Abstract The Somun Cura Magmatic Province (SCMP) is a Cenozoic volcanic region comprised by several basaltic fields and large central volcanoes located at the Northern Extra-Andean Patagonia, Argentina. The principal volcanic sequences were erupted between the late Eocene and late Miocene, forming the Meseta de Somun Cura, which covers ~30,000 km2 between 40°30′-43°20′S and 65°50′-69°20′W, involving around 1 to 2 × 103 km3 of mafic lavas, and about half that volume of intermediate to silicic lava-pyroclastic associations. The SCMP developed in a back-arc to intraplate tectonic setting over the North Patagonian Massif (NPM), at the time of two major geodynamic events at the western margin of South America: the consumption of the Aluk and the break-up of the Farallon oceanic plates. The magmatism at the studied area is represented by eight volcanic complexes, the Somun Cura Formation flood basalts, and other units related to minor volcanic fields or polygenetic centres. These sequences share intricate stratigraphic relations, which hinder the evolution of the SCMP. To address this issue, an updated compilation of geochronological determinations for the Meseta de Somun Cura region is provided. Its integrated analysis, together with stratigraphic information, allowed the identification of periods of preferential volcanic emission, after which seven constructional phases between late Eocene and late Miocene are proposed. Within these phases, seven pulses of magmatic activity are interpreted for the volcanic complexes emplaced in this area (~38-37 Ma, ~32.5–31 Ma, ~29.5–28 Ma, ~26-24 Ma, ~21–18.5, ~18-15 Ma and ~10.5 Ma), together with four pulses of effusion of flood basalts, represented by the Somun Cura Formation (~32 Ma, ~27-26 Ma, ~26-25 Ma, and ~21.5 Ma). The superposition and recurrence of the magmatic pulses associated with the volcanic complexes and the Somun Cura Formation argue against the application of a "pre-plateau", "plateau" and "post-plateau" scheme, which is revised. The largest volumes of magma associated with the Somun Cura Formation and the volcanic complexes were extruded during the late Oligocene and the early Miocene, respectively. The area of emplacement of the Somun Cura Formation changed over time, defining a roughly counter-clockwise spatial and temporal pattern, starting from the southwest. The magmatic activity recorded by the volcanic complexes from late Eocene to middle Oligocene seems to have concentrated alternatively along NW-SE and NE-SW corridors, and along a N–S belt to the west during the early Miocene. This systematic organization could be related to the reactivation of previous structures, triggered by the kinematic changes in the convergence vector between the Farallon-Nazca Plates and the South American Plate.

中文翻译：

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阿根廷安第斯山脉北部巴塔哥尼亚北部索姆库拉岩浆省的时空演化

摘要 Somun Cura Magmatic Province (SCMP) 是一个新生代火山区，由位于阿根廷安第斯北部巴塔哥尼亚北部的几个玄武岩田和大型中央火山组成。主要火山层序发生在晚始新世和晚中新世之间，形成了 Meseta de Somun Cura，覆盖范围在 40°30'-43°20'S 和 65°50'-69°20'W 之间约 30,000 平方公里，涉及大约 1 到 2 × 103 平方公里的镁铁质熔岩，以及大约一半体积的中硅质熔岩-火山碎屑组合。在南美洲西部边缘发生两个主要地球动力学事件时，南华早报在北巴塔哥尼亚地块 (NPM) 的弧后至板内构造环境中发育：Aluk 的消耗和 Farallon 的解体大洋板块。研究区的岩浆活动以八个火山复合体、Somun Cura 组洪水玄武岩和其他与次要火山区或多成中心有关的单元为代表。这些层序共享错综复杂的地层关系，阻碍了南华早报的演化。为了解决这个问题，提供了 Meseta de Somun Cura 地区地质年代学测定的更新汇编。其综合分析与地层信息一起，可以确定优先火山喷发的时期，之后提出了晚始新世和晚中新世之间的七个构造阶段。在这些阶段中，解释了该地区火山复合体的七个岩浆活动脉冲（~38-37 Ma，~32.5-31 Ma，~29.5-28 Ma，~26-24 Ma，~21-18.5，~ 18-15 Ma 和 ~10.5 Ma), 连同以 Somun Cura 地层（~32 Ma、~27-26 Ma、~26-25 Ma 和~21.5 Ma）为代表的四次溢流玄武岩喷流脉冲。与火山复合体和 Somun Cura 组相关的岩浆脉冲的叠加和重现反对应用“高原前”、“高原”和“高原后”方案，该方案已被修正。与 Somun Cura 组和火山复合体相关的最大量的岩浆分别在渐新世晚期和中新世早期被挤出。Somun Cura 组的就位面积随着时间的推移而发生变化，从西南方向开始大致呈逆时针方向的时空格局。晚始新世至中渐新世火山复合体记录的岩浆活动似乎在早中新世沿 NW-SE 和 NE-SW 廊道交替集中，并沿 N-S 带向西集中。这种系统组织可能与先前结构的重新激活有关，这是由法拉隆-纳斯卡板块和南美板块之间会聚向量的运动学变化引发的。