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P. L. C. Grubb 《Mineralium Deposita》1971,6(4):265-274
Mineralogical variations both in vertical profile and bulk sized samples at Weipa are similar in broad outline, but show significant variations in detail. Surface planation has been limited and confined mainly to the limbs of a broad synclinal warp at Andoom and Pera Head. Whereas the proportional increase in boehmite within the upper levels of the pisolitic bauxite may in part be correlated with the degree of subsequent surface planation, other factors such as thickness of profile, size fraction distribution, and quartz sand content also play an essential role. The significance of underlying rock porosity is emphasised together with the special geomorphic conditions induced by warping here. It is concluded that leaching conditions were less dynamic than at Gove and that this accounts in large part for both the high boehmite content and lithological relationships of the Weipa bauxite.
Zusammenfassung Die Bauxite von Weipa sind sowohl im senkrechten Profil, wie auch in großen gesiebten Proben generell ähnlich, weisen aber im Detail wichtige Unterschiede auf. Die Oberflächen-Erosion hat sich hauptsächlich auf die breiten Muldenflügel der synklinalen Mulde in Andoom und Pera Head ausgewirkt. Während die Zunahme von Boehmit in den oberen Schichten des pisolitischen Bauxits teilweise mit dem der Oberflächen-Erosion verknüpft sein kann, können andere Faktoren, wid die Mächtigkeit des Profils, große Bruchverteilung und der Quarz-Sand-Gehalt ebenfalls eine wichtige Rolle spielen. Die Bedeutung der Fels-Porosität wird hervorgehoben, zusammen mit den speziellen geomorphologischen Bedingungen, die durch Einmuldung herbeigeführt werden. Es ergibt sich, daß die Auslaugevorgänge weniger dynamisch waren, als in Gove und zum großen Teil sowohl den hohen Boehmit-Gehalt, wie auch die lithologische Verwandtschaft der Weipa-Bauxite erklären.相似文献
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E. Sherbon Hills 《International Journal of Earth Sciences》1959,47(2):543-561
The structure and history of several Devonian cauldron-subsidences and related granitic intrusions showing evidence of sub-surface ring-fracturing in South Eastern Australia are discussed. The Marysville Igneous Complex includes fish and plant bearing beds in the Acheron Cauldron, which has a diameter of 15 miles, and contains 6000 ft. of acid lavas, with subordinate andesites and basalts. Most of the occurrences are consanguineous. The parent magma is intermediate, close to the hypersthene dacites of the region, and is believed to have been injected as a magma wedge from the east. 相似文献
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Tom Andersen 《Contributions to Mineralogy and Petrology》1986,93(4):491-503
Three different types of carbonatite magma may be recognized in the Cambrian Fen complex, S.E. Norway: (1) Peralkaline calcite carbonatite magma derived from ijolitic magma; (2) Alkaline magnesian calcite carbonatite magma which yielded biotite-amphibole søvite and dolomite carbonatite; and (3) ferrocarbonatite liquids, related to (2) and/or to alkaline lamprophyre magma (damjernite). Apatite formed during the pre-emplacement evolution of (2) contains inclusions of calcite and dolomite, devitrified mafic silicate glass and aqueous fluid. All of these inclusions have a magmatic origin, and were trapped during a mid-crustal fractionation event (P4 kbars, T625° C), where apatite and carbonates precipitated from a carbonatite magma which coexisted with a mafic silicate melt. The fluid inclusions contain water, dissolved ionic species (mainly NaCl, with minor polyvalent metal salts) and in some cases CO2. Two main groups of fluid inclusions are recognized: Type A: CO2-bearing inclusions, of approximate molar composition H2O
88–90
CO
27-5
NaCl
5
(d=0.85–0.87 g/ cm3). Type B: CO2-free aqueous inclusions with salinities from 1 to 24 wt% NaCleq and densities betwen 0.7 and 1.0 g/cm3. More strongly saline type B inclusions (salinity ca. 35wt%, d=1.0 to 1.1 g/cm3) contain solid halite at room temperature and occur in overgrowths on apatite. Type A inclusions probably contain the most primitive fluid, from which type B fluids have evolved during fractionation of the magmatic system. Type B inclusions define a continuous trend from low towards higher salinities and densities and formed as a result of cooling and partitioning of alkali chloride components in the carbonatite system into the fluid phase. Available petrological data on the carbonatites show that the fluid evolution in the Fen complex leads from a regime dominated by juvenile CO2 + H2O fluids during the magmatic stage, to groundwater-derived aqueous fluids during post-magmatic reequilibration. 相似文献