Archean supracrustal rocks on northern Baffin Island Nunavut
Archean supracrustal rocks on northern Baffin Island, Nunavut: defining the Mary River Group Erin Bros, MSc Candidate Finnigan Award Recipient 2019 PHOTO CREDIT: S. JOHNSTON co-author: Johnston S. 2 1, 2 Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta
OUTLINE • GEMII North Baffin Project • MSc Thesis Goals • Regional Geology • Long Lake • Regional Considerations • Next Steps PHOTO CREDIT: S. JOHNSTON
LOCATION From Skipton et al. , 2017
MSC GOALS • GEOLOGICAL MAP • OUTLINE STRATIGRAPHY • STRUCTURAL SETTING • BROAD DEPOSITIONAL AND TECTONIC ENVIRONMENT • REGIONAL MRG CORRELATION • NORTH BAFFIN GEOLOGICAL FRAMEWORK • FURTHER EXPLORATION POTENTIAL
REGIONAL GEOLOGY RAE CRATON • Archean granite-greenstone terrain • Greenschist to granulite facies • Meso- to Neoarchean supracrustal rocks make up greenstone belts • Northeast trending, elongate bodies • Five major events of reworking and deformation (Jackson & Berman, 2005) NORTHERN BAFFIN ISLAND • Meso- to Neoarchean volcanic and sedimentary successions with banded iron formation, represented as the Mary River Group • Surrounding Neoarchean felsic plutonic rocks and Mesoarchean basement gneiss • Evidence for original unconformable relationship at Eqe Bay (Bethune & Scammell, 2003 a) From Liu et al. , 2016
From Skipton et al. , 2017 LONG LAKE • Located western Tuktuliarvik region • Well exposed metamorphosed sedimentary, volcanic and banded iron formation sequence • No basement contact observed
Upper MRG Lower MRG
GEOCHEMISTRY • Very broad sample set, nine metavolcanic rocks • Two distinct sets: felsic and mafic • Calc-alkaline, crustal source • Primitive, tholeiitic basalts From Pearce, 1996
GEOCHEMISTRY • Nb signature • Similarity to other MRG rocks • Suggestive of a continental arc setting with oceanic source From Pearce, 1996; Bethune & Scammell, 2003 a • • • E 113 A 1 rhyodacite E 113 A 3 rhyodacite E 115 A basalt E 116 C basalt E 119 A rhyolite E 124 C basalt E 134 C trachy-andesi E 135 A 1 basalt E 138 D basalt
STRUCTURE • Layer parallel foliated, lineated, folded sequence • Striking northeast, moderate plunge to the southeast • Three generations folding (Young et al. , 2004)
METAMORPHISM • Amphibolite facies • Garnet and hornblende pseudomorphs syn- to post-deformation • Evidence for earlier events too altered • Last event (1. 8 -1. 9 Ga) interpreted main metamorphic footprint
MRG STRATIGRAPHY • Lower and Upper MRG • Developing continental volcanic arc, previously suggested by Gross (1980, 1983) and Jackson (2000) • Multiple BIF occurrences, Superior and Algoma type suggest two different depositional environments 1. Sedimentation and felsic volcanism (lower BIF) 2. Mafic volcanism 3. Sedimentation and intermediate to ultramafic volcanism (upper BIF) 4. Sedimentation and felsic plutonism
ca. 2700 ca. 2716 ca. 2713 ca. 2718 ca. 2719 ca. 2718 ca. 2707 ca. 2755 ca. 2726 -2702 ca. 2735 ca. 2748 ca. 2775 ca. 2778 1. Jackson et al. , 1990 2. Bethune & Scammell, 2003 a 3. Fulcher et al. , 2015 *In-situ 206 Pb/207 Pb 4. Skipton et al. , in press ? ? Eqe Bay Long Lake Mary River Mine E Mary River From Skipton et al. , 2017 ca. 2805 ca. 2830 ca. 2843 ~ca. 3100 -2850 All ages in Ma ca. 2851 ca. 2888 ca. 2896 ? ?
REGIONAL IMPLICATIONS • Re-evaluation age supracrustal rocks of Mary River Group • Interpreted unconformity between basement gneiss and supracrustal deposition • Timing felsic plutonism syn to post -supracrustal deposition
EXPLORATION IMPLICATIONS • Too high grade for significant gold (Herbranson, 2013) Meadowbank BIF-hosted gold, green schist to amphibolite facies, Woodburn Lake Musselwhite BIF-hosted gold, structurally controlled F 2 folds, amphibolite facies • What can Archean Superior BIF mean? • Bimodal volcanism. . . VMS? • Geochemistry of felsic intrusions
NEXT STEPS • Geochemistry on metasedimentary rocks, BIF • Archean deformation evidence? • Correlation to units around Pond Inlet and Barnes Ice Cap
Known Prospective
THANK YOU NAKURMIIK QUJANNAMIIK NAPEG GEM 2 Team Dr. Stephen Johnston NMS INAC Dr. Brendan Dyck Baffinland
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