Pseudotachylyte Alteration and the Rapid Fade of Earthquake Scars From the Geological Record
Pseudotachylyte Alteration and the Rapid Fade of Earthquake Scars From the Geological Record
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DOI：
10.1029/2020gl090020
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发表时间：
2020-11-28
影响因子：
5.2
通讯作者：
Di Toro, G.
中科院分区：
文献类型：
--
作者：
Fondriest, M.;Mecklenburgh, J.;Di Toro, G.
构造伪岩是地震时在断层上产生的凝固的摩擦熔体，是地震滑动事件的有力标志。尽管如此，伪岩显然是不常见的断层岩，因为它们要么很少生产，要么很容易从地质记录中消失。为了解决这一难题，在实验室中对固体岩石样品在地震滑动速率下滑动产生的新鲜伪水杨酸进行了长时间（18-35天）的热液蚀变试验。经过所有的测试，假木酸酯被严重改变与基质的溶解和新形成的粘土团聚体。蚀变后的产物与自然蚀变的伪石及其伴生的超粗碎岩（即在没有熔化的情况下受压裂影响的断层岩石）非常相似，表明在热液存在的情况下，原始伪石微结构的保存潜力非常短，几天到几个月。因此，伪岩在地质记录中的代表性可能明显不足，地震期间断层上的摩擦融化可能比一般认为的更常见。
Tectonic pseudotachylytes are solidified frictional melts produced on faults during earthquakes and are robust markers of seismic slip events. Nonetheless, pseudotachylytes are apparently uncommon fault rocks, because they are either rarely produced or are easily lost from the geological record. To solve this conundrum, long-lasting (18-35 days) hydrothermal alteration tests were performed on fresh pseudotachylytes produced by sliding solid rock samples at seismic slip rates in the laboratory. After all tests, the pseudotachylytes were heavily altered with dissolution of the matrix and neo-formation of clay aggregates. Post-alteration products closely resemble natural altered pseudotachylytes and associated ultracataclasites (i.e., fault rocks affected by fracturing in the absence of melting), demonstrating that the preservation potential of original pseudotachylyte microstructures is very short, days to months, in the presence of hydrothermal fluids. As a consequence, pseudotachylytes might be significantly underrepresented in the geological record, and on-fault frictional melting during earthquakes is likely to occur more commonly than generally believed.