Results 201 to 210 of about 6,679 (273)
Magnesium metasomatism during hydrothermal alteration of new oceanic crust
Geology, 1978 A semiquantitative calculation of the amount of Mg fixation during greenschist-facies metamorphism of a 1-km-thick section of the oceanic crust beneath mid-ocean ridge crests shows that it is of the same order of magnitude as the “excess” (unbalanced) input of this element to the ocean.
Salman Bloch, Albrecht W. Hofmann
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Contributions to Mineralogy and Petrology, 1994 Dolerite dykes that cut Tertiary baslats near the Skaergaard intrusion, East Greenland, are extensively altered to metasomatic assemblages indicating large scale mobilisation of calcium and alkalis. The alteration is characterised by replacement of the dolerite by prehnite together with lesser amounts of epidote, amphibole, salite, titanite, calcite ...
Rose, N.M., Bird, D.K.
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Geology, 1989 On Santa Catalina Island, southern California, bluechist to amphibolite facies metasedimentary, metamafic, and meta-ultramafic rocks show veining and alteration that reflect fluid flow and mass transfer at 25-45 km depths in an Early Cretaceous subduction zone. Synkinematic and postkinematic veins record fluid transport and metasomatism during prograde
Mark D. Barton, Gray E. Bebout
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Journal of African Earth Sciences, 1997 Abstract The granite at Arba'at shows many of the chemical features of a metallogenetically specialised A-type granite, although no economic mineralisation has yet been found there. The specialised character is, however, only strong within the aphyric granites of low density forming the interior of the intrusion.
A.A. Osman +2 more
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Metasomatism in Iceland: Hydrothermal Alteration and Remelting of Oceanic Crust
, 1987 The geochemistry of Icelandic volcanics, especially as pertains LIL-elements, RE-elements, and isotopes, has in the literature called for explanations involving heterogeneous mantle source. These explanations are shown to be incompatible with the data at hand.
Stefán Arnórsson +3 more
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, 1987 Two types of hydrothermal alteration can be recognized in a biotite granite of Variscan age in Northern Switzerland. The first is related to the intrusion of the granite and lead to the replacement of K-spar and biotite by muscovite, of plagioclase by sericite and calcite and to a chloritization of biotite. This process affected the granite as a whole.
T. J. Peters
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Economic Geology, 1999 The Ventersdorp contact reef is an auriferous conglomerate horizon and economic orebody on top of the Late Archean Witwatersrand Supergroup in South Africa. It differs from the other conglomerate beds (reefs) in the Witwatersrand basin in having a massive metabasalt sequence as its hanging wall and by its intense post-depositional alteration.
H. E. Frimmel, V. H. Gartz
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Geological Magazine, 1929 In Teesdale and Weardale, at all exposures that have been examined, the Whin Sill is cut by a system of approximately vertical, sweeping, joint planes. These are distinct in general character from, and are on a larger scale than, the columnar jointing which is conspicuous in all vertical scars of Whin Sill. The pattern of the larger scale jointing on a
L. R. Wager
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The Canadian Mineralogist, 2012 Secondary mineral assemblages in komatiites of the south-western Abitibi greenstone belt reflect the tectonic evolution of the region. Changes in mineralogy were accompanied by changes in fluid chemistry over time. Hot, plume-generated komatiites (2719–2704 Ma) were hydrated by hot fluids (200–300 oC), replacing the primary olivine and pyroxenes by ...
Michael P. Gorton, Eva S. Schandl
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Mineralogy and Petrology, 1987 Homogenization temperatures and salinity data are documented for fluid inclusions present in quartz from a Palaeozoic alkaline to peralkaline granite intrusion. A wide range of salinities (3.8 to 60.6 wt% NaCl equivalent) and homogenization temperatures (25.8 to 537 °C) indicates a sequential entrapment of different fluids, whereby the detected ...
Bernd G. Lottermoser
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