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1.
The Chertovo Koryto gold deposit(80 t Au at 1.84 g/t) in the Lena world-class province,Siberia,is hosted in a metamorphosed sequence of the Paleoproterozoic Mikhailovsk Formation that comprises the oldest black shale strata of the Baikal-Patom region.The mineralisation is confined to the thrust zone complicated with a conjugate anticline fold,zones of shearing and dislocation.The struaural position of the mineralisation is similar to that at the giant Sukhoi Log deposit in the neighbouring Mama-Bodaibo zone.In the latter,the isotope age data suggest that Khomolkho black shales,hosts to Sukhoi Log mineralisation,are of Ediacaran age and underwent prograde metamorphism during early Paleozoic.The geochemical composition of the terrigenous rocks that host Sukhoi Log,Chertovo Koryto,and a number of other deposits at the various stratigraphic levels throughout the Proterozoic sequence have much in common.They do not show elevated metal contents above the common black shale abundances,except for Au and As,which is at variance with the accepted view on diagenetic enrichment of black shales in the Lena province.The occurrence of sagenitic rutile in quartz and chlorite pseudomorphs after biotite and other petrographic observations provide evidence on a retrograde nature of the metamorphic mineral assemblages in the Mikhailovsk rocks.The sulphides are pyrrhotite and arsenopyrite with very minor pyrite at Chertovo Koryto,whereas pyrite is the predominant sulphide in the Sukhoi Log ore.Fluid inclusion data on both deposits emphasise a high-temperature nature of the mineralisation albeit revealing great contrast in the fluid composition.Sukhoi Log mineralisation was formed at mixing between low-salinity aqueous solutions and dense gaseous carbonic fluids,which facilitated effective gold scavenging and precipitation,as demonstrated by thermodynamic simulation.The precursory devolatilisation of the Mikhailovsk sediments at the prograde stage results in the paucity of gaseous carbonic fluid during retrograde metamorphism and mineralisation.The similarity in the styles and chemical parameters of mineralisation,and the predominant structural control of ore localisation within the same Precambrian regional tectonic unit support an idea that orogenic gold mineralisation in the Lena province was produced during a single early Paleozoic event.  相似文献   

2.
Sukhoi Log is one of the largest gold deposits in Russia (1100 t Au at 2.45 g/t). Like many other sediment-hosted gold deposits throughout the world, Sukhoi Log preserves textural, structural and geochemical evidence for multiple generations of Au enrichment and pyrite growth.The deposit is located in the Lena gold province of Siberia, on the edge of the Siberian Craton and occurs in the core of a recumbent anticline in a Neoproterozoic black shale and quartz-rich siltstone-sandstone turbidite succession. Temporal constraints on pyrite paragenesis at the deposit have been determined using laser ablation inductively coupled mass spectrometry (LA-ICPMS) measurements of U, Th and Pb isotopes in pyrite, monazite and zircon. LA-ICPMS age determinations on detrital zircons indicate the host rocks were deposited after 600 ± 10 Ma and derived from a mixture of Palaeoproterozoic and Neoproterozoic sources. The U, Th and Pb isotopic systematics indicate the cores of large monazite crystals, which predate obvious tectonic fabric development in the host rocks, began growing at 573 ± 12 Ma. The rims of the same monazite crystals formed at 516 ± 10 Ma, during peak metamorphism and deformation. Small monazite crystals also grew in the sedimentary rocks during the Devonian (374 ± 20 Ma) and the Carboniferous or Early Permian (288 ± 22 Ma), possibly in response to fluid movements triggered by synchronous granite intrusion in the area. Multi-collector and quadrupole LA-ICPMS Pb isotopic determination on pyrite, combined with overprinting criteria, show that the earliest (stratiform) Pb and Au-bearing pyrite formed prior to metamorphism—possibly during sedimentation or early diagenesis (575-600 Ma). Small Au-rich pyrite nodules preserved as cores to folded bedding-parallel pyrite-quartz veins probably grew during late diagenesis or early metamorphism. Large pyrite euhedra, which overgrow the strong axial planar cleavage in the host rocks, have more radiogenic Pb-isotopic compositions and formed either late during or after deformation. Framboidal pyrite that is overgrown by both the late diagenetic-early metamorphic and syn- to post-metamorphic pyrite has the most radiogenic Pb-isotopic composition suggesting exchange with radiogenic Pb in the matrix may have continued until late in the history of the deposit.The dating and Pb isotopes support a multistage origin for the gold deposit with Au first introduced during or prior to growth of the earliest stratiform pyrite and progressively re-concentrated (with or without addition of further gold) during later metamorphic events.  相似文献   

3.
新疆北部中——大型金、铜矿床的基本成矿特征   总被引：1，自引：0，他引：1       下载免费PDF全文
通过对新疆北部10多个中－大型金、铜矿床的对比研究，探讨了其含矿建造及其岩石化学成分，将这些中－大型金、铜矿床概括为块状硫化物型铜－多金属－金矿系列、浅成低温热液型金矿系列、铜镍硫化物型矿床系列、与韧性剪切带有关的构造蚀变岩型金矿系列、与夕卡岩有关的铜（钼）矿床系列等5个成矿系列类型、并指出本区金、铜矿床存在“一代，双峰”和“集中成矿，分片富集”的时空分布特点；在探讨有关典型矿床的硫同位素、铅同位素、稀土元素地球化学特征的基础上，阐述了本区中－大型金、铜矿床具有明显的多成矿物质来源和多成矿阶段等基本特性；最后建立了本区中－大型金、铜矿床的区域成矿模式。  相似文献   

4.
The relationships between the δ18O of quartz veins and veinlets pertaining to the main stage of gold mineralization at the Sukhoi Log deposit and metasomatically altered host slates are estimated. The oxygen isotopic composition of veined quartz and host slates is not uniform. The δ18O of quartz veins from the Western, Central, and Sukhoi Log areas of the deposit vary from +16 to + 18 ‰. The δ18O range of metasomatically altered slates in the Western and Sukhoi Log areas attains 6 ‰. The δ18O of quartz veins are always higher than those of host slates by 3–7‰. The regular difference in the δ18O between quartz veins and host slates indicates that the oxygen isotopic composition of the ore-bearing fluid forming the system of quartz veins and veinlets at the Sukhoi Log deposit could have formed as a result of interaction with silicate rocks, for instance, terrigenous slates enriched in δ18O. Such interaction, however, took place at deeper levels of the Sukhoi Log deposit. It is suggested that the fluid phase participating in the formation of the vein and veinlet system had initially high δ18O(>+10‰) due to interaction with the rocks enriched in δ18O at a low fluid/rock ratio. The oxygen isotope data indicate that the fluid participating in the formation of gold mineralization at the Sukhoi Log deposit was not in equilibrium with igneous rocks at high temperatures.  相似文献   

5.
The typomorphic features of pyrite of the Sukhoi Log deposit were studied by a set of volumetric and surface methods: electron probe microanalysis, scanning electron and probe microscopy, powder X-ray diffraction, X-ray photoelectron and Auger electron spectroscopy, atomic-absorption spectrometry in the SSADSC (method of statistical sample of analytical data for single crystals) version, and atomic-emission spectrometry. Pyrite from the Sukhoi Log deposit has the following distinctive features: permanent presence of sulfite ion, which often dominates over other surface sulfur anions; weakly determined size dependence of the content of uniformly distributed Au owing to the presence of an internal concentrator of gold—dispersed carbonaceous material—in pyrite from ore zones; cell sculptures of the crystal faces, which appeared owing to the nanofragmentation of the growth surface; micro- and nanoinclusions of carbonaceous phases within crystals, associated with defects in their structure; and thin films enriched in O and C on the surface of and within the crystals. It has been shown that gold-sulfide mineralization at the Sukhoi Log deposit formed in a single ore-generating hydrothermal system, in which gold, sulfur, and carbon belonged to a microparagenesis. Some features (composition of surface, characteristics of submicroscopic structure, and elemental composition) evidence that the conditions of crystallization of pyrite in inter-ore space were different from the conditions of its genesis in the ore zones, which suggests the presence of at least two genetic types of pyrite. Carbonaceous micro- and nanoparticles and O- and C-containing films can favor an increase in the adsorption of gold from cyanide solutions on pyrite. To reduce this effect during gold recovery, a technique for surface modification should be elaborated. The ways for solving the most complicated problems dealt with the source of noble metals (NM) and the ore specialization of the deposit have been outlined. For this purpose, a detailed analysis of the main ore minerals for trace-element speciation is required. In the case of the magmatic source of NM, correlation between the contents of Au and PGE structural forms should exist. On the other hand, there is no correlation between the structural forms of Au or Pt and elements whose contents in fluid are determined by the host rock rather than the magmatic source.  相似文献   

6.
Determining the source of sulfur in an ore deposit is key to understanding the nature of the ore forming processes. The Neoarchaean Paulsens sediment-hosted gold deposit (∼1 Moz @ 7.6 g/t) located in the Pilbara Craton of Western Australia exhibits many of the characteristics of Phanerozoic shale hosted gold deposits (e.g. Huijiabao Trend, Northern Carlin Trend and Sukhoi Log), in that 1) black shales are the dominant host rock, 2) gold is hosted in pyrite as both free gold and dissolved gold in the lattice of the pyrite, and 3) multiple generations of pyrite have formed due to a variety of geological processes. In this contribution we utilised Secondary Ion Mass Spectrometer (SIMS) to measure the in-situ quadrupole (32S, 33S, 34S and 36S) sulfur isotope compositions of the different generations of pyrite. Our results indicate that the both diagenetic and hydrothermal pyrite generations display similar and anomalous Δ33S signatures (up to +0.4‰). Further, the Δ33S-Δ36S arrays in the hydrothermal pyrite generations lie on a slope which is similar to that of the diagenetic pyrite. These data support the hypothesis that the sulfur in the ore zones came from the host Hardey Formation black shales.We also performed trace element analyses of syn-sedimentary and early diagenetic pyrite from the Hardey Formaiton using Nano Secondary Ion Mass Spectrometry (NanoSIMS), Electron Probe Microanalysis (EPMA) and Laser Ablation-inductively coupled plasma-mass spectrometry (LA-ICPMS), all of which show that the syn-sedimentary and early diagenetic pyrite contain high concentrations of many trace elements (As, Ni, Co, Cu, Ag, Se, Te, Bi), including up to 1.5 ppm Au. These metals contents are also abundant in the several generations of mineralised hydrothermal pyrite and form clear patterns of growth associated with couple dissolution reprecipitation reactions. These findings clearly indicate that the fluid that transported the Au must have also been enriched in the base and precious metals that are contained in the early, syn-diagenesis pyrite.Data from this study clearly support the hypothesis that in some sediment-hosted gold systems, all the sulfur and gold required to form the deposit are sourced from the local sedimentary package. By using the presence of anomalous mass independent sulfur isotope signatures as chemically conservative and indelible tracers, it is possible to fingerprint the source of sulfur in a wide range of mineral systems, thus enhancing predictive exploration strategies at the regional to camp scales.  相似文献   

7.
The mixing of gas and aqueous fluid in hydrothermal ore-forming processes is discussed with reference to gold deposits to demonstrate that this phenomenon may affect ore deposition. Data on fluid inclusions in samples from the Sukhoi Log and Olimpiadinskoe deposits in Russia are utilized to demonstrate possible implications of gas mixing with hydrothermal solution when gold ores are formed. A simplified thermodynamic model is suggested to show how interaction between aqueous saline solutions with pure carbon dioxide or carbon dioxide—methane mixture may affect gold solubility. Further studying such processes may provide interesting information for understanding the genesis of ore mineralization.  相似文献   

8.
A lot of new gold deposits have been found on the eastern margin of the Qinghai-Tibet Plateau during the past two decades. Among them, three main types of gold deposits have been recognized, including quartz-vein-type, shearzone-type and porphyry-type. The former two types of gold deposits are mainly hosted within metamorphic rocks, while the latter is related to Cenozoic magmatism. Although all of these gold deposits are believed to have been formed during the uplift process of the Qinghai-Tibet Plateau in the Cenozoic era (Wang et al., 2002b), precise isotopic age constraints have still been lacking until quite recently. This paper presents new ^40Ar/^39Ar data of some gold deposits on the eastern margin of the Qinghai-Tibet Plateau, which indicate that gold mineralization in the region occurred in response to the episodic stages of the orogenies. Recently obtained ^40Ar/^39Ar data on quartz and feldspars from several gold deposits, such as the Sandiao deposit, the Baijintaizi deposit, the Pusagang deposits, provide new constraints on gold mineralization on the eastern margin of the Qinghai-Tibet Plateau. Geochronological studies of gold deposits along the Daduhe River indicate that there are three stages of gold mineralization. The early two stages occurred as early as 65.1 Ma in the Shuibaiyang deposit and 58.95 Ma in the Ruoji deposit, while the latter stage occurred as late as 25.35 Ma in Baijintaizi and 24.70 Ma in Sandiao. Isotopic dating of three plagioclases from the Beiya deposit, Zhifanggou deposit and Luobodi deposit and a K-feldspar from the Jinchangqing deposit in Yunnan Province indicates that these deposits were formed at two stages. The Zhifanggou and Jinchangqing deposits have early stage records as old as 58.82 Ma in Zhifanggou and 55.49 Ma in Jinchangqing, but all of the above four deposits in Yunnan have late stage records of 23.18 Ma in Jinchangqing, 24.54 Ma in Zhifanggou, 24.60 Ma in Luobodi and 24.56 Ma in Hongnitang. The above results suggest that the gold deposits on the eastern margin of the Qinghai-Tibet Plateau were formed concentratedly at two main episodes, i.e. the end of the Paleocene (about 58 Ma) and the boundary between the Paleogene and the Neogene (about 25 Ma). The later episode appears to be looks like more important and was coupled with the Sichuan movement, which was extensively activated at that period. The beginning of the Cenozoic Era (about 65 Ma) might be another episode of gold mineralization, but only one deposit (Shuibaiyang) in this study has been proved to have been be formed at this stage and might be earlier than the initial collision between the Indian Plate and the Eurasia Plate. In view of geology, the above three episodes of gold mineralization are associated with three events of tectonicmagmatism and/or fluid events. Even though the gold deposits (for example, the Shuibaiyang deposit, Ruoji deposit and Pusagang deposit) were formed at different episodes, all of them are genetically related to tectonic movements in largescale shear zones. It looks like theat tectonic events (including large-scale strike-slip) between Paleogene and Neogene had a wide influence upon gold mineralization, with new deposits formed and old deposits enriched or superimposed to be a higher grade by new stage of mineralization. The above data suggest that gold deposits were not only concentrated in some areas, but also formed mainly at different boundaries of geological times, indicating that there existed some peak stages of gold mineralization (metallogenic episodes), and that the gold deposits were formed mainly by episodic mineralization.  相似文献   

9.
The lead isotopic composition of 33 sulfide samples from orebodies of the Sukhoi Log deposit was studied by high-precession MC-ICP-MS with a precision of ±0.02% (±2SD from 120 analyses of the SRM 981 standard sample). The deposit is located in the Bodaibo gold mining district in the northern Baikal-Patom Highland. Gold mineralization is hosted in Neoproterosoic black slates. Variations of lead isotope ratios of the Sukhoi Log sulfides are generally typical of Phanerozoic deposits and ore fields. They are significant for 206Pb/204Pb (17.903–18.674), moderate for 208Pb/204Pb (37.822–38.457), and relatively narrow for 207Pb/204Pb (15.555–15.679). In the Pb-Pb isotope diagrams, the data points of pyrite and galena constitute a linear trend. The points corresponding to pyrite from metasomatic ore occupy the left lower part of the trend. Galena from late gold-quartz veins shows more radiogenic Pb, and corresponding data points are located in the upper part of the trend. According to the Stacey-Kramers model, the end points of the trend, which is regarded as a mixing line, have μ2 = 9.6 and μ2 = 13.2 and model Pb-Pb ages 455 and 130 Ma, respectively. The isotope characteristics of ore lead, their relationships in pyrite and galena, and the mixing trend of Pb isotopic compositions are clearly tied to two Paleozoic stages in the formation of the Sukhoi Log deposit (447 ± 6 and 321 ± 14Ma) and testify to the leading role of crustal sources, which are suggested as being the Neoproterozoic black-shale terrigenous-carbonate rocks.  相似文献   

10.
The Lena gold district is situated in the fold-and-shear belt of the southern framework of the Siberian Platform. The gold deposits are hosted in the Riphean-Vendian Khomolkho and Aunakit formations, revealing the strict control of ore mineralization by folding and shearing. The microstructure of metasomatically altered ore-bearing carbonaceous sedimentary rocks at the Sukhoi Log, Golets Vysochaishy, and Verninsky deposits (the latter includes the Pervenets vein zone) testifies to parallelism in the development of shearing, foliation, and ore-forming metasomatism. The local pressure gradients are marked by removal of silica from pressured zones into opened cleavage fractures and pockets. Two metasomatic stages are recognized: (1) early sodic metasomatism, which is characterized by the assemblage of magnesian siderite and paragonite, and (2) late potassic metasomatism, with formation of muscovite in association with sideroplesite and ankerite. The rocks altered at the early stage are distinguished by elevated Ni, Cr, and probably PGE contents. The second stage, close in age to the emplacement of Hercynian granitic plutons, was accompanied by the gain of chalcophile metals and deposition of the bulk of gold. In mineral composition, the metasomatic rocks are close to beresites, but the alteration differed in somewhat elevated alkalinity, so that microveinlets of albite and potassium feldspar occur in the ore zone together with muscovite. The ratio of modal muscovite to paragonite contents in orebodies is substantially higher than in the surrounding metasomatized rocks. This ratio directly depends on the degree of rock permeability and the intensity of the flow of ore-forming solutions. Carbonaceous matter (CM) in the ore zone underwent reworking and redeposition. CM is graphitized to a lesser extent than in the rocks affected by regional metamorphism. The spatial distribution of CM containing nitro and amino groups indicates more oxidizing conditions in the zone of ore deposition than at a distance from this zone. The temperature of metasomatic processes estimated from the muscovite, muscovite-paragonite, and chlorite mineral thermometers and fluid inclusions in quartz was 300–350°C at a pressure of about 1 kbar. The S, O, and C isotopic compositions of ore-forming fluids that pertain to the second stage of metasomatism (δ34S= +8.5‰, δ18O = +10‰, and δ13C= ?11 to ?18‰) indicate their crustal origin. The generally similar conditions and products of the ore-forming metasomatic process at the giant Sukhoi Log deposit and at the small Golets Vysochaishy deposit are combined with some differences. The formation of the described deposits was related to the deep convection of fluids along shear zones followed by more local flows of postmagmatic solutions derived from the emplaced granitic magma.  相似文献   

11.
隐爆角砾岩筒型金(铜)矿床作为重要的金矿床类型,常伴生关键金属碲的矿化,然而对于此类矿床中碲的分布、分配特征及沉淀机制研究仍较为薄弱。黄屯矿床是长江中下游成矿带近年来发现的最为典型的隐爆角砾岩筒型金铜矿床,伴生有大量的碲化物产出。本文在详细的野外地质工作和岩相学观察基础上,发现碲在矿床中发生了显著富集。通过对黄屯矿床不同蚀变类型矿石及主要富碲矿物开展全岩及微区地球化学分析,明确了碲的分布、分配特征以及初步讨论了碲的沉淀机制。黄屯矿床成矿阶段从早到晚可划分为钠钙硅酸盐、钾硅酸盐、绿泥石-碳酸盐和伊利石-蒙脱石阶段,在不同深度形成了相应的蚀变带,并发育有不同强度的金铜矿化。黄屯矿床伴生的碲储量约有118.71t,平均品位为5.3g/t,达到中型规模,具备重要的综合利用价值。钾硅酸盐蚀变带碲的分布比例最高,占总储量约92.37%,平均品位约为9.6g/t。钾硅酸盐蚀变带内约有89%~99%的碲呈独立矿物,主要以微米级、纳米级的碲铋矿包体的形式分布在黄铁矿中,剩余部分则以类质同象的形式赋存在黄铁矿和黄铜矿内。减压沸腾引起流体温度骤降导致硫化物沉淀,和沸腾过程中释放大量气相H_(2)S,共同导致流体的f(Te_(2))/f(S_(2))比值升高,可能是黄屯矿床中碲沉淀富集的主要机制。  相似文献   

12.
漠滨脆—韧性剪切带型金矿床控矿构造研究   总被引：4，自引：0，他引：4  
层间右旋逆冲脆—韧性剪切带构造控制漠滨金矿床。剪切带变形过程经历了早、中、晚3个阶段。而金矿化的形成和富集又与剪切带多阶段的演化密切相关,金矿化是剪切构造作用形成的。因此,剪切带既是控矿因素,又是重要的成矿机制,属层间逆冲脆—韧性剪切带型金矿床。  相似文献   

13.
中国西北地区中亚型造山—成矿作用的研究意义和进展   总被引：57，自引：0，他引：57  
地处欧亚大陆核心的中亚型造山带,由多条古生代缝合带与多个前寒武纪小陆块镶嵌,基此 形成 中新生代盆地—山脉耦合的构造格局,并具有独特的构造演化史和动力学机制。中亚型造山 作用造就了丰富的矿产资源,矿床类型多样,超大型矿床汇聚,是解决我国21世纪矿产资源 问题的关键地带。但目 前尚未查明其成矿规律、成矿机制和找矿方向,因而急需研究。  相似文献   

14.
This study of the behavior of trace and rare earth elements in ores from the Natalka gold deposit allows us to draw several conclusions. It is suggested that ore formation is related to the regional metamorphism of the host terrigenous carbonaceous rocks, which could be the major source for trace and rare earth elements. Minor enrichment of the Natalka ores in W is evidence of the contribution of magmatic fluid, which could be superimposed on early quartz veins, in ore formation. Our results support the metamorphic–magmatic model of formation of economic gold–quartz deposits of the Yana–Kolyma Belt. The similarity of metasomatites of the Natalka deposit with disseminated gold–sulfide refractory ores from the Nezhdaninskoe and Bakyrchik deposits points to the possible presence of such ores in the Natalka deposit. Our data are important for forecasting regional metallogenic reconstructions, search, and evaluation of gold deposits.  相似文献   

15.
The deposition of finely disseminated gold in the deposits hosted in black shales is considered. It is suggested that gold deposition is controlled by microstructure of pore space in host rocks. The pore space structure of tight shales indicates that most pore volume is occupied by nanopores with hundredths of micrometers in characteristic dimension. The balance calculations show that deposition of native gold in nanopore channels of filtration is hampered by shortage of number of atoms necessary to overcome a nucleation threshold of the future gold crystal in the pore volume. When ore-transporting solution meets on its way the cavities (pores, micro- and macrofractures), whose volume is sufficient to overcome the nucleation threshold, the excess content of ore component, which exceeds equilibrium concentration, is released with formation of crystallization centers and further precipitation of gold. The conditions of ore deposition are exemplified in the reference Sukhoi Log deposit hosted in black shales. On the basis on the PT conditions of ore deposition and physical features of fluid heat and mass transfer, it is suggested that ore disseminations were deposited at the early high-temperature stage under a fluid pressure close to lithostatic and at a host rock permeability markedly exceeding its present-day value.  相似文献   

16.
The Baguamiao superlarge gold deposit in Shaanxi Province is one of the typical cases in China that are hosted by sedimentary rocks. Explorers and researchers have discussed the gold mineralization enrichment conditions by studying sulphur, oxygen, carbon, silicon stable isotopes and mineralizing fluid features of the Baguamiao gold deposit and proposed a hydrothermal sedimentation-magmatic reconstructing gold mineralization model featuring multi-sources of ore-forming materials and multistage mineralizations. In addition, prospecting for "Baguamiao-type" gold deposits was started in the Fengtai Basin and a great number of important prospecting targets such as Tonglinggou, Simaoling, Guoansi and Dachaigou were discovered.  相似文献   

17.
Northern Nevada hosts the only province that contains multiple world-class Carlin-type gold deposits. The first-order control on the uniqueness of this province is its anomalous far back-arc tectonic setting over the rifted North American paleocontinental margin that separates Precambrian from Phanerozoic subcontinental lithospheric mantle. Globally, most other significant gold provinces form in volcanic arcs and accreted terranes proximal to convergent margins. In northern Nevada, periodic reactivation of basement faults along this margin focused and amplified subsequent geological events. Early basement faults localized Devonian synsedimentary extension and normal faulting. These controlled the geometry of the Devonian sedimentary basin architecture and focused the discharge of basinal brines that deposited syngenetic gold along the basin margins. Inversion of these basins and faults during subsequent contraction produced the complex elongate structural culminations that characterize the anomalous mineral deposit “trends.” Subsequently, these features localized repeated episodes of shallow magmatic and hydrothermal activity that also deposited some gold. During a pulse of Eocene extension, these faults focused advection of Carlin-type fluids, which had the opportunity to leach gold from gold-enriched sequences and deposit it in reactive miogeoclinal host rocks below the hydrologic seal at the Roberts Mountain thrust contact. Hence, the vast endowment of the Carlin province resulted from the conjunction of spatially superposed events localized by long-lived basement structures in a highly anomalous tectonic setting, rather than by the sole operation of special magmatic or fluid-related processes. An important indicator of the longevity of this basement control is the superposition of different gold deposit types (e.g., Sedex, porphyry, Carlin-type, epithermal, and hot spring deposits) that formed repeatedly between the Devonian and Miocene time along the trends. Interestingly, the large Cretaceous Alaska–Yukon intrusion-related gold deposits (e.g., Fort Knox) are associated with the northern extension of the same lithospheric margin in the Selwyn basin, which experienced an analogous series of geologic events.  相似文献   

18.
汪在聪  王焰  汪翔  程怀  许喆 《地球科学》2021,46(12):4197-4229
交代岩石圈地幔与大型金矿床之间的成因联系受到越来越多的关注.研究成矿金属在地幔源区的富集程度和幔源岩浆中的金含量,以及金从地幔源区释放、迁移并大规模富集成矿的机制和过程可以帮助我们更好地认识交代岩石圈地幔对金富集成矿的重要作用.金是高度亲铜元素,同时还具有流体活动性,在地幔岩浆作用、岩浆热液演化和富集成矿等诸多过程中的行为较为复杂.主要从金的地球化学行为出发,通过梳理金在各类地幔岩石和幔源岩浆中的分布,以及岩浆热液中金的主要行为及其受控因素,探讨交代岩石圈地幔对巨量金成矿的关键控制机制.主要认识包括:（1）交代岩石圈地幔可能是形成大规模热液型金矿床的重要源区,但金在源区的异常富集可能并不是成矿的必要条件;（2）地幔交代组分（特别是挥发分）有助于金从地幔源区中有效释放、并通过跨岩石圈尺度的深大断裂迁移富集;（3）富挥发分的岩浆热液中金的富集沉淀过程远比一个富金的地幔源区对大规模金成矿作用的贡献更大.因此,深刻理解岩石圈地幔长期演化过程中金在地幔交代和岩浆-热液演化过程中的行为与富集机制是解析大型金矿床成因的关键.   相似文献   

19.
秦岭造山带金属矿床的“二元控矿”特征   总被引：21，自引：2，他引：19  
秦岭造山带是我国重要的有色金属和贵金属成矿带,对其研究表明,多数金属矿床具有成矿物质多源、成矿时代多期、矿床成因复杂等共性特征,但是这些矿床一般受早期初始富集成矿和晚期造山改造就位的二元因素控制,矿床的富集空间主要为断裂构造、褶皱虚脱部位和印支-燕山期侵入体内外接触带.在总结秦岭造山带金属矿床成矿规律的基础上,我们提出秦岭造山带金属矿床的"二元控矿"作用,旨在总结关键控矿因素,指导区域找矿勘查.  相似文献   

20.
乐华—德兴成矿带成矿作用研究的进展,问题及展望   总被引：8，自引：1，他引：7  
张德会 《地质论评》1998,44(5):502-510
赣东北乐华－德兴成矿带位于江南地块东南缘,带内有超大型的德兴斑岩铜矿床,金山金矿床,银山多金属矿床以及许多中小型矿床,其中铜储量和伴生金储分别占全国的１７．５％和３７％,深入研究乐华－德兴成矿带内典型矿床和区域成矿作用,对深刻揭示大型－超大型矿床的成因矿床分带的形成机理以及发展中国的金属成矿学理论等都有重要意义,本文讨论了近年来对该成矿带成矿作用的研究进展,存在问题,并对研究前景作了展望。  相似文献   

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