Results 171 to 180 of about 6,856 (206)
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Magnesium metasomatism during hydrothermal alteration of new oceanic crust
Geology, 1978A 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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Carbonic Metasomatism and Charnockitic Alteration
Journal Geological Society of India, 1994Abstract Field relations in an orthogneiss quarry within the Palghat Gap region illustrate the development of charnockite alteration halos surrounding alkaline pegmatite dykes. Altered orthopyroxenes in the charnockitic zones are artifacts from concordant melt pockets within the gneisses, where orthopyroxene has developed prior to the ...
M. Santosh, U. P. Radhika
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Metasomatic alteration of pelagic ooze on spreading ocean ridges
Marine Geology, 1982Abstract The lithologic unit 5 at DSDP Site 251 on the western flank of the southwest branch of the Indian Ocean Ridge, in which low-temperature metasomatic grandite hydrogarnet occurs, is shown to have been a nannofossil ooze when the hydrothermal solution was introduced. Extensive recrystallization of calcite occurred subsequent to the formation of
A.J. Easton +3 more
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Metasomatically altered peridotite xenoliths from the hessian depression (Northwest Germany)
Geochimica et Cosmochimica Acta, 1990Abstract A set of 36 spinel lherzolite and spinel harzburgite xenoliths from 7 occurrences of Tertiary alkali olivine basalt and olivine nephelinite have been investigated for modal composition, major elements, and 39 minor elements. The peridotites were depleted during former partial melting events.
Gerald Hartmann, K.Hans Wedepohl
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Chemical aspects of hydrothermal alteration with emphasis on hydrogen metasomatism
Economic Geology, 1964The ratio of cation to hydrogen-ion concentration is used as a basis for coordinating many observed varieties of silicate rock alteration. Low ratios drive alteration from feldspar through sericite, montmorillonite, or paragonite, toward kaolinite or pyrophyllite.
J. J. Hemley, W. R. Jones
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Combination processes of diamond recovery from metasomatically altered kimberlite rocks
Journal of Mining Science, 2017The article gives new experimental data on chemistry, phase composition, structure and physicochemical properties of surface of minerals composing metasomatically altered kimberlite rocks. The authors have determined formation conditions and basic genetic types of mineral micro- and nano-size phases on diamond surface in the form of aluminosilicate ...
V. A. Chanturia +5 more
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Geochemical features of metasomatically altered granitic rocks in Azov region
International Geology Review, 1967Mineralogical and chemical analyses, distribution-abundance of Li, Rb, Ta, Nb, Be, Sn, Zr and rare earths of granitoid massifs and migmatites, and other data show that the altered granitoids in the area are essentially transitions from lithionite-amazonite-biotite to biotite-albite apogranites representing early stages of the metasomatic process. --IGR
I.K. Pyatenko +2 more
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Mineralogical zonation and metasomatism of the alteration pipes of Cyprus sulfide deposits
Economic Geology, 1989The stockwork mineralized lavas associated with the cupriferous pyrite deposits of Cyprus occur in the cores of concentrically zoned alteration pipes. These represent the channels of ascending hydrothermal solutions. This paper reports a detailed mineralogical and geochemical study of the Pitharokhoma alteration pipe and reconnaissance studies of other
H. G. Richards, J. R. Cann, J. Jensenius
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Lagrangian and Eulerian Representations of Metasomatic Alteration of Minerals
1987Both Lagrangian and Eulerian formulations of fluid flow coupled to fluid/rock interaction provide complete descriptions of metasomatic processes based on a continuum representation of porous media. The Eulerian method is an inherently transient description of advective and diffusive/dispersive transport referred to a reference frame that is fixed with ...
Peter C. Lichtner +2 more
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Metasomatic Alteration of Ultramafic Rocks
1989Metasomatized ultramafic rocks from the 3800 Ma Isua supracrustal belt have been preferentially enriched in calcium, aluminium and silica, but show no or only little addition of potassium and rubidium. This unusual geochemical response to fluid infiltration can be explained in the light of a low buffered activity of aqueous silica during progressive ...
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