dominantly magmatic source. The δ34S values increase from Py3-4 to Py5 (+6.3 ‰ to +7.4 ‰), and to Py6 (+8.7 ‰ to +9.6 ‰), probably due to increasing contribution from the host rocks, as well as decreasing f O 2 , through incremental fluid-rock interaction. Stages III and IV represent a late gold-mineralizing event during Late Paleozoic to Early Mesozoic, while stage V is post-mineralization. The overprinting gold pre-concentration and mineralization events in the Tanjianshan goldfield correspond to orogenic evolution of the Proto-Tethys Ocean and Paleo-Tethys Ocean, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three-stage scheelite and wolframite were identified. • Intense fluid-rock interaction during W(-Sn) mineralization was revealed by Sr isotope composition. • Fluid mixing triggered the precipitation of late scheelite. • The cassiterite U–Pb dating yielded 156.0 ± 0.7 Ma and 147.5 ± 0.6 Ma isochron ages, respectively. Wolframite and scheelite are primary W–bearing minerals and form in multiple metallogenic stages in quartz-vein type W(–Sn) deposits, recording copious metallogenic information. This study investigates the geochemistry, geochronology and Sr–O isotope of these minerals in the Yaogangxian W(–Sn) deposit, South China, to constrain the metallogenic age and decipher the mineralization process. Three wolframite and scheelite phases were identified in the greisen and quartz-vein type ores with different cathodoluminescence (CL) response, rare-earth element (REE) characteristics, and Sr–O isotopic compositions. The Cassiterite U–Pb dating in the greisen phase yielded a 156.0 ± 0.7 Ma isochron age and a 147.5 ± 0.6 Ma isochron age in the oxide phase, both of which are within error or slightly younger than Jurassic granites. From the early to late stage, the ΣREE contents of scheelite and wolframite decreased sharply, and the REE patterns of the scheelite changed from the LREE-enriched with negative Eu anomalies to HREE-enriched with positive Eu anomalies. The δ18O H2O values of the fluid (8.5 ‰–8.8 ‰) in the greisen phase calculated using the scheelite–H 2 O fractionation equation are identical to the magmatic–hydrothermal fluid, whereas the δ18O H2O values of the fluid (1.4 ‰–1.6 ‰) in the sulfide phase indicate the fluid mixing with meteoric water. The (87Sr/86Sr) 0 ratios of wolframite and scheelite in the quartz-vein type ores range from the 0.74972 to 0.78397, higher than the Jurassic granites ((87Sr/86Sr) 0 = 0.71593–0.73188) but lower than the sandstone in the host rock ((87Sr/86Sr) 0 = 0.785227–0.813912), indicating an intense fluid-rock interaction. Therefore, although the W(–Sn) mineralization is primarily related to Jurassic granites, fluid mixing and fluid–rock interaction in the quartz-vein type ores might have been a trigger mechanism for W(–Sn) precipitation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mineralization of the Quanzigou Mo deposit is closely related to the quartz porphyry. • The Hongniangshan complex mainly originated from partial melting of a Paleoproterozoic lower crust. • Both the medium–coarse-grained granite and the porphyritic granite experienced magmatic mixing. • Magma of the complex experienced fractional crystallization in different extent. • The Hongniangshan complex emplaced in a post-collisional tectonic setting. The Quanzigou porphyry molybdenum deposit is located in Fengzhen County, Inner Mongolia, China, belonging to the northern margin of the North China Craton. A Yanshanian granitic complex, namely the Hongniangshan complex, is exposed in the deposit, mainly composed of medium–coarse-grained granite, porphyritic granite, and quartz porphyry. The Mo orebodies occur mainly in the porphyritic granite as ore-bearing quartz veins or veinlets. Previous study on molybdenite Re–Os and zircon U–Pb dating suggests that the Hongniangshan complex emplaced during 173–160 Ma and that the Quanzigou Mo deposit formed at ca. 160 Ma. Geochemical analyses in this study show that all these Middle–Late Jurassic granites are peraluminous, high-K calc-alkaline granite, featured by enrichment in Rb, Th, U, Hf, and Zr and depletion of Ba, P, and Ti, with high K 2 O/Na 2 O ratios. Nearly all the samples from the medium–coarse-grained granite and the porphyritic granite show weakly negative Eu anomalies, whereas the negative Eu anomalies of the quartz porphyry are moderate or strong. The Hongniangshan complex has low zircon ε Hf (t) values (−14.4 to − 6.7), old single-stage and two-stage model ages (1099–1471 Ma and 1637–2124 Ma, respectively), and low K-feldspar Pb isotopic compositions (206Pb/204Pb = 17.019–17.590, 207Pb/204Pb = 15.365–15.489, 208Pb/204Pb = 37.002–37.670), with K-feldspar δ18O values of 8.0–10.4‰, suggesting that the granitic complex was predominantly originated from a Paleoproterozoic lower crust source. Geochemical characteristics, combined with results from previous studies, show that the Quanzigou Mo mineralization was closely related to the quartz porphyry. The Middle Jurassic medium–coarse-grained granite was likely formed in the back-arc extension environment triggered by the subduction of the Mongol–Okhotsk Ocean and the Paleo-Pacific plate, and the formation of the Late Jurassic porphyritic granite and the quartz porphyry was controlled by both the post-collisional process of the Mongol–Okhotsk orogenic belt and the coeval subduction of the Paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two type zircons and volatile-rich HREE mineral are distributed in the granites for all HREEs ion-adsorption deposits. • Highly fractionated granite to a magmatic-hydrothermal stage is vital to the generation of HREEs ion-adsorption deposits. • Long-term extensional setting in South China during Mesozoic favors to magmatic differentiation. • Zircons could uncover the HREEs ion-adsorption mineralization potential of granites. The key point for further prospecting of heavy rare earth elements (HREE) ion-adsorption deposit is to figure out the granites that could generate HREE ion-adsorption mineralization in weathering processes. In this study, we present a detailed study of zircons from granites associated with Zudong, Dabu, and Xinfeng HREE ion-adsorption deposits in South China. The zircons were studied with regards to their texture, crystallinity, U-Pb dating, and geochemistry. The zircons from these granites all can be subdivided into two types. The type-1 zircons show oscillatory zonation and have Th/U and Zr/Hf mass ratios of 0.4–1.0 and 30–50, respectively. These textural and geochemical features indicate crystallization in a fractionated magma. The type-2 zircons are unzoned, occasionally porous, and have a low crystallinity. They occasionally rim type-1 zircons. The type-2 zircons show significantly higher F, P, Hf, Th, U, and REE contents, but display lower ZrO 2 and SiO 2 contents and lower Th/U, Zr/Hf, La/Yb ratios than those of the type-1 zircons. These geochemical features are consistent with zircon formation in a volatile-HREE-rich magmatic-hydrothermal transition stage. Under these conditions, the HREEs were also hosted in volatile-rich REE mineral phases including synchysite-(Y), aeschynite-(Y), calcybeborosilite-(Y), and atelisite-(Y), which have been observed in these HREE deposits. These volatile-rich REE-mineral phases can easily be dissolved during weathering and release HREE3+ to generate ion-adsorption HREE deposits. Therefore, we conclude that the granitic magma progression to a volatile-HREE-rich magmatic-hydrothermal system is vital for the generation of HREE ion-adsorption deposits. The long-term Mesozoic extension of the South China favors the generation of highly fractionated granites and is thus important for the generation of HREE ion-adsorption deposits. Furthermore, the zircons generated in a volatile-rich environment could be used to determine the HREE ion-adsorption mineralization potential of granites. [ABSTRACT FROM AUTHOR]

• The Dongguashan mineralization may have formed from magmatic-hydrothermal fluids. • Garnet LA-ICP-MS U-Pb dating yielded ages of 135.9 ± 2.1 Ma, 135.6 ± 2.2 Ma, and 134.6 ± 1.4 Ma, which provide constraints on the alteration initiation. • Physicochemical conditions of hydrothermal fluids for Dongguashan garnet were constrained. Dongguashan is one of the largest Cu-Au deposits in eastern China, with ubiquitous garnet in the stratiform and skarn orebodies. The stratiform ore-formation remains enigmatic. In this study, we describe the diverse textures and present new U-Pb age and chemical data for the Dongguashan garnet. Garnet in the skarn orebody can be divided into three generations (Grt-1, Grt-2, and Grt-3). Grt-1 and Grt-2 show three zones from core to inner rim to outer rim (a-b-c). Garnet in the stratiform orebody is homogeneous (Grt-s). All garnet types have low MnO, a wide range of Y/Ho ratios, and visible fluid inclusions, indicating that they formed from hydrothermal replacement. Grt-1a, Grt-1b, Grt-2a, Grt-2c, and Grt-3 are oscillatory-zoned, low-Sn, and HREE-rich grandite, which may have formed from reduced HREE-rich fluids. Meanwhile, Grt-1c and Grt-2b are high-Sn, LREE-rich andradite, and may have formed from oxidized LREE-rich fluids. Grt-s is pure, low-Sn, LREE-rich andradite, and that may have formed from oxidized LREE-rich fluids. The Eu behaviors are sensitive to the fluid physicochemical conditions and Cl content. Grt-1, Grt-2, and Grt-s have positive Eu anomalies, and may have formed from acidic and Cl-rich fluids. Grt-3 has negative Eu anomalies and was possibly formed from neutral and Cl-poor fluids. All garnet types at Dongguashan may have formed by infiltration metasomatism in an open system with multiple metasomatic pulses. Grt-1, Grt-2, and Grt-s yielded nearly the same in-situ U-Pb ages of 135.9 ± 2.1 Ma, 135.6 ± 2.2 Ma, and 134.6 ± 1.4 Ma, respectively. We propose that both ore types at Dongguashan deposit are closely related to the Early Cretaceous plutonism. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Keketale Pb-Zn deposit was formed and was modified in ∼400 Ma and ∼265 Ma, respectively. • The original VMS hydrothermal system can be illustrated by magnetite petrology and geochemistry. • Magnetite has the potential to be an indicator of VMS mineralization. • The Keketale deposit witnessed the evolution of the Chinese Altai and the Paleo-Asian Ocean. The Keketale Pb-Zn deposit (KKTL deposit) is one of the largest VMS-type Pb-Zn deposits in the Altai Mountains, Central Asian Orogenic Belt. Field investigations and microscopic observations suggest that the evolution of the deposit can be divided into two major stages: syngenetic massive sulfide mineralization related to coeval volcanism and epigenetic polymetallic vein mineralization linked to metamorphism and deformation. Supported by the U-Pb dating of zircon and garnet of immediate host rocks (i.e. garnet biotite schist), the former occurred in ∼400 Ma during the Early Devonian, and the latter developed in ∼265 Ma during the Middle Permian. The original VMS hydrothermal system is varying in the physicochemical conditions (e.g., temperature, oxygen fugacity, and sulfur fugacity) in space, together with fluid-rock interactions, causing two types of magnetites with different compositions and textures in different sites. Furthermore, it is revealed that the spatial variations of temperature-sensitive elements (e.g., Ti and Sn) of magnetite can be used to find the location of the hydrothermal vent, which can serve to guide the regional prospecting. Modifications of the KKTL deposit are indicated by deformed sulfides, annealed sulfides, remobilized sulfides, and epigenetic polymetallic veins. We draw a conclusion that the KKTL deposit witnessed the evolution of the Chinese Altai and the Paleo-Asian Ocean, the syngenetic volcanic-associated VMS mineralization was linked with arc/arc-back tectonic setting caused by the subduction of the Paleo-Asian Ocean toward the Chinese Altai, and the modification of the KKTL deposit was related to the collision between the Chinese Altai and the Junggar Block, along with the closing of the back-arc basin. [ABSTRACT FROM AUTHOR]

[Display omitted] • The monzogranitic porphyry is the ore-forming intrusion in Luming porphyry Mo deposit. • Apatite and zircon geochemical data can be used to identify ore-forming intrusions. • The juvenile lower crust with addition of Mo-enriched ocean sediments is critical to Mo concentrate in the source and the regional Mo mineralization. The Luming giant porphyry Mo deposit in NE China host >0.89Mt Mo, but which intrusion induced the Mo mineralization is still in debated. In this study, apatite and zircon geochemistry from three mentioned ore-forming granites, namely monzogranitic porphyry (MGP), granodiorite (GD) and monzogranite (MG) in Luming ore district are presented in order to constrain the real ore-forming granite. Apatite and zircon U-Pb dating of the MGP, GD and MG yield a crystallization age of ca. 177 Ma, ca. 187 Ma and ca. 186 Ma, respectively. Whole-rock geochemistry, in-situ apatite Sr-Nd and zircon Hf isotopic compositions suggest that these granites formed by partial melting of juvenile lower crust with different depth. Both the MGP and GD have adakitic affinities and the depth of their magma source is > 45 km with garnet as residual phase, whereas the source depths for the MG was < 33 km with plagioclase as residue. Apatite and zircon geochemical features indicated that the magma of MGP and GD have higher oxygen fugacity, water contents and lower Ti-in-zircon temperatures than these of the MG, which make the MGP and GD are more favorable for Mo mineralization, but the less volume of GD limited its metallogenic potential. Decoupled Nd-Hf isotopes of the MGP, GD and MG could be induced by recycled ocean sediment added in their source region, and the addition of recycled sediments could be account for Mo concentrate in the source and regional Mo mineralization. [ABSTRACT FROM AUTHOR]

• The Bailingshan dacitic tuffs formed at 312 Ma. • Bailingshan dacitic tuffs were derived from melting of juvenile lower crust mixed with mantle materials. • The dacitic tuffs and iron mineralization were generated by the subduction of the Paleo-Tianshan oceanic plate. The Bailingshan deposit is an economically important Fe deposit in Eastern Tianshan, located in the southern margin of the Central Asian Orogenic Belt, Xinjiang, northwest China. The orebodies at Bailingshan are mainly hosted in the Carboniferous volcanic rocks. In this study, new secondary ion mass spectrometry (SIMS) zircon U-Pb dating, whole rock geochemistry, zircon Hf-O isotopic analyses and Sr-Nd isotopic analyses were carried out on the Bailingshan dacitic tuff. New SIMS zircon U-Pb dating results indicate that the dacitic tuff occurred in the Late Carboniferous (312.1 ± 3.3 Ma and 312.4 ± 4.4 Ma). The geochemistry of the dacitic tuff is consistent with calc-alkaline arc magmatism, characterized by high SiO 2 (70.33–74.70 wt%) and (La/Yb) N values of 1.06 to 3.47. In addition, the Bailingshan dacitic tuff displays variable ε Hf (t) values (+8.2 to + 14.1), low δ18O values (4.70 to 6.35 ‰), high Mg# values (30–59), together with relatively uniform ε Nd(t) values from + 2.1 to + 5.8 and (87Sr/86Sr) i ratios ranging from 0.703818 to 0.707168, suggesting a fractional crystallization dominated origination from melting of a juvenile lower crust that mixed with the depleted mantle materials was most likely responsible for genesis of the Bailingshan dacitic tuffs. Combined with regional tectonic evolution and our new data, we infer that the change of subduction angle led to the rupture of magma chamber and the release of the Fe-rich fluids from magma chamber, causing the iron mineralization and relevant alteration of Bailingshan deposit in the Aqishan-Yanmansu arc. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au mineralization and ore-related magmatism occurred in an extensional setting associated with the subduction of the Paleo-Pacific Plate. • The synchronic basic dikes and granites can be regarded as a precursor to the Au mineraliziton in the JMD. • Mantle- and crustal-fluids and metals substantially contributed to the formation of the giant Au mineralization in the JMD. The Jiapigou mining district (JMD) in the northeastern margin of the North China Craton mainly contains quartz vein- and altered rock-type gold deposits that have been prospected and mined for over 200 years. However, the ore-formation mechanism and geodynamic setting are still limited understood. Here we present new geological, mineralogical, gochronological, geochemical and Hf isotopic evidences of the ore-related intrusions from the deposits in the JMD to reveal the tectonic setting and genetic relationship between the Au mineralizitions and synchronic magmatism. The results show the following: (1) zircon U–Pb dating of the ore-related intrusions, such as basic dikes (gabbro and porphyritic gabbro), granites, and acid dikes (granite aplite dike and rhyolite porphyry) bracket their emplacement in the range of 177–171 Ma; (2) The basic dikes are characterized by enrichment in large ion lithophile elements (LILEs; i.e., Rb, Ba, and U), moderately depletion of high field strength elements (HFSEs; i.e., Nb and Ta), and high ε Hf (t) values (–13 to +12.8), whereas granites are characterized by high SiO 2 (73.24–75.12 wt%) and total alkali (K 2 O + Na 2 O = 5.74–8.58 wt%) concentrations, low TFe 2 O 3 (0.78–1.43 wt%) and CaO (0.98–1.36 wt%) concentrations, enrichment of LILEs (i.e., Rb, Ba, Th, and K) and depletion of HFSEs (i.e., Nb, Ta, Ti, and P), and low high ε Hf (t) values (–13.6 to –11.0), which features as well as those of the acid dikes. These results indicate that the ore-related intrusions, such as basic dikes, granites, and acid dikes were emplaced during the Middle Jurassic (177–171 Ma), constrained that the giant Au mineraliziton in the JMD occurred in the Middle Jurassic. And the basic dikes were likely derived from an enriched lithospheric mantle source that has been influenced by fluids expelled from a subducted slab, whereas granites and acid dikes were likely derived from partial melting of Archean crustal materials. Combined with regional geological observations, we conclude that the giant Au mineralization and ore-related magmatism occurred in an extensional setting associated with the subduction of the Paleo-Pacific Plate. The basic dikes and granites can be regarded as a precursor for the Au mineraliziton in the JMD. And mantle- and crustal-fluids and metals substantially contributed to the formation of the giant Au mineralization in the JMD. [ABSTRACT FROM AUTHOR]