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

Research Article| August 01, 1991 Geology of the northern Cleft segment, Juan de Fuca Ridge: Recent lava flows, sea-floor spreading, and the formation of megaplumes R. W. Embley; R. W. Embley 1NOAA, Pacific Marine Environmental Laboratory, Hatfield Marine Science Center, Newport, Oregon 97365 Search for other works by this author on: GSW Google Scholar W. Chadwick; W. Chadwick 2CIMRS, Oregon State University, Hatfield Marine Science Center, Newport, Oregon 97365 Search for other works by this author on: GSW Google Scholar M. R. Perfit; M. R. Perfit 3Department of Geology, University of Florida, Gainesville, Florida 32611 Search for other works by this author on: GSW Google Scholar E. T. Baker E. T. Baker 4NOAA, Pacific Marine Environmental Laboratory, Sand Point Way, Seattle, Washington 98115-0070 Search for other works by this author on: GSW Google Scholar Author and Article Information R. W. Embley 1NOAA, Pacific Marine Environmental Laboratory, Hatfield Marine Science Center, Newport, Oregon 97365 W. Chadwick 2CIMRS, Oregon State University, Hatfield Marine Science Center, Newport, Oregon 97365 M. R. Perfit 3Department of Geology, University of Florida, Gainesville, Florida 32611 E. T. Baker 4NOAA, Pacific Marine Environmental Laboratory, Sand Point Way, Seattle, Washington 98115-0070 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1991) 19 (8): 771–775. https://doi.org/10.1130/0091-7613(1991)019<0771:GOTNCS>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation R. W. Embley, W. Chadwick, M. R. Perfit, E. T. Baker; Geology of the northern Cleft segment, Juan de Fuca Ridge: Recent lava flows, sea-floor spreading, and the formation of megaplumes. Geology 1991;; 19 (8): 771–775. doi: https://doi.org/10.1130/0091-7613(1991)019<0771:GOTNCS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract 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. Our 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. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.