俄罗斯极地乌拉尔硬玉岩成因矿物学研究

俯冲带是壳-幔物质循环的重要场所,硬玉岩可以记录这一循环过程。文中总结了俄罗斯极地乌拉尔硬玉岩的研究进展。硬玉岩呈脉状或透镜状产在蛇纹石化的方辉橄榄岩中,主要由硬玉和绿辉石组成。根据结构和颜色,硬玉可识别出两个世代。硬玉韵律环带发育,含有H₂O和CH₄流体包裹体,显示从流体中结晶的特征。硬玉岩中的锆石为热液锆石,锆石稀土元素中La_N/Yb_N=0.001~0.01,Lu_N/Gd_N=10~83,Ce/Ce^*=2.8~72,显示正异常,δEu=0.53~1.02,类似于岩浆锆石。锆石的¹⁷⁶Hf/¹⁷⁷Hf=0.282 708~0.283 017,ε_Hf(t)=+6~+17,类似于N-MORB的Hf同位素组成,锆石δ¹⁸O组成为5.03‰~6.04‰,平均δ¹⁸O为(5.45±0.11)‰,类似于岩浆热液和地幔的氧同位素组成。这可能反映了锆石是被俯冲带流体从途经火成岩中捕获的或者形成锆石的流体与寄主岩(方辉橄榄岩)达到了平衡。硬玉岩稀土元素配分模式近平坦或轻稀土元素略显富集,La_N/Yb_N比值为0.82~2.42,δEu为1.2~1.6,显示正异常,这与寄主岩稀土元素配分模式相似。富集Sr、Ba、Zr、Hf,Nb为负异常,与岛弧岩浆特征类似。(⁸⁷Sr/⁸⁶Sr)_t为0.703 400~0.703 519(t=368 Ma),变化较小,与古海水差别明显;ε_Nd(t)值为+0.77~+5.61,变化较大,与寄主岩(方辉橄榄岩)的Nd同位素组成类似,但不同于海水及沉积物的Nd同位素组成,表明硬玉岩的物质来源与寄主岩有明显继承关系,海水与沉积物的贡献不是主要的。矿物学和岩石学证据支持极地乌拉尔的硬玉岩主要是俯冲带流体与橄榄岩相互作用后并在其中结晶的产物。     

危地马拉紫色翡翠的矿物组成特征及意义

通过薄片鉴定、阴极发光、LIBS、LA-ICP-MS等手段,确定了危地马拉紫色翡翠的矿物组成有硬玉、钠长石、钙铝榴石、榍石与金红石,这些矿物的结晶顺序为金红石+榍石-白色硬玉-蓝紫色硬玉+钙铝榴石-钠长石,具有从温度降低的流体中结晶演化的特征。蓝紫色硬玉的Ti含量较高。在外观上,危地马拉紫色翡翠含有钙铝榴石造成的淡红色团块、含Ti硬玉造成的蓝紫色团块以及伴随这些团块的无色透明的钠长石,与缅甸产的紫色翡翠有较为明显的区别。     

危地马拉翡翠宝石矿物学特征及其与缅甸翡翠的对比研究

危地马拉目前已成为仅次于缅甸的第二大翡翠原料供应地。这两个产地翡翠辨别的需求愈发迫切,且应用意义较大。采用显微镜观察、电子探针分析及背散射电子照相获得危地马拉蓝水料翡翠的矿物成分及结构构造特征,结合两产地翡翠产出的大地构造环境、自然地理环境、原石特征与矿物成分特征等进行对比分析。总体上,危地马拉翡翠次生原石有一定的磨圆,呈次棱角状,“皮”(风化皮)厚度较薄,较少出现翻砂现象,由“皮”向里,极少甚至几乎不存在“红雾”。相对地,缅甸翡翠次生原石发育显著的球状风化,原石通常有较好的磨圆度,棱角状不明显,“皮”厚度可达数厘米,用手压磨有显著的翻砂现象, “皮”“肉”之间偶可见“红雾”。硬玉与绿辉石成分判别图显示危地马拉翡翠中硬玉和绿辉石呈相对富Ca、贫Na的特征,而缅甸翡翠中硬玉和绿辉石整体呈相对贫Ca、富Na的特征。在Fe含量上,危地马拉翡翠中硬玉的Fe含量较缅甸翡翠中硬玉的Fe含量偏低,而危地马拉翡翠中绿辉石的Fe含量较缅甸翡翠中绿辉石的Fe含量偏高。对翡翠外观特征的充分对比和对判别图的综合分析可应用于实际中翡翠产地的区分。     

哈萨克斯坦伊特穆伦硬玉岩的矿物学特征

硬玉岩是一种较为少见的高压低温变质岩,不仅具有重要的科研价值,也是一种名贵的玉石材料。本文对产于哈萨克斯坦卡拉干达州伊特穆伦矿区的硬玉岩进行了岩相学观察和矿物化学成分分析,并与缅甸、俄罗斯和危地马拉的硬玉岩进行对比。结果表明,哈萨克斯坦硬玉岩主要组成矿物为硬玉、绿辉石以及少量方沸石和钠沸石,具有粒柱状变晶结构,硬玉矿物的平均化学成分为w(SiO2)=58.38%,w(Al2O3)=21.88%,w(Na2O)=12.69%,w(CaO)=3.40%,w(MgO)=2.58%,w(FeO)=0.29%。不同产地样品中绿辉石和硬玉的SiO2含量相差不大。哈萨克斯坦样品中绿辉石Na2O和FeO的含量略低于缅甸、俄罗斯和危地马拉,MgO和CaO稍高于其它3个产地,硬玉MgO和CaO略高于其它3个产地。     

缅甸硬玉岩中后成合晶冠状体的含水性研究

基于多期次流体活动在硬玉岩及后成合晶冠状体的交互作用过程中发挥了至关重要的作用,采用电子探针、显微红外光谱等测试方法,从微尺度角度重点对缅甸角闪石质硬玉岩中角闪石+铬硬玉+硬玉后成合晶冠状体的成分和结构羟基赋存状态进行了研究。结果显示,参与后成合晶冠状体形成的流体组分较为复杂且形成过程是多阶段的;后成合晶冠状体的共生矿物组合不同,角闪石质硬玉岩中普遍发育角闪石+铬硬玉+硬玉化学成分环带;后成合晶冠状体中核部角闪石结构羟基含量较为均一,铬硬玉边缘至硬玉、硬玉晶粒中的结构羟基含量呈较为规律的递增趋势。核部角闪石中结构羟基均一且外层硬玉中结构羟基含量的变化规律表明缅甸硬玉岩中后成合晶冠状体的形成环境相对稳定,主要以多期次流体交代为主,未出现较大规模的动力变质作用。缅甸硬玉岩中后成合晶冠状体成分及水含量的变化规律有助于解析该地区俯冲带流体参与硬玉岩交互作用的轨迹,从而为缅甸硬玉岩的成岩机制提供一定的佐证。     

危地马拉与缅甸含绿辉石翡翠的矿物学对比研究

以危地马拉蓝水料与缅甸油青种翡翠为研究对象,通过显微镜观察、岩石薄片观察、X射线粉末衍射分析、激光拉曼光谱分析、扫描电镜分析、电子探针分析等测试手段对两者进行了常规宝石学特征、结构特征、杂质矿物、化学成分等方面的对比研究。结果表明,危地马拉蓝水料发育等粒变晶结构,主要成分为硬玉,含有绿辉石,硬玉环带以2～3层为主,绿辉石分别以自形颗粒、交代残余、沿微裂隙充填3种形式存在,其中白色点状物为钠长石,绿色点状物为霓辉石和绿辉石的混杂物;缅甸油青种翡翠以硬玉为主颗粒相对粗大,呈柱粒状镶嵌结构,硬玉发育3～5层环带结构,绿辉石以脉状充填硬玉颗粒间隙或被硬玉颗粒交代呈孤岛状。危地马拉蓝水料硬玉颗粒与脉状绿辉石的CaO含量均高于缅甸油青种翡翠,另外由于霓辉石的存在,推测两产地翡翠结晶环境中的Ca、Fe含量可能存在差异。     

危地马拉硬玉岩与硬玉化绿辉石岩的岩石学特征及其地质意义

位于北美-加勒比板块俯冲带内的危地马拉硬玉岩区产有硬玉岩、榴辉岩、钠长岩等岩石类型,但绿辉石岩还没有详细报导过。研究样品为该区的硬玉岩和绿辉石岩,前者主要由Jd端元含量较高的硬玉组成,具有粒、柱状镶嵌结构。硬玉晶体具有显著的成分振荡环带,其核部及其背散射电子图像的浅色区Jd端元含量为94.81%～95.48%;暗色区Jd含量大于97.92%。后者绿辉石岩具有交代结构,主要由绿辉石和硬玉组成。其中绿辉石的CaO(9.01%～10.80%)和MgO(6.09%～7.94%)含量较高,FeO(2.84%～4.89%)含量较低;硬玉的CaO、MgO和FeO含量变化范围较大,分别为0.59%～4.30%,0.26%～3.05%,0.76%～2.87%。硬玉岩中流体包裹体的存在,以及绿辉石岩中显著的硬玉交代绿辉石现象说明其成因与缅甸硬玉一样,是硬玉质流体通过结晶-交代作用形成。硬玉岩中硬玉振荡的环带结构反映形成时温度-压力-组分体系存在振荡变化,平直连续的环带边界反映结晶时P-T条件位于硬玉稳定的低温高压区域。该区绿辉石岩的硬玉化作用清楚,能够观察到三期硬玉岩化作用现象,说明绿辉石岩可能是在硬玉岩的形成过程中,硬玉质流体与原岩辉石岩作用的结果,这进一步阐明了俯冲带内硬玉岩区硬玉质流体的广泛透入性与结晶交代作用的多样性。     

Dissakisite-(Ce) chemical composition: some implications for its origins

Euhedral dissakisites from Trimouns dolomite mine, France, is compositionally zoned. Back-scattered electron (BSE) images reveal that each of the described dissakisite crystals has three distinct compositional zones: normal zoned core (Mg-rich), oscillatory zoned middle (Ca–Al-rich) and homogeneous rim (Fe–ΣREE-rich). The latter zone with Fe²⁺ > Mg corresponds to allanite-(Ce). Dissakisite-(Ce) also displays pronounced zoning in Fe/Mg which may suggest that the temperature of crystallization continuously decreased from core to rim. Despite a systematic increase in Fe/Mg of the dissakisite with an allanite rim, there is no monotonic decrease in the REE zoning: the normal zoned core and homogeneous rim are rich in La, Ce and Pr, but the relatively REE-poor oscillatory zoned middle is relatively abundant in Y, Sm and Gd. Discontinuous variation in REE content of the dissakisite, with the allanite rim may indicate a localized change in either the relative concentration of various ligands or pH of the crystallizing fluid. Observations under the polarizing microscope confirm that the different zones have simultaneous extinction. These chemical and optical observations suggest that epitaxial crystallization of dissakisite, from Trimouns, passes through three formation stages. The ternary Fe²⁺–Mg²⁺–(Al + Fe)³⁺ diagram illustrates that in general dissakisite can be classified into two groups, (Al + Fe)³⁺-rich and an Mg-rich; dissakisite from Trimouns belongs to the former group. Chondrite-normalized REE patterns of dissakisites from Trimouns are similar to those of allanites formed by hydrothermal fluids. In conclusion, it is clear from the above two geochemical characteristics that dissakisites from Trimouns are of (Al + Fe)³⁺-type, and were derived from hydrothermal fluids.     

Jadeitites, albitites and related rocks from the Motagua Fault Zone, Guatemala

Jadeitites from Guatemala are found as weathered blocks in tectonized serpentinite in a 15-km zone north of the Motagua Fault Zone. Rock types found with jadeitite include albitites, albite-mica rocks, omphacite/taramitic amphibole-bearing metabasites, chlorite-actinolite schists, talc-carbonate rocks and antigorite schists. In addition to the predominant jadeitic (Jd₉₃_₁₀₀) pyroxene, common phases in jadeitite include micas (paragonite and/or phengite ± rarer phlogopite), omphacite, albite, titanite /Pm zircon, apatite and graphite. Conditions of jadeitite formation are 100-400d? C, 5-11 kbar with 0.0 > log₁₀a_sio2≥= 0.7. Fluid inclusions, coarse textures, vein structures, and rhythmic zoning of pyroxene indicate an aqueuos fluid was involved. Jadeitites are either (1) metasomatic modifications of former felsic-to-pelitic inclusions that have undergone silica depletion plus efficient soda exchange and enrichment, or (2) solution precipitations derived from such a source. The close spatial relationship of faults and shear zones, serpentinites, and jadeitites suggests jadeitites form in a relatively high-P/T setting with substantial flow of sodic fluid in a tectonized zone. Most Guatemalan jadeitites are extensively altered to analcime, albite, taramitic amphibole, (clino)zoisite ± nepheline and preiswerkite. This alteration reflects depressurization /Pm heating to below the jadeite + fluid = analcime reaction at high a_Na. With progressive alteration, analcime and nepheline are replaced by albite; the increase in silica content may result from fluid flowing up a tectonized zone reaching saturation with an albite assemblage. Albitite phases, albite, actinolite, zoisite, /Pm chlorite, phengite, K-feldspar and quartz, record conditions of c. 3-8 kbar at T < 400d? C, indicating a clockwise P-T trajectory of the blocks. Barium aluminosilicates—banalsite, celsian, cymrite and hyalophane—are common minor late-stage phases in jadeitites and albite-rich rocks. Barian phengite is common in albite-mica rocks.     

The La Unión Au ± Cu prospect,Camagüey District,Cuba: fluid inclusion and stable isotope evidence for ore-forming processes

The Camagüey district, Cuba, is known for its epithermal precious metal deposits in a Cretaceous volcanic arc setting. Recently, the La Unión prospect was discovered in the southern part of the district, containing gold and minor copper mineralization interpreted as porphyry type. Mineralization is hosted in a 73.0 ± 1.5 Ma calc–alkaline I-type oxidized porphyry quartz diorite intrusive within volcanic and volcaniclastic rocks of the early Cretaceous Guáimaro Formation. The porphyry is affected by propylitic alteration and crosscut by a network of quartz and carbonate veinlets and veins. Chlorite, epidote, sericite, quartz, and pyrite are the main minerals in the early veins which are cut by late carbonate and zeolite veins. Late barite pseudomorphously replaces pyrite. Gold is associated with pyrite as disseminations in the altered quartz diorite and in the veins, occurring as inclusions or filling fractures in pyrite with 4 g/t Au in bulk samples, and up to 900 ppm Au in in pyrite. Fluid inclusion and oxygen isotope data are consistent with a H₂O–NaCl–(KCl) mineralizing fluid, derived from the quartz diorite magma, and trapped at least at 425°C and 1.2 kbar. This primary fluid unmixed into two fluid phases, a hypersaline aqueous fluid and a low-salinity vapor-rich fluid. Boiling during cooling may have played an important role in metal precipitation. Pyrite δ³⁴S values for the La Unión prospect range between 0.71‰ and 1.31‰, consistent with a homogeneous magmatic sulfur source. The fluids in equilibrium with the mineralized rocks have estimated δ¹⁸O values from 8‰ to 11.8‰, calculated for a temperature range of 480–505°C. The tectonic environment of the La Unión prospect, its high gold and low copper contents, the physical–chemical characteristics of the mineralizing fluids and the isotopic signature of the alteration minerals and fluids indicate that the La Unión gold mineralization is similar to the porphyry gold type, even though the ore-related epidote–chlorite alteration can be classified as propylitic and not the classic potassic and/or phyllic alteration. The low copper contents in the prospect could be due to a mineralizing fluid previously saturated in copper, which is indicated by trapped chalcopyrite crystals in high-temperature fluid inclusions. The low-temperature paragenesis, represented by carbonate, zeolite and barite, indicates epithermal overprint. The study shows the potential for other gold porphyry-type deposits in the Cretaceous volcanoplutonic arc of Cuba.     

Geochemistry of major and rare earth elements in garnet of the Kal-e Kafi skarn,Anarak Area,Central Iran: Constraints on processes in a hydrothermal system

Grossular-andradite (grandite) garnets, precipitated from hydrothermal solutions is associated with contact metamorphism in the Kal-e Kafi skarn show complex oscillatory chemical zonation. These skarn garnets preserve the records of the temporal evolution of contact metasomatism. According to microscopic studies and microprobe analysis profiles, the studied garnet has two distinct parts: the intermediate (granditic) composition birefringent core that its andradite content based on microprobe analysis varies between 0.68–0.7. This part is superimposed with more andraditic composition, and the isotropic rim which its andradite content regarding microprobe analysis ranges between 0.83–0.99. Garnets in the studied sample are small (0.5–2 mm in diameter) and show complex oscillatory zoning. Electron microprobe analyses of the oscillatory zoning in grandite garnet of the Kal-e Kafi area showed a fluctuation in chemical composition. The grandite garnets normally display core with intermediate composition with oscillatory Fe-rich zones at the rim. Detailed study of oscillatory zoning in grandite garnet from Kal-e Kafi area suggests that the garnet has developed during early metasomatism involving monzonite to monzodiorite granitoid body intrusion into the Anarak schist- marble interlayers. During this metasomatic event, Al, Fe, and Si in the fluid have reacted with Ca in carbonate rocks to form grandite garnet. The first step of garnet growth has been coeval with intrusion of the Kal-e Kafi granitoid into the Anarak schist- marble interlayers. In this period of garnet growth, change in fluid composition may cause the garnet to stop growing temporarily or keep growing but in a much slower rate allowing Al to precipitate rather than Fe. The next step consists of pervasive infiltration of Fe rich fluids and Fe rich grandite garnets formation as the rim of previously formed more Al rich garnets. Oscillatory zoning in the garnet probably reflects an oscillatory change in the fluid composition which may be internally and/or externally controlled. The rare earth elements study of these garnets revealed enrichment in light REEs (LREE) with a maximum at Pr and Nd and a negative to no Eu anomaly. This pattern is resulted from the uptake of REE out of hydrothermal fluids by growing crystals of calcsilicate minerals principally andradite with amounts of LREE controlled by the difference in ionic radius between Ca⁺⁺ and REE³⁺ in garnet x site.     

Formation of kyanite–quartz veins of the Alpe Sponda,Central Alps,Switzerland: implications for Al transport during regional metamorphism

In this study, we have investigated the formation of quartz–kyanite veins of the Alpe Sponda, Central Alps, Switzerland. We have integrated field observations, fluid inclusion and stable isotope data and combined this with numerical geochemical modeling to constrain the chemical processes of aluminum transport and deposition. The estimated P–T conditions of the quartz–kyanite veins, based on conventional geothermometry (garnet–biotite, white mica solvus and quartz–kyanite oxygen isotope thermometry) and fluid inclusion data, are 550 ± 30°C at 5.0 ± 0.5 kbar. Geochemical modeling involved construction of aqueous species predominance diagrams, calculation of kyanite and quartz solubility, and reaction–path simulations. The results of the modeling demonstrate that (1) for the given chemical composition of the vein-forming fluids mixed Al–Si aqueous species are dominant in transporting Al, and that (2) fluid cooling along a small temperature gradient coupled with a pH decrease is able to explain the precipitation of the quartz–kyanite assemblages in the proportions that are observed in the Alpe Sponda veins. We conclude that sufficient amounts of Al can be transported in typical medium- to high-grade regional metamorphic fluids and that immobile behavior of Al is not very likely in advection–dominanted fluid–rock systems in the upper and middle crust.     

Fluid inclusions in coesite-bearing eclogites and jadeite quartzite at Shuanghe, Dabie Shan (China)

Fluid inclusions in coesite‐bearing eclogites and jadeite quartzite at Shuanghe in Dabie Shan, East‐central China, have preserved remnants of early, prograde and/or peak metamorphic fluids, reset during post‐UHP (ultrahigh‐pressure) metamorphic uplift. Inclusions occur in several minerals (e.g. omphacite & epidote), notably as isolated, primary inclusions in quartz included in various host minerals. Two major fluid types have been identified: non‐polar fluid species (N₂ or CO₂) and aqueous, the latter is by far the most predominant. Aqueous fluids cover a wide range of salinity, from halite‐bearing brines to low salinity fluids. For non‐polar fluids, few N₂ inclusions occur in undeformed eclogite, whereas a number of CO₂‐rich inclusions have been found in microshear zones of eclogite or jadeite quartzite in close proximity to marble occurrences. The primary character of N₂ and high‐salinity aqueous inclusions indicates that they are remnants from UHP metamorphic fluids and for some there is the distinct possibility that they are ultimately derived from pre‐metamorphic fluids. This conclusion is supported by the preservation, in some samples, of microdomains containing synchronous inclusions of variable salinities, which tend to relate to the chemical composition of the host crystal. Carbonic fluids may be derived from neighbouring rocks, notably marble and carbonate‐bearing metasediments, during post‐metamorphic uplift. During post‐UHP exhumation, a limited decrease of the fluid density has occurred, with formation of new sets of fluid inclusions. Fluid movements, however, remained exceedingly limited, at the scale of the enclosing crystal.     

Petrology of the Non-mafic UHP Metamorphic Rocks from a Drillhole in the Southern Sulu Orogenic Belt, Eastern-Central China

The Drillhole ZK703 with a depth of 558 m is located in the Donghai area of the southern Sulu ultrahigh-pressure (UHP) metamorphic belt, eastern China, and penetrates typical UHP eclogites and various non-mafic rocks, including peridotite, gneiss, schist and quartzite. Their protoliths include ultramafic, mafic, intermediate, intermediate-acidic, acidic igneous rocks and sediments. These rocks are intimately interlayered, which are meters to millimeters thick with sharp and nontectonic contacts, suggesting in-situ metamorphism under UHP eclogite facies conditions. The following petrologic features indicate that the non-mafic rocks have experienced early-stage UHP metamorphism together with the eclogites: (1) phengite relics in gneisses and schists contain a high content of Si, up to 3.52 p.f.u. (per formula unit), while amphibolite-facies phengites have considerably low Si content (<3.26 p.f.u.); (2) jadeite relics are found in quartzite and jadeitite; (3) various types of symplectitic coronas and pseud     

传统温压计在低温榴辉岩应用中的局限:以西南天山超高压变质带为例

榴辉岩相变质岩石的温压研究对理解高压-超高压变质带的形成和演化具有重要意义,但西南天山低温榴辉岩运用石榴石-绿辉石（-多硅白云母）温压计计算的压力普遍低于相平衡模拟的结果.为此,在Zhang et al.（2017）对含霓辉石榴辉岩研究结果的基础上,对该区域内榴辉岩及其脉体中的绿辉石进行了岩相学和矿物化学的研究,结果表明绿辉石普遍发育环带结构:从核部到边部,Fe3+含量降低,Al含量增加,Fe3+/Al比值的降低对应于霓石含量的降低和硬玉含量的升高.相平衡模拟中硬玉分子等值线的计算结果表明具有最高硬玉含量的边部绿辉石在降压阶段生长.因此,具有最高含量的硬玉组分的绿辉石并不一定代表峰期压力,在应用石榴石-单斜辉石（-多硅白云母）传统温压计时需谨慎,尤其是应用于低温的、具有复杂环带模式的矿物组合时要尤为慎重.      

Fluid evolution during burial and Variscan deformation in the Lower Devonian rocks of the High-Ardenne slate belt (Belgium): sources and causes of high-salinity and C–O–H–N fluids

Fluid inclusions in quartz veins of the High-Ardenne slate belt have preserved remnants of prograde and retrograde metamorphic fluids. These fluids were examined by petrography, microthermometry and Raman analysis to define the chemical and spatial evolution of the fluids that circulated through the metamorphic area of the High-Ardenne slate belt. The earliest fluid type was a mixed aqueous/gaseous fluid (H₂O–NaCl–CO₂–(CH₄–N₂)) occurring in growth zones and as isolated fluid inclusions in both the epizonal and anchizonal part of the metamorphic area. In the central part of the metamorphic area (epizone), in addition to this mixed aqueous/gaseous fluid, primary and isolated fluid inclusions are also filled with a purely gaseous fluid (CO₂–N₂–CH₄). During the Variscan orogeny, the chemical composition of gaseous fluids circulating through the Lower Devonian rocks in the epizonal part of the slate belt, evolved from an earlier CO₂–CH₄–N₂ composition to a later composition enriched in N₂. Finally, a late, Variscan aqueous fluid system with a H₂O–NaCl composition migrated through the Lower Devonian rocks. This latest type of fluid can be observed in and outside the epizonal metamorphic part of the High-Ardenne slate belt. The chemical composition of the fluids throughout the metamorphic area, shows a direct correlation with the metamorphic grade of the host rock. In general, the proportion of non-polar species (i.e. CO₂, CH₄, N₂) with respect to water and the proportion of non-polar species other than CO₂ increase with increasing metamorphic grade within the slate belt. In addition to this spatial evolution of the fluids, the temporal evolution of the gaseous fluids is indicative for a gradual maturation due to metamorphism in the central part of the basin. In addition to the maturity of the metamorphic fluids, the salinity of the aqueous fluids also shows a link with the metamorphic grade of the host-rock. For the earliest and latest fluid inclusions in the anchizonal part of the High-Ardenne slate belt the salinity varies respectively between 0 and 3.5 eq.wt% NaCl and between 0 and 2.7 eq.wt% NaCl, while in the epizonal part the salinity varies between 0.6 and 17 eq.wt% NaCl and between 3 and 10.6 eq.wt% for the earliest and latest aqueous fluid inclusions, respectively. Although high salinity fluids are often attributed to the original sedimentary setting, the increasing salinity of the fluids that circulated through the Lower Devonian rocks in the High-Ardenne slate belt can be directly attributed to regional metamorphism. More specifically the salinity of the primary fluid inclusions is related to hydrolysis reactions of Cl-bearing minerals during prograde metamorphism, while the salinity of the secondary fluid inclusions is rather related to hydration reactions during retrograde metamorphism. The temporal and spatial distribution of the fluids in the High-Ardenne slate belt are indicative for a closed fluid flow system present in the Lower Devonian rocks during burial and Variscan deformation, where fluids were in thermal and chemical equilibrium with the host rock. Such a closed fluid flow system is confirmed by stable isotope study of the veins and their adjacent host rock for which uniform δ¹⁸0 values of both the veins and their host rock demonstrate a rock-buffered fluid flow system.     

基于现代测试技术的钠长石玉矿物组成研究

虽然目前普遍认为钠长石玉的主要矿物组成是钠长石、阳起石、绿泥石、绿帘石、石英等,但仍有待验证.参照行业中对翡翠种的划分,将市场上常见的钠长石玉进行分类,通过偏光显微镜观察、电子探针测试、X射线粉末衍射仪等测试方法对钠长石玉的矿物组成进行了测试与分析,得出钠长石玉的主要组成矿物、次要矿物及副矿物.对一些学术著作中关于钠长石玉的矿物组成钠长石玉中“飘蓝花”品种的致色矿物是绿泥石和绿帘石提出质疑,结果表明,钠长石玉中“飘蓝花”矿物为绿辉石和角闪石.X射线粉末衍射试验的分析表明钠长石的有序度为1或非常接近1,为完全有序或非常接近完全有序的钠长石,说明钠长石玉的形成温度很低.     

"水墨画"种翡翠的矿物学特征研究

"水墨画"种翡翠是市场上出现的翡翠新品种,得名于其黑色不透明物质在无色的"地"上的不规则分布,形似水墨画。本文运用电子探针、X射线粉晶衍射、红外光谱等分析手段对"水墨画"种翡翠进行了研究,结果表明,"水墨画"种翡翠矿物组成以硬玉和绿辉石为主,含有少量的斜长石、磁铁矿及黑色不透明杂质。黑色杂质和磁铁矿为导致该种翡翠产生黑色和不透明的水墨画状外观的主要原因。     

Rutile to Titanite Transformation in Eclogites and its Geochemical Consequences: An Example from the Sumdo Eclogite, Tibet

The formation of titanite coronae after rutile is common in retrograde high-to ultrahigh-pressure meta-mafic rocks, which provides a good opportunity to address the geochemical behavior of HFSE in crustal environments. In the Sumdo eclogite, titanite occurs either as a corona around rutile grains or as semi-continuous veins cross-cutting the major foliation, whereas rutile grains occur either as inclusions in garnet or omphacite or as a relict core surrounded by titanite. Textural relationships ...     

含钠长石翡翠成因探讨

为详细探讨含钠长石翡翠的成因机制,笔者选取了若干来自缅甸的含钠长石翡翠,对其进行了详细的岩相学、矿物化学等方面的研究。含钠长石翡翠样品属于豆青种,主要由硬玉、钠长石、方沸石和少量的多硅白云母、钡铝硅酸盐等矿物组成。其中的硬玉发育清晰的环带结构,成分从核部至边缘发生规律性的成分变化。翡翠同时受到两期后期流体活动的改造,第一期以钠长石为代表,第二期以方沸石为代表,流体的改造作用使硬玉呈现碎裂状、碎斑状结构和交代穿孔等结构。结果表明,含钠长石翡翠样品表现出从成岩流体中直接结晶的特点,该流体富集Na、Al、Si、K、Ba以及少量的Ca、Fe、Mg等元素,微量元素则相对富集LREE、HFSE和sr等元素。结合前人的研究结果以及该玉石中的矿物反应关系,笔者推测缅甸翡翠形成的压力和温度范围分别在6-14kbar和300℃-450℃。