Do Layer 3 rocks make a significant contribution to marine magnetic anomalies? In situ magnetization of gabbros at Ocean Drilling Program Hole 735B

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doi: 10.1029/93JB01097
Author(s): Pariso, Janet E.; Johnson, H. Paul
Author Affiliation(s): Primary:
University of Washington, School of Oceanography, Seattle, WA, United States
Volume Title: Journal of Geophysical Research
Source: Journal of Geophysical Research, 98(B9), p.16,033-16,052. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227
Note: In English. Univ. Wash., Sch. Oceanogr., Contrib. No. 1969. 61 refs.; illus. incl. 2 tables, sketch map
Summary: We estimate the average magnetization of a vertical section of oceanic gabbros using paleomagnetic and downhole magnetic logging techniques and evaluate the ability of these crustal rocks to contribute to marine magnetic anomalies. Results from Ocean Drilling Program Hole 735B show that the drilled crustal section has a mean effective remanent magnetization of 2.5 A/m. Olivine gabbros, which make up 60% of the section, have an average effective magnetization between 1 and 2 A/m. We used two-dimensional forward modeling and the average effective magnetization of olivine gabbros to predict the magnitude of a typical layer 3 anomaly observable at sea surface. These results indicate that if polarity boundaries within oceanic layer 3 are near-vertical, crustal sections similar to 735B would contribute from 25% to 75% of the overlying marine magnetic anomalies at the sea surface. The shape of the polarity boundaries in lower crust will be controlled by its thermal evolution and potentially could be constrained by systematic analyses of the amplitude and skewness of marine magnetic anomalies at individual spreading centers. Copyright 1993 by the American Geophysical Union.
Year of Publication: 1993
Research Program: ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Crust; Downhole methods; Gabbros; Igneous rocks; In situ; Indian Ocean; Leg 118; Lower crust; Magnetic anomalies; Magnetic logging; Magnetic properties; Magnetization; Mid-ocean ridges; Natural remanent magnetization; ODP Site 735; Ocean Drilling Program; Oceanic crust; Paleomagnetism; Plate tectonics; Plutonic rocks; Remanent magnetization; Sea-floor spreading; Southwest Indian Ridge; Spreading centers; Thermal history; Two-dimensional models; Well-logging
Coordinates: S324327 S324318 E0571618 E0571557
Record ID: 1993041626
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