Ophiolitic basement to a forearc basin and implications for continental growth: The Coast Range Great Valley ophiolite, California

被引:64
作者
Godfrey, NJ [1 ]
Klemperer, SL [1 ]
机构
[1] Stanford Univ, Dept Geophys, Stanford, CA 94305 USA
关键词
D O I
10.1029/98TC01536
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We present a compilation of 18 published models from the length of the Great Valley forearc basin, California, based on seismic reflection, borehole, seismic refraction, gravity, and aeromagnetic data to address long-standing questions about the nature of the basement to the Great Valley, its origin, its tectonic history, and it's mechanism of incorporation into the North American continental margin. The geophysical models permit a 700-km-long, 70-km-wide, complete ophiolite sequence beneath the entire Great Valley. In the northern Great Valley, the ophiolite is overlain by ophiolitic breccia, the ophiolite crust is 7 - 8 km thick, and the mantle section is mostly unserpentinized. Beneath the southern Great Valley, there is no ophiolitic breccia, the crust may be up to 10 - 12 km thick, and the mantle section, if present at all, is serpentinized to such a degree that it cannot be distinguished from Sierran basement or mafic ophiolite members on the basis of velocity or density data. Geochemical, petrological, and paleomagnetic data support suprasubduction zone ophiolite formation at North American paleolatitudes, and geological data and geophysical models are consistent with ophiolite formation by back are spreading behind an east facing are. In the north, this was apparently followed by obduction of back are crust onto older continental basement during the Late Jurassic Nevadan orogeny. In the south, the newly formed intraoceanic are and back are apparently collided with the continental margin during the Nevadan orogeny but were not obducted onto it. Instead, the are and back are "docked" with the continental margin leaving the are itself to become the basement to the Great Valley basin. Cretaceous Sierran magmatism then intruded plutons beneath the docked ophiolite and mafic are. Irrespective of the detailed accretionary history, our cross sections show a rapid pulse of continental growth by ophiolite accretion of more than 500 km(3) km(-1) in less than 10 Myr.
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页码:558 / 570
页数:15
相关论文
共 99 条
[1]  
[Anonymous], 1982, GEOL SOC SPEC PUB, DOI DOI 10.1144/GSL.SP.1982.010.01.31
[2]  
Anonymous, 1972, GEOTIMES, V17, P24
[3]  
[Anonymous], GEOTECTONIC DEV CALI
[4]  
Atwater T., 1970, GEOL SOC AM BULL, V181, P3513, DOI [DOI 10.1130/0016-7606(1970)81[3513:IOPTFT]2.0.CO
[5]  
2, 10.1130/0016-7606, DOI 10.1130/0016-7606]
[6]  
BAILEY EH, 1969, GEOTECTONICS, V3, P148
[7]  
BAILEY EH, 1964, B CALIF DIV MINES GE, V183
[8]  
BAILEY EH, 1970, US GEOLOGICAL SURV C, V700, P70
[9]  
BATEMAN PC, 1981, GEOTECTONIC DEV CALI, V1, P71
[10]  
Blake Jr MC., 1974, SOC ECON PALEONTOLOG, P345, DOI 10.2110/pec.74.19