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Structural architecture and the episodic evolution of the ediacaran Campo Alegre Basin (southern Brazil): Implications for the development of a synorogenic foreland rift and a post-collisional caldera volcano
Journal of South American Earth Sciences ( IF 1.8 ) Pub Date : 2021-01-06 , DOI: 10.1016/j.jsames.2020.103147
Lucas Martins Lino , Francy Roxana Quiroz-Valle , Vinicius Louro , Miguel Ângelo Stipp Basei , Silvio Roberto Farias Vlach , Mathias Hueck , Patricio Rodrigo Montecinos Munõz , Sérgio Brandolise Citroni

During the last decades, tectonic models provided new insight into the evolution of the Luis Alves, Curitiba, and Paranaguá terranes, which are all limited by thrust and transpressive shear zones, nowadays outcropping only as deep crustal horizons and presenting poorly known lateral displacements. An essential puzzle piece to understanding the juxtaposition processes and evolution of these blocks in the Neoproterozoic lies in the Campo Alegre Basin in Southern Brazil, a volcano-sedimentary sequence deposited during the middle to late Ediacaran. Based on new U–Pb geochronological, structural, and aero-geophysical data, at least two main stages of filling and subsidence have been identified in this region, namely the basin and the caldera stages. In the Basin Stage, the regional collisional tectonics triggered the far-field stress resulting in a local extension at ∼605 ± 5 Ma through the reactivation of NNW-SSE inherited basement structures. The deposition of the sedimentary basin finishes with the Initial Volcanic Activity, corresponding to a bimodal mildly alkaline, predominantly mafic and effusive volcanism. After the transition to a post-collisional setting, probably at ca. 595 Ma, regional extension led to the Caldera Stage of the basin, which had its volcanic peak at ca. 583-580 Ma, contemporaneous with the intrusive A-type magmatism of the nearby Graciosa Province. The Main Volcanic Activity corresponds to a predominantly alkaline silica-saturated, effusive to explosive magmatic manifestation culminating with the formation of a caldera-volcano. The volcanic products from both the initial and the main volcanic activities were raised to the surface mainly through NNW-SSE and ENE-WSW oriented conduits, respectively reactivated and neo-formed during the collisional process. The crustal-scaled discontinuities associated with the development of the sedimentary basin have further controlled the subsidence of the caldera structure, which might be the main mechanism of preservation for these ancient volcano-sedimentary sequences in the evolution of the Campo Alegre Basin.



中文翻译:

埃迪卡卡拉坎波阿莱格里盆地(巴西南部)的结构构造和情景演变:对前陆裂谷和碰撞后破火山口火山发展的影响

在过去的几十年中,构造模型为Luis Alves,Curitiba和Paranaguá地貌的演化提供了新的见识,这些地貌都受到推力和超压剪切带的限制,如今仅在地壳深处露头,并呈现出鲜为人知的横向位移。要了解新元古代的并置过程和这些块体的演化,必不可少的难题在于巴西南部的坎波·阿莱格里盆地,这是一个在埃迪卡拉河中晚期沉积的火山沉积序列。根据新的U–Pb年代学,结构和航空地球物理数据,在该区域至少确定了两个主要的充填和沉降阶段,即盆地和火山口阶段。在盆地阶段,区域碰撞构造触发了远场应力,通过重新激活NNW-SSE继承的基底结构,在605±5 Ma处引起了局部扩展。沉积盆地的沉积以初始火山活动结束,这与双峰的轻度碱性,主要是镁铁质和喷发性火山作用相对应。过渡到碰撞后设置后,大概在 595 Ma,区域扩展导致破火山口舞台盆地的顶部,其火山峰大约在 583-580 Ma,与附近格拉西奥萨省的侵入性A型岩浆作用相同。主要火山活动对应于主要为饱和的碱性二氧化硅,对爆发的岩浆表现有强烈的影响,最终形成了火山口火山。最初和主要火山活动的火山产物主要通过NNW-SSE和ENE-WSW定向导管上升到地表,在碰撞过程中分别重新活化和新形成。与沉积盆地发育相关的地壳尺度不连续性进一步控制了火山口结构的下陷,这可能是这些古老的火山-沉积序列在坎波阿莱格里盆地演化过程中保存的主要机制。

更新日期:2021-01-06
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