Thin crust, ultramafic exposures, and rugged faulting patterns at the Mid-Atlantic Ridge (22°-24°N)

• Published in: Geology (Boulder) 1995-01, Vol.23 (1), p.49-52
• Main Authors: Cannat, Mathilde, Mével, Catherine, Maia, Marcia, Deplus, Christine, Durand, Cécile, Gente, Pascal, Agrinier, Pierre, Belarouchi, Abdel, Dubuisson, Gilles, Humler, Eric, Reynolds, Jennifer
• Format: Article
• Language: English
• Subjects: Atlantic Ocean; crust; dredged samples; faults; gabbros; Geophysics; gravity anomalies; igneous and metamorphic rocks; igneous rocks; intrusions; Leg 109; Leg 153; Marine; Mid-Atlantic Ridge; mid-ocean ridges; North Atlantic; oblique-slip faults; Ocean Drilling Program; ocean floors; oceanic crust; Oceans; patterns; Petrology; Plate tectonics; plutonic rocks; solid Earth (tectonophysics); strike-slip faults; Structural geology; tectonics; thickness; topography; ultramafics
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/0091-7613(1995)023<0049:TCUEAR>2.3.CO;2

Off-axis rock sampling in the lat 22°-24°N region of the Mid-Atlantic Ridge shows that the emplacement of mantle-derived rocks in the sea floor has been a common process there for the past few million years. We find a good correlation between domains of positive residual gravity anomalies (inferred to have a thin crust) and the distribution of ultramafic samples. We also find that thin-crust domains have a rugged topography, thought to reflect strong tectonic disruption. We propose that these thin-crust domains are made of tectonically uplifted ultramafic rocks, with gabbroic intrusions and a thin basaltic cover. We also suggest that strong tectonic disruption may be a direct consequence of the lithological and rheological heterogeneity of these thin-crust domains.