Active Basalt Alteration at Supercritical Conditions in a Seawater‐Recharged Hydrothermal System: IDDP‐2 Drill Hole, Reykjanes, Iceland
نویسندگان
چکیده
The 4.5 km deep IDDP-2 drill hole was drilled at Reykjanes, Iceland, in an active seawater-recharged hydrothermal system on the landward extension Mid-Atlantic Ridge. Drilling targeted a well-defined up-flow zone feeding Reykjanes geothermal reservoir, which produces fluids compositionally equivalent to basalt-hosted sea vents. Spot cores recovered from depths between 3,648 4,659 m consist of pervasively altered sheeted diabase dikes. shallowest core has alteration mineral assemblage similar producing reservoir but is being overprinted by underlying Hornblende Zone dominated labradorite and hornblende. deepest cored section (4,634–4,659 m) retains diabasic texture, all primary minerals are replaced or have changed composition. Plagioclase ranges An30 An99 igneous augite intergrown hornblende, clinopyroxene, orthopyroxene. Hydrothermal biotite potassium feldspar formed locally due reaction with phase-separated brine, indicated co-existing vapor-rich salt + fluid inclusions. Seawater-derived supercritical entering bottom bore actively phase separates pressure drop controlled levels hole. Felsic veins, present trace amounts, record continuous transition magmatic conditions, including incipient hydrous melting. vertical changes observed mineralogy chemistry indicate that high temperature can undergo significant cooling host rocks along their path seafloor.
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ژورنال
عنوان ژورنال: Geochemistry Geophysics Geosystems
سال: 2021
ISSN: ['1525-2027']
DOI: https://doi.org/10.1029/2021gc009747