The impact of fluid-rock interaction during deformation is difficult to characterize at the regional scale because of the lack of continuous outcrops to provide textural evidence and meaningful spatial comparisons. Herein we introduce the use of bench top μXRF data as a cost-effective means to quantify chemical and deformation gradients within representative specimens from across the strain gradient associated with the Pocologan Kennebecasis shear zone (PKSZ) in the Canadian Appalachians. Within the Pocologan Harbour granitoid belt, the main foliation is defined by three distinct mineral assemblages characterized by: (A) zoisite, no muscovite; (B) zoisite and muscovite; (C) muscovite and potassium feldspar. We first test whether these mineral assemblages are indicative of primary lithological variation or hydrothermal alteration using major and trace element geochemistry. Then, we test if these mineral assemblages impact the fabric anisotropy using quantitative image analysis of thin section phase maps derived using a benchtop μXRF. We found that whole rock compositions of specimens with an assemblage characterized by potassium feldspar and muscovite show significant element mobility compared to the least altered specimens and that the thin section phase map anisotropy best defines the deformation gradient of the PKSZ regardless of the metasomatic assemblage. This deformation gradient is mimicked by the shape anisotropy of quartz, plagioclase, biotite and muscovite aggregates. Within the most altered specimens, sericite alteration of plagioclase increased the mineral aggregate anisotropy through strain localization in shear bands while the crystallization of potassium feldspar at the expense of plagioclase of muscovite, plagioclase and quartz decreased the mineral aggregate anisotropy which indicates an overall strengthening of the shear zone. Moreover, the combination of grain-size reduction mechanisms and -deformation metasomatism in the high strain portion of the shear zone triggered a change of deformation mechanism from plastic deformation to diffusion creep.

中文翻译：

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定义剪切带变形和蚀变梯度：Pocologan Kennebecasis 剪切带，加拿大阿巴拉契亚山脉


由于缺乏连续的露头来提供纹理证据和有意义的空间比较，变形过程中流体-岩石相互作用的影响很难在区域尺度上表征。在此，我们介绍了使用台式 μXRF 数据作为一种经济有效的方法来量化与加拿大阿巴拉契亚山脉 Pocologan Kennebecasis 剪切带 (PKSZ) 相关的应变梯度中代表性样本内的化学和变形梯度。在波科洛根港花岗岩带内，主要叶理由三种不同的矿物组合定义，其特征为： (A) 黝帘石，无白云母； (B) 黝帘石和白云母； (C)白云母和钾长石。我们首先使用主量和微量元素地球化学测试这些矿物组合是否表明原生岩性变化或热液蚀变。然后，我们使用台式 μXRF 得出的薄片相图的定量图像分析来测试这些矿物组合是否影响织物的各向异性。我们发现，与最少改变的样本相比，具有以钾长石和白云母为特征的组合的样本的整个岩石成分显示出显着的元素迁移率，并且无论交代组合如何，薄片相图各向异性最好地定义了 PKSZ 的变形梯度。这种变形梯度由石英、斜长石、黑云母和白云母聚集体的形状各向异性来模拟。 在蚀变最大的样本中，斜长石的绢云母蚀变通过剪切带中的应变局部化增加了矿物聚集体的各向异性，而钾长石的结晶以牺牲白云母、斜长石和石英的斜长石为代价，降低了矿物聚集体的各向异性，这表明矿物聚集体的各向异性总体增强。剪切带。此外，剪切带高应变部分的晶粒尺寸减小机制和变形交代作用的结合引发了变形机制从塑性变形到扩散蠕变的转变。