Geochemical Characteristics of Gold Polymetallic Deposits as Exemplified by the Laozuoshan Deposit,Heilong jiang,China

From the studies of ore deposit geologic settings,sulfur isotopes,lead isotopes,carbon isotopes and oxygen isotopes,fluid inclusions and petrochemistry in this paper,the authors have drawn a conclusion that the ore-forming hydrothermal solutions are the high-temperature magmatic hydrothermal solutions for the gold ore deposit,and at the same time,the involvemety of crustal materials can not be ruled out .It is the first time that the authors have proposed that the Laozuoshan gold-ploymetallic ore deposit in Heilongjiang Province was formed in the calc-alkaline series environment at the margin of an active continent.     

浙江八面山萤石矿床流体包裹体地球化学研究

八面山萤石矿床流体包裹体可分为三大类型:Ⅰ气液包裹体,Ⅱ气体包裹体,Ⅲ含子矿物的多相包裹体;矿床成矿温度变化不大,主要集中在120～240°C之间。细粒条带状萤石矿石包裹体温度变化在115～250℃之间;巨晶块状萤石矿石和石英脉型萤石矿石包裹体温度集中在135～170℃之间。萤石矿床流体包裹体以低盐度成矿流体为主。成矿过程中起作用的成矿流体为KCl-H2O体系和CO2-CaF2-H2O体系,成矿溶液的离子类型属K+-Ca2+-HCO--F-型,KCl-H2O体系反映岩浆期后热液作用的结果,而CO2-CaF2-H2O体系可能反映了寒武纪矿源层成矿体系。通过包裹体研究,认为八面山萤石矿床是受地层-岩体-层间断裂共同控制三位一体的热液成因矿床。     

Genesis of the Xiuwenghala Gold Deposit in the Beishan Orogen,Northwest China: Evidence from Geology,Fluid Inclusion,and H–O–S–Pb Isotopes

The Xiuwenghala gold deposit is located in the Beishan Orogen of the southern Central Asian Orogenic Belt. The vein/lenticular gold orebodies are controlled by Northeast‐trending faults and are hosted mainly in the brecciated/altered tuff and rhyolite porphyry of the Lower Carboniferous Baishan Formation. Metallic minerals include mainly pyrite and minor chalcopyrite, arsenopyrite, galena, and sphalerite, whilst nonmetallic minerals include quartz, chalcedony, sericite, chlorite, and calcite. Hydrothermal alterations consist of silicic, sericite, chlorite, and carbonate. Alteration/mineralization processes comprise three stages: pre‐ore silicic alteration (Stage I), syn‐ore quartz‐chalcedony‐polymetallic sulfide mineralization (Stage II), and post‐ore quartz‐calcite veining (Stage III). Fluid inclusions (FIs) in quartz and calcite are dominated by L‐type with minor V‐type and lack any daughter mineral‐bearing or CO₂‐rich/‐bearing inclusions. From Stages I to III, the FIs homogenized at 240–260°C, 220–250°C, and 150–190°C, with corresponding salinities of 2.9–10.9, 3.2–11.1, and 2.9–11.9 wt.% NaCl eqv., respectively. The mineralization depth at Xiuwenghala is estimated to be relatively shallow (<1 km). FI results indicate that the ore‐forming fluids belong to a low to medium‐temperature, low‐salinity, and low‐density NaCl‐H₂O system. The values decrease from Stage I to III (3.7‰, 1.7–2.4‰, and ?1.7 to 0.9‰, respectively), and a similar trend is found for their values (?104 to ?90‰, ?126 to ?86‰, and ?130 to ?106‰, respectively). This indicates that the fluid source gradually evolved from magmatic to meteoric. δ³⁴S values of the hydrothermal pyrites (?3.0 to 0.0‰; avg. ?1.1‰) resemble those of typical magmatic/mantle‐derived sulfides. Pyrite Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 18.409–18.767, ²⁰⁷Pb/²⁰⁴Pb = 15.600–15.715, ²⁰⁸Pb^/204Pb = 38.173–38.654) are similar to those of the (sub)volcanic ore host, indicating that the origin of ore‐forming material was mainly the upper crustal (sub)volcanic rocks. Integrating evidence from geology, FIs, and H–O–S–Pb isotopes, we suggest that Xiuwenghala is best classified as a low‐sulfidation epithermal gold deposit.     

安徽金寨银水寺铅锌矿床流体包裹体和同位素地球化学特征

银水寺铅锌矿床位于大别造山带北缘,是该区最大的矽卡岩型矿床。矿体主要发育在中元古界庐镇关岩群仙人冲组大理岩与郑堂子组千枚岩之间的层间破碎带以及正长花岗斑岩与大理岩的接触带中。矿床先后经历了四个成矿阶段,矽卡岩阶段(Ⅰ)、石英.白钨矿阶段(Ⅱ)、石英.硫化物阶段(Ⅲ)、碳酸盐阶段(Ⅳ)。矽卡岩阶段(Ⅰ)主要发育绿帘石、阳起石、石英、绿泥石、磁铁矿及少量金属硫化物等;石英.白钨矿阶段(Ⅱ)主要发育石英、方解石、萤石及少量白钨矿和金属硫化物;石英.硫化物阶段(Ⅲ)广泛发育闪锌矿、方铅矿、黄铜矿等金属硫化物及石英、方解石、萤石、绿泥石等;碳酸盐阶段(Ⅳ)主要发育方解石、石英及少量黄铁矿。矿床中发育三种类型流体包裹体,包括富CO2水溶液包裹体(AC类)、气液两相水溶液包裹体(L类)和含子晶多相包裹体(S型)。根据流体包裹体岩相学、显微测温、激光拉曼研究结果,矽卡岩阶段主要有富CO2包裹体和气液两相水溶液包裹体,均一温度为314~400℃、盐度变化范围较大(1.1%~19.3%NaCleqv);石英.白钨矿阶段发育气液两相水溶液包裹体、含子晶多相包裹体和富CO2包裹体,后两者均一温度相近(263~349℃)、盐度差异较大(32.8%~41%NaCleqv和0.8%~6.1%NaCleqv),表明流体发生了沸腾作用;石英.硫化物阶段主要发育气液两相水溶液包裹体,均一温度为230~332℃,盐度为0.2%~8.9%NaCleqv;碳酸盐阶段只发育气液两相水溶液包裹体,显示低温(162~245℃)、低盐度(0.2%~5.6%NaCleqv)的特征。矿床不同成矿阶段石英、绿帘石中流体包裹体中水H-O同位素研究结果表明,δ18Ofluid值从早到晚逐渐减小,其中矽卡岩阶段为–1.3‰~4.7‰、石英.硫化物阶段为–5.1‰~–3.1‰,表明银水寺矿床早期成矿流体主要为岩浆来源,并在成矿过程中不断有大气降水的加入。石英流体包裹体中CO2的C同位素测试结果表明,矽卡岩阶段δ13CV-PDB值为–9.2‰,石英.硫化物阶段为–25.8‰~–15.4‰,表明早期成矿流体中碳质主要来自岩浆,石英-硫化物阶段有大量有机碳加入,其可能与流体和富含有机质的地层反应有关。矿石中主要金属硫化物的δ34S值(1.7‰~4.4‰)显示了深源硫的特征。Pb同位素变化范围集中(206Pb/204Pb=16.55~16.705,207Pb/204Pb=15.369~15.459,208Pb/204Pb=37.463~37.767),显示壳幔混源的特点。随着成矿作用的进行,岩浆流体与碳酸盐围岩地层发生水岩交代反应形成矽卡岩,该过程造成了成矿矽卡岩阶段磁铁矿和少量闪锌矿的沉淀;断裂活动造成热液体系压力下降,流体发生沸腾,CO2、HF进入气相并逃逸促使矿床中钨的沉淀;同时大气降水沿裂隙灌入,混合作用导致流体的温度、盐度降低,Cl–浓度下降,造成矿床中铅锌的大面积沉淀。     

羊石坑汞矿床包裹体地球化学特征研究

羊石坑汞矿是80年代后期勘探的大型汞矿床,矿床位于川黔汞矿带北部,矿体以细脉、网脉浸染状为主。包裹体地球化学研究表明,成矿温度120～250℃,成矿流体盐度为10.6％(NaCl),流体沸腾发生在250℃左右,包裹体圈闭的最小压力为40×10~5Pa,成矿深度约为400m。结合成矿构造环境、构造演化、探讨了构造改造成矿机制和规律。     

鄂尔多斯盆地中部奥陶系方解石脉中包裹体流体势研究

结合前人研究成果，归纳出了一种利用盐水包裹体均一温度与盐度确定流体势的方法，并对鄂尔多斯盆地中部气田奥陶系方解石脉中包裹体进行了流体势计算，推算出了古流体运移方向。     

On Rhythmical Layering of Rocks Formed from Basaltic Magma

Formation of rhythmical layering in intrusive basic and ultrabasic rock bodies is explained in different ways, in particular, by the movement of microparticles (mineral clusters) of plagioclase and pyroxene within the basalt melt under the influence of thermal and gravitational forces. A model of cluster movement is proposed as a consequence of the forces appearing when ultrasonic elastic fluctuations pass through the melt. The model is based on fundamental dynamic equations. Depending on cluster density, wave parameters, and magmatic chamber size, in the melt there can form different combinations of rhythmically alternating layers of different composition.     

三种类型烃-烃不混溶包裹体组合的特征和热力学条件的计算

在自然界广泛分布着烃-烃不混溶体系中捕获的流体包裹体,由于这些包裹体具有复杂的组成和相态,因此不混溶包裹体组合的判别和热力学参数的计算常常难以进行。根据烃-烃不混溶体系中两个端员组分流体包裹体室温下的相态特征和在温度-压力平面图上等容线交点显示的位置,划分成三种类型流体包裹体组合,本文介绍了三种类型流体包裹体组合特征,叙述了不混溶烃-烃包裹体组合的测定和判别方法,并且阐述均一化包裹体相态方程和气-液平衡常数原理和方法。与此同时列攀了自然界简单的三种类型不混溶烃-烃包裹体组合的测定、判别和计算的几个实例,利用相态方程和气．液平衡常数,不但精确地计算出包裹体均一压力,并且精确地计算出流体密度和体积等热力学参数。最后,利用均一成气相和液相的两种包裹体在p—T平面图上等容线交点同样计算出流体包裹体组合的捕获温度和压力。     

Hydrothermal Fluid Sources of the Fengjia Barite–fluorite Deposit in Southeast Sichuan,China: Evidence from Fluid Inclusions and Hydrogen and Oxygen Isotopes

The Fengjia barite–fluorite deposit in southeast Sichuan is a stratabound ore deposit which occurs mainly in Lower Ordovician carbonate rocks. Here we present results from fluid inclusion and oxygen and hydrogen isotope studies to determine the nature and origin of the hydrothermal fluids that generated the deposit. The temperature of the ore‐forming fluid shows a range of 86 to 302 °C. Our detailed microthermometric data show that the temperature during mineralization of the fluorite and barite in the early ore‐forming stage was higher than that during the formation of the calcite in the late ore‐forming stage. The salinity varied substantially from 0.18% to 21.19% NaCl eqv., whereas the density was around 1.00 g/cm³. The fluid composition was mainly H₂O (>91.33%), followed by CO₂, CH₄ and traces of C₂H₆, CO, Ar, and H₂S. The dominant cation was Na⁺ and the dominant anion Cl^‐, followed by Ca²⁺, SO₄^2‐, K⁺, and Mg²⁺, indicating a mid–low‐temperature, mid‐low‐salinity, low‐density NaCl–H₂O system. Our results demonstrate that the temperature decreased during the ore‐forming process and the fluid system changed from a closed reducing environment to an open oxidizing environment. The hydrogen and oxygen isotope data demonstrate that the hydrothermal fluids in the study area had multiple sources, primarily formation water, as well as meteoric water and metamorphic water. Combined with the geological setting and mineralization features we infer that the stratabound barite–fluorite deposits originated from mid–low‐temperature hydrothermal fluids and formed vein filling in the fault zone.