Dr. Ray Anderson, newly retired from the Iowa Geological Survey, will present information to the Winneshiek Board of Supervisors on the potential for metallic mineral mining in Northeast Iowa next week.
The public is invited to the presentation, which begins at noon in the large courtroom at the Courthouse Monday, Aug. 25.
Last year, the U.S. Geological Survey (USGS), working with the geological surveys of Iowa and Minnesota, initiated a program to study the “basement complex” -- rocks below sedimentary rocks or sedimentary basins -- of Northeast Iowa and adjacent Minnesota. Researchers were hoping the area could be an “exploration target” for possible platinum group elements (PGE) and related mineralization -- materials of strategic importance to the United States, according to Anderson.
These basement rocks -- about 2,000 feet below the land surface -- are known as the Northeast Iowa Plutonic Complex (NEIPC) and are currently interpreted as a series of iron-rich intrusive rocks associated with the formation of the Midcontinent Rift System.
The study was initiated due to the similarities between interpretations of the geology of the NEIPC and the Duluth Complex in Northeastern Minnesota. Recent industry exploration of the Duluth Complex has led to the discovery of extremely valuable PGE resources in those rocks, leading to the suggestion of similar mineralization in the Iowa rocks, Anderson said.

Aerial data
The initial phase of the Iowa exploration involved analysis of limited drill data, including an exploration core drilled by New Jersey Zinc in 1961 near Osborne in Clayton County and obtaining high resolution aerial gravity gradiometer, aeromagnetic, and aerial electro-magnetic data late 2012 and early 2013 using low altitude helicopter and fixed-wing aircraft platforms over part of Winneshiek County and adjacent areas of Fillmore and Houston counties in Minnesota.
Future plans include the deepening of a water well north of Decorah to obtain additional core samples of the target rocks and the expansion of aerial gravity and magnetic information in the area around the 2012 Winneshiek County survey, Anderson said.
“At Monday’s Board of Supervisors’ meeting we will outline the geologic history of Northeast Iowa, our current understanding of the NEIPC and compare it with the proven PGE resources in the Duluth Complex. The current USGS research study will be described and the preliminary results discussed, and we will go on to discuss what might be expected from potential future industry exploration in the area and if that is successful how mining operations might develop. Finally, we will try to answer questions about the potential resources and how exploration and extraction operations might affect the county,” Anderson said.

Frac sand
Supervisor Dean Thompson said Anderson’s presentation would be informative to the supervisors as they consider issues that are part of the county’s 18-month moratorium on frac sand mining. The moratorium expires in December.
“What we’re looking for in our fact-finding mission of the county is information about potentials for both industrial non-metallic (silica sand) and metallic-mineral mining in our county. Supervisor Dennis Karlsbroten and I invited Dr. Anderson to speak about potentials for metallic mineral mining based on findings of the U.S. Geological Survey’s 2013 airborne survey of Northeast Iowa,” Thompson said.