Shear deformation of a solid-fluid, two-phase material induces a fluid segregation process that produces fluid-enriched bands and fluid-depleted regions, and a crystallographic preferred orientation (CPO) characterized by girdles of [100] and [001] axes sub-parallel to the shear plane and a cluster of [010] axes sub-normal to the shear plane, namely the AG-type fabric. Based on experiments of two-phase aggregates of olivine + basalt, a two-phase flow theory and a CPO formation model were established to explain these microstructures. Here, we investigate the microstructure in a two-phase aggregate with supercritical CO₂ as the fluid phase and examine the theory and model, to evaluate differences in rheological properties due to the presence of CO₂ or basaltic melt. We conducted high-temperature and high-pressure shear deformed experiments at 1 GPa and 1100 °C in a Griggs-type apparatus on samples made of olivine + dolomite, which decomposed into carbonate melt and CO₂ at experimental conditions. After deformation, CO₂ segregation and an AG-type fabric were observed in these CO₂-bearing samples, similar to basaltic melt-bearing samples. An SPO-induce CPO model was used to explain to the formation of the fabric. Our results suggest that the influences of CO₂ as a fluid phase on the microstructure of a two-phase olivine aggregate is similar to that of basaltic melt and can be explained by the CPO formation model for the solid-fluid system.

中文翻译：

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CO2对剪切的橄榄石骨料微观结构的影响

固相两相材料的剪切变形引起流体分离过程，该过程产生富流体带和贫流体区域，以及以[100]和[001]轴的腰带为特征的晶体学优选取向（CPO） -平行于剪切平面并垂直于剪​​切平面的[010]轴簇，即AG型织物。基于橄榄石+玄武岩两相聚集体的实验，建立了两相流理论和CPO形成模型来解释这些微观结构。在这里，我们研究了以超临界CO ₂为流体的两相聚集体的微观结构，并研究了理论和模型，以评估由于存在CO ₂而引起的流变性质的差异。或玄武岩融化。我们在1 GPa和1100°C的Griggs型仪器中对由橄榄石+白云石制成的样品进行了高温高压剪切变形实验，这些样品在实验条件下分解为碳酸盐熔体和CO ₂。变形后，在这些含CO _2的样品中观察到了CO ₂偏析和一种AG型织物，类似于玄武岩含熔体的样品。使用SPO诱导CPO模型来解释织物的形成。我们的结果表明，CO ₂作为液相对两相橄榄石聚集体微观结构的影响与玄武质熔体的影响相似，并且可以通过固-液体系的CPO形成模型来解释。