Jurnal Internasional Great Basin mantle xenoliths merekam downwelling litosfer aktif di bawah pusat Nevada – Dygert – – Geokimia, Geofisika, Geosystems

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Jurnal Internasional Great Basin mantle xenoliths merekam downwelling litosfer aktif di bawah pusat Nevada – Dygert – – Geokimia, Geofisika, Geosystems

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Removal of the mantle lithosphere by Rayleigh Taylor Taylor instability (R-T) is used to explain the formation of highlands and mountains. Here we report the geochemical and microstructural observations of the mantle xenoliths from the volcanic field of Lunar Crater, central Nevada, which we interpret to directly take the example of R-T instability under Basins and Ranges. Xenolith consists of a series of mylonitic and granular peridotites with a fertile and fire-resistant composition of the main element and trace that shows the origin of the lithosphere. The temperature calculated using several geothermometers is 1200–1300 ° C, in contrast to xenolith from other regions in the Basin and Range (usually ~ 1000 ° C). The high Lunar Crater temperature indicates that xenolith originates from the bottom of the mantle lithosphere. Mylonitic peridotite shows olivine deformation microstructure which is a deformation characteristic in dislocated creep regimes; orthopyroxenes undergoes fragile deformation. The recrystallized grain size (~ 80μm) showed deformed mylonites at ~ 50MPa. Olivine recrystallization shows isochemical deformation which shows ~ 50MPa differential pressure achieved at ~ 1200 ° C, implying a strain rate of 2 × 10 -9 44 × 10 -7 / s, and according to viscosity effective 8.9 × 10 13 to 1.4 × 10 16 Pa · s. The most plausible mechanism for producing such conditions in the deep lithosphere beneath the central Nevada is extreme strain localization in the active deformation of R-T. The most strained samples have relatively low effective viscosity, indicating that strains are specially partitioned into weaker rocks in the deformed lithosphere. This study highlights the importance of strain localization and related attenuation as a mechanism to facilitate instability of the lithosphere RT.

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