Sources of ore-forming fluids and metallic materials in the Jinwozi lode gold deposit, eastern Tianshan Mountains of China

This paper presents gas compositions and H-, O-isotope compositions of sulfide- and quartz-hosted fluid inclusions, and S-, Pb-isotope compositions of sulfide separates collected from the principal Stage 2 ores in Veins 3 and 210 of the Jinwozi lode gold deposit, eastern Tianshan Mountains of China. Fluid inclusions trapped in quartz and sphalerite are dominantly primary. H- and O-isotopic compositions of pyrite-hosted fluid inclusions indicate two major contributions to the ore-forming fluid that include the degassed magma and the meteoric-derived but rock 18O-buffered groundwater. However, H- and O-isotopic compositions of quartz-hosted fluid inclusions essentially suggest the presence of groundwater. Sulfide-hosted fluid inclusions show considerably higher abundances of gaseous species CO2, N2, H2S, etc. Than quartz-hosted ones. The linear trends among inclusion gaseous species reflect the mixing tendency between the gas-rich magmatic fluid and the groundwater. The relative enrichment of gaseous species in sulfide-hosted fluid inclusions, coupled with the banded ore structure indicating alternate precipitation of quartz with sulfide minerals, suggests that the magmatic fluid has been inputted to the ore-forming fluid in pulsation. Sulfur and lead isotope compositions of pyrite and galena separates indicate an essential magma derivation for sulfur but the multiple sources for metallic materials from the mantle to the bulk crust.     

Laser probe 40Ar-39Ar ages of metasomatic K-feldspar from the Hougou gold deposit, northwestern Hebei Province, China

The Hougou gold deposit in northwestern Hebei is a typical K-metasomatism-related gold deposit hosted by K-altered rocks overprinting alkali intrusive rocks. In order to determine the age and pulse intervals of K-metasomatism in this gold deposit, some metasomatic K-feldspars from K-altered rocks are selected to measure their formation time by laser probe 40Ar-39Ar dating method. The new analyzing data show that these metasomatic K-feldspar formed during 202.6 Ma and 176.7 Ma, and the corresponding K-metasomatism and associated gold mineralization occurred in the early stage of Mesozoic era. The pulse intervals of K-metasomatism in the Hougou area are estimated to be about 4 Ma.     

Ore-forming fluid and metallization of the Huanggangliang skarn Fe-Sn deposit, Inner Mongolia

Two kinds of inclusions, fluid-melting inclusion and gas-liquid inclusion, are present in the Huanggangliang deposit in eastern Inner Mongolia. Temperature ranges from 1050°C of fluid-melting inclusion to 150°C of liquid inclusion. Away from intrusion, the inclusions of orebodies intend to be characterized by simpler type, lower temperature and lower salinity, as well as weakened relation to intrusion. The metallization of the Huanggangliang deposit is characterized by multiple activities of ore-forming fluid, multi-source, multi-stage accumulation of ore-forming material, F-rich environment, enrichment of F, organic gas, CO₂ and N₂, and involving of residual magma.     

安徽省霍山县东溪-南关岭金矿地质特征与成矿条件

东溪-南关岭金矿为北淮阳东段发现的第一个原生金矿,产于磨子潭-晓天中生代火山盆地边缘,容矿围岩为安山质-英安质火山岩,矿化和蚀变受桐柏-桐城深大断裂带的次级构造带控制。该金矿发育陡倾斜的脉状矿体和缓倾斜的似层状矿体,成因类型为冰长石-绢云母型浅成低温热液金矿。火山岩盆地之下的变质基底可能起到了初始矿源层作用,桐柏-桐城断裂带及其次级构造破碎带为重要的导岩导矿构造,早白垩世强烈的岩浆活动提供了热源、动力源和部分矿源。参照国内外类似金矿的特征,认为本区成矿地质条件良好,有可能隐伏着与石英正长岩体有关的细脉浸染型矿化,晓天火山盆地具有良好的找矿前景。     

Ore-forming mechanism for the Xiaoxinancha Au-rich Cu deposit in Yanbian,Jilin Province,China: Evidence from noble gas isotope geochemistry of fluid inclusions in minerals

The Xiaoxinancha Au-rich copper deposit is one of important Au-Cu deposits along the continental margin in Eastern China. The deposit consists of two sections: the Beishan mine (North), composed of altered rocks with veinlet-dissemination sulfides and melnicovite-dominated sulfide-quartz veins, and the Nanshan mine (South), composed of pyrrhotite-dominated sulfide-quartz veins and pure sulfide veins. The isotope compositions of noble gases extracted from fluid inclusions in ore minerals, i.e. ratios of 3He/4He, 20Ne/22Ne and40Ar/36Ar are in the ranges of 4.45―0.08 Ra, 10.2―8.8 and 306―430, respectively. Fluid inclusions in minerals from the Nanshan mine have higher 3He/4He and 20Ne/22Ne ratios whereas those from the Beishan mine have lower 3He/4He ratios. The analysis of origin, and evolution of the ore fluids and its relations with the ore-forming stages and the ages of mineralization suggests that the initial hydrothermal fluids probably come from the melts generated by partial melting of oceanic crust with the participation of fluids from the mantle (mantle-plume type)/aesthenosphere. This also corresponds to the continental margin settings during the subduction of Izanagi ocaneic plate towards the palaeo-Asian continent (123―102 Ma). The veinlet-dissemination ore bodies of the Beishan mine were formed through replacement and crystallization of the mixed fluids generated by mixing of the ascending high-temperature boiling fluid with young crustal fluid whereas the melnicovite-dominated sulfide-quartz veins were formed subsequently by filling of the high-temperature ore fluid in fissures. Pyrrhotite-dominated sulfide-quartz veins in the Nanshan mine were formed by filling-deposition-crystallization of the moderate-temperature ore fluids and the pure sulfide veins were formed later by filling-deposition-crystallization of ore substance-rich fluids after boiling of the moderate-temperature ore fluids. The metallogenic dynamic processes can be summarized as: (1) formation of fluidand ore substance-bearing Adakitic magma by degassing, dewatering and partial melting during subduction of the Izanagi plate; (2) separation and formation of ore fluids from the Adakitic magma; and (3) success-sive ascending of the ore fluids and final formation of the Au-rich Cu deposit of veinlet-dissemination and vein types by secondary boiling.     

地磁空间相关法在河北省的应用研究

通过对河北省境内8个地磁台站1981-2006年Z21地磁资料的相关分析,发现地磁Z21相关系数异常与河北省及邻区MS≥5.0地震有较好的对应关系:26年内共出现了符合判据标准的异常18次,在其后10个月内对应地震13次,应报15个,虚报3次,漏报2次。初步给出了适合该区域的地震预报参数。     

Origin of Mesozoic gold mineralization in South Korea

Abstract   The Mesozoic gold–silver deposits in South Korea are closely associated with the Mesozoic granitoids. The Jurassic gold–silver deposits can be distinguished from the Cretaceous ones in terms of occurrence, alteration style, gold fineness, associated mineral assemblage, fluid inclusion and stable isotopic compositions. The Jurassic deposits were formed in mesozonal environments related to deep-seated granitoids, whereas the Cretaceous ones were formed in epizonal environments related to shallow-level granitoids. The Jurassic auriferous deposits (about 165–145 Ma) show fluid characteristics typical of an orogenic-type gold deposit, and were probably generated in a compressional regime caused by an orthogonal convergence of the Izanagi oceanic plate into the Asiatic margin. However, strike-slip faults and caldera-related fractures, together with subvolcanic to volcanic activity, may have played an important role in the formation of Cretaceous gold–silver lode deposits (about 110–45 Ma) under a continental arc setting.     

河南范疙瘩金矿床矿体定位的构造控制

范疙瘩金矿位于熊耳山断隆的东南部,马超营断裂带的北侧,金矿体产于北西向M14断裂带内。本文通过研究断裂构造的方向、规模、分布特征,分析断裂活动历史及矿体产出特征,总结成矿规律。金矿体严格受M14断裂控制,离断裂越远金矿化越弱,M14断裂带倾向上引张部位及断裂分支复合部位是金元素的富集地段,是成矿有利部位。     

Experimental study of gold activation-transportation in the process of potash metasomatism-alteration——North China platform gold deposit taken as an example

Chemical reactions of plagioclase, biotite and their singleminerals, as well as a mineral mixture of (plagioclase +biotite+quartz), with KCl and (KCl+KHCO3) solutions were carried out at 150400℃ and 5080 MPa. Experiments show that alkaline fluid promotes plagioclase’s changing into potash feldspar, while acid fluid helps plagioclase, potash feldspar and biotite alteration form chlorite and sericite. After chemical reaction the acidity-alkalinity of solutions often changes reversely. It was observed that gold dissolved from the tube wall and recrystallized on the surfaces of biotite and pyrite. Therefore the transportation and enrichment of gold are related to the elementary effect of the fluid-mineral interfaces. Fe3+-Fe2+, as an oxidition-reduction agent, and volatile components Cl? and CO2 play important roles in the reaction process.     

Pb-Sr isotopic evidence for contribution of deep crustal fluid to the Hishikari epithermal gold deposit, southwestern Japan

The gold-bearing quartz-adularia veins of the world-class Hishikari mine in southwestern Japan occur in a geological regime where the rocks of the upper to middle crust are simple and their chemical and Sr-Nd-Pb isotopic compositions are well studied. Detailed comparison of Pb and Sr isotopic data of the Hishikari veins with those of all possible source materials demonstrates that metals in the veins were essentially derived from a mixture of magmatic fluid with a deep crustal fluid that originated near the boundary between the Shimanto middle crust and the underlying subcontinental crustal materials. We propose that the release of the deep crustal fluid was triggered by intrusion of the Shishimano rhyodacite magma related to timing of the mineralization. This fluid mixture carried metals to the brittle upper crust along fissures created by extensional stress forming the ore deposits. Although the deep crustal fluid has not been paid much attention, it may be distributed over a large scale in the deep crust from the continent to the arc system and play an important role in the genesis of magmatic-hydrothermal ore deposits and in the generation of flow-induced deep tremor.     

Study on the carbonate ocelli-bearing lamprophyre dykes in the Ailaoshan gold deposit zone, Yunnan Province

Three carbonate ocelli-bearing lamprophyre dykes have been found in the Laowangzhai and Beiya gold orefields in the northern sector of the Ailaoshan gold deposit zone, Yunnan Province. Ocelli in the lamprophyre dykes are carbonates composed mainly of dolomite and calcite. Their trace elements, REE and C isotopic compositions are characteristic of carbonatite and the main mineral assemblages, major elements, trace elements and REE in the matrix are similar to those in the carbonate ocelli-barren lamprophyre dykes in the orefields, which are calc-alkaline lamprophyres that derived from the fertile mantle. The results indicate that the carbonate ocelli-bearing lamprophyre dykes in this area were produced at the time when the Himalayan lamprophyre magma evolved to a relatively late stage of silicate-carbonate liquid immiscibility. In the process of magmatic evolution there took place magmatic degassing with CO₂ and H₂O as the dominant released gases.     

滇西北地区活动构造温泉水汞背景值观测研究

采用流动采样、定点观测分析方法,对滇西北地区部分典型活动断裂带上天然出露的温泉,进行水汞背景值(本底值)调查和观测研究,得出各点位温泉中水汞的正常变化范围、空间分布特征,以及与活动构造的关系,用于滇西北地区地震短临跟踪加密观测,以及强震现场周围的前兆异常监视工作。     

江西港南红土型金矿地质特征及成因探讨

江西省瑞昌市港南金矿是上世纪八十年代发现的小型金矿床,前人称之为＂铁帽＂型。本文通过对以往勘查资料的进一步分析和野外调查,发现矿体受F1硅化破碎带及溶蚀侵蚀洼地控制,产于破碎带之上的溶蚀侵蚀洼地粘土层中,顶板较平整,底板随基岩侵蚀面的起伏而波动,初步认为属残积红土型金矿,矿区及外围具有进一步找矿的前景。     

Laser probe <Superscript>40</Superscript>Ar-<Superscript>39</Superscript>Ar ages of metasomatic K-feldspar from the Hougou gold deposit,northwestern Hebei Province,China

The Hougou gold deposit in northwestern Hebei is a typical K-metasomatism-related gold deposit hosted by K-altered rocks overprinting alkali intrusive rocks. In order to determine the age and pulse intervals of K-metasomatism in this gold deposit, some metasomatic K-feldspars from K-altered rocks are selected to measure their formation time by laser probe ⁴⁰Ar-³⁹Ar dating method. The new analyzing data show that these metasomatic K-feldspar formed during 202.6 Ma and 176.7 Ma, and the corresponding K-metasomatism and associated gold mineralization occurred in the early stage of Mesozoic era. The pulse intervals of K-metasomatism in the Hougou area are estimated to be about 4 Ma.     

Ore-forming fluid constraints on illite crystallinity (IC) at Dexing porphyry copper deposit, Jiangxi Province

Illite, a distinctive kind of clay minerals of potassium alteration within the hydrothermal alteration zone, frequently occurs at the Tongchang porphyry copper deposit ore field. The illite crystallinity (IC) value and expandability are mainly affected by water/rock ratio or fluid flux. It was formed by illitization of plagioclase and micas during hydrothermal fluid-rock interaction within the porphyry body and near the contact zone with wall rocks. Moreover, the negative correlation between illite index (IC) and copper grade indicates that within the alteration zone, the smaller the illite crystallinity value, the higher the alteration degree, and the higher the copper grade due to higher water/rock ratio. At lower levels of the porphyry body, however, the illite crystallinity (IC) values are mainly controlled by temperature and time duration.     

基于二维经验模态分解的河北省及邻区流动重力场时空动态变化分析

搜集河北省及邻区2010—2019年20期的流动重力观测数据和绝对重力观测数据,利用二维经验模态分解方法获取河北省及邻区范围内(110°E～120°E,36°N～42°N)不同尺度、不同场源深度下的分解结果,并结合该时间段内M≥4.0震例进行回溯性检验。结果表明,当半年时间尺度与一年时间尺度下的1阶、2阶固有模态函数结果出现正-负重力高值差异或四象限异常变化时,在异常变化中心200km范围内存在2年内发生M4.0以上中强地震的可能。该结论可为河北省及邻区后续震情分析和研判提供参考。     

河北省地磁场变化规律研究

利用河北省地磁台1986～2005年的地磁观测资料,对该地区地磁场长期变化规律进行总结分析.这进一步认识了河北省地磁场变化规律及其特征,为地震预报提供有实用价值的第一手资料十分有意义.     

河北省40年防震减灾工作回顾与展望--纪念邢台地震40周年

40年来,河北的防震减灾工作在中国地震局和省委、省政府的领导下,全省地震工作者和各有关部门,为建立、推进和发展我省的防震减灾事业做出了不懈的努力和探索,特别是“九五”、“十五”以来,我省认真贯彻落实党和国家关于防震减灾的各项方针、政策,在加强领导、建立健全防震减灾工作体系,加大投入、夯实监测预报基础,加强综合防御、依法推进防震减灾工作,发挥政府职能作用、切实做好地震应急准备等方面,取得了一些进步与成绩。认真、全面、科学地对河北省40年来的防震减灾工作进行回顾总结,对于我们发扬成绩、开创未来,具有重要的意义。     

Geochemistry of ore-forming fluids and geological significance of the Kuoerzhenkuola gold field in Xinjiang, China

The Kuoerzhenkuola gold field (including the Kuo- erzhenkuola and the Buerkesidai gold deposits), lo- cated 68 km east of Jimunai County in northern Xing- jiang, China, is an important component of the Sawuer gold belt which is the eastward extending part of the Zarma-Sawur gold-copper belt in Kazakhstan. Some studies are concerned with the geology of the gold ores[1―3], the associated volcanic rocks[4], radiogenic isotope[5―8], and the ore-forming environment[8]. Most researchers inferr…