The Pre-Jurassic Surface of Montana.

It has long been known that, prior to the deposition of Jurassic sediments, Montana was subjected to an intensive period of erosion. Mention of this may be found in numerous reports, especially those dealing with western Montana.

Areal Geology of the Post-Paleozoic Surface of the Northwest Plains

Probably most of the area included in this report has been ex­amined to some extent by oil geologists, and most, if not all, of the important domes have been discovered and surveyed thoroughly. In parts of the area, the bedrock is covered by glacial drift or alluvium materi­al, but it is reasonable to believe that no new domal structure will be found. This means that surface examination alone will be insufficient in locating new oil fields, so future prospecting will be dependent, to a great extent, on studies of sub-surface stratigraphy.

Subsurface to Surface Correlation of the Tensleep Sandstone in the West Flank of the Pryor Mountains in Carbon County, Montana

The Pennsylvanian Tensleep Sandstone is an eolian and nearshore marine/sabka quartz arenite unit with prominent outcrops along the western Pryor/Bighorn Mountain front east of Red Lodge, MT. Regionally, the formation represents one of the largest ergs in the global geologic record. High permeability makes it an important oil and gas reservoir and aquifer in south central Montana and throughout much of Wyoming. The Tensleep Sandstone’s high percentage of quartz content and grain roundness, due to its eolian origin, makes it a prospective source for natural proppant sand. Three continuous 4-inch cores were obtained during a cooperative project between Montana Tech and industry partners. Using stratigraphic sections, cores, thin sections, and x-ray fluorescence (XRF) analysis, the usefulness and economic feasibility of the Tensleep Sandstone as a minable hydraulic fracture proppant was explored. Usefulness depends on cementation, grain shape, grain size, and depth from surface of the prospective zone. Grain shape and size were determined by thin sections, sieving, and stereomicroscope analysis. Analysis of 20 disaggregated sand samples has shown that as much as 30 percent of the grain sizes fall between 30-50 mesh (medium- to finegrained sand size) and about 45 percent of the grain sizes fall between 70–140 mesh (very fine-grained sand to coarse silt), grain sizes appropriate for some hydraulic fracture operations. Core descriptions and XRF data display the distribution of lithology and cementation. Core descriptions and XRF data display the distribution of lithology and cementation. Elemental (XRF) analyses help to delineate more pure quartz sands from those with grain fractions reflecting fine-grained clastic and evaporitic inputs. The core and nearby stratigraphic sections are used to quantify the amount of overburden and the 3 amount of resource in the area. Initial results show favorable crush strength and useable grain size and shape.

Voltammetric Investigation of Xanthate Chemisorption on a Chalcopyrite Surface

Cyclic Voltammetry experiments have been conducted on copper, iron, and chalcopyrite (CuFeS2) and compared to mass-balanced EH-pH Diagrams. Potassium ethyl xanthate (KEX) was added to solution and additional voltammetry experiments were performed to determine the surface chemistry reactions of flotation collector in solution with these minerals. The ultimate goal of this research was to investigate the possibility of xanthate chemisorption onto the chalcopyrite mineral surface. Results of the copper mineral testing confirm previous literature studies and corroborate published isotherm data. Results of the iron mineral testing showed changes in surface reactions with the addition of potassium ethyl xanthate to solution, however, these results were not attributed to the chemisorption of xanthate. Results of the chalcopyrite mineral testing indicate that the surface of the mineral oxidizes to chalcocite (Cu2S). In the presence of ethyl xanthate, small currents were observed and attributed to chemisorption of the potassium ethyl xanthate at the chalcocite surface, suggesting that the mineral's hydrophobicity is induced by more than dixanthogen. This phenomenon was found to be pH-dependent under a range of alkaline conditions (i.e., pH 7-12) at narrow potentials (i.e., 0 to -200mV).