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Geology topics

Frank E. Senftle

Publications and source records attributed to Frank E. Senftle.

6 recordsLinked to original sources
USGS1980

Field studies of borehole gamma-ray spectrometer methods for mineral exploration; a selected bibliography

A finite-difference digital model was developed to simulate the effects of a proposed well field on the water levels in existing wells in the Salt River Indian Reservation, which is in the southeastern part of Paradise Valley in central Arizona. The model area includes about 600 square miles in Paradise Valley and the adjoining Salt River Valley. In 1975 about 37,500 acre-feet of ground water was withdrawn for irrigation in the Salt River Indian Reservation. The proposed well field would withdraw as much as 45,000 acre-feet per year of additional irrigation water north of the Arizona Canal. The model was calibrated by using measured water-level declines for 1923-76 and simulated declines for 1946-75. The calibrated model was then used to predict water-level declines, based on projected amounts of pumpage, after 20 years of pumping. The rate of water-level decline would be an additional 2 to 6 feet per year in existing wells after 20 years of pumping in the proposed well field. The model was more sensitive to changes in pumpage distribution and in pumpage and recharge amounts than to changes in transmissivity and specific yield. (USGS)

Open-File Report↗
USGS1978

A table of photopeaks useful in nuclear geophysics

The table lists full-energy, single-escape, and double-escape photopeak energies corresponding to about 1800 x- and gamma rays derived from natural radioactivity, X-ray fluorescence, neutron reactions, and induced radioactivity. Photon lines have been selected on the basis of their importance in borehole logging by nuclear methods. The mode of production of each photopeak and the half lives of natural and artificial radionuclides are given, but intensity information is omitted.

Open-File Report↗
USGS1975

The Néel transition and magnetic properties of terrestrial, synthetic, and lunar ilmenites

The magnetic susceptibility of a terrestrial, synthetic and lunar ilmenite specimen has been measured from 4 to 300 K. All specimens had a single Néel temperature transition which ranged from 56 to 57.7 K. In one case the powdered specimen was partially aligned in the magnetic field prior to the susceptibility measurements and the Néel transition was observed to shift to 60 K indicating magnetic anisotropy. A study of several magnetic parameters calculated from the experimental data showed gross impurities in the terrestrial specimen, single-domain to multi-domain metallic iron in the synthetic specimen, and a small amount of superparamagnetic metallic iron in the lunar sample. No multidomain iron was observed in the lunar ilmenite. The results of electron spin resonance measurements were also in general agreement with these findings. Because of the absence of Fe 3+ compared to most terrestrial samples it is suggested that the anisotropic magnetic parameters be determined on lunar ilmenite when a large enough single crystal becomes available.

Earth and Planetary Science Letters↗
USGS1971

Magnetic susceptibility and triangular exchange coupling in the tourmaline mineral group

Magnetic susceptibilities of three iron-rich tourmaline crystals from Mexquitic (Mexico), Pierpont (New York), and Madagascar with different and known chemical compositions have been studied from 8° to 300°K. The iron atoms in the tourmaline crystal structure, space group R3m , a∼15·9, c∼7·2 , are situated at the three corners of an equilateral triangle and are close enough for magnetic exchange interaction. For buergerite, the Mexquitic sample, the susceptibility data lead to an exchange constant J/k of 7·5°K. Although the amount of aluminum would be sufficient to fill point position 18(c) exactly, the magnetic data are consistent with some substitution of ferric iron for aluminum, as previously determined from X-ray and neutron diffraction studies. Some aluminum thus replaces iron in position 9(b). Exchange constants were also estimated for the other two magnesium-iron specimens, of which the madagascar sample is aluminum deficient. The results agree with the evidence from optical spectra that there is considerable deviation from octahedral symmetry in the oxygen coordination polyhedra about the 9(b) and 18(c) point positions.

New York↗