U-Pb Analysis of Detrital Zircons in Late Proterozoic Rocks of Arctic Alaska: Implications for Tectonic Evolution of the Canada Basin and Adjacent Polar Margins

点击翻译按钮获取中文摘要

Abstract This award supports a project to study the tectonic evolution of the Arctic by providing paleogeographic constraints on mechanical models proposed for the opening of the Canada Basin. Current geophysical and geological data upon which these models are based typically lack the required detail and resolution (e.g., geophysical data), do not provide unique solutions (e.g., stratigraphic and basin axis correlations), or remain interpretive due to overprinting during younger orogenesis (e.g., structural relationships). The two models that best fit the meager data base invoke (1) rifting of Arctic Alaska-Chukotka from the Lomonosov Ridge followed by sinistral translation along the Canadian Arctic Island margin or (2) rifting and rotation of Arctic Alaska from the Canadian Arctic Islands. These models differ in the assumed pre-Cretaceous paleogeographic position of northern Alaska. Thus isotopic studies designed to constrain the paleogeographic origin of Arctic Alaska could potentially provide significant insights into the evolution of the Canada Basin. Nd isotopic analyses have been successfully utilized to provide general constraints on paleogeographic models. Combining Nd data with U-Pb isotopic analysis of single detrital zircons, which allow discrimination of specific age populations, provides a powerful tool for correlation of displaced stratal sequences and their source regions. This research will involve a U/Pb detrital zircon study of Proterozoic metaclastic rocks at 4 localities across Arctic Alaska in an effort to provide additional constraints on its paleogeographic origin. Proterozoic rocks will be targeted in order to determine the primary cratonal signature and establish a baseline for similar detrital studies in Paleozoic and younger strata of the Arctic Alaska region. Comparison of the resultant isotopic data with known detrital signatures from the Canadian Arctic and Cordilleran margins will bear directly on critical evaluation of current models for the tectonic evolution of the Canada Basin. In addition, results of this study will address the presence or absence of pre- Mississippian terranes, the significance of 2.0 Ga Nd model age reported for Proterozoic rocks in northern Alaska in terms of homogeneous source versus multicomponent mixing, depositional ages of the Proterozoic clastic rocks sampled, and potential correlation of Arctic Alaska with crustal fragments (Yukon-Tanana and Ruby terranes) presently outboard of the Cordilleran miogeocline.