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Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California

Journal of Geophysical Research

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Abstract

Measurement of the magnetic susceptibility of more than 6000 samples of granitic rock from the Mariposa 1?? by 2?? quadrangle, which crosses the central part of the Sierra Nevada batholith between 37?? and 38??N latitude, shows that magnetic susceptibility values are above 10-2 SI units in the east and central parts of the batholith and drop abruptly to less than 10-3 SI units in the western foothills. In a narrow transitional zone, intermediate values (10-3 to 10-2) prevail. Magnetic susceptibility appears to decrease slightly westward within the zones of both high and low values. Magnetic susceptibility in plutonic rocks is chiefly a function of the abundance of magnetite, which depends, in turn, on the total iron content of the rocks and their oxidation ratio. Correlations of magnetic susceptibility with initial 87Sr/86Sr suggest that oxidation ratios have been inherited from the source regions for the magmas from which the rocks crystallized. Reduction of Fe3+ to Fe2+ by organic carbon or other reducing substances may also have affected magnetic susceptibility. -from Authors

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Magnetic susceptibility and relation to initial 87Sr/86Sr for granitoids of the central Sierra Nevada, California
Series title:
Journal of Geophysical Research
Volume
96
Issue:
B12
Year Published:
1991
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research