Combined Sr-Nd isotopic and geochemical fingerprinting as a tool for identifying tephra layers: Application to deep-sea cores from Eastern Mediterranean Sea
Combined Sr-Nd isotopic and geochemical fingerprinting as a tool for identifying tephra layers: Application to deep-sea cores from Eastern Mediterranean Sea
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结合 Sr-Nd 同位素和地球化学指纹作为识别火山灰层的工具：在东地中海深海岩心中的应用
DOI：
10.1016/j.chemgeo.2016.09.022
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
L. Civetta
中科院分区：
文献类型：
--
作者：
M. D’Antonio;R. Mariconte;I. Arienzo;F. C. Mazzeo;A. Carandente;D. Perugini;M. Petrelli;C. Corselli;G. Orsi;M. S. Principato;L. Civetta
火山碎屑层从6个深海岩心，恢复之间的爱奥尼亚海和爱琴海，覆盖的时间跨度为~ 102和~ 8.2 ka BP，进行了调查，目的是确定其火山源。通过超微化石生物地层学和腐泥层的发生定义的每个火山灰层的地层位置集成了一个彻底的地球化学表征的玻璃碎片的基础上的主要氧化物和微量元素的含量，和Sr-Nd同位素比值。主要的氧化物组合物允许他们分为三组（K-粗面岩，过碱性流纹岩，安山岩），微量元素数据的主成分分析证实。原始地幔标准化的微量元素分布模式允许精确识别的地球化学亲和力和地球动力学设置的每一组。虽然部分火山岩的Sr同位素组成受海水蚀变的影响很大，但143 Nd/144 Nd值结合主要氧化物和微量元素数据可很好地区分三组火山岩。因此，本文提出了La/Yb和Th/Y与143 Nd/144 Nd比值的判别图解，用于识别东地中海地区102- 8.2kaBP时间跨度内活动的潜在火山岩源，并将6个K粗面质火山岩归属于Y-5地层标志（意大利南部Campi Flegrei的Campanian火山灰凝灰岩喷发，约39 ka BP），以及两个与Y-6地层标志（西西里海峡Pantelleria岛的绿色凝灰岩喷发，约46 ka BP）相关的泛碲质（=过碱性流纹岩）火山岩。安山质火山灰，地层约束在~ 39和~ 83-102 ka BP之间，可能对应于在东地中海的几个深海岩心中发现的X-1地层标志，尽管其归属在文献中仍有争议。微量元素含量的基础上，Sr-Nd同位素特征的支持下，它是在这里假设，这火山灰可能与位于爱琴海地区的火山源，可能是圣托里尼岛。更一般地说，这项研究表明，Sr-Nd同位素与主要氧化物和微量元素的地球化学指纹的选择和纯化的玻璃碎片的组合是一个非常有效的工具，用于确定性质和来源可疑火山灰层。
Tephra layers from six deep-sea cores, recovered between the Ionian and the Aegean Seas, and covering a time span between ~ 102 and ~ 8.2 ka BP, were investigated with the aim of identifying their volcanic source. The stratigraphic position of each tephra layer defined by means of nannofossil biostratigraphy and occurrence of sapropel layers was integrated with a thorough geochemical characterization of glass shards based on major oxides and trace elements content, and Sr-Nd isotope ratios. Major oxides composition permitted their subdivision into three groups (K-trachyte, peralkaline rhyolite, andesite), confirmed by Principal Component Analysis on trace elements data. Primordial mantle-normalized trace elements distribution patterns allowed for precise identification of the geochemical affinity and geodynamical setting of each group. Although the Sr isotopic composition of some investigated tephras was deeply affected by seawater alteration as expected, the143Nd/144Nd values discriminate well the three groups of tephras in combination with major oxides and trace elements data. Therefore, La/Yb and Th/Y vs.143Nd/144Nd discrimination diagrams are proposed for identification of potential volcanic sources active in the 102–8.2 ka BP time span in the Eastern Mediterranean area for unknown tephras.The obtained results have permitted the attribution of six K-trachytic tephras to the Y-5 stratigraphic marker (Campanian Ignimbrite eruption of Campi Flegrei, Southern Italy, ~ 39 ka BP), and two pantelleritic (= peralkaline rhyolite) tephras to the Y-6 stratigraphic marker (Green Tuff eruption of Pantelleria Island, Sicily Channel, ~ 46 ka BP). The andesitic tephra, stratigraphically constrained between ~ 39 and ~ 83–102 ka BP, might correspond to the X-1 stratigraphic marker, found in several deep-sea cores of the Eastern Mediterranean Sea, although its attribution is still debated in the literature. On the basis of trace elements content, supported by Sr-Nd isotopic features, it is here hypothesized that this tephra could be related to a volcanic source located in the Aegean Sea area, probably the island of Santorini. More generally, this study demonstrates that the combination of Sr-Nd isotopic with major oxide and trace element geochemical fingerprinting on selected and purified glass shards is a very effective tool for identifying nature and source of doubtful tephra layers.
DOI：
10.1073/pnas.1204579109
发表时间：
2012-08-21
影响因子：
11.1
作者：
Lowe, John;Barton, Nick;Tzedakis, Polychronis C.
通讯作者：
Tzedakis, Polychronis C.