Neogene Retroarc Foreland Basin Evolution, Sediment Provenance, and Magmatism in Response to Flat Slab Subduction, Western Argentina
Neogene Retroarc Foreland Basin Evolution, Sediment Provenance, and Magmatism in Response to Flat Slab Subduction, Western Argentina
复制标题
阿根廷西部新近纪弧后前陆盆地演化、沉积物源及岩浆活动对平板俯冲的响应
DOI：
10.1029/2019tc005958
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发表时间：
2020-07-01
期刊：
影响因子：
4.2
通讯作者：
Alvarado, Patricia
中科院分区：
文献类型：
--
作者：
Capaldi, Tomas N.;Horton, Brian K.;Alvarado, Patricia
了解平板俯冲对造山、弧岩浆作用和盆地演化的影响是汇聚边缘构造学的基础，对地球动力学、岩浆和地表过程之间的潜在反馈具有影响。阿根廷中安第斯山脉南部（南纬31度）新生代沉积和岩浆作用的新地层学和地质年代学约束揭示了火山活动、前陆/腹地盆地发育、沉积物积累和物源的变化，因为弧后区域在板片扁平化过程中被结构划分。弧后盆地系统西部（卡林加斯塔盆地）、中部（塔拉卡斯托和阿尔巴拉辛盆地）和东部（贝尔梅霍前陆盆地）的碎屑锆石 U-Pb 年龄分布保留了多个构造区的同沉积火山作用和造山带揭顶作用。主山脉在 24-17 Ma 的初始缩短相关折返是通过带有来自安第斯岩浆弧的渐新世-始新世锆石的远端风成沉积物的积累记录的。卡林加斯塔盆地在大约 17-11 Ma 期间记录了前科迪勒拉的火山活动和基底缩短，其特征是河流到冲积扇沉积物向上粗化，其持续的锆石 U-Pb 年龄成分与腹地普遍存在的二叠纪-三叠纪基岩相匹配。 11 Ma 时火山活动向东向内侧扫掠了 450 公里，与平板俯冲的开始同时发生，随后 Precordillera 褶皱逆冲带出现薄皮缩短，挖出了楔形顶部沉积物，并导致弯曲沉降向克拉通（向东）推进到 Bermejo 前陆盆地。该前陆盆地在结构上被划分，因为潘皮纳斯山脉的基底隆起将河流巨型扇沉积物路径网络转变为由邻近基底块供给的较小的孤立冲积扇系统。
Understanding the effects of flat slab subduction on mountain building, arc magmatism, and basin evolution is fundamental to convergent-margin tectonics, with implications for potential feedbacks among geodynamic, magmatic, and surface processes. New stratigraphic and geochronological constraints on Cenozoic sedimentation and magmatism in the southern Central Andes of Argentina (31 degrees S) reveal shifts in volcanism, foreland/hinterland basin development, sediment accumulation, and provenance as the retroarc region was structurally partitioned during slab flattening. Detrital zircon U-Pb age distributions from the western (Calingasta basin), central (Talacasto and Albarracin basins), and eastern (Bermejo foreland basin) segments of the retroarc basin system preserve syndepositional volcanism and orogenic unroofing of multiple tectonic provinces. Initial shortening-related exhumation of the Principal Cordillera at 24-17 Ma was recorded by the accumulation of distal eolian deposits bearing Oligocene-Eocene zircons from the Andean magmatic arc. The Calingasta basin chronicled volcanism and basement shortening in the Frontal Cordillera at similar to 17-11 Ma, as marked by an upward coarsening succession of fluvial to alluvial fan deposits with a sustained zircon U-Pb age component that matches pervasive Permian-Triassic bedrock in the hinterland. An similar to 450 km eastward inboard sweep of volcanism at 11 Ma coincided with the inception of flat slab subduction, and subsequent thin-skinned shortening in the Precordillera fold-thrust belt that exhumed wedge-top deposits and induced cratonward (eastward) advance of flexural subsidence into the Bermejo foreland basin. This foreland basin was structurally partitioned as basement uplifts of the Sierras Pampeanas transformed a fluvial megafan sediment routing network into smaller isolated alluvial fan systems fed by adjacent basement blocks.