Propagation of seismic slip from brittle to ductile crust: Evidence from pseudotachylyte of the Woodroffe thrust, central Australia
Propagation of seismic slip from brittle to ductile crust: Evidence from pseudotachylyte of the Woodroffe thrust, central Australia
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DOI：
10.1016/j.tecto.2004.10.016
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发表时间：
2005-06
期刊：
影响因子：
2.9
通讯作者：
A. Lin;T. Maruyama;Stallard Aaron;K. Michibayashi;A. Camacho;Ken‐ichi Kano
中科院分区：
文献类型：
--
作者：
A. Lin;T. Maruyama;Stallard Aaron;K. Michibayashi;A. Camacho;Ken‐ichi Kano
澳大利亚中部的Woodroffe逆冲断层是一个宽大于1.5 km的糜棱岩化剪切带，以大量mm至cm级的假玄武玻璃岩脉为标志。假玄武玻璃显示典型的熔融起源的功能，包括圆形和海湾碎屑，球晶和枝晶微晶，细粒度矩阵内的流动结构。三种类型的假玄武玻璃的变形结构的基础上，静脉形态，和主岩岩性：碎裂岩相关（C-Pt），糜棱岩相关（M-Pt），和超糜棱岩相关（Um-Pt）。M-Pt和Um-Pt脉侵入糜棱岩和超糜棱岩中，并被随后的糜棱岩化叠加。这些pseudotachylytes包含一个内部叶理所定义的扁平碎斑岩和细粒脉基质的分层，叶理一般是平行于周围的糜棱岩和超糜棱岩叶理定向。这些意见限制的时间和环境的M-Pt和Um-Pt假玄武玻璃形成的变形和糜棱岩化的韧性地壳制度内的一个漫长的时期。M-Pt和Um-Pt脉，以及主机糜棱岩，叠加的碎裂和多代的后期C-Pt脉，产生于脆性为主的制度，在隆起和折返的剪切带的上地壳。大量的C-Pt，M-Pt和Um-Pt脉的多代共存表明，假玄武玻璃岩脉代表了大量的大地震和伴随的地震滑动在一个延长的地震活动期的Woodroffe逆冲断层。假玄武玻璃的时间和分布表明，地震的核在底部的脆性为主的孕震带和传播向下通过脆-韧性过渡到韧性为主的地壳制度。
The Woodroffe thrust, central Australia, is a >1.5-km-wide mylonitized shear zone marked by large volumes of mm- to cm-scale pseudotachylyte veins. The pseudotachylytes display typical melt-origin features, including rounded and embayed clasts, spherulitic and dentritic microlites, and flow structures within a fine-grained matrix. Three types of pseudotachylyte are identified on the basis of deformation texture, vein morphology, and host-rock lithology: cataclasite-related (C-Pt), mylonite-related (M-Pt), and ultramylonite-related (Um-Pt). The M-Pt and Um-Pt veins intrude into mylonite and ultramylonite and are themselves overprinted by subsequent mylonitization. These pseudotachylytes contain an internal foliation defined by flattened porphyroclasts and layering of the fine-grained vein matrix, and the foliation is generally oriented parallel to foliation in the surrounding mylonite and ultramylonite. These observations constrain the timing and environment of M-Pt and Um-Pt pseudotachylyte formation to a protracted period of deformation and mylonitization within the ductile regime of the crust. The M-Pt and Um-Pt veins, as well as the host mylonite, are overprinted by cataclasis and multiple generations of late-stage C-Pt veins that were generated in the brittle-dominated regime of the upper crust during uplift and exhumation of the shear zone. The coexistence of multiple generations of voluminous C-Pt, M-Pt, and Um-Pt veins indicates that the pseudotachylyte veins represent a large number of large earthquakes and accompanying seismic slip over an extended period of seismicity on the Woodroffe thrust. The timing and distribution of pseudotachylyte indicate that the earthquakes nucleated at the base of the brittle-dominated seismogenic zone and propagated down through the brittle–ductile transition into the ductile-dominated regime of the crust.