Publication Date:
2014-07-18
Description:
Multiple geological processes affect the distribution of hydrothermal venting along a mid-ocean ridge. Deciphering the role of a specific process is often frustrated by simultaneous changes in other influences. Here we take advantage of the almost constant spreading rate (65-71 mm/yr) along 2500 km of the Southeast Indian Ridge (SEIR) between 77°-99°E to examine the spatial density of hydrothermal venting relative to regional and segment-scale changes in the apparent magmatic budget. We use 227 vertical profiles of light backscatter and (on 41 profiles) oxidation-reduction potential along 27 1 st - and 2 nd -order ridge segments on and adjacent to the Amsterdam-St. Paul (ASP) Plateau to map p h , the fraction of casts detecting a plume. At the regional scale, venting on the five segments crossing the magma-thickened hotspot plateau is almost entirely suppressed ( p h = 0.02). Conversely, the combined p h (0.34) from all other segments follows the global trend of p h versus spreading rate. Off the ASP Plateau, multi-segment trends in p h track trends in the regional axial depth, high where regional depth increases and low where it decreases. At the individual segment scale, a robust correlation between p h and cross-axis inflation for 1 st -order segments shows that different magmatic budgets among 1 st -order segments are expressed as different levels of hydrothermal spatial density. This correlation is absent among 2 nd -order segments. Eighty-five percent of the plumes occur in eight clusters totaling ~350 km. We hypothesize that these clusters are a minimum estimate of the length of axial melt lenses underlying this section of the SEIR.
Electronic ISSN:
1525-2027
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
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