Upper Jurassic event of ignimbrite flare-up linked to extensional tectonics: the beginnings of Andean volcanism in southern Patagonia (~ 46° S, Chile)

IF 1.8 3区 地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY
Rodrigo J. Suárez, Pablo D. González, A. Pablo Rolando, Sebastián A. Andrada, Claudia B. Zaffarana, Damien Koerber
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Abstract

Understanding the origin of Late Jurassic volcanism in southern Patagonia is crucial for unraveling the early Andean orogenic evolution. However, radiometric dating is not connected to stratigraphic analysis along the South Patagonian Andes, which obscures the real duration of the Late Jurassic magmatic activity. In this contribution, we present the results of a volcanic stratigraphy analysis, complemented by structural and petrographic data, on a thick succession of acidic volcanogenic rocks in the Laguna Verde district of southern Chile located along the south shore of General Carrera-Buenos Aires Lake. Through the recognition of igneous stratigraphy, we strategically sampled representative volcanogenic rocks that cover the entire duration of eruptive activity. By doing so, the new U–Pb zircon magmatic ages, combined with a compilation of U–Pb crystallization ages from the South Patagonian Andes, allows us to constrain the volcanic activity in the study area to a period of 8 My (~ 155–146 Ma, V3 stage) and 11 My considering age inherent errors. The field recognition of normal faults and the syn-kinematic emplacement of sub-volcanic bodies, which are inferred to conform to a ring-fault system, along with the presence of a thick succession of ignimbrites, suggest that the syn-extensional volcanic emplacement occurred in a caldera volcanic environment. This setting was responsible for the short-lived, voluminous eruptions. Furthermore, the high Th/U zircon ratios identified for the ~ 155–150 Ma period indicate the climax of extensional tectonics. The integration of these data supports the hypothesis that retreating-mode subduction played a major role in producing ignimbrite flare-ups.

Graphical abstract

Abstract Image

与伸展构造有关的上侏罗世燃爆事件:巴塔哥尼亚南部安第斯火山活动的开端(智利,南纬约 46 度)
了解巴塔哥尼亚南部晚侏罗世火山活动的起源对于揭示早期安第斯造山运动的演变至关重要。然而,辐射测定年代与南巴塔哥尼亚安第斯山脉的地层分析并不相关,这掩盖了晚侏罗世岩浆活动的真实持续时间。在这篇论文中,我们介绍了对智利南部卡雷拉将军湖-布宜诺斯艾利斯湖南岸拉古纳维德地区厚厚的酸性火山岩层序进行火山地层分析的结果,并辅以构造和岩石学数据。通过对火成岩地层的识别,我们战略性地采集了具有代表性的火山岩样本,这些样本涵盖了整个火山喷发活动时期。这样,新的 U-Pb 锆石岩浆年龄与南巴塔哥尼亚安第斯山脉的 U-Pb 结晶年龄汇编相结合,使我们能够将研究区域的火山活动限制在 8 My(约 155-146 Ma,V3 阶段)和 11 My(考虑到年龄固有误差)时期。正断层的实地确认和次火山体的同步运动式喷发(推断为符合环状断层系统),以及厚厚的火成岩演替的存在,表明同步伸展式火山喷发发生在火山口火山环境中。这种环境造成了短暂而大量的喷发。此外,在〜155-150 Ma时期发现的高Th/U锆石比值表明当时正处于伸展构造的高潮期。这些数据的整合支持了这样的假设,即后退模式的俯冲在产生火成岩爆发中发挥了重要作用。
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来源期刊
International Journal of Earth Sciences
International Journal of Earth Sciences 地学-地球科学综合
CiteScore
4.60
自引率
4.30%
发文量
120
审稿时长
4-8 weeks
期刊介绍: The International Journal of Earth Sciences publishes process-oriented original and review papers on the history of the earth, including - Dynamics of the lithosphere - Tectonics and volcanology - Sedimentology - Evolution of life - Marine and continental ecosystems - Global dynamics of physicochemical cycles - Mineral deposits and hydrocarbons - Surface processes.
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