Results 171 to 180 of about 210,813 (245)
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
semanticscholar +4 more sources
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
semanticscholar +4 more sources
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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American Mineralogist, 2020 Scheelite from the Tongshankou porphyry- skarn Cu-Mo(-W) deposit occurs mainly as disseminated grains in the altered granodiorite porphyries at depth (Sch A), in the skarn coeval with retrograde alteration (Sch B) and in distal quartz veins crosscutting ...
Jinsheng Han +6 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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