کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4691911 1636762 2014 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Deformation microstructures and magnetite texture development in synthetic shear zones
ترجمه فارسی عنوان
ریزساختارهای تغییر شکل و توسعه بافت مگنتیت در مناطق برش مصنوعی
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی
We present observations of deformation features in magnetite from synthetic magnetite-bearing silicate aggregates deformed between 1000 °C and 1200 °C in transpressional shear experiments with strains of up to 300%. Anisotropy of magnetic susceptibility and shape preferred orientation (SPO) analysis were combined with electron backscatter diffraction (EBSD) to characterize the magnetite deformation fabrics and intragrain microstructures. Crystallographic preferred orientation (CPO) in magnetite is very weak in all deformed samples and does not vary as a function of either temperature or shear strain. Magnetic anisotropy and SPO increase strongly with both strain and deformation temperature and indicate that strain partitioning between magnetite and the plagioclase matrix decreases at higher temperatures. EBSD orientation mapping of individual magnetite particles revealed substantial dispersions in intragrain orientation, analogous to undulose extinction, after deformation at 1000 and 1100 °C, indicating that dislocation creep processes were active in magnetite despite the lack of a well-developed CPO. Geometrical analysis of crystallographic orientation dispersions from grain map data indicates that low-angle grain boundary formation in magnetite could have been accommodated by slip on {110} or {100} planes, but no evidence for dominant slip on the expected {111} planes was found. Evidence for activation of multiple slip systems was seen in some magnetite grains and could be partially responsible for the lack of CPO in magnetite. These results suggest that, at least in polyphase rocks, crystallographic textures in magnetite may be inherently weak or slow to develop and CPO alone is not an adequate indicator of magnetite deformation mechanisms. These results may aid in the interpretation of deformation textures in other spinel-structured phases such as chromite and ringwoodite.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Tectonophysics - Volume 629, 26 August 2014, Pages 211-223
نویسندگان
, ,