Magma evolution of the East Eifel volcanic field from a perspective based on detrital zircon in modern river sediment

基于现代河流沉积物碎屑锆石视角的东埃菲尔火山场岩浆演化

• 批准号: 461405636
• 负责人: Professor Dr. Axel Karl Schmitt, Ph.D.
• 金额: --
• 依托单位: Abteilung Petrologie und Geochemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/461405636?language=en
• 关键词: Magma; evolution; East; Eifel; volcanic

With the eruption of Laacher See volcano ca. 13,000 years ago, the Quaternary East Eifel volcanic field ranks among the youngest and most dynamic volcanically active areas in Central Europe. Earthquakes, uplift, and gas emissions occur focused in this region, suggesting persistent migration of magmatic fluids from anomalously hot upper mantle zones to the present day. Geodetic and geophysical methods, however, can only image the current conditions in the crust and mantle underneath the volcanic cover. To improve the understanding of the long-term processes and timescales of magma transfer from the mantle to the surface, investigations of past eruptions are therefore essential. Conventionally, samples of lava, pyroclastic fragments or xenoliths from volcanic deposits are collected for such investigations. This punctuated sampling, however, is labor intensive and prone to bias. Instead, it is proposed here to investigate modern stream sediments from the East Eifel, from which zircon can be extracted as a particularly resistant and datable index mineral at relative ease. In the liquid line of descent, zircon crystallizes in evolved melts, which for the East Eifel were tapped predominantly in the phonolitic‒trachytic volcanic centers of Rieden, Wehr, and Laacher See. In addition, mafic volcanics occasionally contain zircon megacrysts which represent xenocrysts entrained from plutonic bodies at depth during magma ascent. In this project, stream sediment of the Nette and Brohlbach catchments will be sampled to extract zircon using in-situ hydraulic separation. Both stream systems drain an area that encompasses nearly all East Eifel volcanic centers and thus can yield a complete picture of all zircon-bearing sources in regional volcanic deposits. A representative number (n = 300) of volcanic detrital zircon crystals will be dated using uranium-thorium and uranium-lead geochronology, and their oxygen-hafnium isotopic compositions will be determined. Results will aid in clarifying critical questions regarding the causes for spatially focused episodes in volcanic activity, which are known from existing eruption ages and volumes for the East Eifel. The analysis of detrital components in modern streams located in young volcanic areas allows rapid and comprehensive sampling, which can also include minerals of already weathered and eroded volcanic edifices. This novel approach has potential to be widely applied to other volcanic regions worldwide.

随着Laacher See火山的爆发，13，000年前，第四纪东艾菲尔火山区是中欧最年轻，最具活力的火山活动区之一。地震、隆升和气体排放集中发生在这一地区，表明岩浆流体从异常热的上地幔区持续迁移到今天。然而，大地测量和地球物理方法只能描绘火山覆盖层下地壳和地幔的当前状况。为了更好地了解岩浆从地幔转移到地表的长期过程和时间尺度，对过去喷发的调查至关重要。通常，为进行此类调查，会采集火山沉积物中的熔岩、火山碎屑或捕虏体样品。然而，这种间断采样是劳动密集型的，并且容易产生偏差。相反，它建议在这里调查现代流沉积物从东艾菲尔，从锆石可以提取作为一个特别耐和可测年的指标矿物相对容易。在下降的液体线中，锆石结晶在演化的熔体中，东艾菲尔主要是在Rieden，Wehr和Laacher See的响岩粗面质火山中心被挖掘。此外，镁铁质火山岩偶尔含有锆石巨晶，代表在岩浆上升过程中从深部深成岩体中夹带出来的捕虏晶。在本项目中，将对Nette和Brohlbach集水区的河流沉积物进行采样，以使用现场水力分离法提取锆石。这两个水系的排水区域几乎涵盖了所有东艾菲尔火山中心，因此可以完整地了解区域火山沉积物中所有含锆石的来源。将使用铀-钍和铀-铅地质年代学对代表性数量（n = 300）的火山碎屑锆石晶体进行测年，并确定其氧-铪同位素组成。结果将有助于澄清关键问题的原因，在火山活动中，这是已知的现有的喷发年龄和卷东艾菲尔。对位于年轻火山地区的现代河流中的碎屑成分进行分析，可以快速和全面地取样，其中还可以包括已经风化和侵蚀的火山建筑物的矿物。这种新方法有可能广泛应用于世界其他火山地区。