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Tephrostratigraphy and Magma Evolution Based on Combined Zircon Trace Element and U-Pb Age Data: Fingerprinting Miocene Silicic Pyroclastic Rocks in the Pannonian Basin
Frontiers in Earth Science ( IF 2.0 ) Pub Date : 2021-01-25 , DOI: 10.3389/feart.2021.615768
Réka Lukács , Marcel Guillong , Olivier Bachmann , László Fodor , Szabolcs Harangi

We present a novel approach to use zircon as a correlation tool as well as a monitor for magma reservoir processes in silicic volcanic systems. Fingerprinting eruption products based on trace element content and U-Pb dates of zircon offers a promising, previously underestimated tephra correlation perspective, particularly in cases where the main minerals and glass are altered. Using LA-ICP-MS analyses, a rapid and cost-effective method, this study presents U-Pb dates and trace element concentration data of more than 950 zircon crystals from scattered occurrences of early to mid-Miocene silicic ignimbrites in the northern Pannonian Basin, eastern-central Europe. This magmatic phase produced >4000 km3 of erupted material, which provide unique stratigraphic marker horizons in central and southern Europe. The newly determined zircon U-Pb eruption ages for the distal pyroclastic deposits are between 17.5 and 14.3 Ma, comparable with the previously published ages of the main eruptive events. Multivariate discriminant analysis of selected trace element concentrations in zircon proved to be useful to distinguish the main volcanic units and to correlate the previously ambiguously categorized pyroclastic deposits with them. Using the zircon trace element content together with published glass data from crystal-poor ignimbrites, we determined the zircon/melt partition coefficients. The obtained values of the distinct eruption units are very similar and comparable to published data for silicic volcanic systems. This suggests that zircon/melt partition coefficients in calc-alkaline dacitic to rhyolitic systems are not significantly influenced by the melt composition at >70 wt% SiO2 at near solidus temperature. The partition coefficients and zircon trace element data were used to calculate the equilibrium melt composition, which characterizes the eruption products even where glass is thoroughly altered or missing. Hence, our results provide important proxies for tephrostratigraphy in addition to yielding insights into the complex processes of silicic magma reservoirs.



中文翻译:

锆石微量元素和U-Pb年龄数据相结合的地层和岩浆演化:潘诺尼盆地中新世硅质碎屑岩的指纹识别

我们提出了一种新颖的方法来使用锆石作为相关工具以及硅质火山岩系统中岩浆储层过程的监测器。基于微量元素含量和锆石的U-Pb日期的指纹萌发产品提供了一个有希望的,以前被低估的特非拉相关性的观点,尤其是在主要矿物质和玻璃被改变的情况下。本研究使用一种快速且经济高效的方法LA-ICP-MS分析,显示了Pannonian盆地北部中新世早期至中新世硅质火成岩中零星出现的950多个锆石的U-Pb数据和痕量元素浓度数据。 ,中东欧。这个岩浆期产生了> 4000 km 3喷发的物质,在中欧和南欧提供了独特的地层标记层。新近确定的远端火山碎屑沉积的锆石U-Pb喷发年龄在17.5和14.3 Ma之间,与先前公布的主要喷发事件年龄相当。锆石中所选微量元素浓度的多判别分析被证明有助于区分主要的火山岩单元,并将先前模棱两可的火山碎屑矿床与它们联系起来。利用锆石中微量元素的含量以及贫晶火成岩中已公布的玻璃数据,我们确定了锆石/熔体分配系数。获得的不同喷发单位的值非常相似,可以与硅质火山系统的公开数据相比较。2在接近固相线的温度下。分配系数和锆石微量元素数据用于计算平衡熔体成分,即使在玻璃被彻底改变或缺失的情况下,也可表征喷发产物。因此,我们的结果除了对硅质岩浆储层的复杂过程提供了见识之外,还为断层岩层照相提供了重要的代理。

更新日期:2021-02-25
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