Magnetic anomaly patterns on Mid-Atlantic Ridge crest at 26°N

1977 ◽  
Vol 82 (2) ◽  
pp. 231-238 ◽  
Author(s):  
Bonnie A. McGregor ◽  
C. G. A. Harrison ◽  
J. William Lavelle ◽  
Peter A. Rona
1977 ◽  
Vol 14 (4) ◽  
pp. 664-673 ◽  
Author(s):  
D. I. Ross ◽  
R. K. H. Falconer

Geophysical data collected as part of Leg 37 are compiled with more recent data collected for new IPOD drilling site surveys. Bathymetric and magnetic maps covering the area of sites 332–335 are presented. On the basis of magnetic anomaly correlations it is suggested that site 334 is on normal crust between fracture zones A and B and not closer than 15 km to either fracture zone. Magnetic anomaly inversion is applied to a composite profile, extending from the ridge crest out to beyond anomaly 5. It shows a definite change in spreading rate at 4.7 ± 0.5 Ma. Average rates for the periods 0–4.7 Ma and 4.7–10 Ma are 10.2 ± 0.9 mm/yr and 14.0 ± 1.9 mm/yr respectively. The inversion results are consistent with a simple magnetic source layer 2 km thick.


Displacements along strike slip faults in the ocean floor are measured by fitting magnetic anomaly patterns. In the northeastern Pacific Ocean the combined left lateral displacement of 1400 km across the Mendocino and the Pioneer faults can now be followed with a few interruptions from 140 to 165° W, or a distance of 2200 km. The western end of the correlatable pattern has not yet been reached. In latitude the pattern stretches between 28 and 41° N, or a distance of 1450 km. Right lateral displacements of 150 and 680 km separated by a disturbed zone have been measured on the Murray fault between 125 and 152° W. The disturbed zone occurs on the south side of the Murray fault. It is characterized by more rugged topography and is bordered by groups of volcanoes at its eastern and western boundaries. Across the faults the bathymetric contours are displaced in the same direction and roughly by the same amount as the magnetic intensity pattern. Fourteen magnetic profiles across the Mid-Atlantic Ridge between 30 and 6° S show a persistent magnetic anomaly on the crest of the ridge which can be followed from one profile to the next, whereas topographic features lack this continuity. Mapping the position of the crest anomaly suggests that if the ridge was originally continuous, it has now been cut into sections by strike slip faults.


1998 ◽  
Vol 103 (B10) ◽  
pp. 24201-24221 ◽  
Author(s):  
Morgane Ravilly ◽  
Jérôme Dyment ◽  
Pascal Gente ◽  
Rémy Thibaud

Author(s):  
PETER A. RONA ◽  
REGINALD N. HARBISON ◽  
BOBBY G. BASSINGER ◽  
ROBERT B. SCOTT ◽  
ANDREW J. NALWALK

1975 ◽  
Vol 12 (12) ◽  
pp. 1959-1969 ◽  
Author(s):  
Patrick J. C. Ryall ◽  
J. M. Ade-Hall

A detailed study has been made of the magnetic properties of four pillow lavas of differing ages from the Mid-Atlantic Ridge crest at 45°N. The pillows show radial variations in grain size and concentration of titanomagnetite due to the initial cooling history, and radial variation in their degree of titanomagnetite oxidation due to low temperature alteration by sea-water. The degree of titanomagnetite alteration not only increases from the interior to the exterior of the pillows, it also increases from the youngest to the oldest. Radial variation in NRM intensity results in average values for the pillows of as little as half the values for the freshest parts. The direction of the original NRM has been maintained throughout the alteration.


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