Understanding of the style of extension and the architecture of oceanic crust ― Drilling through the upper oceanic crust off-Hawaii

International Conference on Ophiolites and the Oceanic Lithosphereによる発表資料金沢大学理工研究域地球社会基盤学系conference pape

Asymmetric Electrical Structure in the Mantle Beneath the East Pacific Rise at 17°S

The magnetotelluric component of the Mantle Electromagnetic and Tomography (MELT) Experiment measured the electrical resistivity structure of the mantle beneath the fast-spreading southern East Pacific Rise (EPR). The data reveal an asymmetric resistivity structure, with lower resistivity to the west of the ridge. The uppermost 100 kilometers of mantle immediately to the east of the ridge is consistent with a dry olivine resistivity structure indicating a mantle depleted of melt and volatiles. Mantle resistivities to the west of the ridge are consistent with a low-melt fraction (about 1 to 2 percent interconnected melt) distributed over a broad region and extending to depths of about 150 kilometers. The asymmetry in resistivity structure may be the result of asymmetric spreading rates and a westward migration of the ridge axis and suggests distinct styles of melt formation and delivery in the mantle beneath the two plates.</jats:p