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刘铁庚 《矿物岩石地球化学通报》1988,(4)
纤维丝状白云母发现于新疆富蕴县3号伟晶岩脉。岩脉产于海西期片麻状黑云母花岗岩岩体顶部凹陷的辉长岩一闪长岩体内。围岩发生锂白云母化、黑鳞云母化、铯黑云母化、电气石化等等。3号伟晶岩脉由岩钟和缓倾斜的脉体组成。从边部到岩钟核心可分为九个环带。各带中 相似文献
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大红柳滩二云母花岗岩被认为是白龙山等伟晶岩型锂矿的成矿母岩.为约束大红柳滩地区花岗岩-伟晶岩的岩浆-热液演化过程.本文选取大红柳滩岩体二云母花岗岩及不同矿化程度伟晶岩中的贯穿性矿物——云母和电气石,开展了背散射结构观察(BSE)和电子探针成分分析(EPMA).二云母花岗岩(Ms1)和白云母-微斜长石伟晶岩(Ms2)中云母结构均一、化学成分变化小;白云母-钠长石-锂辉石伟晶岩(Ms3)中云母类型多样,除白云母外,还发育富锂多硅白云母、铁锂云母、锂云母,后者常交代白云母.Ms3中Li、F含量突增,其中Li2O最高可达4.68%、F可达6.47%.二云母花岗岩(Tur1)和白云母-微斜长石伟晶岩(Tur2)中电气石为碱性黑电气石,白云母-钠长石-锂辉石伟晶岩中(Tur3)发育碱性锂电气石.相较于黑电气石,锂电气石具有富SiO2、Al2O3、Li... 相似文献
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四川丹巴伟晶岩型白云母矿床是我国第二大白云母产地,但其研究程度很低,形成机理的研究停留在定性推断的水平上,本文拟从流体的角度来研究其形成机理。丹巴北部的布衣沟位于白云母矿区的中心地带,自西向东穿过混合岩化变质带→部分混合岩化变质带→夕石化变质带,分布有蒋家→下蒋家→水大→二道桥等伟晶岩矿脉,其流体包裹体的均一温度峰值依次降低,CO2-H2O包裹体的数量逐渐减少,盐度有增高的趋势。碳、氢、氧同位素示踪出成岩成矿流体主要由携带深源碳的岩浆热液、建造水及脱碳反应产生的CO2组成。从蒋家→下蒋家→水大→二道桥伟晶岩脉,流体中的CO2/CH4和CO2/N2呈降低。这些特征显示出成岩成矿流体的演化过程:携带深源碳的岩浆热液自春牛场穹隆体的深部向外迁移,在部分混合岩化带与脱碳反应产生的CO2混合,在夕石带与建造水混合而稀释。因此丹巴白云母矿床属于“岩浆 变质”混合成因。 相似文献
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以小虎斯特91号伟晶岩脉中的不同结构带及蚀变围岩、交代岩、锂云母细脉中云母矿物为研究对象,通过电子探针(EMPA)和激光剥蚀等离子体质谱(LA-ICP-MS)对各结构带不同产状的云母进行主微量成分分析.研究表明,91号脉从围岩蚀变带、伟晶岩边缘带、外侧带、中间带到核部带,依次发育黑云母、白云母、富锂白云母和锂云母,伟晶岩中云母类矿物显示由白云母向锂云母演化趋势.Li在白云母和富锂云母(锂白云母和锂云母)中的置换机制不同,分别可能为2SiⅣ+ LiⅥ(←→)3A1Tot和Si+Li(←→)AlTot+Fe (Zn,Mn,Mg)(白云母)和3LiⅥ(←→)AlⅥ+ 2□Ⅵ(富锂云母,□代表空位).小虎斯特91号伟晶岩脉经历了岩浆-热液的演化过程,随着演化进行,云母中K/Rb、Mg/Li比值显著降低,Li、Rb、Cs、F含量显著增大,指示分离结晶作用是晚期熔体相Li、Rb、Cs、F富集的主要机制.但云母类矿物的主、微量元素特征显示小虎斯特91号脉岩浆-热液过渡阶段特征不明显,伟晶岩演化很快由正岩浆阶段转化为热液阶段. 相似文献
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川西甲基卡308号脉的矿物学特征及其岩浆- 热液演化示踪 总被引：1，自引：0，他引：1
甲基卡稀有金属矿床是亚洲规模最大的伟晶岩型锂矿床，308号脉为其中出露面积最大的伟晶岩脉。308号脉具有完善的分带性:细粒白云母- 钠长石- 石英带（Ⅰ）、中粗粒钠长石- 石英- 微斜长石带（Ⅱ）、中粒电气石- 钠长石- 石英带（Ⅲ）、中粗粒锂辉石- 钠长石- 石英带（Ⅳ）和中细粒锂辉石- 钠长石- 石英带（Ⅴ），并且富含稀有金属矿物（如锂辉石、绿柱石、锡石和铌钽氧化物），因此是系统研究伟晶岩演化历史和成岩成矿机制的理想实验对象。308号脉的矿物学研究较为薄弱，其岩浆- 热液演化过程及该过程中熔- 流体性质的变化规律，以及稀有金属的富集过程和影响因素尚不清楚。本文选取该脉各结构带中的贯通性矿物云母、磷灰石，以及稀有金属矿物锂辉石和特征性矿物电气石，通过详细的电子探针工作，分析它们的产状、结构特征、化学组成及其变化，结果表明:① 308号脉边部Ⅰ带（高温结晶）中电气石的出现（~5%）反映伟晶岩初始熔体具有富B的特征（>2%）；锂辉石在Ⅳ和Ⅴ带内的大量结晶说明初始熔体可能具有富Li的性质；主要含氟矿物电气石、磷灰石和云母类在岩石中的含量均较低，并且原生磷灰石具有相对偏低的F浓度（<3%），仅能形成于富F环境中的锂云母矿物也十分稀少，这些特征均表明308号脉初始熔体很可能具有较低的F含量；② 伟晶岩体系演化至Ⅴ带时发生流体出溶现象，自此进入岩浆- 热液过渡阶段，出溶流体可能具有富Cs和贫F的性质；③ 原生白云母和电气石化学成分的规律性变化说明308号脉的演化过程很可能不存在外来流体的加入；④ 308号伟晶岩的成岩和锂成矿过程主要受分异结晶作用支配，有限的出溶流体规模和伟晶岩分异演化程度（仅演化至岩浆- 热液过渡阶段，未充分进入热液阶段）对锂辉石的结晶和保存都起到了重要作用。 相似文献
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云南哀牢山和新疆可可托海伟晶岩矿物中熔融包裹体电子探针研究 总被引：5，自引：0，他引：5
运用电子探针测定了云南哀牢山伟晶岩和新疆可可 托海伟晶岩矿物中熔融包裹体及流体-熔融包裹体子矿物成分。据73个包裹体中120个测 点分 析结果,鉴定出锌尖晶石、刚玉、磷灰石、磁铁矿、白云母、黑云母、钾长石、钠长石、绿 柱石和石英等10种 子矿物,并确定矿物组合27个。其中锌尖晶石、刚玉在两地区伟晶岩熔融包裹体中属首次发 现,磷灰石成分属首次测定。两地伟晶岩矿物的熔融及流体-熔融包裹体中子 矿 物成分及矿物组合各异,包裹体中子矿物与主矿物的化学成分存在一定演化规律,可作为了 解伟晶岩浆结晶分异作用、元素演化规律的依据。研究表明,伟晶岩存在局部岩浆分异作 用,岩浆具不混溶性及非均匀性。此成果对了解伟晶岩物质成分、形成机制及成因研究具重 要意义。对岩浆岩、地幔岩及陨石研究也有一定启迪。 相似文献
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云南哀牢山和新疆可可托海伟晶岩矿物中熔融包裹体电子探针研究 总被引：6，自引：0，他引：6
运用电子探针测定了云南哀牢山伟晶岩和新疆可可 托海伟晶岩矿物中熔融包裹体及流体-熔融包裹体子矿物成分。据73个包裹体中120个测 点分 析结果,鉴定出锌尖晶石、刚玉、磷灰石、磁铁矿、白云母、黑云母、钾长石、钠长石、绿 柱石和石英等10种 子矿物,并确定矿物组合27个。其中锌尖晶石、刚玉在两地区伟晶岩熔融包裹体中属首次发 现,磷灰石成分属首次测定。两地伟晶岩矿物的熔融及流体-熔融包裹体中子 矿 物成分及矿物组合各异,包裹体中子矿物与主矿物的化学成分存在一定演化规律,可作为了 解伟晶岩浆结晶分异作用、元素演化规律的依据。研究表明,伟晶岩存在局部岩浆分异作 用,岩浆具不混溶性及非均匀性。此成果对了解伟晶岩物质成分、形成机制及成因研究具重 要意义。对岩浆岩、地幔岩及陨石研究也有一定启迪。 相似文献
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川西甲基卡二云母花岗岩和伟晶岩内发育大量原生熔体包裹体和富晶体流体包裹体。为了查明甲基卡成矿熔体、流体性质与演化特征,运用激光拉曼光谱和扫描电镜鉴定了甲基卡花岗伟晶岩型锂矿床中二云母花岗岩及伟晶岩脉不同结构带内的原生熔体、流体包裹体的固相物质。分析结果表明,甲基卡二云母花岗岩石英内熔体包裹体的矿物组合为磷灰石+白云母、白云母+钠长石、白云母+石墨;伟晶岩绿柱石内富晶体流体包裹体的矿物组合主要为刚玉、富铝铁硅酸盐+刚玉+锂辉石、锂辉石+石英+锂绿泥石;伟晶岩锂辉石内富晶体流体包裹体的矿物组合主要为磷灰石、锡石、磁铁矿、石英+钠长石+锂绿泥石、萤石、富钙镁硅酸盐+富铁铝硅酸盐+富铁硅酸盐+石英;花岗岩浆熔体与伟晶岩浆熔体(流体)具有一定的差异,成矿熔体、流体成分总体呈现出碱质元素(Na、Si、Al)、挥发分(F、P、CO_2)含量增高及基性元素(Fe、Mg、Ca)降低的特征;包裹体中子矿物与主矿物的化学成分具有一定的差别,揭示出伟晶岩熔体(流体)存在局部岩浆分异作用,具不混溶性及非均匀性。因此认为,伟晶岩熔浆(流体)为岩浆分异与岩浆不混溶共同作用的产物,挥发分含量的增高(F、P、CO_2)使伟晶岩能够与稀有金属组成各类络合物或化合物,这对于稀有金属成矿起到了至关重要的作用。 相似文献
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Prosper Rakotovao Andrianjakavah Stefano Salvi Didier Béziat Michel Rakotondrazafy Gaston Giuliani 《Mineralium Deposita》2009,44(7):817-835
The Ianapera emerald deposit is located in the Neoproterozoic Vohibory Block of southern Madagascar. The local geology consists
of intercalated migmatitic gneissic units and calcareous metasedimentary rocks, containing boudinaged metamorphosed mafic/ultramafic
lenses, all intruded by pegmatite veins. These units occur near the hinge of the tightly folded Ianapera antiform, within
a few kilometers of the Ampanihy shear zone. Emerald mineralization is hosted by metasomatic phlogopite veins, and bodies
developed within the mafic/ultramafic rocks. Based on field and textural relationships, we distinguish proximal and distal
styles of mineralization. Proximal mineralization occurs at the contact of pegmatite veins with mafic/ultramafic units; in
the distal style, pegmatites are not observed. Three types of emeralds could be distinguished, mainly on the basis of color
and mineral zoning. Some of these emeralds have the most Al-depleted and Cr-rich composition ever recorded. Another characteristic
feature to the Ianapera deposit and, to our knowledge, yet unreported, is the association of some emeralds with scapolite
in metasomatised mafic rocks. Mineral inclusions are common in most emeralds and include phlogopite, carbonates, barite, K-feldspar,
quartz, pyrite, zircon, monazite, bastnaesite, phenakite, plus Fe and Cr oxides. However, feldspar and rare earth element-bearing
minerals occur predominantly in proximal emeralds, which also have a more incompatible trace-element signature than distal
emeralds. We propose a model related to syn- to post-tectonic magmatic-hydrothermal activity. Pegmatitic bodies intruded units
of the Ianapera antiform probably during tectonic relaxation. Exsolution of fluids rich in halogens and incompatible elements
from the cooling pegmatites caused hydrothermal metasomatism of Cr-bearing mafic/ultramafic rocks in direct contact with the
pegmatites. Local fracturing favored fluid infiltration, permitting the formation of distal mineralization. Emerald composition
was controlled by the chemistry of the host rock. The presence of carbonate mineral inclusions in the emeralds and the high
F-activity indicated by elevated F-contents in newly formed minerals suggest transport of Be as a fluoride-carbonate complex.
It seems likely that beryl formation was triggered by precipitation of F-rich phlogopite, which removed the complexing ligand
from the fluid. 相似文献
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云南祖母绿的矿床地质及宝石学特征 总被引：4，自引：0，他引：4
云南祖母绿矿床产于寒武系变质岩中,矿体分别产于片麻岩的伟晶岩及云英岩脉中。属于典型的伟晶岩型或气成高温热液矿床。祖母绿的铬、钒来源于变质岩,而铍来源于伟晶岩。 相似文献
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云南大丫口祖母绿常出现颜色环带,且伴随明显成分变化,而目前颜色环带的成因仍存争议,相关的多阶段成矿假说尚缺少明确证据。文章通过电子探针和激光剥蚀电感耦合等离子质谱仪对大丫口祖母绿的颜色环带及黑色矿物包裹体进行主微量元素成分分析,并对不同类型岩脉祖母绿中流体包裹体进行显微测温分析,进而探讨祖母绿颜色环带成因与多阶段成矿的联系。成分测试结果表明,从浅绿白核部至绿色边部,V(970×10-6→10 077×10-6)、Rb(9.6×10-6→27.4×10-6)、Cs(535×10-6→3 108×10-6)、Fe(1 376×10-6→2 199×10-6)和Ga(4×10-6→14.7×10-6)等微量元素的含量急剧增加。结合绿色晶体边部中同生黑色富钒电气石包裹体的分布,有力证明了大丫口祖母绿颜色分带的形成与晶体的多阶段成矿有关。流体包裹体测试结果表明,含矿长石-方解石脉、含矿石英脉和伟晶岩-变粒岩接触带中矿物的流体包裹体盐度范围分别为3.39%~10.36%(NaCleq)、5.71%~12.29%(NaCleq)和8%~18.72%(NaCleq),指示了伟晶岩脉中祖母绿的多阶段结晶,且表明随结晶阶段演变,成矿流体的盐度逐渐升高。同时,成矿流体盐度升高也是晚期云英岩化阶段致色元素含量剧增的原因。 相似文献
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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
15.
The Macraes gold-tungsten deposit occurs in a low-angle thrust system in biotite grade Otago Schist. Native gold, scheelite, pyrite and arsenopyrite are found in and adjacent to quartz veins and silicified schist of lenticular reef zones, where the thrust system cuts through graphitic pelitic schist. Mineralization is confined to a shear zone, up to 80 m thick, which is closely sub-parallel to the regional schistosity. Chemical alteration is dominated by silicification, with some addition of Cr and depletion of Sr and Ba. Alteration extends only about 5 m from major veins. Oxygen becomes isotopically heavier away from veins due to temperature decrease as hot fluids penetrated into cooler (250°C?) rock. Graphite within the shear zone rocks has reflectance of 6–7% (in oil), similar to graphite in medium-high grade Otago Schist, and is presumed to be metamorphic in origin. This graphite has acted as a reducing agent to cause precipitation of gold where the thrust system, acting as a conduit for metamorphic fluids, intersects the graphitic schist. The metals were derived from the underlying schist pile which may include an over-thrust oceanic assemblage containing metal-enriched horizons. 相似文献
16.
在东秦岭西官庄-镇平断裂带陈阳坪地区进一步发现稀有金属矿产后,为了解铍铷矿床特征,对陈阳坪花岗伟晶岩型铍铷矿石矿物电子探针特征及矿区地质等进行了综合分析研究.本区发现伟晶岩脉11条,铍铷矿体4条,矿体长105～1100 m,厚4.26～7.00 m,BeO品位:0.035％～0.0445％,Rb2O品位:0.046％～0.123％.矿石有用矿物为钾长石、白云母、绿柱石、石榴子石等,钾长石晶体裂隙中可见绿柱石,为含铍的重要矿物;白云母集中于花岗伟晶岩中带,铯榴石不均匀出现于伟晶岩边部、构造裂隙、钾长石颗粒间隙,为含铯铷矿物.据矿石矿物电子探针分析,矿石中的铷主要赋存于钾长石、白云母矿物.产于晋宁期花岗伟晶岩中的铍铷稀有金属矿,矿体受伟晶岩脉控制,晋宁期的岩浆活动为本区铷矿、稀有元素形成提供了丰富的物质来源,经后期构造及岩浆热液活动使岩体中的铍、铷元素活化富集形成稀有金属矿床.在矿区东部及南部也存在类似地质构造特征,陈阳坪地区花岗伟晶岩的研究成果对豫西南铍铷等稀有金属矿产取得进一步找矿突破具有一定意义. 相似文献
17.
《International Geology Review》2012,54(7):647-662
Pegmatite deposits commonly occur in the 1500 km long, N-S-trending, tungstentin-bearing granitoid belt in Myanmar. Pegmatites are emplaced as veins and dikes that cut granitoid, migmatite, granitoid gneiss, gneiss, and schist. The pegmatite veins and dikes are mostly 2 to 5 meters wide and 30 to 150 meters long, and some are traceable over a distance of 300 meters. The pegmatites are composed of quartz, orthoclase, albite, microcline microperthite, and muscovite, with minor biotite, tourmaline, beryl, garnet, topaz, lepidolite, magnetite, wolframite, cassiterite, and rare columbite. They are commonly zoned, feldspars and muscovite being more abundant in the center and quartz more common at the margin. The zoning pattern is rather distinct in the pegmatite body, where tourmaline is present. The light-colored felsic minerals are confined to the core zone and the dark-colored tourmaline crystals to the outer zone. Numerous fluid inclusions have been found in quartz, topaz, and beryl. Most of the inclusions are rounded to elliptical, with a variable degree of liquid filling. All inclusions are aqueous, two-phase (liquid and vapor) inclusions with no daughter minerals. Homogenization temperatures of 173 fluid inclusions were measured in this study. Geothermometric studies indicate that the pegmatites were formed over a homogeniza-tion temperature range of 230° to 410°C. Salinities of fluid inclusions in pegmatite minerals yielded from 1.0 to 10.8 NaCl equiv. wt‰. Topaz and quartz single crystals (several cm across) from the Sakangyi pegmatite provide an opportunity to extract the fluids trapped in these minerals. The Na/K ratios of the fluid inclusions in two topaz samples were 3.0 to 4.9, and those of two quartz samples were 2.9 to 10.5, suggesting the presence of substantial potassium in the pegmatite-forming fluids. In this study, evidence for phase separation of the pegmatite-forming fluids was not observed. The post-magmatic, hydrothermal fluids responsible for the pegmatite veins evidently emanated from cooling S-type granitoids, with which they are spatially associated. 相似文献
18.
Ralph Kretz 《Australian Journal of Earth Sciences》2013,60(2):561-582
Biotite‐muscovite‐garnet gneisses at Einasleigh contain quartz‐feldspar veins composed of the same minerals as found in the enclosing rock. The vein‐gneiss boundaries are commonly irregular and on a microscopic scale, gradational. Certain amphibolite layers contain quartz‐feldspar veins composed of the same minerals as found in the amphibolite. Hornblende‐rich extraction zones surround these veins, and material balance calculations show that all or nearly all of the vein‐forming matter was locally derived. Variation in the abundance of hornblende and plagioclase in the amphibolite as a function of distance from a quartz‐feldspar vein can be expressed by error‐function curves, thus suggesting that the mineral‐segregation process was diffusion‐controlled. During the mineral rearrangement, the Na and Ca contents of plagioclase have evidently remained unchanged, but the vein hornblende has become slightly richer in Fe+3, Mg, and Ca, and poorer in Si and Al relative to hornblende in the adjacent amphibolite. A certain biotite‐plagioclase rock forms layers and boudins in the gneisses and contains pegmatite veins composed of the same minerals as found in the host rock. The plagioclase in these veins is more sodic than that in the host rock while the biotite contains slightly more Ti and Fe+2 and less Si and Mg than the biotite of the enclosing rock. The data indicate that significant portions of the vein‐forming matter at Einasleigh were locally derived. The chemistry of some minerals has changed slightly during the segregation process, resulting possibly from different diffusion rates for the different mineral‐forming constituents. 相似文献