Transient creep occurs during geodynamic processes that impose stress changes on rocks at high temperatures. The transient is manifested as evolution in the viscosity of the rocks until steady‐state flow is achieved. Although several phenomenological models of transient creep in rocks have been proposed, the dominant microphysical processes that control such behavior remain poorly constrained. To identify the intragranular processes that contribute to transient creep of olivine, we performed stress‐reduction tests on single crystals of olivine at temperatures of 1,250°C–1,300°C. In these experiments, samples undergo time‐dependent reverse strain after the stress reduction. The magnitude of reverse strain is ∼10⁻³ and increases with increasing magnitude of the stress reduction. High‐angular resolution electron backscatter diffraction analyses of deformed material reveal lattice curvature and heterogeneous stresses associated with the dominant slip system. The mechanical and microstructural data are consistent with transient creep of the single crystals arising from accumulation and release of backstresses among dislocations. These results allow the dislocation‐glide component of creep at high temperatures to be isolated, and we use these data to calibrate a flow law for olivine to describe the glide component of creep over a wide temperature range. We argue that this flow law can be used to estimate both transient creep and steady‐state viscosities of olivine, with the transient evolution controlled by the evolution of the backstress. This model is able to predict variability in the style of transient (normal vs. inverse) and the load‐relaxation response observed in previous work.

中文翻译：

---

橄榄石的位错蠕变：背压演变控制高温下的瞬态蠕变

瞬态蠕变发生在地球动力学过程中，该过程在高温下将应力施加在岩石上。在达到稳态流动之前，瞬态表现为岩石粘度的演变。尽管已经提出了岩石瞬态蠕变的几种现象学模型，但是控制这种行为的主要微观物理过程仍然受到约束。为了确定导致橄榄石瞬态蠕变的晶粒内过程，我们在1,250°C–1,300°C的温度下对橄榄石单晶进行了应力降低测试。在这些实验中，样品在应力降低后会经历与时间有关的反向应变。反向应变的大小约为10 ^-3并且随着应力降低幅度的增加而增加。变形材料的高角度分辨率电子背散射衍射分析揭示了晶格曲率和与主要滑动系统相关的非均质应力。力学和微观结构数据与位错之间背应力的积累和释放引起的单晶瞬态蠕变一致。这些结果可以隔离高温下蠕变的位错-滑移分量，并且我们使用这些数据来校准橄榄石的流动定律，以描述在宽温度范围内蠕变的滑移分量。我们认为，该流动定律可用于估算橄榄石的瞬态蠕变和稳态粘度，其瞬态演化受背应力的演化控制。