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Date of Award
2020
Document Type
Campus Access Master's Thesis
Degree Name
Master of Science in Geology (MS)
Administrative Home Department
Department of Geological and Mining Engineering and Sciences
Advisor 1
Chad D. Deering
Advisor 2
James M. DeGraff
Committee Member 1
Nadia Malaspina
Abstract
The Bell Creek batholith, located in the Upper Peninsula of Michigan, lies on the southern edge of the Archean Superior Craton. The Paleoproterozoic batholith, exhumed during the Penokean Orogeny (1.89 Ga ago), exhibits amphibolite-facies metamorphism. This orogeny and subsequent deformation events have produced a complex suite of overprinting textural and mineralogical features previously not carefully examined. Consequently, significant uncertainty has existed about prior interpretations of the textural characteristics of Bell Creek rocks and their petrogenesis. Textural and compositional characteristics previously interpreted as metamorphic in origin are now interpreted to be primary igneous in origin. Such characteristics include: 1) flame-like and convoluted continuous banded structures, 2) almandine crystals in chemical equilibrium with micas in roundish xenoliths (clots), and 3) preferred alignment of K-feldspar megacrysts parallel to the orientation of banding manifested by biotite schlieren. Results presented here indicate that the Bell Creek batholith, a megacrystic S-type peraluminous granitoid, formed by melting amphibolite previously emplaced in the lower crust, followed by assimilation of mid to upper crustal-level metapelites. The chemistry of amphibole and plagioclase in the mafic units, together with field observations, reveals a component of mixing between the granitoid body and several generations of mafic intrusions.
Recommended Citation
Dalle Fratte, Anna, "GEOCHEMICAL AND PETROLOGICAL EVIDENCE OF THE GEODYNAMIC EVOLUTION OF THE BELL CREEK BATHOLITH, REPUBLIC QUADRANGLE, MARQUETTE", Campus Access Master's Thesis, Michigan Technological University, 2020.