کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4681187 1634952 2006 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
The thermal structure of subduction zones constrained by seismic imaging: Implications for slab dehydration and wedge flow
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
The thermal structure of subduction zones constrained by seismic imaging: Implications for slab dehydration and wedge flow
چکیده انگلیسی

Thermal models of subduction zones often base their slab–wedge geometry from seismicity at mantle depths and, consequently, cannot be used to evaluate the relationship between seismicity and structure. Here, high-resolution seismic observations from the recent Broadband Experiment Across the Alaska Range (BEAAR) constrain, in a rare instance, the subducting slab geometry and mantle wedge temperature independent of seismicity. Receiver functions reveal that the subducting crust descends less steeply than the Wadati-Benioff Zone. Attenuation tomography of the mantle wedge reveals a high Q and presumably cold region where the slab is less than 80 km deep. To understand these two observations, we generate thermal models that use the improved wedge geometry from receiver functions and that incorporate temperature- and strain-rate-dependent olivine rheology. These calculations show that seismicity within the subducting crust falls in a narrow belt of pressure–temperature conditions, illuminating an effective Clapeyron slope of 0.1 K/MPa at temperatures of 450–750 °C. These conditions typify the breakdown of high-pressure hydrous minerals such as lawsonite and suggest that a single set of dehydration reactions may trigger intermediate-depth seismicity. The models also require that the upper, cold nose of the mantle wedge be isolated from the main flow in the mantle wedge in order to sustain the cold temperatures inferred from the Q tomography. Possibly, sufficient mechanical decoupling occurs at the top of the downgoing slab along a localized shear zone to 80 km depth, considerably deeper than inferred from thrust zone seismicity.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 241, Issues 3–4, 31 January 2006, Pages 387–397
نویسندگان
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