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四川大水独立碲矿床中的楚碲铋矿 总被引：2，自引：0，他引：2
四川大水沟碲矿床是世界唯一的独立碲矿床，楚碲铋矿是该矿床中重要的碲矿物之一。它存在于辉碲铋矿和磁黄铁矿晶粒之间，或包裹在辉碲铋矿中，呈银灰色，金属光泽，一组底面解理发育。显微压入硬度８０．５ｋｇ／ｍｍ＾２。反光显微镜下为白色，非均质性清楚，反射率为５８．０－５９．０，Ｘ射线衍晶衍射分析的主要谱线有：４．７９７，３．２２９，２．３６８，２．１６９。矿物的化学组成据１１个电子探针分析的平均值为：Ｆｅ０ 相似文献
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四川大水沟碲矿床是世界唯一的独立碲矿床，楚碲铋矿是该矿床中重要的碲矿物之一。它存在于辉碲铋矿和磁黄铁矿晶粒之间，或包裹在辉碲铋矿中。呈银灰色，金属光泽，一组底面解理发育。显微压入硬度为80．5kg／mm2（15g负荷）。反光显微镜下为白色，非均质性清楚，反射率为58．0～59．9（λ=546nm）。X射线粉晶衍射分析的主要谱线有：4．797（60），3．229（100），2．368（80），2．169（50）。矿物的化学组成据11个电子探针分析的平均值为（重量％）；Fe0．13，S0．04，Cu0．03，Te37．84，Bi61．37，Se0．01，Sb0．16；总量99．58，其化学成分式为；BiTe。楚碲铋矿形成于贫硫环境中。 相似文献
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胶东乳山英格庄金矿碲化物的发现及其意义 总被引：8，自引：2，他引：6
本文通过电子探针微束分析,在胶东牟平-乳山成矿带内的英格庄金矿发现碲银矿、辉碲铋矿,并在胶东地区首次发现楚碲铋矿,该矿物系列以复杂的连生关系呈细小片状产出于白云石及石英矿物颗粒间。碲化物电子探针化学成分结果显示本区碲化物普遍贫碲。依据碲化物及其共生矿物的产出关系和矿物化学成分,推测其形成顺序为黄铁矿→镍黄铁矿→辉碲铋矿→楚碲铋矿→碲银矿。依据碲化物矿物共生组合对体系中碲化物形成时的fTe2和fS2进行了限定,log fTe2范围为-19.5~-11.2,log fS2上限为-16.8;并试图对碲的来源及其地质意义进行探讨,认为英格庄金矿中碲化物的发现揭示了深成幔源的信息,鉴于碲与金相近的地球化学特征和密切关系,认为金矿赋矿围岩荆山群和昆嵛山杂岩体提供成矿物质来源的可能性不大,而早白垩世的构造-岩浆活动特别是壳幔物质的交换过程与金成矿关系更为密切。 相似文献
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楚碲铋矿、赫磅铋矿是两种光见矿物，其化学成分特征是亏Bi而富S，An,Cu等杂质，它们呈细小的（0．05－0．15mm)的嵌晶被包裹在黄铁矿晶体中，在黄铁矿（单矿物）中含量最高可达2300ug/g，使其具有重要的综合利用价值。它们的生成是由于两种不同性质的初始热液在运移途中相偶，引起磅元素迅速淀积的结果，其化学成分特征反映出S，Au,Cu等都是该区可利用的重要有益组分，因此具找矿意义。 相似文献
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本文首次报道了四川石棉大水沟独立碲矿床中辉碲铋矿的反射率、显微硬度及热电性特征，与此同时，探讨了其化学成化和Ｘ射线粉晶衍射数据。大水沟独立碲矿床中的辉碲铋矿有粗晶和细晶两类，呈片状，具有较高的反射率和较低的硬度；其平均化学式为Ｂ１２Ｔｅ１．８９Ｓ，其Ｘ射线衍射资料与合成辉碲铋矿和硒碲铋矿类似而不同于世界其它地区的辉碲铋矿，其导电性为Ｎ型。 相似文献
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对小秦岭金矿田石英脉型金矿床中辉碲铋矿的产出特征，物理光学性质，化学成分进行了比较系统的研究，对矿物的显微硬度，反射率色散值以及化学成分进行了精确测定，提供了可靠的测试数据。 相似文献
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小秦岭金矿田中的两种罕见矿物—碲铅铋矿和自然碲 总被引：2，自引：0，他引：2
碲铅铋矿和自然碲产于河南省小秦岭含金石英脉矿床中。碲铅铋矿化学成分平均值(%)为:Te44.06,Bi40.24,Pb14.23,并含有微量的Ag、Au、Hg、Fe、Ni、Cu等元素。理论化学式为(Bi,Pb)_3Te_4,其中Bi>Pb。共生矿物有自然金、碲金矿、破银矿、碲铅矿、碲金银矿、碲铋矿;方铅矿、闪锌矿、黄铁矿、黄铜矿等。 自然碲反射色为纯白微带乳色,非均质性清楚,偏光色为蓝灰-棕灰色。显微硬度为H_v=85.1kg/mm~2(25g)。共生矿物有碲金银矿、碲银矿、黄铜矿等。化学成分中碲含量达98.44％,并含Ag、Cu、W、Fe、Pt等微量元素。 相似文献
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Robert Frei Minik T Rosing Tod E WaightDavid G Ulfbeck 《Geochimica et cosmochimica acta》2002,66(3):467-486
Despite superimposed metamorphic overprinting and metasomatic alterations, primary volcanic features remain preserved in low-strain domains of mafic volcanic sequences in the western Isua supracrustal belt (ISB, West Greenland). These basaltic successions represent the hitherto oldest known fragments of oceanic crust on Earth. Early Archean metasomatic fluids, rich in light rare earth elements (LREE), Th, U, Pb, Ba, and alkalies, invaded the supracrustal package and distinctively altered the basaltic sequences. Field relationships, source characteristics traced by Pb isotopes, and geochronological results provide indications that these fluids were genetically related to the emplacement of tonalite sheets into the ISB between 3.81 and 3.74 Ga ago. Subsequent early Archean metamorphism homogenized the mixed primary and metasomatic mineral parageneses of these metavolcanic rocks. Allanite occurs as the most characteristic and critical secondary metasomatic-metamorphic phase and is developed in macroscopically discernible zones of increased metsomatic alteration, even in domains of low strain. Because of its high concentration of LREE, Th, and U, this secondary mineral accounts for much of the disturbances recorded by the Sm-Nd and Th-U-Pb isotope systematics of the pillowed metabasalts.The supracrustal sequences were tectono-metamorphically affected to varying degrees during a late Archean, ∼2.6- to 2.8-Ga-old event, also recognized in the adjacent gneiss terranes of the Isuakasia area. The degree to which bulk rocks were isotopically reequilibrated is directly dependent on the different relative contributions of allanite-hosted parent-daughter elements to the overall whole-rock mass budget of the respective isotope systems. Although low-strained (initially only weakly metasomatized) pillow basalts remained more or less closed with respect to the U-Pb and Rb-Sr systems since ∼3.74 Ga, the Sm-Nd system appears to have been partially opened on a whole-rock scale during the late Archean event. This diversified behavior of the whole-rock isotope systems with respect to late Archean overprinting is explained by the combination of mass budget contributions of the respective elements added during metasomatism and the partial opening of metasomatic macroenvironments during late Archean recrystallization processes with associated renewed fluid flow. In reactivated zones of high strain, where primary metasomatic alteration is most prominently developed, late Archean partial resetting also of the U-Pb isotope system on a whole-rock scale occurred. This is consistent with an apparent late Archean age of kyanite, which initially crystallized during the early Archean metamorphism. Its age is controlled by the U-Pb systematics of allanite inclusions, which have exchanged their isotopic properties during the tectono-metamorphic event that overprinted the oceanic crustal sequence at Isua more than 1000 myr later.These results underline the need for care in the interpretation of whole-rock geochemical data from polymetamorphic rocks in general, and from the Isua oceanic crustal sequences in particular, to constrain isotopic models of early Earth’s evolution. Likewise, this study cautions against the indiscriminate use of geochemical data of metavolcanic rocks from Isua to infer models for geotectonic settings relevant for their formation. 相似文献
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R. Ellmies G. Voigtländer K. Germann M. T. Krupenin P. Möller 《International Journal of Earth Sciences》1999,87(4):589-602
In the Bashkir mega-anticline (western Urals) stratabound magnesite, siderite, fluorite and base-metal deposits are hosted by a sequence of Riphean sediments with a thickness of more than 12 km. The giant deposits of siderite (Bakal) and sparry magnesite (Satka) belong to the largest known mineral deposits of this type on Earth but are still disputed with respect to their origin. Both the Fe- and Mg-carbonate ores are clearly characterized by mimetic preservation of sedimentary and diagenetic textures of the host carbonate sediments, giving evidence of epigenetic metasomatic replacement. In the stratiform magnesite deposits of Satka, O- and C-isotopes, REE pattern and the lithostratigraphic position of the ore, point to the reflux of early diagenetic Mg-rich brines being responsible for the selective replacement of brecciated dolomite. The Bakal siderite deposits are hosted by Lower Riphean carbonate rocks and are controlled by a Lower to Middle Riphean unconformity marked by deep erosion and subsequent transgression-related sedimentation of coarse clastics. Their independence of carbonate lithofacies and their trace element distribution are indicative of metasomatic processes. Fe-bearing fluids have probably been generated by low-grade metamorphic (catagenetic) devolatization from underlying argillites, causing the metasomatic formation of large siderite ore bodies in the Bakal carbonates due to the focusing of the fluid flow by the overlying Mid-Riphean coarse clastics. 相似文献
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Dolerite dykes that cut Tertiary baslats near the Skaergaard intrusion, East Greenland, are extensively altered to metasomatic assemblages indicating large scale mobilisation of calcium and alkalis. The alteration is characterised by replacement of the dolerite by prehnite together with lesser amounts of epidote, amphibole, salite, titanite, calcite and chlorite, resulting in a complete loss of primary igneous texture. A related type of alteration in the same dykes consists of albite, epidote, amphibole and chlorite with only partial loss of primary texture. Textural relations indicate that the albitic alteration occurs first and is progressively overprinted by the later CaAl-silicate dominated alteration with a consequent large addition of calcium and removal of sodium. Quartz is absent at all stages of alteration. The metasomatic reactions are confined to the centres of a group 10 to 20 metres wide, compound dykes, that were intruded late relative to the majority of Tertiary dykes in this part of East Greenland. These dykes contain abundant leucocratic segregations, the pegmatitic and drusy nature of which suggest volatile pressure increased at late stages in dyke cooling, possibly leading to an early episode of autometasomatism. The later CaAl-silicate alteration is localised around these segregations, but affects the surrounding dolerite. Hydrogen isotope data indicates that the fluids responsible for precipitation of the CaAl-silicates were meteoric, and derived from the surrounding basalt-hosted hydrothermal system. The physical attributes of the dykes, including their width, compound nature, and high initial porosity, are all factors that favoured the influx of surrounding pore fluids into the dyke centres, where they became isolated and reacted to form the CaAl-silicate assemblages. Fluid flow into the dyke centres may have been characterised by fluid movement orthogonal to isotherms. Changes in the relative concentrations of aqueous species in fluids coexisting with albite and CaAl-silicates as a function of temperature along such flowlines are considered an important factor in driving the observed Ca–Na exchange. 相似文献
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E. N. Terekhov 《Geochemistry International》2007,45(4):364-380
The paper reports data on the distribution of REE in metasomatic rocks, including those with corundum, that were formed during the exhumation of the rocks of the Belomorian Belt at 1.9–1.75 Ga. This process is thought to have occurred concurrently with the horizontal extension and tectonic denudation of the upper crust, which, in turn, induced the massive release of fluids. The latter formed two major groups of silicic metasomatic rocks. The deepest-sitting corundum-bearing and other mafic metasomatic rocks are enriched in REE, alkalis, and alumina compared to the host rocks. The coeval acid metasomatic rocks such as orthotectites are, conversely, depleted in REE (with positive Eu anomalies), mafic elements, and HFSE but are also enriched in alumina. These complimentary rocks are thought to have been produced early during the exhumation of deep rocks under the effect of reduced fluids whose genesis was related to decompression. The silicic metasomatic rocks of the second group (with muscovite) have elevated REE concentrations (with negative Eu anomalies) and were formed by already oxidized fluids at shallower depths. The fact that the corundum-bearing metasomatic rocks are enriched in REE (in spite of the ultrabasic composition of these rocks) suggests that they were generated in an extensional environment with the participation of deep fluids, which enriched the rocks in Al, Na, K, Ba, Sr, Zr, and LREE. 相似文献
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Information about the magmatic to hydrothermal transition is preserved in late-stage features of quartz phenocrysts and endoskarn alteration in some Cu–Zn skarn deposits such as the Empire Mine in Idaho. Important features include: (1) quartz phenocrysts with strong resorption textures such as vermicular zones of igneous groundmass cutting primary quartz cathodoluminescence banding, (2) anomalous amounts of endoskarn (more than 50% of mineralized rock), (3) high F activities as evidenced by fluorite as an accessory mineral in igneous rocks, in alteration assemblages, and in fluid inclusions and by high F in hydroxyl sites in igneous biotite and amphibole, and (4) direct association of Zn, which normally is deposited distally at low temperature, with Cu in proximal locations and in endoskarn. These features are explained by the following model: (1) F lowers the solidus temperature of the magma, thus changing the timing, temperature, and duration of hydrothermal fluid exsolution. (2) Upon magmatic vapor saturation the F-rich hydrothermal fluids form bubbles that adhere to quartz phenocrysts and chemically corrode/tunnel into the quartz forming vermicular resorption textures. (3) F-rich hydrothermal fluids also promote the formation of endoskarn; silicic rocks are attacked by F-rich fluids in the same sense that carbonate wall rocks are dissolved by weakly to moderately acidic hydrothermal fluids. (4) Low fluid exsolution temperature facilitated by high F activity promotes high Zn/Cu ratios in proximal locations due to the solubility of Zn relative to Cu at lower temperatures. This model may be applicable at other localities such as the world-class Cu–Zn skarn Antamina mine, as well as some tin and rapakivi granites. 相似文献
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多色青田石是浙江青田石中的一个重要品种,具颜色丰富、纹理多变的特点。通过岩相学观察、X射线粉晶衍射物相分析、全岩主量及微量元素和同位素地球化学分析,对多色青田石的岩石学特征、矿物成分、类型划分进行详细研究,并论证了多色青田石的成矿物质、成矿流体来源及成因。研究表明:多色青田石按主要组成矿物划分属于叶蜡石型青田石和绢云母型青田石;其颜色主要与组成矿物中Fe、Ti、Cr、Mn致色元素的类型和含量有关,其次与赤铁矿(褐铁矿)浸染组成矿物的微晶间隙和充填微裂隙有关。多色青田石的成矿母岩为中酸性火山岩,成矿流体来源与大气降水有关。多色青田石主要由早期充填成因的叶蜡石矿物和晚期由中低温热液蚀变改造早期叶蜡石形成的绢云母矿物构成,是多期多阶段热液蚀变交代成矿作用的产物,多色青田石中常保留高温矿物红柱石。 相似文献
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Cr-spinel bearing wehrlite rocks of Bangriposi are found within the multiply deformed metasedimentary rocks of Singhbhum Group belonging to North Singhbhum Mobile Belt of eastern India. Detailed mineralogical and geochemical studies reveal that these rocks have suffered a two-stage alteration involving a deeper level modal and cryptic metasomatism and a subsequent shallower depth pervasive hydrothermal alteration. Cryptic metasomatism is defined by elevated LREE contents of the wehrlite and its clinopyroxne grains. Metasomatism induced changes in the modal mineralogy of the rocks include the absence of primary orthopyroxene grains, presence of secondary diopside-phlogopite(now present as vermiculite) defining disequilibrium reaction textures and secondary orthopyroxene rims around serpentinized olivine. The mineralogical and geochemical changes due to the metasomatic event present a contrasting picture in regard to the metasomatic history of the rocks. Possible scenarios involving a single stage or multiple stage metasomatism events have been discussed while explaining the metasomatic reactions that took place. An attempt has been made to estimate the REE concentrations of the final equilibrating melt from REE contents of clinopyroxene grains of the wehrlite. The possibility of the LREE-enriched equilibrating melt of the wehrlite rocks(the deeper level metasomatic agent) being similar to residual melts from the E-MORB type parental melts of nearby gabbro suite has been ruled out by geochemical modeling. REE abundance patterns of several natural enriched melts have been compared with REE pattern of calculated LREE-enriched equilibrating melt of the wehrlite and most resemblance has been observed with calcic and potassic melts. It is therefore suggested that the Cr-spinel bearing wehrlite rocks of Bangriposi has been affected by a calcio-potassic melt in deeper level, prior to the shallow level serpentinization event. 相似文献