Geology, U-Pb Geochronology, and Hf Isotope Geochemistry Across the Alaska Range Suture Zone (South-Central Alaska): Implications for Collisional Processes and Cordilleran Tectonics

Mariah C Romero, Purdue University

Abstract

The Alaska Range suture zone is defined by a transition from outboard oceanic terranes to inboard continental margin terranes; distinguishing south-central Alaska as a prime place to study the progressive development of a collisional tectonic setting. We present 3,206 U-Pb analyses and 406 Hf isotope compositions from detrital zircons obtained from the three main components of the collisional zone: the Ancestral North American continental margin, the oceanic Wrangellia terrane, and the sedimentary strata of the Jurassic-Cretaceous Kahiltna assemblage. U-Pb/Hf datasets from the Ancestral North American continental margin and oceanic Wrangellia terrane provide a provenance reference when comparing the Kahiltna assemblage to the inboard strata of the northwestern Laurentian continental margin and outboard oceanic terranes. U-Pb/Hf datasets from our Ancestral North American margin samples preserve reworked detrital zircons that have been transported from various distal sources. These reworked detrital zircons record distinctive stages of crustal melting events and are interpreted as reflecting crustal thickening during the Archean, Paleoproterozoic, Mesoproterozoic, and Middle Paleozoic. U-Pb/Hf datasets from our Wrangellia terrane samples shows sediment derivation from entirely juvenile magmatic sources that represent magmatism within an oceanic-island arc setting with no continental influence. U-Pb/Hf dataset of detrital zircons from the Kahiltna assemblage samples in south-central Alaska record detritus from various magmatic sources of mainly continental-affinity, with increasing amounts of North American detritus in younger strata. Detrital zircon samples from the Kahiltna assemblage record three stages of regional crustal thickening along northwestern Laurentia during Paleozoic-Mesozoic time (Devonian-Mississippian, Late Triassic-Early Jurassic, and Early Cretaceous-Late Cretaceous time). U-Pb/Hf datasets from our study contribute to the global and regional record of crustal melting events during the Archean, Paleoproterozoic, Mesoproterozoic, Middle Paleozoic, and Mesozoic. Our U-Pb/Hf datasets from three components of the collisional zone contributes to the global record of supercontinent assemblage while providing a strong regional record of crustal evolution of northwestern Laurentia from Devonian through Cretaceous time.

Degree

M.S.

Advisors

Ridgway, Purdue University.

Subject Area

Geology|Sedimentary Geology

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