Results 161 to 170 of about 1,786 (213)

Alkali content of alpine ultramafic rocks

Geochimica et Cosmochimica Acta, 1965
The lower limit of abundance of sodium and potassium in ultramafic rocks is less than the threshold amount detectable by conventional analytical methods. By a dilutionaddition modification of the flame-spectrophotometric method, sodium and potassium have been determined in 40 specimens of alpine ultramafic rocks.
Warren Hamilton, Wayne Mountjoy
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Fossilized Life in Subseafloor Ultramafic Rocks

Geomicrobiology Journal, 2018
Ultramafic rocks are hypothesized to support a subseafloor hydrogen-driven biosphere because of extensive production of bioavailable energy sources like H2 or CH4 from fluid-rock interactions.
M. Ivarsson, W. Bach, C. Broman, A. Neubeck, S. Bengtson   +4 more
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Aragonite from deep sea ultramafic rocks

Geochimica et Cosmochimica Acta, 1980
Abstract Aragonite mineralization was observed in serpentinized peridotites from the Romanche and Vema Fracture Zones in the Atlantic and the Owen Fracture Zone in the Indian Ocean, either in veins or as radial aggregates in cavities within the serpentinites. Evidence of incipient dissolution of the aragonite crystals was observed in one case.
E. Bonatti, J.R. Lawrence, P.R. Hamlyn, D. Breger   +3 more
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Geotectonic significance of ultramafic rocks

Earth-Science Reviews, 1973
Abstract Ultramafic rocks can be divided into 5 principal geotectonic groups, as follows: (1) Layered gabbro-norite-peridotite masses, commonly associated with all ages of terrane, possibly connected with accretionary plate margins. (2) Concentrically zoned Alaska-type bodies, possibly associated with consuming plate margins. (3) Ultramafic lavas and
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Rare-Earth abundances in some ultramafic rocks

Journal of Geophysical Research, 1971
A survey has been made of the abundances of the rare earths (REE) in ultramafic rocks. Samples analyzed were taken from alpine regions, layered intrusions, basaltic nodules, and kimberlite pipes. A wide range of REE concentrations and relative abundances was found.
Frederick A. Frey, Larry A. Haskin, Mary A. Haskin   +2 more
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Hydrogen Production from Mafic/Ultramafic Rocks

SPE Annual Technical Conference and Exhibition
Abstract Hydrogen is a clean fuel which can be burnt without any carbon emissions. To minimize greenhouse gas emissions, humanity would need a significant amount of hydrogen as a fuel. The goal of this work is to understand the mechanisms of geological production of hydrogen in mafic and ultramafic rocks.
K. Panthi, C. V. Oeiyono, K. K. Mohanty
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Metasomatic Alteration of Ultramafic Rocks

1989
Metasomatized 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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On the Origin of Ultramafic Rocks

Geological Society of America Bulletin, 1971
It is argued that most alpine ultramafic bodies originated as cumulates in basic magma chambers high in the crust. From some of these chambers, magmas were intruded upward or extruded, leaving sill-like ultramafites behind. These were subsequently folded or dismembered by faulting, and, because of their high density, subsided during tectonism, to form ...
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Alpine ultramafic rocks of southwestern British Columbia

Canadian Journal of Earth Sciences, 1982
Ultramafic rocks of the Hozameen, Bridge River, and Cache Creek ophiolite assemblages show much variety. The Coquihalla belt of the Hozameen ophiolite assemblage, almost completely serpentinized, is elongate, narrow, and lies along a major fault. Three ultramafic bodies from the Bridge River ophiolite differ markedly from each other.
R. L. Wright, Joe Nagel, K. C. McTaggart
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Ultramafic rocks in Angleseytheir non-tectonic emplacement

Journal of the Geological Society, 1975
The ophiolitic suite of Monian rocks in Anglesey has been regarded as segments of oceanic crust or upper mantle and sediments that were tectonically emplaced by cold shearing or thrusting during plate subduction. These processes are inconsistent with the field evidence.
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