Experimental evidence for water weakening of quartzite by microcracking plus solution–precipitation creep
Experimental evidence for water weakening of quartzite by microcracking plus solution–precipitation creep
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微裂加溶解-沉淀蠕变对石英岩水弱化的实验证据
DOI：
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发表时间：
1991
影响因子：
2.7
通讯作者：
C. Spiers
中科院分区：
文献类型：
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作者：
S. W. Brok;C. Spiers
在温度为1073 K、围压为1.2±0.1GPa、应变速率为10−5、10−6和10−7 s−1以及添加0.4 wt%的水的条件下，对天然石英岩进行了实验变形。变形后的显微组织表明，在应变速率为10−5 ~ 6 s−1时，晶体塑性变形占主导地位。这从原始晶粒中丰富的变形片层以及这些晶粒表现出（弱）晶体学优选取向的事实中可以看出。新的颗粒不存在或相对较小的体积重要性。相反，在10−7 s−1下变形的样品在轴向排列的穿晶和晶界微裂纹中显示出许多细小的、新的多边形或自面体石英晶粒阵列。这些新团聚体具有丰富的微尺度孔洞、细小的粒间通道和流体包裹体痕迹等特征。裂缝壁上的合成过度生长结构也很普遍。新颗粒的聚集体因此被解释为是由溶液沉淀形成的。此外，垂直于缩短方向的旧晶界显示了溶蚀的证据。旧晶粒几乎没有变形片、亚晶粒或c轴优先取向。因此，在应变速率为10−7 s−1时，微裂纹和固溶-析出蠕变是主要的变形机制。
Natural quartzites have been experimentally deformed at a temperature of 1073 K, a confining pressure of 1.2 ± 0.1GPa, strain rates of 10−5, 10−6 and 10−7 s−1 and in the presence of 0.4 wt% of added water. Microstructures after deformation indicate that at strain rates of 10−5–10−6 s−1 crystal plastic deformation is predominant. This is evident from abundant deformation lamellae in the original grains, and the fact that these grains show a (weak) crystallographic preferred orientation. New grains are absent or of relatively minor volumetric importance. In contrast, samples deformed at 10−7 s−1 show numerous arrays of fine, new polygonal to euhedral quartz grains developed in axially aligned transgranular and grain boundary microcracks. These new-grain aggregates are characterized by abundant microscale voids, fine intergranular channels and fluid inclusion trails. Syntaxial overgrowth structures on crack walls are also widespread. The aggregates of new grains are thus interpreted to have formed by precipitation from solution. In addition, old grain boundaries oriented perpendicular to the shortening direction show evidence for dissolution. The old grains show almost no deformation lamellae, subgrains or c-axis preferred orientation. It therefore appears that at strain rates of 10−7 s−1 microcracking and solution-precipitation creep are the dominant deformation mechanisms.