Syntectonic microstructural evolution is a well‐known phenomenon in the mantle and lower crust associated with two main processes: grain size reduction through dynamic recrystallization and development of crystallographic preferred orientation (CPO). However, the effects of annealing via static recrystallization on grain size and CPO have been largely overlooked. We investigated mantle annealing by analyzing a suite of kimberlite‐hosted garnet peridotite xenoliths from the Wyoming Craton. We focus on five xenoliths that show microstructures reflecting different degrees of recrystallization, with annealed grains characterized by distinctive faceted boundaries crosscutting surrounding, nonfaceted matrix grains. These textures are indicative of discontinuous static recrystallization (DiSRX). Electron backscatter diffraction analysis further demonstrates a ∼10°–20° misorientation between DiSRXed grains and the matrix grains, resulting in an overall weaker CPO. These characteristics are remarkably similar to microstructures observed in samples that were annealed after deformation in the laboratory. Measurements of the thermal conditions and water contents associated with the last equilibration of the xenoliths suggests that high homologous temperatures (T/T_m > 0.9) are necessary to induce DiSRX. We postulate that annealing through DiSRX occurs under high temperatures after a short episode of intense deformation (years to hundreds of years) with timescales for annealing estimated as weeks to years, significantly slower than the timescale of hours expected for a kimberlitic magma ascent. We conclude that microstructural transformation due to DiSRX will occur during transient heating events associated with mantle upwelling, plumes, and lithospheric thinning.

中文翻译：

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上地幔变形后退火引起的微结构位移

在地幔和下地壳中，构造的微观结构演变是一种众所周知的现象，与以下两个主要过程相关：通过动态再结晶来减小晶粒尺寸以及发展晶体学择优取向（CPO）。但是，通过静态再结晶进行退火对晶粒尺寸和CPO的影响已被大大忽略。我们通过分析一套来自怀俄明州克雷顿的金伯利岩型石榴石橄榄岩橄榄岩异岩，研究了地幔退火。我们重点研究五种异质岩，它们显示出反映不同程度再结晶的微结构，退火晶粒的特征是独特的刻面边界横切周围的，非刻面的基体晶粒。这些纹理指示不连续的静态重结晶（DiSRX）。电子背散射衍射分析进一步表明，DiSRXed晶粒与基体晶粒之间存在约10°–20°的取向错误，从而导致总体CPO较弱。这些特征与在实验室变形后退火的样品中观察到的微观结构非常相似。与异物最后平衡有关的热条件和水含量的测量表明，较高的同源温度（T / T _m  > 0.9）是诱导DiSRX所必需的。我们假设通过DiSRX进行的退火是在短暂的剧烈变形（数年至数百年）后于高温下发生的，退火的时间尺度估计为数周至数年，大大低于金伯利岩岩浆上升预期的小时数。我们得出的结论是，由于DiSRX引起的微观结构转变将在与地幔上升，羽状流和岩石圈变薄有关的瞬态加热事件中发生。