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Date Permissions Signed
Date of Award
Master of Science (MS)
Schermer, Elizabeth, 1959-
McClelland, Bill C.
The Mesoproterozoic MARA terrane of South America has been interpreted to collide and subduct beneath the Gondwana margin of South America in the Cambrian. To test the proposed tectonic model, I combine metamorphic petrology and geochronology along with quantitative thermobarometry to constrain metamorphic events and peak conditions within the Sierra de Maz of the MARA terrane and the adjacent Sierra de Ramaditas. Foliations within the Sierra de Maz are steeply east dipping, with a major sinistral reverse shear zone separating the two major units (Zaino and Maz Complexes) of the northern range. Garnet Lu-Hf records a single metamorphic event in the Zaino Complex at ~425 Ma. Combined garnet Lu-Hf and monazite U-Pb reveal a polymetamorphic history in the Maz Complex with two distinct metamorphic events at ~1.2 Ga and ~425 Ma. Both Complexes were deformed by sinstral transpression between 435 and 415 Ma. Preserved across these Complexes is a Silurian-Devonian amphibolite to granulite inverted metamorphic field gradient that is compatible with observed and modeled gradients from other transpressive orogens. The Ramaditas complex records lower-pressure granulite facies metamorphism at ~460 Ma, was deformed at ~426 Ma, and is correlated with the Famatina arc rather than its previously proposed affiliation to units in the Sierra de Maz. Units of the Sierra de Maz do not share metamorphic histories with nearby ranges within the proposed extent of the MARA terrane. Age dissimilarities require that portions of the MARA terrane were tectonically juxtaposed likely as a result of transpressive translation along the Gondwana margin.
MARA, South America, Sierra de Maz, garnet, monazite, transpression
Western Washington University
La Rioja (Argentina : Province)
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Tholt, Andrew, "Metamorphic Evolution of the Sierra de Maz: Implications for the Timing of Terrane Accretion on the Western Margin of Gondwana" (2018). WWU Graduate School Collection. 713.