A Reappraisal of Stress Field and Convective Roll Models for the Origin and Distribution of Cretaceous to Recent Intraplate Volcanism in the Pacific Basin

摘要

Correlations between volcanic output along the Hawaiian and Cook-Austral-Marquesas chains and basin-wide plate reorganizations at 25 and 5 Ma support the contention of Jackson and Shaw (1975) that intraplate volcanism throughout the Pacific basin is controlled by the transmitted stress field. Reconstruction of the Pacific Basin for the Early Cretaceous through Eocene based on a paleomagnetic model demonstrates that oceanic plateaus (Shatsky Rise, Mid-Pacific Mountains, Magellan Rise, Ontong Java) were generated in zones of tension in the wake of retreating triple junctions, and that ocean island chains may be divided on the basis of propagating- or leaky-fracture origin. The latter, including the Louisville, Marshall-Gilbert, Line Island, and Cook-Austral-Mar(1uesas chains show nonlinear age progressions, and followed pre-existing NNW-SSE-trending fracture Zones initiated t)y transform faulting during the early history of the Pacific plate. Volcanism attributed to propagating fractures includes the Sala y Gomez, Juan Fernandez, am Caroline chains, which extrapolate to breaks in nearby subducting slabs, suggesting stressing of the plate by convergent margin geometry. The Emperor Chain is unique in representing volcanism along a propagating fracture induced at a divergent margin. The location and orientation of this chain is attributed to the geometry of the Kula-Pacific Ridge, following plate reorganizations at 82 Ma that prematurely halted triple-junction volcanism on Meiji seamount. Subsequent volcanism along the Hawaiian Chain marks reorientation of the stress field to control by convergent-margin geometry fo1lowing abandonment of the Pacific-Kula Ridge, and (Toes not require a change in Pacific plate motion at 43 Ma. The distribution of Pacific intraplate volcanism is more regular than would expected from plumes, and can he explained as a result of shallow volatile-hearing sources tapped under developing hotcell conditions, with the change from plateau to island chain volcanism reflecting changes in the transmitted stress field induced by large-scale plate interactions.