Geological and geochemical features of the Erdenetiin-Ovoo deposit

For the first time the opportunities provided by the GIS and three-dimensional modeling techniques were applied for analysis of the distribution of principal and accompanying constituents, harmful impurities, mineral and metasomatic ore types within the ore-bearing Erdenetiin-Ovoo stockwork. Analysis of the obtained materials allowed identification of the zoning of the distribution of useful and accompanying constituents for the first time.     

西藏多龙矿集区荣那铜金矿床蚀变矿物学和地球化学及找矿意义

位于西藏多龙矿集区的荣那铜金矿床是班公湖-怒江成矿带首例斑岩型-浅成低温热液型矿床,它的发现对于班公湖-怒江成矿带找矿模型的构建以及资源潜力评估有着重要意义。本文以荣那矿床ZK3204岩芯钻孔为研究对象,针对其蚀变矿物,运用短波红外光谱测试技术,并结合金属矿物组合以及黄铁矿LA-ICP-MS原位微量元素特征,以期查明其矿床成因,并为深部资源勘查提供理论依据。短波红外光谱测试显示出ZK3204钻孔蚀变矿物垂向分带组合为:高岭石+(地开石)→高岭石+伊利石→高岭石+(地开石+石膏)→高岭石+绢云母+伊利石→高岭石+伊利石+(叶腊石)+(地开石),金属矿物也从Cu-S体系逐渐转变为Cu-Fe-S体系。通过黄铁矿LA-ICP-MS原位微量元素分析发现,黄铁矿可分为四类,分别对应荣那矿床四个成矿阶段:(1) Py I:Co、Ni、Cu、Ag、Au含量较低,Co/Ni显示为沉积成因,代表成岩期黄铁矿;(2) PyⅡ:Co、Ni含量较低,Cu、Ag、Au含量较高,Co/Ni显示为沉积成因,代表第一期斑岩型矿床成矿期黄铁矿;(3) PyⅢ:Co含量较低,Ni、Cu、Ag、Au含量较高,Co/Ni显示为沉积成因,代表第二期斑岩型矿床成矿期黄铁矿;(4) PyⅣ:Cu、Ag、Au含量较低,Co、Ni含量较高,Co/Ni显示为热液成因,代表浅成低温热液矿床成矿期黄铁矿。风化作用也是荣那矿床重要地质过程,贯穿于各成矿阶段,反映为早白垩世班公湖-怒江洋盆向北俯冲消减大背景下的多龙矿集区隆升事件,导致矿床被大量剥蚀,也使黄铁矿显示沉积成因。荣那矿床目前仍有较大找矿潜力,在钻孔深部(815m以下),黄铁矿Cu、Ag、Au含量,钻孔中Cu、Pb、Zn、Cr、Hg等含量,绢云母、伊利石含量以及铜金矿的矿石品位均有向下升高的趋势,说明在ZK3204钻孔下部仍有巨大的找矿潜力,可作为未来深部资源探测的重点对象。     

Geological and geochemical features of the auriferous Butarny deposit

The Butarny deposit is characterized by the development of mineralization of gold-quartz and gold-rare metal mineral associations related to Late Cretaceous granitoid magmatism and metasomatism imposed during the Late Jurassic tectonomagmatic epoch. Ores on the Butarnoe site were formed during the vein quartz-sulphide stage and partially oxidized in a zone of hypergenesis. The gold found there is fine-grained and is also related to arsenopyrite and scorodite and, to a lower degree, to quartz and iron hydroxide     

Metallogenic specialization hypothesis and some of its mineralogical and geochemical aspects

Metallogenic specialization is part of a worldwide differentiation of terrestrial substance. This process is closely connected with magmatic processes. Four types of magmatic specialization are outlined. They are characterized by the regional features of mineralization, evolution of mineral composition of ore, selective dispersion or concentration of ore-forming elements during the crystallization of rocks, and the mobilization of ore-forming substance by the postmagmatic solutions. — E. A. Alexandrov.     

Geological,geochemical and mineralogical characteristics of REE-bearing Las Mercedes bauxite deposit,Dominican Republic

Bauxite deposits, traditionally the main source of aluminum, have been recently targeted for their remarkable contents in rare earth elements (REE). With ∑REE (lanthanoids + Sc + Y) concentrations systematically higher than ∼1400 ppm (av. = 1530 ppm), the Las Mercedes karstic bauxites in the Dominican Republic rank as one of the REE-richest deposits of its style.The bauxitic ore in the Las Mercedes deposit is mostly unlithified and has a homogeneous-massive lithostructure, with only local cross-stratification and graded bedding. The dominant arenaceous and round-grained texture is composed of bauxite particles and subordinate ooids, pisoids and carbonate clasts. Mineralogically, the bauxite ore is composed mostly of gibbsite and lesser amounts of kaolinite, hematite, boehmite, anatase, goethite, chromian spinel and zircon. Identified REE-minerals include cerianite and monazite-Ce, whose composition accounts for the steady enrichment in light- relative to medium- and heavy-REE of the studied bauxites.Considering the paleo-geomorphology of the study area, we propose that bauxites in the Las Mercedes deposit are the product of the erosion and deposition of lithified bauxites located at higher elevations in the Bahoruco ranges. Based on the available data, we suggest a mixed lithological source for the bauxite deposits at the district scale: bedrock carbonates and an igneous source of likely mafic composition.     

山西堡子湾金矿床地质地球化学特征

山西堡子湾金矿床位于华北地台北缘，是以金为主伴生银铜多金属的中型金矿床。赋存地层为太古界集宁群。燕山期岩浆活动形成的石英二长岩及有关的隐爆角砾岩与成矿关系密切。围岩蚀变分布于角砾岩体内，主要为绢云母化、高岭石化、碳酸盐化和硅化。石英二长岩的稀土分布型式和岩石地球化学特征，说明其为重熔型岩浆侵入所形成。矿体中石英的氧同位素δ^18O值接近花岗岩类范围；矿床中硫化物的δ^34S值范围为-3．2‰～-1．2‰，接近陨石硫。堡子湾金矿的成矿物质来源于岩浆，成矿作用与燕山期岩浆期后热液活动以及隐爆作用和流体作用有关。     

Ferreto soils at the southeastern margin of the Bohemian Massif — A mineralogical and geochemical characterization and its application in stratigraphy

Ferreto soils occurring on different levels of sand and gravel sediments in southern Moravia, s.S.R., have been studied by field observations, stratigraphic, mineralogic and chemical analyses. Three groups of paleosoils have been distinguished according to their geological age. It has been found that the intensity of weathering decreases from the Lower Miocene (the oldest and thus the uppermost terrace) to the Quaternary (the youngest and bottom terrace).     

Primary geochemical and mineralogical dispersion in the vicinity of the Lady Loretta Zn-Pb-Ag deposit, Northwest Queensland

Lady Loretta is a stratiform Zn-Pb-Ag deposit occurring within carbonate- and pyrite-rich argillaceous rocks of the southern part of the Lawn Hill Platform, northwestern Queensland. The deposit consists of a single massive sulphide lens within a steep-sided basinal structure and contains reserves of 8 690 000 tonnes of ore at 18.1% Zn, 6.7% Pb and 110 g t⁻¹ Ag.The proportion of pyrite-rich layers in the host rocks increases progressively from about 2% at 150 m stratigraphically below the ore to > 90% in the top 10 m of the footwall rocks. Hanging-wall rocks contain up to 20% pyrite-rich layers for at least 100 m above the ores. Siderite is the carbonate phase present within the ore and within the host rocks in an aureole that extends from 75 m beneath to 50 m above the ore. Both older and younger rocks are dolomitic. The two carbonate phases do not occur together within unmineralized host rocks although they may coexist within veins. Siderite contains up to 13 mol% ZnCO₃ and 32 mol% MgCO₃. There is an antipathetic relationship between Zn and Mg, the latter increasing with distance from the ore.Zinc and, to a lesser extent, Hg, Pb, Ag and Ba show extensive primary dispersion within the host rocks. Within the plane of sedimentation, haloes vary in width from 50 m to 1.5 km and these dispersions are thought to be dependent on the shape of the sedimentary basin floor at the time of exhalative activity. Perpendicular to the sedimentary layering, Zn and Hg show the most extensive primary dispersion with anomalous values extending up to 100 m into the footwall and at least 50 m into the hanging wall.     

约硫砷铅矿在中国的首次发现及其矿物学特征

约硫砷铅矿是一种较为罕见的硫盐矿物,本文在广西壮族自治区武宣县盘龙铅锌矿区首次发现约硫砷铅矿,主要呈不规则粒状分布于黄铁矿中,与黄铁矿、方铅矿、闪锌矿和重晶石相伴生。在反光显微镜下,约硫砷铅矿双反射明显,白光下的反射率为R_1=38.6%,R_2=41.8%,反射色为白色略带蓝色色调,具微弱的反射多色性,强非均质性。利用电子探针确定其经验化学式为Pb_(14.05)(As_(2.66),Sb_(3.23))_(5.89)S_(22.99)。采用X射线衍射技术获得了约硫砷铅矿的晶胞参数:a=8.91(2),b=31.96(6),c=8.47(2),β=117.77°,V=2 135.49~3,空间群为P2_1/m,Z=2。通过XRD、EPMA等现代岩矿测试分析技术,结合前人对盘龙铅锌矿成矿时代研究的相关资料,还对约硫砷铅矿的成因进行了初步探讨。     

安徽休宁桃溪铅锌矿地质、物化探特征及其找矿潜力

桃溪地区位于安徽省休宁县—歙县金多金属矿整装勘查区中部,具有良好的金多金属矿成矿地质条件。通过专项地质填图发现,桃溪铅锌矿受近EW走向多期活动叠加的断裂控制,其中第3期高角度张性正断层与成矿作用关系密切;矿化体多为脉状,含矿热液于密集裂隙带充填而成。土壤化探圈定有AP18综合异常,呈长轴近EW走向的长条椭圆状,受上述断裂控制,该异常面积2.6 km^2,由Au、Ag、Cu、Pb、Zn多元素套合。高精度磁法测量圈定有M2和M3异常,与化探异常相吻合;激电中梯和激电测深测量结果进一步反映了异常的真实性,并剖析了极化体的深部特征。通过桃溪地区地质及物化探特征的综合分析,认为该地区具有多金属矿勘查的潜力。     

大石桥菱镁矿矿床矿石地质地球化学特征

大石桥菱镁矿矿石的残余沉积构造及交代结构均很发育。菱镁矿交代白云岩、粗、中、细粒菱镁矿依序交代。副矿物分残余沉积变质矿物、热液矿物、残余热液矿物及次生矿物四类。菱镁矿为一组MgCO_(?)-FeCO_3固溶体,其铁含量依温度降低而增加,组分均勺性则依世代演化而降低。凡离子半径与镁近似的痕量元素随镁自围岩至矿石迁移,反之,则随钙分散。矿石中碳、氧同位素组成均不因流体冷却、分馏系数增大而变,可能有含适度轻氧的卤水不断注入,碳则因阳离子交换自白云岩继承而来。确定了矿物生成顺序表。     

宿松杂岩中白云母的矿物学特征及地质意义

大别山为印支期扬子陆块和华北陆块之间的碰撞造山带。太湖—宿松地区位于大别山东段部位,主要由扬子陆块北缘不同变质程度的变质基底和少量浅变质盖层组成。本文选择了宿松杂岩中的白云母进行探针分析以及X射线粉末衍射分析,研究结果表明宿松杂岩中的白云母都是2M₁型且均为多硅白云母。其中,多硅白云母的晶胞参数b₀平均值为9.039,显示宿松杂岩的变质压力为中压—高压。根据宿松杂岩中白云母的显微变形特征可以知道白云母至少存在着两期变形,一期是导致石榴子石压力影形成和白云母右旋的构造作用,应该对应着燕山期大别造山带中-下地壳物质发生平行造山带向东流动的地质事件。另一期是导致白云母形成涡流构造形成的构造作用,这一期构造应该对应扬子板块和华北板块碰撞事件。根据白云母中的Ti温度计和多硅白云母压力计可以得出宿松杂岩的变质条件为T=480 ℃～579 ℃,P=0.7～1.2 GPa,属于绿片岩相到角闪岩相。     

居隆庵铀矿床蚀变分带及其地球化学特征

以产于碎斑流纹岩中的铀矿化蚀变为例,对居隆庵铀矿床蚀变分带及其地球化学特征进行了系统研究,将该区蚀变分成5个带。地球化学研究表明,围岩蚀变过程中元素迁移、富集有明显的规律;常量元素（Ca、Mg、K、S）、微量元素（Cu、Pb、Zn、As、Sb、Th、Mo、W、F）和稀土元素（REE）有明显富集;亲硫元素是铀成矿作用的指示元素;成矿过程至少经历了两次热液活动;成矿流体具有还原性和深源性。     

贵州罗甸软玉矿的发现及岩石矿物学特征

贵州省境内近期发现了新玉石矿,玉石以白-浅绿色为主,偶见糖色、青色,多呈蜡状-弱油脂光泽。通过对采自该矿玉石样品的镜下观察,配合FTIR及XRD等大型仪器分析,确定其主要为透闪石矿物所组成的矿物集合体,与新疆和田玉基本一致。SEM观测结果揭示,该矿软玉中透闪石矿物主要呈纤维状、柱状和片状变晶结构,晶粒(片)粒度小,结构致密。其中具纤维状交织结构的软玉质地最为细腻,质量较好,与新疆和田玉相似度较高。     

Zircon LA-ICP-MS U-Pb age, Ce^4＋/Ce^3＋ ratios and the geochemical features of the Machangqing complex associated with copper deposit

1IntroductionQuite a number of porphyry copper deposits havebeen found in the Cenozoic alkali-intrusions along theJinshajiang-Ailaoshan-Red River fault zone,whichconstitute the Cenozoic ore belt in China.The Cenozo-ic alkali-intrusive rocks are similar in…     

东胜地区砂岩型铀矿床后生蚀变矿物分带特征初步研究

鄂尔多斯盆地北部东胜地区砂岩型铀矿主要产在侏罗系直罗组地层中。直罗组地层可分为上、下两段 :下段又分为上、下两个亚段 ,其中下亚段主要为容矿的灰色砂岩 ;上亚段主要为灰绿色砂岩、泥岩 ;上段为杂色的中细砂岩、泥岩。笔者通过对直罗组砂岩的镜下观察研究 ,在垂向上确立了岩石的后生蚀变分带 :直罗组下段下亚段为灰色 灰白色砂岩 (含矿段 )的绿化 (Ⅰ ) (主要为长石的绿帘石化 ) 碳酸盐化带 ;上亚段为灰绿色砂岩的绿化 (Ⅱ ) (主要为黑云母绿泥石化 ,也有长石绿泥石化和绿帘石化 ) 粘土化 碳酸盐化带 ;直罗组上段杂色细砂岩的褐铁矿化 粘土化 碳酸盐化带。主要的后生蚀变作用发生在灰绿色的砂岩中。砂岩呈现灰绿色的原因主要在于含较多绿色黑云母 ,而非绿泥石 ,其本质原因在于矿物中Fe2 含量较高。砂岩层中的后生蚀变现象与铀成矿作用关系密切。     

陕西穆家庄铜矿床后生成矿作用的流体地球化学证据

尽管秦岭泥盆系铅锌金多金属成矿带成矿作用均与热水喷流沉积作用有关,柞山地区却有别于凤太地区,具有独特的铜矿成矿背景。流体包裹体研究揭示了后生成矿流体的两阶段流体演化过程:第一阶段的成矿流体为中温,中高盐度岩浆热液含CO2的NaCl-H2O流体。均一温度为190～265℃,盐度12.5～35.34(wt%NaCl),压力12.8～21.3MPa,在同一寄主矿物中均一温度变化小,而盐度变化极大,是岩浆流体沸腾的产物;第二阶段成矿流体为中高温,中高盐度岩浆期后热液NaCl-H2O流体。均一温度为300～350℃,盐度7.4～41.59(wt%NaCl),压力10.8～19.3MPa。反映了岩浆期后热液流体的二次沸腾。应用流体地球化学的综合方法(包裹体流体组成、演化)识别出后生交代流体性质。穆家庄铜矿的成矿流体第一阶段为岩浆水,第二阶段的成矿流体为岩浆水加部分地层水(建造水)。氢氧同位素分析也支持上述结论。     

胶东大邓格金多金属矿床地质地球化学特征及意义

本文介绍了大邓格金多金属矿床地质特征,对矿床主量元素、硫同位素、氢-氧同位素及流体包裹体作了测试分析,总结了矿床地球化学特征,讨论了成矿物质来源及成矿物理化学条件。主量元素分析表明蚀变过程中Si O2、K2O含量增高,Na2O、Al2O3、Ca O等含量降低;硫同位素组成δ34SCDT值为7.0‰~7.1‰,指示硫可能来自于均一化程度较高的统一流体库;氢同位素组成δDV-SMOW变化范围较大,为-83.68‰~-116.95‰,氧同位素组成δ18O水值为-2.57‰~8.35‰,显示了成矿流体以岩浆水与大气降水组成的混合水为主;成矿流体主要为中温(86~429℃)、低盐度(1.74%~22.38%Na Cleq),属CO2-H2O-N2-Na Cl体系。成矿期流体表现出多期、多来源特征,体系物理化学条件的改变和流体的不混溶是导致金等成矿元素沉淀和富集的重要机制。     

Remobilization of arsenic from buried wastes at an industrial site: mineralogical and geochemical control

An industrial area contaminated by As was studied to determine the source of this element and its speciation in As-bearing solids and in run-off waters. Mineral precipitates and water samples were collected and analyzed to assess processes controlling As mobility at this site. The integrated study of a contaminated industrial area allowed identification of the source of the As and of the nature of secondary As-bearing phases. The results obtained both on solid and water samples were used to model As behavior during waste leaching on carbonate rocks. At the upper end of a topographic transect across the site, run-off waters (pH=7.9) interact with surficial waste piles (containing arsenolite, arsenopyrite and pyrite), becoming acidic (pH=2.2) and concentrated in dissolved arsenate species (As⁵⁺) (ΣAs ranging from 0.961 to 3.149·10⁻³ mol/l). Those acidic waters interact with the limestone substratum, providing dissolved Ca which reacts with As to precipitate 1:1 Ca arsenates (weilite CaHAsO₄, haidingerite CaHAsO₄.H₂O and pharmacolite CaHAsO₄.2H₂O) and, in minor amounts, Ca–Mg arsenates (picropharmacolite (Ca,Mg)₃(AsO₄)₂ 6H₂O). The 1:1 Ca arsenates identified are known to precipitate at low pH (3–6) and seem to be stable in media with high dissolved CO₂, in comparison with other types of Ca arsenates. However, due to their high solubilities, they are not strictly relevant candidates to immobilize As in contaminated surficial environments. Although reported solubilities decrease to values close to the French and US drinking standards in Ca-rich solutions, a thorough examination of the precipitation/dissolution kinetics of Ca arsenates should be undertaken to assess their long-term stability and their efficiency in rapidly immobilizing As in contaminated surficial environments.