The Azores triple junction evolution since 10 Ma from an aeromagnetic survey of the Mid-Atlantic Ridge

Details The Azores triple junction evolution since 10 Ma from an aeromagnetic survey of the Mid-Atlantic Ridge The Azores triple junction evolution since 10 Ma from an aeromagnetic survey of the Mid-Atlantic Ridge

Jul 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994e%26psl.125..439f&link_type=abstract

Earth and Planetary Science Letters (ISSN 0012-821X), vol. 125, no. 1-4, p. 439-459

Mathematics

Logic

28

Atlantic Ocean, Azores, Geological Faults, Geomagnetism, Geomorphology, Magnetic Anomalies, Mathematical Models, Mid-Ocean Ridges, Paleomagnetism, Plates (Tectonics), Sea Floor Spreading, Tectonics, Geodynamics, Kinematics, Magnetic Surveys, Ocean Bottom

Scientific paper

In the past two decades several models have been presented to describe the evolution and the present structure of the Azores Triple Junction. These models were mainly based on morphological analysis of sea bottom topography, sparse magnetic profiling, sidescan sonar surveying over the plateaus and global plate kinematic considerations for the North Atlantic. In this paper we follow a different approach: from a detailed aeromagnetic survey covering both sides of the Mid-Atlantic Ridge between 37 deg N and 40 deg 30 min N the magnetic anomalies up to anomaly 5 are accurately identified, allowing careful modeling of the kinematics of this region for the past 10 Ma and thus establishing a coherent framework for the design of geophysical models for the Azores Triple Junction. The analysis of magnetic anomalies and the use of Fourier domain inversion techniques show that the ridge is made up of six segments, each one varying in length from 50 to 60 km. The more continuous section of the ridge can be defined from the first four northern segments, although the North Azores Fracture Zone right-offsets the ridge at 39 deg 30 min N, 29 deg 40 min W. The fifth and sixth segments are, respectively, right-offset by the Acor Fracture Zone (at 38 deg 23 min N, 30 deg 15 min W) and by the Princess Alice Fracture Zone (at 38 deg 00 min N, 30 deg 50 min W). Anomaly identifications using a two-dimensional model and plate tectonics reconstruction techniques allowed the calculation of rotation pole parameters. The results thus obtained reveal that, at least between anomalies 5 and 3 (approximately 10-3.85 Ma), the Azores displayed an independent motion relative to the neighboring plates and after anomaly 2A (2.45 Ma) the Azores moved attached to the Eurasian plate. The triple junction (Azores-North America-Africa, or Eurasia-North America-Africa) moved northward from approximately 38 deg 00 min N, 30 deg 50 min W to approximately 38 deg 20 min N, 30 deg 15 min W (between 4 and 3A) and probably to 38 deg 50 min N, 30 deg 00 min W at anomaly 2A time. A detailed reconstruction model is presented.

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