Depths and temperatures of <10.5 Ma mantle melting and the lithosphere‐asthenosphere boundary below southern Oregon and northern California
Depths and temperatures of <10.5 Ma mantle melting and the lithosphere‐asthenosphere boundary below southern Oregon and northern California
复制标题
俄勒冈州南部和加利福尼亚州北部以下<10.5Ma地幔熔化的深度和温度以及岩石圈-软流圈边界
DOI：
10.1002/ggge.20070
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
W. Hart
中科院分区：
文献类型：
--
作者：
C. Till;T. Grove;R. Carlson;J. Donnelly;M. Fouch;L. Wagner;W. Hart
Plagioclase and spinel lherzolite thermometry and barometry are applied to an extensive geochemical dataset of young (<10.5 Ma) primitive basaltic lavas from across Oregon's High Lava Plains, California's Modoc Plateau, and the central‐southern Cascades volcanic arc to calculate the depths and temperatures of mantle melting. This study focuses on basalts with low pre‐eruptive H2O contents that are little fractionated near‐primary melts of mantle peridotite (i.e., basalts thought to be products of anhydrous decompression mantle melting). Calculated minimum depths of nominally anhydrous melt extraction are 40–58 km below Oregon's High Lava Plains, 41–51 km below the Modoc Plateau, and 37–60 km below the central and southern Cascades arc. The calculated depths are very close to Moho depths as determined from a number of regional geophysical studies and suggest that the geophysical Moho and lithosphere‐asthenosphere boundary in this region are located in very close proximity to one another (within 5–10 km). The basalts originated at 1185–1383°C and point to a generally warm mantle beneath this area but not one hot enough to obviously require a plume contribution. Our results, combined with a range of other geologic, geophysical, and geochemical constraints, are consistent with a regional model whereby anhydrous mantle melting over the last 10.5 Ma in a modern convergent margin and back arc was driven by subduction‐induced corner flow in the mantle wedge, and to a lesser extent, toroidal flow around the southern edge of the subducting Juan de Fuca and Gorda plates, and crustal extension‐related upwelling of the shallow mantle.
