This page is no longer being updated and remains online for informational and historical purposes only. The information is accurate as of the last page update.
For questions about page contents, contact the Communications Division.
Underground mine geologist Sheila Hutcherson will speak on “Geology from Beneath the Surface — Gold and Platinum Mining from a Geologist’s Point of View” noon today in Van Wickle Hall room 108.
Lunch will be provided free of charge to students and for $3 to faculty and staff. The event is part of the Geology Spring Seminar Series sponsored by the geology and environmental geosciences department.
Hutcherson will discuss the methods she uses on the job and what it is like to work as an underground geologist. She also will talk about precious metal occurrences in Montana’s Stillwater Complex and Nevada’s Carlin-type gold deposits.
Since October 2002, she has worked for Newmont Mining Company in Carlin, Nev. Previously, Hutcherson was employed from July 2001-October 2002 for Stillwater Mining Company as an ore control geologist. She received a B.S. in earth and planetary sciences from University of New Mexico, where she was president of the student chapter of Society of Economic Geologists from 2000-01 and was named outstanding field geologist for the geology department in 1999. She earned an M.S. in economic geology from Mackay School of Mines, where she completed a master’s thesis on a Carlin-type deposit in the Jerritt Canyon District near Elko, Nev.
Carlin-type gold deposits are one of the most important types of gold deposits in the United States.
“They are formed in structurally complex environments at depths of two to four kilometers,” says Hutcherson. “Gold mineralization is typically found as microscopic disseminations associated with pyrite and aresenopyrite in a host lithology of silty-carbonates and/or intrusives. Tracer elements associated with gold include arsenic, barium, mercury, and antimony. Alteration associated with Carlin-type deposits includes silicification, decarbonatization, and argillization. The formation of Carlin-type deposits is enigmatic, but current evidence suggests there is a magmatic link. I will discuss the geology of two underground Carlin-type Au mines (Carlin East and Murray) and compare and contrast their geologic features.”
Hutcherson’s second area of discussion will be the layered Stillwater deposit in Montana.
“The Stillwater deposit is a layered mafic intrusion with platinum/palladium mineralization,” she says. “These types of deposits are not common, and the Stillwater complex is the only one identified in North America. Platinum Group Mineralization is found disseminated in copper and nickel sulfides in what is called the J-M Reef, an assemblage of mafic and ultra mafic rocks formed in an early Precambrian igneous intrusion approximately 2.7 billion years ago. During formation, the magma body was fluid, allowing individual minerals to crystallize first, sinking to the bottom based on their crystal chemistry. Over time, the original horizontal orientation of the reef was changed and tilted at an angle of 50 to 90 degrees to the north.
“Finally, I will discuss how the differences between Carlin-type Au deposits and Pt-Pd bearing layered mafic intrusions require the utilization of different geologic methods to ensure that most efficient mining of the ore body occurs.”
In the next Geology Seminar, Steve Clemens, senior research associate in geological sciences at Brown University, will discuss the causes of variations in the strength of Asian monsoons noon-1 p.m. Friday, April 2.
Harvard curator Bill Metropolis will discuss the university’s collection of minerals and offer samples for examination noon Friday, April 23.
Previous Geology Seminar talks:
Dana Emerson ’03, AmeriCorps program within the New Jersey Department of Environmental Protection, March 5: environmental outreach work
Annette Russo ’80, senior manager of global environment, health, and safety and mobility for telecommunications firm Avaya Inc. in Basking Ridge, N.J., Feb. 20 — “Trends in Environmental Programs and Legislation and Industry Response in a Post-9/11 World”
Guy Hovis, John H. Markle Professor of Geology, Feb. 6: “A European Sabbatical Travelogue — and Why I Destroy Minerals”