Hydrothermal Deposits on the East Pacific Rise Near 13° N: Geological Setting and Distribution of Active Sulfide Chimneys

The study of a fast spreading segment (12 cm y−1, full rate) of the East Pacific Rise (E.P.R.) near 12°50’N explored in detail by a surface ship in 1981 and by a manned submersible in 1982 revealed the existence of intense hydrothermal activity on the Rise crest. In the area of study (600 Km), the Rise crest (regional depth 2600 m) is about 1500 m wide and is occupied in its center by a linear graben (> 300 m wide and 50 m deep) bordered by vertical scarps. The Rise flank topography (near the 2800 m contour line) is limited by linear fault scarps and by four volcanoes located at about 1 Km, 6 Km and 18 Km from the accreting plate boundary. The general orientation of the Rise and graben is N 165°.