Several years of accumulat,ing complex resistivity spectral measurements have indicated that. there are &ill many unexplored areas in induced polarization surveying that need to be investigated for a more complete understanding of t,he polarization process. In a,ddition to providing mineral discrimination capabilities, complex resistivity spectra can be used to differentiate between various barren host, rock responses, to facilitat,e the complete removal of elect,romagnetic coupling, and to identify pipeline, fence, and various other cultural coupling effects.Results of field measurements are presented in an effort t,o demonstrate the utility of and necessity for making complete spectral measurements for serious geophysical interpretation. Correlation of field measurements with laboratory measurements on rare samples from the same area. demonstrates that, strong electromagnetic coupling can be acciu-ately removed from complete spectra without removing t,he important rock response.Recent field and laboratory measurement' s indicat,c that most, if not all, intluced polarization responses att,ribut,rd to magnetite arc not really due to this mineral but can he traced to a host rock alteration response. Also, characteristic host, rock signatures for sulfide environments appear to vary according to loc*alit,y and t.ype of deposits making it impossible to provide a universal set, of signatures for sulfide deposits.

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increases toward the causative skarn-forming pluton with the distal pyroxene zones containing more iron-and manganese-rich pyroxenes than proximal zones (Meinert and others, 2005). In some districts (for example, Christmas, Arizona, and Battle Mountain, Nevada), more copper is recovered from calc-silicate rocks than from the associated intrusive rocks. Polymetallic replacement deposits occur in carbonate-bearing units peripheral to porphyry-style mineralization. At Bingham, Utah (Babcock and others, 1995), and Bisbee, Arizona (Bryant and Metz, 1966), polymetallic replacement deposits surround the intrusive complexes with offshoots appearing to radiate outward from the stocks. Vein deposits occur peripheral to many porphyry copper deposits (for example, Bingham, Utah), as well as crosscutting porphyry-style mineralization (for example, Valea Morii, Romania). Primary Commodities Copper is the primary commodity of economic interest in most porphyry copper deposits, although some deposits with low to very low copper grades are mined principally for their gold (for example, Çopler, Turkey) and(or) molybdenum (for example,

Geophysical methods have been used with increasing frequency in archaeology since 1946; aerial photography has been used since 1919. The geophysical methods that are most commonly used at present are electrical resistivity, magnetics, and ground‐probing radar. Magnetic detectors, particularly when used in a gradient mode or with a continuously recording base station, are used at almost all sites where any geophysical methods are used. Portable, noncontacting electromagnetic soil‐conductivity systems are also being increasingly used because of their very high rate of data acquisition. Less commonly used methods include self‐potential (sometimes called spontaneous potential), microgravity, radiometric, thermal infrared imagery, and sonic or seismic techniques. Recent developments in image processing and graphic representation have contributed substantially to the archaeologist's ability to do “rescue archaeology,” that is, to carry out high‐speed, nondestructive reconnaissance surveys for ancient human cultural evidence in advance of modern industrial development.

The induced polarization method of geophysical prospecting has been in use for more than 25 years with varying degrees of success. Until recently, its two principle drawbacks were (1) the inability to distinguish between anomalous rock responses and, (2) inability to distinguish between these rock responses and inductive coupling. The first problem was solved bg K. L. Zonge in 1972.Solutions to the coupling problem go back to 1932, and have been expanded and elaborated upon by successive authors since then. In most of these papers, electromagnet,ic coupling was separated into two functions, here designated as P, a purely inductive term, and Q, a grounding or purely rcsist,ive t,erm. This paper extends this work into a study of the reflective coupling con-tribution and the effects of anisotropy. Two immediate results are: (a) the development of an ultra-low-frequency deep sountling technique for highly conductive overburden cwvironments, and (b) a successful iterative technique for the removal of coupling from complex resistivity field data.A study was made of the effect of electrically conductive pipelines on induced polarization and complex resistivity data. It appears that the so-called "pipeline effect" is a composite of several effects, including current focusing nonlinenritier, elcctromngneticL induction, and complex electrode polarization. The pipeline effect) is generally predictnbh, while the effect of a fence or an irregular cc~nductiw inhomogcncity is not as simple.