期刊
JOURNAL OF PETROLOGY
卷 49, 期 9, 页码 1579-1588出版社
OXFORD UNIV PRESS
DOI: 10.1093/petrology/egn038
关键词
serpentinization; rodingite; Integrated Ocean Drilling Program Expeditions 304 and 304; IODP hole U1309D; ocean floor metamorphism; silica activity
资金
- JOI [48299]
- Virginia Museum of Natural History
- Natural Environment Research Council [NE/D001366/1] Funding Source: researchfish
- NERC [NE/D001366/1] Funding Source: UKRI
Olivine-rich troctolites of Integrated Ocean Drilling Program hole U1309D contain abundant veins along which the olivine has been serpentinized. Where the serpentinite veins cut plagioclase the plagioclase has been altered to prehnite and in many places the prehnite in the core of the vein has been altered to grossular. We show that these Ca-rich assemblages, which we call micro-rodingites, need not have formed by Ca-metasomatism. Instead the micro-rodingites could have occurred during serpentinization as a nearly closed-system process (apart from the addition of water and release of H(2) and Na(+)). We argue that in these rocks the alteration of plagioclase occurred as a result of the very low silica activity that accompanies serpentinization. The reaction of plagioclase to prehnite and prehnite to grossular provided a source of SiO(2) that allowed olivine to hydrate to serpentine without producing much brucite. Excess Al(2)O(3) produced by the alteration of plagioclase reacted with serpentine to produce chlorite and additional SiO(2).
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