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Neil S. Fishman

Publications and source records attributed to Neil S. Fishman.

23 records · Page 2Linked to original sources
USGS1986

Origin of the Mariano Lake uranium deposit, McKinley County, New Mexico

The Mariano Lake uranium deposit, hosted by the Brushy Basin Member of the Jurassic Morrison Formation, occurs in the Smith Lake district of the Grants uranium region, New Mexico. The orebody, contains abundant amorphous organic material, which suggests that it represents a primary-type deposit; however, the orebody is close to a regional reduction-oxidation interface, which suggests that uranium was secondarily redistributed by oxidative processes. Uranium contents correlate positively with organic carbon contents. Petrographic evidence points to uranium residence in amorphous organic material that was post- depositionally introduced in the diagenetic history of the host sandstone. Uranium mineralization was preceded by precipitation of pyrite (δ 34 S values of — 11.0 to — 38.2 per mil), mixed-layer smectite-illite clays, and quartz and potassium feldspar overgrowths; and also partial dissolution of some detrital feldspars. Alterations associated with uranium mineralization include precipitation of the organic material, microcrys- talline quartz, and pyrite and marcasite (δ 34 S values of -29.4 to -41.6 per mil), and the destruction of detrital Fe-Ti oxide grains. Following mineralization, calcite, dolomite, barite, and kaolinite were precipitated, and some iron disulfides were replaced by ferric oxides. Geochemical data and petrographic observations both indicate that the Mariano Lake orebody is a primary-type deposit. Oxidative processes have not noticeably redistributed uranium in the immediate vicinity of the deposit, nor have they greatly modified geochemical characteristics in the ore. Impedance of ground-water flow by local folds and the lower porosity characteristics of ore zones may have helped to preserve the deposit.

New Mexico↗
USGS1986

Iron-titanium oxide minerals and magnetic susceptibility anomalies in the Mariano Lake-Lake Valley cores-Constraints on conditions of uranium mineralization in the Morrison Formation, San Juan Basin, New Mexico

Petrographic study of the Mariano Lake-Lake Valley cores reveals three distinct zones of postdepositional alteration of detrital Fe-Ti (iron-titanium) oxide minerals in the Westwater Canyon Member of the Upper Jurassic Morrison Formation. In the uranium-bearing and adjacent portions of the Westwater Canyon, these detrital Fe-Ti oxide minerals have been thoroughly altered by leaching of iron. Stratigraphically lower parts of the Westwater Canyon and the underlying Recapture Member are characterized by preservation of Fe-Ti oxide grains, primarily magnetite and ilmenite, and of hematite, and by an absence of uranium concentrations. Partly destroyed Fe-Ti oxide minerals occupy an interval between the zones of destruction and preservation. Alteration patterns of the Fe-Ti oxide minerals are reflected in bore-hole magnetic susceptibility logs. Magnetic susceptibility response in the upper parts of the Westwater Canyon Member is flat and uniformly < 500 /xSI units, but at greater depths it fluctuates sharply, from <1,000 to nearly 8,000 μSI units. The boundary between uniformly low and high magnetic susceptibility response corresponds closely to the interval that divides the zone of completely altered from the zone of preserved detrital Fe-Ti oxide minerals. The alteration pattern suggests that solutions responsible for destruction of the Fe-Ti oxide minerals originated in the overlying Brushy Basin Member of the Morrison Formation. Previous studies indicate that these solutions were rich in soluble organic matter and perhaps in uranium. Uranium precipitation may have been controlled by a vertically fluctuating interface between organic-rich solutions and geochemically different fluids in which the detrital Fe-Ti oxide minerals were preserved.

New Mexico↗
USGS1985

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↗
USGS1983

Geochemical characteristics of the Church Rock 1 and 1 East uranium deposits, Grants uranium region, New Mexico

In the Church Rock 1 and 1 East mines, Grants uranium region (GUR), New Mexico, uranium orebodies occur within three sandstone units in the upper part of the Westwater Canyon Member of the late Jurassic Morrison Formation. Geochemical analyses reveal that organic carbon contents in ore samples from all three sand units are uniformly low (most are less than 0.01 percent). Vanadium (ranging from 0.0002 to 0.19 percent) and sulfur (ranging from <0.01 to 0.74 percent) typically show positive correlations with uranium; however, vanadium contents rarely exceed those of uranium in ore samples. Although no systematic relationship of either selenium or molybdenum to uranium is evident, some ore samples contain anomalously high concentrations of either of these elements. Geochemically, the ore deposits of the Church Rock area contrast greatly with primary (tabular) uranium orebodies in the GUR which contain abundant organic carbon and greater amounts of vanadium and sulfur. These differences and radiometric age determinations strongly suggest that the Church Rock ores formed as a result of the redistribution of uranium from preexisting uranium deposits within the last 1 m.y. However, the Church Rock deposits differ geochemically from redistributed orebodies in the Westwater Canyon Member elsewhere in the GUR. Specifically, redistributed orebodies in the Ambrosia Lake district, which are comparable in contents of uranium and organic carbon with the Church Rock deposits, are characterized by vanadium contents typically higher than those of uranium. Similarly, sulfur contents in the redistributed deposits of the Ambrosia Lake district are greater than those found in the Church Rock ores. In addition, anomalously high concentrations of molybdenum have rarely been found in other redistributed orebodies of the GUR.

Open-File Report↗