Genesis of REE minerals in the karstic bauxite in western Guangxi,China, and its constraints on the deposit formation conditions

Karstic bauxites in western Guangxi, China, comprise two subtypes: Permian bauxite and Quaternary bauxite. The Quaternary bauxite originated from the breaking up, rolling, and accumulating of Permian bauxite in karstic depressions in Quaternary. Various types of rare earth element (REE) minerals were discovered during the formation of the Permian and Quaternary bauxites from the Xinxu, Longhe, and Tianyang bauxite deposits in this study. Five types of REE minerals, including bastnäsite, parisite, cerianite, rhabdophane, and churchite, were identified. Bastnäsite and parisite are the most abundant, and they are widely developed in the Permian ore and also present in the Quaternary ore. Obvious variations in bastnäsite and parisite REE compositions were observed, which is ascribed to distinctions in the source materials in the primary weathering profile from different areas. The mode of occurrence of bastnäsite and parisite suggests they were mainly precipitated under alkaline and reducing conditions during the Permian bauxite-forming stage and underwent intensive corrosion in the Quaternary. Churchite was formed during the Permian weathering stage under acidic condition. Both cerianite and rhabdophane occur in fractures within the Permian bauxite ore, indicating that both formed during the Quaternary weathering stage. It is considered that the rhabdophane enriched in Ce have formed locally, in the process of that the Ce^3 +, released from bastnäsite rapidly, entered the rhabdophane lattice before being oxidized to Ce^4 +. Cerianite was mainly found in association with Mn–Al hydroxides, suggesting that the released Ce^3 + was oxidized into Ce^4 + and precipitated cerianite in fractures within the Permian bauxite ore. Mass balance equations reveal a depletion in nearly all REEs during the transformation from the Permian to the Quaternary bauxite ore, mainly caused by the dissolution of bastnäsite and parisite. The genesis of the REE minerals, together with the occurrence of other minerals, indicates that intensively acidic and oxidizing conditions developed before the formation of the Permian bauxite ore. Towards the end of the Permian, the conditions became reducing and alkaline, favorable for the large-scale bauxitization. The Quaternary bauxite-forming stage was characterized by variable pH and Eh conditions, with acidic (pH = 4–6) and oxidizing (Eh > 2) conditions at the surface of the exposed Permian bauxite ore.     

华北南缘石炭纪仁村大型喀斯特型铝土矿物质来源与成矿过程研究

华北克拉通在中奥陶世至晚石炭世经历了强烈的风化和喀斯特化作用, 并在晚石炭世形成大规模喀斯特型铝土矿, 但是其物质来源及成矿过程目前仍存争议。本文选取华北南缘仁村大型喀斯特型铝土矿床, 在矿床地质剖析基础上, 对两个钻孔岩心进行矿物学、地球化学、碳-氧同位素分析, 剖析了成矿物质来源和成矿环境条件, 总结了铝土矿形成过程。仁村铝土矿含矿岩系赋存于奥陶系灰岩风化面之上的石炭系本溪组中, 含矿岩系自下而上包括铁质粘土岩、铝土矿和粘土岩。X衍射和扫描电镜-能谱分析显示铁质粘土岩主要矿物为菱铁矿和伊利石, 铝土矿主要矿物为硬水铝石、黄铁矿、菱铁矿、锐钛矿、伊利石和高岭石, 而粘土岩主要矿物为高岭石和勃姆石。铁质粘土岩元素组成以SiO₂、FeO、Al₂O₃为主, 铝土矿以Al₂O₃、SiO₂、FeO、TiO₂为主, 而粘土岩主要为SiO₂。微量元素Zr、Hf、Nb、Ta、Th和U等在含矿岩系呈现整体富集, 稀土元素主要在铝土矿层底部富集。硬水铝石-黄铁矿-菱铁矿矿物集合体、铝土矿层中Ce异常、La/Y和(La/Yb)_N比值以及菱铁矿C-O同位素组成(δ¹³C: -11.35‰~-7.63‰; δ¹⁸O: -9.26‰~-5.93‰)揭示铝土矿主要形成于地表碱性-还原的喀斯特洼地环境, 微生物广泛参与成矿过程。微量-稀土元素组成及稳定元素比率显示含矿岩系成矿物源存在明显垂向变化。其中, 底部铁质粘土岩主体为底板碳酸盐岩原地风化形成, 而顶部铝土矿和粘土岩为异地来源。综合前人研究成果, 提出了华北南缘石炭系本溪组铝粘土矿三阶段形成过程: 早期风化阶段(450~320Ma)形成铁质粘土岩或铁质风化壳; 物源输送阶段(320~310Ma)堆积大规模成矿物质; 成矿及后生改造阶段(< 310Ma)形成大规模铝粘土矿。

     

豫西南许窑沟金矿成因

对许窑沟金矿产出的地质背景，矿床特征，控矿因素及矿床成因等几方面作了系统的论述，提出了断裂，特别是韧性剪切带对成矿的主要控制作用；花岗岩与成矿有较大的时差，具有穿时，穿层的特点，它起着沟通深部与浅部的作用，并使深部的含Au流体沿断裂破碎带上升，沉淀而成矿。     

滇西昌宁-孟连缝合带铜厂街矿床成因探讨

铜厂街矿床位于昌宁-孟连缝合带北端,是一个以铜为主的小型矿床。含矿岩系为下石炭统平掌组下段一套变质拉斑玄武岩系列的海相火山岩组合。矿体呈层状、似层状产出,与围岩界线清晰。网脉状矿化发育于块状矿体之下。矿区含矿玄武岩主量、微量元素分析结果显示其具有N-MORB型洋脊玄武岩的特征;电子探针分析结果显示,黄铁矿主要落入岩浆热液型黄铁矿区;磁铁矿主要落入岩浆岩磁铁矿向沉积变质磁铁矿过渡区,且不同晶型、粒度的磁铁矿及其中心和边部在成因上都呈现出一定的差异和规律性。矿区石英和方解石中气液包裹体分析结果表明,均一温度范围131~362℃,盐度w(NaCleq)为2.07%~9.34%。结合矿区成矿地质特征,认为铜厂街矿床为与海底火山活动有关的VMS矿床,后经历了喜马拉雅期的变质改造。     

华北石炭纪艾雨头大型喀斯特铝土矿成因机制研究

喀斯特型铝土矿中硬水铝石的成因机制对准确认识该矿床的成因至关重要, 也是业界长期争论的焦点。早期普遍认为风化作用阶段形成的三水铝石经历后期压实变质作用脱水形成硬水铝石, 然而近期大量研究显示自然界铝土矿中硬水铝石多为地表喀斯特型环境下结晶形成。华北晚石炭世发育大规模硬水铝石型喀斯特铝土矿, 本文选取华北北部艾雨头大型铝土矿床为研究对象, 在翔实的矿床地质研究基础上, 借助X射线粉末衍射(XRD)、扫描电镜-能谱分析(SEM-EDS)及激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)技术, 探索硬水铝石的地表结晶条件和铝土矿的形成过程。艾雨头铝土矿含矿岩系剖面自下而上依次包括铁质粘土岩、铝土矿和粘土岩, 其中: 铁质粘土岩矿物组成主要为伊利石、高岭石、针铁矿、赤铁矿、硬水铝石和锐钛矿; 铝土矿主要为硬水铝石、高岭石、赤铁矿、针铁矿和锐钛矿; 粘土岩为高岭石、针铁矿、赤铁矿和锐钛矿。艾雨头喀斯特铝土矿顶底板岩石未发生变质作用, 而且原位分析显示硬水铝石中含有较高含量的Si、Fe、Ti、Cr、V、Pb等元素, 指示硬水铝石为表生沉淀成因。矿石中发现硬水铝石与赤铁矿和针铁矿密切共生, 表明硬水铝石可在氧化条件下形成(Eh>0.2)。硬水铝石中氧化还原敏感元素间良好的线性关系(包括V/Mn-Cr/Mn、V/Fe-Cr/Fe、V/Fe-U/Fe和U-Cr)以及V、Cr、U元素的共同富集, 指示硬水铝石沉淀时氧化还原阈值为T₁-T₃(即低氧-还原环境(-0.4 < Eh < 0.4))。硬水铝石中较高含量的Fe元素以及与硬水铝石共生的赤铁矿和针铁矿中较高含量的Al元素反映成矿前期已形成了大量的铁铝固溶体(Al_xFe_1-x(OH_y)^3-y)。这些不稳定的铁铝固溶体在成岩阶段转变为含铁硬水铝石(Fe-AlOOH)和含铝针铁矿、赤铁矿(Al-FeOOH、Al-Fe₂O₃); 含铁硬水铝石在后期压实成岩过程中进一步转变为硬水铝石。该研究结果解释了艾雨头铝土矿中硬水铝石地表大规模结晶的基本条件和过程, 对全面认识华北喀斯特铝土矿具有重要意义。

     

微重力法与可控源音频大地电磁法组合在豫西寻找隐伏铝土矿中的应用

通过方法试验,在豫西地区已知铝土矿区的外围开展了1：5万高精度重力测量,发现绝大多数矿床点位于较平缓的重力梯度带上。：基底相对稳定的地段可作为铝土矿的找矿靶区;采用CSAMT（可按源音频大地电磁）法测深剖面,卡尼亚电阻率一频率曲线拐点可直接反映出新生界覆盖层和奥陶系灰岩层的埋藏深度,进而推断石炭系本溪组（铝土矿）的埋深。经10余个钻孔验证,见矿率达80％以上。试验结果证明,在地质研究的基础上,微重力法加上CSAMT法测深是寻找隐伏铝土矿的有效的方法组合。     

Importance of hydrogeological conditions during formation of the karstic bauxite deposits,Central Guizhou Province,Southwest China: A case study at Lindai deposit

Karstic bauxite deposits are widespread in Central Guizhou Province, SW China, and high-grade ores are frequently sandwiched with overlying coal and underlying iron-rich layers and form a special “coal–bauxite–iron” structure. The Lindai deposit, which is one of the most representative karstic bauxite deposits in Central Guizhou Province, was selected as a case study. Based on textural features and iron abundances, bauxite ores in the Lindai deposit are divided into three types of ores, i.e., clastic, compact, and high-iron. The bauxite ores primarily comprise diaspore, boehmite, kaolinite, illite, and hematite with minor quartz, smectite, pyrite, zircon, rutile, anatase, and feldspar. The Al₂O₃ (53–76.8 wt.%) is the main chemical contents of the bauxite ore samples in the Lindai district, followed by SiO₂, Fe₂O₃, TiO₂, CaO, MgO, S, and P etc. Our geological data on the Lindai deposit indicated that the ore-bearing rock series and its underlying stratum have similar rare earth elements distribution pattern and similar Y/Ho, Zr/Hf, and Eu/Eu¹ values; additionally, all ore-bearing rock samples are rich in MgO (range from 0.16 wt.% to 0.68 wt.%), and the plots of the dolomites and laterites lie almost on or close to the weathering line fit by the Al-bearing rocks in Zr vs. Hf and Nb vs. Ta diagrams; suggesting that the underlying Middle Cambrian Shilengshui Formation dolomite is the parent rock of bauxite resources in the Lindai district.Simulated weathering experiments on the modern laterite from the Shilengshui Formation dolomite in the Lindai bauxite deposit show that hydrogeological conditions are important for karstic bauxite formation: Si is most likely to migrate, its migration rate is several magnitudes higher than those of Al and Fe under natural conditions; the reducing inorganic acid condition is the most conducive to Al enrichment and Si removal; Fe does not migrate easily in groundwater, Al enrichment and Fe removal can occur only in acidic and reducing conditions with the presence of organic matter.The geological and experimental studies show that “coal–bauxite–iron” structure in Lindai deposit is formed under certain hydrogeological conditions, i.e., since lateritic bauxite or Al-rich laterite deposited upon the semi-closed karst depressions, Si can be continuously removed out under neutral/acidic groundwater conditions; the coal/carbonaceous rock overlying the bauxitic materials were easily oxidized to produce acidic (H₂S, H₂SO₄, etc.) and reductant groundwater with organic materials that percolated downward, resulting in enrichment of Al in underlying bauxite; it also reduced Fe³⁺ to its easily migrating form Fe²⁺, moving downward to near the basal carbonate culminated in precipitating of ferruginous (FeS₂, FeCO₃, etc.) strata of the “coal–bauxite–iron” structure. Thus, the bauxitic materials experienced Al enrichment and Si and Fe removal under above certain hydrogeological conditions forming the high-quality bauxite.     

豫西铝土矿成矿时代初探

从两个方面论证豫西铝土矿的成矿时代应为晚石炭世的观点 :1、岩石地层学方法 ,说明铝土矿层与其直接盖层处于同一海浸沉积系列中。2、古生物学方法 ,通过经鉴定的 38种种、属的化石 ,证明铝土矿的成矿时代应为晚石炭世     

桂西二叠系铝土矿地球化学特征与沉积模式

桂西二叠系铝土矿具有"二元"成层构造,下层为厚层状铝土矿层,主要矿石类型为块状铝土矿、豆鲕状和碎屑状,上层为层韵状铝土矿层,主要矿石类型为致密状,次之为碎屑状,上下层之间局部地段可见冲刷面。下部厚层状铝土矿层常量组分Al_2O_3、Fe_2O_3、TiO_2明显高于上部层韵状铝土矿层,SiO_2高出4倍,活泼组分Ca O+MgO+K_2O+Na_2O的含量高出10倍,微量元素中Ba、Rb、Sr、Li表现为上层高下层低,不活泼元素Sc、Cr、Ga、Nb、Hf、Ta、V、Zr、∑REE显示上层低下层高特点。铝土矿层属于峨眉山热地幔柱事件引起的东吴运动过程中两个小的"事件—过程"亚阶段(幕)产物,厚层状铝土矿分层形成于"岩浆—夷平"均衡亚阶段,作为物源的古风化壳成熟度高,层韵状铝土矿分层形成于"岩浆—夷平"失衡亚阶段,而相应的古风化壳成熟度低,从而导致成层构造迥异和地球化学突变。     

河南省三门峡地区铝土矿矿床地质特征及找矿方向

河南省三门峡地区的铝土矿是赋存于中石炭统本溪组中的一水硬铝石型铝土矿。以往的地质勘查找到了一些小、中、大型铝土矿矿床。对该地区铝土矿矿床地质特征及成矿规律进行了翔实研究,结果认为,在现有部分勘查区的深部和边部仍有较大的找矿潜力,若加大勘查投入,本区铝土矿的勘查工作将会达到一个新水平。     

Mineralogy,geochemistry, and ore formation of Nuwaifa bauxite deposit,western desert of Iraq

Nuwaifa Formation is a part of sequence stratigraphy that belongs to the Jurassic system exposed in the western desert of Iraq. The Jurassic system consists of Ubaid, Hussainiyat, Amij, Muhaiwir, and Najmah formations. Each formation is composed of basal clastic unit overlain by upper carbonate unit. Nuwaifa karst bauxite was developed in fossil karsts within the Ubaid Formation in areas where maximum intersection of fractures and faults exist. This bauxitization process affected the upper surface of the Ubaid limestone formation, which directly underlies the Nuwaifa bauxite Formation. Nuwaifa Formation represents karst-filling deposit that consists of a mixture of allochthonous (sandstone, claystone, and mudstone) and autochthonous lithofacies (bauxite kaolinite, kaolinitic bauxite, iron-rich bauxite, and flint clay). Most bauxite bodies occur within the autochthonous lithofacies and are lenticular in shape with maximum thickness ranges from few meters to 35 m and in some place up to 100 m. Petrographically, the bauxite deposit exhibits collomorphic-fluidal, pisolitic, oolitic, nodular, brecciated, and skeletal textures indicative of authigenic origin. Mineralogy boehmite and gibbsite are the only bauxite minerals; the former is dominant in the upper parts of the bauxite profiles, whereas the latter is dominant throughout the lower and middle part of the bauxite. Kaolinite, hematite, goethite, calcite, and anatase occur to a lesser extent. The study bauxites are mainly composed of Al₂O₃ (33–69.6 wt.%), SiO₂ (8.4–42 wt.%), Fe₂O₃ (0.5–15.9 wt.%), and TiO₂ (0.7–6.1 wt.%) with LOI ranging from 13.5 to 19.1 wt.%. Geochemical investigations indicate that the immobile elements like Al₂O₃, TiO₂, Cr, Zr, and Ni were obviously enriched, while SiO₂, Fe₂O₃, CaO, MgO, Zn, Co, Ba, Mn, Cu, and Sr were depleted during bauxitization process. The results of this study strongly suggest that the bauxite deposits of the Nuwaifa Formation are derived from the kaolinite of the Lower Hussainiyat Formation.     

豫西黄沟金矿床地质地球化学特征

通过研究黄沟金矿床中岩石地球化学特征,从而探讨太华群地层对于该区金矿床成矿的作用。研究表明(1)本区的片麻岩原岩主要为火成岩,属高钾钙碱性系列,且金矿石一般都明显贫钠而富钾、富钙,SiO2含量普遍较高,Au品位随SiO2的含量增高而呈正相关变化;(2)微量元素特征表明矿石样品以Rb、Ta、Ti等元素强烈亏损,Ba、Sm和Y元素强烈亏损为特征,与太华群片麻岩和熊耳群安山岩的标准化分布曲线型式接近,说明金矿化可能与太华群片麻岩和(或)熊耳群安山岩具有成因上的联系;(3)稀土元素特征表明多数金矿石的轻稀土略亏损、重稀土略富集,弱负铕异常与矿区出露的各类岩石的稀土元素标准化分布曲线(右倾型)不同,而具深源特性;个别金矿石的标准化曲线形态一定程度上具片麻岩或(和)安山岩的特征,呈弱负铕异常的右倾形态,暗示了太华群片麻岩和(或)熊耳群安山岩也贡献了部分成矿物质。     

Genesis of the Sanbaqi deposit: a paleokarst-hosted uranium deposit in China

The Sanbaqi uranium deposit in Hunan Province, south China, is the largest of a group of paleokarst-hosted uranium deposits in Lower Carboniferous limestone. Mineralization is localized in cavities and fault-breccias formed by dissolution of carbonates. Four episodes of karst formation are recognized: late Triassic-early Jurassic, late Jurassic-early Cretaceous, Cretaceous-Tertiary and Recent. Field relations indicate that the main uranium mineralization is related to the second karst episode. This is supported by isotopic ages of two pitchblende samples at 129 Ma and 134 Ma, as indicated by their nearly concordant data points on concordia plot. These ages are in the time range of the early Yanshanian tectonic movements that affected southern China, and the faulting related to the movements likely triggered the mineralization process at the Sanbaqi deposit. Associated minerals include pyrite, millerite, ullmannite, niccolite, molybdenite, chalcopyrite, sphalerite, galena, calcite and dolomite. Fluid inclusion studies on calcite reveal that temperature of ore deposition was from 181° to 150 °C. The δ¹⁸O and δD values of the ore fluids range from 1.5 to 7.9 per mil and from −30.4 and −54.8 per mil, respectively. The mineralogical, fluid inclusion and isotopic data indicate that the minerlization took place in episodic pulses of hydrothermal fluids that were introduced along a set of ring faults. Mobilization and redeposition of earlier formed ore minerals in an open system added to the complexity of the paragenetic sequence. Younger episodes of mineralization occurred during the later karst events as suggested by the geological and additional pitchblende U-Pb isotopic data, during the Cretaceous-Tertiary late Yanshanian tectonic movements and recently. Finally, a comparison of the Sanbaqi uranium deposit with the uranium deposits hosted by solution collapse breccia pipes of the Colorado Plateau, USA, shows that they have many similarities. Received: 9 July 1996 / Accepted: 17 January 1997     

晋豫铝土矿矿床地质特征及资源远景

山西省和豫西地区铝土矿资源量占全国总资源量的一半以上,矿床类型为古风化壳沉积型铝土矿,近年地质调查又发现了堆积型.本文结合以往勘查研究和地质调查成果,通过对该区铝土矿的时空分布、典型矿床研究及矿床沉积环境及成因分析,圈定了找矿靶区,认为该地区铝土矿具有巨大的找矿潜力.     

河南省偃龙铝土矿床地球化学特征及成矿物质来源分析

本文以偃龙铝土矿为对象,研究了铝土矿的地球化学特征,讨论了其成矿物质来源。铝土矿含矿岩系中不同矿产的SiO_2、Al_2O_3、Fe_2O_3、FeO的元素含量变化较大,且总量较高,说明铝土矿在形成过程中,其源岩风化程度较高。Al_2O_3与SiO_2、Fe_2O_3、K_2O含量呈负相关关系,与TiO_2、A/S呈正相关关系。含矿岩系明显具有富集轻稀土、亏损HREE的特征,在垂向上,其稀土元素含量较高的是Ce、La、Nd(均为轻稀土),低含量的是Tm、Ho、Eu、Lu。微量元素方面,偃龙铝土矿比山西铝土矿富集的元素有Li、Be、Sc、Ni、Cu、Zn、Zr等稀有金属元素和亲铜元素,而这些元素在贵州大竹园铝土矿中的含量比偃龙铝土矿更富集。偃龙铝土矿的成矿物质来源于基底碳酸盐岩风化残余,在广泛海侵时,残余物质经搬运沉积成矿。     

黔东南铁厂沟铝土矿含矿岩系地球化学研究

贵州黔东南铁厂沟铝土矿目前已探明矿石量约298万吨,属大型矿床,其含矿岩系为二叠系下统梁山组,矿体常呈似层状、透镜状、漏斗状覆于上泥盆统高坡场组白云岩古侵蚀面上,矿体底部通常含菱铁矿结核.矿体顶板通常为碳质页岩或煤带,部分地区的顶板为二叠系栖霞组灰岩,由此组成了凯里—黄平地区典型的煤-铝-铁结构.对铁厂沟铝土矿成铝盆地中心的1个钻孔中的高岭岩系样品进行元素地球化学特征分析,解剖该成铝盆地中心的沉积风化成岩过程,主要结论包括:1)稳定元素特征如Zr-Ta、Zr-Nb、Cr-Ni图解及Al2O3/TiO2比值等综合表明基底的志留系地层是铁厂沟矿床主要的物源;2)二叠系该区域的第1次抬升剥蚀,致使盆地周缘出露并发生剥蚀去顶作用,风化产物向盆地中心运移,初次沉积以高岭石为主、富集锐钛矿、锆石等副矿物的原始高岭岩系,与志留系页岩相比较,具有低K、Mn、Cs、Rb、Sr、Ba,高Al、Sr、Th、Nb、Zr、Y和REE等特征,δCe异常总体为弱负异常,表明其沉积环境总体以弱还原环境为主;3)第2次抬升作用使得盆地中心剖面也发生了一定程度的风化淋滤改造,但剖面整体Al/Si比值变化较小,表明仅发生了一定的去铁淋滤,上部高岭岩中V/Cr(平均1.96)、Th/U(平均3.40)和Co/Ni(平均0.39)均体现出弱氧化的风化特征,风化淋滤导致上层高岭岩系轻稀土元素的迁移及总稀土元素含量下降,并最终改变了上、下层高岭岩的稀土配分模式,下层高岭岩系以富含菱铁矿结核为特征,风化过程中从上部及盆地周缘成铝部位淋滤的铁在剖面下部富集,推测原始形态为铁结核,在后期成岩过程中与周围的有机碳反应形成菱铁矿结核.     

河南省嵩县万村金矿矿床成因及找矿远景

万村金矿床产于华北陆块南缘熊耳山金矿化集中区,花山花岗岩体的南部边缘。通过综合分析、研究矿区探(矿)采(矿)及前人资料,本区金矿具有造山带型金矿的特征。金矿形成于岩体侵入之后,矿体在构造形成过程中由含矿热液充填形成,太华群仍是本区金矿的主要矿源层,花山花岗岩体在成矿过程中提供了重要的成矿物质。矿体主要分布在含矿蚀变带中下部和底部,根据区内化探资料分析,矿体中深部存在第二矿化富集段,显示该区中深部具有较大的找矿潜力。     

Geochemistry of the Yutangba Se Deposit in Western Hubei, China

1IntroductionThecontentsofSeinthecrustareextremelylow ,onlyabout0 .0 5mg/kg .Innatureitishardtoformindependentminerals,insteaditisdispersedinothermineralsandmedia.Althoughitscon tentsarefarhigherthanthoseofTeinthecrust,seleniumisusuallydispersedinsulfidesinitsas cendingandformingprocesses (D’yachkovaandKhodakovskiy ,1 968) .Thisisthereasonwhyse leniummineralsarefarlessthantelluriummineralsandsulfidesinnature (Simonetal.,1 997) .Forthisreason ,thegeochemicalstudyofseleniumdidnotattractanyat…     

Genesis of the Jincheng Gold Deposit in Luoshan County, Henan Province, China

<正>1 Introduction The Tongbai-Dabie area has experienced multistage plate subduction-collision activities,resulting in the development of a series of nearly EW-trending ductileshear zones with different levels,scales,and characteristics(Wu et al.,2012).These ductile shear zones have controlled the northern Tongbai-Dabie     

豫西前河金矿热液蚀变地球化学研究

含矿热液在迁移过程中与围岩发生了广泛的流体-岩石反应而引起热液蚀变.前河金矿区内主要的热液蚀变有钾长石化、青磐岩化、绢云母化、硅化、黄铁矿化、碳酸盐化和萤石化等7种类型;划分了6个蚀变-成矿阶段,即黑云母-钾长石阶段→青磐岩阶段→绢英岩阶段→黄铁矿-石英阶段→石英-黄铁矿阶段→碳酸盐-卤化物阶段,以及外、中、内3个蚀变带.5种典型蚀变岩的常量和微量元素分析表明,绢英岩化蚀变中,Si、K大量迁入,Pb含量大大增加,在∑REE有所降低的情况下HREE有所富集:δ Eu和δ Ce在各蚀变阶段均呈现负异常:这些现象可能是导致金沉淀的元素地球化学响应.各阶段成矿流体-岩石的交代特点在绿泥石单矿物的矿物化学成分变化上也有所反映.