کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4694136 | 1636897 | 2009 | 11 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
P- and S-wave velocities of the lowermost crustal rocks from the Kohistan arc: Implications for seismic Moho discontinuity attributed to abundant garnet
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موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: P- and S-wave velocities of the lowermost crustal rocks from the Kohistan arc: Implications for seismic Moho discontinuity attributed to abundant garnet P- and S-wave velocities of the lowermost crustal rocks from the Kohistan arc: Implications for seismic Moho discontinuity attributed to abundant garnet](/preview/png/4694136.png)
چکیده انگلیسی
P- (Vp) and S-wave (Vs) velocities of garnet-free (two-pyroxene granulite) and garnet-bearing (garnet granulite and garnet pyroxenite) lowermost crustal rocks collected from the Kohistan arc, northern Pakistan, were measured at 0.1-1.0 GPa and 25-400 °C. Garnet granulite had higher Vp (+ 0.31 km/s) and Vs (+ 0.27 km/s) than two-pyroxene granulite. Although Vp and Vs increased with increasing volume percent of garnet, plagioclase-free garnet pyroxenite showed significantly higher Vp and Vs than plagioclase-rich garnet granulite mainly due to the low Vp and Vs of plagioclase. In contrast, we observed two quasi-linear relationships between Vp (Vs) and SiO2 content for the garnet-bearing and garnet-free rocks. The garnet-bearing rocks had relatively higher Vp and Vs and stronger SiO2 dependences than the garnet-free rocks. The stronger SiO2 dependences of Vp and Vs in the garnet-bearing rocks suggest that the garnet formation in mafic to ultramafic rocks (e.g., pyroxenite and hornblendite), having relatively lower SiO2, leads to more pronounced increases in Vp and Vs than that of relatively felsic rocks (e.g., felsic-to-mafic granulite). Indeed, the Vp and Vs of the garnet pyroxenite were significantly higher than those of garnet granulite but comparable to those of dunite. The significantly high Vp and Vs of the garnet pyroxenite yielded high reflection coefficients between the garnet granulite and garnet pyroxenite of up to 0.13 for P-waves and 0.14 for S-waves, comparable to values expected for Moho reflection. Thus the lithological boundary between plagioclase-rich garnet granulite and plagioclase-free garnet pyroxenite in the lowermost crust of the Kohistan arc corresponds to the seismic Moho discontinuity.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tectonophysics - Volume 467, Issues 1â4, 20 March 2009, Pages 44-54
Journal: Tectonophysics - Volume 467, Issues 1â4, 20 March 2009, Pages 44-54
نویسندگان
Yoshio Kono, Masahiro Ishikawa, Yumiko Harigane, Katsuyoshi Michibayashi, Makoto Arima,