Petrographic features of oceanic peridotites as reflected by their magnetic characteristics

B A Bazylev; K V Popov; V P Shcherbakov

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Petrographic features of oceanic peridotites as reflected by their magnetic characteristics

Published в Russian Journal of Earth Sciences · Volume 4, Issue 3, 2002 · Pages 201–223 · Rubrics: ORIGINAL ARTICLES

Received: 25.06.2002 Accepted: 25.06.2002 Published: 25.06.2002

Authors

B A Bazylev ¹ · K V Popov ² · V P Shcherbakov ³

1 Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia

2 Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

3 Borok Geophysical Observatory, Schmidt United Institute of Physics of the Earth, Borok, Russia

ABSTRACT

Petrographic and petromagnetic studies of a representative collection of peridotites from various localities on the Mid-Atlantic Ridge have been carried out. It is shown that secondary magnetization of peridotites comes into being usually prior to the onset of serpentinization, in the course of the preceding medium-temperature metamorphic recrystallization of the rocks. The formative conditions of magnetite in peridotites can be inferred from its integrated grain size, quantified from petromagnetic characteristics. Grain size of magnetite that is formed during serpentinization of oceanic peridotites averages 3-4 mm. Increased mean grain size of magnetite 20 mm or more is suggestive of its having crystallized in the course of medium-temperature metamorphism of peridotites. Based on our own and published data, an increased mean grain size of the magnetic phase is characteristic of most oceanic peridotites, which provides a further proof of extensive development of medium-temperature metamorphic recrystallization of these rocks both within transform faults and on rift valley slopes. The obtained data afford the conclusion that the thickness of the magnetic layer of the MOR lithosphere ranges from 6 to 15km, its lower limit being set by the 580o C isotherm, corresponding to the Curie point for magnetite.

KEYWORDS

petrography oceanic peridotites magnetic characteristics Mid-Atlantic Ridge.

Information Text References

Authors:

1. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia

2. Institute of Oceanology, Russian Academy of Sciences, Moscow, Russia

3. Borok Geophysical Observatory, Schmidt United Institute of Physics of the Earth, Borok, Russia

Type:

Article

Pages:

from 201 to 223

Status:

Published

Language:

English

Keywords:

petrography, oceanic peridotites, magnetic characteristics, Mid-Atlantic Ridge.

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References

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Petrographic features of oceanic peridotites as reflected by their magnetic characteristics

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