<abstract xmlns="http://www.w3.org/1999/xhtml"><p>The mantle is the most voluminous part of the Earth. However, mantle petrologists usually have to rely on indirect geophysical methods or on material found ex situ. In this review paper, we point out the in-situ existence of oceanic core complexes (OCCs), which provide large exposures of mantle and lower crustal rocks on the seafloor on detachment fault footwalls at slow-spreading ridges. OCCs are a common structure in oceanic crust architecture of slow-spreading ridges. At least 172 OCCs have been identified so far and we can expect to discover hundreds of new OCCs as more detailed mapping takes place. Thirty-two of the thirty-nine OCCs that have been sampled to date contain peridotites. Moreover, peridotites dominate in the plutonic footwall of 77% of OCCs. Massive OCC peridotites come from the very top of the melting column beneath ocean ridges. They are typically spinel harzburgites and show 11.3–18.3% partial melting, generally representing a maximum degree of melting along a segment. Another key feature is the lower frequency of plagioclase-bearing peridotites in the mantle rocks and the lower abundance of plagioclase in the plagioclase-bearing peridotites in comparison to transform peridotites. The presence of plagioclase is usually linked to impregnation with late-stage melt. Based on the above, OCC peridotites away from segment ends and transforms can be treated as a new class of abyssal peridotites that differ from transform peridotites by a higher degree of partial melting and lower interaction with subsequent transient melt.</p></abstract>

The mantle is the most voluminous part of the Earth. However, mantle petrologists usually have to rely on indirect geophysical methods or on material found ex situ. In this review paper, we point out the in-situ existence of oceanic core complexes (OCCs), which provide large exposures of mantle and lower crustal rocks on the seafloor on detachment fault footwalls at slow-spreading ridges. OCCs are a common structure in oceanic crust architecture of slow-spreading ridges. At least 172 OCCs have been identified so far and we can expect to discover hundreds of new OCCs as more detailed mapping takes place. Thirty-two of the thirty-nine OCCs that have been sampled to date contain peridotites. Moreover, peridotites dominate in the plutonic footwall of 77% of OCCs. Massive OCC peridotites come from the very top of the melting column beneath ocean ridges. They are typically spinel harzburgites and show 11.3–18.3% partial melting, generally representing a maximum degree of melting along a segment. Another key feature is the lower frequency of plagioclase-bearing peridotites in the mantle rocks and the lower abundance of plagioclase in the plagioclase-bearing peridotites in comparison to transform peridotites. The presence of plagioclase is usually linked to impregnation with late-stage melt. Based on the above, OCC peridotites away from segment ends and transforms can be treated as a new class of abyssal peridotites that differ from transform peridotites by a higher degree of partial melting and lower interaction with subsequent transient melt.

Mantle rock exposures at oceanic core complexes along mid-ocean ridges

Institute of Geology, Adam Mickiewicz University, Institute of Geology, Maków polnych 16, 61-606 Poznań, Poland

Institut für Mineralogie, Leibniz Universität Hannover, Callinstrasse 3, 30167 Hannover, Germany

Department of Geology and Geophysics, Woods Hole Oceanographic Institution, MS #8, McLean Laboratory, Woods Hole MA 02543-1539, USA

Geologos

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

{"article-title":"Mantle rock exposures at oceanic core complexes along mid-ocean ridges"}

The mantle is the most voluminous part of the Earth. However, mantle petrologists usually have to rely on indirect geophysical methods or on material found ex...

Mantle rock exposures at oceanic core complexes along mid-ocean ridges

Published Online: Jan 22, 2016

Page range: 207 - 231

Received: Dec 15, 2014

Accepted: Jun 13, 2015

DOI: https://doi.org/10.1515/logos-2015-0017

Keywords
peridotite, OCC, detachment fault, megamullion, slow-spreading ridge

© 2015 Jakub Ciazela et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Mantle rock exposures at oceanic core complexes along mid-ocean ridges

Published Online: Jan 22, 2016

Page range: 207 - 231

Received: Dec 15, 2014

Accepted: Jun 13, 2015

DOI: https://doi.org/10.1515/logos-2015-0017

Keywordsperidotite, OCC, detachment fault, megamullion, slow-spreading ridge

© 2015 Jakub Ciazela et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
peridotite, OCC, detachment fault, megamullion, slow-spreading ridge