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1.
榴辉岩中石英出溶体的拉曼光谱学研究及其构造意义 总被引：2，自引：0，他引：2
利用拉曼光谱学和费氏台方法对若干地区超高压榴辉岩中柯石英和榴辉岩中石英出溶体的超显微构造特征进行了研究.研究结果表明, 石榴石(或绿辉石) 中柯石英向石英相变是一个连续变化过程.绿辉石中石英出溶体和主晶具有一定的晶体学拓扑关系, 即石英出溶体长轴有两个展布方向: 平行于绿辉石(10 0) 裂理面和平行于绿辉石(- 10 1) 面.目前, 部分学者推断榴辉岩绿辉石中石英出溶体可作为超高压变质作用的标志.笔者认为, 棒状定向石英在绿辉石中出溶的温压条件和出溶机理尚未查明.因此, 需加强过量二氧化硅单斜辉石出溶机理的超高压实验研究, 从而为证实石英出溶体作为超高压标志提供实验定量约束. 相似文献
2.
钛磁铁矿内部尖晶石出溶体的成分组成和形成机制对估算磁铁矿固溶体的成分以计算铁钛氧化物的氧逸度-温度具有重要意义.为了探究攀枝花钒钛磁铁矿中尖晶石的成因及形成机制,运用岩相观察和各种微区原位观测手段,系统研究了各类尖晶石的矿物学特征.尖晶石的粒度在纳微米之间,有3种类型:第1种为钛磁铁矿晶界处不规则的大颗粒尖晶石,Mg#为60~70;第2种为钛磁铁矿颗粒内部的粒状尖晶石,Mg#为71~77;第3种为沿钛磁铁矿（100）方向定向分布的尖晶石片晶,Mg#为75~77.3类尖晶石分别与磁铁矿主晶具有相同的取向关系:{111}Mag//{111}Spl,{110}Mag//{110}Spl和{100}Mag//{100}Spl.3类尖晶石均是磁铁矿主晶的出溶体,钛磁铁矿晶界处及其内部的粒状尖晶石的形成与某些晶体缺陷关系密切,是在降温过程中较早出溶的产物,尖晶石片晶在两者之后以旋节分解出溶形成. 相似文献
3.
WangLu JinZhenmin HeMouchun 《中国地质大学学报(英文版)》2003,14(2):119-126
The studies on ultra-microstructue characteristics of quartz exsolution in eclogite and coesite in UHP eclogite of several localities are done with the appliance of laser Raman spectroscopy and Ustage. Research results show that the phase transformation of coesite-quartz in garnet and/or omphacite is a continuous process. Topological relationship is present between quartz exsolution in omphacite and its host mineral which shows orientations of two long axes of quartz exsolution parallel to (100) and (-101) of omphacite. At present, some scholars suggest that thequartz exsolution in omphacite of eclogite is the evidence of UHP metamorphism. However, temperature and pressure condition and the exsolution mechanism of oriented needlelike quartz in omphacite still remain undear. Tnerefore, further study should be enhanced on experimental research on exsolution mechanism of super-silicate clinopyroxene, which could provide experimental quantitative constraint on quartz exsolution as UHP indicator. 相似文献
4.
Four different types of pyroxene found in a Beaver Bay ferrogabbro were analysed by microprobe. The crystallization sequence of pyroxene is augite-ferroaugite with exsolution lamellae of Ca-poor clinopyroxene → ferropigeonite with exsolution lamellae of augite → ferrohypersthene without exsolution lamellae+augite and ferroaugite without exsolution lamellae. The core of augite-ferroaugite with exsolution lamellae is cumulus pyroxene, whereas others, including the margin of augite-ferroaugite with lamellae, are interpreted to have crystallized from the intercumulus liquid. The sequence of crystallization of minerals from intercumulus liquid is different from that of minerals which have accumulated successively to the bottom and which were related to the fractionation of the whole layered series. The difference may be attributed to the different oxidation state of crystallization. 相似文献
5.
Exsolution and coarsening in Fe-free clinopyroxene of composition En45.1Di54.9 was studied at temperatures of 1300, 1200, and 1100°C, and annealing times between 10 min and 4320 h. Based on the wavelength of the exsolution lamellae, the exsolution process can be divided into exsolution sensu stricto and coarsening. During exsolution sensu stricto, the average wavelength of the “001” and “100” lamellae remains constant in contrast to the subsequent coarsening process. A progressive development of the microstructure is observed before coarsening which includes formation of island-like regions of dark contrast without phase separation, occurrence of pigeonite and diopside domains predominantly elongated along (100), formation of “100” exsolution lamellae, dissolution of the “100” lamellae, and predominant occurrence of “001” exsolution lamellae. All observations are in accordance with the exsolution mechanism of spinodal decomposition. After termination of the exsolution process, coarsening of the exsolution lamellae is observed. The “001” lamellae coarsen according to the rate law
6.
桐庐、黄山花岗岩类岩体中碱性长石的出溶和超微双晶 总被引：1，自引：0，他引：1
本文研究了桐庐和黄山两地不同成因花岗岩类岩体中碱性长石的出溶和超微双晶。结果表明,碱性长石的出溶和超微双晶同岩体的成岩温度、冷却速率以及岩体成因类型和碱性长石的化学成份有关,成岩期后的热作用对碱性长石的出溶和超微双晶产生改造和破坏。 相似文献
7.
Monoclinic calcium-poor shear-transformation lamellae and calcium-rich exsolution lamellae occur parallel to (100) in orthopyroxene. The formation of both structures from an orthopyroxene host involves a shear on (100) parallel to [001], with additional cation exchange in the exsolution case. The shear transformation involves a macroscopic simple shear angle of 13.3° (shear strain of 0.236) and produces a specific a-axis orientation with respect to the sense of shear; we have found that this orientation dominates in exsolution lamellae in kinked orthopyroxene, where the sense of shear is known. In undeformed orthopyroxene, there is generally no preferred sense of orientation of the monoclinic a axes. We advance a specific model for exsolution involving nucleation and growth by shear transformation combined with cation exchange, thus circumventing the classical nucleation barrier and permitting exsolution at lower solute supersaturations. 相似文献
8.
西藏羌塘地区榴辉岩石榴子石和磷灰石中均发育矿物出溶体,结合电子探针和扫描电镜分析及能谱分析,确定了石榴子石中的出溶体有金红石、石英和角闪石,指示其可能经历了高压/超高压变质作用。本研究在磷灰石中发现了金红石出溶,并认为其可能是在高压/超高压条件下元素相互置换的结果,置换方式为Ti~(4+)(Fe~(2+)、Si~(4+))=2Ca~(2+),这些出溶体的形成为榴辉岩曾经历高压/超高压变质作用提供了矿物学证据。 相似文献
9.
通过组成－自由能关系曲线的分析，提出斜方顽火辉石－正铁辉石（MgSiO3-FeSiO3)固溶体出溶的临界温度约为753K；组成XFe为0.82左右的富铁辉石固溶体处于介稳态，出溶作用有利于系统自由能降低；出溶作用是以Fe^2 、Mg^2 离子逆扩散的方式进行的；出溶作用的推动力是上凸区域介稳相与平衡相之间的化学位差。 相似文献
10.
镍铜硫化物矿石中磁黄铁矿固溶体的退火及其选矿意义 总被引：3，自引：0，他引：3
磁黄铁矿固治体从硫化物熔体结晶后，在缓慢冷却过程中经历了显著的退火。出治和出治体的租化是固治体退火的两种方式。叶片状的单斜磁黄铁矿和“火焰状”的镍黄铁矿原始出治相在降温过程中均可发生退火和租化。分布于磁黄铁矿等矿物粒间或包于磁黄铁矿粒内的粒状镍黄铁矿，不只是高温出治的直接产物，有一部分可能是由火焰状出治体租化而成的。磁黄铁矿中单斜变体的出治和租化可使矿石的磁性发生改变，镍黄铁矿出治体的租化使含镍矿物的粒度加大。因而，退火作用对矿石的选矿工艺性能有着显著影响。 相似文献
11.
M. W. Wegner R. E. Jones J. M. Christie 《Contributions to Mineralogy and Petrology》1978,65(3):283-291
A new chemical etching technique reveals fine scale exsolution structures on polished surfaces of plagioclases in the bytownite and labradorite range. A very obvious blue and locally brown stain is produced (by the action of citric acid) in growth zones of a restricted range of compositions on etched surfaces. The blue-stained zones contain very fine grooves, corresponding to the traces of thin exsolution lamellae. Exsolution features have been revealed in this way in plagioclases in a terrestrial diabase, lunar basalts and an amphibolite. Compositions of the exsolved areas found by microprobe analysis represent averages of the matrix and exsolution lamellae. Analytical methods with higher spatial resolution are required to determine the composition of the lamellae. This etching method permits easy optical identification of compositional zoning and of fine scale exsolution over relatively large areas and is therefore complementary to other techniques. 相似文献
12.
The microtextures developed during relatively slow cooling as a function of bulk composition in zoned ternary feldspars from syenodiorites and syenites in the Klokken intrusion, described in the preceding paper, were determined by TEM and their origin and evolution deduced. The feldspars normally have a plagioclase core and an alkali feldspar rim; cores become smaller and rims larger and the An content of both decrease with distance from the contact of the intrusion. The following microtextural sequence was observed. The inner plagioclase cores are homogeneous oligoclase-andesine with Albite growth twins only, but are crypto-antiperthitic towards the outer core. At first small platelets of low sanidine a few nanometres thick and up to 10 nm long occur sporadically only on Albite-twin composition planes. With further increase in bulk Or they are homogeneously distributed in the plagioclase. Thicker, through-going plates in platelet-free areas are found, which induce Albite twins in the surrounding plagioclase. The microtextures in the rims are regular cryptomesoperthitic, with (¯601) lenses or lamellae, depending on the bulk Or-content, of low sanidine in Albite-twinned low oligoclase-andesine. Albite and Pericline twins in plagioclase in an M-twin relationship, together with lenticular low sanidine, were found in only one small area. The overall diffraction symmetry of the mesoperthites is monoclinic, showing that exsolution started in a monoclinic feldspar, whereas that of the antiperthites is triclinic. The intermediate zone between the core and rim is more complex and microtextures vary over distances of a few micrometres.The cryptomesoperthites are very regular where Or-rich and probably arose by spinodal decomposition. The platelets in the outer cores arose by heterogeneous nucleation on twin composition planes and by homogeneous nucleation elsewhere. Near the intermediate zone they coarsened to give larger plates which induced Albite-twins in the plagioclase. Because of the zoning, microtextures that were initiated in areas of given composition, can propagate laterally into zones of different composition. A diagram is given showing the relationship between ternary bulk composition and the microtexture developed in coherent perthitic alkali feldspars and plagioclases from slowly-cooled rocks.CRPG contribution 730 相似文献
13.
An electron microscopic study of the twinning and exsolution textures in one hydrothermal and two pegmatitic amazonites from southern Norway is reported. From observations of three types of interfaces: between twins, between domains twinned on different laws and between Na- and K-feldspar domains, perthitic textures involving low albite lenses up to 10 μm long in a twinned microcline matrix are shown to result from exsolution from the triclinic phase. Complex twinning on albite and pericline laws is suggested to be the result of strains induced by exsolution. Other textures, involving the late introduction of Na at low temperature in a pegmatite and the occurrence of Pb-rich and plagioclase crystallites in a hydrothermal amazonite, are described. 相似文献
14.
15.
The Discovery of Phlogopite Exsolution Lamellae in Garnets of Eclogite Inclusions, Liaoning Province
Zhou Xiuzhong Institute of Mineral Deposits Chinese Academy of Geological Sciences Beijing Liu Xinzhu 《《地质学报》英文版》1997,71(1):33-42
In No. 50 kimberlite pipe of Fuxian County, Liaoning Province, an eclogite inclusion(nodule), which is extremely rare in kimberlites, was discovered and phlogopite exsolutionlamellae were found in garnets of the inclusion. Microscopic, TEM and energy spectral observa-tions and studies confirmed that these lamellae are phlogopite. They are colourless and acicularin section, generally 0.5-5μm in width and 10-100μm in length. Nevertheless, fine lamellae,0.05-0.1μm wide and 1-2μm long, are also well developed. Along [111] of the garnet, three setsof phlogopite lamellae show oriented arrangement approximately at angles of 60°-70°, indi-cating that these lamellae might be the product of exsolution from garnet as a result ofpressure-release when eclogite ascended from the relatively deep level to the relatively shallowlevel of the mantle. Tiny acicular exsolution minerals (or inclusions) are commonly found ingarnet and pyroxene in eclogite inclusions of kimberlites all over the world and it has been re-ported that the identified exsolution minerals include pyroxene and rutile. This is the first timethat phlogopite exsolution lamillae were found in eclogite inclusions in the world. 相似文献
16.
本文用电子背散射衍射技术(electron backscatter diffraction,EBSD)测试了海南文昌玄武岩中二辉橄榄岩包体中的辉石主晶与其出溶片晶的结晶学取向关系。结合电子探针成分测试,得出:单斜辉石(透辉石)主晶中出溶了两组不同方向的片晶,一组为斜方辉石(顽火辉石-易变辉石)片晶,另一组为单斜辉石(普通辉石)片晶。由于出溶片晶在EBSD测试切面上体现为以线状体,因此需要找到一种方法将线状体所代表的片晶的晶面符号推算出来。本文介绍了一种利用吴氏网进行坐标系旋转的"晶带相交法",该方法可以作图推算出溶片晶的晶面符号。根据"晶带相交法"得出,斜方辉石(顽火辉石-易变辉石)出溶片晶为(100),单斜辉石(普通辉石)出溶片晶为~(401)。根据前人的研究资料,出溶片晶~(401)可能指示最小出溶压力为9.5~12.5GPa。出溶片晶的结晶学取向涉及到主晶与出溶体的晶体结构匹配关系,并且与出溶温度-压力有关,因此出溶片晶的结晶学取向分析具有晶体化学理论意义和反映地质温压过程的实际意义。这种"晶带相交法"可以推广应用于其他矿物出溶结构的结晶学取向研究中。 相似文献
17.
Relict Majoritic Garnet Microstructures from Ultra-Deep Orogenic Peridotites in Western Norway 总被引：9，自引：1，他引：9
VAN ROERMUND H. L. M.; DRURY M. R.; BARNHOORN A.; DE RONDE A. 《Journal of Petrology》2001,42(1):117-130
Protogranular, porphyroclastic and equigranular (or equant-polygonal)garnet microstructures from Mg–Cr type orogenic garnetperidotites, Otrøy, Western Gneiss Region, Norway, havebeen studied using naked eye, light-optical, electron-opticaland confocal laser (fluorescence) microscopy techniques. Protogranularand porphyroclastic garnets contain microstructural evidencefor the former existence of majoritic (or super-silicic) garnet.The microstructural evidence consists of exsolution texturesinvolving pyroxene. Two types of exsolution microstructuresoccur—needles parallel to <111>grt and interstitialgrains. The maximum volume percentage for intra-crystallinepyroxene exsolution is 2·7, and 3·6 for inter-crystallinepyroxene exsolution. The maximum pyroxene total volume percentagemeasured in one single protogranular or porphyroclastic garnetis 4·0. This value, at 1200°C, corresponds to minimumpressures of 6·4 GPa ( 相似文献
18.
徐淮地区镁铁质岩石捕虏体单斜辉石中石榴石和石英的出溶 总被引：7，自引：0，他引：7
徐淮地区早侏罗世侵入杂岩中榴辉岩,石榴辉石岩和单斜辉石岩捕虏体单斜辉石中可以观察丰富的出溶石英针和石榴石,黝帘石及角闪石的出溶叶片,榴辉岩中出溶石英针的绿辉石核部比其边部相对富含FeO和MgO,贫SiO2,Al2O3和CaO。在石榴辉石岩和单斜辉石岩捕虏体中具有出溶石榴石的单斜辉石。从靠近出溶石榴石的一侧向其核部,Al2O3,Na2O和TiO2含量降低,MgO,SiO2和CaO含量增加,单斜辉石中定向石英针的出溶表明曾经存在有超高压条件下（≥25×10^8Pa)稳定的过硅质绿辉石。单斜辉石中出溶石榴石表明温压条件的降低可能是引起出溶的一个主要原因,捕虏体中的矿物组合和岩相学特征表明它们曾经遭受了榴辉岩相和角闪岩相退化变质作用,这与因压力和温度降低引起矿物出溶的结果相吻合。 相似文献
19.
Michael A. Carpenter 《Contributions to Mineralogy and Petrology》1980,71(3):289-300
The free energy curves for simple binary solid solutions with limited miscibility or atomic ordering have been combined to
predict the phase relations and exsolution mechanisms for a system in which both ordering and exsolution are possible. The
nature of the ordering process affects which exsolution mechanisms may be used. If the ordering is second (or higher) order
in character then continuous mechanisms predominate and a ‘conditional spinodal’ (Alien and Cahn, 1976) can be described which
operates between ordered and disordered end members. For a first order case, the ordered phase can only precipitate a disordered
phase by nucleation and growth.
Microstructures in omphacites observed by transmission electron microscopy include exsolution lamellae and antiphase domains
and the relations between them in selected specimens have been used to interpret the exsolution mechanisms which operated
under geological conditions. It appears that most omphacites undergo cation ordering, and then remain homogeneous or exsolve
a disordered pyroxene by spinodal decomposition. The predominance of continuous mechanisms has been used to indicate that
the C2/c→P2/n transformation may be second (or higher) order in character.
A possible phase diagram for jadeite-augite is presented. It is based on the idea that there should be limited miscibility
between the disordered end members at low temperatures and that the cation ordering at intermediate compositions (omphacite)
is superimposed on a solvus. It is adequate to explain many of the observed microstructures and fits with petrographic evidence
of broad two phase fields between impure jadeite and omphacite and between omphacite and sodic augite. The effect of adding
acmite is analogous to increasing temperature so that the phase relations for jadeite-acmite-augite can also be predicted. 相似文献
20.
Pyroxenes of pigeonitic and augitic bulk compositions in H3–4 chondritic meteorites commonly exhibit sigmoidal precipitates, rather than the elsewhere common lamellar associations. Most often, submicrometric sigmoids with calcic clinopyroxene composition occur within clinoenstatite; more rarely, clinoenstatite sigmoids occur within calcic clinopyroxene. The sigmoids appear as 001 terminated lamellae, with terminations rotated in opposite directions towards the 100 orientation. Pre-exsolution pigeonite and augite formed at temperatures higher than 980 °C, whereas sigmoidal exsolution occurred between 990 and 830 °C. Local anomalous lattice parameters determined by electron diffraction suggest that lattice parameters are most strained where the exsolution texture is most poorly defined. Shear strain occurs during exsolution due to mismatching lattice parameters and variable angles. In response to shear stress, the lamellae relax and assume sigmoidal strained morphologies. Sigmoidal exsolution is strongly controlled by (100) orthoenstatite stacking faults that possibly trigger exsolution. 相似文献