首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 812 毫秒
1.
Measuring strain from deformed xenoliths is problematic due mainly to the large initial shape variations of these markers. A method is described which allows mean initial shape to be determined for a number of xenolith populations by displaying their logarithmic ranges (log Rfmax — log Rfmax) on a Range diagram. The diagram contains a check on validity and allows bad samples to be recognised. Xenolith data from a deformed granite in northwest Ireland is analysed using the method.  相似文献   

2.
Hard mode Raman Spectroscopy and optical birefringence studies have been used to evaluate the temperature behaviour of order parameters for the cubictetragonal phase transition in leucite. There is a strong temperature-dependence of Raman line frequencies near 498 cm–1 and 529 cm–1, and the optical birefringence decreases towards zero on heating. Above the transition temperature leucite still shows slight birefringence, which correlates with the persistence of the 200 X-ray reflexion at these temperatures, and is not compatible with the ideal cubic symmetry. Quantitative observations of the temperature evolution of Raman line-frequencies and the birefringence are consistent with an order parameter showing T 1g symmetry, and a nearly-tricritical phase transition behaviour. The results of earlier X-ray and DSC studies imply the operation of an additional order parameter, with E g symmetry; this is observed, but its influence on the transition behaviour is significant only at temperatures close to T c. The two order parameters are related via linear-quadratic or biquadratic coupling. We develop the form of the Landau Potential for leucite — including both order parameters and their couplings — to discuss the present observations and previous structural data.  相似文献   

3.
Based on studies of images obtained from LANDSAT-1 and 2, several seemingly active movement zones have been delineated in a section of the eastern Alps and are being reported in the present paper for the first time. These zones, trending W—E to NW—SE, cut across all earlier Alpine boundaries and contacts and on either side along their length, are marked with drag effects, indicating their post-Alpine neotectonic nature. Their relation with the present-day central European stress field, as determined from fault-plane studies and in-situ stress measurements, has been sought. In conjunction with the evidence from neighbouring areas, a dextral shear tendency of the present-day Mediterranean is indicated. Further, a number of extensive lineaments have been observed in the Alpine section. Statistically, there are three major lineation sets trending N45°, N15°, N345°. They appear to have developed cogenetically as a result of shear and tensile failures due to a stress field with maximum principal stress oriented averagely at N15°. This direction of the maximum principal stress, deduced from the above lineation analysis of the eastern Alps, is in striking conformity with the one believed to have been in existence for the development of the Rhinegraben (N20°). It appears that the Rhinegraben and the Alpide belt have evolved cogenetically and concurrently under the same dominant stress field (P1 = N—NNE, P2 = vertical and P3 = E—ESE) and hence the two geotectonic features are really not antagonistic and mutually incompatible as usually believed on the grounds that one involves tension (taphrogenesis — Rhinegraben) and the other compression (orogenesis — Alpide belt) but are different manifestations of the same stress field. Besides, some additional light has been thrown on the possible controls of development of the Giudicaria Line and cause of predominance of NE—SW trending sinistral faults.  相似文献   

4.
The petrochemistry of kimberlites from Yakutia and Lesotho has been studied using a silicate melt model with the SiO2, CO2 and H2O derivatives as the main anions.A model has been developed, according to which the dissolution of H2O in an ultramafic melt results in orthosilicates (H2SiC 4 -2 , H3SiO 4 – , H4SiO4 etc.) rather than metasilicates, while the dissolution of CO2 produces additional hydrocarbonate complexes. It suggests that at high PCO 2 1 , and where the orthosilicic calcium salt clusters are likely to be present in the magma, the kimberlite melt can break down into carbonate and silicate liquids. Therefore, the composition of kimberlite magma will be determined by the H2O/CO2 ratio under the relatively constant fluid pressure. This can be seen from the distinct fluidrs trend in the H2O-CO2-SiO2 diagram for the Yakutia and Lesotho diamond-bearing kimberlites. The H2O/CO2 ratio changes with the liquidus temperature along this trend (Perchuk and Vaganov 1977) which suggests that liquid immiscibility predominates over the simple CO2 solubility in the melts of kimberlite composition. The well-known Boyd's diagrams for the equilibrium PT-conditions in peridotites have been applied along with new experimental data to natural Cpx and Opx, and the PT-parameters were correlated for peridotite inclusions in kimberlite pipes in Yakutia and Lesotho. The liquidus temperatures for the extrapolated area of these correlations gave depths (pressures) at which kimberlite magmas are formed (200–250 km).The hypothesis on SiO2 partitioning between the melt and the fluid was used to calculate the composition of dry initial kimberlite which characterised the average mantle composition: SiO2 — 45.12; TiO2 — 2.49; Al2O3 — 3.58; Cr2O3 — 0.12; FeO — 9.32; MnO — 0.16; CoO — 0.11; MgO — 23.47; CaO — 13.44; Na2O — 0.20; K2O — 1.12; P2O5 — 0.69; S — 0.18; sum — 100 wt.%. This kimberlite is close to wehrlite in composition.  相似文献   

5.
The results of the study of optical properties of 13 anthracites from different parts of the world are presented in this paper. Measurements of reflectance values were made on non-oriented vitrinite grains for a minimum of 300 points per sample. The reconstruction of Reflectance Indicating Surfaces (RIS) were made by Kilby's method [Kilby, W.E., 1988. Recognition of vitrinite with non-uniaxial negative reflectance characteristics. Int. J. Coal Geol. 9, 267–285; Kilby, W.E., 1991. Vitrinite reflectance measurement — some technique enhancements and relationships. Int. J. Coal Geol. 19, 201–218]. It was found that the use of Kilby's method for strongly anisotropic materials like anthracites did not give unambiguous results. Some improvement in Kilby's method, consisting of the division of the cumulative cross-plot into several elemental components, is suggested. Each elemental cross-plot corresponds to a textural class of anthracite, which is characterized by the values of RIS main axes RMAX(k), RINT(k) and RMIN(k) (k=1,2,…n; n — number of classes). The global texture of anthracite is characterized as a RIS with main axes calculated as the weighted means of , and for each class of this anthracite.The division of cumulative Kilby's cross-plot on elemental components makes possible the calculation of new coefficients Ht and H10 characterizing the heterogeneity of the structure and texture of anthracites. The results of our study show that all anthracites have biaxial negative textures, but their heterogeneity varies in a wide range of Ht and H10 coefficients depending upon the individual coal basin.  相似文献   

6.
A new method to determine stress directions using the preferential orientation of plagioclase mechanical twins has been applied to high-temperature mylonitic rocks from the Além Paraíba shear zone, Ribeira fold belt, southeastern Brazil. We have measured the lattice-preferred orientation of plagioclase grains and calculated the orientation of the stress axes possible for the observed twin orientations. The maximum compressive stress direction (σ1), determined for all studied samples, is a function of the mechanical twin orientations of a number of distinct plagioclase populations. The σ1 direction is generally subperpendicular to the (010) plane. The statistical treatment for most of the plagioclase grains examined for each sample shows that σ1 is almost perpendicular to the foliation plane, suggesting a significant coaxial component in the deformation process of these rocks.  相似文献   

7.
In the Mt. Franks area of the Willyama Complex, microfabric evidence suggests that the alteration of andalusite to sillimanite has taken place by a process similar to that suggested by Carmichael (1969). Andalusite is pre- to syn-S2 in age. Alteration to “sericite” has resulted in the formation of “sericite” laths, some of which are crenulated about S2, and some which are syn- and post-S2. “Fibrolite” occurs in these andalusite—“sericite” aggregates within the sillimanite zone and is wholly embedded in “sericite”. “Fibrolite” is pre- to syn-S2 in age. This evidence is interpreted as suggesting that the formation of sillimanite from andalusite took place via a “sericite” phase.Further microfabric observations are interpreted to imply constant volume for the reaction aluminosilicate → “sericite”. This suggests a situation in which Al3+ is relatively mobile but Al4+ is relatively immobile. This suggestion differs from Carmichael's (1969) idea of Al3+ immobility.  相似文献   

8.
Geodetic networks are designed to obtain data that can be used to monitor crustal movements. The relative position on the earth's surface is determined from these networks by means of coordinates. The coordinates of stations and its variance—covariance matrix are based on the computational model. In spatial networks at least three points, the base points, should be chosen to define the coordinate system “fixed” to the earth. In monitoring crustal movements these base points are considered to be stationary over the time span of the motion involved. A procedure for testing the stability of the base points, together with other stable points, is described.The coordinate differences between two time epochs, t0 and t1 are considered to investigate crustal movements. A statistical test is introduced to determine whether crustal movements have actually occurred.The reliability, i.e., the influence, of nondetected errors in the observations or computations, should be considered. Two types of decisions can be made which may lead to incorrect conclusions. These conclusions are as follows:
1. (1) That no movement has taken place, although a nondetected error leads to the opposite conclusion.
2. (2) That a movement has occurred, although a nondetected error in the observations leads to the opposite conclusion.
The chance of arriving at these conclusions can be computed. Boundary values for assumed crustal motion in specified latitudinal and longitudinal directions give a better insight into the desired specifications for geodetic networks.The testing procedure and the above-mentioned method of computing boundary values can be used for all types of networks e.g., those obtained by conventional triangulation or by a satellite-borne ranging system.  相似文献   

9.
Aluminous parageneses containing gedrite, cordierite, garnet, staurolite, biotite, sillimanite, kyanite, quartz or spinel plus corundum are found as dark colored lenses in the polymetamorphic, multideformed Archean complex at Ajitpura in northwest peninsular India. Staurolite, like kyanite, is a relict phase of earlier metamorphism and is excluded as a paragenetic mineral in view of its incompatibility with quartz and gedrite and its lower X Mg values than for garnet of the assemblage. Its stability here is attributed to zinc content of up to 3 wt%. The XMg in other ferromagnesian minerals decreases in the order: cordierite, biotite, gedrite, garnet, as found elsewhere in high grade rocks.The textural criteria and systematic partitioning of Fe and Mg in the ferromagnesian phases, excluding staurolite, indicate attainment of equilibrium during the second metamorphism. From tie line configurations in the phase diagrams, X Mg ratios in the constituent minerals, and other petrographic criteria, it is suggested that gedrite — cordierite-garnet — sillimanite — biotite assemblage has been produced by the reactions: Biotite+Sillimanite+Quartz = Cordierite+Garnet+K-feldspar+Vapor (1) and Biotite+Sillimanite+Quartz = Cordierite +Gedrite+K-feldspar+Vapor (2) which occurred during partial melting of the rocks at fixed P and T conditions.By isothermal P-X(Fe-Mg) sections it has been demonstrated that release of FeO, SiO2 and other components modified the composition of the reactant biotite presumably by the substitution FeSi2 Al, whereby reaction 1 was replaced by reaction 2. Cordierite with higher X Mg was produced with gedrite instead of with garnet, whose X Mg is less than X Mg of gedrite. Reaction 2 has been tentatively located in T-P space from the intersection of some continuous loops in the P-X(Fe-Mg) diagram at 700°C and also by other constraints. The discontinuous reaction 2 is located about 1–2 kilobars higher than reaction 1, which implies that it is difficult to distinguish between effects of pressure and those of melting on the X Mg ratios of the reaction phases.The P-T calibrations of garnet — cordierite, garnet — biotite and garnet — plagioclase equilibria and the calibrations from other dehydration curves give temperatures near 700°C and pressure (assuming ) about 6 kilobars.  相似文献   

10.
  相似文献   

11.
The association between constant-sum variables Xi and Xj expressed as percentages can be calculated as a product-moment correlation between Xi and Xj/(100 – Xi ) and a correlation between Xj and Xi/(100 – Xj ). An asymmetric, square matrix may be formed from these coefficients, and multivariate analysis performed by two methods: singular value decomposition and canonical decomposition. Either analysis avoids problems in the interpretation of correlation coefficients determined from closed arrays, and provides information about dependencies among the variables beyond that obtained from the usual correlation coefficient between Xi and Xj.Two examples show the canonical decomposition to have the greater usefulness.  相似文献   

12.
Structural overprinting relationships indicate that two discrete terranes, Mt. Stafford and Weldon, occur in the Anmatjira Range, northern Arunta Inlier, central Australia. In the Mt. Stafford terrane, early recumbent structures associated with D1a,1b deformation are restricted to areas of granulite facies metamorphism and are overprinted by upright, km-scale folds F1c), which extend into areas of lower metamorphic grade. Structural relationships are simple in the low—grade rocks, but complex and variable in higher grade equivalents. The three deformation events in the Mt. Stafford terrane constitute the first tectonic cycle (D1-D2) deformation in the Weldon terrane comprises the second tectonic cycle. The earliest foliation (S2a) was largely obliterated by the dominant reclined to recumbent mylonitic foliation (S2b), produced during progressive non-coaxial deformation, with local sheath folds and W- to SW-directed thrusts. Locally, (D2d) tectonites have been rotated by N—S-trending, upright (F2c) folds, but the regional upright fold event (F2d), also evident in the adjacent Reynolds Range, rotated earlier surfaces into shallow-plunging, NW—SE-trending folds that dominate the regional outcrop pattern.The terranes can be separated on structural, metamorphic and isotopic criteria. A high-strain D2 mylonite zone, produced during W- to SW-directed thrusting, separates the Weldon and Mt. Stafford terranes. 1820 Ma megacrystic granites in the Mt. Stafford terrane intruded high-grade metamorphic rocks that had undergone D1a and D1b deformation, but in turn were deformed by S1c, which provides a minimum age limit for the first structural—metamorphic event. 1760 Ma charnockites in the Weldon terrane were emplaced post-D2a, and metamorphosed under granulite facies conditions during D2b, constraining the second tectonic cycle to this period.Each terrane is associated with low-P, high-T metamorphism, characterized by anticlockwise P—T—t paths, with the thermal peaks occurring before or very early in the tectonic cycle. These relations are not compatible with continental-style collision, nor with extensional tectonics as the deformation was compressional. The preferred model involves thickening of previously thinned lithosphere, at a stage significantly after (>50 Ma) the early extensional event. Compression was driven by external forces such as plate convergence, but deformation was largely confined to and around composite granitoid sheets in the mid-crust. The sheets comprise up to 80% of the terranes and induced low-P, high-T metamorphism, including migmatization, thereby markedly reducing the yield strength and accelerating deformation of the country rocks. Mid-crustal ductile shearing and reclined to recumbent folding resulted, followed by upright folding that extended beyond the thermal anomaly. Thus, thermal softening induced by heat-focusing is capable of generating discrete structural terranes characterized by subhorizontal ductile shear in the mid-crust, localized around large granitoid intrusions.  相似文献   

13.
A general method to calculate phase diagrams from the fundamental crystallographic properties has been suggested, using the calcite-aragonite reaction as an example. This procedure requires the measurement of the phonon spectra at different temperatures and pressures, calculation of a reasonable Grüneisen parameter to obtain C p values from the C v values and the consideration of the order—disorder phenomena and its contribution to the Gibb's energy. The remarkable agreement seen between the calculated diagram and that determined experimentally speaks for the reliability of this method.  相似文献   

14.
In contrast to Ferry (1980) (X Ca)-values in garnet even lower than 0.1 have a significant effect on the calculated equilibrium temperature using the experimental calibration of the Fe and Mg paritioning between garnet and biotite. Garnet compositions and Mg/Fe — distribution coefficients from samples of the Eoalpine staurolite — in zone in the southern Ötztal are related by the quadratic regression equation: InK D= -1.7500 (±0.0226) + 2.978 (±0.5317)X Ca Gt -5.906(±2.359)(X Ca Gt )2 Temperatures derived by the Ferry and Spear (1978) calibration using chemistry — correctedK D values are petrologically realistic.Analysis of our data supports non ideal mixing of grossular with almandine — pyrope solid solution. The derived excess mixing energies are quite small for the almandine — pyrope solution (W FeMg= –133 cal/mole) and about +2775 cal/mole for the difference between pyrope-grossular and almandine-grossular solutions (W MgCa —W FeCa) at metamorphic conditions of 570° C and 5,000 bar. The mixing parameters proposed by Ganguly and Saxena (1984) are not confirmed by our data as they would result in significantly lower temperatures.  相似文献   

15.
Some of the upper cretaceous sedimentary rocks near Regensburg, Germany, are rich in glauconite pellets of 63–200µ diameter. The clay fractions < 2µ of the same rocks are rich in glauconite-mica too.X-ray analysis, chemical analysis and petrographical tests show that, the glauconite pellets must be excrements of marine animals which took up glauconite-mica from sea-bottom.The glauconite materials from these rocks are 1M-micapolymorphs. A comparison of this glauconite with 1M-glauconites cited in literature by other authors shows close aggreement in K2O/MgO- and K2O/Fe2O3 ratios. Within the range of analytical errors the structure formulae of all these 1M-glauconites differ from one another only by the oxidation ratio of iron and — corresponding to this ratio — by the aluminum contents of the octahedral lattice layer. The differences of the 1M-glauconites in octahedral layer populations may due to different redox potentials during glauconite formation or to oxidation during rock diagenesis or rock weathering later on.In a similar manner 1Md-polymorphs of glauconite-mica may have developed from 1M-glauconite by oxidation of iron and corresponding removement of K+ and (H3O)+ ions from interlayer lattice positions.  相似文献   

16.
To simulate geological models comprising several litho-types—or facies—we need first to estimate their proportions, which are often poorly known. The corresponding uncertainties can be modelled using a Bayesian approach for inverting the multinomial distribution. The result obtained is known as the Dirichlet distribution. It can be simulated by decomposition into independent conditional distributions. Application of the model is extended to the case of nonstationary proportions and, with some approximation, to the case of correlated spatial data. The mathematical developments presented in the appendices provide a more precise and general definition of the distribution, several decomposition formulae into independent variables, the determination of remarkable stability properties, and the resulting consequences for the conditional and marginal distributions.  相似文献   

17.
Strong tectonic earthquakes within the crust always occur on already existing faults, and they have the property of a shear rupture. Such earthquakes with surface-wave magnitudes M < 7 obviously have a geometric similarity. Because of this similarity and the validity of the Gutenberg and Richter's energy—magnitude relation, the expression M = 2 log10 L + const., with L = focal length, is valid.The expression LmaxL* for the maximum focal length, is also valid if L* is the length of the rectilinear extent of the seismic line on which the maximum earthquake occurs. The bounds of L* may be given by sharp bends and/or by traversing deep faults. Thus the maximum imaginable earthquake on a seismic line with the length L* has the magnitude Mmax = 2 log10 L* + const.For the investigated region — the Alps and adjacent areas — from the data of recent and historical strong earthquakes, it follows that Mmax = 2 log10 L* + 1.7, if L* is measured in kilometres. These limiting values lie in the centre-field of the magnitude range for maximum earthquakes, published by Shebalin in 1970. By the aid of this equation it is also possible to assess the upper limiting value of the accompanying maximum scale intensity.  相似文献   

18.
Hydrometallurgical processing of spent hydrodesulphurisation (HDS) catalyst for the recovery of molybdenum using sodium carbonate and hydrogen peroxide mixtures was investigated. The results indicated that the recovery of molybdenum was largely dependent on the concentrations of Na2CO3 and H2O2 in the reaction medium, which controls the acidity of the leach liquor and carry over of impurities such as Al, Ni, P, Si and V. Leaching process was exothermic and leaching efficiency of molybdenum decreased with increasing solid to liquid ratio. Large scale leaching of spent catalyst, under optimum conditions: 20% pulp density, 85 g/L Na2CO3, 10 vol.% H2O2 and 1 h reaction, resulted a leaching efficiency of 84% Mo. The obtained leach liquor contained (g/L): Mo — 22.0, Ni — 0.015 and Al — 0.82, P — 1.1, Si — 0.094 and minor quantities of V — 8 mg/L, As and Co — < 1 mg/L. Recovery of Mo from leach solution as MoO3 of 97.30% purity was achieved by ammonium molybdate precipitation method.  相似文献   

19.
The genetic population structure of winter flounder larvae was examined in Narragansett Bay, RI. Winter flounder larvae collected from 20 stations within Narragansett Bay and one station outside of the Bay were analyzed for six microsatellite loci. When analyzed by geographic collection sites, there were 16 distinct genetic populations of winter flounder larvae (R ST values from 0.1 to 0.6). The presence of distinct genetic populations was supported by assignment of individual larvae to populations by Bayesian analysis. Bayesian analysis resulted in 14 distinct genetic populations that overlapped with the geographically distributed populations (R ST values from 0.1 to 0.6). Young-of-the-year juveniles collected in the same year as the larvae were also analyzed at the same six microsatellite loci. Juveniles were assigned to larvae populations by both a Bayesian approach and a neural network approach. Juveniles collected from within Narragansett Bay were found to arise from geographically adjacent Narragansett Bay winter flounder larval populations (>99%), suggesting no widespread movement of juveniles away from spawning grounds. These results are discussed in the context of winter flounder population biology in Narragansett Bay, RI.  相似文献   

20.
The seismicity of Uganda has been studied using new data and all other available, previously determined locations of earthquakes (mb 4.0) up to December 1973. A magnitude—frequency graph suggests that since 1963 there is nearly complete coverage of all events with body magnitudes mb 4.2 in Uganda. The distribution of the earthquakes affirms that the Lake Amin—Lake Mobutu region experienced the greatest number of earthquakes, while the area around the Ruwenzori Mountain is probably the most seismically active area in Uganda if not in East Africa. The occurrence of earthquakes and the presence of faults of Cenozoic age in the Ruwenzori fold belt indicate that this area is a tectonically active zone (zone of weakness) probably connecting the eastern and western rifts across the Lake Victoria basin.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号