Age and Origin of the Resurrection Ophiolite and Associated Turbidites of the Chugach-Prince William Terrane, Kenai Peninsula, Alaska

摘要

Detrital zircon U-Pb ages from the Valdez and Orca Groups and postaccretion plutons from Resurrection Bay and western Prince William Sound help resolve a long-standing debate involving the timing of formation and emplacement of the Resurrection Peninsula ophiolite into the Chugach-Prince William accretionary complex of southern Alaska. Maximum depositional ages of interbedded turbidites of the Orca Group and pillow basalts of the Resurrection Peninsula ophiolite are 57-58 Ma, and these rocks are deformed and intruded by near-trench plutons of the Sanak-Barnof belt that yield a U-Pb zircon crystallization age of 56 Ma. Inferred depositional ages from detrital zircon in turbidites from the structurally adjacent Valdez Group confirm that this sequence is slightly older and predates the Orca Group. The interbedded and crosscutting relationships between the mafic rocks of the Resurrection and Knight Island ophiolites and the Orca turbidites, the mixing of Orca sediments and mantle melts to form the geochemically distinct igneous rocks of the ophiolites, and the near-synchronous intrusion of forearc plutons immediately followed by thrusting and crustal thickening in the accretionary wedge suggest that the ophiolites formed in a suprasubduction zone setting.