Characterization of the in situ magnetic architecture of oceanic crust (Hess Deep) using near-source vector magnetic data
Tivey, Maurice A.
MacLeod, Christopher J.
Lissenberg, C. Johan
Shillington, Donna J.
Ferrini, Vicki L.
MetadataShow full item record
Marine magnetic anomalies are a powerful tool for detecting geomagnetic polarity reversals, lithological boundaries, topographic contrasts, and alteration fronts in the oceanic lithosphere. Our aim here is to detect lithological contacts in fast-spreading lower crust and shallow mantle by characterizing magnetic anomalies and investigating their origins. We conducted a high-resolution, near-bottom, vector magnetic survey of crust exposed in the Hess Deep “tectonic window” using the remotely operated vehicle (ROV) Isis during RRS James Cook cruise JC21 in 2008. Hess Deep is located at the western tip of the propagating rift of the Cocos-Nazca plate boundary near the East Pacific Rise (EPR) (2°15′N, 101°30′W). ROV Isis collected high-resolution bathymetry and near-bottom magnetic data as well as seafloor samples to determine the in situ lithostratigraphy and internal structure of a section of EPR lower crust and mantle exposed on the steep (~20°dipping) south facing slope just north of the Hess Deep nadir. Ten magnetic profiles were collected up the slope using a three-axis fluxgate magnetometer mounted on ROV Isis. We develop and extend the vertical magnetic profile (VMP) approach of Tivey (1996) by incorporating, for the first time, a three-dimensional vector analysis, leading to what we here termed as “vector vertical magnetic profiling” approach. We calculate the source magnetization distribution, the deviation from two dimensionality, and the strike of magnetic boundaries using both the total field Fourier-transform inversion approach and a modified differential vector magnetic analysis. Overall, coherent, long-wavelength total field anomalies are present with a strong magnetization contrast between the upper and lower parts of the slope. The total field anomalies indicate a coherently magnetized source at depth. The upper part of the slope is weakly magnetized and magnetic structure follows the underlying slope morphology, including a “bench” and lobe-shaped steps, imaged by microbathymetry. The lower part of the slope is strongly magnetized, with a gradual reduction in amplitude from east to west across the slope. Surface morphology and recent drilling results indicate that the slope has been affected by mass wasting, but the observation of internally coherent magnetization distributions within the upper and lower slopes suggest that the disturbance is surficial. We attribute the spatial differences in magnetization distribution to the combination of changes in in situ lithology and depth to the source. These survey lines document the first magnetic profiles that capture the gabbro-ultramafic and possibly dike-gabbro boundaries in fast-spreading lower crust.
© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Geophysical Research: Solid Earth 121 (2016): 4130–4146, doi:10.1002/2015JB012783.
Suggested CitationArticle: Tominaga, Masako, Tivey, Maurice A., MacLeod, Christopher J., Morris, Antony, Lissenberg, C. Johan, Shillington, Donna J., Ferrini, Vicki L., "Characterization of the in situ magnetic architecture of oceanic crust (Hess Deep) using near-source vector magnetic data", Journal of Geophysical Research: Solid Earth 121 (2016): 4130–4146, DOI:10.1002/2015JB012783, https://hdl.handle.net/1912/8417
The following license files are associated with this item:
Showing items related by title, author, creator and subject.
Investigation of a marine magnetic polarity reversal boundary in cross section at the northern boundary of the Kane Megamullion, Mid-Atlantic Ridge, 23°40′N Xu, Min; Tivey, Maurice A. (John Wiley & Sons, 2016-05-12)Near-bottom magnetic field measurements made by the submersible Nautile during the 1992 Kanaut Expedition define the cross-sectional geometry of magnetic polarity reversal boundaries and the vertical variation of crustal ...
Magnetic character of a large continental transform : an aeromagnetic survey of the Dead Sea Fault ten Brink, Uri S.; Rybakov, Michael; Al-Zoubi, Abdallah S.; Rotstein, Yair (American Geophysical Union, 2007-07-13)New high-resolution airborne magnetic (HRAM) data along a 120-km-long section of the Dead Sea Transform in southern Jordan and Israel shed light on the shallow structure of the fault zone and on the kinematics of the plate ...
Tominaga, Masako; Sager, William W. (John Wiley & Sons, 2010-05-12)The current M-anomaly geomagnetic polarity timescale (GPTS) is mainly based on the Hawaiian magnetic lineations in the Pacific Ocean. M-anomaly GPTS studies to date have relied on a small number of magnetic profiles, a ...