Metabasalts from the Mid-Atlantic Ridge: new insights into hydrothermal systems in slow-spreading crust
Article Abstract:
Samples of hydrothermally altered basaltic rocks from the Mid-Atlantic Ridge, south of Kane Fracture Zone (MARK) were analysed in order to study the processes of hydrothermal alteration in a crustal segment formed at a slow- spreading ridge.The samples were reflective of the MARK environment and were classified into two distinct types. It was suggested that the mineral assemblages in these rocks reflect the total effects of several hydrothermal events. Type I metabasalt formed at 180 to 300 degrees Celsius while type II formed at 250 to over 450 degrees Celsius. Geochemical analysis of the rock types indicate that they were formed under conditions of low water to rock ratio.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1993
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Melting of metasomatized subcontinental lithosphere: undersaturated mafic lavas from Rungwe, Tanzania
Article Abstract:
The melts of metasomatized garnet peridotite are responsible for the formation of mafic alkalic lavas in Rungwe, Tanzania. Minor metasomatic phases in the source area during melting control the geochemical elements of the lava. Carbonatite metasomatism may be the major process. Geochemical analysis of the lava shows the presence of residual garnet in the source for nephelinites. Major rift faults separate volcanoes with varying geochemistry.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1995
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Fluid flow in subduction zones: evidence from Nd- and Sr-isotope variations in metabasalts of the Franciscan complex, California
Article Abstract:
A study of Nd- and Sr-isotope variations in metabasaltic blocks, of the Franciscan complex, California, gives information on the nature of fluid metasomatism in the upper levels of paleosubduction zone. The study also tells about the types of rocks that produced hydrous fluids and the origin of the basaltic rocks. Sea water alteration in ocean-floor hydrothermal system changes the protoliths.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1995
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