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1.
Annibale Mottana Takatoshi Murata Ziyu Wu Augusto Marcelli Eleonora Paris 《Physics and Chemistry of Minerals》1997,24(7):500-509
X-ray absorption Na K-edge spectra have been recorded on synthetic endmember jadeite and on a series of natural Ca-Na pyroxenes
compositionally straddling the Jd-Di join. The C2/c members of the series are systematically different from the P2/n members. Differences can be interpreted and explained by comparing the experimental spectra with theoretical spectra. These
have been calculated by the multiple-scattering formalism from the atomic positional parameters determined by single-crystal
X-ray diffraction structure refinement on the same samples. In the full multiple scattering region of the spectra (1075 to
1090 eV) C-pyroxenes exhibit three features which reflect the 6-2 configuration of the O back-scattering atoms around the Na absorber
located at the center of the cluster (site M2 of the jadeite structure). P-pyroxenes show more complicated spectra in which at least four (possibly five) features can be recognized; they reflect the
two types of configuration (6-2 and 4-2-2) of O around Na in the two independent M2 and M21 eight-fold coordinated sites of the omphacite structure. A weak, sometimes poorly resolved peak at 1079 eV is diagnostic
and discriminates C- from P-pyroxenes. The Garnet Ridge C2/c impure jadeite exhibits a spectrum which is intermediate between those of jadeite and omphacite. The Hedin-Lundqvist potential
proves best for these insulating materials and allows multiple-scattering calculations agreeing well with experiments.
Received: July 11, 1996/Revised, accepted: October 21, 1996 相似文献
2.
Summary Thaumasite from the manganese mine of Tschwinning, South Africa, has the formula Ca3.097 Si1.062OH6.372(CO3)0.994(SO4)1.000·11.596 H2O. Unit cell parameters (a=11.013(2) Å,c=10.379(5) Å,V=1090.1(6) Å3) and refraction indices (ne=1.458(2),n
o=1.498(2)) compare well with the best ones available in the literature. The IR spectrum and DT-TG profiles are given. Contradictions between the IR spectrum, a recent structural refinement and the DT-TG are discussed, but cannot be explained satisfactorily.
With 2 Figures 相似文献
Thaumasit aus der Mangan-Mine von Tschwinning, Süd-Afrika
Zusammenfassung Thaumasit aus der Mangan-Mine von Tschwinning, Süd-Afrika, besitzt die Formel Ca3.097 Si1.062OH6.372(CO3)0.994(SO4)1.000·11.596 H2O. Die Parameter der Elementarzelle (a=11.013(2) Å,c=10.379(5) Å,V=1090.1(6) Å3) und die Brechungsindizes (n e=1.458(2),n o=1.498(2)) zeigen gute Übereinstimmung mit verfügbaren Literaturdaten. Es werden ein IR-Spektrum und DT-TG-Profile präsentiert. Gegensätze zwischen dem IR-Spektrum, einer neueren Strukturverfeinerung und dem DT-TG werden diskutiert, können jedoch nicht zufriedenstellend erklärt werden.
With 2 Figures 相似文献
3.
R-mode technique factor analysis, performed on as many as 186 garnet and 103 omphacite samples from eclogites of known geological setting, confirms the three-group partition given by Smulikowski (1964, 1965) and Coleman et al. (1965), and lends support to the interpretation of eclogites as rocks formed under a wide range of P-T conditions both in the metamorphic and in the igneous realm. 相似文献
4.
Dr. A. Mottana W. R. Church A. D. Edgar 《Contributions to Mineralogy and Petrology》1968,18(4):338-346
An eclogite and five of its coexisting minerals (omphacite, garnet, carinthine, kyanite and zoisite) from the probable type locality of eclogites (Kupplerbrunn, Saualpe, Austria) described by Haüy (1822) have been analysed. Optical and X-ray data for these minerals are also given. Comparison of the Kupplerbrunn rock with those of other eclogites from the Saualpe region indicates they all have roughly similar compositions. When plotted on an A-C-F diagram the majority of these analyses fall in the region of kyanite-bearing eclogites suggested by Tilley (1936) although the Kupplerbrunn rock is the only sample containing kyanite; the others containing zoisite. The garnet and omphacite compositions of the Kupplerbrunn rock differ markedly from those of other Saualpe eclogites, possibly due to different metamorphic conditions of their formation. Carinthine analyses are all very similar for eclogites from Saualpe. On the basis of geological, analytical and limited experimental evidence, it is postulated that the Kupplerbrunn eclogite was derived from an original gabbroic rock low in water content such that amphibole and zoisite formed from plagioclase, pyroxene and water; omphacite, garnet and kyanite formed from plagioclase and pyroxene, once all the water was used up in the form of amphibole and zoisite. These reactions are believed to have taken place at 5–8 kb pressure at around 600° C; a value close to that suggested by Lodemann (1966) from field data. 相似文献
5.
The polymorphic transformation between synthetic pyroxmangite and rhodonite of MnSiO3 composition has been reversibly bracketed in the presence of water at 3 kbar (between 425 ° and 450 ° C), 6 kbar (between 475 ° and 525 ° C), 20 kbar (between 500 ° and 900 ° C), 25 kbar (between 800 ° and 900 ° C) and 30 kbar (between 900 ° and 1,000 ° C), using standard cold-seal pressure vessels and piston cylinder apparatus. Oxygen fugacities buffered by the bomb walls and piston-cylinder cell assemblies sufficed to keep manganese in the divalent state. Pyroxmangite of MnSiO3 composition is shown to be the high-pressure, low-temperature polymorph with respect to rhodonite of the same composition. It is a stable phase at atmospheric pressure below 350–405 ° C.X-ray data for synthetic pyroxmangite are presented. The unit-cell parameters (a0=6.717(2) Å, b0=7.603(1)Å, c0=17.448(5) Å, =113 °50(1), = 82 °21(2), =94 °43(1); space group P-1) give a unit-cell volume (807.5(0.3) Å3) which, in accordance with other recent least squares lattice refinements of hydrothermally synthesized material, is slightly smaller than that obtained by single-crystal work on anhydrously synthesized material.Application of the present results to natural rocks is severely restricted due to the great variety and extent of cationic substitutions observed in natural pyroxenoids. The univariant polymorphic transformation determined for the MnSiO3 composition is thus replaced in natural systems by a divariant field in which pyroxmangite and rhodonite of differing composition will stably coexist. 相似文献
6.
An omphacite from the Nybø eclogite pod, Norway, has a chemical composition which plots within the gap, often regarded as a miscibility gap, which is evident in all previous compilations of natural jadeite-rich acmite-poor omphacite compositions. Its cation site populations determined by crystal structure refinement accord well with its chemical composition analysed by electron microprobe. Its disordered space group C2/c symmetry extends the known compositional range of C2/c pyroxene. The postulated miscibility gap is regarded as real and wide at low temperatures, but it appears to narrow with increasing temperature or ultimately with increasing acmite proportion. The adjacent primitive symmetry field appears to initially widen with increasing temperature or increasing acmite proportion, at the expense of the diminishing miscibility gap, before finally closing with further increase. 相似文献
7.
Fe (136,900 ppm)- and Ti (28,540 ppm)-rich eclogites contained in the Voltri serpentinites show contents of metallic trace elements different from those of other eclogites described so far, both those of ophiolitic type and those included in ultramafic rocks. The Voltri eclogites are enriched in Mn (1,894 ppm), V (610 ppm), and Co (75 ppm) and depleted in Cr (110 ppm), Ni (56 ppm), and Zr (46 ppm) in comparison with other occurrences. The analyzed samples are: twelve flaser-eclogites, four fine-grained bimineralic eclogites and three eclogites showing an advanced degree of retrometamorphism toward greenschist facies. The given average values (in ppm) are based on nineteen analyzed samples. This trace-element content is believed to reflect the highly fractionated tholeiitic character of the eclogites and suggests that the Voltri rocks originated from the isochemical metamorphism of ferrogabbros which were probably intruded into the serpentinized lherzolites of a mid-oceanic ridge at the time of the opening of the Pennidic trough. 相似文献
8.
9.
Simone Recchi Francesca Matteucci Annibale D'Ercole Monica Tosi 《Astrophysics and Space Science》2003,284(2):623-626
We study the effect of different star formation regimes on the dynamical and chemical evolution of Blue Compact Dwarf galaxies.
To do that, we adopt a 2-D hydrocode coupled with detailed chemical yields originating from SNeII, SNeIa and from intermediate-mass
stars. We apply this kind of simulation to a model of galaxy resembling IZw18.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
10.
Ten samples of blueschist facies eclogites occurring as dykes in the ultramafic rocks of the Voltri Group were analysed for eigth rare earth elements (REE). Their patterns are clearly different from those of cognate eclogites enclosed in ultramafic rocks and similar to those of the volcanic rocks dredged from the Mid-Atlantic Ridge (MAR). This similarity confirms both the tholeiitic nature of the magma injected into the Pennidic oceanic basement and metamorphosed to eclogite, and the immobile character of REE during metamorphism up to 10 Kbar and 450°C. Depletion of LREE vs HREE and a positive Eu anomaly in the coarse-grained central portions of the former dykes suggest their derivation from a mush consisting of pyroxene and plagioclase plus trapped superferrian liquid. The high total REE content and the flat pattern of the fine-grained eclogites occurring at the borders of the dykes are consistent with their derivation from a rapidly crystallized superferrian liquid. 相似文献