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Geology of the Egnar quadrangle, Dolores and San Miguel counties, Colorado

Trace Elements Memorandum 695

This report concerns work done partly on behalf of the Division of Raw Materials of the U.S. Atomic Energy Commission
By:
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Abstract

The Egnar quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by hih-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as "Uruvan Mineral Belt". Individual deposits range in size from irregular masses containing only a few tons of ore to large, tabular masses containing many thousands of tons. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

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Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Geology of the Egnar quadrangle, Dolores and San Miguel counties, Colorado
Series title:
Trace Elements Memorandum
Series number:
695
Year Published:
1954
Language:
English
Publisher:
U.S. Geological Survey
Description:
Report: 25 p.; 1 Plate: 34.63 x 28.48 inches
Country:
United States
State:
Colorado
County:
Dolores County;San Miguel County
Other Geospatial:
Egnar Quadrangle
Additional Online Files(Y/N):
Y