HR: 0802h
AN: NS11C-0695    [Abstracts]
TI: Temporal and spectral induced polarization contribution to ore body detection and differenciation.
AU: * Schmutz, m
EM: schmutz@egid.u-bordeaux.fr
AF: University Bordeaux 3, Institute EGID, 1 allée Daguin, Pessac, F-33607, France
AU: Camerlynck, C
EM: camerl@ccr.jussieu.fr
AF: UMR 7619 Sisyphe University Paris 6, 4 place Jussieu, case courrier 105, Paris, 75252, France
AU: Ghorbani, A
EM: Ahmad.Ghorbani@ccr.jussieu.fr
AF: IPGP,University Paris 7, 4 place Jussieu, case courrier 89, paris, 75252, France
AU: Parisot, J
EM: parisot@cerege.fr
AF: UMR 161 IRD CEREGE, BP 80, aix en provence, 13545, France
AB: The aim of this paper is to show complementarity of temporal and spectral induced polarization, applied to ore body detection and differenciation. Study had been lead into well known geological background through borings, geochemical measurements, and also through some electrical resistivity tomographies. Temporal induced polarization (TIP) material and carry out: TIP had been carried out in a quite original way by employed device, and technique. Measurements had been done with SYSCAL PRO (Iris Instrument, Ltd.) transformed into ELREC PRO: this make it possible to differenciate transmitter device (with VIP generator manufactured by IRIS) from receiver one. The main interests are (i) to avoid internal coupling effects and between transmittor/receptor cables on soil, and (ii) to obtain higher electrical power (until 3000 watt) necessary to reach 30-40m depth. Voltage measurement is done through non-polarizable electrodes. Electrical chargeability and resistivity tomographies had been obtained by lateral device displacement. Pole-dipole device had been chosen because it is the best compromise between minimizing coupling effects, getting enough power to reach wanted depth, and necessary lateral resolution. Spectral induced polarization (SIP) material and carry out : SIP FUCHS II device (manufactured by Radic Research) had been used. As the device is not configurated into a multielectrode way, and as one sounding is very time consuming (about 7 hours), only 2 soundings had been done, located on major chargeability anomalies. First results: A a first analysis, a 3 lauer model can be observed: very resistivive level between 0 and 5m depth (up to 1000 ohm.m), more conductive between 5 and 20-25m depth (50 ohm.m), and finally an increasing resistivity. A finer analysis indicates some big conductive zone 50m wide (50 ohm.m) from surface until 30m depth. This could be exlplained by clay or ore body presence. Chargeability analysis indicate us values very high chargeabilities at resistivity anomaly zone (up to 80 mV/V), whereas everywhere else these values are less than 10mV/V. Such chargeability intensity may only be explained by ore body presence. At this stage we could think that there is only one kind of ore body (nevertheless geochemical analysis indicate 2 different types). Two SIP soundings had been done vertically to chargeability anomalies. There is no difference for resistivity values, but phase diagrams are very different (maximum phase is 3 Hz for one sounding and less than 0.1 Hz for the second). Some SIP modelling is now to be done to better characterize ore body nature. As a conclusion, the measurements of electrical resistivity, of chargeabilité and PPS are very complementary (fastness for the chargeability / strong capacity of differenciation for SIP).
DE: 0925 Magnetic and electrical methods (5109)
DE: 0994 Instruments and techniques
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting