Jara José Joaquín, Barra Fernando, Reich Martin, Leisen Mathieu, Romero Rurik, Morata Diego
Departamento de Geología y Centro de Excelencia en Geotermia de los Andes (CEGA), FCFM, Universidad de Chile, Santiago, Chile.
Departamento de Ingeniería de Minería, Pontificia Universidad Católica de Chile, Santiago, Chile.
Nat Commun. 2021 Aug 13;12(1):4930. doi: 10.1038/s41467-021-25232-z.
The subduction of oceanic plates beneath continental lithosphere is responsible for continental growth and recycling of oceanic crust, promoting the formation of Cordilleran arcs. However, the processes that control the evolution of these Cordilleran orogenic belts, particularly during their early stages of formation, have not been fully investigated. Here we use a multi-proxy geochemical approach, based on zircon petrochronology and whole-rock analyses, to assess the early evolution of the Andes, one of the most remarkable continental arcs in the world. Our results show that magmatism in the early Andean Cordillera occurred over a period of ~120 million years with six distinct plutonic episodes between 215 and 94 Ma. Each episode is the result of a complex interplay between mantle, crust, slab and sediment contributions that can be traced using zircon chemistry. Overall, the magmatism evolved in response to changes in the tectonic configuration, from transtensional/extensional conditions (215-145 Ma) to a transtensional regime (138-94 Ma). We conclude that an external (tectonic) forcing model with mantle-derived inputs is responsible for the episodic plutonism in this extensional continental arc. This study highlights the use of zircon petrochronology in assessing the multimillion-year crustal scale evolution of Cordilleran arcs.
大洋板块俯冲到大陆岩石圈之下是大陆生长和洋壳再循环的原因，促进了科迪勒拉弧的形成。然而，控制这些科迪勒拉造山带演化的过程，尤其是在其形成的早期阶段，尚未得到充分研究。在这里，我们采用基于锆石年代学和全岩分析的多指标地球化学方法，来评估安第斯山脉（世界上最显著的大陆弧之一）的早期演化。我们的结果表明，安第斯山脉早期科迪勒拉的岩浆活动持续了约1.2亿年，在2.15亿年至9400万年前之间有六个不同的深成侵入期。每个阶段都是地幔、地壳、板块和沉积物贡献之间复杂相互作用的结果，这些可以通过锆石化学来追踪。总体而言，岩浆活动随着构造格局的变化而演化，从张扭/伸展条件（2.15亿年至1.45亿年前）转变为张扭构造体制（1.38亿年至9400万年前）。我们得出结论，一个具有地幔源输入的外部（构造）强迫模型是造成这个伸展大陆弧间歇性深成侵入作用的原因。这项研究突出了锆石年代学在评估科迪勒拉弧数百万年地壳尺度演化中的应用。
