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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 56 (1972)

Issue: 3. (March)

First Page: 616

Last Page: 617

Title: Magnetic Susceptibility Studies of Shales from Northern Anthracite Field of Pennsylvania: ABSTRACT

Author(s): M. T. El-Ashry, U. R. Nejib

Article Type: Meeting abstract


Magnetic susceptibility measurements, using the Gouy method, were carried out on 70 pulverized shale samples from the Wyoming-Lackawanna Valley in northeastern Pennsylvania. The samples also were chemically analyzed for the elements Fe, Mn, Cr, Ni, and Co. The study showed that variations in the susceptibility values follow very closely variations in the concentration of the trace elements Cr, Ni, and Co. The susceptibility values varied from 1.682186 × 10-6 to 29.938439 × 10-6 per gram using a magnetic field of 2.25 Kilogauss. These values correspond to concentrations of Cr = 11 to 420, Ni = 30 to 160, and Co = 2 to 7.5 ppm respectively. The magnetic susceptibility was found to be field-dependent particularly in samples with high trace-ele ent concentrations. The susceptibility also was measured using the Faraday method and similar results were obtained.

By both methods the variations in Fe concentration did not correlate with the susceptibility values measured, although Mn showed a minor degree of correlation. The contribution to the susceptibility values by free pyrite present in some samples was very small.

Trace-element concentrations were found to be low in the north and to increase southward. Black shales showed higher concentrations than greenish or grayish shales. Samples containing appreciable amounts of coal gave very low or negative susceptibility. Pure

End_Page 616------------------------------

anthracite coal gave negative values (-1.617697 × 10-6 per gram).

It is suggested that magnetic susceptibility measurements can give a first approximation as to the relative concentrations of trace elements in shales and similar rocks. Attempts are being made to establish magnetic susceptibility measurements as a simple and fast analytic method.

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Copyright 1997 American Association of Petroleum Geologists