Objectives of the Field Course
Mafic layered intrusions (MLI) are a class of large igneous bodies that display stratigraphic changes of rock types and mineral compositions resulting from the progressive cooling and crystallization of a mafic magma from the margins inward, coupled with periodic magmatic recharge and venting. MLI are very important economically, as many are host to world class ore deposits of copper, nickel, cobalt, precious metals, titanium, vanadium and chromium. The stratified nature of MLI is typically defined by various types of layering (modal, phase, textural, cryptic) and by igneous foliation. MLI-hosted ore deposit also tend to be stratiform and conformable with the internal structure of the host intrusion. Stratigraphic variations in mineralogy, texture, mineral composition, and whole rock geochemistry within an MLI reveals evidence of its parental magma composition and records the petrogenetic and metallogenic history of the magma. Being able to document the lithostratigraphy of MLI by field mapping is the first step in unraveling that history.
The principal objective of this field course is to provide advanced field training for professional geologists looking to develop or hone their mapping, observational, and interpretive skills that are best suited to field studies of mafic layered intrusions. The camp will involve mapping exercises focused on two MLI that occur in northeastern Minnesota which are part of the 1.1 Ga Midcontinent Rift. These are the Layered Series at Duluth – the type-intrusion of the Duluth Complex, and the Skaergaard-like, Sonju Lake intrusion – the most completely differentiated MLI in the Midcontinent Rift (Fig. 1).
What this course purposely does not offer is training in various field mapping hardware or software applications. Although computers loaded with basic spreadsheet, imaging, and GIS applications will be available for use throughout the camp, these are intended to allow participants to view and integrate their field data with previously acquired geologic, geophysical, geochemical and drill core data in order to make reasonable geologic and mineral potential interpretations. No high-priced, technologically-advanced gizmo or fancy application will fix poor observations or inaccurate mapping. As the adage goes – garbage in – garbage out. This course will teach how to avoid garbage in.
Specific skill sets to be taught during this course include:
- constructing useful field base maps
- neatly and accurately recording field information on field maps and in notebooks
- packing necessary field equipment
- developing navigational, logistical and safety skills necessary to maneuver through boreal forests of the Canadian Shield
- field identification of mafic minerals and their alteration products
- recognition of cumulate textures
- recognition and accurate measurement of internal structures (layering and foliation)
- integrating field data with geophysical, geochemical and drill core data to make reasonable geologic interpretations
- using that same integrated database to evaluate the potential for PGE reef mineralization
The course will include a series of lectures on the following topics:
The core activity of the field course will involve five days of detail bedrock mapping in the two layered intrusion areas. Participants will work in small field parties (2-4) and will produce basic geologic maps and mineral potential interpretations.
- regional overview of the Mesoproterozoic geology of northeastern Minnesota
- mineralogical, textural and structural attributes of MLI
- classification and nomenclature applied to MLI
- mineral deposits hosted by MLI
Geologic Setting of the Field Course Area
The geology of northeastern Minnesota is largely composed of intrusive and volcanic rocks (Fig. 1) that formed during the 1.1 Ga Midcontinent Rift. A volcanic edifice of over 10 km of subaerial basalts and lesser rhyolite, termed the North Shore volcanics accumulated on the northwestern flank of the rift trough, that is now centered over western Lake Superior. Multiple large sheet-like intrusions of mafic and felsic magmas that were emplaced into the basal part of the North Shore volcanics are collectively called the Duluth Complex. These intrusions are subdivided into four series based on their age, internal structure and dominant lithologies – Felsic Series, Early Gabbro Series, Anorthositic Series, Layered Series. The Layered Series is composed of about a dozen individual mafic layered intrusions. The best exposed of these, and the focus of the first half of this course, is the Layered Series at Duluth.
A suite of mafic to felsic intrusions emplaced into the more medial section of the North Shore volcanics is collectively termed the Beaver Bay Complex. Massive hypabyssal intrusions dominate the Beaver Bay Complex, but one noteable exception is the well-differentiated Sonju Lake intrusion (Fig. 1). Mapping out the lithostratigraphy of this Skaergaard-like intrusion will be the focus of the second half of this field course.
Field Course Instructors
The field course will be principally taught by Jim Miller and Dean Peterson, two geologists who have extensive experience in field studies and mineral prospecting in the Duluth Complex and related intrusive complexes in northeastern Minnesota. The course will be assisted by George Hudak, an expert geologic mapper, who specializes in Archean volcanic terranes. For the past 6 years, these three instructors have been principal teachers for the Precambrian Research Center’s Precambrian field camp – a six-week field course intended for undergraduate geology students.
Jim Miller, PhD - Associate Professor, Department of Geological Sciences and Administrative Director, Precambrian Research Center, University of Minnesota Duluth
Research Interests: Field mapping, igneous petrology and metallogeny of the Duluth Complex and related intrusions associated with the Midcontinent Rift. From 1983 to 2008, Jim was a senior geologist with the Minnesota Geological Survey charged with conducting field studies of the Duluth Complex. In joining the Department of Geological Sciences at UMD in 2008, he teaches a Geologic Maps course and advises MS students on thesis topics typically involving mapping. He has authored or coauthored over 25 geological maps of various areas throughout northeastern Minnesota.
Dean Peterson, Ph.D. - Senior Vice President of Exploration, Duluth Metals Ltd, Duluth, MN and Associate Director, Precambrian Research Center, University of Minnesota Duluth.
Research Interests: Economic geology, geological mapping, Precambrian geology, mineral potential modeling, and three-dimensional modeling of ore systems. Dean has broad experience in geological mapping of rocks of all types, ages, and locations mainly through work with the mineral exploration industry in search of mesothermal-gold, epithermal-gold, volcanogenic massive sulfide, copper-nickel-PGE in the Duluth Complex, high-grade copper-PGE veins beneath the Sudbury Igneous Complex, and copper-gold-molybdenum porphyry deposits.
George Hudak, Ph.D., P. Geo., P.G. – Senior Research Associate, Natural Resources Research Institute and Assistant Director, Precambrian Research Center, University of Minnesota Duluth
Research Interests: Field-based volcanic facies and hydrothermal alteration mineral facies mapping associated with Neoarchean VMS and epithermal gold deposits; variations in mineral chemistry across ancient submarine hydrothermal alteration zones; geochemistry of Precambrian volcanic rocks and associated hydrothermal alteration zones, and mineralization. George has extensive field mapping experience in greenstone-granite terranes throughout the Canadian Shield, including the Timmins, Sturgeon Lake and Geraldton-Beardmore camps in Ontario and the Vermilion District of Minnesota.
Course Schedule (preliminary)
Sunday, Oct. 13 – Welcome, Introductions
5-6PM Welcoming Reception (Inn on Lake Superior, Canal Park, Duluth)
7-9 Introductory Lectures
Monday, Oct. 14 – Layered Series at Duluth Mapping Exercise
8-10 Introductory Lectures (cont.)
10-5 Introduction to DLS field area, preliminary mapping
6-8 Group dinner at Canal Park establishment
Tuesday, Oct. 15 – Layered Series at Duluth Mapping Exercise
8-5AM DLS mapping
5-8 Free time, dinner on own
8-10 Lab – DLS compilation
Wednesday, Oct. 16 – Layered Series at Duluth Mapping Exercise
8-1 DLS mapping
2-5 Lab-DLS compilation
5-6:30 Group dinner at Canal Park establishment
6:30-8 Preparation for Sonju Lake Mapping
8-10 Lab - complete DLS map
Thursday, Oct. 17 – Sonju Lake Intrusion Mapping Exercise
8-10 Drive to SLI field area
10-4 Group traverse of SLI stratigraphy
4-6 Check in at Wolf Ridge ELC; Dinner
7-10 Lab – feedback on DLS map, SLI compilation
Friday, Oct. 18 – Sonju Lake Intrusion Mapping Exercise
8-5 SLI mapping
5-7 Dinner at Wolf Ridge
7-10 Lab- SLI compilation
Saturday, Oct. 19 – Sonju Lake Intrusion Mapping Exercise
8-2 SLI mapping
2-4 Return to Inn on LS, Duluth
5-7 Group dinner at Canal Park establishment
7-10 Lab - complete SLI map; PGE reef targeting
Sunday, Oct. 20- Final Presentations
9-12 Presentation of SLI mapping, PGE reef targeting
12-1 Lunch; End of Course
Registration for the complete field course is limited to 20 participants with preference given to PRC members*. PRC members have until June 28th to register for the slots reserved according to their membership level. After June 15th, all remaining slots will be accepted on a first come – first serve basis contingent upon receipt of the registration form and full payment of the field course fee. After August 30, registration costs for any remaining slots will increase by $500.
Field Course Registration $4200 before 8/30/13
$4700 after 8/30/13
< Download Registration Form>
Field course registration includes:
- Field course notebook and CD of Powerpoint lectures, handouts, and reprints
- Field trip guidebook for the Layered Series at Duluth and Sonju Lake Intrusion
- All field equipment and mapping supplies need to complete mapping exercises
- Certificate of attendance indicating contact hours
- Van transport during field course
- Single-room lodging at the Inn on Lake Superior (10/13-10/16 & 10/19); dormitory lodging at Wolf Ridge ELC (10/17-18)
- All meals from Sunday (10/13) dinner through Sunday (10/20) lunch, except dinner on Tuesday (10/15)
Accommodations and Lab Facilities
All registrants will be provided single room lodging at the Inn on Lake Superior for the nights of 10/13-16 and 10/19. During our two-night stay (10/17-18) at Wolf Ridge Environmental Learning Center, participants will be housed in dormitory-style accommodations. Evening labs will be held in rooms furnished with tables, computers, printers, drafting materials, and petrographic microscopes.
A full course refund will be given if notice of cancellation is received by Monday, September 30th. Program obligations make it necessary to assess a charge equal to one-quarter of the course fee ($1050) for later cancellations. No course refund is possible after the course begins on October 13th.
Arrival in Duluth
Daily flights into Duluth International Airport are provided by Delta, United, and Allegiant Airlines with arriving from Minneapolis-St. Paul, Detroit, Chicago, Las Vegas, and Phoenix. The Inn on Lake Superior provides shuttle transport to and from the Duluth International Airport. Call (218) 726-1111 (Toll-Free (888) 668-4352) to arrange a pick-up.
Participants additional information about Duluth can call the Duluth Convention and Visitors Bureau at 1-800-4-DULUTH (438-5884) or visit their website (http://www.visitduluth.com/). For additional information about Minnesota, call the Minnesota Office of Tourism at 888-TOURISM (868-7476) or visit their website at http://www.exploreminnesota.com/.
Field Course Information – Jim Miller (firstname.lastname@example.org)
218-726-6582 , 218-392-5320 (cell)
Registration, Lodging - Julie Anne Heinz (email@example.com)