Although the source layer for marine magnetic anomalies has been assumed to be the extrusive basalts of uppermost ocean crust, recent studies indicate that lower crustal rocks may also contribute. Because the temperature at which magnetization of crustal rocks achieves long-term stability is crucial to any source layer contribution, we undertook hightemperature VRM (viscous remanent magnetizati...

Abstract Most efforts to characterize the size and composition of mantle that complements continental crust have assumed mid‐ocean ridge basalt (MORB) source is incompatible‐element depleted residue extraction. The use Nd isotopes model this process led conclusion “depleted MORB reservoir” confined upper ∼30% mantle, leaving lower in a more “primitive” state. Here, we Nb/U Ta/U evaluate mass re...

The RIDGE2000 program (R2K) is designed to further understanding of the geophysical, geochemical and geobiological causes and consequences of energy and material transfer, from the Earth’s mantle to the hydrosphere and biosphere, along the globe-encircling mid-ocean ridge system. Three sites on the ridge are the focus of detailed R2K studies that will integrate information at various scales to ...

Forested ecosystems diversified more than 350 Ma to become major engines of continental silicate weathering, regulating the Earth's atmospheric carbon dioxide concentration by driving calcium export into ocean carbonates. Our field experiments with mature trees demonstrate intensification of this weathering engine as tree lineages diversified in concert with their symbiotic mycorrhizal fungi. P...

The origin and stability of deep-mantle melts, and the magmatic processes at different times of Earth's history are controlled by the physical properties of constituent silicate liquids. Here we report density functional theory-based simulations of model basalt, hydrous model basalt and near-MORB to assess the effects of iron and water on the melt structure and density, respectively. Our result...

Abstmct: Island arc lavas from New Britain and the Marianas have 143 Nd/144 Nd similar to other oceanic basalts and distinctly different from continental flood basalts and thus appear to be derived from a high Sm/Nd, light-REE-depleted reservoir. Consideration of both Nd and Sr isotopes suggests seawater involvement in the generation of some island arc lavas and thus indicates that they may be ...

Figure 11 Average depth of magma lens reflections beneath ridges versus spreading rate. The curved line shows the depth to the 12003C isotherm calculated from the ridge thermal model of Phipps Morgan J and Chen YJ (1993) Journal of Geophysical Research 98: 6283}6297. Data from different ridges are labeled Reykjanes Ridge (RR), Juan de Fuca Ridge (JdF), Costa Rica Rift (CRR), Lau Basin (Lau), no...

The population divergence process of deep-sea vent invertebrates is driven by both biotic (e.g., dispersal during the larval stage) and abiotic factors such as deep-ocean currents, depth, geological setting vents. However, little known regarding hydrothermal microorganisms. Therefore, our study sought to investigate influence geographic on symbiotic bacteria Bathymodiolus mussels. genetic diffe...

Abstract The continental crust is strongly depleted in iron relative to mid-oceanic ridge basalt, broadly identical the calc-alkaline magmas, suggesting that differentiation key continent formation. However, it remains contentious as what drives Fe depletion during magmatic crust. two competing hypotheses for differentiation—magnetite versus garnet (± amphibole) fractionation—predict contrastin...

[1] Strontium and neodymium radiogenic isotope ratios in early to middle Eocene fossil fish debris (ichthyoliths) from Lomonosov Ridge (Integrated Ocean Drilling Program Expedition 302) help constrain water mass compositions in the Eocene Arctic Ocean between !55 and !45 Ma. The inferred paleodepositional setting was a shallow, offshore marine to marginal marine environment with limited connect...