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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.

Electron spin resonance and distribution of some elements in shales

Akio Inazumi, Toshiyuki Isobe, Toshikazu Tarutani
Geochemical Journal, Vol. 15, No. , P. 325-332, 1981


Five types of ESR signals were observed in shales. The resonance composed of six lines near geff = 2 (type A) is attributed to Mn(II). Type A resonance is divided into two groups on the basis of its line shape; one exhibits six sharp lines (type A-1), and another shows relatively broad lines (type A-2). The geff = 2 broad resonance (type B) may be attributed to Fe(III). The geff sharp resonance line (type C) probably results from stable organic free radicals. The geff = 4.1 resonance (type D) can be attributed to high spin Fe(III) occupying sites of orthorhombic symmetry in clay minerals. Some of the shales show an inclined signal covering a wide magnetic field (type E). Combination of ESR measurements and leaching experiments made it possible to survey the distribution and states of some elements in shales. In shales which exhibit type A-1 resonance overlapped with type A-2 resonance, Mn(II) is randomly distributed both in calcite and clay minerals. In shales which exhibit only type A-2 resonance, Mn(II) is associated mainly with clay minerals. Most of the iron in shales is bound to clay minerals. A part of the iron in clay minerals is present as Fe(III) which shows type D resonance.

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