In porphyry systems, the physicochemical properties of ore-related intrusions critically influence both metallogenic fertility and the resulting metal assemblages. Biotite is a widespread magmatic mineral capable of recording subtle changes in physicochemical parameters throughout the evolution of porphyry systems. Throughout the years, several biotite thermobarometers have been proposed; however, the most appropriate combination for application to porphyry systems remains uncertain. In the Julong Cu–polymetallic district, where magmatic biotite is pervasive in the ore-related intrusive suite, we integrate available temperature, pressure, and oxygen fugacity data to assess which combination of biotite-based thermobarometers best captures the physicochemical condition of the magma. Our results demonstrate that the structural formula recalculation method of Li et al. (2020), when combined with the thermometer of Li and Zhang (2022) and the barometer of Uchida et al. (2007), yields the most accurate reconstruction of magmatic conditions in porphyry systems. In the Julong district, this integrated approach reveals that the earliest granodiorite crystallized at depths of ~3.2–6.3 km, under strongly oxidizing conditions (~NNO+3 to HM) and in the presence of elevated volatile concentrations. A slightly younger monzogranite formed at ~4.4 km depth, recording lower oxygen fugacity conditions (~NNO+2 to NNO+4). Its elevated F concentration and lower oxygen fugacity suggest a genetic link to the fractional crystallization of magmatic phases, especially magnetite. On the other hand, the ore-related monzogranite porphyry (~NNO+3 to HM) shares the oxidized signature of the granodiorite and was emplaced at ~3.4 km depth. Its low log(fH2O/fHCl) value reflects elevated HCl activity, conducive to the efficient magmatic transport of Cu and Mo.

Liba gold deposit, located in the western Qinling metallogenic belt, is a super-large gold deposit. The source of ore-forming materials and the mechanism of gold enrichment and precipitation are still controversial. Through detailed field investigation and microscopic observation, this paper studies the occurrence characteristics of pyrite and arsenopyrite in mining areas, and delineates the geological-mineralization processes as the sedimentary (-metamorphic) period, pre-mineralization/early mineralization stage, main mineralization stage, and late mineralization stage. In-situ geochemical studies of major, trace elements and sulfur isotopes of pyrite in different stages show that pyrite (PyO) in the sedimentary stage is a typical sedimentary genesis, pyrite (Py2) in the main metallogenic stage and pyrite (Py3) in the late metallogenic stage are generally characterized by hydrothermal genesis, while pyrite (Pyl) in the pre-metallogenic and early metallogenic stage has the characteristics of composite genesis of sedimentation and hydrothermal. There is a good positive correlation between Au and As contents in pyrite, which indicates that gold mostly exists in pyrite and arsenopyrite in the form of solid solution. Au, Sb, Pb and Tl in pre-mineralization and early mineralization stage pyrite (Pyl) are predominantly incorporated into the crystal lattice through isomorphic substitution, but tend to separate from the crystal lattice of pyrite in the main stage of mineralization and in the late stage of mineralization. Sb, Pb and other elements exist in pyrite in the form of inclusions such as galena, while Au may be finely dispersed in pyrite or exist in other sulfides. The 8"S value of pyrite in Liba gold mine is 2.54%-12. 1%, which reflects that sulfur mainly comes from magmatic hydrothermal solution generated by water-rock reaction with surrounding rock strata. The geological thermometer estimation results of arsenopyrite show that the ore-forming temperature and sulfur fugacity of ore-forming fluids tend to decrease from early stage to late stage, reflecting sulfur depletion in the fluid system caused by arsenopyrite precipitation.

Qingshan Au-Pb deposit, located in Tanjianshan ore concentration area, northern Qaidam basin, is a paragenetic or associated Au-Pb orogenic deposit that is very rare in the world. The ore of the deposit mainly exists in the schist of the Paleoproterozoic Darken Daban Group, whose distribution is controlled by the NW-trending fault. There are two types of ores, i.e., the altered rock type and the quartz vein type. Sulfides, including pyrite, limonite, galena, chalcopyrite, sphalerite and so on, are well developed in the ores. Among them, the pyrite is the main gold-bearing mineral in the deposit, whose geochemical characteristics not only indicate the existent state of gold but also reveal the properties of ore-forming fluid and the genesis of deposit. Samples of different types of ores and country rocks together with pyrite in them at different depths in boreholes ZK2103 and ZK3701 were selected to analyze their whole rock compositions and ore-forming elements. The chondrite-normalized REE distribution model curves of the measured samples are right-lean-shaped with obvious Eu negative anomaly, but no Ce anomaly, showing that the ore-forming fluid is from metamorphic without any seawater. The ores are relatively enriched Au, Ag, Cu, Pb, Zn, As, Co, Bi, Sb, W, Ni, Sr, Cd and V elements, but depleted in Sn, Mo and Cr elements. The S/Fe values of pyrite in the ore and country rocks are less than 2.0, showing they are depleted in S but enriched in Fe. The Au/Ag value of pyrite is greater than 0.5, and the results of Co-Ni diagram all show that the pyrite is of hydrothermal origin. The gold mainly exists in the form of nanoparticles, with a small amount of gold existing in the form of solid solution. Gold was mainly transported in the form of Au(HS)2-. However, the mixing of fluids destroys the stability of Au(HS)2-, that is most likely the reason for gold precipitation. The sulfur content in the ore-forming fluid is high, as a result, a certain amount of Cu, Pb and Zn will be migrated with sulfur. After the gold precipitates, the reduction of temperature and pressure in the fluid leads to the Pb precipitation. Due to the limited ability of the fluid to transport Pb and Zn, the lead ore of Qingshan deposit developed in small scale. The results of S and Pb isotopes show that the ore-forming material comes from the strata, however, contents of Pb and Zn in the strata of Jinlonggou and Qinglonggou mining areas is low, so there is no lead ore formed in this area.

位于东昆仑造山带东段的浪木日铜镍钴多金属矿床，在新近勘查工作中又圈出独立的铂矿体，对该矿床成矿特征的进一步研究有助于指导勘查找矿.通过矿床地质特征分析，结合含矿橄辉岩主微量元素、Sr‐Nd同位素及其中橄榄石、云母主量元素测试，以及黑云母花岗岩锆石U‐Pb年代学及岩石地球化学特征研究，探讨了浪木日矿床成矿特征、成矿时代及矿床成因.含矿橄辉岩中橄榄石属贵橄榄石（Fo值为86.72～88.39），云母为金云母，其均为幔源岩浆作用产物；含矿橄辉岩稀土元素具右倾型的配分模式，富集Cs、Rb、U等元素，ε Nd （t）值为0.66～2.66，暗示其形成过程中经历了地壳混染.获得黑云母花岗岩U-Pb年龄为414.5±8.8 Ma，其具弧岩浆地球化学特征，( 87 Sr/ 86 Sr) i （0.718 609～0.719 177）、ε Nd （t）值（1.28～5.36）显示其为壳幔岩浆混合作用产物.本研究认为浪木日铜多金属矿床具叠加成矿特征，在450～439 Ma形成与橄辉岩有关的铜镍钴铂钯矿体的基础上，叠加了415 Ma的与黑云母花岗岩有关的热液脉型铜矿化；本矿床以早期与橄辉岩有关的硫化物成矿为主，岩浆演化过程中的地壳混染及岩浆期后热液活动对成矿具积极贡献.本矿区基性-超基性杂岩体底部及顶部、黑云母花岗岩与之接触部位均为有利找矿空间.

The Qingshan gold deposit is located in the Tanjianshan ore collection area, which is in the northern margin of Qaidam Basin and is one of the most important gold and polymetallic metallogenic belts in China. Based on the field investigation and optical microscopic observations, mineralization at the Qingshan deposit can be divided into three stages: (1) quartz-pyrite stage, (2) quartz-sulfide-gold stage, (3) quartz-calcite stage. Pyrite from the stage 1 (Py1), stage 2 (Py2) and stage 3 (Py3) are selected for LA-ICP-MS trace element analyses. Pyrite from the stage 1 (Py1), stage 2 (Py2) are selected for in situ sulfur isotopes analysis. Pyrite from the stage 1 (Py1), stage 2 (Py2) and stage 3 (Py3), galena from the stage 1 (Gn1) and stage 2 (Gn2) are selected for in situ lead isotopes analysis. The result shows that Py1 is relatively rich in Co, Ni, Zn and Ag contents and lacking in Sb contents. Py2 is relatively rich in Cu, As, Sb, Au, Pb and Ag contents and lacking in Co, Ni and Bi contents. Py3 is relatively rich in Co, Ni and Bi contents and lacking in Zn, As, Au and Pb contents. The Au/As ratio shows that invisible gold occurs in the form of solid solution (Au+). The values of Au/Ag and Co/Ni ratio show that the pyrites in the Qingshan deposit are hydrothermal origin. The S isotope values of pyrite range from -4.33 to 4.97%o (mean: 3.71%o, n = 31). The Pb isotope compositions with 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values ranging from 18.002 to 18.791, 15.567 to 15.584, and 38.410 to 38.485, respectively. The results of in situ S-Pb isotopic indicate that sulfur and metals of the Qingshan deposit were mainly derived from the upper crust and orogenic belts. The Qingshan gold deposit is classified as an orogenic gold deposit, and was closely related to a large-scale ductile shear zone, which formed during the process of subduction between the Qaidam block and the Qilian block in the Variscan period. The mixing of fluids destroyed the stability of Au(HS)2- and is most likely the reason for gold precipitation.

The East Tianshan copper metallogenic belt is an important part of the Central Asian metallogenic belt, which mainly includes large-scale Tuwu and Yandong, medium-scale Sanchakou and Yuhai, and small-scale Chihu, Fuxing, Linglong, Yudai and Sidingheishan porphyry copper deposits. The porphyry copper belt is distributed along the Dananhu-Tousuquan island arc in a nearly EW direction. Magmatic activities related to this metallogenic belt mainly include two peak periods of the Silurian and Carboniferous periods, while the peak period of mineralization is the Carboniferous. The host rock strata of the porphyry copper belt are mainly Paleozoic volcanic rocks, granites and sedimentary rocks. The wall rock alteration mainly includes biotite-magnetite alteration, phyllic and propylitization, with a relatively weak potassium alteration. The ore-forming rocks are mainly intermediate-acid calc-alkaline granites with typical island arc magmatic and adakite characteristics, which are enriched in large ion lithophile elements and depleted in high field strength elements with high Sr/Y ratios. In the early stage of ore-forming fluid, a large number of daughter bearing high salinity inclusions are developed, which is an H2O-NaCl +/- CO2 system. H-O-S isotopes show obvious magmatic hydrothermal characteristics. Sr-Nd-Hf isotopic characteristics indicate that the ore-bearing rocks have a mixed source of juvenile crust and depleted mantle. The East Tianshan orogenic belt experienced a multi-directional and multi-stage arc basin transformation in the Paleozoic and experienced multiple magmatic hydrothermal activities, as a result, it has the characteristics of multi-stage superimposed mineralization. The Carboniferous calc-alkaline magmatic rocks are the main target for ore prospecting in the next step, and the late structural superposition may lead to the formation of rich ore bodies.

为了给找矿勘探开发提供基础地质依据和支撑,本文在最新的1:5万面上资料基础上,对卡拉塔格矿集区早古生代火山活动旋回及其成矿类型开展研究.依据早古生代火山岩石组合及火山时空活动特征分为4个亚旋回.第一亚旋回为一套裂隙式喷发为主的玄武质—安山玄武质岩石组合,主要发育于南部,产有红海VMS型铜锌矿床;第二亚旋回以中心式喷发为主的安山质—英安质岩石组合,中部活动最强烈,产有红石热液石英脉状铜矿床;第三亚旋回为裂隙式火山喷发为主的玄武质—安山玄武质夹安山质—英安质岩石组合,主要发育于北部,产有红石北VMS型铜金矿床;第四亚旋回为高位侵出或中心式喷发产出的流纹质岩石组合,产有红山浅成低温铜金矿床.

Three generations of garnets are distinguished in the Yamansu volcanic-hosted skarn iron deposit in NW China, and their detailed textures and geochemical characteristics are presented to reveal the mechanisms controlling the distribution of trace elements in the garnets and to discuss the physicochemical conditions and evolution of the ore-forming fluid. First-generation garnets (Grt1) show well-preserved core-rim growth zonation and have considerable variations in composition (And25-99Gro0-73). Second-generation garnets (Grt2) show complex core-mantle-rim zonation textures with high andradite components (And54-99Gro0-44). Third-generation garnets (Grt3) occur in veins and exhibit nearly monotonic textures and geochemical components (And48-51Gro46-49). Garnet crystals in different generations have variable trace element compositions, such as REEs, U, and Y. We speculate that Grt1 cores were derived from a magmatic-hydrothermal fluid and crystallized in a closed system with low water/rock (W/R) ratios, low oxygen fugacity, and neutral pH, with the distribution of trace elements in Grt1 cores being largely controlled by crystal chemistry. However, during the crystallization of Grt1 rims and Grt2 cores, the hydrothermal fluid system is interpreted to have been open with high W/R ratios and with internal complexes (Cl complex) and external fluid (seawater-like) integrally controlling the fluid properties. The incorporation of trace elements into the Grt1 rims and Grt2 cores was controlled by not only crystal chemistry but also crystal-liquid equilibrium. The Grt2 mantles and rims are interpreted to have formed in a closed system as a result of crack-seal fluid flow. The inferred stable conditions associated with low W/R ratios, a reducing environment, and nearly neutral pH favored Fe reduction in the hydrothermal fluid and provided a material basis for later deposition of iron ores. Grt3 likely formed under near-equilibrium chemical conditions, with low W/R ratios during periods of slow fluid influx determined by episodic supply of hydrothermal fluids, and their distributions were largely controlled by crystal chemistry. The special environment of multistage hydrothermal fluid in the Yamansu deposit was the key factor controlling the multiple enrichment and precipitation of trace elements into garnet.

韧性剪切带型金矿是一种重要的金矿成因类型.韧性剪切带型金矿主要具有以下特征:(1)主要分布在板块边缘;(2)矿体呈上部陡倾、下部平缓的脉状分布,垂向延伸远大于水平延伸;(3)不同矿化类型在同一部位叠加出现;(4)成矿物质和成矿流体呈多源性.区域深大断裂和大规模韧性剪切带控制着金矿田的展布,次级的韧性剪切带控制了金矿床的产出,韧性剪切带是这类型金矿的主要控矿因素.具较高金背景值的古老绿岩带和韧性剪切带中的岩浆作用,是韧性剪切带型金矿成矿的有利条件.韧性剪切带型金矿中金的活化迁移是伴随着韧性剪切作用进行的.成矿流体的闪蒸作用和沸腾作用是金卸载和富集的重要机制.韧性剪切带型金矿的成矿作用过程经历了多期次、多阶段的复杂过程.此外,本文对韧性剪切带型金矿的有效勘查手段进行了归纳,并展望了韧性剪切带型金矿研究的发展.

位于青海大柴旦镇境内的尕日力根金矿床是青海境内发现的砾岩型金矿床.其矿体主要赋存在下-中二叠统勒门沟组砾岩夹薄层砂岩中,矿体主要呈似层状、透镜状,且受地层控制明显;金主要富集在含矿砾岩的胶结物中,重砂实验中发现了原始砂金.矿区还发育辉锑矿脉、含金黄铁矿脉,石英中流体包裹体低盐度(4.01％～10.74％)、中低温(169.8～256.3℃)的特征均暗示研究区可能存在后期热液的扰动.该矿床成矿可划分为沉积成矿阶段和热液成矿阶段,其属于沉积成矿和热液叠加成矿复合成因.

位于东昆仑造山带的那更康切尔沟银多金属矿床是近年来发现的一大型热液脉型矿床.本文研究发现矿区深部流纹斑岩中存在斑岩型Cu矿化,且获得该流纹斑岩LA-ICP-MS锆石U-Pb年龄为253.2±1.7 Ma,形成于晚二叠世.赋矿流纹斑岩SiO2含量为75.56％～76.01％,Na2O+K2O含量为4.09％～7.68％,K2O/Na2O为0.92～11.78,A/CNK为1.05～2.41,属高硅、高钾钙碱性过铝质岩石.该流纹斑岩明显富集Rb、K等大离子亲石元素(LILE),亏损Nb、Ti、P等高场强元素(HFSE);稀土总量(ΣREE)为245×10-6～265×10-6,轻重稀土元素分馏明显((La/Yb)N=7.76～9.96),并表现出 Eu负异常(δEu=0.03～0.38).综合分析认为那更康切尔沟矿区可能存在多期岩浆活动,形成斑岩型和热液脉型叠加成矿,该认识对本矿区乃至区域上寻找与火山-次火山热液有关的多金属矿床,尤其是深部找矿工作具有重要的指导意义.

The Hongyuntan deposit, which is one of the typical volcanic-hosted Fe deposits in the Aqishan-Yamansu metallogenic belt of the Eastern Tianshan Orogenic Belt, primarily consists of Fe and skarn minerals (especially garnet). Two generations (three types) of garnets were identified in the Hongyuntan deposit based on field and optical characteristics. Hongyuntan garnets are Fe-rich and belong to the grossular-andradite solid solution series (And = 50.99%-100.00%, average: 79.06%). Garnets of the first generation (Grtl) are massive aggregates and are fine-grained with well-developed oscillatory zonings. They have Type I (two-phase liquid and vapor) and Type II (multi-phase daughter mineral-bearing) fluid inclusions and experienced high temperature (540-560 degrees C) and salinity (9.2-63.2 wt% NaCl eqv) conditions. The Grt1 have high Sigma REE, LfREE/HREE, delta Eu, U, Y, and high field strength element (HFSE: sum of Nb, Ta, Zr, and Hf) contents. Garnets of the second generation (Grt2) are vefin types and are characterized by irregular shapes with irregular zonings. Type A garnets of the second generation (Grt2-A) usually coexist with mafgnetite and have Type I and Type II fluid inclusions with relatively high temperature (480-500 degrees C) and salinity (9.5-36.6 wt% NaCl eqv) values. Compared to Grtl, Grt2-A have low And, U, and LREE/HREE together with medium Sigma REE, delta Eu, HFSE, and Y contents. Type B garnets of the second generation (Grt2-B) usually coexist with epidote and quartz. They merely have Type I fluid inclusions with medium-low temperature (260-280 degrees C) and salinity (6.6-12.7 wt% NaCl eqv) values. Grt2-B have high And, delta Eu, and LREE/HREE contents but very low Sigma REE, HFSE, and Y contents. The fluid inclusions and geochemical properties of the garnets indicate that the temperature, salinity, oxygen fugacity (fO(2)), and pH of the ore-forming fluid fluctuated, indicating Hongyuntan deposit likely experienced superimposed mineralization. Grt1 originated in a magmatic-hydrothermal fluid and formed through diffusive metasomatism under relatively high fO(2), neutral pH, and low water/rock (W/R) ratio conditions. The reduced Fe and other siderophile elements in the ore-forming fluid, which formed Grtl, are believed to be the material basis for iron ores in the later main metallogenic stage. Grt2-A demonstrate the characteristics associated with transitional fluid, which most likely originated from the episodic hydrothermal supplies. However, the oreforming fluid system gradually opened up during the crystallization of Grt2-B, and the decreasing temperatures and depletion of ore-forming materials were ultimately unfavorable for the deposition of magnetite.

The volcanic rocks hosting the iron deposits in the Aqishan-Yamansu metallogenic belt are sodium-rich. The geochronology, petrography, and geochemistry of minerals and sodium-rich rocks as well as the relationship between these rocks and the iron deposits are studied. Geochemically, the ore-hosting volcanic rocks are sodiumrich (the averages of Na2O and Na2O/K2O are 4.31 wt.% and 8.56, respectively) and belong to the calc-alkaline series. They are enriched in LREEs and LILEs (Ba, U, K, and Sr), but depleted in HFSEs (Nb, Ta, and Ti). SHRIMP zircon U-Pb dating of the crystal tuff in the Aqishan Formation and the dacite in the Tugutu Bulak Formation yields ages of 337.5 +/- 2.3 Ma (n = 15, MSWD = 0.85) and 313.0 +/- 3.3 Ma (n = 13, MSWD = 0.74), respectively, indicating that the sodium-rich volcanic rocks formed from the early-late Carboniferous. Electron microprobe data from plagioclases demonstrate that albites and/or oligoclases were formed in the basic-intermediate-acid volcanic rocks. Two stages of albitization are identified, and the latter is likely attributed to the dissolution of iron in the Aqishan-Yamansu belt. The sodium-rich volcanic rocks probably formed by the interaction between volcanic lava and seawater after volcanoes erupted on the seafloor; meanwhile, the albites formed by element substitution in a low-metamorphic environment. The spatiotemporal coupling relationship between sodium-rich volcanic rocks and iron deposits in the Aqishan-Yamansu belt is favorable. Iron dissolved from the dark minerals of basic-intermediate volcanic rocks through sodium metasomatism is one of the material sources for the iron deposits.

The Chinese East Tianshan is the easternmost sector of the Tianshan Mountain Range in the Central Asian Orogenic Belt (CAOB), and accommodates several events of magmatism, crustal growth and mineralization. The Kalatag arc is unique in the East Tianshan due to its widespread Early Paleozoic volcanic rocks, which offers a special opportunity to study the Early Paleozoic Cu-dominant mineral systems in island arc setting. In this region nine deposits have been discovered in recent years. These deposits occur in Paleozoic volcanic rocks between the Kalatag Fault and Kabei Fault, and can be divided into six mineral systems, i.e., VMS Cu-Zn, epithermal Cu, porphyry Cu-Au, skarn Fe-Cu, magmatic Cu-Ni sulfide and hydrothermally overprinted deposits. Among them, VMS, epithermal, porphyry-skarn and magmatic Cu-Ni sulfide mineralization are distributed in the southeastern, central, northwestern and westernmost Kalatag, respectively. The mineralization and associated intrusive rock ages can be clustered into four episodes in the Kalatag arc, i.e., Late Ordovician-Silurian (ca. 450-430 Ma), Middle Devonian (ca. 390-380 Ma), Late Carboniferous (ca. 320-300 Ma) and Permian (ca. 280 Ma). Here, Paleozoic granitoids show similar geochemistry and isotopic features. All Paleozoic granitoids plot in the subalkaline field, and predominantly tholeiitic to calc-alkaline series, with enrichment of large-ion lithophile elements and depletion of high-field-strength elements. These granitoids plot in a volcanic arc fields in tectonic discrimination diagrams, which are characteristic of an island arc setting. The fluid inclusions in porphyry and skarn system are characterized by high-temperature, high-salinity, low-content of CO2, whereas epithermal system represented by low-temperature, low-salinity, low-content of CO2, and the VMS system can be described as medium-temperature, medium low-salinity, CO2-bearing fluid. H-O isotopic data suggest that orefluids were sourced from a mixing fluid between magmatic and meteoric water. S-Pb isotopic data show that the sulfur mainly came from magma or ore-hosting igneous rocks. The Yudai porphyry Cu-Au deposit, the Hongshi epithermal Cu deposit and the Honghai Au-rich VMS Cu-Zn deposit formed at the same time related to a subduction environment. The Early Paleozoic VMS mineralization is generally overprinted by late magmatic hydrothermal fluids, which may be due to multiple accretionary orogeny in Kalatag island arc. We propose that the north-dipping subduction of the Paleo-Tianshan Ocean or south-dipping subduction of the Junggar Ocean during Late Ordovician-Silurian, which may led to the development of Yudai porphyry copper, Hongshi epithermal copper and Honghai VMS copper-zinc deposits in the Kalatag arc. After that, north-dipping subduction of the Paleo-Tianshan Ocean resulted to the formation of the Middle Devonian (ca. 390-380 Ma) and Late Carboniferous (ca. 320-300 Ma) Cu mineralization. Finally, the Permian (ca. 280 Ma) magmatic copper-nickel sulfide deposits associated with ultramafic-mafic complexes developed in post-collisional-extension setting, part of a Large Igneous Province (LIP) event associated with mantle plume upwelling.

The relationship between the timing of volcanism and hydrothermal alteration and the geochemistry of magnetite are studied to better understand the metallogeny of the Hongyuntan deposit. The orebodies are hosted in the volcanic rocks with banded or lenticular forms, and main massive, disseminated, and veined ores and subordinate mineralized andesite and dacite host rocks are identified at Hongyuntan. SHRIMP zircon U-Pb dating of dacite and LA-ICP-MS garnet U-Pb dating of skarn yield nearly the same ages of 333.8 +/- 5.3 Ma and 331.0 +/- 6.4 Ma, respectively, indicating an isochronous relationship between volcanic rock and skarn. The age of the diabase dike that crosscuts the orebodies and volcanic strata indicates that the mineralization occurred earlier than 307.6 Ma. The dataset of trace element compositions shows that magnetite grains from stratiform mineralized andesite have high Ti, V, Cr, Ni, Mg, and Sn contents and formed under high-temperature and high-oxygen-fugacity conditions, whereas disseminated magnetite grains from mineralized dacite and chlorite skarn have medium above-element contents, suggesting they were hydrothermally altered under relatively high-oxygen-fugacity and fluid-rock interaction conditions. The fluid mixing and reduced temperature and oxygen fugacity might result in the deposition of massive ores. The increasing Cr, Ni, Mg, and Sn contents in magnetite grains from veined ores and their associated mineral assemblages indicate that overprint mineralization occurred in the Hongyuntan deposit, which was probably caused by multiple periods of volcanic activity or intrusion emplacement. Discrimination plots show that Hongyuntan different magnetite samples have compositions similar to different deposit types and likely formed in magmatic and hydrothermal processes.

The Yamansu deposit, which is hosted in the volcanic-sedimentary sequence of the Carboniferous Yamansu Formation in Eastern Tianshan, NW China, contains many skarns, and the orebodies occur in the ore district in stratoidal, banded or lenticular forms. Four alteration stages, namely, albite–tourmaline–apatite–Grt1 (Stage I), K-feldspar–Grt2 (Stage II), magnetite–chlorite–epidote (Stage III), and quartz–calcite–axinite–Grt3 (Stage IV), are distinguished in the Yamansu deposit. The mineral geochemistry associated with each different stage is presented to provide a better understanding of the corresponding metallogenic processes. The ore-forming fluid in Stage I was derived from a magmatic–hydrothermal source and formed at high temperatures with many volatiles. This ore-forming fluid, which contained considerable metallogenic materials during the early stage, likely experienced diffusive metasomatism in a closed system with low water/rock (W/R) ratios. Mineral geochemical analyses show that the Fe content gradually increases from Stage I to Stage II, indicating that accumulated ore-forming materials were available during changes in the physicochemical conditions from a reducing environment with neutral pH to oxidizing conditions with mildly acidic pH. During the main metallogenic stage (Stage III), mineral assemblages reflect moderate- to high-temperature conditions, and the ore-forming fluid was created and destroyed periodically; the magnetite ores were deposited in a fluctuating fluid system. The multilayered orebodies, multigenerational garnets, and minerals with oscillatory zoning indicate that the ore-forming fluid may have developed periodic fluctuations, and this special multistage fluctuation of the hydrothermal fluid in the Yamansu deposit was the key factor controlling the multiple extraction, enrichment and precipitation of metallogenic materials.

锰质黑柱石是矽卡岩型铅锌矿床中一种常见的脉石矿物,其与铅锌矿体关系密切.本文对东昆仑祁漫塔格地区牛苦头铅锌多金属矿床中黑柱石的产状、矿物共生组合、化学成分等进行了研究.牛苦头矿区锰质黑柱石主要产于3种矿物组合:黑柱石+石榴子石+磁铁矿组合;黑柱石+锰钙(铁)辉石+方铅矿+磁铁矿组合;黑柱石+方解石+石英+硫化物(黄铁矿+磁黄铁矿+其他硫化物)组合,并形成自内向外石榴子石-磁铁矿—黑柱石—锰钙辉石的矽卡岩分带.上述3种组合分别对应矿床的3个蚀变矿化阶段:进变质阶段(阶段I),石榴子石被交代分解,形成黑柱石;退变质阶段(阶段Ⅱ),锰钙(铁)辉石分解形成黑柱石;石英硫化物阶段(阶段Ⅲ),黑柱石进一步分解,形成磁铁矿、方解石和石英.电子探针结果,牛苦头矿床黑柱石的化学分子式为Ca0.94-0.98(Fe1.22-1.92 Mn0.10-0.75 Mg0.01-0.03)2+(2.00-2.05)(Fe0.83-0.93 Al0.01-0.07)3+(0.82-1.03)[Si2.00-2.07 O7]O(OH);LA-ICP-MS原位分析显示,牛苦头矿区黑柱石的稀土配分曲线与矿区进变质阶段形成的石榴子石、锰钙(铁)辉石近乎一致.综合研究认为,矿区黑柱石为进变质阶段的石榴子石和辉石蚀变分解的产物;矿床自内向外的矽卡岩分带反映了矽卡岩被逐渐交代的过程,并伴随了成矿流体从主矽卡岩阶段的"还原(Fe2+、Mn2+)"环境向退变质阶段偏氧化(先是Fe2+-Mn2++Fe3+,后是Fe3+)环境的转变.

The Yamansu iron deposit is hosted in submarine volcanic rocks in the Aqishan–Yamansu belt of Eastern Tianshan, NW China. A geological cross-section for the Carboniferous strata in the ore district shows that ore bodies in the Yamansu deposit are hosted in andesitic crystal tuff of the third cycle of the Carboniferous Yamansu Formation. This indicates an association between mineralization and volcanism. The orebodies are strata bound and lensoid and generally share the occurrence state of the host rocks. Magnetite mineralization mainly occurs asbreccia ores, ores in the mineralized volcanic rocks, massive ores, and sulfide-rich ores according to their structures and sequences of formation. Trace element compositions of magnetite from various types of ores were determined by LA-ICP-MS. The dataset indicates thatdifferent types of magnetite havedistinct trace element contents correlated to their formation environments. Magnetite crystals from breccia ores have high Ti, Ni, V, Cr, and Co and low Si, Al, Ca, and Mg contents, indicating crystallization from a volcanic magmatic eruption, which is consistent with field evidence of coexisting altered volcanic breccia. Magnetite crystals from ores in the mineralized volcanic rocks have moderate Ti, Ni, V, Cr, and Co contents. In contrast, magnetite from massive ores and sulfide-rich ores have low concentrations of Ti, Cr, Ni, and V, high concentrations of Si, Al, Ca, and Mg, and evidence of hydrothermal magnetite. In-situ magnetite compositions imply a magmatic-hydrothermal process. Although δ18O values for magnetite grains fromYamansu vary (+ 1.3 to + 7.0‰), they all plot in the range field of volcanic iron deposits, and they also record a magmatic-hydrothermal process. The compositions of Yamansu magnetites are interpreted as controlled mainly by temperature, fluid, host rock buffering, oxygen fugacity, and sulfur fugacity. The metallogenic conditions of the Yamansu deposit changed from high temperature and low oxygen fugacity to low temperature and high oxygen fugacity. However, more fluid-rock reactions and higher sulfur fugacity were involved during the deposition of massive ores and sulfide-rich ores.

The Yamansu deposit is located in the Aqishan-Yamansu belt of the Eastern Tianshan and is hosted by submarine volcanic rocks (spilite-keratophyre series), which are characterized by high Na2O contents (2.85-7.59 wt%) and Na2O/K2O ratios (1.12-68.20). The Yamansu orebodies feature stratoidal, banded, or lenticular shapes in the spilite-keratophyre series. Four principal stages can be recognized in the Yamansu deposit and the main iron mineralization occurred in Stage III. Microthermometry studies on two types of fluid inclusions indicate that the temperature of ore-forming fluid fluctuated and an additional heat caused by multiple periods of volcanic activity may have incorporated into the ore-forming system. The delta D and delta O-18(fluid) values of the ore-forming fluids in the Yamansu deposit vary broadly from -117.1 parts per thousand to -80.0 parts per thousand and from -17.4 parts per thousand to +14.6 parts per thousand, respectively, indicating a magmatic fluid in the early stage and a mixture of magmatic and meteoric water or seawater in the late stage. The delta C-13(V-PDB) (ranging from-2.5 parts per thousand to +1.1 parts per thousand) and delta O-18(V- SMOW) (ranging from-7.7 parts per thousand to +14.8 parts per thousand) values of calcite reveal that the ore-forming fluids experienced water-rock interactions, which changed the physicochemical conditions of the ore-forming fluids and facilitated the deposition of variable amounts of magnetite and skarn minerals (mainly chlorite and epidote) in Stage III. The wide range of delta S-34 values (-2.9 parts per thousand to +8.5 parts per thousand) of pyrite from the Yamansu deposit indicates that the ore-forming materials mainly involved deeply sourced magmatic sulfur but were affected by mixing with seawater. The geochemical signatures suggest that submarine spilite-keratophyre series favored the formation of the Yamansu iron deposit and these signatures can be applied to the prospecting on the periphery of the Yamansu ore district or in the Aqishan-Yamansu metallogenic belt.

The Chinese East Tianshan is the easternmost sector of the Tianshan Mountain Range in the Central Asian Orogenic Belt (CAOB), and accommodates several events of magmatism, crustal growth and mineralization. The Kalatag arc is unique in the East Tianshan due to its widespread Early Paleozoic volcanic rocks, which offers a special opportunity to study the Early Paleozoic Cu-dominant mineral systems in island arc setting. In this region nine deposits have been discovered in recent years. These deposits occur in Paleozoic volcanic rocks between the Kalatag Fault and Kabei Fault, and can be divided into six mineral systems, i.e., VMS Cu-Zn, epithermal Cu, porphyry Cu-Au, skarn Fe-Cu, magmatic Cu-Ni sulfide and hydrothermally overprinted deposits. Among them, VMS, epithermal, porphyry-skarn and magmatic Cu-Ni sulfide mineralization are distributed in the southeastern, central, northwestern and westernmost Kalatag, respectively. The mineralization and associated intrusive rock ages can be clustered into four episodes in the Kalatag arc, i.e., Late Ordovician-Silurian (ca. 450-430 Ma), Middle Devonian (ca. 390-380 Ma), Late Carboniferous (ca. 320-300 Ma) and Permian (ca. 280 Ma). Here, Paleozoic granitoids show similar geochemistry and isotopic features. All Paleozoic granitoids plot in the subalkaline field, and predominantly tholeiitic to calc-alkaline series, with enrichment of large-ion lithophile elements and depletion of high-field-strength elements. These granitoids plot in a volcanic arc fields in tectonic discrimination diagrams, which are characteristic of an island arc setting. The fluid inclusions in porphyry and skarn system are characterized by high-temperature, high-salinity, low-content of CO2, whereas epithermal system represented by low-temperature, low-salinity, low-content of CO2, and the VMS system can be described as medium-temperature, medium low-salinity, CO2-bearing fluid. H-O isotopic data suggest that orefluids were sourced from a mixing fluid between magmatic and meteoric water. S-Pb isotopic data show that the sulfur mainly came from magma or ore-hosting igneous rocks. The Yudai porphyry Cu-Au deposit, the Hongshi epithermal Cu deposit and the Honghai Au-rich VMS Cu-Zn deposit formed at the same time related to a subduction environment. The Early Paleozoic VMS mineralization is generally overprinted by late magmatic hydrothermal fluids, which may be due to multiple accretionary orogeny in Kalatag island arc. We propose that the north-dipping subduction of the Paleo-Tianshan Ocean or south-dipping subduction of the Junggar Ocean during Late Ordovician-Silurian, which may led to the development of Yudai porphyry copper, Hongshi epithermal copper and Honghai VMS copper-zinc deposits in the Kalatag arc. After that, north-dipping subduction of the Paleo-Tianshan Ocean resulted to the formation of the Middle Devonian (ca. 390-380 Ma) and Late Carboniferous (ca. 320-300 Ma) Cu mineralization. Finally, the Permian (ca. 280 Ma) magmatic copper-nickel sulfide deposits associated with ultramafic-mafic complexes developed in post-collisional-extension setting, part of a Large Igneous Province (LIP) event associated with mantle plume upwelling.