排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
Ultrahigh pressure macro diamonds from Copeton (New South Wales, Australia), based on Raman spectroscopy of inclusions 总被引:1,自引:0,他引:1
Mining of Cenozoic alluvial deposits at Copeton and Bingara (Eastern Australia) has produced two million macrodiamonds (0.25 ct median size). Raman spectroscopy is used to identify included minerals within uncut Copeton diamonds, with sealed chamber remnant pressures of 31.7 to 35.6 kbar for coesite, 13.6 and 22.7 kbar for clinopyroxene, and 7.6 kbar for grossular garnet. Assuming elastic behaviour, these values generate inclusion entrapment PT loci which intersect, restricting diamond formation conditions: from 250 °C, 43 kbar to 800 °C, 52 kbar. Larger than error (± 100 °C and ± 4 kbar), this range shows a systematic variation in inclusion composition with diamond zoning and N properties. Published research shows 1) Copeton and Bingara diamonds are unique, and 2) modern alluvium in the Bingara district carries mantle-formed garnet, captured by post-tectonic alkali basalt from an extensive diamondiferous ultrahigh pressure (UHP) terrane that stalled at depth because it is dominated by mafic eclogite. The combined Raman and geological results indicate two sets of subduction UHP diamond formation conditions/protolith are required, firstly cooler oceanic slab and secondly including higher temperature continental crust. The Copeton and Bingara stones are UHP macrodiamonds, and Carboniferous 40Ar/39Ar age dates on clinopyroxene inclusions should be interpreted as ages of crystallisation, representing the termination of subduction. The characteristic features of ruptured inclusions and etched percussion marks on Copeton and Bingara diamond indicate volcanic delivery to the earth's surface. Alluvial deposits elsewhere in Eastern Australia may carry similar diamond along with diamond of different origin. 相似文献
2.
Raman spectra of diopside were collected from atmospheric pressure to 71 GPa. The pressure dependences of 22 modes were determined.
Changes occurred in the spectra at three different pressures. First, at approximately 10 GPa, the two Raman modes at 356 and
875 cm−1 disappeared, while the mode at 324 cm−1 split into two modes, diverging at this pressure with significantly different pressure shifts; second, at approximately 15
GPa, a small (1 to 2 cm−1) drop in several of the frequencies was observed accompanied by changes in the pressure dependency of some of the modes;
and third, above 55 GPa, the modes characteristic of chains of tetrahedrally coordinated silicon disappeared, while those
for octahedrally coordinated silicon appeared. The first change at 10 GPa appears to be a C2/c to C2/c transition involving a change in the Ca coordination. The third change above 55 GPa appears to be a change in the silicon
coordination. At 15 GPa, it is suggested that a change in compressional mechanism takes place.
Received: 14 November 2000 / Accepted: 9 January 2002 相似文献
3.
Microindentation hardness tests were performed on jadeite and diopside, being end members of the omphacite solid solution series. At temperatures between 300 and 750 °C, the hardness of jadeite ranges from 7.4 to 8.5 GPa, that of diopside from 4.9 to 6.1 GPa. Jadeite is significantly stronger than diopside in the low-temperature plasticity regime. Normalization of the hardness-derived yield stress with respect to the shear modulus considerably reduces the strength contrast. The normalized Peierls stress is identical for jadeite and diopside. This indicates that jadeite and diopside belong to the same isomechanical group. The hardness-derived yield stress for jadeite as well as for diopside is used to estimate flow law parameters for the low-temperature plasticity regime. 相似文献
4.
Nuclear reaction analyses on boron in flux-grown Me3+- and Na+-doped diopside crystals utilising the 11B(p,2α)4He reaction in conjunction with EMP analyses for major elements and optical absorption spectroscopy for determination of Me-valence
state distributions show that appreciable amounts of B may enter the diopside lattice in crystals produced in Na2B4O7 fluxes. The results indicate that the substitution [6]Me3+[4]B3+[6]Mg2+
−1
[4]Si4+
−1 operates in the present diopside samples in addition to the coupled substitution [6]Me3+[8]Na+[6]Mg2+
−1
[8]Ca2+
−1. The specific NRA technique applied allows for quantitative, high resolution (ca. 5 μm) B analyses at ppm level as well as
high-resolution and high-contrast imaging of B-concentration patterns in minerals. The estimated detection limit and relative
error of the B analyses are 10 ppm and 5–10%, respectively.
Received: 20 September 1999 / Accepted: 6 June 2000 相似文献
5.
A series of synthetic Ca-Tschermak–diopside (CaAlAlSiO6–CaMgSi2O6) clinopyroxenes were investigated by powder infrared spectroscopy at room temperature in the wavenumber range 80–2,000 cm−1. Measurable local structural heterogeneities in the crystals are suggested by the line broadening parameter, Δcorr that are
observed for intermediate solid-solution compositions. The broadening is most pronounced in the high wavenumber region of
the IR spectra that contains stretching modes involving the TO4 polyhedra. The effective line widths for three selected wavenumber regions deviate positively from linear behavior. This
is also observed for the enthalpy of mixing of this solid solution. The relationship between “excess Δcorr”, δΔcorr, and heat
of mixing, ΔH
mix, behavior was investigated for this clinopyroxene series and for several other binary silicate solid solutions. The ΔH
mix versus δΔcorr slope values show a linear relationship with respect to the integrated excess volume of the various solid solutions. 相似文献
6.
透辉石,透闪石矿床成矿条件及找矿方向 总被引:2,自引:0,他引:2
在国内透辉石、透闪石矿床地质调研基础上,提出我国该类矿床的四种成因类型:区域变质型、接触热变质型、接触交代(矽卡岩)型和基性—超基性岩浆岩型。并探讨了除岩浆岩型矿床以外的各类型矿床成矿地质条件及找矿方向。 相似文献
7.
The right-rectangular parallelepiped resonance (RPR) form of resonant ultrasound spectroscopy (RUS) is applied to monoclinic crystal symmetry to determine the 13 adiabatic elastic constants, Cij, of single-crystal chrome-diopside Di0.93Hd0.03Ur0.02X0.02 (Di, diopside; Hd, hedenbergite; Ur, ureyite; X, other or unknown). These data represent the first published values of the elastic tensor for a monoclinic single-crystal determined by the RPR method, thus demonstrating the feasibility of this method for studying elasticity of low-symmetry crystals. The lowest 62 modal frequencies of a gem-quality specimen were measured and identified at ambient temperature and pressure. Inverting the modal frequencies results in, respectively C11, C22, C33, C44, C55, C66, C12, C13, C23, C15, C25, C35, C46 values (GPa) of 228.1(1.0), 181.1(0.6), 245.4(1.3), 78.9(0.3), 68.2(0.2), 78.1(0.2), 78.8(0.5), 70.2(0.7), 61.1(0.7), 7.9(0.5), 5.9(0.5), 39.7(0.4), and 6.4(0.2), where numbers in parentheses indicate experimental uncertainty. The corresponding isotropic bulk, KS, and shear, G, moduli are 116.5 (0.9) and 72.8(0.4) GPa, respectively. When comparing these results with other pyroxene data, we find systematic correlations between M2 site composition and Cij values for most, but not all, moduli. Unusual compositional dependence near end-member diopside is seen for a few moduli, and is propagated to the KS and G moduli, which should prompt a reexamination of some Cij values of end-member diopside. 相似文献
8.
Atomistic computer simulation techniques have been employed to model mechanisms of hydrogen incorporation in the clinopyroxenes diopside and jadeite. Calculation of solution reaction energies for the pure phases indicates that hydrogen is most easily incorporated via the formation of [VSi(OH)4]
x
hydrogarnet type defects. When components of the two phases are mixed, then solution energies can become exothermic. The substitution of Al for Si in diopside and of Mg or Ca for Al in jadeite, provides favourable routes for hydrogen incorporation, with exothermic values of solution energy. Thus the amount of water present in these minerals in the Earth’s upper mantle will vary with composition. Simulation of IR frequencies associated with O–H stretching at specific defect clusters has also been carried out. An analysis of hydrogen–oxygen bond lengths gives good agreement, although comparison of experimental and calculated IR frequencies are problematic. This is partly due to the complexity of experimental spectra, but may also be due in part to deficiencies in the ability of the model to accurately describe the O–H stretching frequency. 相似文献
9.
Values of the complete adiabatic elastic tensor for single-crystal chrome-diopside (a monoclinic pyroxene mineral) are presented from 298 to 1,300 K. The data were obtained using resonant ultrasound spectroscopy (RUS). They are the first published results for the temperature T dependences of the 13 individual elastic constants C
ij
of any clinopyroxene mineral. Each C
ij
is appropriately described by a linear function in T throughout the range of T. Values for each (∂C
ij
/∂T)
P
in GPa K−1 are as follows: C
11, −0.0291; C
22, −0.0248; C
33, −0.0179; C
44, −0.0103; C
55, −0.0077; C
66, −0.0152; C
12, −0.0119; C
13, −0.0064; C
23, 0.0000; C
15, 0.0025; C
25, 0.0022; C
35, −0.0046; and C
46, 0.0026. Values of (∂M/∂T)
P
in GPa K−1, where M represents an isotropic bulk property calculated from the C
ij
data, are as follows: adiabatic bulk modulus K
S
, −0.0123; isothermal bulk modulus K
T
, −0.0178; and shear modulus G, −0.00998. Some diopside derivatives, notably (∂K
S
/∂T)
P
, (∂K
T
/∂T)
P
, and (∂V
P
/∂T)
P
, where V
P
is the compressional wave velocity, have smaller magnitudes than all other minerals of importance in Earth’s mantle, thus, confirming predictions from systematics studies. We find several dimensionless quantities for this monoclinic mineral have normal values compared to other mantle minerals. Further, αK
T
(α is the volume coefficient of thermal expansion) for diopside is approximately independent of both T and volume V at elevated temperature, so its equation of state is accurately expressed in simplified form. 相似文献
10.