Superlarge Gold Research Articles

Dual-mineralization in the intracontinental Jiangnan Orogen, South China: Evidence from textures and in-situ trace elements and oxygen analysis of quartz from the Woxi Au-Sb-W deposit

The Jiangnan Orogenic Belt (JOB), situated in the interior of the South China Block (SCB), harbors numerous gold-polymetallic deposits, but the ore genesis has been a long-standing controversy. This study examines the Woxi super-large gold deposit in the middle JOB, which is characterized by simultaneous large-scale antimony-tungsten mineralization. The investigation shows that the Woxi ore deposit have developed multiple-stage quartz, i.e., Qz1 (early quartz-carbonate, stage I), Qz2 (quartz-wolframite-scheelite, stage II), Qz3a (quartz-gold-pyrite, early stage III), Qz3b (quartz-stibnite-scheelite, late stage III) and Qz4 (late quartz-carbonate, stage IV). We conducted SEM-CL texture imaging, LA-ICP-MS trace element, and SIMS oxygen isotope analysis on the quartz samples from the main mineralization stages (mainly Qz2 and Qz3). The results reveal a dual mineralization process of the Woxi gold-antimony-tungsten deposit. In the initial stage, the quartz (Qz2) exhibits intense brightness in CL imaging and spiderweb-like texture, shows high concentrations of trace elements, especially Ge, Al and Ti, and has δ18Ofluid values ranging from 10.84 ‰ to 11.64 ‰. These characters are consistent with a magmatic fluid that is acidic (pH<3), reducing, and of relatively high-temperature. In the second stage, the quartz (including Qz3a, Qz3b and Qz4) shows relatively darker CL image and band texture or cobweb mosaic coexistence texture, low concentrations of trace elements, especially Al and Ti, and a low δ18Ofluid values (8.01 ‰ to 9.19 ‰ for Qz3a and 5.83 ‰ to 6.51 ‰ for Qz3b) consistent with characteristics of mantle-derived fluids. The results of this study supports an “intracontinental reactivation metallogenic model”, in which the gold-polymetallic deposits in the JOB formed from a dual-stage mineralization related to tectono-magmatic activities in a back-arc setting. The dual ore-forming processes revealed in this study provide important insights for a comprehensive understanding of the gold-polymetallic deposits in the JOB, and it may be a significant mechanism in the formation of large to super-large gold-polymetallic deposits in this region, which is indicative perspective for exploration of the gold-polymetal deposits. Our work also demonstrates that quartz is an effective tool for identifying the mineralization in the JOB.

Rockburst hazard assessment and prevention and control strategies in the Ruihai gold mine

Ruihai gold mine is a super large underwater gold mine with an initial mining depth of more than 1,400 m. Deep mining may face rockburst disaster. In order to scientifically control the potential rockburst risk, ensure the safety of underground personnel and equipment, and realize the safe and efficient mining of the mine, it is necessary to evaluate the rockburst risk of the mine and formulate appropriate rockburst risk warning and mitigation strategies. XRD mineral composition analysis and conventional rock mechanical tests were carried out on the parent rock granite samples. The results show that there are differences in the lithologic composition and rock mechanics parameters of the three colors of granite, which are preliminarily determined as three kinds of granite; The rockburst tendency of three kinds of granites is evaluated by using three classical rockburst criteria, and the discrimination results of the three rockburst criteria are not completely consistent or even contradictory. The application limitations rockburst risk assessment based on index criteria are discussed and analyzed in detail. It is proposed to apply microseismic monitoring technology to warn and manage the rockburst risk of Ruihai gold mine in development and mining stages, and put forward microseismic monitoring layout schemes and targeted rockburst prevention and control measures in different stages. The research results can provide reference for similar projects.

Fluid evolution and metallogenesis of the Zhangjiapingzi gold deposit in mianning, Sichuan province: constraints from fluid inclusion studies

Introduction: The Zhangjiapingzi gold deposit, located at the western margin of the Yangtze Craton and controlled by the Jinhe-Chenghai deep fault, is a newly discovered super-large gold deposit in the Danba-Mianning metallogenic belt. The gold ore bodies are hosted in the Middle Triassic (T2) altered dolomite (Dm), and have two types of mineralization: altered rock type and quartz vein type. Previous studies on this deposit are rare, especially on the ore-fluid characteristics, which limit the understanding on the ore genesis.Methods: This study focused on fluid inclusions in quartz from altered rocks, and used microthermometry and laser Raman spectroscopy to investigate the properties and sources of ore-forming fluids, and to determine the ore genetic type.Results and discussion: The results show that the fluid inclusions are mainly CO2-H2O-NaCl inclusions, with medium temperature (220–300°C), low salinity (&amp;lt;10%), medium-low density (0.79–1.01 g/cm3) and high contents of CO2 and CH4, resembling typical orogenic gold ore fluids. We suggest that the Zhangjiapingzi is best classified as orogenic type, and our findings provide new insights into the fluid origin and metallogenesis of orogenic gold deposits in the Danba-Mianning metallogenic belt.

Soil Environmental Study Analysis of Mining Areas in the Yangshan Gold Belt,Gansu

The Yangshan gold deposit in Gansu province is a super large gold deposit in the West Qinling metallogenic belt, with a cumulative gold accumulation of 400 tons. The soil environment conditions in Anba- Getiaowan ore section were investigated and analyzed to provide a reference basis for mine construction, development and treatment. A total of 120 samples (95 horizontal profile samples and 25 vertical profile samples) were collected, taking into account the topography, cover type, soil use type and soil type in the study area, and the distribution characteristics and change patterns of soil heavy metals As, Cd, Hg and Pb in the study area were evaluated sterically from both horizontal and vertical dimensions. Meanwhile, the distribution characteristics of F and Se elements in soil were compared and analyzed. The results of the study showed that: (1) the value of heavy metal elements As exceeded the standard, and the rest of the heavy metal elements were above the second grade of soil quality, among which the exceedance rate of heavy metal elements As in Anba area was 15%, and that in Getiaowan area was 84%; (2) the average value of As, F and Se content was higher than the background value of Longnan City, which was speculated to be significantly related to the presence of high arsenic and high fluorine water in the evaluation of poor quality water in the study area; (3) the excessive content of As element in the soil in the mining area is related to the occurrence of arsenic-containing minerals in gold, and As element pollution problem should be emphasized in the later construction and development of the mine.

Petrogenesis and Mo(W) mineralization of deep porphyritic granites in the Laowan ore field, Eastern Qinling, Central China

The Laowan ore field of the Tongbai district is a crucial metallogenic belt within Eastern Qinling, including super large gold (Au) and large molybdenum (Mo) deposits. However, the Au and Mo metallogenic relationship and tectonic setting are still disputed. Petrology, geochemistry, and geochronology were conducted on the 3000 m scientific drilling hole, ZKE1012, south of the Laowan ore field. A concealed porphyritic granite with Mo mineralization was observed at a depth of 1717 m. The concealed porphyry comprises K-feldspar, plagioclase, quartz, biotite and minor magnetite, ilmenite, rutile, apatite, and zircon. Molybdenite, scheelite, pyrite, and chalcopyrite are immersed in the rock as veinlet-dissemination, showing typical porphyry mineralization characteristics. Zircon U–Pb data define that the deep rock was formed at 131.0 ± 2.1 and 133.2 ± 1.0 Ma, consistent with the molybdenite Re–Os age (130 Ma), indicating that the Mo mineralization was related to the porphyry. The rocks are characterized by high silica (SiO2 = 70.5–76.8 wt%), high alkali (Na2O + K2O = 8.55–9.25 wt%), and metaluminous to weakly peraluminous (A/CNK = 0.99–1.09). They are enriched with large ion lithophile elements (Rb, Y, Th, Ce, Sm, and Zr), depleted in Nb, Ba, and Sr, and show negligible Eu anomalies. The deep porphyries belong to I-type granite, and their zircon εHf(t) values are from − 11.2 to − 5.7. Therefore, the concealed porphyritic granite and its mineralization are the product of partial melting of the basements, mixing minor mantle materials caused by the subduction of the Paleo–Pacific Plate to Eurasia in the Early Cretaceous.

Superimposed mineralization in the Tongbai composite orogen, central China: Revealed from geological and geochronological data of the Yindongpo gold deposit

Multi-period mineralizations commonly form superimposed deposits in the orogenic belt, resulting in some disputes about the ore geneses and metallogenic background. Here, we present a comprehensive geological and geochronological study on the Yindongpo super-large gold deposit in the Tongbai composite orogen, central China, to reveal the ages of multi-period gold mineralizations and their links to the complex tectonic evolution framework of the Tongbai orogen. The Yindongpo gold deposit is located in the Weishancheng ore field in the northern segment of the Tongbai orogen and is mainly hosted in the carbonaceous schist of the Waitoushan Formation. Zircon U-Pb dating of leptynite (445 ± 3 Ma) from the Waitoushan Formation shows that it was deposited in the Ordovician, in an island arc or back-arc basin setting during the accretionary orogeny. Orebodies at Yindongpo are strictly controlled by the Zhuzhuang anticline and related fault systems, and are mainly distributed in the turning end, the collapsed part of the dipping end, and the conjugate thrust shear zone of the limbs. Based on field and petrographic observations, two periods of mineralization and four paragenetic stages (stage I to IV) are recognized: the early period consists of the laminated quartz-molybdenite-pyrite stage (I) and laminated-disseminated pyrite stage (II), whereas the late period consists of the quartz-pyrite vein stage (III) and the quartz-polymetallic sulfide vein stage (IV). Molybdenite from stage I has a Re-Os model age of 409 ± 6 Ma, which broadly matches the U-Pb age of intergrown rutile grains (396 ± 4 Ma). These two ages, in combination with the mineralization characteristics, indicate that the early-period gold mineralization was generated by the metamorphism of the accreted terranes during the Early Devonian northward subduction of the oceanic plate. The timing of the late-period mineralization is constrained by the U-Pb age of monazite (127 ± 2 Ma) intergrown with gold-bearing pyrite from stage III and the 40Ar/39Ar ages of ore-related sericite (131 ± 1 Ma) from stage IV and altered sericite (133 ± 1 Ma) from the carbonaceous schist. Combined with the extensive development of coeval granitoids and porphyry Mo deposits in the region, the late-period gold mineralization at Yindongpo belongs to a unified large-scale metallogenic event related to the Early Cretaceous intensive granitic magmatism in an extensional tectonic setting. The results presented here thus reveal two discrete mineralization processes at Yindongpo related to the Tongbai composite orogeny: the early mineralization of Devonian accretionary orogeny and the later mineralization of Cretaceous intracontinental orogeny. Our study contributes to the knowledge of superimposed metallogenesis in composite orogen, and also highlights the decisive role of multi-mineral isotopic dating in revealing the metallogenic epoch of superimposed deposits.

Deep exploration of Jiaodong type gold deposit, taking Shanhou gold deposit, southern part of Zhaoping fault as an example

Crustal response induced by the subduction of Paleo-Pacific Plate, is crucial to study the metallogenic law and prediction of Jiaodong type gold deposit. Gold deposits are preferentially hosted in the lithospheric-scale second-order faults, which provide migration channels, mineralization corridors, and the physicochemical conditions. Super-large gold deposits in northwestern Jiaobei Terrane are generally controlled by regional linear faults, such as Sansandao, Jiaojia, Zhaoping and Qixia faults. However, Zhaoping fault is exposed sporadically (in Xiadian and Jiangjiayao gold deposits) beneath a thick cover of Quaternary basalts, which indicating that limited information can be obtained by traditional geological survey. In this study, high-precision geophysical surveys such as gravity and controlled source audio frequency magnetotellurics (CSAMT) are conducted in the Shanhou gold deposit, which hosted in southern part of Zhaoping fault. Three integrated geophysical profiles results further identified the spatial distribution of second-order oblique-slip faults of Zhaoping fault and established the relationships between brittle deformation and mineralization. The spatial variability of stratum (high density 2.82 g/cm3 and intermediate to high specific resistivity 4000 Ω m), brittle-slip faults (intermediate density 2.73 g/cm3 and low specific resistivity 200 Ω m) and magmatite (low density 2.57 g/cm3 high specific resistivity 8000 Ω m) are identified by two inversion techniques, including the man-machine interactive inversion technology and nonlinear conjugate gradient technology. In addition, the geophysical inversion pseudo sections delicately portray a smooth-out waveform low specific resistivity anomaly, which strongly couples with the spatial ore-hosted locations and enrichment places. The gold mineralized alteration zones generally dips to southeast and the angle changing from 45° to 30°, which are strong coupling with the large-scale acid magmatic intrusion and extensional tectonics occurred in the late Mesozoic. Finally, according to the deep prospecting prediction, a gold ore body with 10 m in thickness was revealed by drilling below the depth of 1,015 m, which is hosting in the brittle deformation of Zhaoping fracture zone.

Deep Insight on the Occurrence Feature of Iron Minerals in a Cyanide Leaching Residue and Its Effective Recovery with Magnetic Separation

The occurrence features of ultrafine iron minerals in a cyanide leaching residue produced from a superlarge gold mining company in Yunnan Province were determined with chemical composition analysis, iron phase analysis, and mineral liberation analysis (MLA). The results show that the residue contains 26.74% iron, mainly occurring in the form of magnetite (26.33%) and limonite (69.41%), in which 67.40% magnetite and 73.00% limonite particles are fully liberated with particle sizes ranging from 9.6 µm to 75.0 µm. The rest are adjacent and wrapped intergrowths. Low-intensity magnetic separation and pulsating high-gradient magnetic separation were, respectively, proposed to recover magnetite and limonite from the residue, and under the optimized conditions, a high-grade magnetite concentrate assaying 64.05% Fe with 85.59% magnetite recovery and a qualified limonite concentrate assaying 50.94% Fe with 54.33% limonite recovery were, respectively, produced. The iron recovery for −30 µm fraction in the magnetite and limonite concentrates reached as high as 51.46%. It was found that the iron recovery for −30µm ultrafine fraction is lower than those of coarser fractions, as a result of the relatively enhanced hydrodynamic drag acting onto the particles, compared with the magnetic force. Entrainment occurs between the ultrafine iron minerals and gangues, thereby reducing the iron grade for the ultrafine fraction. This research outcome would provide a valuable reference for the economic and effective utilization of iron resources from such residues.

A preliminary study of reserve estimate and resource potential assessment of critical elements in the Jiaodong gold deposits, China

通过对大尹格庄和夏甸两个超大型金矿床的精金矿与尾矿砂中关键元素含量的分析，发现相对于华北克拉通地壳元素丰度，本次分析的稀贵元素Co、Rh、Ir和Ru，稀散元素Cd、Te和Se，稀有元素W和In均发生了不同程度的富集；特别是Te、Co和Cd超常富集达到伴生组分综合评价品位。根据伴生有用组分综合评价规范和金矿选矿报告相关参数，分别估算了金矿石和精金矿中可利用的关键金属矿产储量，其中夏甸金矿床内Te储量为69吨（精金矿中52吨）、Co储量为604吨（精金矿中413吨），大尹格庄金矿床内Cd储量为224吨（精金矿中206吨），这些均可直接回收利用。矿物学和矿物化学综合研究表明：Te主体以碲金矿、碲银矿、碲铋矿、碲铅矿和陈国达矿等独立矿物存在，与可见金密切共生；Co常以微量元素形式分布在金成矿早阶段的粗粒黄铁矿和磁黄铁矿中；Cd主要以类质同象的形式赋存于金成矿晚阶段的闪锌矿、黄铁矿和黄铜矿中。进一步通过对典型金矿床中黄铁矿原位和/或单矿物的Te与Co含量对比、并结合矿石中Co与Cd元素组成及其区域地球化学空间分布特征，综合约束了其超常富集特征与资源潜力，揭示新城、玲珑和寺庄金矿床及栖霞异常区分别有约2329吨、1035吨、1553吨和22790吨Co资源量，乳山、新城和焦家金矿床有约1529吨、126吨、216吨Te资源量，仓上、新立、三山岛、寺庄和新城金矿床、以及栖霞和招平北段异常区分别有约47.6吨、78吨、63.7吨、69吨、3564吨、7120吨和696吨Cd资源量；即胶东金矿集区具备近期被综合利用或作为未来潜在接替资源的Co、Te和Cd资源条件，且其展布区域广泛、资源潜力巨大。初步研究已显示胶东具有形成大型-超大型Cd、Te和Co矿床的资源条件，但关键金属资源的空间分布极不均一、其超常富集机理与规律尚不清楚，亟需深入研究。;Through analysis of critical element content in fine gold mine and tailing sands of the two super-large gold deposits of Dayingezhuang and Xiadian, it is found that relative to abundance of elements in crust of the North China Craton, rare and precious elements Co, Rh, Ir and Ru, scattered elements Cd, Te and Se, and rare elements W and In have all been enriched to different degrees; Especially, extreme enrichment of Te, Co and Cd has reached the comprehensive evaluation grade of associated components. According to comprehensive evaluation specifications of associated useful components and relevant parameters of gold beneficiation report, the available critical metal reserves in gold ores and fine gold mines were estimated respectively. The Te reserves in the Xiadian gold deposit are 69 tons (52 tons in fine gold mine), Co reserves are 604 tons (413 tons in the fine gold mine), and the Cd reserves in the Dayingezhuang gold deposit are 224 tons (206 tons in the fine gold mine), all of which can be directly recycled. Mineralogy and geochemistry studies show that Te mainly exists as independent minerals such as gold telluride, silver telluride, bismuth telluride, lead telluride and Chenguoda mineral, and they are closely associated with visible gold; Co is often distributed in the form of trace elements in the coarse-grained pyrite in the early stage of the gold mineralization; Cd mainly occurs in the sphalerite, pyrite and chalcopyrite in the late stage of gold mineralization in the form of isomorphism. Furthermore, by comparing the Te and Co content of pyrite in situ and/or single minerals in typical gold deposits, combined with the elemental composition of Co and Cd in the ore and its regional geochemical spatial distribution characteristics, the extreme enrichment characteristics are comprehensively restricted. The Xincheng, Linglong and Sizhuang gold deposits and the Qixia anomaly area have about 2329 tons, 1035 tons, 1553 tons, and 22790 tons of Co potential resources, respectively, and the Rushan, Xincheng and Jiaojia gold deposits have about 1529, 126, and 216 tons of Te resources, the Cangshang, Xinli, Sanshandao, Sizhuang and Xincheng gold deposits, and the Qixia and northern Zhaoping anomaly areas are about 47.6 tons, 78 tons, 63.7 tons, 69 tons, 3564 tons, 7120 tons and 696 tons of Cd resources, respectively; that is, the Jiaodong gold mining area has the Co, Te, and Cd resource conditions that are comprehensively utilized in the near future or as potential replacement resources in the future, and its spread area is wide and the resource potential is huge. Preliminary studies have shown that Jiaodong has the resource conditions for the formation of super-large Cd deposits, large-scale Te and Co deposits, but the spatial distribution of critical metal resources is extremely uneven, and its extreme enrichment mechanism and law are still unclear, and in-depth research is urgently needed.

Metallogenic age and genesis of the Zhaishang gold deposit in Minxian, Gansu Province

寨上金矿位于西秦岭大规模卡林-类卡林型金矿床集中地之中，是近二十年来探获的又一超大型金矿。通过对寨上金矿的6件矿石样品中的载金矿物黄铁矿进行Rb、Sr、Re、Os同位素分析，获得Rb-Sr、Re-Os等时线年龄分别为273±10Ma、273Ma±22Ma。该数据大于前人所获的二期成矿阶段年龄，在西秦岭已探明的金矿床中尚无报道，反映了寨上金矿更早一期的成矿年龄为273Ma，这也为该区域寻找金矿床拓宽了时间轴。Sr、Os、S同位素及稀土和微量元素研究表明，寨上金矿成矿物质为深源与壳源物质的混合。二叠纪时位于岷礼前陆盆地的吴家山隆起经历了强烈的隆升延展作用，岩浆热液沿断裂通道上升到有较高Au背景值盆地中的褶皱带，使地层中的Au活化富集，在构造有利部位卸载成矿，形成早期寨上金矿床，后期钨矿化及金矿化叠加在早期金矿床之上。寨上金矿第一期金成矿的年龄在时空上与阿尼玛卿洋盆闭合、共和坳拉谷俯冲碰撞、江里沟及中川喜马拉雅型岩体的侵入时间基本吻合，符合“地壳加厚有利于形成金矿床及喜马拉雅型花岗岩与金矿关系密切”的结论，对在该区域寻找同时代金矿床具有一定的指示意义。;Zhaishang gold deposit is located in the concentrated area of large-scale carlin-like gold deposits in West Qinling Mountains, and it is the second super-large gold deposit discovered in the past 20 years. Rb, Sr, Re, Os isotopes of the pyrite, the gold-bearing mineral of Zhaishang gold deposit, in six ore samples were tested in this paper to determine their metallogenic ages and ore-forming materials. The measured Rb-Sr and Re-Os isochron ages of the pyrite are 273±10Ma and 273Ma±22Ma, which are older than the ages of two metallogenic stages of the Zhaishang deposit obtained by the predecessors, i.e., a earlier metallogenic stage (the first stage of 273Ma) might be exist in this area. This new chronological data may broaden the time axis for searching gold deposits in this area since no same metallogenic ages have ever been reported in the explored gold deposits in West Qinling. Furthermore, analyses results of Sr, Os, S isotopes, REE and trace elements compositions indicate that the ore-forming material of the Zhaishang gold deposit is the mixture of deep source and crust source materials. Tectonically, the Wujiashan Rise which is located in the Minli fore-arc basin experienced a strong geothermal uplift and extension in the Late Hercynian Period, which resulted in the hydrothermal fluids rising along the fault channels to the folded belts of the basin with a high Au background, and the activated Au enriched in the formation and unloaded in suitable structural spaces to form the first stage Zhaishang gold deposit. The later two stages of W and Au mineralization superimposed on the early gold deposit. Compared with regional geological evolutionary events, the age of gold mineralization in the first stage of Zhaishang gold deposit is consistent with the time of the closure of the A'nyemaqen ocean basin in the West Qinling, the subduction collision of Gonghe aulacogen, and the intrusion of Jiangligou and Zhongchuan Himalayan-type plutons, which obeys the rule crustal thickening is conducive to the formation of gold deposits and Himalayan granites are closely related to gold deposits. It is of indicative significance for searching contemporary gold deposits in this area.

Two episodic Au–Mo mineralization in the Laowan district from the Tongbai orogenic belt of China: Constraints from U–Pb dating of zircon, rutile, and REE phosphate, and Re–Os dating of molybdenite

The Laowan super-large (208 t Au) gold deposit is located in the Tongbai orogenic belt, along with a newly-discovered molybdenite deposit at its depth in the northern periphery. The gold deposit is a fault-controlled lode gold deposit featuring sulfide quartz vein-type and altered rock-type mineralization hosted within the metamorphic rocks, whereas the molybdenum deposit is a typical porphyry-type deposit. These two deposits have their respective paragenetic sequences and mineralization types without spatial overlapping in the ore field. Here, we present U–Pb dating of zircon, hydrothermal rutile, and REE phosphates, and Re–Os dating of molybdenite to constrain the relationship between the Au and Mo mineralization, and their relation to Mesozoic granitic magmatism. Textural features indicate that rutiles and associated phosphate minerals are of hydrothermal origin, generated by re-precipitation and dissolution of titanite crystals hosted in the metamorphic host rocks due to hydrothermal alteration during Au and Mo mineralization. LA-ICP-MS U–Pb dating of rutile from the auriferous altered rocks yields a 206Pb/238U age of 120.0 ± 6.7 Ma (MSWD = 1.4), consistent with the ages of the associated monazite (125.0 ± 2.4 Ma) and xenotime (126.3 ± 2.0 Ma), representing the timing of the gold mineralization, coeval with Laowan monzogranite (zircon U–Pb: 128.8 ± 0.7 Ma). Rutile from the molybdenum deposit show an older 206Pb/238U age of 141.0 ± 11 Ma (MSWD = 1.1), consistent with the molybdenite Re–Os age (141.5 ± 1.7 Ma; MSWD = 0.27) and the zircon U-Pb age (141.6 ± 0.8 Ma; MSWD = 1.5) of the Songpa porphyry. Hence, the Au and Mo mineralization in the Laowan district represent two episodic mineralization events related to the late Mesozoic granitic magmatism. Our study also suggested that multiple isotopic dating is helpful to precisely constraint the ages for complex hydrothermal deposits.

Large and super-large orogenic golden deposits: Geodynamics, structure, genetic consequences

Research subject.Large and super-large orogenic gold deposits are widely distributed across all continents. This work was aimed at characterizing 24 giant facilities with reserves and resources of more than 500 tons of metal.Materials and methods.The work was based on the authors’ long-term fieldwork research into large and super-large gold deposits in Central Asia and the North-East of the Russian Arctic. In addition, an extensive bibliographic analysis of publications devoted to the largest gold deposits in the world was carried out.Results. A structural analysis showed that the formation of these deposits underwent two main stages. The early – subduction stage – was characterized by the development of gentle disturbances, such as thrusts, thrust nappies, viscous discontinuities and crushing zones, while the structural paragenesis included isocline lying folds and cleavage of the axial surface. The second stage – collision-transpression – began with the deformation of the previously formed structure into open and compressed folds with steep axial surfaces; as a result of further compression, a series of longitudinal discontinuous disturbances developed. An oblique collision of interacting plates lead to the development of shear transpression structural paragenesis, in which oblique cracks predominate. It is established that, in orogenic gold deposits, different stages were characterized by ore-controlling and ore-bearing structures. The binding of ore-bearing disturbances to different stages enabled isolation of deposits of various types that differ in structural and morphological features. The main characteristics of the identified types of deposits are provided. The formation of these deposits occurred during convergent processes, with the ore-controlling structures being a surface manifestation of the movement of block terrains along the surface of the detachment.Results.It is concluded that the surface of the detachment is not only a tectonic zone, but also a channel that provides a link between various deep levels of the subduction zone, from where ore-bearing hydrothermal fluids emerge.

Gravity and magnetic field characteristics and regional ore prospecting of the Yili ancient continent, West Tianshan, Xinjiang Uygur Autonomous Region, China

ABSTRACT Gold, iron, copper, lead-zinc and other mineral exploration in West Tianshan, Xinjiang Uygur Autonomous Region, has made remarkable progress in recent years. However, due to the dispute on the tectonic division of West Tianshan, the ore-controlling factors and the regional metallogenic laws are controversial. The authors analyze regional gravity data and notice that the high-value region corresponds to the Yili ancient continent, thus the southeastern boundary of the Yili ancient continent is delineated. Comparative analysis of gravity, aeromagnetic and geologic data reveals that the Tulasu basin, where some medium to large epithermal gold deposits locate, lies above the Yili ancient continent; the Yili Carboniferous-Permian rift extends in E-W direction, numbers of copper deposits have been found in the mid-west section of the rift which lies above the Yili ancient continent, whereas few copper deposits have been discovered in the east section which is outside the Yili ancient continent. Accordingly, the Yili ancient continent may he rich in gold, copper and other metal elements; the metal-bearing hydrothermal solution moves up with the activity of magmatism, and deposits in the favorable places (the Tulasu basin and the Yili Carboniferous-Permian rift), forming numerous small and medium gold, copper deposits, as well as some large and super-large gold deposits. Therefore, the tectonic-magmatic hydrothermal zone above the Yili ancient continent should be the prospective area for epithermal gold and copper polymetallic deposits.

The Thermal and Dynamic Process of Core → Mantle → Crust and the Metallogenesis of Guojiadian Mantle Branch in Northwestern Jiaodong

The Jiaodong gold mineral province, with an overall endowment estimated as &gt;3000 t, located at the eastern segment of the North China Craton (NCC), ranks as the greatest source of Au in China. The structural evolution, magmatic activity and metallogenesis during the Mesozoic played important roles in the large scale regional gold, silver and polymetallic mineralization in this area; among them, the intensive activation of fault structures is the most important factor for metallogenesis. This study takes the regional deep faults as main thread to discuss the controlling role of faults in large scale metallogenesis. The Jiaojia fault and Sanshandao faults in the northwest margin of the Guojiadian mantle branch not only are dominant migration channels for hydrothermal fluid but are very important favorable spaces for ore-forming and ore-hosting during the formation of world-class super large gold deposits in this area. The deep metallogenic process can be summarized as involving intensive Earth’s core, mantle and crust activity → magmatism → uplifting of metamorphic complex → detachment of cover rocks → formation of mantle branch → penetration of hydrothermal fluid along deep faults → concentration of metallogenic materials → formation of super large deposits.

Geological study and significance of typical gold deposits in eastern Qinzhou-Hangzhou metallogenic belt: Constraint from Tianjingshan gold deposit in south Anhui Province

The eastern part of Qinzhou-Hangzhou metallogenic belt, including Jiangxi, Anhui and Zhejiang province, is located in the southeastern Jiangnan Orogen. A large amount of copper‑gold polymetallic deposits are distributed in the belt, represented by Jinshan super-large gold deposit in Jiangxi province, Tianjingshan large gold deposit in Anhui province and Huangshan medium gold deposit in Zhejiang province.The LA-ICP-MS U-Pb zircon dating for Lingshan and Hanjia intrusions of Tianjingshan gold deposit yield 794.7 ± 5.2 Ma and 765.9 ± 3.7 Ma, respectively, indicating they are all formed in the Jinningian. According to the different geochemical characteristics and field features, Hanjia intrusion shouldn't be altered by Lingshan intrusion, and was not formed in Yanshanian. The Ar-Ar analyses of chlorite for gold-bearing mylonite yield a spectrum age of 331.5 ± 3.2 Ma, firstly identifying Hercynian metallogenic event. The sulfur isotopes of pyrites from gold-bearing quartz veins show that the metallogenic fluids are complex, maybe metamorphic fluids mixed with meteoric water or magmatic water. Integrating with previous studies, Tianjingshan orogenic-type gold deposit with multiple stages and large time span of mineralization is formed by the collision-amalgamation of Yangtze block and Cathaysia block, which the Jinningian is the period of initial gold enrichment, and the Hercynian is an important metallogenic period.Based on contrastive analyses, these three typical gold deposits have similar metallogenic process as follows: the gold rich materials are derived from Neoproterozoic strata and Jinningian intrusion; then the ore-bearing metamorphic fluids resulted from regional metamorphism are mixed with meteoric water or magmatic water, and results in ore-bearing fluids enriched in CO2 and depleted in salinity; finally, the gold in the fluids is enriched in the low degree thrusting brittle- ductile shear zone due to the change of temperature, press and other conditions controlled by the fault. Therefore, these typical gold deposits were directly relate to the collision- amalgamation of Yangtze block and Cathaysia block and have a large time span of mineralization, which the altered-rock type gold deposit was formed at the Jinningian while the quartz vein type gold deposit was formed in Hercynian. Comprehensively, Tianjingshan gold deposit has the typical features of orogenic gold deposit. Significantly, the orogenic type gold deposit can provide important guidance and experience on deep and regional mining exploration.

Dyke swarms and their role in the genesis of world-class gold deposits: Insights from the Jiaodong peninsula, China

Jiaodong peninsula, located at the southeastern margin of the North China Craton, is well known for its rich endowment of super-large gold deposits. This region is also characterized by hundreds of intermediate – mafic dykes that cluster into several dyke swarms. In this study, we present zircon U-Pb ages which show that the timing of dyke emplacement as ca. 120Ma, which followed the crystallization of the (quartz-) diorite porphyry at ca. 130Ma. These ages coincide with the peak ages reported for magmatism and metallogeny in the central North China Craton. The various ages (2450–2570 and 154Ma) from the inherited zircon crystals in these rocks suggest that substantial lower to middle crustal basement rocks and Jurassic granitoids were involved during dyke emplacement. The dyke swarms, varying between alkaline and subalkaline, are compositionally low-Si low-Ti lamprophyre and low-Si high-Ti dolerite porphyry in the western of the Jiaodong peninsula, whereas those in the eastern part are composed of both high-Si low-Ti and low-Si high-Ti lamprophyres. These features imply multiple sources for the dykes from convective asthenospheric mantle to ancient enriched lithospheric mantle with magma generation at different depths involving mixture of slab-derived hydrous fluids. The source magmas of the dykes were hydrous and enriched in volatiles as well as ore components, and their evolution occurred under high oxygen fugacity conditions. The relatively rapid emplacement and cooling of the dyke systems enabled the migration of fluids into ore-controlling faults or fractures. We envisage that the dyke swarms played an important role in generating the world-class gold mineralization of Jiaodong.

Geochemistry Characteristics of Nibao Super Large Gold Deposits from Guizhou Province, China and its Geologic Significance

Geochemistry Characteristics of Nibao Super Large Gold Deposits from Guizhou Province, China and its Geologic Significance

Re-Os dating of auriferous pyrite from the Zhenyuan super-large gold deposit in Ailaoshan gold belt, Yunnan Province, Southwestern China

Zhenyuan gold deposit is the largest super large gold deposit in the Ailaoshan gold belt, but its precise mineralization age is still lack. Re-Os isotopic age of the auriferous pyrite from the Zhenyuan gold deposit was determined by using a high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS). The pyrite samples were decomposed in carius tubes, Os was separated by distillation and Re was extracted by acetone, respectively. The results show that the Re-Os isochron age is 229±38 Ma (MSWD=2.0, confidence level is 95%), with an initial 187Os/188Os value of 0.68±0.24 and a corresponding γOs value of 442±91. The Re/Os ratios of the pyrite vary from 40.8 to 100.5. The data suggest that at least one important ore-forming event was occurred during Indosinian epoch, and the ore-forming materials probably derived from mixed sources of crustal and mantle, while the later dominated. The Ailaoshan composite orogen experienced complicated evolutional processes, including formation of Precambrian-Early Paleozoic basement, subduction and orogenesis of Late Paleozoic era, collisional orogenesis of Late Hercynian-Indosinain epoch, and extensional or striking orogenesis of Yanshainan-Cenozoic epoch. The polycycle tectonic evolution and magmatism in this area caused multi-stage and superposition metallization characteristics of the Zhenyuan gold deposit: the mineralization probably occur mainly during the Indosinian collisional orogeny, while the minor gold ores of altered granite-porphyry and altered lamprophyre may be formed in the late superposition metallization.

Geological Characteristics and Prospecting Orientation of the Altered Rock Type Gold Deposits in Southeastern Guizhou Province, China

The altered rock type gold deposit is the one type gold deposits which can form super-large gold deposit. The super-large altered rock type gold deposit has its specialties among the forming time, forming generation, ore-hosted strata, wall rock alteration, area and structure. The southeast Guizhou Province has wonderful minerogenetic conditions. The area has the similar minerogenetic geological setting as many large, super-large altered rock type gold deposits. The characteristics of the altered rock type gold deposits that are distributed in this area have many similarities with other large, super-large altered rock gold deposits. It indicates that the deep of the southeast of Guizhou Province altered rock type gold metallogenic belt has great prospecting potentiality for looking for such type gold deposits from ore-hosted strata, ore-control structure, mineral paragenesis and ore-forming temperature etc.

The Mesozoic granitoid magmatism and metallogeny of the Central Asian and Pacific Belts junction area

Materials pertaining to Mesozoic granitoids in the Central Asian and Pacific Belts junction area and the adjacent platforms are summarized. Maps of the location of massifs, the extensiveness of granitoid magmatism, the manifestations of Mesozoic plumes, and the relief of the asthenosphere surface have been compiled. The locations of the major ore deposits are plotted on the maps. The distribution chart has been constructed for these deposits in the coordinates of the crust and lithosphere. The depth of the occurrence of the sources for large and superlarge gold, tin, polymetallic, molybdenum, tungsten, and uranium deposits has been estimated. Areas showing promise for the discovery of large deposits are defined.