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1.
庐江陨石中的不透明矿物   总被引：1，自引：0，他引：1  
庐江陨石是一化学岩石类型为ＬＬ６的球粒石陨石。研究表明该陨石中不透明矿物有铁纹石,镍纹石,陨硫铁,铬铁矿,钛铁矿和赤铁矿等。本文对它们的产状,成分和结构进行了研究。  相似文献   

2.
New data on the mineral composition of the Severny Kolchim meteorite, found in Perm Region in 1965, are presented. It has been found that that the meteorite matter is composed of olivine (chrysolite), orthopyroxene (bronzite), clinopyroxene (diopside), plagioclase (oligoclase, bytownite), glass, chromite, magnetite, ilmenite, rutile, metals Fe and Ni (kamasite, taenite, tetrataenite), copper, sulfides (troilite, pentlandite, covellite), chlorapatite, and merrillite. Diopside, tetrataenite, chlorapatite, and merrillite were identified in the Severny Kolchim meteorite for the first time. The chemical compositions are given for all these minerals. The meteorite itself is a nonequilibrium ordinary chondrite stone belonging to petrological type H3.  相似文献   

3.
New data on the mineral composition of Kargapole meteorite, which was found in Kurgan oblast in 1961, are presented. It has been established that the meteoritic material is represented by olivine (chrysolite), orthopyroxene (bronzite), clinopyroxene (diopside), plagioclase (oligoclase), chromite, Fe and Ni metal particles (kamacite, taenite, tetrataenite), sulfides (troilite, pentlandite), chlorapatite, and merrillite. For the first time, diopside, tetrataenite, pentlandite, chlorapatite, and merrillite were identified in the Kargapole meteorite. The chemical compositions of all minerals studied are given in Table 1. In terms of petrology, the meteorite is classified a common H4 chondrite.  相似文献   

4.
In order to gain a better understanding of the formation of plessite in iron meteorites, various electron optical techniques were employed to study the range of plessite structures observed in the Carlton fine octahedrite. Compositional and structural studies of twins in clear taenite and the cloudy zone were made. Transmission electron microscopy studies of martensitic and duplex α + γ plessite regions show the presence of γ-taenite rods, 10–200 nm wide, in an α-kamacite matrix. Scanning transmission electron microscope X-ray analyses showed Ni contents in the y rods of ≥43wt% and Ni contents in the a matrix of 3 wt% Ni. The reaction path involves the decomposition of α2 martensite into α + γ and these reactions occur below 200°C and possibly below 100°C. Apparently the formation of plessite is intimately related to the formation of martensite and the further decomposition of martensite during the cooling history of the meteorite. It is quite probable that the martensite decomposition reaction has occurred in a large number of iron meteorites and is responsible for many of the observed plessite structures.  相似文献   

5.
Taenite fields when etched develop a cloudy brown rim with approximate compositional limits of 25 and 40 per cent Ni. In iron meteorites this cloudy zone is only a few microns wide, with a sharp, high-Ni edge about 1 μm from the kamaciteinterface and a diffuse edge several microns from the central plessite. It is always present in irons unless the meteorite has been cosmically or terrestrially reheated.X-Ray and electron diffraction of grains scratched from exceptionally large areas of cloudy taenite in the mesosiderite Estherville show that this etching zone contains a fine exsolution of kamacite. Electron microscopy reveals a cellular structure with kamacite walls surrounding taenite volumes about 1000 Å in diameter; about one-third of the total volume is kamacite. Electron diffraction from a thin foil of Tazewell indicates that for several microns the cloudy border consists of a single crystal of kamacite interpenetrating a single crystal of taenite.Detailed electron-probe investigations of taenite in Estherville show that there is a step in the M-shaped Ni profile at the sharp, high-Ni edge of the cloudy region, the Ni dropping suddenly from approximately 45 to 42 per cent. It is proposed that exsolution in the cloudy region effectively froze in the Ni profile at that temperature. On subsequent cooling only the clear outer taenite continued to equilibrate with the kamacite matrix producing the kink in the M profile.Cloudy taenite is therefore a variety of plessite differing from the usual varieties in that it forms at lower temperatures in areas much richer in Ni, and the morphology is not crystallographically oriented. Its absence can provide a sensitive indication of reheating.  相似文献   

6.
New data on the mineral composition of the Ozernoye meteorite, found in the Kurgan region in 1983, are presented. It has been found that that the meteorite’s matter is composed of olivine (chrysolite), orthopyroxene (bronzite), clinopyroxene (augite), maskelynite, chromite, ilmenite, metals Fe and Ni (kamasite, taenite), sulfides (troilite, pentlandite), chlorapatite, and merrillite. Augite, taenite, pentlandite, and merrillite were identified in the Ozernoye meteorite for the first time. The chemical compositions are given for all these minerals. The meteorite itself is an ordinary chondrite stone belonging to petrological type L5.  相似文献   

7.
The Shaw L-group chondrite consists of three intermingled lithologies. One is light-colored and has a poikilitic texture, consisting of olivine (many skeletal and euhedral) and augite crystals surrounded by larger (up to 1 mm) orthopyroxene grains; plagioclase occurs between orthopyroxene crystals and rare, small (<5 μm) patches of Si-K-rich glass or cryptocrystalline material occurs within the plagioclase. The skeletal olivine crystals contain 0.08–0.16 wt% CaO. Petrofabric measurements show that the c-axes of the olivines are aligned. The light-colored lithology also contains numerous vugs and vesicles: SEM studies reveal euhedral, possibly vapor-deposited, crystals of olivine and pyroxene in the vugs. A second lithologic type is dark-colored, contains remnant chondrules. and has a microgranular texture. Poikilitic orthopyroxene crystals, where present, are smaller (0.1–0.2mm) than they are in the light-colored lithology. Microgranular olivine crystals contain <0.08 wt% CaO: most contain 0.03–0.05 wt% CaO. Vugs are rare and Si-K-rich material is absent. The third lithologic type is gray macroscopically and seems to be intermediate between the other two. It has a well-developed poikilitic texture, but contains neither skeletal olivines (euhedral olivines are rare) nor Si-K-rich material: remnant chondrules are present but less abundant than in the dark lithology. A modal analysis of a 5300 mm2 slab shows, contrary to published opinions, that Shaw contains normal L-group chondrite abundances of metal and troilite. However, these phases are distributed irregularly throughout the meteorite. The light colored lithology is nearly devoid of metal and troilite and centimeter-sized metal-troilite globules occur between the three silicate lithologies. Wherever the metal occurs, it consists of nearly homogeneous martensite (13.9 wt% Ni) rimmed by kamacite (7.1 wt% Ni). These data indicate that Shaw is a partly-melted shock-breccia. The light-colored lithology must have been totally melted, as shown by the presence of aligned. CaO-rich, skeletal olivines; Si-K-rich residual material: and vugs and vesicles lined with euhedral crystals of mafic silicates. The dark areas appear to be unmelted target rock of L-group composition. Analysis of the growth of kamacite at the taenite (now martensite) borders indicates a cooling rate of ~ 3 C/103 yr. or one thousand times faster than most ordinary chondntes. The Shaw impact event probably formed a crater several kilometers in diameter on its meteorite parent body.  相似文献   

8.
Electron optical techniques were employed to investigate the plessite structure and composition of four IIICD fine octahedrites. These meteorites have a similar thermal history and differences in plessite structure can be ascribed to varying bulk Ni content and/or localized differences in carbon content. Microdiffraction patterns from regions as small as 20 nm dia. were obtained for the first time from plessite structures. It was established that transformation twins in clear taenite I have the conventional fcc twin relationship, individual kamacite and taenite cells in the cloudy zone have the Kurdjumov-Sachs orientation and fine γ rods in the decomposed martensite zone display both the Nishiyama and Kurdjumov-Sachs relation with the matrix-α. All the IIICD irons contain cloudy zone and martensitic plessite. Except for Dayton, martensitic plessite shows further decomposition into α + λ at low temperatures. Using STEM X-ray microanalysis with a spatial resolution of ~ 50 nm, Ni composition profiles in taenite from all the IIICD irons showed a maximum of ~48 wt% Ni. The structural and compositional data indicate that plessite formation occurs at quite low temperatures (~ 200–300°C) during the cooling history of the IIICD irons.  相似文献   

9.
The fragments of the Chelyabinsk meteorite studied are represented by light-gray granular rock of chondritic structure. The chondrules and their cementing matter are mainly constituted by olivine and orthopyroxene. The matrix consists of a pyroxene-olivine aggregate with plagioclase, apatite, melted glass, and the inclusions of ore minerals: taenite, kamacite, troilite, pyrrhotite and pentlandite (more rarely), and individual grains of chromite and ilmenite. The comparison of the composition of the Chelyabinsk meteorite to the average composition of LL chondrites had shown their complete convergence. The concentrations of sidero- and chalcophile rare elements in the meteorite, normalized to CI chondrites, are much close to the values for LL chondrites and almost reproduce the character of their distribution in the spider diagram. However, some high-charged and lithophile elements (Nb, Zr, Hf, Sr, Ba, Th, and U) not belonging to the mentioned groups are characterized by somewhat increased contents. The enrichment of the samples of the Chelyabinsk meteorite in rare-earth elements compared to LL chondrite (5.18 against 3.58 ppm) is also revealed. This is related to the higher concentrations of light lanthanides in the meteorite samples, which is seen from the increased La/Yb ratio compared to the value for LL chondrite (1.9–2.3 and 1.4, respectively). Iron-nickel alloys are the main magnetism carriers in the Chelyabinsk meteorite. The compositions of kamacite, taenite, chromite, and Fe-sulfides are not much different. The optical and microprobe data are confirmed by the thermomagnetic parameters as well: (1) The specific magnetization of 4–6 Am2/kg points to small variations in the concentrations of magnetic minerals. (2) The M(T) curves for all the samples nearly repeat each other, and the Curie temperatures of 490–520 and 740–770°C are registered in the curves of the first and second heating, hence, these curves correspond to kamacite of various composition, right up to pure iron. (3) The monocline ferrimagnetic pyrrhotite of TC = 320–340°C is registered in the treated fragments in both the M(T) curves of heating and cooling. (4) The concentrations by thermomagnetic analysis amount to 0.6–1.6% (0.9% average) for kamacite, 0.7–1.5% (1.1% average) for taenite, and 0–1.5% (0.4% average) for monocline pyrrhotite. (5) No magnetite was found in the M(T) curve during the first heating of the samples. Hence, the content of magnetite is much below 0.1.  相似文献   

10.
Keilite (Fe>0.5,Mg<0.5)S, the iron-dominant cubic analog of niningerite, (Mg>0.5,Fe<0.5)S, occurs in enstatite chondrites [Shimizu, M., Yoshida, H., Mandarino, J.A., 2002. The new mineral species keilite, (Fe,Mg)S, the iron-dominant analog of niningerite. Can. Mineral. 40, 1687–1692]. I find that keilite occurs only in enstatite chondrite impact-melt rocks and impact-melt breccias. Based on the phase relations in the system MgS–MnS–CaS–FeS [Skinner, B.J., Luce, F.D., 1971. Solid solutions of the type (Ca,Mg,Mn,Fe)S and their use as geothermometers for the enstatite chondrites. Am. Mineral. 56, 1269–1296], I conclude that keilite formed from niningerite or alabandite (Mn>0.5,Fe<0.5)S by reaction with troilite (FeS) at elevated temperatures of well above 500 °C (the lowest equilibration temperature of keilite), but it is likely that the maximum temperatures during melting experienced by keilite-bearing impact-melt rocks and impact-melt breccias were considerably higher, perhaps >1500 °C, as indicted by the occurrence of euhedral enstatite that formed from a melt [McCoy, T.J., Dickinson, T.L., Lofgren, G.E., 1999. Partial melting of the Indarch (EH4) meteorite: a textural, chemical, and phase relations view of melting and melt migration. Meteorit. Planet. Sci. 34, 735–746]. Based on the classifications of the keilite-bearing meteorites as impact-melt rocks and impact-melt breccias and my own textural observations, I conclude that this elevated temperature was reached as a result of impact and not internal heating and melting, followed by fast cooling, thus, quenching in keilite. Enstatite chondrite impact-melt rocks and impact-melt breccias that do not contain keilite may have been more deeply buried after impact and, hence, cooled slowly and were annealed so that FeS exsolved from keilite, concomitant with the formation of niningerite, alabandite or various (Mn,Mg,Fe) mixed sulfides.  相似文献   

11.
On September 13, 1976, the Qingzhen enstatite chondrite fell near Qingzhen County, Guizhou Province (26°32′N, 106°28′E). The total mass recovered was 2.6 kg. Phenomena of the meteorite fall were recorded as well. In the present paper some of the significant observations are described. X-ray diffraction analyses and petrologic studies revealed that it is mainly composed of enstatite/clinoenstatite, plagioclase, troilite, kamacite, taenite, quartz and oldhamite. X-ray electron microprobe analyses were performed on orthoenstatite and clinoenstatite. Chemical analysis gave: SiO2-36.48; Al2O3-1.64; TiO2-0.08; Cr2O3-0.28; FeO-0.30; MnO-0.25; MgO-18.19; CaO-1.14; Na2O-1.06; K2O-0.11; H2O+-0.47; H2O?-0.10; P2O5-0.39; FeS-13.35; FeO-22.94; Ni-1.81; Co-0.093; C-0.37; Cu-0.022; Zn-0.027; CaS-0.60; total-99.70 (wt.%). This meteorite has been extremely reduced; all iron is present as FeS and metallic Fe-Ni. The Qingzhen enstatite chondrite is characterized by high ratio, Si/Mg as compared with ordinary chondrites, scarcity of olivine, and enrichment in sulfur and iron. In thin sections, it is observed that round chondrules approximately account for 10–15 per cent, being porphyritic, radial, excentroradial, or excentric fan-shaped. Devitrified chondrules composed of pyroxene were also identified. It is postulated from its mineralogy, chemistry and textural characteristics that the Qingzhen meteorite should be assigned toE 4 orEH chondrites.  相似文献   

12.
This work describes the application of microfocus X-ray absorption spectroscopy (XAS) and X-ray photo-emission electron microscopy (XPEEM) to the study of the complex mineralogical intergrowths within the Santa Catharina meteorite. The Santa Catharina meteorite of this study (BM52283 from the meteorite collection of the Natural History Museum, London, UK) primarily comprises a taenite bulk host phase (Fe:Ni ratio = 70.9 ± 0.8%:29.1 ± 0.8%) with a set of oxide-bearing cloudy zone textured regions (Fe:Ni:O ratio = 40.4 ± 0.3%:49.0 ± 0.7%:10.6 ± 0.8% at the core and Fe:Ni:O ratio = 34.4 ± 1.5%:42.7 ± 0.6%:22.9 ± 1.8% towards the rims) and numerous schreibersite (Fe:Ni:P ratio = 38.6 ± 1.6%:38.4 ± 0.9%:23.0 ± 0.5%) inclusions. Between the schreibersite and the taenite are rims up to 50 μm across of Ni-rich kamacite (Fe:Ni ratio = 93.4 ± 0.4%:6.6 ± 0.5%). No chemical zoning or spatial variations in the Fe and Ni speciation was observed within either the schreibersite or the kamacite phases. The oxide-bearing cloudy zone textured regions mostly comprise metallic Fe–Ni alloy, predominantly tetrataenite. Within the oxide phases, the Fe is predominantly, but not entirely, tetrahedrally co-ordinated Fe3+ and the Ni is octahedrally co-ordinated Ni2+. Structural analysis supports the suggestion that non-stoichiometric Fe2NiO4 trevorite is the oxide phase. The trevorite:tetrataenite ratio increases at the edges of the oxide-bearing cloudy zone textured regions indicating increased oxidation at the edges of these zones. The spatial resolution of the XPEEM achieved was between 110 and 150 nm, which precluded the study of either the previously reported ∼ 10 nm precipitates of tetrataenite within the bulk taenite or any antitaenite.  相似文献   

13.
Optical and electron optical (SEM, TEM, AEM) techniques were employed to investigate the fine structure of eight ataxite-iron meteorites. Structural studies indicated that the ataxites can be divided into two groups; a Widmanstätten decomposition group and a martensite decomposition group. The Widmanstätten decomposition group has a Type I plessite microstructure and the central taenite regions contain highly dislocated lath martensite. The steep M shaped Ni gradients in the taenite are consistent with the fast cooling rates, ≥500°C/my, observed for this group. The martensite decomposition group has a Type III plessite microstructure and contains all the chemical group IVB ataxites. The maximum taenite Ni contents vary from 47.5 to 52.7 wt% and are consistent with slow cooling to low temperatures ≤350°C at cooling rates ≤25°C/my. Ordered FeNi and the cloudy border structure were not observed in any of the ataxites. Modest reheating to ≤350°C may have been responsible for the lack of these structures.  相似文献   

14.
Zusammenfassung Der jüngste Granit im österreichischen Moldanubikum ist der im nordwestlichen Waldviertel aufgeschlossene Eisgarner Granit.Das Gestein ist ein Zweiglimmergranit. Der Plagioklas (20–28 Vol.-%), selten zonar gebaut, hat einen durchschnittlichen An-Gehalt von 13%; daneben treten basischere Plagioklase (An bis 30%) als Einschlüsse im Mikroklin auf. Der Alkalifeldspat (25–38 Vol.-%) ist ein gegitterter, perthitisch entmischter Mikroklin mit Or 67–72%, Ab 24–28%, An 1,8–2,8%. Durch den Gehalt an Spurenelementen unterscheidet er sich stark von dem der älteren moldanubischen Granite. Die Triklinität liegt meist unter 0,90. Quarz tritt stellenweise als frühes Kristallisat auf, gehört aber im allgemeinen zu den Letztausscheidungen. Biotit (4–7 Vol.-%) bildel 2M-Polymorphe, ebenso Muskowit (6,5–7,5%), der entweder durch Reaktion von Andalusit mit der Schmelze oder aus Alkalifeldspat durch Reaktion mit der fluiden Phase hervorgegangen ist. Die Akzessorien Spinell, Rutil, Granat und Andalusit weisen darauf hin, daß der Granit durch Anatexis hochmetamorpher Gesteine (Silimanitgneise?) entstanden ist. Die Kristallisation verlief im Temperaturbereich zwischen ca 700° und 600°C bei einem Wasserdampfdruck von ca 5000 bar.
Summary The youngest granite in the Moldanubian zone of Austria is theEisgarn granite which is exposed in the northwestern part of the Lower Austrian Waldviertel.The rock is a two-mica granite. The plagioclase (20–28 vol.-%) has an average An-content of 13% and shows only a weak zonary structure. Also more basic plagioclases (up to An 30) occur as inclusions in microcline. The alkalifeldspar (25–38 vol.-%) is a cross-hatched microcline perthite with the composition Or 67–72, Ab 24–28, An 1,8–2,8. It is distinguished from the microcline perthites of older granites by its content in trace elements. Its obliquity lies below 0,90. Partly the quartz is an early crystallisate, it is commonly a very late product, however. Biotite (4–7 vol.-%) forms the 2M polymorphe, as well as muscovite (6,5–7,5 vol.-%) which may develop by reaction of andalusite with the melt or from alkalifeldspar by reaction with the fluid phase. The accessories rutile, spinel, garnet and andalusite indicate a development of the granite by anatexis of high-metamorphic rocks (sillimanite-bearing gneisses?). Crystallization took place in the temperature range of 700° to 600°C under a water-vapor-pressure of 5000 bars.

Mit 11 Texiabbildungen

Herrn Prof. Dr.H. Leitmeier zum 80. Geburtstag gewidmet.  相似文献   

15.
The solubility limits of the α (kamacite) and γ (taenite) phases in the Fe-Ni and Fe-Ni-P phase diagrams have been measured at low temperatures, 700-300°C. The predicted αα + γ retrograde solubility below 500°C was demonstrated experimentally for the first time in the Fe-Ni system. The minimum solubility of Ni in γ at the γα+γ boundary increases with decreasing temperature to as much as 54 wt% at 300°C. The addition of P increases the maximum solubility of Ni in α by as much as 1.6 wt% and decreases the minimum solubility of Ni in γ by as much as 7 wt% at 300°C.The solubility limits of kamacite and taenite were also obtained from heat-treated samples of the Grant and Cape York iron meteorites. The data indicate that in iron meteorites minor and trace elements other than P do not significantly shift the Ni solubility limits of the Fe-Ni and Fe-Ni-P phase diagrams. The measured phase diagrams can be used to explain the Agrell effect and the differences in maximum Ni content of taenite among irons and chondrites. The formation of plessite and the influence of the measured solubility limits on the cooling rate simulation method are also considered.  相似文献   

16.
We have measured diffusion coefficients for P, Cr, Co, Ni, Cu, Ga, Ge, Ru, Pd, Ir, and Au in Fe metal from 1150 to 1400°C and at 1 bar and 10 kbar. Diffusion couples were prepared from high-purity Fe metal and metal from the IIA iron meteorite Coahuila (single crystal kamacite) or the pallasite Springwater (polycrystalline kamacite) and held at run conditions for 3.5 to 123 h. Diffusion profiles were measured using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) or the electron microprobe. Many elements were measured from the same experimental runs so interelemental comparisons are improved over other data sets in which data for different elements come from different experiments. Some literature diffusion coefficients (D) for Ni and Co in taenite can be up to a factor of 3 higher for Ni than Co, yet our results show no difference (e.g., DNi and DCo ∼ 2.2 × 10-15 m2/s at 1150°C). Thus, diffusion of Ni and Co in single crystal taenite will not measurably fractionate the Ni/Co ratio. On the other hand, the large difference in DNi and DIr (DIr is ∼5 times lower) and the similarity of DNi and DRu at all temperatures investigated indicates that Ni/Ir and Ni/Ru ratios in zoned metal grains will be useful discriminators of processes controlled by diffusion vs. volatility. In zoned metal grains in primitive chondrites, deviations of the Ni/Ru and Ni/Ir ratios from a condensation curve are opposite to a diffusion-controlled process, but consistent with a volatility-controlled process. The new multielement diffusion coefficients will also be useful in evaluating a variety of other processes in planetary science.  相似文献   

17.
陶克捷 《地质科学》1980,15(3):296-298
本文介绍的陨石标本,系朱向君1978年在甘肃省渭源县北寨公社北西约300米处(东经104°19′27″,北纬35°16′28″)拾得。经地质一队岩矿鉴定组做了简单光薄片鉴定、光谱半定量及简便化学分析,认为可能是陨石,把标本转给中国科学院地质研究所。  相似文献   

18.
Magnetic properties of the Chelyabinsk meteorite: Preliminary results   总被引：1，自引：0，他引：1  
This paper presents the distribution of magnetic susceptibility, χ0, in fragments of the Chelyabinsk ordinary chondrite (LL5, S4, W0, fall of February 15, 2013) from the collection of the Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, and results obtained by standard magnetic techniques for the meteorite material, including thermomagnetic analysis, measurements of natural remanent magnetization (NRM) and saturation isothermal remanent magnetization (SIRM), as well as the spectra of their alternating field demagnetization at amplitudes up to 170 mT, measurements of hysteresis loops and back-field remanence demagnetization curves at temperatures from 10 K to 700°C etc. The mean logχ0 values for the light-colored (main) lithology of the meteorite material and impact-melt breccia from our collection are 4.54 ± 0.10 (n = 66) and 4.65 ± 0.09 (n = 38) (×10?9 m3/kg), respectively. According to international magnetic classification of meteorites, Chelyabinsk falls within the range of LL5 chondrites. The mean metal content was estimated from the saturation magnetization, M s, of the light- and dark-colored lithologies as 3.7 and 4.1 wt %, respectively. Hence, the dark lithology is richer in metal. The metal grains are multidomain at room temperature and show low coercive force, B c (<2 mT) and remanent coercive force, B cr (15–23 mT). The thermomagnetic analyses of the samples showed that the magnetic properties of the Chelyabinsk meteorite are controlled mainly by taenite and kamacite at temperatures >75 K. In the temperature range below 75 K, magnetic properties are controlled by chromite; the magnetic hardness of the samples is maximal at 10 K and equals to 606 and 157 mT for the light- and dark-colored lithologies, respectively.  相似文献   

19.
Summary The Chiang Khan meteorite fell on 18th November, 1981 at Chiang Khan, Thailand. It consists of olivine, orthopyroxene, clinopyroxene, Fe-Ni metal, troilite, chromite, plagioclase, glass, and phosphate in order of abundance. Olivine forms barred or porphyritic chondrules, and its composition is uniform (average Fo80.2), close to the average composition of olivine in equilibrated H chondrites. Orthopyroxene and clinopyroxene also have compositions similar to those in equilibrated H chondrites. Both well-defined chondrules and their broken fragments are present in the recrystallized matrix. Microcrystalline plagioclase and clinopyroxene often occur in the groundmass of chondrules, but clear interstitial plagioclase is absent. Chemical composition of chromite plots in the field of chromites in H chondrites. Chiang Khan meteorite is thus classified as an equilibrated H 5 type chondrite. The equilibrium temperatures estimated by using mineral pairs are as follows: Opx-Cpx 800–900°C; Ol-Chromite 510°C.Water content is 0.24 wt %, and the hydrogen isotopic composition (D) is –89.5In the thermal demagnetization experiment magnetization steadily decreased from 0 to 500°C, whereas the remanent magnetization obtained in the A.C. demagnetization experiment is very unstable, probably owing to the large grain size of the Fe-Ni metal.With 9 Figures  相似文献   

20.
Zusammenfassung Sechs bisher als Tonschiefer bezeichnete Gesteine wurden chemisch, röntgenographisch, optisch und mit dem Elektronenmikroskop in Hinblick auf ihre Färbung, ihren quantitativen Mineralbestand sowie ihren Metamorphosegrad untersucht. Diese Untersuchungen zeigten, daß zwei dieser Proben keine reinen Tonschiefer sind, sondern als Chlorit-Talk-Schiefer bzw. als dolomitischer Tonschiefer zu bezeichnen sind.Die Färbung in den Tonschiefern wird durch feinstverteiltes Pigment (grau bis schwarz), Hämatitschuppen (rot) und Chlorit (grün) hervorgerufen.Der quantitative Mineralbestand wurde unter Zuhilfenahme der Dichtebestimmung sowie optischer und röntgenographischer Daten aus den chemischen Analysen errechnet. Muskovit (25 bis 45 Vol.-%), Chlorit (15 bis 25 Vol.-%), Quarz (18 bis 30 Vol.-%) und Albit (2 bis 6 Vol.-%) bilden die Hauptgemengteile; Hämatit, Dolomit und Talk treten als Nebengemengteile auf, wobei Hämatit bis zu 11 Vol.-%, Dolomit bis zu 42 Vol.-% und Talk bis zu 40 Vol.-% erreichen und Übergemengteile bilden können, während sich die Akzessorien aus Pyrit, röntgenamorphem Kohlenstoff, Apatit, Erz, Zirkon und Rutil zusammensetzen.Petrologisch sind diese Gesteine der niedrigsten Stufe der Grünschieferfazies mit der unteren Grenze bei etwa 300°C und etwa 3 Kb zuzuordnen. Die phyllitähnliche Fältelung der Tonschiefer ist Zeugnis für die Durchbewegung während der Metamorphose.
Mineralogy and petrology of east-alpine clay schists
Summary Six rocks, so far called slates, were examined by x-ray, chemical and optical methods to determine the cause of colouring, the quantitative mineralogical composition and the degree of metamorphism. Two of these so-called slates are chlorite-talc-schists and dolomitic slates.The colouring of the slates is due to pigment (gray to black), hematite (red) and chlorite (green).The quantitative mineralogical composition of these rocks is calculated from the chemical analyses. These data are controled by the density and by optical and x-ray results. The mineral assemblages are dominated by muscovite (25–45%), chlorite (15–25%), quartz (18–30%) and albite (2–6%) while hematite, dolomite, pyrite, apatite, ore, zircon, rutile and amorphous carbon are accessory, but in some rocks hematite (11%), dolomite (42%) and talc (40%) are also dominant.The slates belong to the lowest metamorphic part of the greenschist-facies with the lower limit at 300°C and 3 Kb. The phyllitic structure is the result of deformation synchronous with metamorphism.

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