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As opposed to ocean crustal drilling that often yields a discontinuous core, ophiolites provide a unique opportunity to study continuous sections of oceanic basalts. In order to provide high frequency constraints on the construction of... more
As opposed to ocean crustal drilling that often yields a discontinuous core, ophiolites provide a unique opportunity to study continuous sections of oceanic basalts. In order to provide high frequency constraints on the construction of the upper oceanic crust, a continuous 280 m thick volcanic transect was sampled in the Semail ophiolite in Oman. The analyzed section is located in the
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The eastern end of the Haylayn massif exposes a complex paleoridge structure interpreted as the tip of a northwest- ward propagating segment (Nicolas et al., this issue). The area, revisited from a petrostructural and geochemical... more
The eastern end of the Haylayn massif exposes a complex paleoridge structure interpreted as the tip of a northwest- ward propagating segment (Nicolas et al., this issue). The area, revisited from a petrostructural and geochemical viewpoint, offers the most documented exposures of the association of olivine gabbros and gabbronorites in Oman (Juteau et al., 1988). Gabbronorites were injected while the
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Three-quarters of the oceanic crust formed at fast-spreading ridges is composed of plutonic rocks whose mineral assemblages, textures and compositions record the history of melt transport and crystallization between the mantle and the sea... more
Three-quarters of the oceanic crust formed at fast-spreading ridges is composed of plutonic rocks whose mineral assemblages, textures and compositions record the history of melt transport and crystallization between the mantle and the sea floor. Despite the importance of these rocks, sampling them in situ is extremely challenging owing to the overlying dykes and lavas. This means that models for understanding the formation of the lower crust are based largely on geophysical studies and ancient analogues (ophiolites) that did not form at typical mid-ocean ridges. Here we describe cored intervals of primitive, modally layered gabbroic rocks from the lower plutonic crust formed at a fast-spreading ridge, sampled by the Integrated Ocean Drilling Program at the Hess Deep rift. Centimetre-scale, modally layered rocks, some of which have a strong layering-parallel foliation, confirm a long-held belief that such rocks are a key constituent of the lower oceanic crust formed at fast-spreading...
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I. ABSTRACT In recent years there has been a profound rise in appreciation of the importance that exposure of mantle material, and resultant reactions with seawater to produce serpentinite play as fundamental, and central Earth processes.... more
I. ABSTRACT In recent years there has been a profound rise in appreciation of the importance that exposure of mantle material, and resultant reactions with seawater to produce serpentinite play as fundamental, and central Earth processes. Serpentinization profoundly affects the rheology, gravity, and seismic structure of ocean crust formed by slow-spreading. Because magnetite is a product of serpentinization, hydration of olivine-rich rocks has a major effect on the magnetic signature of the ocean floor. The geochemical consequences of serpentinization are also important to sea floor studies. Serpentinite-hosted hydrothermal vents are common along slow and ultraslow spreading ridges. These vents host unique microbiological ecosystems supported by hydrogen and methane released during peridotite- seawater interactions. Serpentinization is also common away from mid-ocean ridges, in fore-arc regions and at rifted continental margins. Serpentine formation and dehydration plays a dominant...
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The Early Cretaceous Ontong Java Plateau (OJP) represents by far the largest igneous event on Earth in the last 200 Ma and yet, despite its size, the OJP's basaltic crust appears to be remarkably homogeneous in composition. The most... more
The Early Cretaceous Ontong Java Plateau (OJP) represents by far the largest igneous event on Earth in the last 200 Ma and yet, despite its size, the OJP's basaltic crust appears to be remarkably homogeneous in composition. The most abundant rock type is a uniform low-K tholeiite, represented by the Kwaimbaita Formation on Malaita and found at all but one