GAC-MAC 2013: Field Guide Summary

Neoarchean Mafic– Ultramafic Intrusions in the Bird River Greenstone Belt:

Tectonic Setting and Economic Significance

H. P. Gilbert
Manitoba Geological Survey, 360-1395 Ellice Avenue, Winnipeg, MB, Canada, R3G 3P2.
J. S. Scoates
Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 6339 Stores Road, Vancouver, BC, Canada, V6T 1Z4.
R.F. J. Scoates
2502 Holyrood Drive, Nanaimo, BC, Canada, V9S 4K9.
X. M. Yang
Manitoba Geological Survey, 360-1395 Ellice Avenue, Winnipeg, MB, Canada, R3G 3P2.
C. A. Mealin
Ontario Geological Survey, Willet Green Miller Centre, Level B7, 933 Ramsey Lake Road, Sudbury, ON, Canada, P3E 6B5.
M. G. Houlé
Geological Survey of Canada, Earth Sciences Sector, 490 rue de la Couronne, Québec, QC, Canada, G1K 9A9.
C. R. Galeschuk
Mustang Minerals Corp., P.O. Box 670, S18 - 24 Aberdeen Avenue Pinawa, MB, Canada, R0E 1L0.
GAC–MAC Winnipeg 2013, post-meeting field trip

FIELD TRIP OBJECTIVES

1 The Neoarchean Bird River greenstone belt in southeastern Manitoba contains a variety of mafic to ultramafic intrusions that host significant Ni-Cu-(PGE) and chromite mineralization. This excursion will focus on magmatic stratigraphy, chromitite layering and associated mineralization in the Neoarchean Bird River Sill and Mayville intrusion (Figs. 1, 2), located within the main part and northern arm, respectively, of the Bird River greenstone belt. In addition to the surface exposures, drillcore will be examined from the Ni-Cu-(PGE) M2 deposit and the PGE-reef style mineralization in the Mayville intrusion, as well as the Ni-Cu-(PGE) orebodies at the former Maskwa-Dumbarton Mine within the Bird River Sill.

Figure 1. Typical exposure of the ore zone at the M2 site in the Mayville intrusion.
Thumbnail of Figure 1Display large image of Figure 1
Figure 2. Medium-grained to very coarse grained leucogabbro (Mayville intrusion).
Thumbnail of Figure 2Display large image of Figure 2

2 This field excursion in the Bird River greenstone belt provides a unique opportunity to examine and compare two contemporaneous (ca. 2.745 Ga) Neoarchean mafic to ultra-mafic intrusions that are separated by an approximately 20 km wide granitoid terrane containing some relatively older (Mesoarchean) intrusive phases. The trip complements the GAC–MAC 2013 Special Session entitled Magmatic Ni-Cu-PGE-Cr Deposits: Ore-Forming Processes with Implications for Exploration.

OTHER INFORMATION

3 The 3-day trip is based at the Wilderness Edge conference centre at Pinawa (100 km east-northeast of Winnipeg). It will depart from Winnipeg directly after technical sessions on May 24 and return on the evening of May 27. A moderate level of physical activity is involved (at least 1-3 km daily) and sturdy footwear and raingear are recommended. Parts of the Mayville intrusion may not be accessible because of high water levels, in which case an alternative itinerary will be run.