Palaeopermeability structure within fault-damage zones: A snap-shot from microfracture analyses in a strike-slip system
Palaeopermeability structure within fault-damage zones: A snap-shot from microfracture analyses in a strike-slip system
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DOI：
10.1016/j.jsg.2015.12.002
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发表时间：
2016-02-01
影响因子：
3.1
通讯作者：
Faulkner, Daniel R.
中科院分区：
文献类型：
--
作者：
Gomila, Rodrigo;Arancibia, Gloria;Faulkner, Daniel R.
了解断层带渗透性及其空间分布可以评估导致热液矿物沉淀的流体迁移。本文以热液充填的微裂隙为基础，揭示了断裂带流体输运特征的条件和分布，反映了“冻结”的瞬时平流热液活动，记录了断裂-裂隙系统的古渗透性条件。我们研究了Jorgillo断层，一个暴露的20公里长，左旋走滑断层，并置侏罗纪辉长岩对属于阿塔卡马断层系统在北方智利的变质。从一个400米长的横断面横跨主断层跟踪的19个定向薄片的微裂缝网络的示踪进行了估计的低应变断层damagezone的水力学性质，邻近高应变断层核心，假设硬币形的微裂缝的恒定半径和孔径内的各向异性断裂系统。辉长岩的古渗透率值为9.1 × 10 ~（-11）~ 3.2 × 10 ~（-13）m ~（2），变质碎屑岩的古渗透率值为5.0 × 10 ~（-10）~ 1.2 × 10 ~（-13）m ~（2），两者均随断层核的方向垂直递减。裂缝孔隙度值范围为40.00%至0.28%。Jorgillo断层充当左侧扩张断层弯曲，在同震活动期间在JF北部产生大规模扩张部位。(C)2016爱思唯尔有限公司版权所有。
Understanding fault zone permeability and its spatial distribution allows the assessment of fluid migration leading to precipitation of hydrothermal minerals. This work is aimed at unraveling the conditions and distribution of fluid transport properties in fault zones based on hydrothermally filled microfractures, which reflect the "frozen-in" instantaneous advective hydrothermal activity and record palaeopermeability conditions of the fault-fracture system. We studied the Jorgillo Fault, an exposed 20 km long, left-lateral strike-slip fault, which juxtaposes Jurassic gabbro against metadiorite belonging to the Atacama Fault System in northern Chile. Tracings of microfracture networks of 19 oriented thin sections from a 400 m long transect across the main fault trace was carried out to estimate the hydraulic properties of the low-strain fault damagezone, adjacent to the high-strain fault core, by assuming penny shaped microfractures of constant radius and aperture within an anisotropic fracture system. Palaeopermeability values of 9.1*10-11 to 3.2*10(-13) m(2) in the gabbro and of 5.0*10(-10) to 1.2*10(-13) m(2) in the metadiorite were determined, both decreasing perpendicularly away from the fault core. Fracture porosity values range from 40.00% to 0.28%. The Jorgillo Fault has acted as a left-lateral dilational fault bend, generating large-scale dilation sites north of the JF during co-seismic activity. (C) 2016 Elsevier Ltd. All rights reserved.