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1.
祖母绿矿床研究现状 总被引：5，自引：0，他引：5
祖母绿矿床多为花岗岩浆期后酸性热液交代基性-超基性岩之产物。祖母绿通常呈不均匀浸染状或斑晶赋存变质片岩或其与酸性岩脉的接触带中,可将其分为热液型、气成-热液型和伟晶岩型几类矿床．包裹体研究对确定祖母绿宝石的成因、成矿地质环境条件、鉴定天然和人工宝石、确定其产地及评定其质量等级有着重要意义．我国对云南麻坡祖母绿矿床已做过较深入的研究,此外,新疆阿尔泰山、天山、甘肃北山、内蒙古中部、湖南幕阜山、四川九龙、平武等亦都有绿柱石类宝石产出．新疆发现一处碳酸岩脉祖母绿矿床,颇具前景。当前我国祖母绿研究中应加强对矿床分类、成矿及生长结晶作用、包裹体的深入研究并对已有线索加大研究及勘查力度． 相似文献
2.
世界祖母绿矿床研究现状及存在问题 总被引：1，自引：0，他引：1
从祖母绿矿产资源、成矿地质环境与成因、祖母绿的包裹体特征研究及其呈色机理等方面,对当前世界主要祖母绿矿床的研究现状、分类等进行了评述。分析了祖母绿中包裹体的形成及其与成矿环境之间的相关性。同时也对我国的祖母绿矿床作了简要介绍。最后对祖母绿矿床研究中存在的问题提出了一些建议。 相似文献
3.
Emerald deposits and occurrences: A review 总被引：3，自引：0，他引：3
Emerald, the green gem variety of beryl, is the third most valuable gemstone (after diamond and ruby). Although it is difficult to obtain accurate statistics, Colombia supplies most (an estimated 60%, worth more than $500,000,000 per year) of the world's emeralds. However there is speculation that the emerald mines in Colombia are becoming depleted. Brazil currently accounts for approximately 10% of world emerald production. Emeralds have also been mined in Afghanistan, Australia, Austria, Bulgaria, China, India, Madagascar, Namibia, Nigeria, Pakistan, South Africa, Spain, Tanzania, the United States, and Zimbabwe.Because it is difficult to obtain accurate analyses of beryllium, most published analyses of beryl are renormalized on the basis of 18 oxygen and 3 Be atoms per formula unit. The color of emerald is due to trace amounts of chromium and/or vanadium replacing aluminum at the Y site; in most cases the Cr content is much greater than that of V. To achieve charge balance, the substitution of divalent cations at the Y site is coupled with the substitution of a monovalent cation for a vacancy at a channel site.Beryl is relatively rare because there is very little Be in the upper continental crust. Unusual geologic and geochemical conditions are required for Be and Cr and/or V to meet. In the classic model, Be-bearing pegmatites interact with Cr-bearing ultramafic or mafic rocks. However in the Colombian deposits there is no evidence of magmatic activity and it has been demonstrated that circulation processes within the host black shales were sufficient to form emerald. In addition, researchers are recognizing that regional metamorphism and tectonometamorphic processes such as shear zone formation may play a significant role in certain emerald deposits.A number of genetic classification schemes have been proposed for emerald deposits. Most are ambiguous when it comes to understanding the mechanisms and conditions that lead to the formation of an emerald deposit. Studies of individual emerald deposits show that in most cases a combination of mechanisms (magmatic, hydrothermal, and metamorphic) were needed to bring Be into contact with the chromophores. This suggests the need for a more flexible classification scheme based on mode of formation. Stable isotopes can be used to estimate the contribution of each mechanism in the formation of a particular deposit. Such estimates could perhaps be more precisely defined using trace element data, which should reflect the mode of formation.Emerald may be identified in the field by color, hardness, and form. It will tend to show up in stream sediment samples but because its specific gravity is relatively low, it will not concentrate in the heavy mineral fraction. In Colombia, structural geology, the sodium content of stream sediment samples, and the lithium, sodium, and lead contents of soil samples have all been used to find emerald occurrences. Exploration for gem beryl could result in the discovery of new occurrences of non-gem beryl or other Be minerals that could become new sources of Be and Be oxide.Future efforts should go towards creating a comprehensive data base of emerald compositions (including trace elements), determination of the role of metamorphism in the formation of some emerald deposits, improved classification schemes, and more effective exploration guidelines. 相似文献
4.
Lara Loughrey Dan Marshall Peter Jones Paul Millsteed Arthur Main 《Central European Journal of Geosciences》2012,4(2):287-299
The Emmaville-Torrington emeralds were first discovered in 1890 in quartz veins hosted within a Permian metasedimentary sequence, consisting of meta-siltstones, slates and quartzites intruded by pegmatite and aplite veins from the Moule Granite. The emerald deposit genesis is consistent with a typical granite-related emerald vein system. Emeralds from these veins display colour zonation alternating between emerald and clear beryl. Two fluid inclusion types are identified: three-phase (brine+vapour+halite) and two-phase (vapour+liquid) fluid inclusions. Fluid inclusion studies indicate the emeralds were precipitated from saline fluids ranging from approximately 33 mass percent NaCl equivalent. Formational pressures and temperatures of 350 to 400 °C and approximately 150 to 250 bars were derived from fluid inclusion and petrographic studies that also indicate emerald and beryl precipitation respectively from the liquid and vapour portions of a two-phase (boiling) system. The distinct colour zonations observed in the emerald from these deposits is the first recorded emerald locality which shows evidence of colour variation as a function of boiling. The primary three-phase and primary two-phase FITs are consistent with alternating chromium-rich ??striped?? colour banding. Alternating emerald zones with colourless beryl are due to chromium and vanadium partitioning in the liquid portion of the boiling system. The chemical variations observed at Emmaville-Torrington are similar to other colour zoned emeralds from other localities worldwide likely precipitated from a boiling system as well. 相似文献
5.
Precambrian emerald deposits of Brazil are found in a typical geologic setting with Archean basement and supracrustal, ultramafic, granitoid and rocks. Volcano-sedimentary series occur as imbricated structures or as bodies affected by complex folding and deformation. Emerald mineralization belongs to the classic biotite-schist deposit, which formed by the reaction of pegmatitic veins within ultrabasic rocks. At the same time, pegmatite-free emerald deposits linked to ductile shear zones are also known. Emerald formation is attributed to infiltrational metasomatic processes provoking a K-metasomatism of the ultrabasic rocks and also a desilication of the pegmatites. A new classification based on the geological setting, structural features, and ore paragenesis is proposed. 相似文献
6.
巴西典型祖母绿矿床介绍 总被引：2，自引：1，他引：2
巴西的祖母绿矿床主要属于所谓的片岩型祖母绿矿床。它们产于富含暗色岩和伟晶岩的古老地盾区内。与矿化有关的伟晶岩往往脉幅小，分异不完全。最有利于矿化的围岩是富镁的滑石片岩，含滑石片岩，含滑石大理岩和黑云母片岩等。 相似文献
7.
8.
电子探针和微区X射线衍射研究陕西镇安钨-铍多金属矿床中祖母绿级绿柱石 总被引：4，自引：3，他引：1
南秦岭镇安地区发现了以白钨矿-绿柱石为矿石矿物组合的矿床新类型。为查明该矿床中首次发现的翠绿色祖母绿级绿柱石的致色机理并进一步揭示其成矿机制,本文在野外地质调查的基础上,对绿柱石开展了电子探针与微区X射线衍射等矿物学研究。结果表明:矿区中首次发现的祖母绿级绿柱石,呈自形晶产于石英(方解石)脉中并与白钨矿共(伴)生。祖母绿级绿柱石从核部至边缘V2O3含量较高,分别为0.64%~0.98%和1.04%~1.42%,且有增高趋势。X射线衍射数据表明区内祖母绿为"正常"绿柱石,同时存在Al■Me2+和Be■Li两种类质同象替换机制。V为本区祖母绿主要致色元素,来自于区内碳质板岩、金云母片岩及白云质大理岩等地层,Be、Si、Al等主要元素则来自于深部酸性岩浆岩。本次发现为该矿床中钨、铍矿产资源的综合开发利用提供了基础地质资料,并为南秦岭在区域及深部继续寻找稀有金属矿指出新的找矿方向。 相似文献
9.
碳酸盐成岩作用是沉积学最为活跃的领域之一,与之有关的研究成果会直接影响人们对碳酸盐油气储层形成机制和层控矿床形成机制的理解。近年来,碳酸盐成岩作用在多个领域取得了令人瞩目的研究成果,主要包括以下几个方面:(1)实验室沉淀白云石获得成功:人们模拟海水(泻湖)条件下的细菌硫酸盐还原环境,在常温下沉淀出具有序反射的白云石。(2)热液白云化作为新的主流模式成为关注的热点:人们已认识到热液白云岩储层、沉积-喷流型铅锌矿床和Mississippi河谷型铅锌矿床具有共同的形成机制,它们均受构造(伸展、走滑构造)和热流体流动的强烈控制。(3)深埋藏条件下封闭系统的白云化作用受到关注:一些对油气储集空间和层控矿床有较大意义的白云化作用主要是在相对封闭条件下发生的,在对岩石储集空间的变化的贡献上以及在相应的地球化学指标上不同于开放条件下的白云化作用。(4)混合水白云化模式受到质疑:人们重新研究了作为混合水白云化典型地点的美国威斯康星弧碳酸盐的成岩作用,根据流体包裹体分析、阴极发光分析、偏光显微镜观察及稳定同位素分析等方法并结合有机物成熟度的数据,得出威斯康星弧与白云化有关的水-岩相互作用是由与温度升高有关的浓卤水导致的,白云化作用是热水成岩作用的结果。(5)淡水环境的成岩机制受到挑战:新近研究证明,大范围的低位体系域中可以没有具化学活性的淡水透镜体,海水环境同样可以产生成熟的石灰岩,细菌硫酸盐还原作用可以引起海水对碳酸盐的不饱和。(6)锶同位素在海相碳酸盐研究中的广泛应用:由于锶同位素不像氧、碳同位素那样因温度、压力和微生物作用而分馏,矿物可直接反映流体的同位素组成,地质历史中海水锶同位素组成也具有独特的长期变化趋势,这使得海相碳酸盐的锶同位素组成在沉积期后流体示踪中得到广泛应用。(7)硫酸盐还原作用对碳酸盐成岩作用的影响受到重视:如BSR和TSR可减小SO42-对白云石沉淀(或白云化)的动力学屏障,其产物H2S和CO2可在不同条件下对碳酸盐储层产生影响,BSR和TSR可提高成岩流体锶含量,甚至在形成天青石矿床中也具极大的潜在价值。 相似文献
10.
The Mananjary emerald deposits are hosted in phlogopite-rich rocks formed through metasomatic alteration of meta-ultrabasites (hornblendites) at about 500 °C and 2 kbar due to infiltration of fluoride-rich fluids. A thermodynamic model explains the role of fluoride-complexation in the transport of Be and points to co-precipitation of F-phlogopite as the cause of beryl deposition. To cite this article: B. Moine et al., C. R. Geoscience 336 (2004). 相似文献
11.
Stratiform barite deposits (SB) and vein Pb-Zn barite deposits (VB) are known in a rift basin in central Guangxi. The former
is hosted in the Upper Devonian chert beds and the latter occurs in the Middle and Lower Devonian neritic sediments. The two
types of mineralization are believed to have a common origin as evidenced by the following observations: (1) Spatially, they
are closely associated with each other. (2) They possess a basic similarity, but also show systematic variations from VB to
SB in terms of ore composition, structural and textural features, temperature of mineralizing solutions, country rocks and
alteration. (3) Their δ34S values are more similar to the average value of marine sulfate in Late Devonian than to that in Early Devonian. A model
for thermal water deposition has been proposed to illustrate the genesis of these deposits. 相似文献
12.
俄罗斯富铁型水热法合成祖母绿特征研究 总被引：1，自引：0，他引：1
针对近期市场上出现的俄罗斯富铁型水热法合成祖母绿,采用电子探针、傅里叶变换红外光谱仪和紫外-可见光谱仪等测试分析方法,从化学成分、宝石学特征及谱学进行初步研究。结果表明,俄罗斯富铁型水热法合成祖母绿内部有特征的红棕色假六方片状金属固体包裹体,化学成分以贫碱富铁含铜为特征,环状分子通道内I型水和Ⅱ型水同时存在,在760nm处有由Fe3＋的d-d电子跃迁导致的特征吸收峰。除此之外,笔者对比分析了俄罗斯富铁型、传统水热法合成祖母绿、桂林水热法合成祖母绿、助熔剂法合成祖母绿及天然祖母绿样品在谱学上的差异。 相似文献
13.
《International Geology Review》2012,54(5):400-424
The fluid composition, δD of channel H2O, and δ18O of lattice oxygen have been determined in beryl and emerald from a variety of geological environments and used to constrain the origin of the parental fluids from which beryl has grown. Step-heating analyses performed by quadrupolar mass spectrometry were used to quantify the composition of the fluid phases in beryl from granitic pegmatites and greisens and emerald from Brazil, Colombia, and Afghanistan. An important conclusion is that beryl and emerald have a similar fluid composition, with concentrations of H2O being greater than 90% of the total water in the mineral irrespective of the age of formation (2.0 Ga to 32 Ma) and tectonic settings. However, the Brazilian Santa Terezinha shear-zone emerald deposit contains abundant CO2, up to 13 wt% of the total fluid. A second conclusion is that the channel H2O content for some Brazilian emeralds is higher than the range defined for beryl in the literature, especially for those related to the shear-zone type (2.99 lt; H2O < 3.16 wt%) and the pegmatite type from the Pombos, Pela Ema, and Pirenopolis deposits (2.78 < H2O < 3.01 wt%). Colombian emeralds have very low H2O contents (1.30 < H2O < 1.96 wt%), among the lowest in the world. Brazilian, Colombian, and Afghanistani emeralds have contrasting and restricted ranges of δ18O values. In Brazil, emeralds related to pegmatites have a systematic δ18O inter-deposit variability (+6.3 < δ18O < +12.4‰). The calculated δ18O of the fluid was buffered by the host ultrabasic rocks during fluid-rock interaction. Emerald and cogenetic phlogopite related to shear-zone-type deposits have a quite restricted δ18O range (+12.0 < δ18O 7lt; +12.4‰); the calculated is interpreted to represent the original isotopic composition of the hydrothermal fluid. Relative to Brazil, the δ18O of Colombian and Afghanistani emeralds shows strong enrichment in 18O (+13.4 < δ18O < +23.6‰), and the high calculated δ18O of the fluid suggests extensive reaction with 18O-rich sedimentary or metasedimentary rocks. In Brazil, the δD composition of channels in emerald and the calculated δ18OH2O for phlogopite are compatible with both magmatic and metamorphic origins. A magmatic origin is supported for emeralds associated with the pegmatitic Socotó and Carnaiba deposits (mean δD = ?37.8 ± 8‰) and a metamorphic origin is suggested for the Santa Terezinha shear-zone type (mean δD = ?32.4 ± 3‰). A metamorphic origin is proposed for Colombian emeralds. Afghanistani emeralds have a δD composition of channels (mean δD = ?46.3 ± 1.3‰) that is compatible with both magmatic and metamorphic origins. 相似文献
14.
Emerald deposits of Colombia are confined to lower Cretaceous shales of the Eastern Cordillera. The tectonic pattern of the deposits is related to deep reverse and large regional fault systems. Hydrofracturing is the main factor controlling emerald mineralization. It permitted to the hydrothermal solutions to permeate through fractures but also along stratification planes forming in this case stratabound mineralizations. Emerald occurs in calcite veins, veinlets, pockets and brecciated zones associated mainly with pyrite, quartz, parisite, codazzite and fluorite. Emerald mineralization belongs to an epigenetic hydrothermal process. The alternance of arenite-shale formations in the Cretaceous probably played an important role in the accumulation of solutions and in the propagation of the hydrothermal channels. The origin of emerald involves chemical elements mobilized by the fluids in the Cr-V-Fe-Al-Si-bearing black shales. The source of beryllium remains a problem and is discussed in the paper. 相似文献
15.
A. A. Beus 《Journal of Geochemical Exploration》1979,11(2):195-208
Emerald-bearing deposits in the Cordillera Oriental are structurally controlled, localized at the intersection of two fault systems. At these intersections zones of intense fracturing affected by sodium and carbonate metasomatism host the emerald mineralization. Albitization, carbonatization and hydrothermal leaching of potassium and trace metals are characteristics of the metasomatically altered Cretaceous black shales which compose the emerald-bearing tectonic zones.Stream sediments collected in areas which have metasomatically altered shales in the drainage basin have a low K/Na ratio. It is possible to use this ratio, or the sodium content of the sediments, to locate areas worthy of further exploration. 相似文献
16.
Shreeram Suman Sahu Sahendra Singh Jyoti Sankar Satapathy 《Journal of the Geological Society of India》2018,92(3):291-297
Emerald, the green gem variety of beryl (Be3Al2Si6O18), is the third most valuable gemstone after diamond and ruby. The green colour appearance of the crystal is due to trace of Cr3+ and V3+, which replaces Al3+ ions in the crystal lattice of beryl. The hue of green colour of emerald depends on the quantity of Cr3+ and V3+ present in the crystal. Be is incorporated along with Cr and/or V during the process of crystallization. Since Be is relatively rare in the upper continental crust, therefore specific geological and geochemical parameters are required for Be to be incorporated in the crystal lattice of emerald.The present work was carried out to understand the lithological and structural control of emerald occurrences in and around Gurabanda area within the Singhbhum shear zone (SSZ) of Singhbhum crustal province, eastern India. The biotite and serpentine schist belong to the Paleoproterozoic Dhanjori Group and constitute the major lithology of the area. Pegmatite and biotite schist contains a variety of gem minerals in abundance in the area and the gem quality emerald occur at the contact zone of quartz vein and mica-schist. Lithology and structure are the main controlling factors of gem-mineralization in the study area. The study indicates that regional metamorphism and deformation processes along the shear zone played a significant role in the formation of emerald deposits. It is inferred that Singhbhum shear zone facilitated a favourable condition, where the Be bearing pegmatites interacted with Cr bearing mica schist or ultramafic rocks to produce emerald crystal. 相似文献
17.
《International Geology Review》2012,54(10):924-937
40Ar/39Ar plateau ages and/or K-Ar ages have been obtained on the emerald deposits of Brazil. These include: Socotò (2104 ± 41 Ma), Carnaíba (2019 ± 40 Ma), Pirenòpolis (650 ± 2 Ma), Santa Terezinha (520 ± 2 Ma), Coqui (516 + 4 Ma), Capoeirana (509 ± 2 Ma), Pombos (502 ± 8 Ma), and Juca (490 ± 8 Ma). These ages reveal regionally coherent trends that are consistent with two periods of emerald formation in Brazil–～2 Ga and between 650 and 500 Ma. The age of the Santa Terezinha deposit (520 ± 2 Ma), linked to a shear-zone system, helps define the metallogenic role (Be, Au, Sn) played by ductile-brittle shear-zone systems in the state of Goias and the economic importance of the Brasiliano tectonic event. 相似文献
18.
还原性流体与斑岩型矿床成矿机制探讨 总被引：4，自引：0，他引：4
目前已经广泛认同斑岩型Cu-Mo-Au矿床是在氧化性相对较高的含矿流体作用下形成的。但是随着研究的深入,逐渐发现了一系列具备还原性特征的斑岩型矿床,这些矿床往往不发育表征高氧逸度的原生磁铁矿和硫酸盐矿物。本文针对目前发现的与还原性I型花岗岩相关的斑岩矿床进行了综合分析,发现此类矿床的成矿流体中普遍含有CH4等还原性流体成分,并且伴生有CO2。结合相关资料分析认为还原性流体中所含有的CH4可能来自邻近的S型花岗岩的混染作用,但也不排除是经地球排气作用从地幔进入到地壳的可能性。结合典型还原性斑岩型矿床研究,给出了一个化学模型,认为CH4和SO2属于岩浆系统自生成分,在特定化学物理阶段发生反应,形成H2S和CO2,从而抑制了硫酸盐矿物的形成。反应所生成的H2S可以与Mo结合形成辉钼矿矿化,而Cu-Au由于在氧逸度较低的环境下具备更高的活性,易于富集在气相流体中,所以可以迁移到某一距斑岩系统较远的有利部位沉淀成矿,从而形成以Mo矿化为核心区,外围Cu-Au矿化的模式。 相似文献
19.
"一带一路"地区由于特殊的地质构造环境,发育宝玉石矿床,特别是高级宝玉石矿床。对于相关国家的高级宝玉石矿床,前人虽进行过一定程度的研究,但并未从"一带一路"的角度进行探索研究。鉴于此,在相关资料研究的基础上,对"一带一路"地区高级宝玉石矿床的分布规律进行了归纳与总结,以期为中国企业掌握"一带一路"地区宝玉石信息提供参考资料,同时为相关国家勘查开发宝玉石矿床提供资料,促进其经济发展。研究表明,金刚石矿床主要分布在俄罗斯、中国、印度等地,尤以俄罗斯西伯利亚地区为主要生产地,分为原生矿床和次生矿床2种;翡翠矿床主要分布在缅甸、俄罗斯、哈萨克斯坦和中国,其中缅甸是翡翠产量最高、品质最好的国家,产量占全世界产量的95%,分布在缅甸北部克钦邦的帕敢—道茂一带,有原生矿床和次生矿床2种类型;祖母绿矿床分布比较广泛,在阿富汗、哈萨克斯坦、巴基斯坦、印度、俄罗斯和中国都有分布,尤以俄罗斯乌拉尔地区祖母绿较出名,分为气成热液型和伟晶岩型2种;软玉矿床分布在中国、俄罗斯和韩国,尤以中国新疆的和田玉最出名,有岩浆热液型和变质热液型2种类型。 相似文献
20.
《Russian Geology and Geophysics》2015,56(3):435-445
The spatial coexistence and synchronous formation of magmatogene porphyry Cu–Mo mineralization and epithermal gold mineralization are due to the genetic relationship between their formation processes. This relationship might be due to the generation of metal-bearing fluids of different geochemical compositions by the porphyry ore-magmatic system, which then participate in the formation of magmatogene porphyry Cu–Mo(Au) and associated epithermal gold deposits. Synthesis of fluid inclusions in quartz was performed for experimental study of the behavior of Cu, Mo, W, Sn, Au, As, Sb, Te, Ag, and Bi in heterophase fluids similar in composition and aggregate state to natural ore-forming fluids of porphyry Cu–Mo(Au) deposits. We have established that at 700 °C, a pressure decrease from 117 to 106 MPa leads to a significant enrichment of the gas phase of heterophase chloride fluid with Au, As, Sb, and Bi. The heterophase state of carbonate–chloride–sulfate fluids is observed at 600 °C and 100–90 MPa. It characterizes the highly concentrated liquid carbonate–sulfide phase–liquid chloride phase–low-density gas phase equilibrium. A decrease in the pressure of heterophase carbonate–chloride–sulfate fluid leads to a noticeable enrichment of its chloride phase with Cu, Mo, Fe, W, Ag, Sn, Sb, and Zn relative to the carbonate–sulfate phase. The processes of redistribution of ore elements between the phases of heterophase fluids can be considered a model of generation of metal-bearing chloride fluids, which occurs in nature during the formation of porphyry Cu–Mo(Au) deposits, as well as a model of generation of gas fluids supplying Au, Te, As, and other ore elements to the place of formation of epithermal Au–Cu and Au–Ag mineralization.© 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved. 相似文献