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  • 1
    Electronic Resource
    Electronic Resource
    Gabbroic intrusions and magmatic metasomatism in harzburgites from the Garrett transform fault: implications for the nature of the mantle–crust transition at fast-spreading ridges (1999)
    Springer
    Contributions to mineralogy and petrology 136 (1999), S. 111-130 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Mafic and ultramafic rocks sampled in the Garrett transform fault at 13°28′S on the East Pacific Rise (EPR) provide insight on magmatic processes occurring under a fast-spreading ridge system. Serpentinized harzburgite from Garrett have modal, mineral and bulk chemical compositions consistent with being mantle residue of a high degree of partial melting. Along with other EPR localities (Terevaka transform fault and Hess Deep), these harzburgites are among the most residual and depleted in magmatophile elements of the entire mid-ocean ridge system. Geothermometric calculations using olivine-spinel pairs indicate a mean temperature of 759 ± 25 °C for Garrett residual harzburgite similar to the average of 755 °C for tectonite peridotites from slow-spreading ridges. Results of this study show that mid-ocean ridge peridotites are subject to both fractional melting and metasomatic processes. Evidence for mantle metasomatism is ubiquitous in harzburgite and is likely widespread in the entire Garrett peridotite massif. Magma-harzburgite interactions are very well preserved as pyroxenite lenses, plagioclase dunite pockets or dunitic wall rock to intrusive gabbros. Abundant gabbroic rocks are found as intrusive pockets and dikes in harzburgite and have been injected in the following sequence: olivine-gabbro, gabbro, gabbronorite, and ferrogabbro. The wide variety of magmas that crystallized into gabbros contrast sharply with present-day intratransform basalts, which have a highly primitive composition. Ferrogabbro dikes have been intruded at the ridge-transform intersection and as they represent the last event of a succession of gabbros intrusive into the peridotite, they likely constrain the origin of the entire peridotite massif to the same location. In peridotite massifs from Pacific transform faults (Garrett and Terevaka), primitive to fractionated basaltic magmas have flowed and crystallized variable amounts of dunite (±plagioclase) and minor pyroxenite, followed by a succession of cumulate gabbroic dikes which have extensively intruded and modified the host harzburgitic rocks. The lithosphere and style of magmatic activity within a fast-slipping transform fault (outcrops of ultramafic massif, discontinuous gabbro pockets intrusive in peridotite, magnesian and phyric basalts) are more analogous to slow-spreading Mid-Atlantic Ridge type than the East Pacific Rise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004100050527
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Contrasting volcanic-tectonic processes during the past 2 Ma on the Mid-Atlantic Ridge: submersible mapping, petrological and magnetic results at lat. 34°52′ N and 33°55′ N (1998)
    Springer
    Marine geophysical researches 20 (1998), S. 425-458 
    Details
    ISSN: 1573-0581
    Keywords: Mid-Atlantic Ridge ; magnetic anomalies ; ocean crust ; basalts ; peridotites ; volcanic ejecta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In August–September of 1995, 20 Nautile dives and detailed magnetic surveys (spaced every 1.8 km) were undertaken on two segments of the Mid-Atlantic Ridge between the Oceanographer and Hayes fractures zones. These two segments are only 65 km apart and show strong morphology and gravity contrasts. OH1 is shallower and has a large mantle Bouguer anomaly (MBA) bull's eye, whereas OH3 is deeper and has a smaller MBA bull's eye. Thirteen dives were devoted to segment OH1. The Median Ridge (MR) located on the central high (1700 m deep) is topped by 100 to 300 m high circular volcanoes. The volcanics consists mainly of porphyritic and/or vesicular pillows and volcaniclastics. The NVZ (2200 m deep), located in the valley floor east of the MR, consists of near aphyric fluid lava flows. A chain of off-axis volcanoes, displaying a magnetic continuity with surroundings, extends on both sides of the axis. Three volcanoes on the east side and one on the west side of the axis were explored and sampled by submersible. The off-axis increase of weathering, Fe-Mn coating and magnetic signature suggest that the volcanoes were built at or near the ridge axis. The spacing of NS elongated hills bearing circular volcanoes and separated large magnetic signature (2 to 4 km) depressions suggests that several similar volcanic events occured during the past 2 Ma. The last 1 Ma episode involves (1) the construction of an axial ridge (MR) by fissure eruptions and the formation of circular summit volcanoes by focused volcanism, and (2) the extrusion of fluid magma in the depressions formed by further fissuring and faulting of the MR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004760111160
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    Paper (German National Licenses)
    Fulltext
  • 3
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    Supplementary data - Geological maps of the Réservoir Blanc, Rochette West, and Lac à la Vase intrusions (Portneuf-Mauricie Domain, Grenville Province, Canada), doi:10.1016/j.lithos.2012.07.016 (2012)
    PANGAEA
    In:  EPIC3Bremerhaven, PANGAEA
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , notRev
    Format: application/pdf
    Format: application/pdf
    Format: application/pdf
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    PAPER (OA)
  • 4
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    CO2-depleted warm air venting from chrysotile milling waste (Thetford Mines, Canada): Evidence for in-situ carbon capture from the atmosphere (2012)
    Geological Society of America (GSA)
    Details
    Publication Date: 2012-03-01
    Description: We have discovered diffuse warm air vents at the surface of a chrysotile milling waste heap at the Black Lake mine, Thetford Mines, Québec, Canada. The venting areas are inconspicuous, except in winter when the vents form snow-free areas of unfrozen ground, each with a surface area of 1–15 m2. The temperature and chemical composition of the warm air vents have been monitored from March 2009 to July 2010. The temperature of the warm air and ground surface at the venting sites ranged from 6.6 to 20.0 °C, whereas that of the ambient air ranged from –13.2 to 20.0 °C. The difference between atmospheric and vent air temperatures is greater in cold-weather months. The warm air has low CO2 content, but has otherwise normal atmospheric gas composition. Warm air volumetric flow varies from 2.1 to 19.9 L/m2/s in winter, when it contains between
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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    PAPER CURRENT
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