Structure and evolution of the Lewisian Gairloch shear zone: variable movement directions in a strike-slip regime
Structure and evolution of the Lewisian Gairloch shear zone: variable movement directions in a strike-slip regime
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刘易斯盖尔洛赫剪切带的结构和演化：走滑区域的可变运动方向
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发表时间：
2010
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通讯作者：
R. Park
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作者：
R. Park
盖尔洛克剪切带（GSZ）长期以来被认为是一个右旋走滑剪切带，具有西北倾伏剪切方向。然而，原始应变分析仅适用于该区域的东北三分之一，其余三分之二的结构要复杂得多。6.5km宽的GSZ形成于1.7Ga左右的拉克斯福晚期（D3）变形。它是退变质绿片岩相变质作用下D3褶皱和右旋走滑剪切相互作用的产物，该变质作用是在角闪岩相早期拉克斯福德（D2）变形的强烈变形下进行的。GSZ在走向上分为四个单元：东北剪切带，具有NW倾伏的D3线性组构; Flowerdale带，具有SE倾伏的D2线性组构和低D3应变; Ard带，具有陡峭倾伏的F3褶皱;西南剪切带，具有SE倾伏的D3线理。因此，GSZ由两个高应变D3剪切带的中央低应变带的两侧。虽然始终右旋走滑，D3剪切制度的变化，从东北-在东北剪切带通过亚水平走滑在Ard带西南-在西南剪切带。这种变化可能是由走滑系统的壁的几何形状的变化引起的局部隆起或凹陷引起的。右行剪切水平分量的修正的非常近似的最小估计值为c.9.5 km，净东北向上垂直分量为c.5.5 km。地面安全带和南哈里斯带之间的结构相似性加强了这两个区域是同一结构的一部分的情况。
Synopsis The Gairloch shear zone (GSZ) has long been regarded as a dextral strike-slip shear zone with a northwesterly plunging shear direction. However, the original strain analysis applies only to the northeastern third of the zone and the structure of the remaining two-thirds is considerably more complex. The 6.5 km wide GSZ was formed during late Laxfordian (D3) deformation at c. 1.7 Ga. It was a product of the interaction of D3 folding and dextral strike-slip shear under retrogressive greenschist-facies metamorphism on rocks previously intensely deformed by early Laxfordian (D2) deformation in amphibolite-facies. The GSZ is divided into four units across strike: the Northeastern shear zone with NW-plunging D3 linear fabric; the Flowerdale belt with SE-plunging D2 linear fabric and low D3 strain; the Ard belt with steeply plunging F3 folds; and the Southwestern shear zone, with SE-plunging D3 lineation. Thus the GSZ consists of two high-strain D3 shear zones on either side of a central low-strain belt. Although consistently dextral strike-slip throughout, the D3 shear regime varies from NE-up in the Northeastern shear zone through sub-horizontal strike-slip in the Ard belt to SW-up in the Southwestern shear zone. This variation may have been caused by local uplift or depression induced by variations in geometry of the walls of the strike-slip system. A revised very approximate minimum estimate of the horizontal component of dextral shear is c. 9.5 km with a net NE-up vertical component of c. 5.5 km. Similarities in structure between the GSZ and the South Harris belt strengthen the case for these two zones to have been part of the same structure.