辽宁岫岩玉的岩相结构和无损分析研究

利用外束质子激发X荧光技术（PIXE）、X射线衍射（XRD）、激光Raman光谱（Raman）以及扫描电子显微镜（SEM）等技术对辽宁岫岩玉进行岩石矿物学分析。实验结果表明岫岩玉矿相以叶蛇纹石为主,各种微量元素含量很低。岫岩玉Raman光谱的主要特征峰位于231、378、684、1048、1368和1397cm^-1处。PIXE、XRD和Raman光谱技术作为无损分析方法为鉴定岫岩玉提供了一种快速有效的方法,为研究贵重的古玉器提供了技术支持。     

海泡石相变的粉晶 X 射线衍射研究

摘 要　 利用粉晶 X 射线衍射分析方法‚研究了海泡石在热处理过程中的相变特征。研究发 现‚海泡石在受热后将向滑石转变‚并可分为4个阶段：室温～200℃‚为海泡石相;300～ 700℃‚为向滑石转化的过渡相;800～900℃‚为混合相;900～1000℃‚为顽火辉石相。     

The role of fluids in the metamorphism of komatiites,Agnew nickel deposit,western Australia

The Agnew nickel sulfide deposit is spatially associated with a lenticular body of ultramafic rocks which shows a concentric zonation in metamorphic mineralogy. Olivine + tremolite + chlorite + cummingtonite ±enstatite assemblages occur at the margin of the ultramafic lens, giving way to olivine + anthophyllite, olivine + talc and olivine + antigorite assemblages successively inwards. These rocks are interpreted as having crystallized from komatiitic lavas, and exhibit a spectrum of compositions from those of original flow tops to pure olivine adcumulates. The relative modal abundances of metamorphic olivine, tremolite and chlorite reflect original proportions of cumulus olivine and komatiite liquid in the protolith. Peak metamorphic conditions are estimated at 550° C, based on garnet-biotite thermometry, at a maximum pressure of 3 kb. This temperature falls within the narrow range over which metamorphic olivine may co-exist with enstatite, anthophyllite, talc or antigorite depending upon the fugacity of water in the metamorphic fluid. The observed mineralogical zonation is therefore attributed to infiltration by CO₂-rich fluids, generated by decarbonation of talc-carbonate rocks formed during pre-metamorphic marginal alteration of the ultramafic lens. Metamorphic fluids were essentially binary mixtures of water and CO₂, with minor H₂S having a maximum partial pressure less than 1 percent of total pressure. Enstatite-bearing assemblages formed in the presence of CO₂-rich fluids at fluid: rock volume ratios close to one, while anthophyllite, talc and antigorite bearing assemblages formed in the presence of progressively more water-rich fluids at progressively lower fluid-rock ratios.     

砂岩热物理性质的温度作用效应试验研究

高温作用会导致岩石内部结构发生变化,并对其热物理性质有着显著影响。因此,研究高温作用后岩石热物理性质的变化规律对地热系统及存在热流传播问题的地下工程具有指导意义。试验利用高温炉和Hot Disk热常数分析仪研究了高温作用后砂岩热物理性质的变化特征。研究表明:砂岩的热导率、比热、热扩散率随温度整体呈下降趋势,可分为25℃~100℃,100℃~400℃,400℃~600℃,600℃~900℃四个阶段;25℃~100℃,砂岩热导率、比热、热扩散率因附着水蒸发急剧减小;100℃~400℃,砂岩热导率、热扩散率变化平缓,比热因含水量的降低减小得较快;400℃~600℃,砂岩中结晶水、结构水的蒸发及石英的相变导致微裂隙发育、延伸,进而引起热导率、比热、热扩散率持续下降;600℃~900℃,砂岩中矿物发生分解、熔融破裂,热破裂进一步增加与扩展,这个阶段内热导率、比热迅速下降,但热扩散率基本稳定。     

Constraints on phase diagram topology for the system CaO−MgO−SiO2−CO2−H2O

Published phase diagrams for the siliceous carbonate system CaO–MgO–SiO₂–CO₂–H₂O are contradictory because of different estimates of the relative stability of magnesite. Experimental data on magnesite are too ambiguous to determine the validity of these estimates. Therefore, field evidence is used to select the correct phase diagram topology for siliceous carbonate and carbonate ultramafic rocks at pressures of about 2–5 kbar. The primary selection criterion is provided by the existence of the stable assemblage talc+dolomite+forsterite+tremolite+antigorite, which occurs in the Bergell contact aureole and Swiss Central Alps. Field evidence also is used to argue that the reaction magnesite+quartz=enstatite must occur at lower temperature than the reaction dolomite+quartz=diopside. T-X _{CO 2} and P _{CO 2}-T phase diagrams consistent with these observations are calculated from experimental and thermo-dynamic data. For antigorite ophicarbonate rocks, remarkable agreement is obtained between the spatial distribution of low variance mineral assemblages and the calculated diagrams.     

广西陆川蛇纹石玉的岩相结构及成矿机理

应用外束质子激发X射线荧光光谱法、X射线衍射、激光拉曼光谱、扫描电子显微镜等无损分析技术,对广西陆川蛇纹石玉的成分、物相和结构进行分析。X射线衍射结果显示样品的衍射峰主要位于0.724、0.456、0.362、0.248、0.153和0.150 nm处,表明陆川蛇纹石玉主要矿物成分是蛇纹石,同时伴生方解石矿物与蛇纹石形成穿插交织结构。成矿机理分析表明,陆川蛇纹石玉是由白云质大理岩热液交代作用形成的,和广东的信宜玉均属于富镁碳酸盐型蛇纹石。拉曼光谱显示叶蛇纹石的特征峰位于229、376、457、686和1046 cm-1处,纤蛇纹石的特征峰位于228、345、386、624、690和1102 cm-1处,通过激光拉曼光谱可以快速区分陆川蛇纹石玉中纤蛇纹石和叶蛇纹石两种不同结构的蛇纹石亚种。     

加州软玉和缅甸软玉特征及矿物成分的研究

根据加里福尼亚州的“加州玉“和缅甸“困就“的物理性质、矿物组成、化学成分及红外光谱特征,确定“困就“的主要矿物成分是透闪石,“加州玉“的主要矿物成分为阳起石,两者的宝石名称是软玉.此两玉石较新疆和田、江苏溧阳、辽宁岫岩、俄罗斯贝加尔湖软玉具有较高的Fe、Cr、Ni含量,其矿床类型均为透闪石化或阳起石化超基性岩型.紫外可见吸收光谱特征及化学成分表明:Cr是它们的一个重要致色元素.     

The high-pressure stability of Mg-sursassite in a model hydrous peridotite: a possible mechanism for the deep subduction of significant volumes of H<Subscript>2</Subscript>O

The stability of the high-pressure phase Mg-sursassite, previously MgMgAl-pumpellyite, in ultramafic compositions has been determined in experiments in the system MgO-Al₂O₃-SiO₂-H₂O (MASH). The breakdown of Mg-sursassite + forsterite + enstatite to pyrope + vapour with increasing temperature was bracketed at 6.0 and 7.0 GPa. Below 6.0 GPa, Mg-sursassite + forsterite + vapour reacts to chlorite + enstatite. This reaction provides a mechanism for transfer of water from chlorite- to Mg-sursassite-bearing assemblages. At pressures of 7.0 GPa and above, the assemblage Mg-sursassite + phase A + enstatite was found. Phase relations involving Mg-sursassite and phase A are considered. For bulk compositions with a low water content, the vapour-absent reaction Mg-sursassite + forsterite = pyrope + phase A + enstatite determines the upper-pressure stability of Mg-sursassite, and provides a mechanism for the complete transfer of water from Mg-sursassite to phase A-bearing assemblages. Mg-sursassite plays an important role in peridotite compositions in the subducting slab because, at temperatures below 700 °C, it can transfer water from hydrous phases such as antigorite and chlorite to high-pressure stable phases such as phase A.     

蒙脱石热处理产物的微结构变化研究

本文对广东和平蒙脱石及其热处理产物进行了化学分析、差热和热重分析、X射线粉末衍射分析、红外吸收光谱分析、扫描电镜、原子力显微镜及魔角旋转核磁共振等研究。结果表明,蒙脱石在热处理温度为126℃-148℃时,主要脱出吸附水和层间水,这一脱水过程是可逆的。当热处理温度达到659℃时,蒙脱石八面体片中的羟基开始脱失,但层状结构仍然保持,这种羟基的脱失过程对应着八面体片中Al^Ⅵ向Al^Ⅳ的转变。当温度达到900℃时,蒙脱石的层状结构完全被破坏,并有新的矿物相μ-堇青石产生。当温度为1200℃时,则出现方英石及莫来石相。当热处理温度达到1350℃时,方英石及莫来石的含量略有减少,并出现较多的含铁堇青石相。     

俯冲带蛇纹岩的变质过程

俯冲带蛇纹岩是俯冲带流体的重要来源,特别是其深部脱水作用对地幔动力学影响深远,是研究俯冲带约80~200km深度范围的地球动力学的关键,因此研究蛇纹岩的变质作用过程及其相关特征矿物(组合)的温压稳定范围具有重要意义。蛇纹岩具有简单的矿物(组合):蛇纹石类、硅镁石类、磁铁矿、氢氧镁石、绿泥石、橄榄石、透辉石、角闪石、滑石等,并且这些矿物(组合)对温压变化不敏感从而很难用来判定蛇纹岩所经历的变质演化轨迹。近几十年来,研究者通过实验岩石学和野外地质观察,主要研究了蛇纹石类矿物和硅镁石类矿物的温压稳定范围,并且试图使用这些特征矿物(组合)来判定俯冲带蛇纹岩的峰期变质条件。本文总结了蛇纹岩中这些主要矿物的温压稳定范围和相关变质反应,并且以中国西南天山蛇纹岩为例,展示使用特征矿物(组合)和叶蛇纹石Al等值线判定蛇纹岩峰期温压条件在实际岩石中的应用。另外,早期对叶蛇纹石的研究表明:随着温压条件的变化,叶蛇纹石的晶体结构会发生相应的调整。表现为单位晶胞内硅氧四面体的个数(m值)发生变化:温度升高,m值变小;压力升高,m值变大,这个发现在高压实验和天然样品中得到了一定程度的验证。本文利用已知峰期温压范围的叶蛇纹石样品分别采用粉末制样法和离子减薄制样法,进行透射电镜测试(TEM)样品的m值,并通过统计的方法获得叶蛇纹石的m值的峰值。结果显示叶蛇纹石的m值的峰值在一定程度上可以用以指示温压条件。本文提出可以用矿物组合、叶蛇纹石Al等值线和叶蛇纹石m值峰值相结合的方法确定蛇纹岩的变质温压条件和P-T轨迹。     

甘肃省武山县鸳鸯玉的地球化学和宝石学特征

对甘肃武山县鸳鸯镇鸳鸯玉的地球化学特征和宝石学特征进行的鉴定、分析和研究表明,鸳鸯玉是富镁铁的辉橄岩经岩浆期后多期热液的叠加蚀变(主要为蛇纹石化)形成的蛇纹岩;鸳鸯玉的主要矿物成分为蛇纹石,且多为叶蛇纹石,含有少量的透闪石、滑石、白云石,还有一定量的金属矿物,如磁铁矿、褐铁矿和水镍矿等。该玉石呈较深的灰绿色和墨绿色,质地细腻,可用于制作"夜光杯"和玉碗等工艺品。鸳鸯玉矿区交通方便,矿石开采成本低,是具有良好开发前景的玉石资源。     

The crystal chemistry and thermal stability of sol-gel prepared fluoride-substituted talc

Stable, colloidal sols were prepared from the addition of methanolic (Mg(OCH₃)₂) to one equivalent of H₂O₂ in methanol. Fluoride was quantitatively incorporated by treatment of these sols with HF. Stable sols were obtained when sols, prepared from the acid catalyzed hydrolysis of tetramethylorthosilicate (TMOS), were combined with these fluoridated magnesium sols. Solvent removal gave xerogels, which were calcined, and treated with stoichiometric quantities of water at 750 °C and 1.6 kbar. The resulting products were high-purity, single-phase talcs with fluoride substitution as high as 75 mole percent; the fluoride substitution is higher than any previously reported. Powder XRD analysis showed a non-linear decrease in d(060) spacing with increasing fluoride substitution, which is attributed to a decrease in the b-dimension of talc when fluoride replaced hydroxide. FTIR spectroscopy showed a non-linear decrease in v_O-H in talc with increasing fluoride substitution, which was attributed to an increase in hydrogen bonding of the OH groups and an increase in the electronegativity of the octahedral layer in talc with increasing fluoride substitution. The thermal stability of the talcs was studied using DT and TG, powder XRD, FTIR, and fluoride ion-selective electrode analyses. Synthetic talc without fluoride decomposed at 860 °C, whereas talc with 68% fluoride substitution showed essentially no decomposition when heated to 1060 °C. When heated to 1200 °C, 68% fluoride substituted talc formed amorphous material, enstatite, protoenstatite, norbergite, and chondrodite. The upper stability temperature of talc, taken as the maximum rate of the first endothermic event in its DTA profile, was dependent on the extent of fluoride substitution. Talc with 100% fluoride substitution is predicted to be stable up to ～1100°C.     

Antigorite-ophicarbonates: Contact metamorphism in Valmalenco,Italy

Outside the Bergell tonalite contact aureole, ophicarbonate rocks consist of blocks of antigorite schist embedded in veins of calcite ± tremolite. An antigorite schistosity predates some of these calcite veins. Mono- and bimineralic assemblages occur in reaction zones associated with the veins. Within the aureole, the ophicarbonate veining becomes less distinct and polymineralic assemblages become more frequent. A regular sequence of isobaric univariant assemblages is found, separated by isograds corresponding to isobaric invariant assemblages. In order of increasing grade the invariant assemblages are: antigorite+diopside+olivine+tremolite+calcite antigorite+dolomite+olivine+tremolite+calcite antigorite+olivine+talc+magnesite antigorite+dolomite+olivine+tremolite+talc These assemblages match a previously derived topology in P-T-X_CO2 space for the system CaO-MgO-SiO₂-H₂O-CO₂; the field sequence can be used to adjust the relative locations of calculated invariant points with respect to temperature. Isobaric univariant and invariant assemblages are plotted along a profile map to permit direct comparison with the phase diagram.It is inferred that, during the formation of the ophicarbonate veins, calcite precipitated from fluid introduced into the serpentinite. During contact metamorphism, however, the compositions of pore fluids evolved by reaction in the ophicarbonate rocks were largely buffered by the solid phases. This control occurred on a small scale, because there are local variations in the buffering solid assemblages within a centimeter range.     

High pressure breakdown of antigorite to spinifex-textured olivine and orthopyroxene, SE Spain

The prograde, high pressure, transition from antigorite serpentinite to enstatite-olivine rock occurs along a tectonically undisturbed profile at Cerro del Almirez, SE Spain. The reactant assemblage is antigorite + olivine with tremolite rimming precursor diopside. The product assemblage of tremolite + chlorite + enstatite + olivine has a spinifex-like texture with arborescent or radiating olivine elongated parallel to [001] and with radially grown enstatite. Product enstatite is very poor in Al₂O₃. Due to numerous oriented submicroscopic inclusions of chromian magnetite, product olivine has a brownish pleochroism and a bulk chromium content similar to precursor antigorite. Titanian clinohumite with a fluorine content of 0.45–0.50 wt% persisted beyond the breakdown of antigorite. The partitioning of iron and magnesium amongst the silicate phases is almost identical to that at lower pressures. Average K_d values Mn/Mg and Ni/Mg are 0.17 and 0.70 for antigorite-olivine pairs and 1.83 and 0.22 for orthopyroxene-olivine pairs, respectively. These data are useful in discriminating generations of olivine grown on each other. From the field data a phase diagram topology for a portion of the system CaO-MgO-SiO₂-H₂O is derived. This topology forms the basis for extrapolations into inaccessible P-T regions. Received: 6 February 1998 / Accepted: 24 March 1998     

绿河页岩干酪根分步瞬时热解演化特征及机理研究

分步瞬时热解法可以有效的用于研究干酪根（或其他相关样品）结构组分随温度变化而演变的详细特征。利用分步瞬时热解法从300℃到600℃共分七个温度点,依次对绿河页岩干酪根样品进行热模拟分析。结果表明:在300℃时,绿河页岩干酪根样品基本没有热解产物,在350℃时可检测到少量吸附烃但含量极少;400℃、450℃和500℃是热解产物十分丰富的三个温度点,主要产物是成对出现的正构烷烃和直链烯烃,同时含有一定量的异构烷烃和姥鲛-1-烯;随着热解温度升高,异构烷烃和长链烃类的相对含量逐渐减少;姥鲛-1-烯在400℃和450℃一直占据主要地位;550℃出现了长碳链烷烃（C₂₇~C₃₂）,很有可能是绿河页岩干酪根样品中类似于绿藻等的组分经高温裂解产生的;600℃之后热解产物基本消失,说明在低温阶段干酪根裂解作用就基本完全。另外,绿河页岩干酪根样品在不同温度点的瞬时热解均给出了相应的产物组分构成,对比研究发现,其产物种类及相对含量具有逐渐变化的特征,由此将更有利于研究干酪根的热演化及其成烃机制。     

Minerogenic System of Magnesian Nonmetallic Deposits in Early Proterozoic Mg-rich Carbonate Formations in Eastern Liaoning Province

In the early Proterozoic the Li'eryu Formation and Dashiqiao Formation of eastern Liaoning province, China, there are distributed Mg-rich carbonate rock formations, in which large to superlarge deposits of boron, mag-nesite, talc, Xiuyan jade etc. occur. The formation of these magnesian nonmetallic deposits was related to early Proterozoic evaporates; then these deposits underwent reworking of regional metamorphism and hydrothermal metasomatism during the Luliang orogeny and tectono-magmatism during the Indosinian-Yanshanian. Among other things, the Mg-rich carbonates formations, minerogenetic structures and ore-forming fluids played a controlling role in the formation of the mineral deposits. Therefore, it can be concluded that the mineral deposits are products of combined processes of the coupling of ore source field, fluid field, thermal field (energy field) and stress field under certain time-space conditions in the early Proterozoic and the late-stage superimposed reworking of tectono-magmatism.     

浏阳永和海泡石矿床中海泡石向滑石转变的矿物学研究

在浏阳永和浅海相沉积型海泡石矿床中,海泡石与滑石密切共生,二者或同层出现,或相间出现。即或在单独存在的海泡石矿体和滑石矿体,也属相同时代,相同层位,并伴生同种生物组合。通过X—射线衍射分析、红外光谱分析及电镜分析结果表明,海泡石矿物与滑石矿物之间存在着相互转换的关系,滑石是由海泡石在成岩过程中转化而来的。     

The Metamorphism of the Blue River Ultramafic Body, Cassiar, British Columbia, Canada

The Blue River ultramafic body is an ‘Alpine’-typeperidotite tectonically emplaced within spilitic volcanic rocksin northern British Columbia. The intrusive margins were shearedand serpentinized to a lizardite-chrysotile plus brucite assemblageduring emplacement, prior to thermal metamorphism in the aureoleof a younger batholith. Relatively anhydrous peridotite andhydrous serpentinite were both affected by thermal metamorphism.The body has been subdivided into units defined by the mineralassemblages observed in meta-peridotite and meta-serpentiniteabove and below the isograd for the advent of the mineral talc.Isograds were also established for prograde metamorphic olivine,tremolite, and enstatite. The intrusive was subjected to two metamorphic processes, oxidationand dehydration. The nucleation of metamorphic olivine in weaklymetamorphosed serpentinite was erratic, and turbid porphyroblastcores are enriched in Fe and Mn. The dehydration reaction isthought to have been metastable. Above the talc isograd, serpentine, in both peridotite and serpentinite,reacted with original spinel to form ferritchromit and chlorite.The chlorite becomes progressively more aluminous with increasein grade. The oxidation process inhibited dehydration in meta-peridotiteas a stable chlorite was formed. The process also served toreduce the Fe content of the silicate system, as shown by thecomposition of the olivine generated from excess serpentinein high grade meta-serpentinite.     

An experimental investigation of antigorite dehydration in natural silica-enriched serpentinite

Piston cylinder experiments were performed to constrain the pressure and temperature conditions for two high-pressure antigorite dehydration reactions found in silica-enriched serpentinites from Cerro del Almirez (Nevado–Filábride Complex, Betic Cordillera, southern Spain). At 630–660°C and pressures greater than 1.6 GPa, antigorite first reacts with talc to form orthopyroxene ± chlorite + fluid. We show that orthopyroxene + antigorite is restricted to high-pressure metamorphism of silica-enriched serpentinite. This uncommon assemblage is helpful in constraining metamorphic conditions in cold subduction environments, where antigorite serpentinites have no diagnostic assemblages over a large pressure and temperature range. The second dehydration reaction leads to the breakdown of antigorite to olivine + orthopyroxene + chlorite + fluid. The maximum stability of antigorite is found at 680°C at 1.9 GPa, which also corresponds to the maximum pressure limit for tremolite coexisting with olivine + orthopyroxene. The high aluminium (3.70 wt% Al₂O₃) and chromium contents (0.59 wt% Cr₂O₃) of antigorite in the investigated starting material is responsible for the expansion of the serpentinite stability to 60–70°C higher temperatures at 1.8 GPa than the antigorite stability calculated in the Al-free system. The antigorite from our study has the highest Al–Cr contents among all experimental studies and therefore likely constraints the maximum stability of antigorite in natural systems. Comparison of experimental results with olivine–orthopyroxene–chlorite–tremolite assemblages outcropping in Cerro del Almirez indicates that peak metamorphic conditions were 680–710°C and 1.6–1.9 GPa.     

高温高压岩石流变仪的围压标定方法

高温高压岩石流变仪围压标定的主要方法为氯化盐类的部分熔融法和矿物相变法。利用氯化盐类进行压力标定时,不仅可以利用单一盐类,也可以使用多种盐类的混合物;常用的压力标定矿物相变及其适用温压范围如下:石英-柯石英,500~1200℃、2.5~3.2GPa;钠长石-硬玉+石英,600~1200℃、1.6~3.2GPa;铁橄榄石+石英-铁辉石,600~1200℃、1~1.7GPa;磷镁石-Mg3(PO4)2-Ⅱ,565~825℃、0.6~0.9GPa;方解石-文石,600~1200℃、0.5~2.5GPa。不同的标定方法具有不同的特征,文中将进行详细介绍。