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Post-depositional alteration of titanomagnetite in a Miocene sandstone, south Texas (U.S.A.)

Earth and Planetary Science Letters

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Abstract

Petrographic and geochemical studies have yielded information on the time-space relationships of the post-depositional alteration of detrital titanomagnetite (Ti-mt) in fine- to medium-grained sandstone from unoriented core samples (taken below the water table at depths of 30-45 m) of the Miocene Catahoula Sandstone, south Texas. Aqueous sulfide introduced from sour gas reservoirs along a growth fault into part of the Catahoula shortly after deposition resulted in the replacement at the periphery of Ti-mt grains by iron disulfide (FeS2) minerals. Remnants of Ti-mt in cores of the partly sulfidized grains show no evidence of earlier hematitic oxidation. After sulfidization, part of the sandstone body was invaded by oxygenated groundwaters flowing down a shallowly inclined (1??) hydrologic gradient. The boundary between oxidized and reduced facies is clearly defined by the distribution of ferric and ferrous iron minerals, and the concentrations of Mo, U, and Se. In oxidized (light-red) strata that had not been previously subjected to sulfidic-reducing conditions but that are correlative with strata containing FeS2 minerals, Ti-mt has been partly to entirely replaced pseudomorphously by hematite to form martite. The absence of hematitic alteration of Ti-mt in the reduced facies is strong evidence that martite in the oxidized facies formed after deposition. ?? 1982.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Post-depositional alteration of titanomagnetite in a Miocene sandstone, south Texas (U.S.A.)
Series title:
Earth and Planetary Science Letters
Volume
61
Issue:
2
Year Published:
1982
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Earth and Planetary Science Letters
First page:
381
Last page:
391
Number of Pages:
11