Petrogenesis of a Large-Scale Miocene Zeolite Tuff in the Eastern Slovak Republic

Autor(en)

Cornelius Tschegg, A. Hugh N. Rice, Bernhard Grasemann, Elisabeth Matiasek, Pavel Kobulej, Martin Dzivak, Thomas Berger

Abstrakt

Over 170,000 metric tonnes of high-grade clinoptilolite tuff were extracted from the open-pit mine in Nižný Hrabovec (eastern Slovak Republic) in 2018, making it one of the world’s major natural clinoptilolite producers. The mine is hosted in a Miocene volcanogenic-sedimentary deposit in the East Slovak basin, with estimated 150 million tonnes of clinoptilolite tuff—the economically most important reserve in the European Union. The 100-m-thick tuff horizon is under- and overlain by SW-dipping shallow-marine Badenian sediments (16.30–15.03 Ma ≅ Langhian stage). The tuff is rhyolitic (74.3–77.6 wt % SiO2, 4.09–5.49 wt % Na2O + K2O) with a generally high-K calc-alkaline affinity (3.07–4.28 wt % K2O), comparable to volcanic rocks in the central segment of the Carpathian-Pannonian region of similar age. Although some parts of the tuff underwent slight geochemical changes during formation, this did not significantly change the whole-rock composition of the strikingly homogeneous raw material present in the mine. Rare earth elements (ΣREE = 117–141 ppm) show a uniform pattern, with enriched light REEs and negative Eu anomalies of 0.42 to 0.6 (when normalized to chon-drite), comparable to the upper continental crust composition. Mean

⁸⁷Sr/86Sr = 0.70880 and 143Nd/144Nd = 0.512463 indicate an enriched magmatic source, with a dominant crustal contribution. X-ray diffraction data and electron probe microanalyses show that clinoptilolite-Ca is the only zeolite phase present in the deposit. High-resolution electron probe microanalytical imaging and measurement techniques reveal that clinoptilolite is present as (1) coarse patches that either form pseudomorphs of volcanic glass shards or grew in voids and (2) ultrafine material making up the matrix of the tuff. Both textural types have Si/Al >4, and their evolution is connected to dissolution-(transport)-precipitation reactions from acidic volcanic ash under alkaline fluid influence and slightly elevated pressure-temperature (44°–84°C) conditions. Authigenic cristobalite, detected as ultrafine-grained matrix crystallites, formed during the zeolitization process from excess Si. The large-scale, remarkably homogeneous and monomineralic natural zeolite deposit formed from a well-equilibrated magmatic source, with no syn- to postsedimentary reworking and with essentially isochemical conditions during the zeolitization process.

Organisation(en)

Institut für Geologie

Externe Organisation(en)

Zeocem As, Glock Health, Science and Research GmbH

Journal

Economic Geology: Bulletin of the Society of Economic Geologists

Band

114

Seiten

1177-1194

Anzahl der Seiten

18

ISSN

0361-0128

DOI

https://doi.org/10.5382/econgeo.4679

Publikationsdatum

09-2019

Peer-reviewed

Ja

ÖFOS 2012

105105 Geochemie

Schlagwörter

ASJC Scopus Sachgebiete

Geophysics, Geology, Geochemistry and Petrology, Economic Geology

Link zum Portal

https://ucris.univie.ac.at/portal/de/publications/petrogenesis-of-a-largescale-miocene-zeolite-tuff-in-the-eastern-slovak-republic(7738c718-8c18-4e23-ac46-60eec0d1cbb9).html