Abstract The early Jurassic volcanism of Central Patagonia covers an extensive area of 50,000 km2 where the volcanic deposits occur as isolated systems. The volcanic records form an elongated belt in which the composition, depositional and genetic features, show several differences along with its distribution. The Canadon Chileno Complex (CCHC), located in the Rio Negro province, provides the opportunity to evaluate and improve the knowledge about the Lower Jurassic volcanic stratigraphy and the lower Jurassic regional setting of Central Patagonia. Based on the field and laboratory data developed in the present work, 22 lithofacies were recognized and grouped into eight facies associations. The continental sedimentary environments include alluvial fan deposits (FA 1), ephemeral deposits (FA 2), braided fluvial deposits (FA 3), alluvial plains, or over banks (FA 4), and lacustrine deposits (FA 9). On the other hand, the pyroclastic facies were separated according to the pyroclastic currents involved during the deposition; into fall-out, dilute, and density currents (FA 5, FA 6, and FA 7). Effusive andesitic feeders and lava-flows (FA 8) were also recognized. The stratigraphic data obtained in the present work allow proposing the existence of two felsic diatreme volcanoes in the CCHC records - described here as Southern and Northern Zone-, developed over a local subsided area, represented by an asymmetrical basin. Seven units were recognized and described in the CCHC (Units a, b, c, d, e, f, and g: unit (a) represents an initial stage of continental sedimentation recorded throughout the entire Complex. Unit (b) represents the upper felsic diatreme facies, in Southern Zone of the Complex, where debris flows are interbedded with massive lapilli-tuff deposits. Unit (c) consists of local andesitic lavas flows and feeder dikes, and the unit (d) consists of welded lapilli tuff deposits interpreted as the growth of the volcanic system. The Northern Zone evolves similarly with the felsic intra-diatreme deposits of unit (e). The unit (f) consisting of an effusive stage represented by extended andesitic lava flows. Finally, a deep lacustrine system is installed (unit g) that includes shallow and deep facies, with intercalations of local pyroclastic deposits. Also, new geochronological data (U-Pb zircon age of 188 ± 3 Ma) was determined to confirm and reinforce the correlation criteria between the different volcanic areas in Central Patagonia, indicating that the volcanism described here is synchronous with the Northern silica-rich calderas of the Garamilla Formation as well as the large andesitic volcanoes of the Lonco Trapial Formation located southward to the CCHC. The regional volcanism changes described, in the present work, are connected with the N-S rift segment limited by E-W regional transfer fault systems developed in continuity to the strike-slip structures of the La Esperanza area.

中文翻译：

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在巴塔哥尼亚中部确认下侏罗纪长英质火山岩作为沿走向裂谷分割的证据

摘要 中巴塔哥尼亚侏罗纪早期火山活动覆盖了50,000平方公里的广阔区域，火山沉积以孤立系统形式出现。火山记录形成了一条细长的带，其中的组成、沉积和成因特征在其分布上表现出一些差异。Canadon Chileno Complex (CCHC) 位于 Rio Negro 省，为评估和提高有关下侏罗统火山地层和中巴塔哥尼亚下侏罗统区域环境的知识提供了机会。根据目前工作中开发的现场和实验室数据，识别出 22 个岩相并将其分为 8 个相组合。大陆沉积环境包括冲积扇沉积物（FA 1）、短暂沉积物（FA 2）、辫状河流沉积物（FA 3）、冲积平原、或超过银行（FA 4）和湖泊存款（FA 9）。另一方面，根据沉积过程中涉及的火山碎屑流将火山碎屑相分离；分为沉降电流、稀释电流和密度电流（FA 5、FA 6 和 FA 7）。喷出的安山岩馈线和熔岩流（FA 8）也被识别出来。在目前的工作中获得的地层数据允许在 CCHC 记录中提出两个长英质火山口的存在 - 这里描述为南部和北部地区 - 在当地下沉区域开发，以不对称盆地为代表。CCHC 中识别和描述了七个单元（单元 a、b、c、d、e、f 和 g：单元 (a) 代表整个复合体记录的大陆沉积的初始阶段。单元 (b) 代表上部长英质硅质相，在复合体的南部区域，在那里，泥石流与大量的凝灰岩沉积物互层。单元 (c) 由当地的安山岩熔岩流和支流岩脉组成，单元 (d) 由被解释为火山系统生长的熔结火山灰凝灰岩沉积物组成。北部区域的演化与单元 (e) 的长英质岩内沉积物类似。单元 (f) 由一个以延伸的安山岩熔岩流为代表的喷流阶段组成。最后，安装了一个深湖系统（单位 g），包括浅相和深相，局部火山碎屑沉积物夹层。此外，还确定了新的地质年代学数据（U-Pb 锆石年龄为 188 ± 3 Ma），以确认和加强巴塔哥尼亚中部不同火山区之间的相关标准，表明这里描述的火山活动与 Garamilla 组的北部富含二氧化硅的火山口以及位于 CCHC 以南的 Lonco Trapial 组的大型安山火山同步。在目前的工作中所描述的区域火山作用变化与受 EW 区域转移断层系统限制的 NS 裂谷段有关，该断层系统与 La Esperanza 地区的走滑结构保持连续性。