Development of columnar jointing in albite rhyolite in a rapidly cooling volcanic environment (Rupnica, Papuk Geopark, Croatia)

The Rupnica locality became the first protected geosite in Croatia in 1948 owing to a well‐exposed phenomenon of columnar jointing developed in albite rhyolite. According to the geochemical signature, melt that originated at mid‐crustal depths (10–15 km) reached a shallow emplacement level as a high...

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Bibliographic Details
Published in:Terra nova (Oxford, England) England), 2014-04, Vol.26 (2), p.102-110
Main Authors: Balen, Dražen, Petrinec, Zorica
Format: Article
Language:English
Subjects:
Geochemistry
Geology
Lava
Rocks
Volcanoes
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Summary:The Rupnica locality became the first protected geosite in Croatia in 1948 owing to a well‐exposed phenomenon of columnar jointing developed in albite rhyolite. According to the geochemical signature, melt that originated at mid‐crustal depths (10–15 km) reached a shallow emplacement level as a high‐temperature lava. Non‐destructive statistical analysis conducted at the geosite revealed that relatively narrow (29.4 ± 6.3 cm) predominantly four‐ and five‐sided columns, tightly packed striae (4.8 ± 2.1 cm) and small‐amplitude wavy sets of columns (wavelength of 32.5 ± 6.7 cm) dominate the exposed part of the Rupnica. A number of features quantified through this statistical approach, together with petrography, geochemistry and the geology of the geosite's surroundings, suggest the rapid cooling of a (sub)surface acidic lava body and the behaviour of the evolving volcanic system, developing columnar jointing under the combined influence of large‐scale constitutional supercooling and thermal contraction processes.
ISSN:0954-4879
1365-3121
DOI:10.1111/ter.12075