Large-scale pseudotachylytes and fluidized cataclasites from an ancient subduction thrust fault
Large-scale pseudotachylytes and fluidized cataclasites from an ancient subduction thrust fault
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来自古代俯冲逆冲断层的大型假速晶石和流化碎裂岩
DOI：
10.1130/g21856.1
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发表时间：
2005
期刊：
影响因子：
5.8
通讯作者：
Alexander W. McKeirnan
中科院分区：
文献类型：
--
作者：
C. Rowe;J. Casey Moore;F. Meneghini;Alexander W. McKeirnan
在科迪亚克增生杂岩，科迪亚克岛，阿拉斯加，假玄武玻璃发生在黑色，局部玻璃质超细颗粒断层岩。显微镜观察表明，pseudotachylytes是由玻璃，囊泡，杏仁，微晶和流动结构，表明摩擦熔体。假玄武玻璃与碎裂岩呈递变关系，显示出露规模的注入和韧性变形构造。碎裂岩是韧性的移动的（即，流体化）的同时形成和侵位的假玄武玻璃熔体。假玄武玻璃岩的时代晚于相关的剪切带混杂岩的地层破裂组构，并显示出类似的逆冲推覆方向，并经历了有限的后续变形。我们解释的地层破裂，作为俯冲板块和pseudotachylyte的发展作为这个逆冲面的最后活动的下冲所造成的。假玄武玻璃和碎裂岩之间的递变接触表明，碎裂岩也形成为地震产物，可能代表古地震破裂带，可能是非常大的地震，伴随或不伴随假玄武玻璃。假玄武质体积庞大，许多在空间上与生成面不相连。这种风格与其他环境中描述的假玄武玻璃不同，这可能解释了俯冲-逆冲假玄武玻璃的罕见记录。
In the Kodiak accretionary complex, Kodiak Island, Alaska, pseudotachylyte occurs in black, locally vitreous ultrafine-grained fault rock. Microscopic observations show that the pseudotachylytes are composed of glass, with vesicles, amygdules, microlites, and flow structures, indicating a frictional melt. The pseudotachylyte is gradational to cataclasite and shows outcrop-scale injection and ductile deformation structures. The cataclasite was ductily mobile (i.e., fluidized) simultaneous with the formation and emplacement of pseudotachylyte melt. The pseudotachylytic rocks postdate the stratal disruption fabric of associated shear-zone melanges and show similar direction of thrust transport, and have undergone limited subsequent deformation. We interpret the stratal disruption as resulting from underthrusting of the subducting plate and pseudotachylyte development as the final activity of this thrust surface. The gradational contacts between pseudotachylyte and cataclasite demonstrate that the cataclasite also formed as a seismic product and may represent paleoseismic rupture zones, possibly of very great earthquakes, with or without accompanying pseudotachylytes. The pseudotachylytes are voluminous, and many are spatially disconnected from generation surfaces. This style is distinct from pseudotachylytes described in other environments, and this may explain the rarity of documented examples of subduction-thrust pseudotachylyte.