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Penrose Conference Report nickel titanium, and vanadium around the world. As an illustra- GSA TODAY | www.geosociety.org/gsatoday
tion of how unique and important these environments are, it is
Layered Mafic Intrusions worth highlighting that the Bushveld Complex (South Africa)
and Associated Economic hosts >75% of the world’s exploited platinum. The Stillwater
Deposits Complex also hosts significant economic quantities of these
precious metals, at even higher grades (i.e., 18 ppm Pt+Pd) than
Red Lodge, Montana, USA, 8–12 August 2016 the Bushveld, so it is an important location for understanding
ore-forming processes. In general, it is the combination of the
CONVENERS industrial and scientific relevance of layered intrusions that has
ensured support for research on these intrusions for the past six
Alan E. Boudreau, School of the Environment, Duke University, decades. Despite the large volume of literature dedicated to layered
Durham, North Carolina, USA intrusions, advances in various subdisciplines are somewhat scat-
tered, and there is a need for synthesis of the past 20 years of
Eric C. Ferré, Dept. of Geology, Southern Illinois University, research as well as an urgent need to define the new scientific
Carbondale, Illinois, USA challenges that the broad community and graduate students
should focus on. The Stillwater Complex is an ideal setting in
Brian O’Driscoll, School of Earth and Environmental Sciences, which to consider these challenges, as it combines a rich tradition
University of Manchester, Manchester, UK of petrological research with active economic interests in a rela-
tively easily accessible location. More simply, it is one of the most
Edward M. Ripley, Dept. of Geological Sciences, Indiana important layered intrusions on Earth, in terms of historical study
University, Bloomington, Indiana, USA and quality of exposure.
ORGANIZING COMMITTEE The Geological Society of America Foundation, the National
Science Foundation Petrology and Geochemistry Program, the
S. Barnes, J. Day, M. Cheadle, J. Gee, A. Glazner, T. Kalakay, C. U.S. Geological Survey Mineral Resources Program, the Rocky
Lundstrom, B. Meurer, M. Koski, W. Maier, L. Meinert, P. Moffitt, Mountain Association of Geologists Foundation, and the
J. Scoates, and B. Stewart Stillwater Mining Company Foundation jointly sponsored this
Penrose Conference.
INTRODUCTION
The conference, held at the Rock Creek Resort in Red Lodge,
Layered mafic intrusions (LMI) play a central role in our Montana, USA, from 8 August through 12 August 2016, gathered
understanding of magmatic systems. They also represent one of an impressive array of 58 experts and six industry delegates from
the fundamental modes of magma transfer from the upper mantle Taiwan, Germany, the UK, Canada, South Africa, and the U.S.
to the crust. These magmatic systems formed throughout geologic
time from the Archean (e.g., Stillwater Complex) to the Paleogene PRESENTATIONS AND FIELD TRIP
(e.g., Skaergaard Complex) on all five continents. As many of the
best-studied layered intrusions are associated with Large Igneous Participants met in session, exchanged new results, discussed
Provinces, they are largely independent from tectonic processes at critical scientific questions, and engaged with one another on the
plate boundaries. Layered intrusions have generated significant outcrops of the Stillwater Complex during two days of geological
historic interest from the igneous petrology and geochemistry excursions led by Alan Boudreau and Mike Zientek on the
communities because they lie at the heart of some of the most Stillwater Complex.
fundamental petrologic precepts, such as fractional crystallization
and Bowen’s reaction series. These intrusions also host first-class The major aims of the conference were to define the critical
economic deposits of platinum group elements (PGE), chrome, scientific questions that the community will need to address in
the next decade, to foster collaboration with industrial partners,
and to promote exchange between the generation of senior scien-
tists and younger academics. Thirteen graduate students (nine of
whom were women) and seven early-career scientists (four of
whom were women) were supported through the generous dona-
tions of our sponsors. The format of the discussions actively
promoted the intellectual contribution of younger scientists.
The scientific party collectively defined the following key
questions:
• What are the timescales of emplacement and cooling of LMI?
• What is the physical nature of a magma chamber?
• Have large volume mafic magma chambers ever existed?
• How do monomineralic layers form in LMI?
• How much crustal contamination occurs in LMI magmatism?
• In what tectonic settings are LMI likely to form?
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