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1.
Werner Smykatz-Kloss 《Contributions to Mineralogy and Petrology》1972,36(1):1-18
The optical and x-ray investigation of 51 microcrystalline quartz samples show that they are built up of fibrous chalcedony (agates) or finest crystalline, isometric grained quartz (flints, cherts, jasper or Chrysoprase). These samples were examined by standardized d.t.a. — methods in order to get their inversion characteristics.
- A third of the samples conteins low-temperature cristobalite in addition to quartz (in two samples even as main component); the high-low inversion of this mineral lies between 80 and 245° C according to its defect character. In five samples of jasper low- tridymite is occurring as minor component.
- In contrary to macrocrystalline quartz crystals microcrystalline quartzes generally show no sharp inversion point. The inversion takes place over an interval of nearly 50° C, to be seen in the d.t.a. curve as a broad, only slightly endothermic effect with hardly visible peak or several small minima. In the curves of 15 samples no inversion could be detected. This broad inversion peak is caused by different defect characters of the crystals or even of parts of the crystals which invert at different temperatures (Flörke, 1955).
- There is no dependance of t i on the size of crystallites at least for crystals with diameter greater than 0.05 μ. The temperature of the most prominent inversion minimum allows a division of the microcrystalline quartz crystals analogous the macrocrystalline classification into samples with t i below and above 570° C. The lowest (518±2° C) and the highest t i (578,7+0,3° C) were measured at different parts of the same sample of a Chrysoprase.
- The intensity of the brown and red coloured parts of agate and jasper grows with increasing Fe2O3-content, but there is no connection between t i and chemical composition.
- As in macrocrystalline quartzes of caverns and veins there are also some t i -differences between the marginal and the central parts of agates or jaspers. The explanation lies in the mechanism of formation: higher t i in the margin (e.g. in one globular jasper) points to a formation by silification, whereas higher t i in the center indicates a formation by the filling up of cavities and veins.
- The variation in t i of microcrystalline quartzes and the comparison of these t i ? with those of associated low-temperature cristobalite shows a connection between temperatures of formation and inversion: samples with low t i (i.e. with a great number of defects) should be formed at low temperatures, that is by sedimentary or diagenetic processes, and samples with t i above 570° C (i.e. nearly without defects in the structure) should have crystallized out of hydrothermal solutions. The weak inversion peaks below 570° which in d.t.a. curves often appear besides a main peak at 570° C represent the small amount of diagenetically formed microcrystalline quartz with a large degree of defect character.
2.
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.
3.
Dr. Achim Hirschberg Helmut G. F. Winkler 《Contributions to Mineralogy and Petrology》1968,18(1):17-42
The stability relations between cordierite and almandite in rocks, having a composition of CaO poor argillaceous rocks, were experimentally investigated. The starting material consisted of a mixture of chlorite, muscovite, and quartz. Systems with widely varying Fe2+/Fe2++Mg ratios were investigated by using two different chlorites, thuringite or ripidolite, in the starting mixture. Cordierite is formed according to the following reaction: $${\text{Chlorite + muscovite + quartz}} \rightleftharpoons {\text{cordierite + biotite + Al}}_{\text{2}} {\text{SiO}}_{\text{5}} + {\text{H}}_{\text{2}} {\text{O}}$$ . At low pressures this reaction characterizes the facies boundary between the albite-epidotehornfels facies and the hornblende-hornfels facies, at medium pressures the beginning of the cordierite-amphibolite facies. Experiments were carried out reversibly and gave the following equilibrium data: 505±10°C at 500 bars H2O pressure, 513±10°C at 1000 bars H2O pressure, 527±10°C at 2000 bars H2O pressure, and 557±10°C at 4000 bars H2O pressure. These equilibrium data are valid for the Fe-rich starting material, using thuringite as the chlorite, as well as for the Mg-rich starting mixture with ripidolite. At 6000 bars the equilibrium temperature for the Mg-rich mixture is 587±10°C. In the Fe-rich mixture almandite was formed instead of cordierite at 6000 bars. The following reaction was observed: $${\text{Thuringite + muscovite + quartz}} \rightleftharpoons {\text{almandite + biotite + Al}}_{\text{2}} {\text{SiO}}_{\text{5}} {\text{ + H}}_{\text{2}} {\text{O}}$$ . Experiments with the Fe-rich mixture, containing Fe2+/Fe2++Mg in the ratio 8∶10, yielded three stability fields in a P,T-diagram (Fig.1):
- Above 600°C/5.25 kb and 700°C/6.5 kb almandite+biotite+Al2SiO5 coexist stably, cordierite being unstable.
- The field, in which almandite, biotite and Al2SiO5 are stable together with cordierite, is restricted by two curves, passing through the following points:
- 625°C/5.5 kb and 700°C/6.5 kb,
- 625°C/5.5 kb and 700°C/4.0 kb.
- At conditions below curves 1 and 2b, cordierite, biotite, and Al2SiO5 are formed, but no garnet.
4.
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.
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.
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.
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.
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.
9.
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
10.
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.
11.
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 ( \(\delta S_1 ^{34} \) ).
12.
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
13.
Dr. Christoph Hoffmann 《International Journal of Earth Sciences》1976,65(1):939-966
In the central area of the early paleozoic Damara belt migmatites and some types of granites (sensu lato) crop out. Conventional petrographic data were collected and melting experiments were carried out with 63 samples of such rocks. Based on these data, migmatite genesis can be classified as follows:
- Formation by partial melting and separation of more liquid and more crystalline fractions, the melting behaviour of these fractions has to be principally similar then.
- Formation by injection of “geologically liquid” crystal-melt mixes into rocks of (incidentally) similar or (more frequently) dissimilar melting behaviour.
- Formation by partial melting of metasediments of originally different composition. The method is applied and demonstrated for outcrops with complicated interrelations and it is shown that temperature estimates are possible thereby (670° to 710° at 4–5 kb H2O pressure in the central Damara belt).
14.
The Elzevir batholith belongs to a suite of trondhjemitic intrusions emplaced at ca. 1,240 Ma in the Grenville Province of eastern Ontario. New major and trace element data, including REE, combined with isotopic and petrographic data indicate that:
- the batholith has calc-alkalic affinities;
- the Elzevir parental magma is very similar to that of dacites in the nearby, coeval metavolcanic rocks; the magma formed by partial melting of crustal material at granulite grade;
- chemical differences between the plutonic and volcanic rocks can be best explained by accumulation of plagioclase in the plutonic environment;
- fractionation was dominated by plagioclase and quartz, with lesser biotite and epidote, and minor zircon and apatite.
15.
Dr. Christoph Hoffmann 《Contributions to Mineralogy and Petrology》1970,27(4):283-320
In the southern Apennin (= northern part of the region dealt with) and the Coasta Chain (= southern part) there are metabasalts wich are classified in the northern part as:
- Glaucophane rocks of the albite-lawsonite-glaucophane-subfacies with the assemblage glaucophane + pumpellyite + lawsonite ±albite ±aragonite ±muscovite (7 rock analyses, 8 mineral analyses). These rocks are conceived as relics of an older burial metamorphism.
- Rocks with pumpellyite and chlorite or also chlorite alone, that are interpreted as reaction rims between the metastable glaucophane rocks and the country rock (phyllites, quartzites). The assemblages pumpellyite + chlorite and chlorite alone are to be found (2 rock analyses and 2 mineral analyses).
- Rocks with lawsonite and/or epidote belong to the same mineral facies as the country rock: a facies similar to the greenschist facies (called “lawsonite-albite-chlorite-subfacies”) which is characterized by the assemblages lawsonite + albite + chlorite ±calcite and also epidote ±lawsonite + albite + chlorite ± muscovite. These types are attributed to a younger dynamo-metamorphism (2 rock analyses).
16.
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.
17.
Chemical and mineralogical compositions of granitic rocks of the French Massif Central enable us to classify them into two distinct groups: (i) leucogranites, (ii) granodiorites or quartz-monzonites, separated by a natural gap. The differences between these two groups are not only chemical and mineralogical, but are also reflected by: conditions of crystallization as deduced from compositions and from thermal metamorphism of xenoliths. nature of inclusions and, especially, the occurrence of basic fine-grained igneous xenoliths restricted to the granodiorite — quartz-monzonite group relations between intrusive and autochtonous migmatitic masses; levels of formation and of intrusion; the granodioritic and quartz-monzonitic magmas have originated at deeper horizons of the earth's crust than the leucogranitic one, but have risen higher. In our opinion these differences are linked, and the specific characteristics of the granodiorites and quartz-monzonites are related to the presence of basic igneous inclusions. These inclusions are relics of deep basic intrusions in the earth's crust, which have overheated the surrounding acid rocks beyond the minimum temperature of melting. Thus granodioritic or quartz-monzonitic melts were produced and were able to rise to superficial levels. These inclusions are missing in leucogranites. The compositions of the latter and their poor mobility suggest a wet anatectic origin in minimal PT conditions. 相似文献
18.
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.
19.
Massive sulfide deposits located on Hercynian islets of northwestern Morocco exhibit four main characteristics: They are strata-bound massive pyrrhotite deposits mined for sulfur and/or base metals occasionally occurring as sulfides of workable grade. Volcanic rocks with which these massive sulfide orebodies are associated are scarce, although always present as acid flows of submarine emissions of either rhyolitic or more often quartz-keratophyric nature. Later on, basic plutonics intruded the pelitic country rocks. Stockworks underlying the massive sulfide orebodies are common, but not systematic. When present, they occur in siltite ± phyllite ± carbonate rocks at the wall of massive sulfide lenses. They consist of fissural disseminations transformed by epimetamorphic recrystallization and by one schistosity generally concordant with s0. Associated alterites and exhalites belong to three types, i.e., sericitite (or biotite-rich rock), chloritite, and/or chert (jasper). Generally well located in a back-arc basin environment characterized by a two-phase geological history, i.e., “extension and volcanism, compression and metamorphism”, these volcano-sedimentary deposits exhibit distal features with regard to the volcanism coeval with their sedimentation. They are mostly linked with strongly reducing environmental properties entailing pyrrhotite and/or magnetite syngenetic deposition, whatever the iron activity. 相似文献
20.
Dr. Martin Hartmann 《International Journal of Earth Sciences》1973,62(3):742-754
Suspended matter was separated from the hydrothermal brines of the Atlantis-II Deep in the Red Sea. Contents of iron, manganese, copper, and zink collected on membrane filters were measured by X-ray-flourescence, and the main results were:
- Metal concentrations in suspended form were lower by 10?1 to 10?5 compared to the dissolved concentrations of the brines.
- Suspended copper and zink were enriched most pronounced in the deeper brine zone — markedly so in the SW-basin, values there ranged between 10 and 30μg/l, one Zn-value was as high as 60μ/l, the other basins contained mostly less than 1 to 10μg/l.
- Iron, copper, and zink in the deeper brine zone and in few cases also in the 50°-brine were suspended in the form of sulfide compounds. This conclusion is based only on the slightly purple-, green-, and blue-colored gray hues of the material on the filters and its rapid oxidation upon contact with the air.
- In the transition zone of the 50°/60°-brine iron hydroxides were highly concentrated with values ranging up to 1000μg Fe/l.
- Suspended manganese is found only within the transition zone of brine to the normal sea water, where up to 200μg Mn/l in form of darkbrown manganese hydroxides were found.
- Concurrently with the increased thermal activity since 1966 more strongly reducing conditions within the brines seemed apparent which were caused by discharge of higher amounts of Sulfides into the basins. Increased precipitation of heavy metal sulfides was found to be most pronounced in the SW-basin.