STRUCTURAL, METAMORPHIC, AND DETRITAL ZIRCON CHARACTERIZATION ACROSS THE BOUNDARIES OF HIGH-PRESSURE ROCKS IN THE BROOKS RANGE OROGEN, NORTHERN ALASKA

Early Cretaceous south-directed subduction resulted in collision between a passive margin and an island arc and created a north-directed fold-thrust belt and two metamorphic belts, the Central Belt and Schist Belt, which altogether form the Brooks Range. The Central Belt and Schist Belt were metamorphosed to greenschist and blueschist/eclogite facies, respectively, during underthrusting of the passive margin. Many aspects of these two belts are poorly understood, including the ages of metamorphism in each belt, their original stratigraphic positions, and the nature of the boundary between them. These ambiguities have led to diverse models for development of the Brooks Range. Hypotheses for the boundary between the high-P Schist Belt and lower P Central Belt include: (1) >100 km of northward thrusting of the Schist Belt over the Central Belt subsequent to high-P metamorphism, (2) N-directed thrusting of the Central Belt over the Schist Belt during high-P metamorphism, and (3) late S-directed backthrusting of the Central Belt over the Schist Belt.

We present tests of these models through detailed field mapping and metamorphic/structural petrographic analysis across the boundary between the two belts along the Wild River, an area which has been poorly studied. Additionally, detrital zircon analyses will be used to characterize the stratigraphy of each belt. The results will provide critical data for testing models for not only tectonic evolution of the Brooks Range but also for understanding exhumation mechanisms of the high-P rocks, and the relationship between Brooks Range evolution and the tectonic development of the broader Arctic region.