Magmatic activities on the Southwest Indian Ridge between 35°E and 40°E, the closest segment to the Marion hotspot. (20th December 2013)

• Record Type: Journal Article
• Authors: Sato, Taichi; Okino, Kyoko; Sato, Hiroshi; Mizuno, Mariko; Hanyu, Tomoko; Seama, Nobukazu
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 14:Number 12(2013)
• Page Start: 5286
• Page End: 5307
• Publication Date: 2013-12-20
• Subjects: Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1002/2013GC004814
• Languages: English
• ISSNs: 1525-2027

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p>[1] We conducted geophysical surveys, including bathymetry, gravity, and magnetism, within a first‐order segment of the Southwest Indian Ridge (SWIR) between the Prince Edward and Eric Simpson fracture zones (FZs) (latitude 35°–40°E, segment PE), in the vicinity of the Marion hotspot. Segment PE includes four orthogonally spreading second‐order segments (PE‐1, PE‐2, PE‐3, and PE‐4) and a long, oblique axial valley (NTD‐1). Segments PE‐1, PE‐2, and PE‐4 are magmatic, whereas segment PE‐3 and NTD‐1 are characterized by low magmatic activity. Segment PE‐3 is a nascent segment and NTD‐1 contains three tiny magmatic sections. Each low‐magmatic interval along the axis of segment PE lies between two magmatic segments. This segmentation pattern is similar to the SWIR between the Gallieni and Melville FZs; therefore, a strong melt‐focusing process can be expected. Different characteristics of second‐order magmatic segments suggest that the magmatic activity in each segment varies among each other as well as that of the other segments of SWIR. Continuous seafloor morphology and isochrons over off‐axis areas of segment PE‐1 and NTD‐1 suggest that PE‐1 shortened after the C2An chron. The V‐shaped bathymetric structure between segment PE‐1 and NTD‐1 suggests that the melt supply center has migrated westward. This westward melt migration would have reduced magmatic activity at NTD‐1 after C2An. Ridge obliquity may also have reduced magmatic activity. Geophysical characteristics of second‐order segments suggest that magmatic activity of segment PE is mainly controlled by a strong melt‐focusing process and a comparatively low contribution of melt supply from Marion hotspot.</p> </abstract>