Jeff Wynn

Evaluating groundwater in arid lands using airborne magnetic/EM methods: An example in the southwestern U.S. and northern Mexico

In the southwestern United States, where water extraction is beginning to exceed the limited groundwater recharge, assessing regional aquifers is becoming increasingly important. Ideally, one would like to assess these aquifers over time to determine anthropogenic changes. In general, potable groundwater in the southwestern United States is more conductive than in the eastern or northwestern part of the country due to greater ion content. The latest generation of powerful airborne electromagnetic (AEM) systems can directly image groundwater if it contains some dissolved solids and if it is under conditions of little or no human cultural interference.

Where is the Hot Rock and Where is the Ground Water – Using CSAMT to Map Beneath and Around Mount St. Helens

We have observed several new features in recent controlled-source audio-frequency magnetotelluric (CSAMT) soundings on and around Mount St. Helens, Washington State, USA. We have identified the approximate location of a strong electrical conductor at the edges of and beneath the 2004–08 dome. We interpret this conductor to be hot brine at the hotintrusive-cold-rock interface. This contact can be found within 50 meters of the receiver station on Spine 5, which extruded between April and July of 2005. We have also mapped separate regional and glacier-dome aquifers, which lie one atop the other, out to considerable distances from the volcano.

Detection and quantification of hydrocarbons in sediments

A new technology developed by the US Geological Survey now allows for fast, direct detection of hydrocarbon plumes both in rivers and drifting in the deep ocean. Recent experiments show that the method can also detect and quantify hydrocarbons buried in river sediments and estuaries. This approach uses a variant of induced polarization, a surface-sensitive physical property of certain polarizable materials immersed in an electrolyte that can accept and adsorb charge under an inducing voltage. Known polarizable materials include most sulfides, ilmenite (FeTiO3), metallic objects such as buried wrecks and pipelines, and now hydrocarbons. The hydrocarbon-in-water response to induced polarization is in fact nearly two orders of magnitude greater than the IP response of any of the hard minerals. The oil:water detection limit for hydrocarbons so far is down to 0.0002% in the laboratory.

An open-water electrical geophysical tool for mapping sub-seafloor heavy placer minerals in 3D and migrating hydrocarbon plumes in 4D

A towed-streamer technology has been developed for mapping placer heavy minerals and dispersed hydrocarbon plumes in the open ocean. The approach uses induced polarization (IP), an electrical measurement that encompasses several different surface-reactive capacitive and electrochemical phenomena, and thus is ideally suited for mapping dispersed or disseminated targets. The application is operated at sea by towing active electrical geophysical streamers behind a ship; a wide area can be covered in three dimensions by folding tow-paths over each other in lawn-mower fashion. This technology has already been proven in laboratory and ocean settings to detect IP-reactive titanium- and rare-earth (REE) minerals such as ilmenite and monazite. By extension, minerals that weather and accumulate/concentrate by a similar mechanism, including gold, platinum, and diamonds, may be rapidly detected and mapped indirectly— even when dispersed and covered with thick, inert sediment. IP is also highly reactive to metal structures such as pipelines and cables.

A high-resolution electrical geophysical approach to mapping marine sediments in the Atlantic coastal shelf and the Gulf of Mexico.

Studies suggest that the EEZ contains substantial mineral resources, including industrial minerals like ilmenite (a source of titanium) and monazite (a source of thorium and rare earth elements). Gold and platinum are associated with these minerals in some places (Wynn and others, 1990). Ilmenite distribution off the East Coast of the United States is shown in figure 1. Information on ilmenite distribution in the Gulf of Mexico is incomplete and not

Sequestered oil pollution mapping, and tracking active oil breakouts in sensitive rivers, bays, and estuaries

ABSTRACT Oil on the water surface represents just the American Petroleum Institute API > 10 gravity component of any crude oil spill or well blowout, and is identified and tracked by conventional r...

IMAGING WATER AND HOT ROCK BENEATH A VOLCANO USING CONTROLLED-SOURCE AUDIO-FREQUENCY MAGNETOTELLURICS

We have observed several new features in recent Controlled-Source Audio-Frequency Magnetotelluric (CSAMT) soundings on and around Mount St. Helens. We have identified the approximate location of a strong conductor at the edges of and beneath the 2004–08 dome. We interpret this conductor to be hot brine at the hot-intrusive-cold-rock interface, and it can be found within 50 meters of the surface on Spine 5. We have also mapped separate regional and glacier-dome aquifers.