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湘西晚前寒武纪层状硅质岩的热水沉积地球化学标志及其环境意义 总被引：5，自引：0，他引：5
湘西晚前寒武纪层状硅质岩化学成分纯净,硅质矿物平均含量９５％以上。岩石富Ｆｅ、Ｍｎ,相对贫Ａｌ、Ｔｉ、Ｍｇ,富含Ｂａ、Ａｓ、Ｓｂ、Ａｇ、Ｕ等微量元素。Ｆｅ／Ｔｉ、（Ｆｅ＋Ｍｎ）／Ｔｉ、Ａｌ／（Ａｌ＋Ｆｅ＋Ｍｎ）、Ｕ／Ｔｈ比值及ＡｌＦｅＭｎ、ＦｅＭｎ（Ｎｉ＋Ｃｏ＋Ｃｕ）三角图均表明岩石为热水来源沉积岩。稀土元素总量低,Ｃｅ负异常,重稀土相对富集,显示主要为热水沉积作用的产物。δ３０Ｓｉ、δ１８Ｏ值及岩石的形成温度清楚地表明组成岩石的二氧化硅来源于热水。岩石的ＭｎＯ／ＴｉＯ２、δＣｅ及δ３０Ｓｉ值分析表明硅质岩沉积于大陆边缘斜坡半深海至大洋盆地深海环境中 相似文献
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浙西石炭纪层状硅质岩地球化学特征及其意义 总被引：7，自引：0，他引：7
在浙西石炭纪地层中存在与地层整合产出的层状硅质岩。硅质岩中ＦｅＯ、ＭｎＯ、ＴｉＯ２、Ａｌ２Ｏ３、ＭｇＯ、ＣａＯ、Ｎａ２Ｏ、Ｋ２Ｏ等含量相对较高，富集Ａｓ、Ｓｂ、Ｂｉ、Ａｕ、Ａｇ、Ｇａ，Ｆｅ２Ｏ３／ＦｅＯ、ＳｉＯ２／Ａｌ２Ｏ３、ＳｉＯ２／（Ｎａ２Ｏ＋Ｋ２Ｏ）、ＳｉＯ２／ＭｇＯ比值较小，稀土元素总量低，Ｃｅ弱负异常，重稀土相对富集，包裹体富含气相组份ＣＨ４、ＣＯ２、Ｎ２、ＣＯ、Ｈ２，具热水沉积硅质岩的地球化学特征。在Ｆｅ—Ｍｎ—（Ｎｉ＋Ｃｏ＋Ｃｕ）三角图及ＳｉＯ２—Ａｌ２Ｏ３、ＳｉＯ２—Ｆｅ２Ｏ３图上均属于热水沉积硅质岩。硅质岩中硅、氧同位素也显示其热水成因之特点。硅质岩的硅同位素和稀土元素Ｃｅ／Ｃｅ※值表明本区层状硅质岩主要是在浅海环境下沉积的。硅质岩的形成温度较高，为９８℃～１５２℃ 相似文献
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浙江西裘晚元古代层状硅质岩热水沉积地球化学标志及其沉积环境意义 总被引：17，自引：0，他引：17
在浙江西裘地区晚元古界地层中存在与地层整合产出的层状硅质岩。硅质岩富Ｆｅ、Ｍｎ，相对贫Ａ１，富集Ａｓ、Ｓｂ、Ｂｉ、Ｇａ，稀土元素总量低，铈负异常，重稀土相对富集，具热水沉积硅质岩的地球化学特征。在Ａ１－Ｆｅ－Ｍｎ和Ｆｅ－Ｍｎ－（Ｎｉ＋Ｃｏ＋Ｃｕ）三角图上均属于热水沉积硅质岩。硅质岩硅、氧同位素地球化学也显示其热水成因之特点。硅质岩的ＭｎＯ／ＴｉＯ２、δＣｅ和δ３０Ｓｉ值分析表明本区层状硅质岩主要是在深海环境下沉积的。硅质岩形成温度较高，约为８２－１６５℃。 相似文献
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广东长坑金银矿床含矿硅质岩的地球化学与成因 总被引：7，自引：1，他引：7
长坑矿床的金、银矿化与硅质岩关系最为密切，角砾状硅质岩矿体具层控和断裂控制双重特点。含矿硅质岩的ＳｉＯ２含量为７３％～９２％，其平均值（８８％）与海底热液燧石相近，但硅质金矿石的ＴｉＯ２、Ａｌ２Ｏ３、ＴＦｅ、ＣａＯ、Ｋ２Ｏ和银矿石的ＣａＯ、ＦｅＯ含量平均值明显高于热水沉积硅质岩；在Ａｌ Ｆｅ Ｍｎ成分三角图上，含矿硅质岩在水成区和热液区均有分布。虽然矿化硅质岩的稀土成分具海底热水沉积岩的特点，即总量较低，具Ｃｅ负异常，但其模式曲线与围岩相似。硅质矿石相对富Ｆｅ，贫Ｃｕ、Ｃｏ、Ｎｉ，过渡元素配分模式继承了围岩的特点。结合硅质矿体的地质产状、矿化年龄与成矿流体来源，认为硅质矿石主要形成于热液对围岩和裂隙的交代、充填作用，但不排除早期热水沉积硅质岩存在的可能性。 相似文献
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华北地台南缘中元古代官道口群热水沉积硅质岩的… 总被引：1，自引：0，他引：1
在简要介绍了硅质岩基本地质特征的基础上，详细讨论了该套硅质岩的常量元素，微量元素以及氧同位素化学成分及组成，研究表明，该套硅质岩富集了与热水成因有关的Ａｇ，Ａｓ，Ｃｓ，Ｐｂ，Ｚｎ，Ｃｕ，Ｂ，Ｓｂ等微量元素和ＣａＯ，ＦｅＯ，Ｆｅ２Ｏ３等氧化物中常量元素，贫化了ＴｉＯ２，Ａｌ２Ｏ３，ＭｎＯ等氧化物中的常量元素，氧同位素组成及利用氧同位素估算的硅质岩的形成温度，均反映了热水沉积的成因的特点。 相似文献
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本区金矿中黄铁矿的Ｍｏ谱测试和综合分析表明，主要穆斯堡尔参数的变化与含金性之间存在有一定的关系。主要表现为，黄铁矿的Ｉ．Ｓ．值与含金性间呈明显的负相关。Ｏ．Ｓ．值与含金性间则呈明显的正相关，且Ｏ．Ｓ．值随着（Ａｕ＋Ａｓ）／（Ｃｏ＋Ｎｉ）原子数比值的增大而增大。这是由于Ａｕ＋取代Ｆｅ２＋进入黄铁矿晶格使其结构产生畸变所致。置换时电荷补偿可通过两个途径来实现，其一是Ａｕ＋（Ｃｏ３＋、Ｎｉ３＋）→２Ｆｅ２＋，其二是Ａｓ３＋＋Ａｕ＋→２Ｆｅ２＋。 相似文献
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凤太泥盆纪拉分盆地中硅质铁白云岩—硅质岩特征及成岩成矿方式 总被引：16，自引：2，他引：14
从岩石学、矿物学、地球化学等叫结秦岭凤太地区泥盆纪硅质白云岩－硅质岩的地质地球化学特征。硅质岩类中,ＳｉＯ２〉８０％,（ＦｅＯ＋Ｆｅ２Ｏ３＋ＭｇＯ）〈１０％;硅质铁白云岩类中,ＳｉＯ２为３０％～５０％,（ＦｅＯ＋ＦｅＯ３＋ＭｇＯ）大于２０％,提出该类热水沉积岩热水同生沉积作用、热水温合同生沉积作用,热水同生沉积交代作用,热水爆炸－液压致裂作用及热水充填－交代作用形成。 相似文献
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采用纯水，氢氟酸处理样品，结合高灵敏的ＧＦＡＡＳ测定四氯化硅中超痕量Ｆｅ、Ｃｕ、Ｎｉ、Ｍｎ、Ｃｒ。方法简便、快速、灵敏度高、各元素的检出限（ｎｇ／ｍＬ）分别为Ｆｅ５，Ｎｉ０．８，Ｃｕ，Ｃｒ０．５，Ｍｎ０．２。 相似文献
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Geochemical Features and Formation of the Auriferous Cherts in the Mojiang Gold Deposit,Yunnan 总被引：1，自引：0，他引：1
Auriferous cherts in the Middle Carboniferous Jinchang Formation are the dominant host rocks of auriferous quartz veins and mixed orebodies comprised of gold-bearing quartz veins and cherts in the Mojiang gold deposit.The rocks exhibit sedimentary texture and structure and are composed of hot-water deposited minerals.The FeO,Fe2O3,Au and Ag contents of the auriferous cherts are high;the Cr,Ni and Co contents are also high but significantly variable;MnO/TiO2 and TFe/TiO2 ratios are relatively higy.As viewed from a few diagrams that distinguish different chert formations,the auriferous cherts are in or near the range of hot-water deposited cherts.Because the correlation coefficients between Au contents and those of Cr, Ni of the rocks are negative,a great Au amount in the cherts might not be brought about by later hydrothermal alterations.The rare-earth elements,O and Si isotopic compositions of the auriferous cherts demonstrate that the cherts belong to hot-water deposited rocks.The later hydrothermal alterations made the petrochemical compositions of the cherts deviate from the characteristics of hot-water deposition.In general,the geological and geochemical features of the auriferous cherts demonstrate that the rocks were formed by hot water deposition. 相似文献
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The paper discusses factors in the deposition and concentration of native gold and the spatial distribution of its individuals within the sufide-poor gold–quartz veins at the mesoabyssal Tokur deposit. The major factors in deposition of gold were sealing of the hydrothermal system, a sudden drop in fluid pressure, and repeated immiscibility in the fluid. Native gold was deposited in relation to initial acts of prolonged and discrete opening and preopening of cavities in three mineral assemblages of the productive association II. Most native gold individuals with a visible size of 0.1–1.5 mm were together with the early generation of quartz 2 on cavity walls adjacent to altered rocks. This is caused by the high content of Au complexes in initial hydrothermal solutions favoring rapid oversaturation during cavity formation. Gold fills interstices between grains of quartz 2 throughout the deposit and mineral assemblages. The vertical-flow distribution of gold has been established in economic veins; the upper and middle levels are enriched in gold, and samples with the greatest gold grade of 100–500 g/t or higher are concentrated there. This is caused both by the predominance of mineral association II at these levels and probable natural flotation of gold grains contained in the gold–gas associate for immiscibility of the hydrothermal fluid at the second stage of the ore-forming process. 相似文献
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新疆东准噶尔卡拉麦里地区以金水泉、双泉、南明水、苏吉泉东等为代表的金矿床,构成了一套与晚古生代碰撞造山有关的金成矿系统。矿床夹持于区域性的卡拉麦里深大断裂和清水—苏吉泉大断裂之间,矿化受次级脆-韧性断层控制,以中等至陡倾斜的含金石英脉和破碎蚀变岩的形式产于晚古生代浅变质火山沉积岩中。流体包裹体、H-O-S-Pb同位素和热液锆石U-Pb年代学研究表明,成矿流体具中高温(集中于240~330 ℃)、低盐度(<6% NaCleq)、富CO2的变质流体特征,成矿物质来自赋矿的火山沉积岩系,流体不混溶(相分离)和水-岩反应(围岩硫化作用)是导致金沉淀的主要机制,成矿深度变化于7~15 km之间,成矿时代约为314 Ma。晚石炭世至早二叠世,研究区的构造体制由挤压向走滑或走滑伸展转换,构造应力的释放导致深部变质脱水形成的低盐度CO2-H2O-NaCl±CH4含金流体,沿走向NW至近EW向的走滑剪切断裂向地壳浅部流动,并在脆-韧性过渡带或脆性变形带的次级断裂中形成含金石英脉及蚀变岩型金矿石。 相似文献
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采用电子探针显微分析(EMPA)和粉末X射线衍射(XRD)分析了采自乌拉山金矿床含金钾长石石英脉、石英脉以及其他类型岩石中的10 0多个钾长石样品的化学成分和结果状态,并采用R和Q模式聚类分析、Spearman等级相关分析方法对实验数据进行了统计分析。结果表明,含金矿脉、岩浆热液脉和蚀变花岗岩中的钾长石为中等到最大微斜长石,其特征为K2 O含量高,但相对而言,Na2 O、CaO和BaO的含量低。其他岩石类型中的钾长石的化学成分和结果状态变化很大,可以从透长石、正长石到微斜长石,其特征为K2 O的含量相对较低,但Na2 O、CaO和BaO的含量相对较高。含金样品中的钾长石通常更富K2 O ,表明金的成矿作用与富钾的热液流体和碱质交代作用有关。乌拉山金矿床的成矿作用分为两个阶段,主要的含金钾长石石英脉中的钾长石富K2 O ,形成温度为30 7～379℃,平均为35 3℃;第二阶段含金石英脉中的钾长石含K2 O较低,形成温度为2 6 0～318℃,平均为2 81℃。这些结果表明成矿流体与岩浆热液作用有关,流体朝温度降低、K2 O含量降低的方向演化,K2 O含量高的热液流体和2 6 0～380℃的形成温度有利于金的成矿作用。 相似文献
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新疆吐拉苏盆地京希-伊尔曼德金矿地质和地球化学特征研究 总被引：2，自引：1，他引：1
京希-伊尔曼德金矿位于新疆北天山吐拉苏盆地的西北缘,赋存于泥盆纪-早石炭世火山-沉积地层底部的凝灰岩、凝灰质砂岩中,围岩经历了绢云母化、黄铁矿化、多期硅化和角砾化、碳酸盐化和重晶石化,金矿化与硅化围岩紧密伴生。矿体呈透镜状、层状和似层状,产状与围岩基本一致,主要由热液角砾岩型矿石组成,其热液演化期由四个阶段组成:I:硅化及绢云母化——在围岩凝灰岩和凝灰质砂岩中形成大量浸染状石英、绢云母和少量黄铁矿;II:角砾化及硅化——形成含金热液角砾岩a,角砾为早期蚀变围岩,胶结物为烟灰色玉髓状石英、黄铁矿、毒砂和少量金矿物;III:角砾化及硅化——形成含金热液角砾岩b,角砾为热液角砾岩a和蚀变围岩,胶结物为细粒石英、黄铁矿、毒砂和少量金矿物;IV:方解石-重晶石阶段——形成大量粗大的方解石-重晶石脉。京希-伊尔曼德金矿成矿流体本身富集V、Cr、Ni、Cu、Sb,且其中的Mn、Co、Zn、Bi以及大离子亲石元素LILE主要来自火山岩围岩。从成矿早期到晚期,成矿流体轻稀土元素逐渐富集、氧化性增强。水-岩体系氢、氧同位素组成模拟计算表明,京希-伊尔曼德金矿成矿流体主要为与区内火山岩再平衡的岩浆水,其中金浓度为1×10-6～2×10-6,形成该矿需要约1×108～0.5×108t岩浆热液,蚀变围岩和矿石中黄铁矿富集轻稀土元素。角砾化作用及其伴随的氧逸度升高是导致金沉淀的主要机制。 相似文献
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Turbidite hosted orogenic gold mineralization in the Archean Gadag greenstone belt of the Western Dharwar Craton, forms a major auriferous zone (Central Auriferous Zone) extending over a strike length of about 12 km in the Gadag duplex. The turbidite sequence comprises thick inter-bedded, medium to coarse grained lithic graywacke and thin laminated layers of fine grained carbonaceous phyllite. Gold bearing quartz veins impregnate preferentially along the en-echelon shear planes, fractures and schistosity planes. Auriferous quartz veins are enveloped by the altered wall rocks.Mineralogy of the auriferous zone is dominated by gangue minerals like quartz, ankerite, chlorite, sericite and carbonaceous matter, with subordinate plagioclase. Monazite and xenotime are the important accessory minerals. Arsenopyrite and pyrite are the major sulfide minerals, but pyrrhotite, chalcopyrite, sphalerite, galena and scheelite are also present. Gold in native state occurs within quartz, silicates and arsenopyrite.Notable distinctions in mineral assemblage, texture and in chemical compositions of altered wall rocks compared to the precursor host rock in the study area implies that the metasomatism and wall rock alterations are the results of pervasive infiltration and intense interaction between hydrothermal fluids and the surrounding host rocks over a prolonged period.Sulfides, carbonates, carbonaceous matter, K2O, MgO, CaO, Cr, Ni, Cu, Pb, Zn, As and higher values of gold (0.98–4.72 ppm) are added into the altered wall rocks, immediately enveloping the auriferous quartz vein bodies. The chondrite normalized REE pattern of altered wall rocks exhibits enriched LREE (LaN/YbN = av. 9.54), with prominent negative Eu anomaly. The observed variation in geochemical characteristics and mineral assemblages in the alteration zones indicates differential response of the host rock and intensity of alteration depending on the composition of host rocks and hydrothermal fluids.The auriferous hydrothermal fluids were of low salinity (2.0 to 6.6 wt.% NaCl), dominated by CO2–H2O (about 30 mol% CO2) with moderate densities (0.7 to 1.04 g/cm3), and gold deposition occurred over a wide temperature range between 175 °C and 325 °C. Gold deposition was influenced by fluid mixing, phase separation and redox reactions. Mixing between CO2–H2O fluids and more reduced fluids, which evolved during fluid reaction with adjacent carbonaceous wall rocks, was the key factor causing gold deposition.The formation of the Gadag duplex, deformation, folds and reverse strike slip faults (discontinuities) was caused by the compression associated with subduction related tectonic processes. During the initial period of intrusive magmatism (2,555 ± 6 Ma), regional metamorphism occurred in the entire greenstone belt, while during later period, hydrothermal fluids responsible for gold mineralization probably were derived from metamorphic processes as well as from intrusive granites. Such fluids channeled through the thrust in host turbidite sequence carrying dissolved gold, associated metals and sulfur, ultimately were precipitated in a reducing environment in the splays to the thrust in the Gadag duplex at about 2,522 ± 6 Ma, resulting in retrograde alteration assemblages. 相似文献
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金厂特大型金矿床的地质特征与成因研究 总被引：18，自引：0，他引：18
金厂特大型金矿床产于吉黑东部兴凯地块太平岭隆起与老黑山断陷的交接部位,矿区外围出露新元古界黄松群变质岩系。本区燕山期岩浆活动可分为5期,分别为燕山早期第一阶段闪长岩(δ52-1)、燕山早期第二阶段文象花岗岩(γo52-2)、燕山早期第三阶段花岗岩(γ52-3)、燕山晚期第一阶段花岗斑岩(γπ53-1)、燕山晚期第二阶段闪长玢岩脉(δμ53-2),形成岩浆穹窿型构造和隐爆角砾岩筒构造,并叠加大规模的热液蚀变活动,金矿化与第4、5期岩浆活动紧密相关。金矿矿体产状有三种类型:岩浆穹窿构造型、隐爆角砾岩型和环状放射状断裂型。矿石类型主要有含金黄铁矿化石英脉、含金石英黄铁矿脉、含金多金属硫化物石英脉、含金黄铁矿化方解石脉等。金矿成矿年龄为119.40 -122.53 Ma。金矿体受统一的构造-岩浆流体蚀变系统控制,成矿物质来源于深部,成矿流体为岩浆水,晚阶段有少量大气水加入。成矿环境为中高温、中等压力,流体盐度为中等偏高,流体性质为弱碱性、弱还原性,属于K -Na - Ca2 -Cl--SO42-型流体。金在成矿流体中以[Au(HS)2]-、[AuCl2]-、[Au(CO3)]-及[Au(HCO3)2]-等络合物形式存在,当温度、压力下降时,溶液由酸性演化为弱酸性再到弱碱性时,络合物离解,金沉淀成矿。 相似文献
18.
焦家式金矿中铬铝云母化学成分的标型性 总被引：1，自引：1，他引：1
本文系统研究了胶东地区金矿中产出的铬铝云母亚族中３个白云母、１６个绢云母和３２个含Ｃｒ云母种属的化学成分特征。提出了含Ｃｒ云母种属结构层内四面体、八面体及层间离子种类和数量在焦家式金矿成矿过程中的指示作用，阐明了白云母、绢云母及含Ｃｒ云母种属之间的演化特征在与焦家式金矿化有关的成岩成矿作用中的标型意义。 相似文献
19.
陕西略阳煎茶岭金矿矿集区中的张家山金矿主要由破碎蚀变岩型、角砾岩型和含金石英黄铁矿脉型矿石组成。含金石英-黄铁矿脉型矿石产于断层下盘的石英菱镁岩中。黄铁矿发育富As黄铁矿边,环边受As含量的变化呈现一定的韵律变化,自然金赋存在富As黄铁矿中。在断裂发育形成断层角砾岩的过程中,流体充填破碎石英菱镁岩的裂隙中形成热液矿物,包括硫化物、硒化物以及自然金。石英菱镁岩发生破碎形成的网状裂隙被含金石英-方解石-黄铁矿脉充填。破碎蚀变岩型矿石中,自然金主要分布在含金石英-黄铁矿脉的石英之中或靠近热液脉的菱镁矿或石英间隙。随着大量方解石脉沿裂隙贯入,进一步促进石英菱镁岩的破碎及岩石角砾的分离,形成由石英菱镁岩碎屑、石英和褐铁矿组成的复成分角砾岩,自然金和硒化物呈浸染状分布在角砾岩中。笔者在角砾岩型矿石中发现了灰硒汞矿、直硒镍矿、硒铅矿等硒化物,这些硒化物往往与自然金密切共生。结合矿物组合以及相关化学反应关系,通过热力学计算,构建了该矿床在不同温度条件下的热力学相平衡关系图,限定了硒化物与其他相关矿物稳定存在的物理化学条件。硒化物一般与自然金和石英共生,高的f(Se2)值和f(Se2)/f(S2)比值是控制硒化物形成的关键因素。 相似文献
20.
Detailed hydrothermal alteration investigations, including petrography, infrared reflectance spectroscopy (IRS) and XRD of the low sulfidation epithermal Co–O mine, located in Eastern Mindanao (Philippines) revealed that both distal and intermediate hydrothermal alteration zones contain dominantly illite and chlorite, whereas the proximal alteration zone comprises mainly illite, chalcopyrite and pyrite. The gold-bearing veins and the proximal hydrothermal alteration zone display a distinct absence of K-rich hydrothermal alteration minerals such as K-feldspar (adularia).Gold mineralization in the Co–O mine is controlled by an extensive quartz-breccia vein system, which is characterized by three distinct stages of vein (incl. breccias) formation. Gold is mainly observed in stages 2 and 3 veins. Stage 1 veins appear as fragments in stage 2 veins and display boiling textures such as quartz pseudomophs after bladed calcite. These veins further display colloform to crustiform banding and contain pyrite, chalcopyrite and minor gold located in the colloform bands and between bladed quartz pseudomorphs. Stage 2 veins comprise mostly banded to massive quartz and contains sulfides parallel to bands or disseminated. These veins are fine-grained with mosaic/jigsaw quartz and contain calcite blebs and/or fragments of stage 1 veins. Gold is in textural equilibrium with chalcopyrite, sphalerite, and locally pyrite. Stage 3 veins consist of quartz and carbonate (locally Mn-rich), and display irregular banded and comb textures. In auriferous veins of this stage gold is in textural equilibrium with chalcopyrite and pyrite (with local abundance of sphalerite). Other sulfide minerals observed with gold in stages 2 and 3 are galena, acanthite and locally jalpaite.The XRD and IRS provide inconsistent results regarding the abundance of K-rich clays (e.g., illite) associated with auriferous veins. Illite, with possibly interlayered swelling clays, such as Al-smectite, was identified in auriferous vein stages 2 and 3 using IRS, but could not be confirmed by XRD. Comparative analysis of the results of these techniques with respect to the ordering of micaceous minerals, suggest less ordered white mica proximal to the veins.Vein textures such as banded quartz, the absence of K-feldspar and the abundance of illite (interlayered Al-smectite) suggest relatively low temperatures of formation of the hydrothermal alteration system and point to a potential boiling horizon located deeper or marginal to the currently exploited levels of the Co–O mine. The absence of K-feldspar may also be related to relatively low temperatures of the hydrothermal fluid, the medium potassium-rich magma series of the host rocks, and/or a relatively low oxidation state of the hydrothermal fluid. 相似文献