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Precambrian Iron Deposits in Missouri

Frank G. Snyder
Frank G. Snyder
603 South Gables Boulevard, Wheaton, Illinois, July 3, 1967
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January 01, 1969


New discoveries made over the past several years indicate that Southeast Missouri is a major iron province. The ten known iron occurrences include three major deposits.

The ore occurs as magnetite, with minor amounts of hematite, in Precambrian rhyolites and andesites. Iron mineralization may be conformable with flow structures of volcanic rocks or may be sharply disconformable. Ore bodies, overlain by up to 2,000 feet of Lower Paleozoic sediments, may be at the Precambrian outcrop or subcrop, or within upper Precambrian. Their presence is indicated by strong sharp magnetic anomalies.

Published age dates of rocks from Missouri range from 1.1 b.y. to 1.5 b.y. At Pea Ridge ore body, the rhyolite host and a post-ore dike cutting the ore body give essentially the same age, within the limits of error, of 1.3 b.y.

Deformation due to magmatic pressures that accompanied or immediately followed igneous activity is believed to be the major factor localizing the deposits. The iron could have been derived by differentiation of granitic magma or from hydrothermal alteration of older basic rocks. Presently available evidence suggests that it was derived from the granitic magma.

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Figures & Tables


Society of Exploration Geophysicists Geophysical Monograph Series

Magmatic Ore Deposits

H. D. B. Wilson
H. D. B. Wilson
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Society of Economic Geologists
ISBN electronic:
Publication date:
January 01, 1969




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