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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 4. (April)

First Page: 756

Last Page: 756

Title: Geology of Lakeview Uranium District, Oregon: ABSTRACT

Author(s): S. B. Castor, M. R. Berry

Article Type: Meeting abstract


About 400,000 lb (181.4 Mg) of U3O8 have been mined from Tertiary volcanic rocks near Lakeview, Oregon, mostly from uraninite-coffinite ore bodies at the White King mine. At this deposit, tuffs and tuffaceous sedimentary rocks are overlain by a basaltic lahar which is capped by basalt flows. The tuffaceous rocks are intruded by flow-banded rhyolite. Most of the ore is in the rholite and adjacent tuffaceous rocks, but uraniferous shear zones cut the lahar, and the basalt is highly altered. Most of the uraniferous rock is silicified and brecciated, and has high As, Hg, Mo, and Pb together with secondary U minerals.

Within 10 km of the mine are nine smaller uranium occurrences, four of which are in, or adjacent to, flow-banded rhyolite domes which are considered endogenous. However, five occurrences are distant from surface exposures of rhyolite: three in volcanic sandstone and tuff near contacts with basalt, and two in a thick sequence of rhyolitic to dacitic ash flows.

At the White King mine and most of the other occurrences, uranium was probably deposited from epithermal fluids released during rhyolite intrusion. These fluids could have migrated some distance from the intrusions along fractures or through permeable sedimentary rocks. Capping basalts, which are cut by the intrusions, appear to have arrested the movement of uranium at several occurrences.

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