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1.
E. H. Brown 《Contributions to Mineralogy and Petrology》1977,64(2):123-136
Phase relations of pumpellyite, epidote, lawsonite, CaCO3, paragonite, actinolite, crossite and iron oxide are analysed on an Al-Ca-Fe3+ diagram in which all minerals are projected from quartz, albite or Jadeite, chlorite and fluid. Fe2+ and Mg are treated as a single component because variation in Fe2+/Mg has little effect on the stability of phases on the diagram. Comparison of assemblages in the Franciscan, Shuksan, Sanbagawa, New Caledonia, Southern Italian, and Otago metamorphic terranes reveals several reactions, useful for construction of a petrogenetic grid:
- lawsonite+crossite + paragonite = epidote+chlorite + albite + quartz + H2O
- lawsonite + crossite = pumpellyite + epidote + chlorite + albite+ quartz + H2O
- crossite + pumpellyite + quartz = epidote + actinolite + albite + chlorite + H2O
- crossite + epidote + quartz = actinolite + hematite + albite + chlorite + H2O
- calcite + epidote + chlorite + quartz = pumpellyite + actinolite + H2O + CO2
- pumpellyite + chlorite + quartz = epidote + actinolite + H2O
2.
Gert Hoschek 《Contributions to Mineralogy and Petrology》1974,47(4):245-254
P, T, \(X_{{\text{CO}}_{\text{2}} }\) relations of gehlenite, anorthite, grossularite, wollastonite, corundum and calcite have been determined experimentally at P f =1 and 4 kb. Using synthetic starting minerals the following reactions have been demonstrated reversibly
- 2 anorthite+3 calcite=gehlenite+grossularite+3 CO2.
- anorthite+corundum+3 calcite=2 gehlenite+3 CO2.
- 3anorthite+3 calcite=2 grossularite+corundum+3CO2.
- grossularite+2 corundum+3 calcite=3 gehlenite+3 CO2.
- anorthite+2 calcite=gehlenite+wollastonite+2CO2.
- anorthite+wollastonite+calcite=grossularite+CO2.
- grossularite+calcite=gehlenite+2 wollastonite+CO2.
3.
Monika E. Huch 《International Journal of Earth Sciences》1988,77(3):777-786
The European Geotraverse (EGT) crosses along a 4000 km profile from the North Cape to Tunisia the following main suture zones: the Tornquist-Teisseyre zone between the Baltic Shield and the Variscan realm, the transition zones between Rhenohercynian and Saxothuringian as well as between Saxothuringian and Moldanubian zones in the Variscan part of central Europe, and the collision zone between the European continent and the Adriatic microplate. Some structural aspects of these suture zones are described. 相似文献
4.
Medium-to high-pressure granulite facies complexes represent samples of lower crustal material and are, therefore, important in the study of crustal processes. New rare earth element data for the Scourian granulite facies terrain of the Precambrian Lewisian complex of N.W. Scotland indicate that:
- Overall, the Scourian complex has a light rare earth enriched pattern with a small but distinct positive Eu anomaly;
- While some rare earth element trends for the complex as a whole (e.g., Σ REE vs SiO2) are similar to those observed in upper crustal cogenetic sequences, others (e.g., Eu/Eu* vs SiO2) are reversed;
- Compared to average upper crust, the Scourian complex is depleted in REE (except Eu) by a factor of 2 to 3.
5.
Six lithologic units in tectonic contact with each other have been defined during mapping of the Devonian in the Beaujolais area of the northeastern Massif Central. Five main igneous suites have been recognized:
- A transitional basaltic suite restricted to a single unit.
- An acid volcanic-plutonic suite the members of which are related by fractional crystallization and magma mixing.
- Low-TiO2 volcanic rocks with calc-alkaline affinities.
- A TiO2-rich tholeiitic suite related to an ophiolitic complex.
- A plutonic suite with close resemblances to Alaskantype intrusions.
6.
A. Gandin M. Tongiorgi A. Rau C. Virgili 《International Journal of Earth Sciences》1982,71(3):881-894
In Southwestern Mediterranean Europe (NE Spain, Sardinia and NW Apennines e. g. Monti Pisani and Punta Bianca) the Middle-Triassic transgression on a margin of an intracratonic basin appears to be controlled by the different morphology and tectonic activity of the margin itself. The analysis of some sequences leads to recognize three different kinds of margins:
- margin with a narrow shelf sloping toward a very shallow restricted basin (Central and Southwestern Sardinia);
- margin with a broad shelf gently sloping toward a shallow basin (NE Spain, Monti Pisani, NW Sardinia);
- margin with a narrow shelf and steep slope marked by tectonic and volcanic activity (Punta Bianca).
7.
The P-T path of magma associated with the 1944 Vesuvius eruption has been outlined on the basis of probe mineralogy and the relationships between the crystallising phases. Equilibrium P-T values, obtained from the reactions:
- CaMgSi2O6(liq) = CaMgSi2O6(cpx)
- NaAlSi3O8 (liq) = NaAlSi3O8 (plag)
- CaAl2Si2O8 (plag)=CaAl2SiO6(cpx)+SiO2(liq) have been established for three intracrustal crystallisation stages: I) 8.0 kbar and 1255 °C; II) 4.0 kbar and 1178 °C; III) 0.5 kbar and 1105 °C.
8.
Laihunite Research Group 《中国地球化学学报》1982,1(1):105-114
Laihuite reported in the present paper is a new iron silicate mineral found in China with the following characteristics:
- This mineral occurs in a metamorphic iron deposit, associated with fayalite, hypersthene, quartz, magnetitc, etc.
- The mineral is opaque, black in colour, thickly tabular in shape with luster metallic to sub-metallic, two perfect cleavages and specific gravity of 3.92.
- Its main chemical components are Fe and Si with Fe3+>Fe2+. The analysis gave the formula of Fe Fe 1.00 3+ ·Fe 0.58 2+ ·Mg 0.03 2+ ·Si0.96O4.
- Its DTA curve shows an exothermic peak at 713°C.
- The mineral has its own infrared spectrum distinctive from that of other minerals.
- This mineral is of orthorhombic system; space group:C 2h /5 ?P21/c; unit cell:α=5.813ű0.005,b=4.812ű0.005,c=10.211ű0.005,β=90.87°.
- The Mössbauer spectrum of this mineral is given, too.
9.
Niranjan D. Chatterjee Ludger Terhart 《Contributions to Mineralogy and Petrology》1985,89(2-3):273-284
The system MgO-Al2O3-SiO2(MAS) comprises 88–90% of the bulk composition of an average peridotite. The MAS ternary is thus a suitable starting point for exploring peridotite phase relations in multicomponent natural systems. The basic MAS phase relations may be treated in terms of the reactions (see list of symbols etc).
- py (in Gt)=en (in Opx)+mats (in Opx),
- en (in Opx)+sp (in Sp)=mats (in Opx)+fo (in Ol), and
- py (in Gt)+fo (in Ol)=en (in Opx)+sp (in Sp).
- binary Sp (sp-pc) crystalline solution (Oka et al. 1984),
- ternary Opx (en-mats-mcts) crystalline solution (this study), and
- binary Gt (py-kn) crystalline solution (this study).
- With increasing incorporation of Cr+3 into Sp and Gt, the X mats isopleths of the reactions (1) and (2) are shifted to higher temperatures (Fig. 3a); simultaneously, the spinel-peridotite to garnet-peridotite phase transition is moved to higher pressures (Fig. 3b).
- At identical P and T, the X mats values of Opx coexisting in equilibrium with Ol and Sp is strongly dependent upon the X pc value in the latter phase (Figs. 4a and b). Accurate correction for the composition of Sp is, therefore, a necessary precondition for geothermometry of the spinelperidotites.
- The discrepant temperatures reported by Sachtleben und Seck (1981, Fig. 5) from the spinel-peridotites of the Eifel area (systematically too high temperatures as a function of X pc in Sp) are demonstrated to be the result of ignoring the nonideality in the chromian spinels.
10.
Samples taken from loess and paleosols were examined for carbonate content. The main results were as follows:
- The carbonate content measured differed significantly when the samples were analysed jointly with the concretions occurring in them or separately from these constituents.
- Solubility of different carbonates (calcite, dolomite, aragonite etc.) was found different. This factor also might have influenced the measured total amounts of carbonates.
11.
Bays, lagoons, and estuaries are sites where normal physicochemical processes result in accumulations of sediment and certain chemicals. Changes in water velocity and chemistry, and chemical interactions of sediment, biota, and water are factors that contribute to concentrating trace metals in coastal and lake sediments. To evaluate whether lead concentration is affected by mineralogy, kaolinite, illite, montmorillonite, and a zeolitic tuff were suspended in 10 and 20 mg/l concentrations of lead solutions [Pb(NO3)2] which were pH-adjusted incrementally through a range of 2.5 to 11.0. Samples were centrifuged after 24 hours to separate liquid from suspended sediment. Sediment-free solutions were run as controls. Lead concentrations were determined by atomic adsorption spectrophotometry. Results indicate that montmorillonite (Wyoming Bentonite) particles serve as lead adsorption nuclei over a broad pH range. Maximum sorption occurs as the solution reaches a pH of about 7.5. The kaolinite clay from Georgia strongly adsorbs trace amounts of lead at pH ranging from 3.0 to 4.5, where up to 95 percent of the lead is adsorbed by the clay. Little adsorption difference was found between the Fithian illite clay and zeolitic tuff from the Nevada Test Site in comparison to sediment-free solutions which were pH-adjusted. In concentrations of 10 to 20 mg/l montmorillonite and kaolinite clays serve as nucleation sites capable of adsorbing up to 95 percent of trace concentrations of lead within 24 hours. It appears that accumulations of lead in coastal lake and estuarine sediments are significantly influenced by:
- pH changes which occur as river and coastal waters mix resulting in precipitation of lead, and
- sorption of lead by suspended clays.
12.
Yiyang Zhao 《中国地球化学学报》1982,1(3):338-342
The following conclusions can be drawn from the work reported in this paper:
- Sixteen samples were determined for uranium by spectrophotometric method. The uranium content in the sea floor sediments of the Bohai Gulf ranges from 1.6 to 6.3 ppm, with an average of 4.3 ppm.
- Statistical data show close relationship between U concentration and grain size. Relatively larger amount of uranium was found accumulated in mud than in sand. The bulk of uranium is assumed to be derived from terrestrial detrital minerals.
- A positive correlation between U and Fe is recognized. Similar relation also can be seen between U and Al. The plot of U concentration vs. Fe is linear, and can be expressed by the linear regression equation:Y=?0.37+1.35X. The plot of U against Al gives an equation ofY=?2.48+1.01X.
- The average U/Corg. ratio for these sediments is 7×10?4, and the average ratios of U/P, U/Mn, and U/CaCO3 are 100×10?4, 50×10?4 and 2×10?4, respectively.
- Compared with the abundances of other shelf sediments, the average concentration of U in the area under consideration is close to that of sediments on the selves of Japan and the Gulf of Mexico, and the Black Sea. Uranium concentration in the Bohai Gulf sediments is comparable to that of the continental crust, but differs from that of deep-sea clay.
13.
A number of experimental CO2 solubility data for silicate and aluminosilicate melts at a variety of P- T conditions are consistent with solution of CO2 in the melt by polymer condensation reactions such as SiO 4(m 4? +CO2(v)+Si n O 3n+1(m) (2n+1) ?Si n+1O 3n+4(m) (2n+4)? +CO 3(m )2? . For various metalsilicate systems the relative solubility of CO2 should depend markedly on the relative Gibbs free change of reaction. Experimental solubility data for the systems Li2O-SiO2, Na2O-SiO2, K2O-SiO2, CaO-SiO2, MgO-SiO2 and other aluminosilicate melts are in complete accord with predictions based on Gibbs Free energies of model polycondesation reactions. A rigorous thermodynamic treatment of published P- T-wt.% CO2 solubility data for a number of mineral and natural melts suggests that for the reaction CO2(m) ? CO2(v)
- CO2-melt mixing may be considered ideal (i.e., { \(a_{{\text{CO}}_{\text{2}} }^m = X_{{\text{CO}}_{\text{2}} }^m \) );
- \(\bar V_{{\text{CO}}_{\text{2}} }^m \) , the partial molal volume of CO2 in the melt, is approximately equal to 30 cm3 mole?1 and independent of P and T;
- Δ C p 0 is approximately equal to zero in the T range 1,400° to 1,650 °C and
- enthalpies and entropies of the dissolution reaction depend on the ratio of network modifiers to network builders in the melt. Analytic expressions which relate the CO2 content of a melt to P, T, and \(f_{{\text{CO}}_{\text{2}} } \) for andesite, tholeiite and olivine melilite melts of the form
14.
According to Sakai-Ohmoto's theory regarding the evolution of sulfur isotopes in hydrothermal systems, in conjunction of new data on chemical resaction equilibrium constants and equilibrium isotopic fractionation factors as well as on individual ion activity coefficients of aqueous sulfur species, the following lgfo2.-pH diagrams are constructed:
- mole fractions of aqueous sulfur species (X i ),
- stability fields of some minerals in the Fe-S-O system,
- diagram depicting the oxidation-reduction-state ratio for aqueous sulfur species (R′)
- isotopic compositions of sulfur compounds ( \(\delta S_1 ^{34} \) ).
15.
Prof. T. K. Poiker Dr. 《GeoJournal》1982,6(3):241-249
Computer Cartography has gone through many changes during its short life. This article tries to document some of the results of the development. The major conclusions are: - whereas the application of computer mappins is fluurishing, conceptual development is slow; - as a result the applications are simpler than they could be, given the development of computer science, and brute force reigns over elegance. To exemplify these points, the main types of Geographic Information Systems are discussed with respect to their recent achievements: Catastral mapping, Thematic mapping, Topographic mapping, Resource Information Systems, and Digital Terrain Models. 相似文献
16.
A petrogenetic model is developed to explain the evolution and geochemical character of granitic rocks in early Archean (pre 3.6 Gyr) continental crust taking into account the following important geological constraints, viz.:
- High geothermal gradients (probably in excess of 90 ° C/km) and resulting widespread granulite facies metamorphism even at relatively shallow depths
- The fractionation of certain major and trace elements under granulite facies conditions
- The composition and geochemical behaviour of fluids which emanate from or pass through terrains undergoing granulite facies metamorphism viz. carbonic fluids containing significant amounts of SO2 and halogens.
17.
R. Catalano B. d'Argenio C. B. Gregor A. E. M. Nairn G. Nardi P. Renda 《International Journal of Earth Sciences》1984,73(2):577-598
The Mesozoic lavas and minor intrusions in the thrust sheets of western Sicily have the following characteristics:
- The lavas in the Triassic Mufara Formation in the north were broken into fragments which rotated independently within the incompetent strata that enclose them. This behavior is characteristic of igneous rocks found within the more internal (northerly) thrust units.
- The Jurassic lavas in the more external (southerly) units have consistent directions which agree with those of the Ammonitico Rosso limestones in the same zone and lie about 30° clockwise from those of coeval autochthonous formations in Tunisia.Schult's presumed Cretaceous directions from Custonaci on the north coast (similar to those found in the Cretaceous Scaglia Rossa at Terrasini to the east byChannel et al., 1980) are rotated still more (140°) with respect to those of the autochthonous Iblean platform of SE Sicily. These differences are believed to reflect rotation of the thrust sheets during tectonic transport in Cenozoic times, the internal units being the most strongly rotated.
- All the igneous rocks are highly altered: generally the original mineralogy cannot be completely determined. Relative abundances of some of the less mobile elements (Ti, Sr, Y) suggest that they are intraplate basalts.
18.
Diopside twins mechanically on two planes, (100) and (001), and the associated macroscopic twinning strains are identical (Raleigh and Talbot, 1967). An analysis based on crystal structural arguments predicts that both twin mechanisms involve shearing of the (100) octahedral layers (containing Ca2+, Mg2+ and Fe2+ ions) by a magnitude of c/2. Small adjustments or shuffles occur in the adjacent layers containing the [SiO4]4? tetrahedral chains. While the (100) twins are conventional with shear parallel to the composition plane, this analysis predicts that (001) twins form by a mechanism closely related to kinking. A polycrystalline diopside specimen was compressed 8% at a temperature of 400° C, a pressure of 16 kilobars, and a compressive strain rate of about 10?4/s. Transmission electron microscopy on this specimen has revealed four basic lamellar features:
- (100) mechanical twin lamellae;
- (100) glide bands containing unit dislocations;
- (001) twin lamellae;
- (101) lamellar features, not as yet identified.
19.
Wilhelm Heinrich Paul Metz Werner Bayh 《Contributions to Mineralogy and Petrology》1986,93(2):215-221
Stoichiometric mixtures of tremolite and dolomite were heated to 50° C above equilibrium temperatures to form forsterite and calcite. The pressure of the CO2-H2O fluid was 5 Kb and \(X_{{\text{CO}}_{\text{2}} }\) varied from 0.1 to 0.6. The extent of the conversion was determined by the amount of CO2 produced. The resulting mixtures of unreacted tremolite and dolomite and of newly-formed forsterite and calcite were examined with a scanning electron microscope. All tremolite and dolomite grains showed obvious signs of dissolution. At fluid compositions with \(X_{{\text{CO}}_{\text{2}} }\) less than about 0.4, the forsterite and calcite crystals are randomly distributed throughout the charges, indicating that surfaces of the reactants are not a controlling factor with respect to the sites of nucleation of the products. A change is observed when \(X_{{\text{CO}}_{\text{2}} }\) is greater than about 0.4; the forsterite and calcite crystals now nucleate and grow at the surface of the dolomite grains, thus indicating a change in mechanism at medium CO2 concentrations. As the reaction progresses, the dolomite grains become more and more surrounded by forsterite and calcite, finally forming armoured relics of dolomite. Under experimental conditions this characteristic texture can only be formed if the CO2-concentration is greater than about 40 mole %. These findings make it possible to estimate the CO2-concentration from the texture of the dolomite+tremolite+forsterite+calcite assemblage. The results suggest a dissolution-precipitation mechanism for the reaction investigated. In a simplified form it consists of the following 4 steps:
- Dissolution of the reactants tremolite and dolomite.
- Diffusion of the dissolved constituents in the fluid.
- Heterogeneous nucleation of the product minerals.
- Growth of forsterite and calcite from the fluid.
20.
K. Viswanathan 《Contributions to Mineralogy and Petrology》1972,37(4):277-290
A series of K-plagioclases have been produced metastably by ion-exchanging the plagioclases in KCl-melt. Chemical analyses and re-exchange experiments (with NaCl-melt) have proved that the K-plagioclases are truly isomorphous with plagioclases. Because of their isomorphous nature it was possible to mix them in different proportions and homogenise them, thereby producing ternary feldspars of different compositions in the system Or-Ab-An. A comparative study of the lattice constants of plagioclases, their K-equivalents and the different ternary feldspars calculated using powder data leads to the following conclusions:
- It is possible to dertermine by X-ray methods the anorthite content of a plagioclase to an accuracy of ±1% An.
- The influence of the ionic size of the bigger cations Na, Ca, and K and that of order/disorder are different on different lattice constants and it is possible to distinguish these two effects.
- The b-parameter indicates a definite structural change in plagioclases at about 25–30% An.
- It is possible to predict the average Al/Si-distributions in the four different positions T1(o), T1(m), T2(o) and T(m) of all plagioclases of all stable structural states, using the c-parameter of their K-equivalents.