Search USGS⌕ Search

Geology topics

T. E. Mullens

Publications and source records attributed to T. E. Mullens.

9 recordsLinked to original sources
USGS1973

Gold-bearing arsenian pyrite determined by microprobe analysis, Cortez and Carlin Gold Mines, Nevada

Studies of polished sections and chemical analyses made by electron microprobe show that gold and arsenic in the unoxidized ores from the Cortez and Carlin mines are most abundant in pyrite. Gold, as particles too small to be seen under the microscope, along with arsenic is concentrated in tiny pyrite grains (<0.005 mm) and in thin rims of larger pyrite grains. It is concentrated also in arsenopyrite which is sparsely distributed in the Cortez ore. Traces of gold are contained in sphalerite and chalcopyrite sparsely disseminated in Carlin ore. Mercury and antimony occur also in the pyrite, and antimony is in illite as well. Little if any gold or arsenic is contained in quartz, carbonate, clay, and carbonaceous material. In oxidized ore, the sulfur and carbonaceous material have been removed and gold and arsenic occur in iron oxide pseudomorphs after pyrite. Gold can be seen in the oxidized ore, indicating that it has been mobilized and concentrated. No association was found between gold and the carbonaceous material. During mineralization, calcite was removed from the fractured silty carbonate of the Roberts Mountains Formation, creating micropore space in which pyrite, quartz, and illite were deposited. The average tenor of the pyrite, if all the gold were in the pyrite, would be 0.10 percent at Cortez and 0.14 percent at Carlin. These calculated values are similar to the analytical values. The calculated tenor of the carbonaceous material, however-if such material were considered to be the mineral host of the gold-would be 0.28 percent at Cortez and 1 percent at Carlin. These figures are unreasonable when compared with the analytical data, which show that the carbonaceous material contains no detectable amounts of gold. © 1973 Society of Economic Geologists, Inc.

Nevada↗
USGS1957

Lithofacies of the salt wash member of the Morrison Formation, Colorado plateau

The Salt Wash is the basal member of the Upper Jurassic Morrison Formation in parts of Utah, Colorado, Arizona, and New Mexico. Deposited by streams, it comprises lenticular beds of cross-laminated sandstone irregularly interbedded with mudstone, siltstone, claystone, and horizontally laminated sandstone. The term "lithofacies," as used in this paper, denotes lithologic aspect. The specific lithofacies of the Salt Wash member at a given locality is determined by the thickness, proportion, and continuity of the stream and flood-plain deposits that make up the Salt Wash. Stream deposits include all rocks interpreted as deposited from moving water; flood-plain deposits include all rocks interpreted as deposited from slack water. Regional differences in lithofacies show that the Salt Wash member is a fan-shaped wedge of sedimentary rocks whose apex is in south-central Utah. Within the wedge, the thickness of the Salt Wash and the thickness, proportion, and continuity of the contained stream deposits decrease relatively uniformly to the north, northeast, and southeast of the apex. Interpretation of the regional differences in lithofacies indicates deposition by a distributary stream system whose apex was in south-central Utah and which spread sediments to the north, east, and southeast over a nearly flat plain. Irregularities on this plain near the Four Corners area and in west-central Colorado modified the distributary system, and therefore the wedge is not symmetrical. Most uranium-vanadium ore deposits in the Salt Wash member occur in a lithofacies near the center of the wedge. This may be a genetic relation and can be explained as a function of transmissibility of the particular lithofacies. The ore deposits, however, are concentrated in a relatively small part of the central lithofacies. Because local geologic features such as structure or igneous intrusions might control the localization of ore deposits in the small area, the high degree of correlation of ore deposits and a certain lithofacies may be coincidental. © 1957, The Geological Society of America, Inc.

Colorado↗
USGS1954

Distribution of the Hoskinnini tongue of the Cutler formation in southwestern Utah and adjoining parts of Arizona and Colorado

Recent field work indicates the Hoskinnini tongue of the Cutler formation is present in much of southeastern Utah and adjoining parts of Colorado. Previously the Hoskinnini had been recognized only in the Monument Valley region of southeastern Utah and northeastern Arizona. The Hoskinnini tongue is pale reddish brown and is composed mainly of silt and very fine-grained sand and minor quantities of fine, medium, and coarse sand grains. The Hoskinnini is indistinctly bedded in horizontal beds generally ranging from 1 to 2 feet thick, and individual beds are composed of indistinct discontinuous wavy laminae bounded by grayish-red clay or silt films. The Hoskinnini is generally 50 to 120 feet thick but ranges up to 126 feet thick' Pinchouts of the Hoskinnini on the west are abrupt, and the Hoskinnini near some of these pinchouts contains unusual features such as intraformational and chert pebble conglomerates, contorted stratification, and petroliferous material. The combination of coarse grains in the finer-grained matrix and discontinuous wavy laminae serve to differentiate the Hoskinnini tongue from the underlying and overlying formations' The distinctive combination of grain size and wavy laminae also assures correlation of the Hoskinnini with rocks not previously correlated with the Hoskinnini in southeastern Utah and adjoining parts of Colorado. Although the Hoskinnini tongue is cUJITently classified as a part of the Permian Cutler formation, stratigraphic relations show the Hoskinnini to be conttasted with typical Cutler rocks and to be closely related to the Lower and Middle (?) Triassic Moenkopi formation.

Trace Elements Memorandum↗