Anatexis and crustal differentiation: insights from the Fosdick migmatite--granite complex, West Antarctica
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Anatexis
Migmatite
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University of Minnesota M.S. thesis. January 2013. Major: Geological Sciences. Advisor: Dr. John Goodge. 1 computer file (PDF); x, 197 pages, appendices A-C.
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Queen (butterfly)
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The Mesoproterozoic English Bay Complex consists of a granite-rhyolite assemblage outcropping on the shores of Lake Nipigon in western Superior Province, Canada. It intrudes Neoarchean rocks and is disconformably overlain by a rift–infracratonic basin sedimentary succession recording subsidence following a heating event. The granites and rhyolites are characterized by light rare-earth element (LREE) enrichment (La/Sm n = 2.8–5.1) and only weakly fractionated heavy REE (HREE; Gd/Yb n = 1.1–1.6). The felsic igneous rocks are high-K, enriched in Zr, Nb, Y, and REE satisfying all the criteria for an A-type suite. Trace element geochemistry, particularly the absence of any negative Nb anomalies, indicates this melt did not originate in a suprasubduction zone setting, unlike the St. Francois Mountain Complex to the south. The English Bay Complex may record the northern portion of a Mesoproterozoic plume track— a plume that possibly led to earlier igneous activity and infracratonic basin formation to the north and would later interact with a suprasubduction zone margin to the south.
Felsic
Outcrop
Large igneous province
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University of Minnesota M.S. thesis. November 2014. Major: Geological Sciences. Advisor: Dr. John Goodge. 1 computer file (PDF); vi, 61 pages, appendices A-C.
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Petrogenesis
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Petrogenesis
Ultramafic rock
Greenstone belt
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Anatexis
Geochronology
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The Fosdick Mountains, West Antarctica, form an 80 × 15 km migmatite dome comprising massive paragneisses that exhibit polyphase fabrics, nappe-scale folds that involve granodiorite to leucogranite intrusions, and diatexite. High strain zones developed on the NE flank of the dome. Multiple generations of leucogranite sheets, dikes and diatexite intrude the dome, and evidence for partial melt in structural sites is widespread. Macroscopic folds and the maximum anisotropy of magnetic susceptibility (AMS) direction are oriented NE-SW, generally parallel with the N65W regional finite strain axis determined from brittle faults and a mafic dike array outside the dome. The direction is...
Leucogranite
Dome (geology)
Dike
Migmatite
Lineation
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