新疆东准噶尔绿源金矿床成因研究：流体包裹体及氢、氧同位素制约

东准噶尔绿源金矿是近年来新发现的矿床,位于野马泉-琼河坝古生代岛弧带东段的琼河坝矿集区。矿体主要产于上石炭统巴塔玛依内山组中酸性火山岩中,呈似层状、条带状、透镜状,多受断裂构造控制。流体成矿作用可分为4个阶段:石英-黄铁矿阶段、石英(玉髓)-金-黄铁矿阶段、石英-金-多金属硫化物阶段、石英-碳酸盐阶段,其中阶段2和阶段3为金主要成矿阶段。金属硫化物组合主要为黄铁矿-毒砂-闪锌矿-黄铜矿±银金矿组合。文章从流体包裹体和H、O同位素研究入手,对该矿床成矿流体和矿床成因进行探讨。流体包裹体岩相学特征显示,本矿床热液矿物中流体包裹体存在3种类型:富液相气液两相水溶液包裹体(V+L型)、富气相气液两相水溶液包裹体(V型)和纯液相水溶液包裹体(L型)。其中,V+L型包裹体数量最多,各阶段热液矿物中均有发育;V型包裹体数量最少;L型包裹体数量较少。显微测温结果显示:绿源金矿床石英中流体包裹体均一温度介于115~349℃之间,盐度集中于0.7%~8.8%NaCl eqv.之间,密度介于0.66~0.98g/cm~3之间;从阶段2至阶段4,流体均一温度从268~322℃,经181~300℃,降为115~176℃。这些都表明绿源金矿床成矿流体具有低温、低盐度、低密度的特征,与典型浅成低温热液型金矿成矿流体特征相似。对成矿压力和深度的估算表明,其成矿压力为(73~335)×10~5Pa(均值203×10~5Pa),成矿深度为0.24~1.12km(均值0.68km),显示出浅成热液矿床的特征。流体包裹体激光拉曼探针分析显示,各阶段包裹体成分类似,气相成分和液相成分主要为H_2O。成矿流体氢、氧同位素组成分别为δD_(H_2O)=-108.8‰~-129.0‰、δ~(18) O_(H_2O)=-7.2‰~4.6‰,表明成矿流体具有多来源,以大气降水为主的特征。综合矿床地质特征和成矿流体研究,认为流体不混溶作用可能是绿源金矿床的重要成矿机制,该矿床应属浅成低温热液型金矿床。     

青海省都兰县果洛龙洼金矿成矿流体

果洛龙洼金矿是青海东昆仑地区最典型、最具规模的金矿床之一。在前人资料基础上,将果洛龙洼金矿热液成矿期划分为4个成矿阶段：贫矿化石英阶段、石英-多金属硫化物阶段（主要成矿阶段）、石英-贫硫化物阶段（次要成矿阶段）和石英-碳酸盐阶段。随后对主要和次要成矿阶段石英脉开展流体包裹体显微测温和H-O同位素研究。结果表明：原生流体包裹体主要包括气液两相、富CO₂三相、纯CO₂两相共3类;成矿流体总体以CO₂-NaCl-H₂O体系为主,均一温度为130.0~357.3 ℃,盐度（w(NaCl)）为1.83%~20.11%。石英-多金属硫化物阶段石英δ¹⁸O_V-SMOW值为14.8‰~17.2‰,据此计算流体的δ¹⁸O_H2O值为5.5‰~8.5‰,流体的δD_V-SMOW值为-61‰~-96‰;而石英-贫硫化物阶段石英δ¹⁸O_V-SMOW值为15.7‰~16.9‰,据此计算流体的δ¹⁸O_H2O值为4.1‰~5.3‰,流体的δD_V-SMOW值为-84‰~-101‰。由此认为：主要成矿阶段成矿流体可能为高温低盐度富CO₂变质热液和低温中高盐度岩浆热液两个端元组成的混合流体;次要成矿阶段成矿流体主要为混合后更均匀的中低温中低盐度热液,但后期明显有大气降水混入。总之,成矿流体的来源、性质及其演化等方面的研究结果进一步证明果洛龙洼金矿为造山型金矿。     

胶东牟乳成矿带范家庄金矿床成矿流体特征及其地质意义

牟乳成矿带是胶东半岛金矿集区三大金成矿带之一,但带内金矿床的成矿流体来源仍存在着较大分歧。范家庄金矿床是近年在该成矿带内新发现的金矿床,其成矿流体的研究较为薄弱。鉴于此,本文从流体包裹体和H-O同位素研究入手,结合矿床地质特征,对范家庄金矿床的成矿流体和矿床成因进行探讨。金矿体主要产于侏罗纪弱片麻状黑云母二长花岗岩内,呈脉状、透镜状,受断裂构造控制明显。该矿床热液成矿期可分为3个成矿阶段：石英-粗粒黄铁矿阶段（成矿早阶段）、石英-金-多金属硫化物阶段（主成矿阶段）、石英-碳酸盐阶段（成矿晚阶段）。流体包裹体岩相学特征显示,矿床中的原生包裹体以气液两相包裹体和纯液相水溶液包裹体为主,另有少量含CO₂三相包裹体。显微测温结果显示,成矿早阶段和主成矿阶段的均一温度分别为167.2~297.5℃和168.4~253.6℃,盐度（w（NaCl））分别为3.55%~22.65%和2.58%~12.05%,密度分别为0.77~1.06 g/cm³和0.84~1.02 g/cm³,具有中低温、中低盐度、低密度的特征,与中温热液成矿系统流体特征相一致。对成矿压力和深度的估算表明,主成矿阶段的成矿压力为45.8~68.7 MPa （平均为52.8 MPa）,成矿深度为5.38~6.71 km （平均为5.93 km）,显示出中浅成成矿的特点。成矿流体H-O同位素示踪显示,成矿早阶段流体的δD_H2O-SMOW值介于-96.9‰~-89.0‰之间,δ¹⁸O_H2O-SMOW值介于-4.3‰~4.5‰之间;主成矿阶段的δD_H2O-SMOW值介于-90.7‰~-85.3‰之间,δ¹⁸O_H2O-SMOW值介于-5.4‰~-0.2‰之间。由此认为,范家庄金矿床的成矿流体来源于岩浆水与大气降水的混合,且随着成矿流体的演化,大气降水的混入比例增加。综合矿床地质特征和成矿流体研究,认为范家庄金矿床应属中温热液脉型金矿床。     

The Ore-forming Fluid of the Gold Deposits of Muru Gold Belt in Eastern Shandong, China - a Case Study of Denggezhuang Gold Deposit

Abstract. Denggezhuang gold deposit is an epithermal gold‐quartz vein deposit in northern Muru gold belt, eastern Shandong, China. The deposit occurs in the NNE‐striking faults within the Mesozoic granite. The deposit consists of four major veins with a general NNE‐strike. Based on crosscutting relationships and mineral parageneses, the veins appear to have been formed during the same mineralization epochs, and are further divided into three stages: (1) massive barren quartz veins; (2) quartz‐sulfides veins; (3) late, pure quartz or calcite veinlets. Most gold mineralization is associated with the second stage. The early stage is characterized by quartz, and small amounts of ore minerals (pyrite), the second stage is characterized by large amounts of ore minerals. Fluid inclusions in vein quartz contain C‐H‐O fluids of variable compositions. Three main types of fluid inclusions are recognized at room temperature: type I, two‐phase, aqueous vapor and an aqueous liquid phase (L+V); type II, aqueous‐carbonic inclusions, a CC₂‐liquid with/without vapor and aqueous liquid (LCO₂+VCC₂+Laq.); type III, mono‐phase aqueous liquid (Laq.). Data from fluid inclusion distribution, microthermometry, and gas analysis indicate that fluids associated with Au mineralized quartz veins (stage 2) have moderate salinity ranging from 1.91 to 16.43 wt% NaCl equivalent (modeled salinity around 8–10 wt% NaCl equiv.). These veins formatted at temperatures from 80d? to 280d?C. Fluids associated with barren quartz veins (stage 3) have a low salinity of about 1.91 to 2.57 wt% NaCl equivalent and lower temperature. There is evidence of fluid immiscibility and boiling in ore‐forming stages. Stable isotope analyses of quartz indicate that the veins were deposited by waters with δ^O and δD values ranging from those of magmatic water to typical meteoric water. The gold metallogenesis of Muru gold belt has no relationship with the granite, and formed during the late stage of the crust thinning of North China.     

Ore-Forming Fluid Characteristics of the Dayingezhuang Gold Deposit, Jiaodong Gold Province, China

The Dayingezhuang gold deposit is located in the central part of the Zhaoping Fault Zone, which is one of the most important gold-hosting faults in the Jiaodong gold province of China. Dayingezhuang is a typical large-scale shear zone-hosted disseminated gold deposit with superimposed silver mineralization. Fluid inclusion (FI) petrography and microthermometry, and analysis of oxygen and hydrogen isotopes for fluid inclusions were conducted to determine the characteristics of the ore-forming fluids and the processes of silver mineralization. Microthermometry data of FI indicated that ore-forming fluids are characterized by low salinity and low density. Homogenization pressures of FI are estimated at 20 × 10⁵–220 × 10⁵ Pa. The change in ore-forming fluids from K₂SO₄ type to NaCl type indicates the superposition of two hydrothermal mineralizing events. Ore-forming fluids were dominated by magmatic components in the early mineralization period, and affected by meteoric waters in the late period. Gold may have been transported as Au-S or Au-Cl complexes, whereas silver was transported as Ag-Cl complexes. Early fluid boiling and later fluid mixing are thought to be two of the main factors causing the deposition and superimposing of gold and silver to form the large deposit.     

Genesis of the Ciemas Gold Deposit and Relationship with Epithermal Deposits in West Java, Indonesia: Constraints from Fluid Inclusions and Stable Isotopes

The Ciemas gold deposit is located in West Java of Indonesia,which is a Cenozoic magmatism belt resulting from the Indo-Australian plate subducting under the Eurasian plate.Two different volcanic rock belts and associated epithermal deposits are distributed in West Java:the younger late Miocene-Pliocene magmatic belt generated the Pliocene-Pleistocene epithermal deposits,while the older late Eocene-early Miocene magmatic belt generated the Miocene epithermal deposits.To constrain the physico-chemical conditions and the origin of the ore fluid in Ciemas,a detailed study of ore petrography,fluid inclusions,laser Raman spectroscopy,oxygen-hydrogen isotopes for quartz was conducted.The results show that hydrothermal pyrite and quartz are widespread,hydrothermal alteration is well developed,and that leaching structures such as vuggy rocks and extension structures such as comb quartz are common.Fluid inclusions in quartz are mainly liquid-rich two phase inclusions,with fluid compositions in the NaCl-H20 fluid system,and contain no or little CO_2.Their homogenization temperatures cluster around 240℃-320℃,the salinities lie in the range of 14-17 wt.%NaCl equiv,and the calculated fluid densities are 0.65-1.00 g/cm~3.The values of δ~(18)O_(H2O-VSMOW)for quartz range from +5.5‰ to +7.7‰,the δD_(VSMOW) of fluid inclusions in quartz ranges from-70‰ to-115‰.All of these data indicate that mixing of magmatic fluid with meteoric water resulted in the formation of the Ciemas deposit.A comparison among gold deposits of West Java suggests that Miocene epithermal ore deposits in the southernmost part of West Java were more affected by magmatic fluids and exhibit a higher degree of sulfldation than those of Pliocene-Pleistocene.     

Association of Electrum and Calcite and Its Significance to the Genesis of the Hishikari Gold Deposits, Southern Kyushu, Japan

Abstract. Mineral assemblage, precipitation sequence and textures of the gold‐bearing veins from the Hishikari epithermal vein‐type deposits, southern Kyushu, Japan, were examined. In addition, fluid inclusion microthermometry and carbon and oxygen isotopic compositions of calcite were determined. Calcite, and that replaced by quartz, were commonly observed throughout the precipitation sequence of the veins. Thus, calcite must be a more common gangue constituent initially than observed presently. Association of calcite and electrum is observed immediately subsequent to columnar adularia in some vein samples. In addition, close association of electrum with pseudo‐acicular quartz, and electrum with truscottite were observed. The initial coprecipitation of electrum and calcite might be a common phenomenon in the gold‐bearing veins at the Hishikari deposits. The Th (homogenization temperature) data from the Honko‐Sanjin deposits are generally higher than those from the Yamada deposit. Samples that show association of calcite and electrum yielded higher Th (206–217°C, average) than the Th data from calcite associated with low‐grade Au ore or barren (180–204°C, average). The measured Tm (temperature of last melting point of ice) range from ‐0.4 to 0.0°C. The result suggests that the salinity of the hydrothermal solution was low during the precipitation both of calcite associated with Au mineralization and of barren calcite. Fluid inclusion evidence suggestive of boiling of hydrothermal solution for the precipitation of calcite was not recognized in the present work. The δ¹³C and δ¹⁸O values of calcite range from ‐10.8 to —4.7 % and from +3.2 to +15.2 %, respectively. The δ¹³C value of H₂CO₃ and the δ¹⁸O value of H₂O in the hydrothermal fluids calculated assuming isotopic equilibrium with calcite using the temperature obtained by fluid inclusion microthermometry, range from ‐14.4 to ‐9.1 %, and from ‐6.2 to +5.5 %, respectively. Thus, the calculated δ¹⁸O values of H₂O for calcite further confirm the presence of the ¹⁸O‐enriched ore fluids during the mineralization at the Hishikari deposits. The hydrothermal solution isotopically equilibrated with the sedimentary basement rocks was responsible for the gold mineralization associated with calcite.     

黑龙江省老柞山金矿床成矿流体特征及矿床成因

黑龙江省老柞山金矿床位于兴蒙造山带东段佳木斯地块的中北部,是佳木斯金多金属成矿区的一座大型矿床,金主要赋存在NW向、NWW向的张性断裂及花岗岩和钙质大理岩、钙质片麻岩的接触构造带内,成矿与矽卡岩密切伴生。根据野外和室内研究,成矿阶段可划分为矽卡岩阶段、氧化物阶段、早期石英硫化物阶段、晚期石英硫化物阶段和石英-方解石阶段。为揭示流体演化过程,本文选择石榴子石、石英和方解石开展了流体包裹体研究。包裹体岩相学显示,流体包裹体类型有含子晶三相、气液两相（富液相、富气相）、纯液相和纯气相包裹体。测温结果表明：从早到晚均一温度依次为448~462、240~509、166~480、118~360和57~230℃;在矽卡岩阶段盐度（w（NaCl））为9.21%~10.37%,在氧化物阶段为1.73%~13.77%,中低盐度,在早期石英硫化物阶段为1.73%~23.71%和23.64%~39.66%,在晚期石英硫化物阶段为3.05%~6.44%,在石英-方解石阶段为1.73%~11.95%。高温中低盐度且富含CO₂、H₂O和少量CH₄的初始成矿流体,在氧化物阶段流体"沸腾",CO₂逃逸,生成磁铁矿;在早期石英硫化物阶段流体持续沸腾,pH值升高,由氧化转化为还原,卸载金和毒砂、黄铁矿等硫化物;在晚期石英硫化物阶段温度降低,卸载方铅矿、闪锌矿等低温矿物和金。因此,推测老柞山金矿床属于矽卡岩型金矿床。     

Variations in Chemical Composition of Clay Minerals and Magnetic Susceptibility of Hydrothermally Altered Rocks in the Hishikari Epithermal Gold Deposit, SW Kyushu, Japan

Hydrothermal alteration, involving chiefly chlorite and illite, is extensively distributed within host rocks of the Pleistocene Hishikari Lower Andesites (HLA) and the Cretaceous Shimanto Supergroup (SSG) in the underground mining area of the Hishikari epithermal gold deposit, Kagoshima, Japan. Approximately 60% of the mineable auriferous quartz‐adularia veins in the Honko vein system occur in sedimentary rocks of the SSG, whereas all the veins of the Yamada vein system occur in volcanic rocks of the HLA. Variations in the abundance and chemical composition of hydrothermal minerals and magnetic susceptibility of the hydrothermally altered rocks of the HLA and SSG were analyzed. In volcanic rocks of the HLA, hydrothermal minerals such as quartz, chlorite, adularia, illite, and pyrite replaced primary minerals. The amount of hydrothermal minerals in the volcanic rocks including chlorite, adularia, illite, and pyrite as well as the altered and/or replaced pyroxenes and plagioclase phenocrysts increases toward the veins in the Honko vein system. The vein‐centered variation in mineral assemblage is pronounced within up to 25 m from the veins in the peripheral area of the Honko vein system, whereas it is not as apparent in the Yamada vein system. The hydrothermal minerals in sandstone of the SSG occur mainly as seams less than a few millimeters thick and are sporadically observed in halos along the veins and/or the seams. The alteration halos in sandstone of the SSG are restricted to within 1 m of the veins. In the peripheral area of the Honko vein system, chlorite in volcanic rocks is characterized by increasing in Al in its tetrahedral layer and the Fe/Fe + Mg ratio toward the veins, while illite in volcanic rocks has relatively low K and a restricted range of Fe/Fe + Mg ratios. Temperature estimates derived from chlorite geothermometry rise toward the veins within the volcanic rocks. The magnetic susceptibility of tuff breccia of the HLA varies from 21 to less than 0.01 × 10^?3 SI within a span of 40 m from the veins and has significant variation relative to that of andesite (27–0.06 × 10^?3 SI). The variation peripheral to the Honko vein system correlates with an increase in the abundance of hematite pseudomorphs after magnetite, the percentage of adularia and chlorite with high Fe/Fe + Mg ratios, and the degree of plagioclase alteration with decreasing distance to the veins. In contrast, sedimentary rocks of the SSG maintain a consistent magnetic susceptibility across the alteration zone, within a narrow range from 0.3 to 0.2 × 10^?3 SI. Magnetic susceptibility of volcanic rocks of the HLA, especially tuff breccia, could serve as an effective exploration tool for identifying altered volcanic rocks.     

Timing of Fracture Formation and Duration of Mineralization at the Hishikari Deposit, Southern Kyushu, Japan

Abstract. The Hishikari epithermal gold deposit consists of the Honko-Sanjin zone and Yamada zone. On the basis of observed crosscutting relationships of veins, vein system in the Hishikari deposit was classified into the early and late veins. They differ from orientation, width, control by unconformity, the amount of displacement and structural features, but have similarity in gold grade and Au/Ag ratios. K-Ar ages are presented for the classified veins to clarify timing of fracturing and duration of mineralization.
Age determination revealed that the early veins in the Honko-Sanjin zone range from 0.86 to 1.11 Ma and that the late veins range from 0.73 to 0. 84 Ma. The economically most important mineralization in the Hishikari deposit occurred around 0.90 Ma in a very short period (about 0.05 million years).
The distribution of mineralization age in the whole Hishikari deposit, occurrences of slickensides and ground water temperatures imply that mineralization lasted longer in the southern part of the deposit. As compared the early veins with late veins, structural changes including width, strike, dip and vein characteristics occurred at around 0.85 Ma.     

新疆西南天山阿万达金矿床成矿流体演化

阿万达金矿位于新疆阿克苏市拜城县, 属西南天山造山带, 是一新发现的中型金矿床。在简要总结矿床地质特征的基础上, 通过流体包裹体显微测温和毒砂地温计研究, 详尽地探讨了阿万达金矿成矿流体的演化。研究表明:矿化石英中存在含CO₂的三相和气液两相两类包裹体, 且以后者居多;气液两相包裹体均一温度为188~380℃, 呈双峰式分布, 盐度(w(NaCl))为6.9%~20.7%;含CO₂包裹体的最终均一温度为238~347℃, 盐度为2.8%~7.0%。综合分析认为, 阿万达金矿成矿流体经历了由高温向中低温两个成矿阶段的演化过程。高温阶段, 成矿流体均一温度为270~380℃, 捕获温度为345~420℃, 估算的捕获压力为74~142 MPa(按静岩压力估算成矿深度为2.8~5.4 km), 以中低盐度H₂O-CO₂-NaCl体系为主, 形成高温毒砂及其他硫化物;中低温阶段, 均一温度为188~270℃, 捕获温度为270~304℃, 捕获压力为52~104 MPa, 成矿流体成分向中低盐度H₂O-NaCl体系转变, 沉淀出低温毒砂及其他硫化物。综合阿万达金矿的矿床地质特征以及流体演化特点, 认为其成因类型属中浅成造山型金矿。     

Mass Transfer, Oxygen Isotopic Variation and Gold Precipitation in Epithermal System: A Case Study of the Hishikari Deposit, Southern Kyushu, Japan

Abstract: Transportation of various kinds of elements occurred in wall rocks (Quaternary andesites) during the hydrothermal alteration accompanied by the Hishikari epithermal gold mineralization. For example, K₂O and MgO contents of wall rocks decrease away from the gold-quartz veins, while (CaO+Na₂O) content increases, and SiO₂ content is variable near the veins. Hydrothermal alteration zoning and bulk compositional variations in wall rocks suggest that the mixing of hydrothermal solution and acidic groundwater took place an important role as the cause for the hydrothermal alteration and bulk compositional variations. The relationship between dissolved silica concentration and temperature of hydrothermal solution mixed with groundwater is obtained based on precipitation kinetics-fluid flow–mixing model, and the computed results are compared with the distribution of SiO₂ minerals (quartz and cristobalite) in the hydrothermal alteration zones. This comparison suggests that the most reasonable flow rate of fluids migrating through hydrothermal alteration zones, and A/M (A: surface area of rocks interacting with fluid, M: mass of fluid) are estimated to be ca. 10^-4.2 m/sec, and ca. 0.10 m²/kg, respectively. The mixing of two fluids (hydrothermal solution and acidic groundwater) can also explain δ¹⁸O zoning in the altered country rocks, hydrothermal alteration zoning from K-feldspar through K-mica to kaolinite from the center (veins) to margin, and deposition of gold.     

山东省寺庄金矿床成矿流体特征

莱州寺庄金矿床位于焦家成矿带南段,是焦家金矿田的一部分,也是焦家成矿带上重要的热液脉型金矿床。区内主要有黄铁绢英岩带、黄铁绢英岩化花岗碎裂岩带和黄铁绢英岩化花岗岩带3个控矿带,位于焦家断裂带下盘。矿石矿物主要为银金矿、黄铁矿、自然金、黄铜矿、方铅矿和闪锌矿等。该矿床发育了绢英岩化、硅化、钾化、碳酸盐化等蚀变类型,且硅化和绢英岩化与矿化关系最为密切。本文从流体包裹体岩相学特征、显微测温、单个包裹体成分激光拉曼光谱分析以及氢、氧同位素分析方面对山东省寺庄金矿床成矿流体特征进行综合研究。结果显示：该矿床金矿石中主要发育含CO₂相、气液两相和CO₂相三类包裹体。在成矿过程中,流体经历了CO₂-H₂O-NaCl体系的不混溶作用。成矿流体具有低盐度（w（NaCl）为（0.53%~10.24%））、低密度（0.50~1.03 g/cm³）的特点。成矿温度为260~340℃,压力为82~116 MPa,成矿深度为中成（7.40~8.94 km）。氢、氧同位素分析成矿流体δD_V-SNOW为-76.6‰~-69.0‰,δ¹⁸O_水为2.94‰~7.24‰,说明成矿流体以幔源流体为主,并有少量的岩浆水和大气降水参与。结合该矿床地质特征与实验结果综合分析,认为寺庄金矿的矿床成因类型为受断裂构造控制的幔源流体参与成矿的中温中成热液蚀变岩型金矿床。     

黑龙江省漠河县砂宝斯金矿床流体特征及矿床成因

成因类型与控矿条件的不确定一直是制约砂宝斯金矿床找矿突破的关键因素.就成矿背景而言, 多数学者认为其形成于造山过程的挤压背景, 而是否与伸展构造体系有关则鲜有研究.为重新确定砂宝斯金矿床的成因类型, 在详实的野外调研基础上, 对该矿床的控矿构造、成矿流体特征、成矿物质来源等方面展开深入研究.结果表明, 矿床受大型拆离断层控制, 矿体主要赋存于拆离断层的次级张性断裂中.通过扫描电镜首次发现了含砷黄铁矿, 与毒砂、黄铁矿共生于早阶段, 指示该矿床形成于中温或中温偏高的热液环境.石英中流体包裹体较为发育, 以气液两相为主.主成矿阶段流体具有中温(峰值为200~260℃)、低盐度(平均值为5.56% NaCl equiv.)、低密度(平均值为0.87g/cm3)的特征.成矿流体气相成分主要为H₂O、CO₂与CH₄, 属于H₂O-CO₂-CH₄体系.硫主要来自深源岩浆(成矿早阶段黄铁矿δ34S为-1.3‰~5.6‰), 也有少量地层硫.成矿流体盐度随着温度降低而降低, 不同流体混合是成矿物质卸载沉淀成矿的主要机制.综合研究表明, 砂宝斯金矿床的成因类型属受拆离断层控制的中温热液脉型金矿床, 形成于燕山晚期地壳强烈伸展和幔源物质大规模参与地壳演化的构造背景.      

河南祁雨沟金矿临界-超临界包裹体特征及成矿流体演化

河南省祁雨沟金矿床位于华北地块南部熊耳地体东北缘,是我国典型的角砾岩型金矿。该矿床临界-超临界流体包裹体的发现对研究成矿流体演化及成矿机制有重要意义。包裹体岩相学、显微测温以及激光拉曼显微探针（LRM）研究显示,祁雨沟J4角砾岩筒中发育临界状态均一的包裹体富含CO₂,这些包裹体出现在第Ⅰ、Ⅱ成矿阶段,并且在金品位最高的400-460中段出现最为集中,对成矿有明显的指示作用。临界-超临界流体来自富含挥发分的高氧化状态岩浆的出溶作用。流体演化先后经历了高氧化状态的岩浆-流体体系→临界-超临界流体体系→H₂O-NaCl和CO₂-H₂O流体体系→低盐度的H₂O-NaCl流体体系→H₂O流体体系。临界―超临界流体体系在383.7~387.2 ℃发生了沸腾作用,沸腾作用可能是祁雨沟金矿J4岩筒中成矿物质沉淀的重要原因之一。     

新疆东准噶尔绿源金矿床地质特征与金成矿物质来源分析

绿源浅成低温热液型金矿床位于野马泉-琼河坝古生代岛弧带东段的琼河坝矿集区。赋矿地层为一套中酸性火山熔岩夹火山碎屑岩建造。矿体呈似层状、条带状、透镜状,多受断裂构造控制。其热液成矿作用可分为4个阶段:石英-黄铁矿阶段(S1)、石英(玉髓)-金-黄铁矿阶段(S2)、石英-金-多金属硫化物阶段(S3)、石英-碳酸盐阶段(S4)。金主要赋存于S2和S3阶段。本文对该矿床开展S、Pb同位素及硫化物稀土元素研究,拟揭示其成矿物质来源。结果表明,绿源金矿床金属硫化物的硫同位素组成比较稳定,δ34S集中于+0.2‰~+2.8‰,均值为+1.35‰,显示出岩浆硫的组成特征。矿石与围岩中硫化物的硫同位素δ34S值一致,表明硫可能来源于矿区巴塔玛依内山组火山岩地层。S2和S3阶段硫化物的铅同位素~(206)Pb/~(204)Pb=16.457~18.084、~(207)Pb/~(204)Pb=15.267~15.635、208Pb/~(204)Pb=36.472~38.379,另一件长石的Pb铅同位素~(206)Pb/~(204)Pb=18.546、~(207)Pb/~(204)Pb=15.509、208Pb/~(204)Pb=38.183,μ值介于9.11~9.58之间,ω值介于33.97~38.61之间。上述各铅同位素比值变化范围较大,远远大于正常铅同位素组成的变化范围。结合同位素组成特征及特征参数法认为绿源金矿床矿石Pb为异常Pb,铅源为混合来源,一部分来源于上地壳物质,一部分来源于地幔物质。硫化物稀土元素特征与火山岩类似,暗示成矿物质可能来源于火山岩地层。H、O同位素特征显示,绿源金矿成矿流体以大气降水为主,有少量岩浆水的加入。综合S、Pb同位素、稀土元素等分析,本文认为绿源矿区岩浆活动和成矿作用具有壳幔混合源特征,成矿物质具深源特征,主要直接来自赋矿火山岩。     

辽宁省朝阳市东五家子金矿成矿流体特征及矿床成因探讨

东五家子金矿所处大地构造位置为华北克拉通北缘中段,其北侧以赤峰-开原深大断裂与内蒙-兴安褶皱造山带相隔,南侧以凌源-北票深断裂与燕山沉降带为邻.北西向断层为矿区内最主要的容矿构造,脉岩中的闪斜煌斑岩与矿化关系最为密切.矿石自然类型为石英脉型,矿石中硫化物主要为黄铁矿,其次为黄铜矿和方铅矿.贵金属矿物有自然金和碲银矿.围岩蚀变为硅化、绢云母化和碳酸盐化等,蚀变分带明显.矿石中明显出现碲化物,与矿化关系密切的闪斜煌斑岩发育,矿石硫同位素δ34S‰接近零值等表明成矿流体具幔源流体特征.石英流体包裹体发育较差,包裹体为单一的气液两相包裹体,属H2O-NaCl体系类型.流体盐度为9.86%～16.72%,且随着温度降低盐度出现升高的趋势.流体密度为0.936～1.017g/cm3,成矿温度为172.3～212.6℃,成矿压力为19～24MPa,形成深度为1.9～2.4km.与国内典型的造山型金矿对比表明,该矿床属浅成的造山型金矿,成矿动力学背景为早燕山期华北与西伯利亚克拉通碰撞后的陆内造山.     

西藏列廷冈-勒青拉铅锌铁铜钼矿床成矿流体特征:来自流体包裹体及碳氢氧同位素的证据

列廷冈-勒青拉矿床位于西藏冈底斯北缘多金属成矿带东侧,是该成矿带内一个独特的同时发育Pb、Zn、Fe、Cu、Mo五种元素矿化的典型矽卡岩型矿床.对该矿床成矿流体性质研究有助于解决这种具有不同来源属性的多金属共生矿床的成矿机制等科学问题.基于此,选取与Fe-Cu-Mo矿化和Pb-Zn-Cu矿化密切相关的矽卡岩矿物和脉石矿物,系统开展了流体包裹体和碳氢氧同位素研究,结果显示二者的成矿流体来源相同并经历了相似的演化过程.矽卡岩阶段主要发育富液相包裹体,成矿流体具有高温中高盐度特征.成矿期石英硫化物阶段和成矿后期碳酸盐阶段主要发育富液相包裹体和含子晶的多相包裹体,前者成矿流体温度属于中高温范畴,而盐度分为高盐度和低盐度两类;后者成矿流体温度属于中低温范畴,而盐度同样分为高盐度和低盐度两类,研究表明出现两种盐度截然不同的流体是由于沸腾作用造成的.稳定同位素研究结果显示矽卡岩阶段成矿流体主要源于发生过脱水去气作用的残余岩浆水,石英硫化物阶段和碳酸盐阶段均有大气降水的参与.灰岩地层与正常海相碳酸盐岩相比δ18O明显亏损,表明成矿流体在矿区灰岩地层中大规模运移并发生水岩反应,从而在远端矽卡岩带形成铅锌铜矿化.结合前人及本次研究结果,列廷冈-勒青拉矿床Fe-Cu矿化与Pb-Zn矿化为同一时期岩浆活动的产物,但分别与不同属性的岩浆有关.降温冷却、流体混合作用以及pH值的变化是控制列廷冈-勒青拉矿床金属沉淀的重要因素,而成矿温度和岩浆属性的差异是造成成矿元素在空间上分带的主要原因.     

新疆阿希低硫型金矿床流体地球化学特征与成矿机制

位于新疆西天山的阿希金矿为一赋存于古生代陆相火山岩中的冰长石—绢云母型（低硫型）浅成低温热液金矿床,其围岩为下石炭统安山质火山岩和火山碎屑岩。矿体呈脉状产出,严格受古火山机构外围的环形断裂带控制。成矿作用分为石英—玉髓状石英脉阶段、石英脉阶段、石英碳酸盐脉阶段、硫化物脉阶段、碳酸盐脉阶段,形成的矿石有石英脉型和蚀变岩型两类。成矿作用阶段形成的流体包裹体主要有三类：液相水溶液包裹体、富液相气液两相水溶液包裹体和富气相的气液两相水溶液包裹体,其中以前两类为主。三类流体包裹体在矿石中同时出现,说明它们形成于非均一的流体介质条件,矿床形成时流体发生了沸腾作用。成矿流体冰点温度一般为-0.3--2.3℃,相应盐度为0.48%-3.75%NaCleq,平均1.85%NaCleq;冰点峰值温度位于-0.4--1.6℃,相应盐度为0.66%-2.63%NaCleq。流体包裹体均一温度为121-335℃,平均209℃;均一温度峰值为140-240℃,计算得到流体密度为0.73-0.96,成矿深度小于700m。成矿流体的氢、氧同位素变化范围小,δDSMOW,H2O=-98‰--116‰,δ18OSMOW,H2O=-0.55‰-1.65‰;碳同位素δ13CPDB,方解石=2.6‰-4.9‰,δ34SCDT=-4.0‰-3.1‰,平均值为δ34SCDT=-0.45‰,表明成矿流体主要为循环的大气降水,成矿物质主要来自赋矿围岩火山岩及基底岩石。含金石英脉中冰长石、叶片状石英和硫化物集合体的出现,以及气相比例和均一温度变化很大的液相、富液相和富气相的水溶液包裹体的共生,说明流体的沸腾作用是引起成矿流体中矿质发生沉淀富集的主要成矿机制;对于蚀变岩型矿石,其成矿以水岩交代反应为主,成矿作用过程中流体处于近中性pH值环境。     

西秦岭大桥金矿硅质岩硅氧同位素特征及成因探讨

西秦岭大桥金矿床位于岷县-宕昌和舟曲-成县大断裂之间,金矿体赋存于三叠系下部灰岩、泥质板岩岩性不整合界面处的硅质角砾岩中。硅质角砾岩呈似层状、板状和透镜状产出,倾向于断裂带分布两侧,矿石构造以角砾状、被膜状、皮壳状、细脉-网脉状、孔隙状构造为主。矿石矿物主要为黄铁矿、白铁矿、磁黄铁矿、毒砂、闪锌矿、方铅矿、黄铜矿,蚀变以硅化、绢云母、方解石为主,矿化元素组合为Au、Sb、Ag、As、Hg、W。利用氧同位素地质温度计估算的硅质岩形成温度为142~218℃,硅质岩δ30Si值为-0.7‰~0.4‰,δ18O为12.8‰~17.9‰,与热水-热泉华型金矿床地质特征及同位素特征一致。综合研究认为,大桥金矿硅质岩为热水-热泉形成,硅质角砾岩是在断裂带的周期性破裂-自封闭条件下,由流体超压引发的岩石破裂形成。