Hydrothermal activity on near-arc sections of back-arc ridges: Results from the Mariana Trough and Lau Basin

摘要: [1] The spatial density of hydrothermal venting is strongly correlated with spreading rate on mid-ocean ridges (with the interesting exception hot spot–affected ridges), evidently because a reliable proxy for magma budget. This correlation remains untested in back-arc basins, where budget may be complicated by subduction-induced variations melt supply. To address this uncertainty, we conducted plume surveys along slow-spreading (40–60 mm/yr) and arc-proximal (10–60 km distant) sections southern Mariana Trough Valu Fa Ridge (Lau Basin). On both found multiple plumes overlying ∼15–20% total length each section, coverage comparable to at similar rates. These conditions contrast earlier reported results from two nearest-arc segments faster (60–70 ridge, East Scotia Ridge, which approaches no closer than 100 its arc. There, relatively scarce (∼5% coverage) ridge characteristics are distinctly slow-spreading: small central volcanic highs bookended deep median valleys, axial lenses restricted highs. Two factors contribute an unexpectedly low these segments: they lie too far adjacent arc benefit near-arc sources supply, subduction-aided migration mantle Bouvet spot reduce circulation local crustal warming thickening, analogous Reykjanes Ridge. Thus pattern among three appears mirror larger global defined ridges: well-defined trend versus activity most sections, plus subset unusual delivery diminish expected activity.