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1.
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 ( \(\delta S_1 ^{34} \) ).
2.
Shuguang Li 《中国地球化学学报》1983,2(3):213-222
Based upon geological and geochemical data on the genesis of Gongchangling rich magnetite deposit, it is suggested that the deposit is of multi-genesis, and a three-stage geochemical model for the genesis of the deposit is proposed:
- Sedimentary stage: the deposition of BIF (magnetite-quartzite) was accompanied by high-grade magnetite (hematite)-siderite ores which are intercalated with magnetite-quartzites as lenses or stratoid shoots.
- Metamorphic stage: in response to metamorphism, siderite, was decomposed into magnetite and graphite with decreasing fO 2 and increasingP CO 2. In the marginal parts of magnetite-siderite ores or within the thin-layered interbeds where fO 2 was high relative toP CO 2 were formed graphite-free rich magnetite ores.
- Hydrothermal stage: as a result of later hydrothermal process diffusive metasomatism between the rich ores and the host rocks and silica leaching took place, thus giving rise to the rich magnetite ore of metasomatic type and altered rocks.
3.
W. E. G. Taylor 《International Journal of Earth Sciences》1968,58(2):564-587
The paper presents novel information on the Caledonian orogeny in Ireland. A series of Dalradian (Upper Precambrian-Lower Cambrian) metasedimentary rocks occur as an envelope to a granitic igneous complex at Slieve Gamph, Western Ireland. These metasedimentary rocks have been deformed at several distinct times and evidence is shown for the following sequence of events:
- formation of major nappe structures and a tectonic slide. The axial-plane traces of the folds probably trended N. E.-S. W.
- formation of upright, gently plunging folds with axial-plane traces of the folds trending N. E.-S. W. Emplacement of the components of the Slieve Gamph igneous complex.
- formation of a conjugate set of folds:
- Open folds with N. N. E.-S. S. W. trending axial-planes which dip to the east,
- Open folds with E.W. trending axial-planes which dip to the north.
- formation of kink-bands, open and conjugate folds with an axialplane trace trending N. W.-S. E.
4.
Basalts from DSDP Site 417 (109 Ma) exhibit the effects of several stages of alteration reflecting the evolution of seawater-derived solution compositions and control by the structure and permeability of the crust. Characteristic secondary mineral assemblages occur in often superimposed alteration zones within individual basalt fragments. By combining bulk rock and single phase chemical analyses with detailed mineralogic and petrographic studies, chemical changes have been determined for most of the alteration stages identified in the basalts.
- Minor amounts of saponite, chlorite, and pyrite formed locally in coarse grained portions of massive units, possibly at high temperatures during initial cooling of the basalts. No chemical changes could be determined for this stage.
- Possible mixing of cooled hydrothermal fluids with seawater resulted in the formation of celadonite-nontronite and Fe-hydroxide-rich black halos around cracks and pillow rims. Gains of K, Rb, H2O, increase of Fe3+/FeT, and possibly some losses of Ca and Mg occurred during this stage.
- Extensive circulation of oxygenated seawater resulted in the formation of various smectites, K-feldspar, and Fe-hydroxides in brown and light grey alteration zones around formerly exposed surfaces. K, Rb, H2O, and occasionally P were added to the rocks, Fe3+/FeT increased, and Ca, Mg, Si and occasionally Al and Na were lost.
- Anoxic alteration occurred during reaction of basalt with seawater at low water-rock ratios, or with seawater that had previously reacted with basalt. Saponite-rich dark grey alteration zones formed which exhibit very little chemical change: generally only slight increases in Fe3+/FeT and H2O occurred.
- Zeolites and calcite formed from seawater-derived fluids modified by previous reactions with basalt. Chemical changes involved increases of Ca, Na, H2O, and CO2 in the rocks.
- A late stage of anoxic conditions resulted in the formation of minor amounts of Mn-calcites and secondary sulfides in previously oxidized rocks. No chemical changes were determined for this stage.
5.
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.
6.
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
7.
The occurrence of talc and tremolite in a temperature gradient was investigated in siliceous calcite-dolomite sediments exposed along a strip in the southeastern part of the Damara Orogen. Five bivariant reactions may lead to the formation of talc and tremolite:
- 3 dolomite+4 quartz+1 H2O ? 1 talc+3 calcite+3 CO2
- 5 talc+6 calcite+4 quartz ? 1 tremolite+6 CO2+2 H2O
- 2 talc+3 calcite ? 1 tremolite+1 dolomite+1 CO2+1 H2O
- 5 dolomite+8 quartz+1 H2O ? 1 tremolite+3 calcite+7 CO2
- 2 dolomite+1 talc+4 quartz ? 1 tremolite+4 CO2.
8.
Dr. Wolfgang E. Krumbein 《International Journal of Earth Sciences》1971,60(2):438-471
The influence of bacteria on recent sediments was first discussed in 1885, whenFischer andGazert were discussing the cycle of substances in the sea as well as in sediments. The influence of bacteria on the cycling of C, N, S, P in recent sediments and the open sea was soon accepted by marine geologists. Nevertheless, only very few experiments have, so far, shown more than qualitative and quantitative data collection in various restricted areas. This is due to the extensive and complicated chain of reactions on the surface of sediments and in the sediment itself. Biologists are asking for the amount of organic and inorganic matter which is reworked and released to the sea. Geologists usually emphasize the amount of substances which are sedimentated. For biologists the sediment is only part of their dominant ecosystem (the sea). While, for geologists the “sea” is only furnishing and influencing their first range system sediment. How much then, are bacteria involved in the slow process of conversion from a recent sediment to sedimentary rocks? Bacteria influence more or less strongly and to a more or less advanced degree of diagenesis:
- The organic matter in sediments and the final form in which it is found.
- The anions CO3 2?, NO3 ?, OH-, SO4 2?, PO4 3? as well as their intermediate stages and the resulting minerals.
- The cations H+, NH4 +, Ca2+, Fe2+, Fe3+, and a series of metals which are dissolved or precipitated by microbial activities as for example Fe, Mn, Cu, Ag, V, Co, Mo, Ni, U, Se, Zn.
- The equilibrium of silicium. At least diatoms and radiolarians are precipitating silica, while other reactions which have been proved are not yet shown to influence marine sediments.
- pH-values and oxidation-reduction potentials of the sediment.
- The composition of interstitial waters.
- The surface activity of minerals, since bacteria are growing especially on particle surfaces.
- The energy content and temperature of sediments.
- The texture of fine grained sediments.
- The fossilization of microfauna, macrofauna and trace fossils.
9.
Concordant granite sheets from the granulite facies Scourian Complex, N.W. Scotland exhibit the following features:
- a common planar fabric with their host pyroxene granulites;
- the presence of an exsolved ternary feldspar phase;
- a low-pressure, water-saturated minimum composition;
- K/Rb ratios (450–1,350) distinctly higher than most upper crustal granites but similar to the surrounding granulites;
- low absolute concentrations of the rare earth elements (REEs), light REE enrichment, and large positive Eu anomalies.
10.
Dr. Hasso Schorin 《International Journal of Earth Sciences》1980,69(1):226-244
In the present phase of the volcanic activity on Nea Kameni / Santorini / Greece the calc-alkalic volcanic rocks are decomposed by H2O, CO2 and SO2 gases of about 100 °C. Using a method ofGresens (1967) for the determination of gains and losses of compounds five different processes could be distinguished:
- leaching of compounds
- enrichment of Ca as gypsum
- increase of Fe2O3 (6%–11%), TiO2 (0,8%–3%) and Zr
- enrichment of Al2O3 (15%–29%), TiO2 (0,8%–1,5%) and K
- increase of Al2O3 (15%–26%), Fe2O3 (6%–9%), TiO2 (0,8%–1,3%), Sr, Ba, Pb and Zr
11.
The equilibrium conditions of the following reaction 2 zoisite +1 CO2?3 anorthite+1 calcite+1 H2O 2 Ca2Al3[O/OH/SiO4/Si2O7]+1 CO2?3 CaAl2Si2O8+1 CaCO3+1 H2O have been determined experimentally at total pressures of P j= 2000 bars, P f =5000 bars, and P f =7000 bars. Owing to the vertical position of the equilibrium curves in isobaric T- \(X_{{\text{CO}}_{\text{2}} }\) diagrams, the composition of the binary H2O-CO2 fluid phase coexisting with zoisite is independent of temperature in the temperature interval investigated. According to our experiments, orthorhombic zoisite is only stable in equilibrium with a fluid phase at a concentration of CO2 which is less than, respectively, ca. 2 Mol% CO2 at P f =2000 bars, ea. 6 Mol% at P f =5000 bars, and ca. 10 Mol% at P f =7000 bars. Thus, the fluid phase coexisting with zoisite is rich in H2O. While this is independent of temperature the experimental data demonstrate that the influence of pressure cannot be neglected: With increasing pressure the concentration of CO2 of the fluid phase coexisting with zoisite can rise a little. The position of the reaction studied, which is independent of temperature and exhibits small values of \(X_{{\text{CO}}_{\text{2}} }\) ,leads to two important petrogenetic conclusions:
- The occurrence of zoisite is an indicator for a CO2-poor and H2O-rich fluid composition during metamorphism of marly calcsilicates.
- If the concentration of CO2 of the fluid phase coexisting with zoisite exceeds the equilibrium value of \(X_{{\text{CO}}_{\text{2}} }\) calcite+anorthite+H2O is formed from zoisite+CO2. Thus, a considerable increase in the anorthite-content of plagioelase is possible.
12.
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.
13.
E. Salje 《Physics and Chemistry of Minerals》1987,14(2):181-188
Landau theory of the \(P\bar 1 - I\bar 1\) phase transition in Ca-rich plagioclases reveals the sensitivity of the phase transition behaviour to a) Al, Si disorder, b) structural replacement of Ca by Na, and c) inhomogeneities of lattice strains. The following effects are predicted:
- A tricritical phase transition exists in fully ordered anorthite. Al, Si disorder and Na, Ca exchange lead to second order phase transitions.
- The transition temperatures depend sensitively on the degree of Al, Si disorder and the chemical composition of the Ca-rich plagioclases. Increasing Na-content decreases the transition temperatures.
- The thermal evolution of c and d reflections depends on the homogeneity of the crystal and do not necessarily reflect the temperature evolution of the macroscopic lattice strain. A simple quadratic dependence of the X-ray scattering intensity on the order parameter exists only for fully ordered, homogeneous anorthite.
14.
Dr. Barbara Theilen-Willige 《International Journal of Earth Sciences》1982,71(1):318-327
The following facts have supported the origin of the Araguainha circular structure in Central Brazil by a meteoritic impact:
- the almost circular contour
- the impact-morphologic sequence including a central uplift, ring walls and a basin rim of escarpments
- outcrops of suevites and mixed breccias
- the evidence of shock metamorphism
- the presence of shatter cones, and
- negative anomalies of the total intensity of the magnetic field at the center of the ring structure.
15.
Alexander A. Godovikov George C. Kennedy 《Contributions to Mineralogy and Petrology》1968,19(2):169-176
Prior experimental work has shown that in the laboratory the mineralogy of eclogites is sensitive to the ratio of CaO ∶ MgO ∶ FeO and that the reaction pyroxene + kyanite?garnet + quartz proceeds to the right at high pressures in rocks rich in magnesium and to the left in rocks rich in calcium and iron. Typical basalts crystallized at high pressure never contain kyanite. The chemistry and mineralogy of a large number of naturally occurring eclogites show they belong to three classes.
- Kyanite-free magmatic eclogites, rich in magnesium, from:
- kimberlites
- dunites and serpentinites.
- Kyanite-bearing eclogites and grosspydites rich in CaO and low in FeO with intermediate MgO from:
- kimberlites
- gneisses.
- Kyanite-free eclogites of metamorphic origin rich in iron with low magnesium and intermediate amounts of calcium from:
- glaucophane schists
- gneisses.
16.
The origin of scapolite in the regionally metamorphosed rocks of Mary Kathleen,Queensland, Australia
Scapolite at Mary Kathleen (North-Western Queensland) occurs in calcareous and non-calcareous metapelites, acid and basic metavolcanics and metadolerites. Graphical treatment of the relationship between scapolite composition (Me%) and the host rock oxide ratios CaO/Na2O and Al2O3/(CaO + Na2O) reveals the following points:
- The calcareous metapelites are also very sodic.
- Scapolite in calcareous metapelites is more marialitic than that in low-calcium equivalents.
- In graphs of Me% against CaO/Na2O and Al2O3/(CaO + Na2O) the metasediments and the metaigneous rocks show markedly different trends.
17.
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.
18.
Huang Jizhong 《中国地球化学学报》1991,10(1):45-57
This paper is the continuation of the paper published in 1985, with the emphasis on the irregular components of natural gases from the Sichuan Basin—the isotopic compositions of C,H and S, the n-and iso-alkane predominance (C6-C13) of methane homologues, the compositional characteristics of benzene and methylbenzene, and the distribution and geochemical characteristics of organic sulfur-bearing compounds including thiophen, thio-alcohol, etc. It is considered that natural gases from the Sichuan Basin have different distributional characteristics in different layers and locations, suggesting that they are controlled by a combination of factors such as kerogen type, maturity of organic matter and wall-rock assemblage.
- The type of source material (or precursor) is a main factor affecting the geochemical characteristics of natural gases. T3x-h and P2l produce coal-series gases with type-III source material dominant. The C and H isotopic compositions of natural gases are heavier, the contents of C6H6 and C7H8 are high, C7H8/C6H6 < 1. the content of C4H4S is low, and the predominance in isoalkane (C6C13) is obvious. J1t. P1y. Z2b. etc. produce oil-series gases with type-I and -II kerogens dominant, indicating that the geochemical characteristics of natural gases are different from those described above.
- The maturity of organic matter is an important factor affecting the composition of natural gases.With increasing maturity of organic matter, the C and H isotopic compositions tend to become light. C1 and C2 isotopic values are nearly equal or even inverse, and C4H4S decreases in content.
- Wall-rock assemblage has apparent influence on the S isotopic composition. The Middle-Lower Triassic series belongs to sulfate-carbonate formations enriched in gypsum. Therefore, the (δ34S values of natural gases are relatively high (< 20 %.) against the lower values for other layers due to the absence of gypsum layers.
19.
B. Lammerer I. Fruth D. D. Klemm E. Prosser K. Weber-Diefenbach 《International Journal of Earth Sciences》1976,65(1):436-459
Geologic, petrological and geochemical investigations have been carried out in the western part of the “Zillertaler Alpen”. Important results are:
- The premetamorphic material of the Greiner series consists of conglomerates, breccias, arcosic-sandstones or greywackes, bituminous shales, volcanic lavas and tuffs.
- The southern part of the “Zentralgneis” shows a differentiation trend from alkaline granite to quarzdiorite with predomination of granodiorite.
- Chemical relationships of granodiorite to its restitic inclusions allow the supposition of a palingenetic origin of the granitic rocks.
- At least two stages of metamorphism can be differentiated.
- Parts of the Greiner series, covered by triassic metasediments, are supposed to be of Permian age. A lower age boundary can not yet be given.
- Some vertical, northeast striking faults with throws of more than 1 or 2 kilometers produced southward verging drag folds.
- Geodynamic aspects, revealed from regional metamorphism and tectonics, are discussed.
20.
Dr. Hervé Chamley 《International Journal of Earth Sciences》1986,75(1):271-285
Various stratigraphic and paleoenvironmental results arise from mineralogical, geochemical and micromorpho logical investigations on Late Cretaceous and Cenozoic sediments recovered by the Deep Sea Drilling Project in the West Pacific: Stratigraphic correlations. The deep pelagic red clays deposited on either side of the Shatsky Rise contain a variety of clay minerals, which point to the importance of eolian detrital supply and allow rough stratigraphic correlations. Climate and paleocirculation. Neogene sediments of the Lord Howe Rise area reflect closely the relationship between the evolution of the Antarctic ice sheet and related aridification stages, and the atmospheric and oceanic circulation pattern since 14 my. Regional and global tectonics. The post-Eocene deposits around New Zealand express a sequence of tectonic events and of relaxation stages, associated with changes in the circulation regime. Along the inner wall of the Japan Trench, clay mineral successions document the existence of an outer continental landmass until the late Oligocene, its collapse associated with volcanism close to the Paleogene-Neogene boundary, and an increased detrital influence from Japan since the early-middle Miocene. Volcanism, diagenesis and detrital supply. The Aptian to Maastrichtian sediments in the Mariana Basin document a complex sequence of geochemical and geodynamical events: proximal volcanism and local supply from subaerial archipelagoes; early marine diagenesis during lithospheric subsidence and plate migration; and finally the occurrence and evolution of terrigenous input from distant sources distributed by marine currents. 相似文献