An open-system, two-layer crustal stretching model for the Eastern Great Basin

摘要: New geological and geophysical information from the eastern Great Basin sheds light on how Cenozoic extensional strain is partitioned throughout crustal column provides broad constraints much new material was added to crust as a consequence of synextensional magmatism. The total amount extension across half northern Range province estimated be 141 km or 77%, but varies dramatically more local scales. Individual domains, several tens kilometers across, have experienced supracrustal strains that vary 15% 300%. Volcanism in this region initiated early Oligocene has continued sporadically present. major eruptions appear both temporally spatially associated with large-magnitude extension. A COCORP deep seismic reflection profile indicates uniform present thickness 30 35 km. preextensional inferred tapered westward 40- 45-km Colorado Plateau maximum 50 thickened root zone Sevier fold thrust belt. Simple mass-balance calculations employing thicknesses together suggest approximately 5 during lack relief Moho suggests whole may stretched quite uniformly. model for stretching incorporates heterogeneously deforming (brittle) upper decoupled uniformly (ductile) middle lower crust, significant flux mantle-derived magmas into best explains observations Basin. This open-system, two layer important thermal mechanical implications helps account many enigmatic aspects magmatism western United States.