142 • Marine Minerals: Exploring Our New Ocean Frontier 



Figure 4-11.— Conceptual Design of the Towed-Cabie-Array Induced Polarization System 



Transmitter electrodes 



10 kg weight 



Receiver electrodes 



Ag-Ag CI 

 electrodes 



Drogue rope 

 / 



Common-mode rejection 

 differential pre-amp 



Induced polarization, used for many years onshore, is currently being adapted for use at sea to search for titanium placers. 



SOURCE: J.C. Wynn and A.E. Grosz, "Application of the Induced Polarization Mettiod to Offshore Placer Resource Exploration," Proceedings, Offshore Technology 

 Conference 86, May 5-8, 1986, Houston, TX (OTC 5199), p. 399. 



When polarizable minerals are located, there is 

 some hope that a related method, spectral induced 

 polarization (which requires a stationary ship), may 

 be able to discriminate between the various sources 

 of the IP effect. It has been demonstrated that cer- 

 tain onshore titanium minerals (e.g. , ilmenite and 

 altered ilmenite) have strong and distinctive IP sig- 

 natures, and that these signatures can be used in 

 the field for estimating volumes and percentages 

 of these minerals. ""^ One factor complicating inter- 

 pretation of the spectral IP signature for ilmenite 

 could be the degree of weathering. More work is 

 required to determine if spectral IP works as well 

 offshore as it does onshore. If so, it may be possi- 

 ble to survey large areas of the EEZ using recon- 



naissance and spectral IP. Sampling then could be 

 guided in a much more efficient manner. ^^ 



The applicability of IP to placers other than tita- 

 nium-bearing sands has not been demonstrated, but 

 USGS researchers also believe that it may be pos- 

 sible, by recalibrating IP equipment, to identify and 

 quantify other mineral sands. Experiments are now 

 being designed to determine if IP methods can be 

 used to identify gold and platinum sands.®* The ap- 

 plicability of IP techniques to marine sulfide de- 

 posits and to manganese-cobalt crusts, too, has yet 

 to be demonstrated. USGS researchers hope to ac- 

 quire samples of both types of deposits to perform 

 the necessary laboratory measurements. 



"J.C. Wynn, A.E. Grosz, and V.M. Foscz, "Induced Polariza- 

 tion Response of Titanium-Bearing Placer Deposits in the Southeastern 

 United States," Open-File Report 85-756 (Washington, DC: U.S. 

 Geological Survey, 1985). 



"Wynn and Grosz, "Applications of the Induced Polarization 

 Method," p. 397. 



"A. Grosz, Eastern Mineral Resources, USGS, telephone conver- 

 sation with W. Westermeyer, OTA, Apr. 8, 1986. 



