In‐situ complex resistivity measurements over the frequency range [Formula: see text] to [Formula: see text] have been made on 26 North American massive sulfide, graphite, magnetite, pyrrhotite, and porphyry copper deposits. The results reveal significant differences between the spectral responses of massive sulfides and graphite and present encouragement for their differentiation in the field. There are also differences between the spectra of magnetite and nickeliferrous pyrrhotite mineralization, which may prove useful in attempting to distinguish between these two common IP sources in nickel sulfide exploration. Lastly, there are differences in the spectra typically arising from the economic mineralization and the barren pyrite halo in porphyry copper systems. It appears that all these differences arise mainly from mineral texture, since laboratory studies of different specific mineral‐electrolyte interfaces show relatively small variations. All of the in‐situ spectra may be described by one or two simple Cole‐Cole relaxation models. Since the frequency dependence of these models is typically only about 0.25, and the frequency dependence of inductive electromagnetic coupling is near 1.0, it is possible to recognize and to remove automatically the effects of inductive coupling from IP spectra. The spectral response of small deposits or of deeply buried deposits varies from that of the homogeneous earth response, but these variations may be readily determined from the same “dilution factor” [Formula: see text] currently used to calculate apparent IP effects.

which provides assessments of undiscovered oil and gas. He held research positions in mineral exploration with Kennecott Exploration Services, radioactive waste storage with Lawrence Berkeley Laboratory, and petroleum production with Sohio Petroleum Company. His current interests are in the characteristics of tightgas resources and the pressure and temperature regimes of sedimentary basins.

A new "Langmuir" trough is described which allows accurate, symmetric compression and expansion of a spread or adsorbed film of molecules. Compression/expansion of films is equally easy at an air-water (A-W) interface or oil-water (O-W) interface. Several different modes of operation of the trough are described which allow measurement of surface/interfacial pressure (π)-area per molecule (A) isotherms and measurement of dilatational rheology of interfacial films. Equlibrium and dilatational measurements are consistent with those obtained via other techniques. The π-A isotherms of spread films of the proteins, β-lactoglobulin (β-L) and bovine serum albumin (BSA) are considerably more expanded at the O-W interface compared to the A-W interface.

Complex resistivity spectra, in the frequency range 0.001 to 10 hz, have been obtained through computer analysis of waveforms tape recorded at porphyry copper deposits. When care is taken to avoid distortions caused by the geometric effects of electrical inhomogeneities, the spectra of typical porphyry copper mineralization are remarkably uniform in character. The geometric effects of veins, which generally complicate the response of hand samples, can be reduced through in‐situ measurements using electrode separations of a few meters. In the frequency range of interest for inducedpolarization (IP) exploration, the observed spectra are accurately described by [Formula: see text] where K is a constant and b is a positive fraction. The fraction b has a value less than 0.1 and is a complete measure of IP. In the frequency range of interest, Laplace transformation gives the step response to be approximated by [Formula: see text] Typical current waveforms used in IP prospecting can be synthesized by superposition of steps. Using these frequency and time response functions, percent frequency effect, phase, and pulse‐transient parameters are compared as measures of IP. By using a volume distribution function, it is shown that a distribution of lossy capacitors will explain the observed response. Physically, this might correspond to the double‐layer capacitance of metallic particles in mineralized rock.