Geology, geochemistry, and uranium favorability of Tertiary rocks in south-central Alaska
No abstract available.
Alaska↗
Geology topics
John A. Campbell
Publications and source records attributed to John A. Campbell.
Genesis of the tabular-type vanadium-uranium deposits of the Henry Basin, Utah
Tabular-type vanadium-uranium deposits occur in fluvial sandstones of the Salt Wash Member of the Morrison Formation of Late Jurassic age The mineralized intervals and the weakly mineralized lateral extensions are bounded both above and below by zones rich in dolomite cement. Carbon isotope values of dolomite cements indicate that at least two sources of carbon existed. One source appears to be the same as that which formed the bedded carbonates in the evaporites in the Tidwell Member of the Morrison Formation stratigraphically below the mineralized interval. The second carbon source is typical of terrestrially deposited carbonates generally associated with meteoric water-dominated environments. Oxygen isotope values of these dolomites show the same trend of isotopically light values above the mineralized interval and isotopically heavier values in and below that interval; they indicate that two isotopically distinct fluids were involved in the mineralizing process. Some aspects of the origin of gangue and ore phases are explainable on the basis of processes which occurred solely within the saline fluid, but key aspects of ore genesis involved the interaction of the saline and meteoric waters. It is postulated that the solution interface migrated vertically within the stratigraphic section. -from Authors
Utah↗
Paleomagnetic and petrologic evidence bearing on the age and origin of uranium deposits in the Permian Cutler Formation, Lisbon Valley, Utah
An approximate age for uranium deposits in red beds of the Permian Cutler Formation, Lisbon Valley salt anticline, Utah, was obtained using paleomagnetic techniques. Progressive thermal demagnetization of samples of mineralized sandstone isolates stable magnetization components having high (≳400 °C) unblocking temperatures that define a tilt-corrected mean direction of D = 358.1°, I = 65.5°, α 95 = 3.3°. This direction is close to expected Late Cretaceous to middle Tertiary mean directions at Lisbon Valley. In contrast, thermal cleaning of samples of unmineralized sandstone isolates tilt-corrected southeasterly, shallow mean directions (D = 140.5°, I = −9.5°, α 95 = 8.6°, and D = 155.9°, I = −4.4°, α 95 = 10.9°, for two localities in the Lisbon Valley area). These results are closely similar to results from the Cutler Formation elsewhere on the Colorado Plateau and from other Lower Permian strata in North America. In unmineralized sandstone, the stable remanent magnetization is carried predominantly by martite of postdepositional or detrital origin, whereas in mineralized sandstone, the stable magnetization is carried largely by authigenic specular hematite as uranium- and vanadium-bearing clusters in interstitial areas, and it thus reflects the time of mineralization. Partial dissolution of martite grains and grain-coating ferric oxide pigment prior to formation of abundant interstitial specular hematite has minimized or eliminated the influence of late Paleozoic magnetic components in mineralized sandstone. These results, combined with information on the structural development of the Lisbon Valley area and on nearby uranium deposits in the Triassic Chinle Formation, suggest that the growth of the Lisbon Valley anticline during Late Cretaceous to early or middle Tertiary time promoted oxidative destruction of Chinle orebodies and led to a redistribution of uranium and iron from the Chinle into the Cutler. Acidic solutions generated during destruction of sulfide minerals in Chinle orebodies may account for the simultaneous transport of significant quantities of iron and uranium and for the partial dissolution of martite in the Cutler host beds. Neutralization of these solutions by reaction with host-rock constituents (especially calcite) caused precipitation of amorphous ferric oxide, which incorporated uranium by adsorption and which aged to form specular hematite.
Utah↗
Depositional environments of the uranium-bearing Cutler Formations, Lisbon Valley, Utah
The Cutler Formation in Lisbon Valley, San Juan County, Utah, is composed predominantly of fluvial arkosic sandstones, siltstones, shales, and mudstones that were deposited by meandering streams that flowed across a flood plain and tidal flat close to sea level. Two types of channel deposits are recognized from their sedimentary structures: meandering and distributary. The flood plain was occasionally transgressed by a shallow sea from the west, resulting in the deposition of several thin limestones and marine sandstones. The marine sandstones were deposited as longshore bars. Wind transported sand along the shoreline of the shallow sea, forming a coastal dune field. Marine sandstones and eolian sandstones are more common in the upper Cutler in the southern part of the area, whereas in the central and northern part of the area the formation is predominantly fluvial. Crossbed orientation indicates that Cutler streams flowed S. 67? W. on the the average, whereas marine currents moved sediment S. 36? E. and N. 24? W., and wind transported sand S. 800 E. The uranium in the Cutler is found in the central and northern part of the area, in the upper part of the formation, in small fluvial sandstone bodies that were deposited predominantly in a distributary environment. No uranium is known in the marine or eolian sandstones. Petrographically, the uranium-bearing sandstones are identical to other Cutler fluvial sandstones except that they contain less calcite and more clay and are slightly coarser grained. Ore formation has modified the host sandstones very little.
Open-File Report↗
Preliminary investigation of the elemental variation and diagenesis of a tabular uranium deposit, La Sal Mine, San Juan County, Utah
Ore in the La Sal mine, San Juan County, Utah, occurs as a typical tabular-type uranium deposit of the-Colorado Plateau. Uranium-vanadium occurs in the Salt Wash Member of the Jurassic Morrison Formation. Chemical and petrographic analyses were used to determine elemental variation and diagenetic aspects across the orebody. Vanadium is concentrated in the dark clay matrix, which constitutes visible ore. Uranium content is greater above the vanadium zone. Calcium, carbonate carbon, and lead show greater than fifty-fold increase across the ore zone, whereas copper and organic carbon show only a several-fold increase. Large molybdenum concentrations are present in and above the tabular layer, and large selenium concentrations occur below the uranium zone within the richest vanadium zone. Iron is enriched in the vanadium horizon. Chromium is depleted from above the ore and strongly enriched below. Elements that vary directly with the vanadium content include magnesium, iron, selenium, zirconium, strontium, titanium, lead, boron, yttrium, and scandium. The diagenetic sequence is as follows: (1) formation of secondary quartz overgrowths as cement; (2) infilling and lining of remaining pores with amber opaline material; (3) formation of vanadium-rich clay matrix, which has replaced overgrowths as well as quartz grains; (4) replacement of overgrowths and detrital grains by calcite; (5) infilling of pores with barite and the introduction of pyrite and marcasite.
Open-File Report↗
Uranium potential of Permian rocks in the southwestern United States
Evaluation of the uranium potential of Permian rocks in the southwestern United States, between 96° and 112° longitude and 29° and 41° latitude, is being conducted. This area includes central and western parts of Oklahoma, Kansas, and Texas; all of Colorado and New Mexico; and eastern parts of Utah and Arizona. The purpose of this evaluation is to select areas that have high uranium potential for basin analysis, and to improve our knowledge of the distribution of uranium in Permian rocks. Paleotectonic elements including basins and positive areas, and stratigraphic sequences lying marginal to these elements were analyzed for uranium potential. Basin analysis factors considered were: source of sediment; sediment dispersal; depositional environments; basin geometry; lithology including organic content; sand-shale ratios, and thickness; regional unconformities; and depth of burial at the present time. Associations between uranium occurrences and basin factors were used to test and modify the approach. Target areas with the highest uranium potential were selected for field reconnaissance. High potential target areas include the following in the mid-continent area: central Oklahoma northward from the Arbuckle Mountains; along the north flanks and between the Arbuckle and Wichita Mountains, and south of the Wichita and Arbuckle Mountains in the Hollis Basin and adjacent areas. Potential host rocks in these target areas are in both the Wolfcamp and Leonard Series. Guadalupe Series rocks northwest of the Arbuckle Mountains in western Oklahoma are also a target. In the Southern Rocky Mountain area the following target areas were outlined: the Central Colorado Trough, the Rowe-Mora Basin in northern New Mexico, and the Uncompahgre Trough of eastern Utah and southwestern Colorado and the associated Permian San Juan Basin of northwestern New Mexico. From these targets, four areas (including the Uncompahgre Trough, the Central Colorado Basin, western Oklahoma, and the Hollis Basin and adjacent areas) were selected for detailed stratigraphic and depositional environment study.
Open-File Report↗