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I. V. Belyatinskaya V. I. Feldman V. V. Milyavsky T. I. Borodina G. E. Valyano A. A. Belyakov 《Moscow University Geology Bulletin》2010,65(5):289-300
In this work the patterns of shock-metamorphic transformations of rock-forming minerals (amphibole, plagioclase, and clinopyroxene)
in layered crystalline schists (Southern Ural) appeared as a result of planar shockwave loading of rocks. Comparison of the
data obtained with those of diaplect transformations of the above-listed minerals in the field and as a result of experiments
with convergent spherical shockwaves for this rock revealed essential differences between transformations. The formation of
polymineral shock-thermal apoamphibole and apoclinopyroxene aggregates that were typical for the conditions of spherical shockwave
compression was not observed during stage shockwave compression, even at 52 GPa. 相似文献
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The paper presents a concise review of results obtained by studying shock metamorphism of polymineralic rocks with the application of spherical hermetically sealed recovery devices. Such experiments are proved to be able to reproduce principally important features of transformations detected in rocks from natural meteoritic craters (astroblemes). The experimental samples show subspherical concentric zones with different rock transformations, which are generally analogous to zones in natural astroblemes (listed in order from the centers of the spherical samples to their margins): fracturing, diaplectic transformations, selective and then complete melting, and finally, evaporation. However, the laboratory scale of the experiments and the absence of younger overprinted processes, which can obliterate impact transformations of rocks in nature, enable the researcher to reveal distinctive compositional, textural, and phase features of transformations induced in the rocks at increasing isentropic shock wave-induced loading. Data on the mobility of major elements in the course of impact metamorphism show that the type and certain features of the crystal structures of minerals are of paramount importance for the amorphization of the minerals or their shock wave-induced thermal decomposition. The crystal chemical control of mineral transformations was proved to be exerted at a number of levels. High-pressure phases identified in experiments with shock wave loading were determined to crystallize from melt or via a phase transition associated with the migration of elements. 相似文献
4.
I. V. Belyatinskaya V. I. Fel’dman V. V. Milyavsky T. I. Borodina A. A. Belyakov 《Moscow University Geology Bulletin》2012,67(1):30-42
Patterns in the shock metamorphic transformations of rock-forming minerals (garnet, biotite, plagioclase, and K-feldspar)
in quartz-feldspar-biotite-garnet schist (the Southern Urals) that were subjected to shockwave compression using planar geometry
recovery ampoules were investigated. The maximum shock pressures that were attained upon a few wave circulations in a sample
(stepwise shock compression) reached 26, 36, and 52 GPa. Comparison of the transformations that occurred due to stepwise shock
compression with diaplectic changes of the studied minerals in nature and in the course of experiments with convergent spherical
shock waves revealed significant differences in the transformations of melanocratic (garnet and biotite) minerals under different
types of loading. 相似文献
5.
The mineralogy and petrology of pumice exposed in two small outcrops at the top of two hills in western Spain suggest that these rocks are of impact genesis. Ringwoodite, which was identified in the rocks, can crystallize from melt under pressures of 10?C11 GPa in static regime or at the relief of pressure of a shock wave under pressures of 15?C17 GPa and more. The other minerals crystallizing from the melt at a pressure decrease are ferrous hortonolite (unit cell parameters of ringwoodite and hortonolite are reported), minerals belonging to the spinel group and having variable Fe mole fractions, clinopyroxene, orthopyroxene, anorthite, and corundum. Hollow, skeleton, dendritic, and whisker crystals of these minerals suggest that they crystallized at the cooling and strong undercooling of the melt. The crystallization temperature of the hercynite is 1780°C. The temperature of the melt that produced the pumice is estimated at 1900?C2700°C. Our find of ringwoodite is the first discovery of this mineral in natural impact rocks. 相似文献
6.
The analysis of available theoretical evaluations and experimental data reveals discrepancies and makes it possible to formulate the goals for the comprehensive study of the behavior of enstatite MgSiO3 in shock isentropic waves of various scale and intensity. The paper presents the layout and results of an explosion experiment on the compression of an enstatite sphere with spherical shock waves and the subsequent recovery of the experimental material and its examination in discrete zones (along the sphere radius) that were produced by shock waves in the material. The latter were examined with the application of scanning electron microscopy, Raman spectroscopy, and X-ray diffraction analysis. The comparison of the systematic variations in the texture, chemistry, and phase composition of enstatite along the sphere radius with calculated pressure P(R, t) and temperature T(R, t) values led us to the following conclusions: enstatite starts melting on an isentrope upon pressure relief after shock wave compression at ?? xx ?? 80 GPa and melts on the front of the spherically converging shock wave at ?? xx ?? 160 GPa and T ?? 6300 K. Our laboratory experiments with shock waves were the world??s first in which enstatite was loaded with spherical converging shock isentropic waves and which provided evidence that shock wave-loaded MgSiO3 shows certain morphological and mineralogical features never before detected in this mineral loaded with plane shock wave of smaller amplitude and duration. Goals are formulated for the further studying of shock wave-loaded materials, and the necessity is discussed for conducting an explosion experiment with a five to seven times greater spherical system in order to increase the duration of the shock wave loading impulse. 相似文献
7.
L. V. Sazonova V. I. Fel’dman E. A. Kozlov N. A. Dubrovinskaya L. S. Dubrovinskii 《Geochemistry International》2006,44(2):137-142
Ringwoodite, a high-density olivine modification, was first synthesized by loading plagioclase-biotite-quartz schist containing garnet and staurolite by impact waves. Ringwoodite was identified in the impact-thermal aggregates that replaced biotite (together with a mineral corresponding to spinel in chemical composition and with a biotite residue). The physical parameters under which ringwoodite was synthesized in this experiment (P imp ～ 20–30 GPa and T ～ 1060–1500°C) include a pressure approximately 1.5 times higher than that in static analogous experiments. The ringwoodite was formed via the regrouping of and the associated removal and addition of material, as follows from the development of ringwoodite after biotite, a mineral of principally different composition. Component migration was reliably confirmed by the microprobe mapping of the chemistries of the original and newly formed minerals, which makes the origin of the ringwoodite similar to the origin of diamond (togorite) in the Kara astrobleme, where the impact loading was up to ten times higher than the static pressure. 相似文献
8.
文章主要通过电子探针、扫描电镜、激光拉曼光谱、透射电镜等微区微分析技术研究GRV 022115球粒陨石的基础矿物学特征和冲击变质矿物学特征，探讨陨石冲击熔融脉的形成机制和界定其母体的冲击条件。陨石主岩主要由橄榄石、辉石、熔长石、铁镍金属和硫化物等矿物组成。根据主岩的硅酸盐矿物学特征，确定GRV 022115是风化程度较低（W1） 的L6型普通球粒陨石，与前期分类结果一致。根据熔融脉内含有大量林伍德石的现象，修正GRV 022115陨石的冲击级别为S6，比原定的S5高一个级别。GRV 022115球粒陨石中有多条冲击熔融脉，熔融脉由基质和主岩碎块包裹体两类岩相组组成。熔融脉基质的主要组成是微米级粒状镁铁榴石与纳米级的含铁方镁石，是在平衡冲击压力下结晶的产物。冲击熔融脉主岩碎块包裹体中的橄榄石、低钙辉石、长石碎块已部分或全部转为相对应的高压相。橄榄石相变为林伍德石；个别低钙辉石相变为钙钛矿结构布里奇曼石微晶的集合体；长石主要相变为熔长石与玲根石。几乎所有的主岩碎块都有高温熔融的圆滑边界。熔融脉内外同类矿物的主量和微量元素具有一定的差异性，该差异性可以反映高温高压下混溶作用和扩散作用的影响。结合陨石冲击熔融脉形成机制和结晶模型，根据熔脉基质中镁铁榴石+方镁石矿物组合及静态高温高压实验相图，界定该陨石经受的冲击压力为23~27 GPa。 相似文献
9.
橄榄石高压多形林伍德石被认为是地幔过渡带的主要矿物。天然产状林伍德石主要在发生强烈冲击变质的球粒陨石冲击脉体中出现。目前还没有在地球岩石中发现林伍德石的报告。陨石冲击脉体的温度压力历史和矿物组合特征研究表明,林伍德石形成后,高压下淬火是使林伍德石不发生退变作用的重要条件。陨石中有利于林伍德石保存的淬火时间仅为数秒到十多秒。在地球上任何地质事件中,均难以实现在如此短的时问内使位于地幔过渡带的林伍德石被带往地球表层。寻找地球产状的林伍德石,关键是要在岩石和矿物中存在有利于林伍德石保存的条件,特别是当这些岩石和矿物仍处于高温的环境时。 相似文献
10.
We conducted CO2–water–rock interaction experiments to elucidate the dissolution characteristics and geochemical trapping potential of three different altered andesitic to rhyolitic tuffaceous rocks (Tsugawa, Ushikiri and Daijima tuffaceous rock) relative to fresh mid-ocean ridge basalt. The experiments were performed under 1 MPa CO2 pressure to reproduce the water–rock–CO2 interactions in CO2 storage situations. Basalt showed high acid neutralization potential and rapid dissolution of silicate minerals. Two of the tuffaceous rocks (Ushikiri and Daijima) showed relatively high solubility trapping potential, mainly due to the dissolution of carbonate minerals in the andesitic Ushikiri tuffaceous rock and the ion-exchange reaction with zeolite minerals in the rhyolitic Daijima tuffaceous rock. The mineral trapping potential of the Ushikiri tuffaceous rock was found to be relatively high, due to the rapid dissolution of Mg- and Ca-bearing silicate minerals. Our experimental results suggest that regions of porous and andesitic tuffaceous rock hold global promise as CO2 storage sites. 相似文献
11.
The mineralogy of shock vein matrix in the Suizhou meteorite has been investigated by optical and transmission electron microscopy. It was revealed that the vein matrix is composed of majorite-pyrope garnet, magnesiowüstite, and ringwoodite, with FeNi–FeS intergrowths. The observation and character of ring-like selected electron diffraction (SAED) patterns indicate that the idiomorphic garnet crystals in the vein matrix have different orientations. The polycrystalline nature of magnesiowüstite is also confirmed by a ring-like SAED pattern. Both garnet and magnesiowüstite crystals showed sharp diffraction spots, signifying the good crystallinity of these two minerals. The SAED pattern of cryptocrystalline ringwoodite shows only diffuse concentric diffraction rings. FeNi metal and troilite (FeS), which were molten during the shock event, occur in the matrix as fine eutectic FeNi–FeS intergrowths filling the interstices between garnet and magnesiowüstite grains. Based on the phase diagram of the Allende chondrite and the results of this TEM study, it is inferred that majorite-pyrope garnet first crystallized from the Suizhou chondritic melt at 22–26 GPa, followed by crystallization of magnesiowüstite at 20–24 GPa, and then ringwoodite at 18–20 GPa. The eutectic intergrowths of FeNi-metal and troilite are proposed to have crystallized during meteorite cooling and solidified at the last stage of vein formation. 相似文献
12.
Neoformed minerals in shallow fault rocks are increasingly recognized as key to the behavior of faults in the elasto-frictional regime, but neither the conditions nor the processes which wall-rock is transformed into clay minerals are well understood. Yet, understanding of these mineral transformations is required to predict the mechanical and seismogenic behavior of faults. We therefore present a systematic study of clay gouge mineralogy from 30 outcrops of 17 low-angle normal faults (LANF's) in the American Cordillera to demonstrate the range and type of clay transformations in natural fault gouges. The sampled faults juxtapose a wide and representative range of wall rock types, including sedimentary, metamorphic and igneous rocks under shallow-crustal conditions. Clay mineral transformations were observed in all but one of 28 faults; one fault contains only mechanically derived clay-rich gouge, which formed entirely by cataclasis.Clay mineral transformations observed in gouges show four general patterns: 1) growth of authigenic 1Md illite, either by transformation of fragmental 2M1 illite or muscovite, or growth after the dissolution of K-feldspar. Illitization of fragmental illite–smectite is observed in LANF gouges, but is less common than reported from faults with sedimentary wall rocks; 2) ‘retrograde diagenesis’ of an early mechanically derived chlorite-rich gouge to authigenic chlorite–smectite and saponite (Mg-rich tri-octahedral smectite); 3) reaction of mechanically derived chlorite-rich gouges with Mg-rich fluids at low temperatures (50–150 °C) to produce localized lenses of one of two assemblages: sepiolite + saponite + talc + lizardite or palygorskite +/− chlorite +/− quartz; and 4) growth of authigenic di-octahedral smectite from alteration of acidic volcanic wall rocks. These transformation groups are consistent with patterns observed in fault rocks elsewhere. The main controls for the type of neoformed clay in gouge appear to be wall-rock chemistry and fluid chemistry, and temperatures in the range of 60–180 °C. 相似文献
13.
Zheng Haifei Xie Hongsen Xu Yousheng Song Maoshuang Zhang Yueming Wang Mingzai Xu Huigang Department of Geology Peking University Beijing Institute of Geochemistry Chinese Academy of Sciences Guiyang Guizhou 《《地质学报》英文版》1996,70(2):157-167
The experimental study on the melting of potassic basalt and eclogite with about 2% waterat 800-1300℃ and 1.0-3.5 GPa shows that the solidi of both rocks are significantly lower thanthose obtained from the previous experiments of the same type of rocks under dry conditions,and the former which is enriched in potassium has a lower melting point than the latter. It is con-sistent with the previous study. The melting temperature of eclogite increases with pressure,whereas potassic basalt has similar properties only at 1.5—2.5 GPa and>3.0 GPa, and at 2.5—3.0 GPa the melting temperature decreases with pressure. This can be explained as follows: (1)eclogite only has one hydrous mineral amphibole and the dehydous temperature is lower than thewet solidus of the rock. (2) Amphibole exists in potassic basalt at the pressures lower than 2.5GPa and phlogopite exists at pressures higher than 2.5 GPa, and the special compositions of bothminerals determine that amphibole has a dehydration temperature higher than or close to that ofthe wet solidus of the rocks, while phlogopite has a dehydration temperature lower than that ofthe wet solidus. On the other hand the features of the continuous solidus in the experiment ofhydrous eclogite were produced by the fact that the dehydration temperature of its amphibolelower than or close to the melting temperature of the hydrous conditions. So the melting tempera-ture lowers at higher pressures. Therefore, the composition of the rocks in the lithosphere and thetypes of hydrous minerals and their stable P-T conditions are the important factors controllingthe solidi of rocks. It can quite well explain the partial melting of rocks and the origin of the lowvelocity zone in the deep lithosphere. 相似文献
14.
This paper reports results of experimental study of the influence of shock waves on the structure, ion valence, and phase composition of oxides, including the minerals tenorite (CuO) and hausmannite (Mn3O4) and perovskite-structured manganite LaMnO3. Shock-wave loading (SWL) was modeled by explosion experiments in spherical and cylindrical (in the case of tenorite) configurations. The results of strong quasi-static shear deformations of oxides under pressure are also given for comparison. The main focus was the investigation of shock wave-induced changes in oxides at the level of chemical bonds, disturbances of ionic composition and stoichiometry, relation of these processes to the formation of micro(nano)structures in the minerals, and stages and microscopic mechanisms of the development of new dense phases. It was shown that SWL-affected oxides can be successfully investigated by various methods of X-ray spectroscopy (photoelectron, absorption, and emission) and nuclear techniques (Rutherford back scattering, nuclear reaction analysis, and positron annihilation spectroscopy). Crystal structure and phase composition were explored by X-ray and neutron diffraction methods. Microscopic structures were investigated by optical, scanning electron, and scanning tunneling microscopy. It was shown that the effects of SWL are initially manifested in oxides as a stoichiometry violation, an increase in the number of low-valence cations, and formation of a micro(nano)structure. Plastic deformations developed during SWL are especially important for these processes. The decomposition of oxides during the solid-phase stage of shock metamorphism under the influence of high pressures, temperatures, and severe plastic deformations produces oxides with a low degree of oxidation and free oxygen, which can migrate over considerable distances to form new compounds. The ultradeep penetration of particles of the surrounding matrix into the target mineral during SWL can also serve as a mechanism of shock metamorphism at the solid-phase stage of transformation. 相似文献
15.
Burkhard O. Dressler Virgil L. Sharpton Benjamin C. Schuraytz 《Contributions to Mineralogy and Petrology》1998,130(3-4):275-287
The Slate Islands archipelago is believed to represent the central uplifted portion of a complex impact structure. Planar
microstructures in quartz and feldspars and shock vitrification of rocks are the most common shock metamorphic features encountered.
No diaplectic quartz was identified in the exposed rocks, but minor maskelynite is present. Shatter cones occur on all islands
of the archipelago suggesting minimum pressures of 4 ± 2 GPa. The relative frequency of low index planar microstructures of
specific, optically determined crystallographic orientations in quartz are correlated with results from shock barometric experiments
to estimate peak shock pressures experienced by the exposed target rocks. In general, there is a decrease in shock pressure
recorded in the target rocks from about 20–25 GPa in east-central Patterson Island to about 5–10 GPa at the western shore
of this island and on Mortimer Island. The shock attenuation gradient is ∼4.5 GPa/km across this section of the island group.
However, the shock attenuation has a roughly concentric plan only over the western part of the archipelago. There is no distinct
shock center and there are other deviations from circularity. This is probably the result of: (1) the shock wave not having
expanded from a point or spherical source because of the ∼1. 0 to 1.5 km size of the impactor; (2) differential movement of
large target rock blocks during the central uplift and crater modification phases of the impact process. The orientation of
planar deformation features in quartz appears to be independent of the shock wave direction suggesting that crystal structure
exerts the primary control on microstructure development. Based on the results of XRD analyses, residual, post-impact temperatures
were high enough to cause annealing of submicroscopic damage in shocked quartz.
Received: 15 July 1997 / Accepted: 6 October 1997 相似文献
16.
Leander Franz Rolf L. Romer Christian de Capitani 《Contributions to Mineralogy and Petrology》2013,166(1):255-274
Whiteschists appear in numerous high- and ultrahigh-pressure rock suites and are characterized by the mineral assemblage kyanite + talc (+-quartz or coesite). We demonstrate that whiteschist mineral assemblages are well stable up to pressures of more than 4 GPa but may already form at pressures of 0.5 GPa. The formation of whiteschists largely depends on the composition of the protolith, which requires elevated contents of Al and Mg as well as low Fe, Ca, and Na contents, as otherwise chloritoid, amphibole, feldspar, or omphacite are formed instead of kyanite or talc. Furthermore, the stability field of the whiteschist mineral assemblage strongly depends on XCO2 and fO2: already at low values of XCO2, CO2 binds Mg to carbonates strongly reducing the whiteschist stability field, whereas high fO2 enlarges the stability field and stabilizes yoderite. Thus, the scarcity of whiteschist is not necessarily due to unusual P–T conditions, but to the restricted range of suitable protolith compositions and the spatial distribution of these protoliths: (1) continental sedimentary rocks and (2) hydrothermally and metasomatically altered felsic to mafic rocks. The continental sedimentary rocks that may produce whiteschist mineral assemblages typically have been deposited under arid climatic conditions in closed evaporitic basins and may be restricted to relatively low latitudes. These rocks often contain large amounts of the clay minerals palygorskite and sepiolite. Marine sediments generally do not yield whiteschist mineral assemblages as marine shales commonly have too high iron contents. Sabkha deposits may have too high CO2 contents. Protoliths of appropriate geochemical composition occur in and on continental crust. Therefore, whiteschist assemblages typically are only found in settings of continental collision or where continental fragments were involved in subduction. Our calculations demonstrate that whiteschists can form by closed-system metamorphism, which implies that the chemical and isotopic composition of these rocks provide constraints on the development of the protoliths. 相似文献
17.
数值计算中利用随机分布对各单元赋予不同的物理力学参数来考虑岩石的非均质性,赋值过程是纯随机的,并没有考虑岩石矿物组成的结构特征。故提出一种新的岩石非均质参数赋值方法--岩石矿物细胞元随机性参数赋值方法,基于岩石矿物种类及其含量定义细胞元类别判定区间,利用Monte Carlo方法对各个细胞元进行矿物类别判定,并进行相应的参数赋值,通过各矿物细胞元的随机混合体来描述岩石的非均质性。该方法既考虑了组成岩石的矿物种类及其含量（结构特征）,又考虑了组成矿物在岩石中的随机分布特征。针对矿物分布的随机特征,利用两矿物细胞元混合模型和三矿物细胞元混合模型进行数值试验,研究了矿物细胞元随机分布特征对岩石宏观力学参数的影响。研究结果表明,岩石矿物细胞元随机性参数赋值方法具有结构性和随机性的双重特性,其随机性不依赖于随机参数,岩石宏观力学参数受细胞元随机性特征的影响很小。 相似文献
18.
The elastic properties of cordierite, a common volatile-bearing metamorphic mineral, were measured using Brillouin spectroscopy
under ambient conditions. We obtain a bulk modulus of KS =129(1) GPa, and a shear modulus of G=54.0(4) GPa. The bulk modulus of cordierite is much larger than those of other crustal
framework silicates (e.g., quartz and feldspars), but is similar to KS for denser upper mantle phases such as olivine. This is likely a result of the cordierite crystal structure, as suggested
by a similarly high value of KS for minerals with closely related structures. Cordierite has an unusually high K/G ratio of about 2.4, and a Poisson’s ratio
of 0.31,which may be a diagnostic seismic properties of areas in which cordierite-rich metamorphic rocks occur. The overall
velocity anisotropy of cordierite is relatively low (<14%) in comparison with many other metamorphic minerals. Calculated
velocities for a representative lower crustal rock suggest that cordierite is not likely to explain the high seismic anisotropy
observed in some lower crustal sections. Cordierite would have a strong influence on the bulk seismic anisotropy only in rocks
where it is present in large concentrations and has a strong preferred orientation. Although such rocks are known to occur,
they are uncommon.
Received: 23 Deceber 1997/ Revised, accepted: 12 October 1998 相似文献
19.
The considered part of ductile shear zones, which are widespread in the area of the village of Gridino in the central part
of the Belomorian Mobile Belt, is accompanied by the high-temperature eclogitization of basites. The paper reports examples
of eclogitization in rocks of various age, mostly in rocks of the Early Proterozoic lherzolite-gabbronorite and coronite gabbro
complexes. The degrees of structural and mineralogical transformations in unequally deformed bodies of gabbronorites and olivine
gabbronorites of the lherzolite-gabbronorite complex are correlated with the degrees of deformations of these rocks and their
fluid recycling. The relatively weakly deformed rocks have massive and apomagmatic textures with garnet and omphacite reaction
rims at boundaries between grains of magmatic plagioclase and pyroxenes. These rims are typical of the domainal equilibrium
stage, which is an intermediate eclogitization stage between a magmatic rock and completely equilibrated eclogite. The enhancement
of rock deformation results in the development of equilibrium eclogite with anisotropic metamorphic textures and structures.
Textural transformations simultaneous with intense deformations are manifested involved the recrystallization of magmatic
minerals and the development of linear fine-grained mineral aggregates of the Pl-Opx-Grt-Omp eclogite mineral assemblage and the systematically oriented growth of much larger mineral neoblasts in amphibole eclogite
assemblages. 相似文献
20.
微生物对碳酸盐岩的风化作用 总被引：7，自引：0，他引：7
微生物-矿物相互作用可以促进许多表生生物地球化学反应过程,是表生地球化学研究的重要内容。通过综合岩石表面的微生物类群及其地质作用,分析碳酸盐岩微生物风化的各种现象,特别是微观尺度上的各种形态,阐述碳酸盐岩的微生物风化机制与风化产物,笔者提出微生物对碳酸盐岩风化的4种途径:(1)通过微生物在岩石表面和缝隙中生长,导致岩石表层发生生物溶蚀、生物磨蚀和生物钻孔作用,加速岩石风化进程;(2)微生物群体形成的钻孔网络可以增强岩石化学溶蚀的有效表面积并导致其表面强度减弱而促进机械侵蚀作用,微生物对周围岩石颗粒胶结结构的破坏、疏松作用也会导致岩石矿物颗粒的分解;(3)微生物的持水作用,微生物分泌的有机酸以及微生物呼吸所释放的CO2对岩表水分的酸化过程亦加速岩石矿物的分解;(4)微生物生长过程中从岩石内摄取营养元素和产生复杂的有机配体,能促进矿物元素的释放。文中提出在开展微生物对碳酸盐岩风化过程和机理研究的基础上,有必要引入微生物生物技术来综合开发本地低品位含钾磷矿产资源,加速岩溶地区山地土壤的形成与演化。 相似文献