期刊
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
卷 13, 期 -, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2012GC004189
关键词
intraplate volcanism; mantle dynamics; mantle upwelling; slab rollback; subduction
资金
- NSF Continental Dynamics program [EAR-0507248, EAR-0506914, EAR-0507486, EAR-0506857]
- NSF EarthScope Science program [EAR-0548288]
- NSF [EAR-0809192]
- Alfred P. Sloan Research Fellowship
- Division Of Earth Sciences
- Directorate For Geosciences [0911268] Funding Source: National Science Foundation
The Pacific Northwest (PNW) has a complex tectonic history and over the past similar to 17 Ma has played host to several major episodes of intraplate volcanism. These events include the Steens/Columbia River flood basalts (CRB) and the striking spatiotemporal trends of the Yellowstone/Snake River Plain (Y/SRP) and High Lava Plains (HLP) regions. Several different models have been proposed to explain these features, which variously invoke the putative Yellowstone plume, rollback and steepening of the Cascadia slab, extensional processes in the lithosphere, or a combination of these. Here we integrate seismologic, geodynamic, geochemical, and petrologic results from the multidisciplinary HLP project and associated analyses of EarthScope USArray seismic data to propose a conceptual model for post-20 Ma mantle dynamics beneath the PNW and the relationships between mantle flow and surface tectonomagmatic activity. This model invokes rollback subduction as the main driver for mantle flow beneath the PNW beginning at similar to 20 Ma. A major pulse of upwelling due to slab rollback and upper plate extension and consequent melting produced the Steens/CRB volcanism, and continuing trench migration enabled mantle upwelling and hot, shallow melting beneath the HLP. An additional buoyant mantle upwelling is required to explain the Y/SRP volcanism, but subduction-related processes may well have played a primary role in controlling its timing and location, and this upwelling likely continues today in some form. This conceptual model makes predictions that are broadly consistent with seismic observations, geodynamic modeling experiments, and petrologic and geochemical constraints.
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