Potassic alteration of Cambrian-Ordovician sandstones and Precambrian basement rocks of the North American midcontinent

In Hole UPH-3 the Mt. Simon Sandstone contains three distinct diagenetic zones: an upper K-feldspar overgrowth zone, an underlying sericite zone, and a lowermost feldspar zone. Uppermost Precambrian basement exhibits potassic alteration similar to the overlying Mt. Simon Sandstone. Sericite in the basement rock was likely formed during the same episode as in the Mt. Simon Sandstone, based on similar δ\sp{18}O values. A K/Ar date of 394.6 $\pm$ 6 Ma (Early Devonian) was obtained from authigenic K-feldspar of the basal Mt. Simon Sandstone. K/AR dates of 271.3 $\pm$ 4.6 Ma (Permian), 254.4 $\pm$ 4.6 Ma (Permian), and 214.1 $\pm$ 4.6 Ma (Triassic) were obtained from authigenic sericite of the Mt. Simon Sandstone. Similar potassic diagenesis of Mt. Simon Sandstone in UPH-3 occurs on a regional scale in the Upper Midcontinent area. Here, two widespread zones of K-feldspar and sericite occur. A K/Ar date of 276 $\pm$ 10 Ma (Permian) was obtained on sericite from one locality in Iowa, which is separated by 300 km from Hole UPH-3. The episodic K diagenesis of the Mt. Simon Sandstone is attributed to regional migration of basinal brines caused by groundwater recharge on uplifted arches.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Geology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Duffin, Michael Eugene

Contributors dc:contributor

• Hay, Richard L.

• Geochemistry

Statement dc:rights

• Copyright 1990 Duffin, Michael Eugene

Language dc:language

eng

Identifier

AAI9021675
(UMI)AAI9021675

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/21663