Ridge propagation, oceanic core complexes, and ultramafic-hosted hydrothermalism at Rainbow (MAR 36°N): insights from a multi-scale magnetic exploration
Abstract
The Rainbow Hill is one of the best examples of atypical oceanic core complex (OCC) - atypical because no break-away has been recognized and no clear corrugations are present on the bathymetric data. Furthermore, hydrothermal site Rainbow exhibits high temperature fluids on a ultramafic basement, associating contradicting evidences for cold, poorly magmatic seafloor spreading through tectonic denudation of the mantle (the ultramafic basement) and hot, magmatic seafloor spreading by volcanic intrusion (the high temperature hydrothermalism). We analyze sea-surface and near-seafloor magnetic and bathymetric data as well as photos collected by R/V L'Atalante and ROV Victor (cruise MOMARDREAM, 2008) to propose a model that explains these peculiarities and solves this apparent paradox. The Rainbow Hill has been formed as an oceanic core complex associated with the Amar Minor North (AMN) segment (now located to the North and East of Rainbow), later dismantled by the northward propagation of the Amar Minor South (AMS) segment (located to the South and West of Rainbow) and the coeval recession of the AMN segment. In this model, the break-away remains on the North American plate whereas the main part of the core complex is transferred to the African plate by the propagation of the AMS segment. The corrugations are dismantled by the deformation associated with the northward propagation of the non transform discontinuity between the AMN and AMS segments. This model explains the high-temperature hydrothermal site sitting on an oceanic core complex characteristic of a cold, poorly magmatic spreading environments. The core complex belongs to the cold, receding AMN segment whereas the heat fueling site Rainbow comes from the hot, northward propagating AMS segment. In this model, fossil high-temperature hydrothermal sites should be found on the propagation trace south-east of the present site Rainbow, an inference supported by a strong positive near-seafloor magnetic anomaly still to be explored. The association of an OCC and ridge propagation may be quite common at slow spreading centers and explain many atypical OCC.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGP31B0716D
- Keywords:
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- 1517 Magnetic anomalies: modeling and interpretation;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1519 Magnetic mineralogy and petrology;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1525 Paleomagnetism applied to tectonics: regional;
- global;
- GEOMAGNETISM AND PALEOMAGNETISMDE: 1541 Satellite magnetics: main field;
- crustal field;
- external field;
- GEOMAGNETISM AND PALEOMAGNETISM