闽西南地区大地构造演化和矿床时空分布规律

在充分吸收前人工作成果的基础上,讨论了闽西南地区的主要矿床类型及其特征,将闽西南地区的矿床划分为三个矿床成矿系列:晋宁期与海相火山作用有关的铅、锌、银多金属块状硫化物矿床成矿系列;海西-印支期与火成岩有关的铁、铜、铅、锌多金属矿床成矿系列;燕山期与中酸性火成岩有关的铁、铜、铅、锌、钼、钨、锡、金、银、铀等多金属矿床成矿系列。其中,与燕山期有关的矿床成矿系列可进一步划分为侏罗纪早期与壳幔混合源I型花岗闪长岩有关的铁、铜、铅、锌矿床成矿亚系列;侏罗纪晚期与壳源S型花岗质岩体有关的钨、锡、钼、铋多金属矿床成矿亚系列;早白垩世与壳源型中酸性侵入岩有关的层控矽卡岩型铁、铜、铅、锌、钼多金属矿床成矿亚系列;早白垩世与壳幔混合源型中酸性侵入岩-次火山作用有关的金、银、铜、钼、铅、锌、铀等多金属矿床成矿亚系列。总结研究提出了各成矿(亚)系列的形成背景、时空分布规律,初步认为晋宁期VMS型多金属矿床形成于华南联合陆块拉张裂解形成的政和-大埔海底双峰式火山盆地环境,海西-印支期岩浆热液-斑岩型金属矿床形成于陆内伸展与挤压环境交替出现的岩浆侵入过程中,而燕山期成矿(亚)系列则形成于太平洋构造域时期的陆内伸展与挤压环境交替出现的岩浆侵入与火山喷发的过程中。     

Isotopes and Geochronology of the Meixian-type Pb-Zn-(Ag)Deposits,Central Fujian Rift,South China:Implications for Geological Events

Central Fujian Rift is another new and important volcanogenic massive sulfide Pb-Zn polymetallic metallogenetic belt. In order to find out the material genesis and mineralization period of Meixian-type Pb-Zn-Ag deposits, S and Pb isotope analysis and isotope geochronology of ores and wall rocks for five major deposits are discussed. It is concluded that the composition of sulfur isotope from sulfide ore vary slightly in different deposits and the mean value is close to zero with the 834S ranging from -3.5‰ to ＋5.6‰ averaging at ＋2.0‰, which indicates that the sulfur might originate from magma or possibly erupted directly from volcano or was leached from ore-hosted volcanic rock. The lead from ores in most deposits displays radioactive genesis character （206pb/204pb〉18.140, 207Pb/204pb〉15.584, 208pb/204pb〉38.569） and lead isotope values of ores are higher than those of wall rocks, which indicates that the lead was likely leached from the ore-hosted volcanic rocks. Based on isotope data, two significant Pb-Zn metallogenesis are delineated, which are Mid- and Late-Proterozoic sedimentary exhalative metailogenesis （The single zircon U-Pb, Sm-Nd isochronal and Ar-Ar dating ages of ore- hosted wall rocks are calculated to be among 933-1788 Ma.） and Yanshanian magmatic hydrothermal superimposed and alternated metallogenesis （intrusive SHRIMP zircon U-Pb and Rb-Sr isochronal ages between 127-154 Ma）.     

Cadmium and sulfur isotopic compositions of the Tianbaoshan Zn–Pb–Cd deposit,Sichuan Province,China

Although Zn–Pb deposits are one of the most important Cd reservoirs in the earth, few studies have focused on the Cd isotopic fractionation in Zn–Pb hydrothermal systems. This study investigates the causes and consequences of cadmium and sulfur isotope fractionation in a large hydrothermal system at the Tianbaoshan Zn–Pb–Cd deposit from the Sichuan–Yunnan–Guizhou (SYG) metallogenic province, SW China. Moderate variations in Cd and S isotope compositions have been measured in sphalerite cover a distance of about 78 m. Sphalerite has δ^114/110Cd values ranging from 0.01 to 0.57‰, and sulfides (sphalerite, galena and chalcopyrite) have δ³⁴S_CDT values ranging from 0.2 to 5.0‰. Although δ³⁴S_CDT and δ^114/110Cd values in sphalerites have no regular spatial variations, the δ³⁴S_CDT values in galena and calculated ore-forming fluid temperatures decreased from 2.1 to 0.2‰ and from about 290 to 130 °C, respectively, from the bottom to the top of the deposit. Heavy Cd isotopes are enriched in early precipitated sphalerite in contrast to previous studies. We suggest that Cd isotopic compositions in ore-forming fluids are heterogeneous, which result in heavy Cd isotope enrichment in early precipitated sphalerite. In comparison with other Zn–Pb deposits in the SYG area, the Tianbaoshan deposit has moderate Cd contents and small isotope fractionation, suggesting differences in origin to other Zn–Pb deposits in the SYG province.In the Tianbaoshan deposit, the calculated δ³⁴S∑_S-fluids value is 4.2‰, which is not only higher than the mantle-derived magmatic sulfur (0 ± 3‰), but also quite lower than those of Ediacaran marine sulfates (about 30 to 35‰). Thus, we suggest that reduced sulfur of ore-forming fluids in the deposit was mainly derived from the leaching of the basement, which contains large amount of volcanic or intrusive rocks. Based upon a combination of Cd and S isotopic systems, the Tianbaoshan deposit has different geochemical characteristics from typical Zn–Pb deposits (e.g., the Huize deposit) in SYG area, indicating the unique origin of this deposit.     

Geology and Geochemistry of the Bianbianshan Au‐Ag‐Cu‐Pb‐Zn Deposit,Southern Da Hinggan Mountains,Northeastern China

The Bianbianshan deposit, the unique gold-polymetal (Au-Ag-Cu-Pb-Zn) veined deposit of the polymetal metallogenic belt of the southern segment of Da Hinggan Mountains mineral province, is located at the southern part of the Hercynian fold belt of the south segment of Da Hinggan Mountains mineral province, NE China. Ores at the Bianbianshan deposit occur within Cretaceous andesite and rhyolite in the form of gold-bearing quartz veins and veinlet groups containing native gold, electrum, pyrite, chalcopyrite, galena and sphalerite. The deposit is hosted by structurally controlled faults associated with intense hydrothermal alteration. The typical alteration assemblage is sericite + chlorite + calcite + quartz, with an inner pyrite - sericite - quartz zone and an outer seicite - chlorite - calcite - epidote zone between orebodies and wall rocks. δ34 S values of 17 sulfides from ores changing from –1.67 to +0.49‰ with average of –0.49‰, are similar to δ34 S values of magmatic or igneous sulfide sulfur. 206Pb/204Pb, 207Pb/204Pb and 208Pb/ 204Pb data of sulfide from ores range within 17.66–17.75, 15.50–15.60, and 37.64–38.00, respectively. These sulfur and lead isotope compositions imply that ore-forming materials might mainly originate from deep sources. H and O isotope study of quartz from ore-bearing veins indicate a mixed source of deep-seated magmatic water and shallower meteoric water. The ore formations resulted from a combination of hydrothermal fluid mixing and a structural setting favoring gold-polymetal deposition. Fluid mixing was possibly the key factor resulting in Au-Ag-Cu-Pb-Zn deposition in the deposit. The metallogenesis of the Bianbianshan deposit may have a relationship with the Cretaceous volcanic-subvolcanic magmatic activity, and formed during the late stage of the crust thinning of North China.     

Distinctive features of Late Palaeozoic massive sulphide deposits in South China

More than 20 sediment-hosted massive sulphide deposits occur in Late Palaeozoic basins in South China. These deposits are accompanied by a certain amount of volcanic rocks in the host sequence and are economically important for their Cu, Pb, Zn, Au and Ag reserves. The deposits and their host strata were commonly intruded by Mesozoic granitoids. Remobilisation of sedimentary ores and magmatic hydrothermal overprinting processes resulted in the coexistence of massive sulphides with vein-, skarn- and porphyry-type orebodies in the same region or within a single deposit. The ore-containing basins occur in different tectonic settings. The Lower Yangtze basin occurs on a passive continental margin, where the deposits are high in Cu and Au with minor Pb and Zn and recoverable Ag, Co and Mo. The ores have a lower concentration of radiogenic lead, and δ³⁴S values close to zero. Fluid inclusions are highly saline and Na-rich. Fluids and metals of the Lower Yangtze Region are interpreted to have been derived essentially from deep sources including the Precambrian basement. By contrast, basins of the Nanling Region formed in an intracontinental setting developed on a folded Caledonian basement. These deposits are higher in Pb, Zn, Sn and W, as well as Cu, with recoverable Ag, Sb, Hg, U, Bi, Tl and Mo. The ores are characterised by a higher concentration of radiogenic lead and a wide variation of δ³⁴S composition. Fluid inclusions have lower salinities and higher K⁺/Na⁺ ratios. Fluids are considered to have been sourced substantially from seawater by convection. Metals for the Nanling deposits were essentially derived from the Caledonian basement by leaching. The contrast in ore composition between these two regions appears to have been controlled by differences in basement composition of the ore-forming basins.     

Types,features, and prospecting potential for Mesozoic metal ore deposits in Zhejiang Province,southeast China

The geotectonic units of Zhejiang Province include the Yangtze Plate in the northwest juxtaposed against the South China fold system in the southeast along the Jiangshan–Shaoxing fault. The South China fold system is further divided into the Chencai–Suichang uplift belt and the Wenzhou–Linhai geotectogene belt, whose boundary is the Yuyao–Lishui fault. The corresponding metallogenic belts are the Mo–Au(–Pb–Zn–Cu) metallogenic belt in northwest Zhejiang, the Chencai–Suichang Au–Ag–Pb–Zn–Mo metallogenic belt, and the coastal Ag–Pb–Zn–Mo–Au metallogenic belt. The main Mesozoic metal ore deposits include epithermal Au–Ag(Ag), hydrothermal vein-type Ag–Pb–Zn(Cu), and porphyry–skarn-type Mo and vein-type Mo deposits. These ore bodies are related to the Mesozoic volcanic-intrusive structure: the epithermal Au–Ag(Ag) deposits are represented by the Zhilingtou Au–Ag deposit and Houan Ag deposit and their veins are controlled by volcanic structure; the hydrothermal vein-type Ag–Pb–Zn deposits are represented by the Dalingkou Ag–Pb–Zn deposit and also controlled by volcanic structure; and the porphyry–skarn-type Mo deposits are represented by the Tongcun Mo deposit and the vein-type Mo deposits are represented by the Shipingchuan Mo deposit, all of which are related to granite porphyries. These metal ore deposits have close spatio-temporal relationships with each other; both the epithermal Au–Ag(Ag) deposits and the hydrothermal vein-type Ag–Pb–Zn deposits exhibit vertical zonations of the metallic elements and form a Mo–Pb–Zn–Au–Ag metallogenetic system. These Jurassic–Cretaceous deposits may be products of tectonic-volcanic-intrusive magmatic activities during the westward subduction of the Pacific Plate. Favourable metallogenetic conditions and breakthroughs in the recent prospecting show that there is great resource potential for porphyry-type deposits (Mo, Cu) in Zhejiang Province.     

The Ordovician igneous rocks with high Sr/Y at the Tongshan porphyry copper deposit,satellite of the Duobaoshan deposit,and their metallogenic role

A strong link between high Sr/Y arc magmas and porphyry Cu–Mo–Au deposits has been recognized in recent years. The Tongshan and Duobaoshan deposits are representative large Cu–Mo–Au deposits in NE China. We report LA–ICP–MS zircon U–Pb crystallization age of 471.5 ± 1.3 Ma for Tongshan ore-related granitoid. Re–Os isotopic analyses of the two chalcopyrite samples from Tongshan deposit show a model age range of 470.2–477.1 Ma. The Duobaoshan and Tongshan ore-related granitoids show higher Sr/Y and La/Yb ratios. The δ³⁴S values of sulphides from the Duobaoshan and Tongshan deposits vary from −2.3‰ to 0.0‰, belonging to a magmatic-hydrothermal system. The Pb isotopic ratios of the sulphides from the Duobaoshan and Tongshan deposit range from 17.201 to 18.453 for ²⁰⁶Pb/²⁰⁴Pb, 15.445 to 15.551 for ²⁰⁷Pb/²⁰⁴Pb, and 36.974 to 37.999 for ²⁰⁸Pb/²⁰⁴Pb, indicating the addition of lower crustal material. The Duobaoshan and Tongshan granitoids were formed in a subduction-related continental arc setting, produced by partial melting of juvenile hydrous basalts underplating the deep continental crust during the Ordovician.     

S,Pb, and Sr isotope geochemistry and genesis of Pb–Zn mineralization in the Huangshaping polymetallic ore deposit of southern Hunan Province,China

The Huangshaping Pb–Zn–W–Mo polymetallic deposit, located in southern Hunan Province, China, is one of the largest deposits in the region and is unique for its metals combination of Pb–Zn–W–Mo and the occurrence of significant reserves of all these metals. The deposit contains disseminated scheelite and molybdenite within a skarn zone located between Jurassic granitoids and Carboniferous sedimentary carbonate, and sulfide ores located within distal carbonate-hosted stratiform orebodies. The metals and fluids that formed the W–Mo mineralization were derived from granitoids, as indicated by their close spatial and temporal relationships. However, the source of the Pb–Zn mineralization in this deposit remains controversial.Here, we present new sulfur, lead, and strontium isotope data of sulfide minerals (pyrrhotite, sphalerite, galena, and pyrite) from the Pb–Zn mineralization within the deposit, and these data are compared with those of granitoids and sedimentary carbonate in the Huangshaping deposit, thereby providing insights into the genesis of the Pb–Zn mineralization. These data indicate that the sulfide ores from deep levels in the Huangshaping deposit have lower and more consistent δ³⁴S values (− 96 m level: + 4.4‰ to + 6.6‰, n = 13) than sulfides within the shallow part of the deposit (20 m level: + 8.3‰ to + 16.3‰, n = 19). The δ³⁴S values of deep sulfides are compositionally similar to those of magmatic sulfur within southern Hunan Province, whereas the shallower sulfides most likely contain reduced sulfur derived from evaporite sediments. The sulfide ores in the Huangshaping deposit have initial ⁸⁷Sr/⁸⁶Sr ratios (0.707662–0.709846) that lie between the values of granitoids (0.709654–0.718271) and sedimentary carbonate (0.707484–0.708034) in the Huangshaping deposit, but the ratios decreased with time, indicating that the ore-forming fluids were a combination of magmatic and formation-derived fluids, with the influence of the latter increasing over time. The lead isotopic compositions of sulfide ores do not correlate with sulfide type and define a linear trend in a ²⁰⁷Pb/²⁰⁴Pb vs. ²⁰⁶Pb/²⁰⁴Pb diagram that is distinct from the composition of the disseminated pyrite within sedimentary carbonates and granitoids in the Huangshaping deposit, but is similar to the lead isotopic composition of sulfides within coeval skarn Pb–Zn deposits in southern Hunan Province. In addition, the sulfide ores have old signatures with relative high ²⁰⁷Pb/²⁰⁶Pb ratios, suggesting that the underlying Paleoproterozoic basement within southern Hunan Province may be the source of metals within the Huangshaping deposit.The isotope geochemistry of sulfide ores in the Huangshaping deposit shows a remarkable mixed source of sulfur and ore-forming fluids, and the metals were derived from the basement. These features are not found in representative skarn-type Pb–Zn mineralization located elsewhere. The ore-forming elements (S, Pb, and Zn) from the granitoids made an insignificant contribution to sulfide precipitation in this deposit. However, the emplacement of granitoids did provide large amounts of heat and fluids to the hydrothermal system in this area and extracted metals from the basement rocks, indicating that the Jurassic magmatism associated with the Huangshaping deposit was crucial to the Pb–Zn mineralization.     

Spatial–temporal evolution of ore-forming fluids and related mineralization in the western Lanping basin,Yunnan Province,China

The Lanping basin is a significant Pb–Zn–Cu–Ag mineralization belt in the Sanjiang Tethyan metallogenic province. A series of sediment-hosted Himalayan Cu–Ag–Pb–Zn polymetallic deposits have been discovered in the western part of the basin, controlled by a thrust–nappe system. In the thrust–nappe system, the Cu orebodies mainly occur in the western and relatively deep part of the mineralization system (the root zone), whereas the Pb–Zn–Ag (± Cu) orebodies occur in the eastern and relatively shallow part of the system (the front zone), both as vein-type mineralization.In this paper we present new data, combined with existing data on fluid inclusions, isotopes and geologic characteristics of representative deposits, to provide the first study that contrasts mineralizing fluids in the Cu–Ag (Mo) and Pb–Zn–Ag (Cu) polymetallic deposits.Fluid inclusion and isotope studies show that the Cu–Ag (Mo) mineralization in the root zone formed predominantly from deep crustal fluids, with the participation of basinal brines. The deep crustal fluids are marked by high CO₂ content, relatively high temperatures (280 to 340 °C) and low salinities (1 to 4 wt.% NaCl equivalent), whereas the basinal brine shows relatively low temperatures (160 °C to 220 °C) and high salinities (12 to 22 wt.% NaCl equivalent), containing almost no CO₂. In comparison, hydrothermal activity associated with the Pb–Zn–Ag (± Cu) deposits in the front zone is characterized by basinal brine, with relatively low temperatures (130 °C to 180 °C), high salinities (9 to 24 wt.% NaCl equivalent), and low CO₂ concentrations. Although evolved meteoric waters have predominantly been proposed as the source for deep crustal fluids, magmatic and metamorphic components cannot be completely excluded. The basinal brine was predominantly derived from meteoric water.The δ³⁴S values of sulfides from the Cu–Ag (Mo) deposits and Pb–Zn–Ag (± Cu) deposits range from − 17.9 to 16.3‰ and from 2.5 to 11.2‰, respectively. These ranges may relate to variations in physicochemical conditions or compositional variation of the sources. Lead isotope compositions indicate that the ore-forming metals were predominantly derived from sedimentary rocks of the Lanping basin.     

Source Diversity of Ore Sulfur from Mesozoic-Cenozoic Mineral Deposits in the Korean Peninsula Region

Abstract: Sulfides from the Daebo Jurassic granitoids and some ore deposits from Korean Peninsula and Sikhote Alin occurring in different basement settings were analyzed for δ³⁴S values. Highly positive values were obtained from Jurassic Mo skarn deposit at Geumseong of the Ogcheon belt (average +13. 0%), Au‐quartz vein deposits at Unsan, North Korea (+6. 7%), and late Paleozoic Sn‐F deposit at Votnesenka (+8. 2%), Khanka massif, Russia. Together with published data of that region, regional variation of δ³⁴S values is shown across Korean Peninsula. Sulfur isotopic data published are compiled on 88 ore deposits, whose mineralization epochs belong to Cretaceous (58 deposits), Jurassic (25 deposits) and Precambrian (4 deposits) in South Korea. Average sulfur isotopic values vary across South Korea as follows: Cretaceous deposits in the Gyeongsang basin, +4. 8% ranging +1.2 ? +12.7‰ (n=28); Jurassic and Cretaceous deposits in the Sobaegsan massif, +3. 5% ranging 0.0 ? +7.8‰ (n=20); those of the Ogcheon belt, +6. 4% ranging ‐0.5 ? +15.4‰(n=19); those of the Gyeonggi massif, +5. 5% ranging +2.1 ? +9.0‰(n = 21). The δ³⁴S values of South Korea tend to be concentrated around +5. 5 permil, exhibiting little, if any, a systematic variation across the geotectonic belts. This tendency is seen also in North Korea and Northeast China within the Cino‐Korean Block, and may be called as Cino‐Korean type. Sulfur of this type is derived mostly from the crystalline basement. Khanka massif of Russia seems to have features of the Cino‐Korean type. In contrast, paired positive/negative belts corresponding to magnetite‐series/ilmenite‐series granitic belts are overwhelming in the Japanese Islands, especially in Southwest Japan. The similar trend is also seen in southern Sikhote Alin and northern Okhotsk Rim, which may be called as Japanese type. Source of the sulfur in this type is likely in the subducting oceanic slab for positive value and accreted sedimentary complex for the negative value, respectively. The Daebo granitoids have an average rock δ³⁴S value of +5. 3 permil, which should have reflected that of the source rocks in the continental crust. The ore sulfur heavier than this value may have been originated in other granitoids having even higher δ³⁴S values, or the ore fluids interacted directly with sulfate sulfur of the host evaporites or carbonate rocks. Rock isotopic values of granitoids and basement rocks need to be examined in future from the above point of view in mind.     

Unique Origin of Skarn at the Ohori Base Metal Deposit,Yamagata Prefecture,NE Japan: C,O and S Isotopic Study

The Ohori ore deposit is one of the Cu–Pb–Zn deposits in the Green Tuff region, NE Japan, and consists of skarn‐type (Kaninomata) and vein‐type (Nakanomata) orebodies. The former has a unique origin because its original calcareous rocks were made by hydrothermal precipitation during Miocene submarine volcanism. Carbon and oxygen isotope ratios of skarn calcite and sulfur isotope ratios of sulfides were measured in and around the deposit. Carbon and oxygen isotope ratios of the skarn calcite are δ¹³C = ?15.51 to ?5.1‰, δ¹⁸O = +3.6 to +22.5‰. δ¹³C values are slightly lower than those of the Cretaceous skarn deposits in Japan. These isotope ratios of the Kaninomata skarn show that the original calcareous rocks resemble the present submarine hydrothermal carbonates at the CLAM Site, Okinawa Trough, than Cenozoic limestones, even though some isotopic shifts had occurred during later skarnization. δ³⁴S ratios of the sulfide minerals from the Kaninomata and Nakanomata orebodies are mostly in a narrow range of +4.0 to +7.0‰ and they resemble each other, suggesting the same sulfur origin for the both deposits. The magnetite‐series Tertiary Kaninomatasawa granite is distributed just beneath the skarn layer and has δ³⁴S ratios of +7.5 to 8.1‰. The heavy sulfur isotope ratio of the skarn sulfides may have been affected by the Kaninomatasawa granite.     

U–Pb and Re–Os Geochronology of the Tongcun Molybdenum Deposit and Zhilingtou Gold‐Silver Deposit in Zhejiang Province,Southeast China,and Its Geological Implications

Mesozoic ore deposits in Zhejiang Province, Southeast China, are divided into the northwestern and southeastern Zhejiang metallogenic belts along the Jiangshan–Shaoxing Fault. The metal ore deposits found in these belts are epithermal Au–Ag deposits, hydrothermal‐vein Ag–Pb–Zn deposits, porphyry–skarn Mo (Fe) deposits, and vein‐type Mo deposits. There is a close spatial–temporal relationship between the Mesozoic ore deposits and Mesozoic volcanic–intrusive complexes. Zircon U–Pb dating of the ore‐related intrusive rocks and molybdenite Re–Os dating from two typical deposits (Tongcun Mo deposit and Zhilingtou Au–Ag deposit) in the two metallogenic belts show the early and late Yanshanian ages for mineralization. SIMS U–Pb data of zircons from the Tongcun Mo deposit and Zhilingtou Au–Ag deposit indicate that the host granitoids crystallized at 169.7 ± 9.7 Ma (2σ) and 113.6 ± 1 Ma (2σ), respectively. Re–Os analysis of six molybdenite samples from the Tongcun Mo deposit yields an isochron age of 163.9 ± 1.9 Ma (2σ). Re–Os analyses of five molybdenite samples from the porphyry Mo orebodies of the Zhilingtou Au‐Ag deposit yield an isochron age of 110.1 ± 1.8 Ma (2σ). Our results suggest that the metal mineralization in the Zhejiang Province, southeast China formed during at least two stages, i.e., Middle Jurassic and Early Cretaceous, coeval with the granitic magmatism.     

Genesis of the Jurassic Carbonate‐Hosted Pb–Zn Deposits of Jebel Ressas (North‐Eastern Tunisia): Evidence from Mineralogy,Petrography and Trace Metal Contents and Isotope (O,C, S,Pb) Geochemistry

The Jebel Ressas Pb–Zn deposits in North‐Eastern Tunisia occur mainly as open‐space fillings (lodes, tectonic breccia cements) in bioclastic limestones of the Upper Jurassic Ressas Formation and along the contact of this formation with Triassic rocks. The galena–sphalerite association and their alteration products (cerussite, hemimorphite, hydrozincite) are set within a calcite gangue. The Triassic rocks exhibit enrichments in trace metals, namely Pb, Co and Cd enrichment in clays and Pb, Zn, Cd, Co and Cr enrichment in carbonates, suggesting that the Triassic rocks have interacted with the ore‐bearing fluids associated with the Jebel Ressas Pb–Zn deposits. The δ¹⁸O content of calcite associated with the Pb–Zn mineralization suggests that it is likely to have precipitated from a fluid that was in equilibrium with the Triassic dolostones. The δ³⁴S values in galenas from the Pb–Zn deposits range from ?1.5 to +11.4‰, with an average of 5.9‰ and standard deviation of 3.9‰. These data imply mixing of thermochemically‐reduced heavy sulfur carried in geothermal‐ and fault‐stress‐driven deep‐seated source fluid with bacterially‐reduced light sulfur carried in topography‐driven meteoric fluid. Lead isotope ratios in galenas from the Pb–Zn deposits are homogenous and indicate a single upper crustal source of base‐metals for these deposits. Synthesis of the geochemical data with geological data suggests that the base‐metal mineralization at Jebel Ressas was formed during the Serravallian–Tortonian (or Middle–Late Miocene) Alpine compressional tectonics.     

古利库金(银)矿床的稳定同位素地球化学特征

通过对大兴安岭古利库金银矿床的成矿热液流体的温度测定和同位素组成的研究,确定该矿床属浅成低温热液类型,并将成矿作用划分为2个成矿阶段,早期阶段成矿温度240~280℃,晚期成矿温度185~235℃.成矿热液流体的氢氧同位素组:δD_H2O-76‰~-94‰,δ¹⁸O-6.58‰~-14.11‰,表明成矿热液来自大气降水.矿石的硫和铅同位素组成说明成矿热液硫来自中生代火山岩,而铅是从基底落马湖变质岩系及相伴的兴凯期花岗岩类中萃取出来的.     

额尔古纳地区有色、贵金属成矿特征

额尔古纳地区是一个重要的有色、贵金属成矿省.区内金、银、铅、锌、铜等矿产具明显分带性,可划分为耳布尔、上护林及恩和3个成矿小区,分别以银铅锌、铜多金属、金为主.该区在J₃-K₁时期发生了强烈的构造-岩浆活动,这些矿产在成因上均与J₃-K₁时期酸性岩浆侵入作用密切相关,成矿热液主要来源于岩浆热液.矿体主要受次级张性裂隙控制,以NW向为主.成矿时代主要为J₃-K₁.     

Sulphur source and genesis of polymetallic sulphide occurrences of the Ofoten district in the Central–North Norwegian Caledonides: evidence from sulphur isotopic studies

Fourteen stratiform, stratabound and vein-type sulphide occurrences in the Upper Allochthon of the Central–North Norwegian Caledonides have been studied for their sulphur, oxygen and hydrogen isotope composition. Depositional ages of host rocks to the stratabound and stratiform sulphide occurrences range from 590 to 640?Ma. The sulphides and their host rocks have been affected by polyphase deformation and metamorphism with a peak temperature of 650?°C dated to 432?Ma. A total of 104 sulphide and 2 barite samples were analysed for δ³⁴S, 16 whole-rock and quartz samples for δ¹⁸O and 12 samples of muscovite for δD. The overall δ³⁴S values range from ?14 to +31‰ with the majority of sampled sulphides lying within a range of +4 to +15‰. In most cases δ³⁴S within each hand specimen behaves in accordance with the equilibrium fractionation sequence, δ³⁴S_gn<δ³⁴S_cp<δ³⁴S_sph<δ³⁴S_py. A systematic increase in δ³⁴S from the vein sulphides (?8‰) through schist/amphibolite-hosted (+6‰) and schist-hosted (+7 to +12‰) to dolomite-hosted (+12 to +31‰) occurrences is documented. The δ³⁴S averages of the stratiform schist-hosted sulphides are 17 to 22‰ lower than in the penecontemporaneous seawater sulphate. The Bjørkåsen (+4 to +6‰) occurrence is a volcanogenic massive sulphide (VMS) transitional to sedimentary massive sulphide (SMS), exhalative, massive, pyritic deposit of Cu–Zn–Pb sulphides formed by fluids which obtained H₂S via high-temperature reduction of seawater sulphate by oxidation of Fe²⁺ during the convective circulation of seawater through underlying rock sequences. The Raudvatn, volcanic-hosted, disseminated Cu sulphides (+6 to +8‰) obtained sulphur via a similar process. The Balsnes, stratiform, ‘black schist’-hosted, pyrite–pyrrhotite occurrence (?6 to ?14‰) is represented by typical diagenetic sulphides precipitated via bacteriogenic reduction of coeval (ca. 600?Ma) seawater sulphate (+25 to +35‰) in a system open to sulphate supply. The δ³⁴S values of the Djupvik–Skårnesdalen (+7 to +12‰), Hammerfjell (+5 to 11‰), Kaldådalen (+10 to +12‰) and Njallavarre (+7 to +8‰) stratiform, schist-hosted, massive and disseminated Zn–Pb (±Cu) sulphide occurrences, as well as the stratabound, quartzite-hosted, Au-bearing arsenopyrite occurrence at Langvatnet (+7 to +11‰), suggest that thermochemically reduced connate seawater sulphate was a principal sulphur source. The Sinklien and Tårstad, stratabound, dolomite- and dolomite collapse breccia-hosted, Zn (±Cu–Pb) sulphides are marked by the highest enrichment in ³⁴S (+20 to +31‰). The occurrences ?are?assigned to the Mississippi-Valley-type deposits.?High δ³⁴S values require reduction/replacement of contemporaneous (ca. 590?Ma) evaporitic sulphate (+23 to +34‰) with C_org-rich fluids in a closed system. The Melkedalen (+12 to +15‰), stratabound, fault-controlled, Cu–Zn sulphide deposit is hosted by the ca. 595?Ma dolomitised Melkedalen marble. The deposit is composed of several generations of ore minerals which formed by replacement of host dolomite. Polyphase hydrothermal fluids were introduced during several reactivation episodes of the fault zone. The positive δ³⁴S values with a very limited fractionation (<3‰) are indicative of the sulphide-sulphur generated through abiological, thermochemical reduction of seawater sulphate by organic material. The vein-type Cu (±Au–W) occurrences at Baugefjell, Bugtedalen and Baugevatn (?8 to ?4‰) are of hydrothermal origin and obtained their sulphur from igneous sources with a possible incorporation of sedimentary/diagenetic sulphides. In a broad sense, all the stratiform/stratabound, sediment-hosted, sulphide occurrences studied formed by epigenetic fluids within two probable scenarios which may be applicable separately or interactively: (1) expulsion of hot metal-bearing connate waters from deeper parts of sedimentary basins prior to nappe translation (late diagenetic/catagenetic/epigenetic fluids) or (2) tectonically driven expulsion in the course of nappe translation (early metamorphic fluids). A combination of (1) and (2) is favoured for the stratabound, fault-controlled, Melkedalen and Langvatnet occurrences, whereas the rest are considered to have formed within option (1). The sulphides and their host rocks were transported from unknown distances and thrust on to the Fennoscandian Shield during the course of the Caledonian orogeny. The displaced/allochthonous nature of the Ofoten Cu–Pb–Zn ‘metallogenetic province’ would explain the enigmatically high concentration of small-scale Cu–Pb–Zn deposits that occur only in this particular area of the Norwegian Caledonides.     

大兴安岭北部主要金属矿床成矿系列和区域矿床成矿谱系

文章以大兴安岭北部内生金属矿床、海相火山岩型硫铁矿矿床和砂金矿床为研究对象,按照矿床成矿系列的学术思想将其划分为7个矿床成矿系列,即:多宝山地区与加里东期中酸性火山_侵入活动有关的铜、钼矿床成矿系列,呼玛地区与华力西期辉长岩和花岗岩有关的铁、钛、金矿床成矿系列,伊尔施_黑河地区与华力西期花岗岩和海相火山岩有关的铁、铜、锌、硫铁矿矿床成矿系列,牙克石地区与华力西期海相中基性火山岩有关的铁、锌、硫铁矿矿床成矿系列,得尔布干地区与印支期_燕山期中酸性火山_侵入活动有关的铅、锌、银、铜、钼、金矿床成矿系列,伊尔施_呼玛地区与燕山期中酸性火山_侵入活动有关的金、铁、锌、铜、钼、钨矿床成矿系列和黑龙江流域与第四纪冲积沉积作用有关的砂金矿床成矿系列。大兴安岭北部区域矿床成矿谱系表明,从奥陶纪到新生代该区不同构造单元经历了7个主要的构造演化及成矿时期,依次出现奥陶纪岛弧环境的斑岩型矿床、泥盆纪陆块边缘拉张环境的岩浆型和热液脉型矿床、泥盆纪—石炭纪俯冲_碰撞环境的海相火山岩型和矽卡岩型矿床、石炭纪弧后盆地环境的海相火山岩型矿床、晚三叠世—早白垩世俯冲_碰撞_后碰撞环境的斑岩型、热液脉型、浅成低温热液型和矽卡岩型矿床、早侏罗世—早白垩世俯冲环境的斑岩型、热液脉型、浅成低温热液型和矽卡岩型矿床和新生代地壳差异运动带砂金矿床。大兴安岭北部优势矿种为铜、钼、金、银、铅、锌,主攻矿床类型为斑岩型、热液脉型、低硫化浅成低温热液型、冲积型和海相火山岩型。     

安徽铜陵天马山金硫矿床地质地球化学特征

安徽铜陵天马山金硫矿床发育上部层状矿体和下部网脉状矿体, 地球化学特征呈现出明显的垂向变化和二元结构性。从下部网脉状矿化岩石到上部层状矿石, Pb、Zn、Au、Ag、As、Hg等含量和δ18O值总体逐渐增高, Cu、Mo、Cr、Co、Ni、REE等含量和成矿温度499℃→65℃及δ34S值总体呈逐渐降低趋势。黄铁矿的δ34S值为+4.0‰~+9.6‰, 上部层状块状矿石中方解石和石英的δ18O平均值为+13.7‰, 下部网脉状矿化岩矿石中脉石英或全岩δ18O平均值为+12.3‰。地质地球化学特征反映天马山金硫矿床为海底热水喷流沉积成因。     

Metallogeny during continental outgrowth in the Columbia supercontinent: Isotopic characterization of the Zhaiwa Mo–Cu system in the North China Craton

The Eastern Qinling Molybdenum Belt (EQMB) in central China represents the largest Mo province in the world. Located at the southern margin of the North China Craton, this Mo province is largely associated with Mesozoic granitoids. Here we report Re–Os isochron age of 1761 ± 33 Ma (2σ, MSWD = 2.9) from molybdenite in the recently discovered Zhaiwa porphyry Mo–Cu system within the EQMB. This age coincides with the peak eruption period (1.78−1.75 Ga) of the Xiong'er Group volcanic rocks which unconformably overlie the Taihua Supergroup and are interpreted to have developed on a continental arc. The Re concentrations (1 to 43 ppm) of the Zhaiwa molybdenites are similar to those of typical porphyry Cu–Mo–Au systems developed on continental arcs. The δ³⁴S values of the Zhaiwa ores (2.7–7.3‰, average 5.2‰) suggest that the sulfur was mainly sourced from a magmatic system. The sulfides from the ores yield Sr_i average of 0.70533, similar to that of the Xiong'er Group (0.70547), albeit higher than that of the Kuanping Group (0.70334) and lower than the Taihua Supergroup (0.70763), suggesting a mixed source. The average ε_Nd(1.76 Ga) of the sulfides from the ores (0.9) falls between the averages of the Taihua Supergroup (ca. − 6.8) and the Kuanping Group (ca. 7.4). The Pb isotope ratios of the ores are similar to, but slightly higher than those of the Taihua Supergroup, reflecting preferential leaching of radiogenic Pb from the Taihua Supergroup by magmatic fluids. Integrated data and interpretations constrain the Zhaiwa Mo–Cu deposit to be a porphyry mineral system developed within a ca. 1.76 Ga continental arc related to oceanic plate subduction beneath the southern margin of the North China Craton. A correlation between tectonic settings and metallogenic types clearly indicate that the Xiong'er Group was formed in a volcanic arc, confirming Paleo-Mesoproterozoic continental outgrowth along the margins of the Columbia supercontinent. The isotopic characterization of the Zhaiwa deposit provides new insights into the enigma of the widespread distribution of large and super-large Mo deposits of EQMB along the southern margin of the North China Craton.     

Genesis of Luobuzhen Pb–Zn veins: Implications for porphyry Cu systems and exploration targeting at Luobuzhen-Dongshibu in western Gangdese belt,southern Tibet

Porphyry systems are known to form in magmatic arc environment and commonly include porphyry Cu, epithermal Pb–Zn–Au–Ag, skarn polymetallic mineralization, etc. The systems are rarely reported in collisional zones, such as the Gangdese belt in southern Tibet where many postcollisional porphyry copper deposits occurred. In addition, other types of mineral systems are rarely present except porphyry copper mineralization in the Gangdese belt. In this study, we present Pb–Zn-bearing quartz veins at Luobuzhen in the western Gangdese belt. The Luobuzhen Pb–Zn veins cross-cut dacite of the Linzizong Group with zircon U–Pb age of 50.1 ± 0.2 Ma and monzogranite with zircon U–Pb age of 17.1 ± 0.1 Ma. Ore minerals include sphalerite, galena, chalcopyrite, and pyrite; gangue minerals are quartz with minor chlorite and sericite. Primary fluid inclusions of quartz are liquid-rich, aqueous, and two-phase inclusions. The homogenization temperatures of these primary inclusions are moderate to high (267–400 °C), and salinities range from 8.9 to 18.4 wt.% NaCl equiv. Quartz has δ¹⁸O_SMOW values of 6.2–9.3‰, while sulfides have δ³⁴S_V-CDT values of −5.1‰ to 0.1‰, ²⁰⁶Pb/²⁰⁴Pb of 18.722–18.849, ²⁰⁷Pb/²⁰⁴Pb of 15.640–15.785, and ²⁰⁸Pb/²⁰⁴Pb of 39.068–39.560. These data suggest that magmatic fluids with contribution from meteoric water, magmatic sulfur, and lead derived from upper crust and metasomatized mantle by Indian continental materials would be critical for the Luobuzhen base metal mineralization.The Dongshibu area, located at ∼2 km east of the Luobuzhen, is characterized by high concentrations of Cu (up to 1450 ppm) and Mo (up to 130 ppm) of stream sediments, which is quite different from high concentrations in Pb, Zn, Ag, and Au shown in the Luobuzhen area. In addition, porphyry copper mineralization-related alteration and veins/veinlets occur in the Miocene monzogranite at Dongshibu. The monzogranite is characterized by high Sr/Y ratios, which are also shown on ore-forming intrusions in the Gangdese postcollisional porphyry copper deposits, and shows similar zircon Hf isotopes to the ore-related high Sr/Y intrusions from the Zhunuo porphyry copper deposit which is located ∼20 km northeast of the Luobuzhen-Dongshibu. A comprehensive analysis allows us to infer that the base metal veins at Luobuzhen are components of a porphyry Cu system with porphyry Cu mineralization likely present at Dongshibu and epithermal Au–Ag veins possibly occurring at Luobuzhen, which are indicative of the existence of porphyry copper systems in collisional zones. The potential porphyry Cu mineralization and epithermal Au–Ag veins should be targeted in future exploration at Luobuzhen-Dongshibu.