2/21/2013 2:20:00 PM Aerial survey concerned with
valuable minerals, not frac sand
By Sarah Strandberg
Strange, low-flying helicopters carrying net-like antennas; news that Decorah is sitting on a buried meteorite impact crater; and meetings on frac-sand mining have many locals wondering what it all means.
Starting in December, the United States Geological Survey (USGS) began a series of aerial surveys of portions of Winneshiek County to collect information on a series of rocks that lie buried about 2,000 feet deep.
The USGS is a science organization that provides impartial information on the health of the country's ecosystems and environment, and the natural resources the country relies on, among other things, according to the organization's website.
"As part of Iowa's 'basement complex,' these rocks are a suite of iron- and magnesium-rich igneous rocks that were intruded into older rocks in that area about 1 billion years ago ... it is suspected that these intrusive rocks could host significant deposits of strategic metallic minerals, such as nickel, well as gold and silver," Ray Anderson of the Iowa Geological and Water Survey wrote in an article in December.
In December and January, a fixed-wing airplane with a gravity gradiometer flew over Winneshiek County and part of Southeastern Minnesota, and this month, a helicopter carrying large electromagnetic and magnetic instruments from a cable underneath, has been observed locally.
"These instruments will provide much more detailed information on the rocks that are interacting with the Earth's gravity and magnetic fields than is currently available," Anderson said.
"With these measurements, scientists will be able to create a more accurate model of the distribution and character of these intrusive rocks, perhaps leading to exploration drilling to accurately access their mineral value."
Not connected, but a benefit
The survey is not connected to recently reported research on the likelihood Decorah is sitting on a meteorite impact crater, although crater sites, such as the Sudbury Impact Structure in Canada, is rich in minerals, according to Robert McKay, an Iowa Department of Natural Resources geologist.
"Some impact craters are also associated with oil and gas deposits like the Ames Impact Structure in Oklahoma," he added.
"We do not know of any relationship (with minerals or other resources) so far at Decorah. The airborne geophysical survey over Winneshiek County was done because other work analyzing the cores (drilled) to the north and south and old gravity and magnetic data suggested a similarity to the Duluth area geology," McKay told Decorah Newspapers Tuesday, referring to "drill holes" in Clayton County and Houston County in Minnesota.
Exploration of the Duluth Complex, along the north shore of Lake Superior in eastern Minnesota, has discovered a valuable concentration of nickel, copper, titanium and vanadium, as well as gold and silver. Mining should begin there within the next decade, Anderson said.
McKay did acknowledge the USGS survey would provide "very interesting new data that can be analyzed for the (meteorite) crater."
"This is a bonus ... it's going to provide very good information to analyze the size and structure of this crater."
As far as frac sand and the recent USGS surveying of the area, McKay said the two are "not in any way related."
"The distribution of frac sand units is already well known and already well mapped. There would be no reason to conduct sophisticated geophysical survey to learn more about frac sand. The survey is to learn about deep basement rocks, 2,000 feet below the land's surface and more," he said.
Frac sand already has been identified in Winneshiek and Allamakee counties. It's in demand for its use in extracting petroleum, natural gases or other substances from rock formations.
A public meeting on frac sand mining was held last night (Wednesday) in Decorah. Ric Zarwell, president of the Allamakee County Protectors, updated attendees on the frac sand mining discussion in Allamakee County. The Allamakee County Board of Supervisors recently passed an 18-month frac-sand-mining moratorium.
The data compiled in the USGS survey will be released to the public in a report that will be "open to anybody," McKay said.
He said assisting in the discovery of strategic and critical minerals for the U.S is one of the mandates for the USGS.
McKay said it would be more than a decade before any mining would begin should the desired minerals be identified here.
"The demand for minerals goes up and down with the world and U.S. economies. In general, the demand for minerals is (now) relatively high worldwide. The developing countries like China are consuming a lot of minerals," McKay said.
"Hybrid cars have a lot more copper than a normal car because they have a lot of batteries," he added. "Copper prices have been elevated in the past decade."
The USGS is planning other surveys to the east, west and possibly north of current survey area, next year, McKay said.