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宁强碳质球粒陨石的球粒和基质中存在大量圆形的不透明矿物集合体. 其中的主要矿物为富镍金属、磁铁矿和铁镍硫化物, 另有少量磷酸盐、富磷橄榄石、辉石及微量的铂族金属颗粒. 这种矿物组合与难熔包体中的不透明矿物集合体非常相似, 因此, 它们具有相似的成因机制. 富磷橄榄石是自然界十分罕见的矿物相, 它是液态含磷金属与橄榄石晶体之间在快速冷却过程中发生非平衡反应的产物. 富磷橄榄石出现在不透明矿物集合体, 说明不透明矿物集合体的金属前身是从组成球粒的硅酸盐熔体中出溶结晶而成, 而不是直接从星云中凝聚而成. 宁强陨石中不透明矿物集合体的矿物岩石学特征表明, 不透明矿物集合体是由内生的均匀金属在陨石母体上受到低温水蚀变作用形成的. 相似文献
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橄榄石和辉石以及它们的高压相是地幔转换带主要矿物,系统研究橄榄石和辉石在转换带底部温度和压力条件下相变的差异是认识660km地震不连续面位置和形态的关键．本文使用多面砧压机开展了橄榄石和顽火辉石在压力为21．3～24．4GPa,温度为1600℃的相变实验研究．地幔转换带底部,橄榄石和顽火辉石相变主要的差异在于钙钛矿出现的压力不同．在橄榄石体系中,后尖晶石相分解发生在23．8GPa,与660km不连续面具有很好的对应关系;而在顽火辉石体系中,钙钛矿出现的压力小于23GPa．研究结果表明,橄榄石后尖晶石相变与辉石中钙钛矿的出现之间有约0．5—1GPa压力差．因此,在受大洋俯冲带影响地区（例如中国东部）,辉石体系中发生的秋本石（钛铁矿）．钙钛矿的相变能够合理解释660km地震不连续面向上的起伏或分裂． 相似文献
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橄榄石矿物弹性研究进展 总被引：1，自引：0，他引：1
橄榄石是上地幔含量最丰富的矿物,对其弹性性质的研究对解释地球内部的物质组成和动力学过程至关重要.近年来,对橄榄石矿物弹性的研究,无论是实验测试还是模拟计算都取得了很大的进展.本文首先介绍了研究橄榄石弹性的主要方法,然后从铁、镁不同配分比例下橄榄石的弹性性质,水对橄榄石弹性的影响以及橄榄石各向异性等三个方面,对近年来橄榄石弹性研究所取得的主要进展做了介绍.实验方法方面主要介绍了1)超声共振谱法(Resonant Ultrasound Spectroscopy,RUS);2)X射线衍射法;3)X射线照相法;4)超声干涉法;5)布里渊散射法. 相似文献
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微量元素在尖晶石相和石榴石相橄榄岩中的分布 总被引：6，自引：2，他引：4
根据我国东部两个尖晶石相和石榴石相橄榄岩全岩及主要造岩矿物的微量元素组成,探讨了微量元素在不同深度上地慢的分布特征．得到的数据支持大部分强不相容元素（Ｒｂ,Ｂａ,Ｔｈ,Ｕ,Ｓｒ,Ｎｂ,Ｔａ）主要存在于粒间组分和流体包裹体中的观点;流体包裹体对橄榄石和斜方辉石的ＬＩＬＥ组成影响很大,以致不能用固相矿物之间的分配系数来推导ＬＩＬＥ的矿物／熔体分配系数．尖晶石相和石榴石相橄榄岩中的（Ｏｐｘ／Ｃｐｘ）_ＨＲＥＥ有很大的差别,暗示Ｐ－Ｔ条件对平衡分配系数的控制． 相似文献
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上地幔橄榄岩流变性研究新进展及其地球动力学意义 总被引：2，自引：1，他引：2
本文系深部地幔流性研究进展综述文章之一，重点介绍了近年来国际地球物理学界在涉及橄榄岩上地幔流变性的下述三方面取得的进展：（１）化学环境因素对橄榄石高温塑性的影响；（２）高温高压下水在橄榄石晶体中的溶解度和赋存状态；（３）橄榄石多晶体的变形机制转变，并对由此得出的地球动力学意义作了讨论。 相似文献
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氢能够显著地影响岩石的物理性质,如岩石的流变等.它能赋存于通常不含水的矿物中,如上地幔的橄榄石.为了解上地幔的物理性质和地球化学过程,测量氢在橄榄石中的溶解度是非常重要的.在 相似文献
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Olivine crystals in mare basalts 12004,8 and 12022,12 are normally zoned with Cr-poor rims. The Ni content of rare 2–10-μm metal inclusions in olivine decreases markedly as Fe/Mg in their immediate olivine hosts increases. Each metal grain appears to have been enclosed by late olivine almost immediately after it crystallized. The fractionation trend for the olivine and metal contrasts with the subsolidus equilibration trend for pallasites. For the basalts, not even local equilibration of Fe, Ni and Co at metal/olivine interfaces can be detected by microprobe. Ni and Co concentrations range from about 300 ppm in olivine cores to about 70 ppm in rims. The limits of detection, at 95% confidence, are 36 ppm (Ni) and 25 ppm (Co). The distribution of Ni and Co in olivine, like that of Mg and Cr, records the depletion of these elements in the melt.Fractional solidification models, using the Ni and Co concentrations of the whole rock, and Ni and Co concentrations of the earliest formed olivine, metal and “opaques” as initial compositions, allow metal and olivine compositions to be predicted if the order of crystallization is known. Conversely the order of crystallization can be established if known olivine and metal compositions are reproduced. Calculated Ni and Co contents for metal and olivine in these basalts correspond to observed concentrations only where metal precipitation is delayed until the liquid has crystallized 4–5 wt.% olivine. 相似文献
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Christian Desnoyers 《Earth and Planetary Science Letters》1980,47(2):223-234
The origin of olivine grains in C2 carbonaceous chondrites is a controversial topic: directly condensed material or detrital remnants of preexisting chondrules? This study shows that the Niger C2 meteorite is similar to Murchison but reveals several interesting features in relation to the origin of the olivine. Microprobe analysis of olivine (Si, Fe, Mg, Ca, Mn, Cr), glass and nickel-iron inclusions within the grains, and Fe-S-O phase as well as the relationships between the olivine grains in the aggregates, between the grains and the interstitial phyllosilicate matrix, between the inclusions and their host olivine grains, and the morphology of some aggregates all show that two populations of olivine coexist, probably crystallized from chondrule melts rather than by direct condensation from a solar nebula gas. The characteristics of the nickel-iron inclusions within the olivine suggest a magmatic chondrule-making stage from previously condensed materials. 相似文献
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The axial ratio of basalt pillows in some shallow water pillow lava sequences from Azores and Iceland, is defined as V/H, where V and H represent the vertical and horizontal axes in cross section perpendicular to the elongate direction of undisturbed pillows. The axial ratios show a great spread of overlapping values for pillows from different sequences. However, alkaline olivine basaltic pillows tend to be more flattened than the olivine tholeiitic pillows. Another, and probably more discriminative feature between the two, is the difference in the maximum size of V and H of a pillow body. The limit for V and H for alkaline olivine basalt pillows is significantly lower than that of the olivine tholeiite pillows. A lower viscosity for alkaline olivine basalt than for olivine tholeiite probably accounts for the differences. 相似文献
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R. Ostertag G. Amthauer H. Rager H.Y. McSween 《Earth and Planetary Science Letters》1984,67(2):162-166
ALHA 77005, a shocked achondrite of the shergottite group, is unique in containing cumulus olivine crystals which display a brownish color in thin section. Mössbauer, EPR, and optical spectroscopic studies show the presence of Fe3+ in the olivine. Approximately 4.5 wt.% of the total iron in the olivine (24 wt.% as FeO) is in the trivalent state. The Fe3+ ions preferentially occupy M2 lattice positions. Charge transfer between Fe3+ and Fe2+ as well as between Fe3+ and oxygen ligands causes a broad absorption band in the optical spectrum at high energies which is the reason for the olivine color. It is concluded that the color of the ALHA 77005 olivine is preterrestrial and may be the result of shock-induced oxidation of the olivine crystals on the meteorite parent body. 相似文献
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In the Late Cenozoic West Carpatian alkali olivine basalts spinel peridotite xenoliths have been found. Their mineral composition corresponds to those found in this type of xenoliths in alkali basalts throughout the world (Mg-rich olivine, Cr-diopside, clinopyroxene, spinel). For the studied West Carpathian alkali olivine basalts kaersutite amphibole and clinopyroxene magacrysts are characteristic. The presence of the xenoliths under consideration in the boundary zone between Tatra and Pannonian blocks is the consequence of tectonic conditions (thickness of the Crust) in the area mentioned as distinct from the other West Carpathian areas of alkali olivine basalt occurrences. 相似文献
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本文研究了橄榄石原位相变实验中加载、加热路径上的相变及其对确定相变动力学参数的影响.利用文献［1］所给出的退火后先加温后加压,且相对低温条件下实验结果确定出的Ni2SiO4橄榄石相变动力学参数,计算了加载、加热路径上所发生的相变对确定成核率、长大率及相变体积分数的影响.结果表明,退火后先加压后加温,且相对高温条件下的实验数据受到加热路径上成核的影响.根据这样的实验数据得到的成核率会明显高于实际温压条件下的成核率.尤其是当多数实验都是高温实验时,根据这些成核率数据所确定的成核率参数会严重偏离其真值,从而严重影响对俯冲带颗粒粒度及俯冲带流变结构的计算.尽管目前有很多关于Mg2SiO4橄榄石长大率的实验数据,也有通过对挤碰物理图像的分析对(Mg0.89Fe0.11)2SiO4橄榄石成核率的估算,但只有文献［2］通过退火后先加压后加温的原位实验得到了Mg2SiO4橄榄石的相变成核率,且属于高温实验.根据本文的研究结果,我们认为亟需补充退火后先加温后加压或相对低温的实验数据以得到正确的地幔橄榄石成核率参数. 相似文献