Influence of Deformation and Fluids on Ti Exchange in Natural Quartz
Influence of Deformation and Fluids on Ti Exchange in Natural Quartz
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DOI：
10.1029/2021jb022548
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发表时间：
2021-12-01
影响因子：
3.9
通讯作者：
Kewish, Cameron M.
中科院分区：
文献类型：
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作者：
Bestmann, Michel;Pennacchioni, Giorgio;Kewish, Cameron M.
使用显微结构，光谱和地球化学分析相结合，我们调查如何亚晶粒旋转重结晶和流体迁移影响钛浓度[Ti]在自然变形的石英脉从普里耶克特推覆体（奥阿尔卑斯山单位，东阿尔卑斯山）。这些粗粒石英脉形成于角闪岩相条件下，受到下部绿片岩相变形的不同程度的叠加。在叠加过程中，亚晶旋转重结晶在渐进变形至超糜棱岩阶段占主导地位。初始[Ti]（3.0-4.7 ppm）和阴极发光（CL）签名的静脉晶体在变形过程中减少，主要取决于流体的可用性的微观结构。应变量在重置为较低的[Ti]和相应的较暗CL色度中起次要作用。使用微观结构控制分析，我们发现在重结晶聚集体（0.2-0.6 μ m的[Ti]）中最完全的再平衡是在重结晶聚集体（0.2-0.6 μ m的[Ti]）中。发生在（a）石英碎斑周围的应变阴影中，充当流体汇，以及（B）局部微剪切带中，使流体渗流通道化。[Ti]主要沿着润湿的高角度边界（取向差角>10-15度）观察到复位，沿着干燥的低角度边界观察到部分[Ti]复位（
Using a combination of microstructural, spectroscopic, and geochemical analyses, we investigate how subgrain rotation recrystallization and fluid migration affect Ti concentration [Ti] in naturally deformed quartz veins from the Prijakt Nappe (Austroalpine Unit, Eastern Alps). These coarse-grained quartz veins, that formed at amphibolite facies conditions, were overprinted by lower greenschist facies deformation to different degrees. During the overprint, subgrain rotation recrystallization was dominant during progressive deformation to ultramylonitic stages. The initial [Ti] (3.0-4.7 ppm) and cathodoluminescence (CL) signature of the vein crystals decrease during deformation mainly depending on the availability of fluids across the microstructure. The amount of strain played a subordinate role in resetting to lower [Ti] and corresponding darker CL shades. Using a microstructurally controlled analysis we find that the most complete re-equilibration in recrystallized aggregates ([Ti] of 0.2-0.6 p.m.) occurred (a) in strain shadows around quartz porphyroclasts, acting as fluid sinks, and (b) in localized microshear zones that channelized fluid percolation. [Ti] resetting is mainly observed along wetted high angle boundaries (misorientation angle >10-15 degrees), with partial [Ti] resetting observed along dry low angle boundaries (