Oblique-slip tectonics in an active volcanic chain: A case study from the Southern Andes
Oblique-slip tectonics in an active volcanic chain: A case study from the Southern Andes
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活火山链中的斜滑构造：安第斯山脉南部的案例研究
DOI：
10.1016/j.tecto.2019.228221
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发表时间：
2019
期刊：
影响因子：
2.9
通讯作者：
Pablo Iturrieta
中科院分区：
文献类型：
--
作者：
G. Sielfeld;J. Ruz;A. Brogi;J. Cembrano;A. Stanton‐Yonge;P. Pérez;Pablo Iturrieta
南安第斯弧内区的斜滑构造适应了上新世和第四纪板块汇聚所产生的不均匀变形。安第斯横向断裂(即NW向左行断裂)和边缘平行断裂(即NNE向断裂)之间的长期机械作用导致了连通的扭张性断裂破坏带，这有利于上地壳流体运移和侵位的构造条件。我们调查了南安第斯山脉塔塔拉-圣佩德罗-佩拉多火山杂岩的喷发前单元的结构和断层的性质。在这里，斜滑断裂横切中新世褶皱地层和花岗岩类。我们的主要结果表明，第四纪火山作用和相关的地热系统是在北东向构造各向异性的基础上发展起来的，该各向异性是由数百条断层和岩脉在长约9公里、宽约4公里的岩石体积中相互作用所定义的，称为塔塔拉破坏带。该区的变形特征为北东向至WNW向的扭张性斜滑断裂，其两侧有(1)地震活动的南北向(右行)Melado断裂，(2)向东的离散的南北向至北东向的右行展布断裂，(3)向东北方向的左行NW向的LosCóndores断裂，这在本工作中是首次报道。后一条断层代表了一个长期存在的安第斯横向断层的极好例子。此外，我们认为，洛斯孔多雷斯断裂含有块体扭压变形的边缘斜滑成分。我们论证了上新世-第四纪弧内斜向断裂作用是在中新世前晚期挤压构造之后发展起来的，这种斜向断裂作用制约了第四纪地球流体流动、侵位和喷发的渗透通道的几何形状。此外，我们评估了一个离散的火山杂岩的应力场，并提供了关键要素，以更好地了解安第斯横向断裂在南安第斯山脉第四纪弧形火山活动和地热系统的空间组织中的作用。
Oblique-slip tectonics in the intra-arc region of the Southern Andes accommodates heterogeneous deformation derived from plate convergence during the Pliocene and Quaternary. Long-term mechanical interaction between Andean transverse faults (i.e. NW-striking sinistral faults) and margin-parallel faults (i.e. NNE-striking faults) results in linked transtensional fault damage zones that facilitate structural conditions for the migration and emplacement of geofluids in the upper crust. We investigated the architecture of pre-eruptive units and the nature of faulting at the Tatara–San-Pedro–Pellado volcanic complex in the Southern Andes. Here, oblique-slip faulting crosscuts Miocene folded strata and granitoids. Our main results suggest that Quaternary volcanism and an associated geothermal systems developed on top of an ENE-oriented structural anisotropy defined by hundreds of faults and dikes interacting in a ca. 9 km long and 4 km wide rock volume, named the Tatara Damage Zone. Deformation in this domain is characterized by ENE- to WNW-striking transtensional oblique-slip faults flanked by (1) the seismically active NS-striking (dextral) Melado Fault to the west, (2) discrete NS- to ENE-striking dextral splay faults to the east and (3) the sinistral NW-striking Los Cóndores Fault to the north-east, which is reported for the first time in this work. The latter fault represents an excellent example of a long-lived Andean Transverse Fault. Furthermore, we suggest that the Los Cóndores Fault accommodates a margin-oblique slip component of bulk transpressional deformation. We demonstrate that Pliocene–Quaternary intra-arc oblique faulting developed after pre-Late Miocene compressional tectonics, and that this oblique faulting constrains the geometry of permeable pathways for the flow, emplacement, and eruption of quaternary geofluids. Furthermore, we evaluated the stress field for a discrete volcanic complex and provided key elements to better understand the role of Andean Transverse Faults in the spatial organization of Quaternary arc volcanism and geothermal systems in the Southern Andes.