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Paleomagnetic and Ar-40/Ar-39 geochronologic data bearing on the structural evolution of the Silver Peak extensional complex, west-central Nevada | |
Petronis, MS; Geissman, JW; Oldow, JS; McIntosh, WC | |
通讯作者 | Petronis, MS |
来源期刊 | GEOLOGICAL SOCIETY OF AMERICA BULLETIN |
ISSN | 0016-7606 |
出版年 | 2002 |
卷号 | 114期号:9页码:1108-1130 |
英文摘要 | The Silver Peak extensional complex, located in the Silver Peak Range of west-central Nevada, is a displacement-transfer system linking the Furnace Creek-Fish Lake Valley fault system and transcurrent faults of the central Walker Lane. Late Neogene, northwest-directed motion of an upper plate, composed of lower Paleozoic sedimentary rocks and late Tertiary volcanic and volcaniclastic strata, exhumed a lower-plate assemblage of metamorphic tectonites with Proterozoic and Mesozoic protoliths. Paleomagnetic investigation of Miocene-Pliocene pyroclastic and sedimentary rocks of the upper plate and Miocene mafic dikes in the lower plate reveals modest horizontal-axis tilting (northwest-side-up) and vertical-axis rotation (clockwise) within the extensional complex. Eight to ten samples from each of 123 sites were demagnetized; 95 sites yielded interpretable results. Dual-polarity results from one population of mafic dikes in the lower-plate assemblage indicate moderate, northwest-side-up tilting (declination D = 329degrees, inclination I = 37degrees, alpha(95) = 4.3degrees, number N = 30 sites; in situ) (alpha(95) = the confidence limit for the calculated mean direction expressed as an angular radius from the calculated mean direction). Some dikes yield exclusively normal-polarity results that are interpreted to indicate modest clockwise vertical-axis rotation (D = 021degrees, I = 57degrees, alpha(95) = 4.3degrees, N = 19 sites; in situ) concurrent with uplift of the lower-plate rocks, and nine sites yield magnetization directions that are north-directed with positive inclinations of moderate steepness, similar to an expected Miocene field. Late Miocene pyroclastic rocks in the upper plate yield normal-polarity magnetizations suggestive of moderate, clockwise, vertical-axis rotation (D = 032degrees, I = 53degrees, alpha(95) = 8.8degrees, N = 10 sites). The apparent clockwise rotation is unlikely to result from incomplete sampling of the geomagnetic field, because the overall dispersion of the VGP (virtual geomagnetic pole) positions is high for the latitude of the site location. Middle Miocene sedimentary rocks probably were remagnetized shortly after deposition. Of eight Ar-40/Ar-39 determinations from mafic dikes in the lower plate, five groundmass concentrates yield saddle-shaped age spectra, and one separate provided a plateau date of low confidence. Isochron analysis reveals that all six groundmass concentrates contain excess Ar. If rapid cooling and Ar retention below similar to250 degreesC are assumed, the preferred age estimate for mafic intrusions is provided by isochron dates and suggests emplacement between 12 and 10.5 Ma. The Ar-40/Ar-39 age-spectrum data are consistent with existing fission-track cooling and K-Ar isotopic age information from lower-plate granitic rocks and indicate rapid cooling of the lower-plate assemblage from well above 300 degreesC to 100 degreesC between 13 and 5 Ma. Rapid cooling may explain the overall distribution of paleomagnetic results from lower-plate intrusions such that the earliest acquired magnetizations reflect both northwest-sideup tilt and clockwise rotation and the younger magnetizations reflect northwest-sideup tilt. Overall, the paleomagnetic data from the Silver Peak extensional complex are interpreted to suggest that vertical-axis rotation of crustal-scale blocks, associated with displacement transfer in the central Walker Lane, may play an integral part in accommodating strain within a continental displacement-transfer system. |
英文关键词 | ash-flow tuffs extensional tectonics geochronology metamorphic core complexes paleomagnetism Walker Lane |
类型 | Article |
语种 | 英语 |
国家 | USA |
收录类别 | SCI-E |
WOS记录号 | WOS:000177938100004 |
WOS关键词 | DIXIE VALLEY REGION ; WALKER LANE BELT ; STRIKE-SLIP ; EASTERN CALIFORNIA ; THERMAL HISTORY ; RANGE PROVINCE ; UNITED-STATES ; MOJAVE-DESERT ; AGE-SPECTRA ; SHEAR ZONE |
WOS类目 | Geosciences, Multidisciplinary |
WOS研究方向 | Geology |
资源类型 | 期刊论文 |
条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/142682 |
作者单位 | (1)Univ New Mexico, Dept Earth & Planetary Sci, Albuquerque, NM 87131 USA;(2)Univ Idaho, Dept Geol Sci, Moscow, ID 83844 USA;(3)New Mexico Inst Min & Technol, New Mexico Geochronol Res Lab, Socorro, NM 87801 USA |
推荐引用方式 GB/T 7714 | Petronis, MS,Geissman, JW,Oldow, JS,et al. Paleomagnetic and Ar-40/Ar-39 geochronologic data bearing on the structural evolution of the Silver Peak extensional complex, west-central Nevada[J],2002,114(9):1108-1130. |
APA | Petronis, MS,Geissman, JW,Oldow, JS,&McIntosh, WC.(2002).Paleomagnetic and Ar-40/Ar-39 geochronologic data bearing on the structural evolution of the Silver Peak extensional complex, west-central Nevada.GEOLOGICAL SOCIETY OF AMERICA BULLETIN,114(9),1108-1130. |
MLA | Petronis, MS,et al."Paleomagnetic and Ar-40/Ar-39 geochronologic data bearing on the structural evolution of the Silver Peak extensional complex, west-central Nevada".GEOLOGICAL SOCIETY OF AMERICA BULLETIN 114.9(2002):1108-1130. |
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