Bio-climatic imprints on a Holocene loess palaeosol from China

Micromorphology, heavy minerals, pollen and soil properties were examined in a typical Holocene loess profile in the north of the Loess Plateau, consisting of a palaeosol (locally known as the Ansai palaeosol) underlain by the Malan loess and overlain by modern loess. The palaeosol consists of an upper humus-rich (AB) horizon over a clay-rich (Bt) horizon. The humus-rich horizon is intensely weathered, contains precipitated calcitic material derived from the overlying modern loess, and has both high pollen content and diversity. Clay coatings in the clay-rich horizon indicate formation by eluviation–illuviation of clay. Pedogenetic characteristics and pollen analysis imply that the vegetation during the time of most intensive soil development is likely to have been a warm-temperate forest. A complex interpretation of the loess–palaeosol sequence recognizes several development stages. The phase of soil development, maximum and minimum limiting ages for which are ca. 8800 and 4400 ¹⁴C years BP, involved continuing but reduced loess deposition, and successive Holocene bio-climatic environment overprinted new features on the palaeosol.     

哈萨克斯坦北东天山浅成低温热液型金矿床成矿时代及构造背景

哈萨克斯坦北东天山地区是中亚造山带重要的浅成低温热液型金矿床产出地区,但其成矿年代学研究非常薄弱。为确定成矿时代,作者运用高精度激光40Ar/39Ar定年法对阿尔哈尔雷金矿床和乌仁科布拉克金矿床的赋矿围岩进行了年龄测定。获得阿尔哈尔雷金矿床安山岩样品20个点40Ar/39Ar等时线年龄为304±7Ma(MSWD=6),乌仁科布拉克金矿床安山玄武岩样品21个点40Ar/39Ar等时线年龄为280±6Ma(MSWD=2.4),表明哈萨克斯坦北东天山地区浅成低温热液型金矿床主要形成于晚石炭世末期-早二叠世。初步的岩石学、地球化学研究表明,哈萨克斯坦北东天山地区晚石炭世末期-二叠纪火山岩主要为流纹岩、粗安岩、玄武粗安岩、玄武安山岩、粗面玄武岩和玄武岩,具双峰式特征,主体属于高钾钙碱性和橄榄玄粗岩系列。哈萨克斯坦北东天山地区晚石炭世末期浅成低温热液型金矿床形成于碰撞晚期向裂谷的转换阶段,而二叠纪浅成低温热液型金矿床产出于陆内裂谷环境。     

内蒙古中部大青山东段二道洼岩群分布区金矿找矿方向

古元古代二道洼岩群分布区已发现一批金矿床和金矿化点。它们均赋存于该岩群上部层位内。主要控制金矿成矿的因素为层位 +岩性 +剪切变形变质带。因此只要有该岩群上部层位的存在 ,又有金化探异常 ,那就可能找到新的金矿床。     

Geology, Genetic Types and Metallogeny of Gold Deposits in the Eastern Tianshan, Xinjiang

As a typical Palaeozoic island arc system, the eastern Tianshan area, Xinjiang, is different from eastern China but similar to the Meso-Cenozoic island arc metallogenic provinces along the coast of the Pacific Ocean in metallogenic environment, geology and geochemistry. Three types of gold deposits, ductile shear zone-hosted gold deposits (Kanggur ), magmatic hydrothermal gold deposits (Jinwozi) and volcanic- or subvolcanic-hosted gold deposits (Xitan and Mazhuangshan), have been identified in this area. Regionally, gold deposits are structurally controlled by the Kanggur Tag ductile shear zone, Shaquanzi fault, Hongliuhe fault and Yamansu fault. Generally, gold mineralization occurs in the transition zones from volcanic rocks to sedimentary rocks. The horizon bearing well-developed jasper is an important indicator for gold mineralization. Each of the three types of gold deposits has its distinctive metallogenic background and geological-geochemical characteristics.     

休宁县大丘田地区金矿成矿地质条件和找矿前景

休宁县大丘田地区与毗邻的江西大背坞、金家坞金矿同处于一条北东向成矿带上。大丘田地区地质构造条件有利,北东向分布的玄武岩带造就了该区得天独厚的优势,规模巨大成带分布的地球化学异常,分布众多的矿点矿化点特别是近年发现的大丘田金矿点,都充分表明了大丘田地区具有良好的找矿前景。     

Geology, Geochemistry and Genesis of the Hongshijing Gold Deposit in Ruoqiang,Xinjiang

1IntroductionTheHongshijinggolddepositislocatedinthenorthofLuobupouLakeofRuoqiang ,about 30 0kmsouthwestofHamiCity ,Xinjiang .ItwasdiscoveredbytheSixthGeologicalTeamofXinjiangduringgeo chemicalexploration .TheHongshijinggolddeposit,whichoccursinthegold bearingformationcomposedofMiddleandLateCarboniferousvolcanicandpyroclasticrocks ,isabrittle ductileshearzonetypegolddepositcontrolledbyariftbelt.TheHongshijinggolddepositislocatedinthesouthwestoftheHongshi jing -Maotoushanmineralizationb…     

Deep－Source Ore－Forming Materials and Prospecting of Gold Deposits in Eastern Hebei,China

Eastern Hebei Province is one of the important gold mineralization areas in North China,and detailed investigations have been made in this area.Different mineralization models and different ore-formng surces have been proposed for the gold deposits in this area.As more detailed work was made and more information has been accumulated,it is necessary to make a new investigation on gold metallogenesis and its source.This paper presents the data about 13 gold deposits(occurrences.)It is concluded that the element gold came from the deep mantle.Different models of metallogenesis substantially describe such processes that ore-forming fluids were involved in metallogenesis in different favorable loci.Gold ore prospecting should be focused on fluid channel ways and favorable structures.     

A rendzina from the Lower Carboniferous of South Wales

ABSTRACT A thin calcrete-crust horizon from the Lower Carboniferous Llanelly Formation of South Wales consists of two parts; an upper laminated unit and a lower peloidal unit. The former is interpreted as a subaerial stromatolite and the latter as an A horizon of a palaeosol. Comparisons are made with the A horizons of rendzinas and it is concluded that the calcrete-crust represents a complete rendzina profile. This fossil rendzina contains abundant evidence of a soil fauna in the form of fecal pellets and small burrows.     

云南省宾川县白象厂金矿地质特征及成矿规律探讨

通过对白象厂金矿的区域地质概况、矿区地质特征及控矿因素的分析研究，认为，白象厂金矿产于二长斑岩与玄武岩接触带上，局部赋存于二长斑岩与大理岩、玄武岩与大理岩的接触带上，呈脉状，似层状透镜状产出。矿化受构造及岩浆岩联合控制。矿床为构造破碎斑岩蚀变型金矿床。根据该矿床的控矿规律，认为沿金矿化带的走向和倾向方向上可能找到厚大、品位高的金矿体或金的次生富集体。     

新疆卡拉麦里地区金成矿流体和O、H、S同位素地球化学特征

卡拉麦里金矿带位于准噶尔北缘和阿尔曼太至北塔山以南地区,成矿带划分属卡拉麦里—达尔布特成矿带(Ⅲ级成矿带)的卡拉麦里—莫钦乌拉成矿带(Ⅳ级成矿带),是新疆重要的金多金属成矿带。对双泉、南明水、苏吉泉等金矿床流体包裹体,氢、氧同位素和硫同位素研究表明,主成矿期成矿温度一般在200～230℃,属中低温;盐度(质量分数)一般为3.55%～4.5%,属低盐度;成矿流体为C-O-H-N-S体系。除库布苏金矿床成矿流体主要为岩浆水外,其他金矿床的成矿流体以变质水为主,但也兼具有岩浆水、建造水和/或大气降水的特征。双泉、南明水金矿中的硫主要来自变质的围岩,可能有部分深源岩浆硫的混入;金山沟、柳树泉金矿床的硫同位素组成具有深源硫的特征,成矿可能与火山、次火山活动有关。     

The formation of auriferous quartz-sulfide veins in the Pataz region, northern Peru: A synthesis of geological, mineralogical, and geochemical data

The Pataz region in the eastern part of the North Peruvian Department La Libertad hosts a number of important gold mining districts like La Lima, El Tingo, Pataz, Parcoy, and Buldibuyo. Economic gold mineralization occurs in quartz-sulfide veins at the margin of the calc-alkaline Pataz Batholith, that mainly consists of granites, granodiorites, and monzodiorites. The batholith is of Paleozoic age and cuts the Precambrian to Early Paleozoic low-grade metamorphic basement series. Its intrusion was controlled by a NNW-trending fault of regional importance. The gold-bearing veins are characterized by a two-stage sulfide mineralization. Bodies of massive pyrite and some arsenopyrite were formed in stage 1, and after subsequent fracturing they served as sites for deposition of gold, electrum, galena, sphalerite, and chalcopyrite. It is concluded that gold was transported as a AuCl ₂ ^- -complex by oxidizing chloride solutions and deposited near older pyrite by micro-scale redox changes and a slight temperature decrease. Mineralogical, textural, geochemical, and microthermometric features are interpreted as a consequence of mineralization at considerable depth produced by a hydrothermal system linked with the emplacement of the Pataz Batholith. acteristics in order to outline a general physicochemical model of the hydrothermal ore-forming processes.     

Isotopic Geochronology of the Late Paleozoic Kanggur Gold Deposit of East Tianshan Mountains, Xinjiang, NW China

Abstract: The Kanggur gold deposit lies in East Tianshan mountains, eastern section of Central Asia orogenic belt. The gold mineralization occurs on the northern margin of the Aqishan‐Yamansu Paleozoic island arc in the Tarim Plate. It was hosted mainly in Middle‐Lower Carboniferous calc‐alkaline volcanic rocks, and controlled by the distributions of syn‐tectonic intrusions and ductile shear zones. In order to determine ore‐forming age of the Kanggur deposit, samples were collected from ores, wall rocks, altered rocks and intrusions. The dating methods include Rb‐Sr isochron and Sm‐Nd isochron, and secondly ⁴⁰Ar/³⁹Ar age spectrum, U‐Pb and Pb‐Pb methods. Based on the mineral assemblage and crosscutting relationship of ore veins, five mineralization stages are identified. This result is confirmed by isotope geochronologic data. The first stage featuring formation of pyrite‐bearing phyllic rock, is mineralogically represented by pyrite, sericite and quartz with poor native gold. The Rb‐Sr isochron age of this stage is 2905 Ma. The second stage represents the main ore‐forming stage and is characterized by native gold–quartz–pyrite–magnetite–chlorite assemblage. Magnetite and pyrite of this stage are dated by Sm‐Nd isochron at 290.47.2 Ma and fluid inclusion in quartz is dated by Rb‐Sr isochron at 282.35 Ma. The third mineralization stage features native gold–quartz–pyrite vein. In the fourth stage, Au‐bearing polymetallic sulfide‐quartz veins formed. Fluid inclusions in quartz are dated by Rb‐Sr isochron method at 25821 Ma. The fifth stage is composed of sulfide‐free quartz–carbonate veins with Rb‐Sr age of 2547 Ma. The first and second stages are related to ductile‐brittle deformation of shear zones, and are named dynamo‐metamorphic hydrothermal period. The third to fifth stages related to intrusive processes of tonalite and brittle fracturing of the shear zones, are called magmato‐hydrothermal mineralization period. The Rb‐Sr isochron age of 2905 Ma of the altered andesite in the Kanggur mine area may reflect timing of regional ductile shear zone. The Rb‐Sr isochron age of 28216 Ma of the quartz‐syenite porphyry and the zircon U‐Pb age of 2757 Ma of tonalite in the north of Kanggur gold mine area are consistent with the age of gold mineralization (290‐254 Ma). This correspondence indicates that the tonalite and subvolcanic rocks may have been related to gold mineralization. The Rb–Sr, Sm‐Nd and U‐Pb ages and regional geology support the hypothesis that the Kanggur gold deposit was formed during collisional orogenesis process in Late Variscan.     

The Nassara gold prospect,Gaoua District,southwestern Burkina Faso

The Nassara-Au prospect is located in the Birimian Boromo Greenstone Belt in southwestern Burkina Faso. It is part of a larger mineralized field that includes the Cu–Au porphyry system of Gaoua, to the north. At Nassara, mineralization occurs within the West Batié Shear Zone that follows the contact between volcanic rocks (basalt and andesite) and volcano-sediments (pyroclastics and black shales) at the southern termination of the Boromo Belt. Gold is associated with pyrite and other Fe-bearing minerals that occur disseminated within the sheared volcanic and volcano-sedimentary rocks. In particular, highest grades are distinguished in alteration halos of small quartz–albite–ankerite veins that form networks along the shear zone. Here, pyrites are marked by As-poor and As-rich growth zones, the latter containing gold inclusions. Gold mineralization formed during D2_NA. Subsequent shear fractures related to D3_NA related are devoid of gold. Nassara is a classical orogenic gold occurrence where gold is associated to disseminated pyrite along quartz veins.     

Episodes of Cenozoic Gold Mineralization on the Eastern Margin of the Qinghai-Tibet Plateau:~(40)Ar/~(39)Ar Dating and Implication for Geodynamic Events

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.     

黑龙江三道湾子金矿床火山岩-次火山岩年代学、地球化学和地质意义

三道湾子金矿床位于小兴安岭北麓,是典型的以碲金化合物为主的矿床,为了限定其成矿时代和厘定其成矿地质背景,笔者对同成矿地质体火山岩和成矿期后的玄武粗安玢岩的单颗粒锆石U-Pb年龄和元素地球化学进行测定,获得同成矿地质体粗面英安斑岩及玄武粗安玢岩的~(206)Pb/~(238)U年龄加权平均值分别为(124.2±0.9)Ma(MSWD=0.5,n=18)和(118.9±2.3)Ma(MSWD=0.5,n=6);赋矿围岩为玄武粗安岩与同成矿地质体粗面英安斑岩,Si O2含量为52.75%~62.30%,K_2O和Na_2O含量分别为2.02%~2.85%和3.96%~4.24%。里特曼指数(δ)在0.85~3.67之间,属于钙碱性到高钾钙碱性岩系特征;成矿期后脉岩玄武粗安玢岩,SiO_2含量为51.53%~52.32%,K_2O含量为2.30%~2.36%,Na_2O含量为3.78%~4.14%,里特曼指数(δ)在4.05~4.86之间;微量和稀土元素均显示富集大离子亲石元素(Cs、K、Rb、Ba、LREE等),相对亏损高场强元素(Nb、Ta、Zr、Hf等)和HREE,特别是强烈亏损Th、U和Nb、Ta的特征,与岛弧钙碱性玄武岩相似。研究揭示了该矿床形成于早白垩世(124~119 Ma)或晚中生代造山后伸展构造环境,成矿热动源可能是交代大洋性质的岩石圈地幔。     

内蒙古金厂沟梁金(铜)矿床的PGE、铁族和亲硫元素的地球化学特征与物质来源、形成环境

首次采用盐酸-过氧化氢封闭熔矿与ICP-MS相结合的方法,对金厂沟梁金(铜)矿床东、西两矿区典型矿石的铂族元素(PGE)、亲铁以及亲硫元素的含量进行了系统测定,结果显示矿石中上述元素的含量均高于实验的检测限;地球化学演化特征显示含矿流体具有岩浆性质,PGE对原始地幔/球粒陨石标准化后的配分曲线均呈强烈左倾斜的分馏模式,其配分曲线和与幔源岩浆有关的富铜硫化物和富铜镍硫化物熔体的形式相似,并与幔源玄武岩、碳酸盐熔体的配分模式基本一致,反映含矿流体具有幔源岩浆属性;从区域构造、岩浆热事件角度出发,结合典型斑岩铜(钼)矿床的PGE特征,初步确定其含矿流体形成于中生代大陆边缘环境,其直接的热动源是中生代底侵的玄武岩浆。成矿阶段富含金、铜矿石的Pd/Pt、Pd/Ir比值接近低钛玄武岩浆以及玄武安山岩,而成矿早阶段贫金、铜样品的Pd/Pt、Pd/Ir比值接近地幔;反映早期含矿流体可能是直接来自中生代幔源玄武质岩浆结晶分异,而富金(铜)流体的形成可能是玄武质岩浆演化晚期被地壳物质强烈混染后的富超临界流体岩浆(低钛熔体)发生岩浆与流体分离而产生;含矿流体演化过程的PGE地球化学行为与Cu或S(As)的饱和度有关,即主要受亲硫(铜)元素或结晶分异的硫化物矿物相所制约。     

Structural and geochronological studies on the Liba goldfield of the West Qinling Orogen, Central China

The Liba goldfield, located to the northeast of the Zhongchuan Granite in the West Qinling Orogen (WQO) of mainland China, contains the largest known gold resource of 2.8 Moz in the Zhongchuan area. Devonian metasedimentary rocks host the structurally controlled gold mineralization, which is associated with silica–sericite–chlorite–carbonate alteration. Two major styles of mineralization occurred at the goldfield, which are disseminated sediment-hosted and quartz vein hosted types. Pyrite, arsenopyrite, and arsenian pyrite are major gold carriers and gold also occurs as native gold grains and electrum spatially associated with the sulfides. Numerous felsic/intermediate dykes have a similar structural control as the mineralization, and their contacts with host rocks are recognized as favorable zones for mineralization. Detailed fieldwork in conjunction with geochronological studies has helped to define the deformation history and gold metallogenesis of the goldfield. Three major phases of deformation have been recognized in the Zhongchuan area. The first deformation (D₁) event was compressional in broadly a N–S orientation, the second (D₂) event was also compressional and orientated in a NE–SW direction, and the third (D₃) event was post-mineralization and was associated with the emplacement of barren calcite and anhydrite veins. Compression related to D₂ is the key process that controlled the distribution of igneous dykes and gold mineralization in the Liba goldfield. Both igneous and hydrothermal fluids preferentially focused along dilational jogs under local trans-extension, which took place during the late stage of D₂. Precise dating with high-resolution ion microprobe (SHRIMP) U–Pb on zircon and ⁴⁰Ar/³⁹Ar on muscovite, biotite, hornblende, and plagioclase of crosscutting pre-mineralization granitic porphyry and diorite dykes have constrained the mineralization age to after ca. 227 Ma. ⁴⁰Ar/³⁹Ar analysis of minerals formed in hydrothermal alteration zones associated with gold mineralization indicates that there was a widespread ca. 216 Ma hydrothermal event that affected almost all lithologies in the area. This detailed investigation is the first study to tightly constrain the timing of gold mineralization in the WQO. The broadly overlapping timing and similar structural control of the mineralization and igneous dykes show a promising correlation, which could be potentially used to map this Late Triassic gold mineralization event in the WQO.     

川南盐源桃子乡地区玄武岩型铜矿床地质特征及找矿方向

分布于盐源桃子乡一带的峨眉山玄武岩具有厚度大、构造应力集中和深部有基性、中酸性、酸性系列岩浆侵入活动等特征,具备形成规模以上矿床的潜力。近年来,随着全国矿产资源潜力评价工作的有力推进,有关峨眉山玄武岩型铜矿床成矿理论研究已取得了一些重要成果,但勘查效果不佳。文章综合利用研究区内最新的地质勘查、地球物理勘测成果,重点讨论了区内玄武岩型铜矿床的成矿规律和找矿前景,认为矿化受层位和构造热液控制,并进一步明确了矿体与地层、岩性及构造之间的成因联系。     

Geology and Metallogenesis of the Sawayaerdun Gold Deposit in the Southwestern Tianshan Mountains, Xinjiang, China

The Sawayaerdun gold deposit, located in Wuqia County, Southwest Tianshan, China, occurs in Upper Silurian and Lower Devonian low‐grade metamorphic carbonaceous turbidites. The orebodies are controlled by a series of NE‐NNE‐trending, brittle–ductile shear zones. Twenty‐four gold mineralized zones have been recognized in the Sawayaerdun ore deposit. Among these, the up to 4‐km‐long and 200‐m wide No. IV mineralized zone is economically the most important. The average gold grade is 1–6 g/t. Gold reserves of the Sawayaerdun deposit have been identified at approximately 37 tonnes and an inferred resource of 123 tonnes. Hydrothermal alteration is characterized by silicification, pyritization, arsenopyritization, sericitization, carbonatization and chloritization. On the basis of field evidence and petrographic analysis, five stages of vein emplacement and hydrothermal mineralization can be distinguished: stage 1, early quartz stage, characterized by the occurrence of quartz veins; stage 2, arsenopyrite–pyrite–quartz stage, characterized by the formation of auriferous quartz veinlets and stockworks; stage 3, polymetallic sulfide quartz stage, characterized by the presence of auriferous polymetallic sulfide quartz veinlets and stockworks; stage 4, antimony–quartz stage, characterized by the formation of stibnite–jamesonite quartz veins; and stage 5, quartz–carbonate vein stage. Stages 2 and 3 represent the main gold mineralization, with stage 4 representing a major antimony mineralization episode in the Sawayaerdun deposit. Two types of fluid inclusion, namely H₂O–NaCl and H₂O–CO₂–NaCl types, have been recognized in quartz and calcite. Aqueous inclusions show a wide range of homogenization temperatures from 125 to 340°C, and can be correlated with the mineralization stage during which the inclusions formed. Similarly, salinities and densities of these fluids range for each stage of mineralization from 2.57 to 22 equivalent wt% NaCl and 0.76 to 1.05 g/cm³, respectively. The ore‐forming fluids thus are representative of a medium‐ to low‐temperature, low‐ to medium‐salinity H₂O–NaCl–CO₂–CH₄–N₂ system. The δ³⁴S_CDT values of sulfides associated with mineralization fall into a narrow range of ?3.0 to +2.6‰ with a mean of +0.1‰. The δ¹³C_PDB values of dolomite and siderite from the Sawayaerdun gold deposit range from ?5.4 to ?0.6‰, possibly reflecting derivation of the carbonate carbon from a mixed magmatic/sedimentary source. Changes in physico‐chemical conditions and composition of the hydrothermal fluids, water–rock exchange and immiscibility of hydrothermal fluids are inferred to have played important roles in the ore‐forming process of the Sawayaerdun gold–antimony deposit.     

Decrepitation Thermometry and Compositions of Fluid Inclusions of the Damoqujia Gold Deposit,Jiaodong Gold Province,China:Implications for Metallogeny and Exploration

The recently discovered Damoqujia (大磨曲家) gold deposit is a large shear zone-hosted gold deposit of disseminated sulphides located in the north of the Zhaoping (招平) fault zone, Jiaodong (胶东) gold province, China. In order to distinguish the temperature range of cluster inclusions from different mineralization stages and measure their compositions, 16 fluid inclusions and 5 isotopic geochemistry samples were collected for this study. Corresponding to different mineralization stages, the multirange peaks of quartz decrepitation temperature (250-270, 310-360 and 380-430℃(2) indicate that the activity of ore-forming fluids is characterized by multistage. The ore-forming fluids were predominantly of high-temperature fluid system (HTFS) by CO2-rich, and SO2-4-K type magmatic fluid during the early stage of mineralization and were subsequently affected by low-temperature fluid system (LTFS) of CH4-rich, and Cl--Na /Ca2 type meteoric fluid during the late stage of mineralization. Gold is transferred by Au-HS- complex in the HTFS, and Au-Cl- complex can be more important in the LTFS. The transition of fluids from deeper to shallow environments results in mixing between the HTFS and LTFS, which might be one of the most key reasons for gold precipitation and large-scale mineralization. The ore-forming fluids are characterized by high-temperature, strong-activity, and superimposed mineralization, so that there is a great probability of forming large and rich ore deposit in the Damoqujia gold deposit. The main bodies are preserved and extend toward deeper parts, thereby suggesting a great potential in future.