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Anderson |
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Arizona, USA |
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U
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
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The Anderson uranium mine is located in west-central Arizona, USA, approximately 70 km NW of Wickenburg in Yavapai County.
Uranium mineralisation occurs within the Miocene Chapin Wash Formation of the Date Creek basin. The host sequence is composed of a succession of interbedded lacustrine and alluvial sediments which are underlain by a thick complex of probable Oligocene age andesitic to dacitic volcanic rocks. The host sequence is in turn overlain by late Miocene basalt and Pliocene-Pleistocene fanglomerates.
The mineralisation is confined to the 150 m thick lacustrine facies of the host, comprising tuffaceous mudstone, fine grained sandstone and silicified marls, with two basal carbonaceous horizons with thicknesses of 37 and 35 m respectively. These carbonaceous beds are characterised by coalified plant material and dispersed pyrite and contain an extensive, generally conformable 100 to 200 ppm U zone of mineralisation with high grade 0.1 to 0.3% U3O8 masses, mainly in the upper of the two horizons. The two carbonaceous beds are separated by a thick un-mineralised conglomeratic sandstone unit.
The lacustrine sediments of the Chapin Wash Formation contain considerable amounts of rhyolitic ash which has been altered to lithium rich smectite clay minerals, mainly heulandite-clinoptilolite zeolites which was penecontemporaneously silicified and calcified.
Uranium mineralisation is locally associated with high Mo, As and V levels. The higher grade U accumulations are confined to individual seams of lignitic coal and forms halos around rootlet remains, with spotlike concentrations associated with pyrite framboids. The principal ore minerals are uranyl-bearing opaline silica and colloform coffinite.
The mineralised section represents the distal facies of a large alluvial fan-braided river accumulation to the west of the mine area where it inter-tongues with the lacustrine succession, while to the south, an east-west elongated complex of sandy deltaic sediments limit the mineralised facies which are confined to an area of 5 sq. km.
Ore shipped from the Anderson mine open pit between 1955 and 1959 totalled 15 tonnes of U3O8 at a grade of 0.15% U3O8 from a resource of 15 500 tonnes of U3O8 at a cut-off of 0.05% U3O8. Alternatively a resource of 50 000 tonnes of U3O8 at a cut-off of 0.01% U3O8 is quoted by (Otton, et al., 1990).
The lacustrine rocks of the Chapin Wash Formation encompassing the Anderson mine area are estimated to a contain an intermediate- to, locally, high-grade uranium uranium resources of 680 000 tonnes of U3O8 at an average grade of 0.023% U3O8 (Otton, et al., 1990).
For detail see the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1983.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Mueller A, Halbach P 1983 - The Anderson Mine (Arizona) - an early diagenetic Uranium deposit in Miocene Lake sediments: in Econ. Geol. v78 pp 275-292
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Otton J K, Bradbury J P, Forester R M and Hanley J H, 1990 - Paleontological analysis of a lacustrine carbonaceous uranium deposit at the Anderson mine, Date Creek basin, west-central Arizona (U.S.A.): in Ore Geology Reviews v5 pp 541-552
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