Geology of the northern Cleft segment, Juan de Fuca Ridge: Recent lava flows, sea-floor spreading, and the formation of megaplumes

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1991)019<0771:GOTNCS>2.3.CO;2· OSTI ID:5877503

Embley, R W ^[1]; Chadwick, W ^[2]; Perfit, M R ^[3]; Baker, E T ^[4]

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1. NOAA, Newport, OR (United States)
2. Oregon State Univ., Newport (United States)
3. Univ. of Florida, Gainesville (United States)
4. Pacific Marine Environmental Lab., Seattle, WA (United States)

Geologic mapping and lava sampling were carried out after the discovery of large bursts of hydrothermal fluids (megaplumes) over the southern Juan de Fuca Ridge in 1986 and 1987. These investigations of the northernmost section of the Cleft segment have discovered: (1) semicontinuous low-temperature venting and one major high-temperature vent site along 17 km of the neovolcanic zone and (2) very glassy, lightly sedimented sheet flows and pillow mounds superimposed on older terrain over about 24 km along the northern-most part. The pillow mounds are documented to have erupted between 1981 and 1987. The occurrence of the megaplumes during this same time period strengthens the hypothesis that megaplumes are caused by sea-floor extension events. Although the basalts from the entire length of the neovolcanic zone of the Cleft segment appear to have been derived from the same mantle source, a systematic northward increase in Mg number along the segment within the neovolcanic zone indicates less shallow-level differentiation to the north, possibly related to the development of new magma chambers during the recent phase of sea-floor spreading that has occurred there.

• OSTI ID: 5877503
• Journal Information: Geology; (United States), Journal Name: Geology; (United States) Vol. 19:8; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150200 -- Geology &amp; Hydrology of Geothermal Systems
58 GEOSCIENCES
580000* -- Geosciences
ALKALINE EARTH METALS
BASALT
CHEMISTRY
ELEMENTS
FLUIDS
GEOCHEMISTRY
GEOLOGIC FORMATIONS
GEOLOGY
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
HYDROTHERMAL SYSTEMS
IGNEOUS ROCKS
LAVA
MAGNESIUM
MAPPING
METALS
PACIFIC OCEAN
ROCKS
SAMPLING
SEA-FLOOR SPREADING
SEAS
SURFACE WATERS
VOLCANIC REGIONS
VOLCANIC ROCKS