"INDUCED POLARIZATION DATA AT ... - University of Utah

ABSTRACT
CHU
Both field and laboratory broadband multispectral data have been
gathered in a study of IP phenomena at the Roosevelt Hot Springs
geothermal area. The field survey involved two traverses across the
main part of the present day hydrothermal system. The laboratory
research gathered data at 25°C, 50°C, and 75°C, on hydrothermally
altered rocks from the hot springs area.
Laboratory data indicate a small IP effect of 3 to 23 mr at low
frequencies (0.004 Hz). High frequency (10 3 Hz) IP data ranged from 20
to 100 mr. The IP effect is frequency dependent, and is not affected
markedly by moderate changes in temperature; it is also dependent upon
the quantities of pyrite and clay minerals. Pyrite affects the phase
spectrum well above 1 Hz, and its effect is different from that of
polarizable clays.
The field data at the higher frequencies show both positive and
negative phase values, which can be explained by electromagnetic
coupling. Extrapolated phase data reveal a small anomalous region of 20
to 34 mr along one of the profiles; the majority of the data ranged from
7 to 15 mr.
The laboratory and field data indicate only a small IP effect over
the hydrothermal system; it could be considered as background and hence
of no consequence. There seems to be no large scale delineation of the
geothermal field.