Abstract

Traces of extremely powerful explosive volcanic eruptions are documented in the southern Moscow Syneclise; the eruptions occurred in the Moscovian Age about 309 million years ago in Variscan orogenic regions adjacent to the East European Platform. Interbeds of altered volcanic ash, 5–15 cm thick, can be traced over the distance of tens of kilometers in the sediments referring to the Podolskian and Myachkovian substages of the Moscovian Stage. These interbeds are composed of calcareous clays of montmorillonite composition and contain grains of zircon, apatite, ilmenite, biotite, K-feldspar, and quartz. Two types of K-feldspar (authigenic and volcanic) referring to the sanidine group are identified. U–Pb SIMS dating of pyroclastic zircons from the tuffaceous bed at the boundary between the Podolskian and Myachkovian showed an age of 308.9 ± 2.3 Ma, and ⁴⁰Ar/³⁹Ar dating of volcanic sanidine at a higher level showed the age of 305.5 ± 2.7 Ma, which agrees well with the available age estimates for the stage boundaries in the Pennsylvanian. Analysis of the Late Paleozoic volcanism in the nearby regions showed that the most likely area where catastrophic explosions took place, with subsequent transportation of volcanic ash to the southern Moscow Syneclise, is the zone of the North Caucasus.

中文翻译：

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中东欧地台莫斯科期（中宾夕法尼亚期、石炭纪）灾难性火山喷发痕迹

摘要

莫斯科南部的 Syneclise 记录了极其强烈的火山爆发的痕迹；火山喷发发生在大约 3.09 亿年前的莫斯科时代，位于东欧地台附近的华力斯坎造山带。在莫斯科阶段的波多尔斯基阶和米亚奇科阶亚阶段的沉积物中，可以在数十公里的距离内追踪到厚度为 5-15 厘米的蚀变火山灰互层。这些互层由蒙脱石组成的钙质粘土组成，并含有锆石、磷灰石、钛铁矿、黑云母、钾长石和石英颗粒。确定了两种类型的钾长石（自生和火山），指的是sanidine 组。Podolskian 和 Myachkovian 交界处凝灰质层的火山碎屑锆石 U-Pb SIMS 测年显示年龄为 308.9 ± 2.3 Ma，⁴⁰ Ar/ ³⁹ Ar 较高水平的火山群山定年测年显示年龄为 305.5 ± 2.7 Ma，这与可用的宾夕法尼亚阶段边界的年龄估计吻合良好。对附近地区晚古生代火山活动的分析表明，最有可能发生灾难性爆炸的地区是北高加索地区，随后火山灰将其运送到莫斯科南部的赛尼克利斯地区。