Segmentation of the Central Indian Ridge between 12°12′ S and the Indian Ocean Triple Junction

Parson, L. M.; Patriat, P.; Searle, R. C.; Briais, A.

doi:10.1007/bf01982385

Cited by 35 publications

(27 citation statements)

References 21 publications

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“…The CIR meets the Southwest Indian Ridge and the Southeast Indian Ridge at its southern end, forming a ridge-ridge-ridge triple junction (Rodriguez Triple Junction: RTJ). In the southern CIR, the ridge axis trends in an almost NNW-SSE direction and is segmented by several transform faults and non-transform offsets (Parson et al 1993;Briais 1995). Briais (1995) describes the detailed axial bathymetry between the RTJ and 20 30 0 S, and defines the axial segmentation using a sequential numbering system that increases northward starting at the RTJ.…”

Section: Regional Settingmentioning

confidence: 99%

Tectonic Background of Four Hydrothermal Fields Along the Central Indian Ridge

Okino

Nakamura

Sato

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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Since the discovery of the Kairei hydrothermal field at the southernmost end of the Central Indian Ridge (CIR) in 2000, only four active hydrothermal vent fields have subsequently been discovered. These four hydrothermal fields show remarkable diversity in the chemical compositions of fluids and associated ecosystems. Focused geophysical mapping and rock sampling indicate that different tectonic setting constrains the different hydrothermal activity for each field. Two hydrothermal fields in the southern CIR are located on the axial rift-valley wall. The hydrogen-rich Kairei hydrothermal field at 25 19 0 S is constrained by both basaltic magmatism and detachment faulting that exhume ultramafic rocks on a shallow subsurface, whereas no evidence of ultramafic exposure is recognized in the typical mid-ocean ridge type Edmond hydrothermal field at 23 52 0 S. Two other hydrothermal fields have been newly discovered in the central CIR. The Solitaire field at 19 33 0 S is located about 2.6 km away from the neo-volcanic zone and is likely influenced by intra-plate volcanism. The Dodo field at 18 20 0 S is located at the center of the axial valley floor, where a basaltic sheet-lava flow buries the seafloor. The lava morphology and the existence of an adjacent large off-axis seamount support the idea that excess melt is supplied in this segment. The anomalous magmatism is likely influenced by mantle plume components or by a large-offset transform fault just north of the segment. The large diversity found in the four hydrothermal fields along the CIR provides important insights on the tectonic control of global hydrothermal systems.

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Section: Regional Settingmentioning

confidence: 99%

Tectonic Background of Four Hydrothermal Fields Along the Central Indian Ridge

Okino

Nakamura

Sato

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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“…Eleven secondorder segments have thus been identified and numbered from the Triple Junction northward (Figure 3). The section of the CIR studied here corresponds to the super-segments A and B defined by Parson et al (1993). The 21°05'S offset corresponds to their ridgeaxis discontinuity (RAD) B-4, the 22°10'S offset is their RAD B-5, the 23°05'S offset is RAD A-I, and the …”

Section: Morphology Of Spreading Segments and Ridge Discontinuities Fmentioning

confidence: 99%

“…More recently, Schlich et al (1989) and Dyment (1991) presented a large-scale magnetic and morphological study of the CIR and its evolution since 42 Ma. From a G L O R I A side-scan sonar survey of the Central Indian Ridge, Parson et al (1993) analyzed the segmentation of the axis from 12°S to the Rodriguez Triple Junction. Fig.…”

Section: Introductionmentioning

confidence: 99%

Structural analysis of the segmentation of the Central Indian Ridge between 20�30?S and 25�30?S (Rodriguez Triple Junction)

Briais

1995

Mar Geophys Res

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Abstract. The morphological characteristics of the segmentation of the Central Indian Ridge (CIR) from the Indian Ocean Triple Junction (25°30'S) to the Egeria Transform Fault system (20°30'S) are analyzed. The compilation of Sea Beam data from R/V Sonne cruises SO43 and SO52, and R/V Charcot cruises Rodriguez t and 2 provides an almost continuous bathymetric coverage of a 450-km-long section of the ridge axis. The bathymetric data are combined with a GLORIA side-scan sonar swath to visualize the fabric of the ridge and complement the coverage in some areas. This section of the CIR has a full spreading rate of about 50 mm yr -~, increasing slightly from north to south. The morphology of the CIR is generally similar to that of a slow-spreading center, despite an intermediate spreading rate at these latitudes. The axis is marked by an axial valley 5 35 km wide and 500-1800 m deep, sometimes exhibiting a 100-600 m-high neovolcanic ridge. It is offset by only one 40-km offset transform fault (at 22°40'S), and by nine second-order discontinuities, with offsets varying from 4 to 21 km, separating segments 28 to 85 km long. The bathymetry analysis and an empirical orthogonal function analysis performed on across-axis profiles reveal morphologic variations in the axis and the second-order discontinuities. The ridge axis deepens and the relief across the axial valley increases from north to south. The discontinuities observed south of 22°S all have morphologies similar to those of the.slowspreading Mid-Atlantic Ridge. North of 22°S, two discontinuities have map geometries that have not been observed previously on slow-spreading ridges. The axial valleys overlap, and their tips curve toward the adjacent segment. The overlap distance is 2 to 4 times greater than the offset. Based on these characteristics, these discontinuities resemble overlapping spreading centers (OSCs) described on the fast-spreading EPR. The evolution of one such discontinuity appears to decapitate a nearby segment, as observed for the evolution of some OSCs on the EPR. These morphological variations of the CIR axis may be explained by an increase in the crustal thickness in the north of the study area relative to the Triple Junction area. Variations in crustal thickness could be related to a broad bathymetric anomaly centered at 19°S, 65°E0 which probably reflects the effect of the nearby R6union hotspot, or an anomaly in the composition of the mantle beneath the ridge near 19°S. Other explanations for the morphological variations include the termination of the CIR at the Rodriguez Triple Junction or the kinematic evolution of the triple junction and its resultant lengthening of the CIR. These latter * Now at: GRGS-UMR 39, CNRS, Observatoire Midi-Pyr6n6es,

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“…The Indian Ocean Ridge System with study area in inset. Figure modified after Parson et al (1993) and Briais (1995) to intra-segment variability of melting temperature are yet to be fully understood.…”

Section: Introductionmentioning

confidence: 97%

“…Morphology, regional physiographic, magnetic anomalies, and kinematic evolution of this slow-to-intermediate-spreading CIR since 42 Ma were studied (Drolia et al 2000). Using GLORIA long-range side-scan sonar and the multibeam swath echo-sounder, Parson et al (1993) and Briais (1995) mapped the segmentation of the southern CIR (SCIR, ~12°S-25.5°S) to study its morphotectonic characteristics. Petrologically, the SCIR is characterized by N-MORB, gabbro, and ultramafics, including serpentinized peridotites, talc-anthophyllite, and lherzolites (Engel and Fischer 1975;Herzig and Plüger 1988;Ray et al 2007Ray et al , 2008.…”

Section: Introductionmentioning

confidence: 99%