Collaborative Research: Origin of the Alexander Terrane in the Arctic Realm?

University Of Iowa, Iowa City IA

Investigators

Abstract

This project will test the hypothesis that much of southern Alaska formed along the Arctic margin of Canada, with transport to its present position only in the relatively recent geologic past. Such a displacement history is counter to the more traditional view that these rocks, and most other portions of western North America (e.g., Baja California), have moved northward along the continental margin. It also differs from previous suggestions that these rocks formed along the western margin of the paleo-Pacific and are truly exotic to North America. Fortunately, recent technological developments have provided a technique that will provide a robust evaluation of these possible displacement scenarios. The technique involves the determination of ages of zircon crystals in the displaced rocks and in potential correlatives in the western US, along the western margin of the paleo-Pacific, and in the Canadian Arctic. The occurrence of similar ages would suggest potential linkages, whereas the occurrence of different ages of zircon crystals in rocks of the same age would be inconsistent with geographic proximity. This project will provide opportunities for undergraduate and graduate students at two universities to participate in a research project that involves both field studies in frontier regions and laboratory analyses utilizing sophisticated instrumentation. Primary activities involved in this project will include: 1. Conducting geologic field studies and collecting samples from Paleozoic strata of the Alexander terrane in southeast Alaska and the Pearya terrane in the Canadian Arctic. These studies will be based from zodiacs and a live-aboard boat (presently operated by the University of Arizona) in SE Alaska and with helicopter support in the Canadian Arctic. 2. Determining U-Pb ages and Hf isotope ratios of detrital zircons utilizing a new Laser Ablation-ICPMS system (Nu HR ICPMS) and SEM system (Hitachi 3400N and Gatan Chroma CL) at the University of Arizona. 3. Comparison of our new data with U-Pb ages and Hf isotope information from other assemblages in the circum-Pacific and circum-Arctic realms in an effort to test various possible displacement models for the Alexander terrane. Much of the field and lab research will be conducted by graduate students at the University of Arizona and the University of Iowa. Undergraduate students will be involved as field assistants, with possible senior-thesis-type projects available as appropriate.