scholarly journals Tephrostratigraphy and Magma Evolution Based on Combined Zircon Trace Element and U-Pb Age Data: Fingerprinting Miocene Silicic Pyroclastic Rocks in the Pannonian Basin

2021 ◽  
Vol 9 ◽  
Author(s):  
Réka Lukács ◽  
Marcel Guillong ◽  
Olivier Bachmann ◽  
László Fodor ◽  
Szabolcs Harangi
Keyword(s):  
Trace Element ◽  
Partition Coefficients ◽  
Pannonian Basin ◽  
Trace Element Content ◽  
Element Content ◽  
Published Data ◽  
Concentration Data ◽  
Pyroclastic Deposits ◽  
Silicic Volcanic ◽  
Melt Composition

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.

The zircon proxy in tephrostratigraphy and magma evolution studies. Fingerprinting Miocene silicic pyroclastic rocks in the Pannonian Basin and its surroundins.

2021 ◽  
Author(s):  
Réka Lukács ◽  
Maurizio Petrelli ◽  
Marcell Guillong ◽  
Olivier Bachmann ◽  
László Fodor ◽  
...  
Keyword(s):  
Machine Learning ◽  
Trace Element ◽  
Partition Coefficients ◽  
Pannonian Basin ◽  
Volcanic Glass ◽  
Machine Learning Algorithms ◽  
Published Data ◽  
Pyroclastic Deposits ◽  
Pyroclastic Rocks ◽  
Melt Composition

<p>We used combined trace element and U-Pb isotopic data of zircon from dacitic to rhyolitic pyroclastic rocks and Si-rich ash-bearing deposits to assess their tephrostratigraphic potential. Data were collected using LA-ICP-MS analyses, a rapid and cost-effective method, to obtain simultaneously trace element contents and U-Pb ages of a large number of zircon grains. The rationale in using zircon crystals for characterizing tephra deposits is that zircon is a resistant mineral phase and is usually a late crystallizing mineral in highly evolved magmas. Therefore, they are assumed to be in equilibrium with the erupted melt phase represented by the volcanic glass. Knowing the zircon/melt partition coefficients, equilibrium melt composition can be calculated even in cases when the volcanic glass in the pyroclastic material has undergone severe post-depositional alteration.</p><p>We studied Miocene silicic pyroclastic deposits in a broad area including the Pannonian Basin (eastern-central Europe) and its surroundings to characterize and correlate the explosive volcanic products. In regional scale, these deposits are usually assigned as important stratigraphic key horizons within sedimentary successions and thus, they help to understand better the chronostratigraphic framework and palaeoenvironmental changes having affected the highly-dynamic Mediterranean-Paratethys system.</p><p>The early to middle Miocene silicic pyroclastic deposits within the Pannonian basin are estimated to be more than 4000 km<sup>3</sup> in volume within 4 Myr, suggesting an important ignimbrite flare-up event. At least 4 main eruption units were distinguished and characterized, each could have regional (>>100 km) effects. We demonstrate here the power of multivariate discriminant analyses as well as machine learning techniques in distinguishing the main eruptive units and their correlation with unclassified distal deposits based on zircon trace element data. The machine learning algorithms were trained using our zircon database with trace elements as input parameters. Both the discriminant analysis and the machine learning methods gave reliable results, i.e. distinguished the main 4 pyroclastic units and found the link of the distal deposits to them. As a result, we provide a robust zircon-based fingerprint that can be used as a proxy in tephrostratigraphy.</p><p>Zircon trace element compositions indicate distinct silicic magmas resided partly coeval in the upper crust. Using trace element content of zircon and glasses from the same samples of crystal-poor ignimbrites, we determined zircon/melt partition coefficients. The obtained values of the 4 main units are very similar and comparable with published data for silicic volcanic systems. This suggests that zircon/melt partition coefficients in calc-alkaline silicic systems are not significantly influenced by melt composition at >70 wt% SiO<sub>2</sub>. These findings let us use these zircon/melt partition coefficients to calculate the equilibrium melt compositions for the pyroclastic occurrences even in case when no glass data were available. The zircon proxy approach can be limited by the non-existence of zircon in the rocks and also by the fact that no systematic compositional difference is found between eruption products, although the latter problem similarly stands for glass chemistry-based tephrostratigraphic studies.</p><p>This study was supported by the NKFIH FK-131869 project.</p>

Restitic or not? Insights from trace element content and crystal — Structure of spinels in African mantle xenoliths

Lithos ◽  
2017 ◽  
Vol 278-281 ◽  
pp. 464-476 ◽  
Author(s):  
Davide Lenaz ◽  
Maria Elena Musco ◽  
Maurizio Petrelli ◽  
Rita Caldeira ◽  
Angelo De Min ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Trace Element ◽  
Trace Element Content ◽  
Mantle Xenoliths ◽  
Element Content

The implications of reworking on the mineralogy and chemistry of Lower Carboniferous K-bentonites

Clay Minerals ◽  
1996 ◽  
Vol 31 (3) ◽  
pp. 377-390 ◽  
Author(s):  
T. Clayton ◽  
J. E. Francis ◽  
S. J. Hillier ◽  
F. Hodson ◽  
R. A. Saunders ◽  
...  
Keyword(s):  
Trace Element ◽  
Volcanic Ash ◽  
Clay Fraction ◽  
Trace Element Content ◽  
Element Content ◽  
Heavy Minerals ◽  
Lower Carboniferous ◽  
Greenish Yellow ◽  
Trace Element Contents ◽  
Plastic Clays

AbstractPotassium-bentonites have been found in the Courceyan Lower Limestone Shales near Burrington Combe and Oakhill, Somerset, consisting of thin, greenish yellow, plastic clays interbedded within a mudrock and limestone sequence. Mineralogically, the clay fraction is composed of virtually monomineralic interstratified illite-smectite containing 7–10% smectite layers. The clay fraction of the surrounding mudrocks, however, consists of an illite-chlorite dominated assemblage. Their mineral composition, trace element content, and the relative abundance of zircon crystals suggest an origin from burial of montmorillonite originally formed from volcanic ash. The presence of anomalously high trace element contents with both euhedral and rounded zircon grains in the Oakhill K-bentonites suggests a secondary or reworked origin for these samples. In contrast, the presence of a non-anomalous trace element content and large (>100 μm) euhedral zircon grains suggests that the Burrington K-bentonite is primary in origin. Modelling of whole-rock rare-earth element (REE) patterns shows that the Oakhill REE pattern can be derived from the Burrington pattern by the addition of small contributions from zircon and monazite, two major heavy minerals present. These K-bentonites probably represent the oldest Carboniferous K-bentonites so far recorded in the British Isles.

Variation in trace element content between liver lobes in cattle. How important is the sampling site?

2019 ◽  
Vol 52 ◽  
pp. 53-57 ◽  
Author(s):  
Diego Luna ◽  
Marta Miranda ◽  
Víctor Pereira ◽  
Marta López-Alonso
Keyword(s):  
Trace Element ◽  
Sampling Site ◽  
Trace Element Content ◽  
Element Content
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