Archive · dataset · 1988
Chemistry of minerals of ODP Hole 103-637A peridotites
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The Galicia margin lies northwest of the Iberian Peninsula and is a passive ocean margin with thin sedimentary cover.
Description
Altered peridotite was recovered from ODP Site 637, on the north-trending ridge at the western edge of the margin, near the oceanic/continental crust boundary.The altered ultramafics were originally clinopyroxene-rich upper mantle harzburgites and are now extensively serpentinized (>85%) and cut by very late-stage carbonate veins.
Despite pervasive late, low-temperature alteration, evidence of early, high-temperature alteration remains. Alteration is apparent as (1) amphibole rims on clinopyroxene (>800°C), (2) hornblende + tremolite (450° to 800°C), (3) breakdown of hornblende to form tremolite + chlorite (<450°C), (4) zoned Cr-spinels, (5) hydration of orthopyroxene and olivine to serpentine, (6) serpentine veins, (7) replacement of pyroxene and olivine by calcite, and (8) calcite veins and vugs.Both the relict igneous and the high-temperature alteration minerals (amphiboles) show evidence of brittle deformation.
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Subsequent low-temperature alteration veins and minerals are deformed only in faulted and brecciated zones. This textural evidence suggests that the low-temperature alteration occurred after emplacement of the ultramafics at the surface. Serpentine fills tension fractures in orthopyroxene, and both serpentine and calcite fill tension cracks in olivine.The high-temperature alterations in these samples are similar to those found in oceanic fracture zone and ophiolite ultramafics.
This widespread occurrence of high-temperature alteration suggests that hot fluids were pervasive in these ultramafic blocks.Localization of high-temperature alteration close to large carbonate veins suggests channelization of the late, low-temperature fluids. Earlier hydrations (e.g., high-temperature alterations and serpentinization) were pervasive.
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- OAI-PMH record oai.datacite.org/oai?verb=GetRecord&metadataPrefix=oai_dc&identifier=doi%3A10.1… ↗
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- Earth & Environmental Science · Ocean & Atmospheric Science
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Provenance · 1 source records, 7 field assertions
| Source | Key | Last seen | Raw |
|---|---|---|---|
| GigaDB | doi:10.1594/pangaea.743572 | 17 h ago | JSON v1 |
| Field | Assertion | Extractor | Evidence |
|---|---|---|---|
| access_level | source · gigadb org | connector:gigadb_org@1.0.0 | |
| concepts[field].local:field:earth-environmental | mapping · gigadb org | connector:gigadb_org@1.0.0 | |
| concepts[field].local:field:ocean-atmospheric | mapping · gigadb org | connector:gigadb_org@1.0.0 | |
| description | source · gigadb org | connector:gigadb_org@1.0.0 | /metadata/dc/description |
| license | source · gigadb org | connector:gigadb_org@1.0.0 | /metadata/dc/rights |
| publication_date | source · gigadb org | connector:gigadb_org@1.0.0 | |
| title | source · gigadb org | connector:gigadb_org@1.0.0 | /metadata/dc/title |