Magnetic structure of an oceanic core complex at the southernmost Central Indian Ridge: Analysis of shipboard and deep-sea three-component magnetometer data

• Published in: Geochemistry, geophysics, geosystems : G3 Vol. 10; no. 6; pp. Q06003 - n/a
• Main Authors: Sato, Taichi, Okino, Kyoko, Kumagai, Hidenori
• Format: Journal Article
• Language: English
• Published: American Geophysical Union 01.06.2009; Blackwell Publishing Ltd
• Subjects: magnetic anomaly; Marine Geology and Geophysics; mid-ocean ridge; Midocean ridge processes; morphology; oceanic core complex; ROV, AUV, submersibles; Seafloor morphology, geology, and geophysics; Submergence instruments; submersible survey; ISW, Indian Ocean, Central Indian Ridge; A, Mid-Atlantic Ridge; mid-ocean ridge; morphology; magnetic anomaly; oceanic core complex; submersible survey
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2008GC002267

We investigated the magnetic structure of an oceanic core complex (OCC) at the southernmost Central Indian Ridge (CIR) near 25°S on the basis of newly collected magnetic and bathymetric data and submersible dives. The OCC is located off‐axis on the western flank of the CIR and is characterized by typical megamullion morphology with flow line–parallel corrugations. The OCC is similar in size to those found along the Mid‐Atlantic Ridge (MAR), but the CIR OCC formed in an estimated 0.8 Ma, which is slightly shorter than the average time for the formation of OCCs along the MAR. The magnetization intensity over the CIR OCC is quite weak compared to that over adjacent seafloor of the same age. Mostly gabbroic rocks were recovered from outcrops during submersible dives. Fault rocks were also recovered from the corrugated surface, suggesting that the OCC surface represents the plane of a detachment fault. Although the magnetization intensity is rather low, we were able to identify the Brunhes‐Matuyama boundary and the Jaramillo and Olduvai subchrons on and around the OCC using vector magnetic analysis. Over the OCC, the Jaramillo subchron, which cannot be recognized from magnetic data acquired at the sea surface, was identified using data from a magnetometer attached to a submersible. The locus of this subchron is consistent with that observed over the seafloor adjacent to the OCC. Combining the results of magnetic survey and rock sampling, we would like to point out the possibility that the gabbroic rocks constituted the OCC and preserved seafloor‐spreading history, although there are several interpretations of the low magnetization.