The role of water and compression in the genesis of alkaline basalts: Inferences from the Carpathian-Pannonian region

I. Kovács, L. Patkó, N. Liptai, T. P. Lange, Z. Taracsák, S. A.P.L. Cloetingh, K. Török, E. Király, D. Karátson, T. Biró, J. Kiss, Zs Pálos, L. E. Aradi, Gy Falus, K. Hidas, M. Berkesi, A. Koptev, A. Novák, V. Wesztergom, T. FancsikCs Szabó

Research output: Contribution to journalArticle

Abstract

We present a new model for the formation of Plio-Pleistocene alkaline basalts in the central part of the Carpathian-Pannonian region (CPR). Based on the structural hydroxyl content of clinopyroxene megacrysts, the ‘water’ content of their host basalts is 2.0–2.5 wt.%, typical for island arc basalts. Likewise, the source region of the host basalts is ‘water’ rich (290–660 ppm), akin to the source of ocean island basalts. This high ‘water’ content could be the result of several subduction events from the Mesozoic onwards (e.g. Penninic, Vardar and Magura oceans), which have transported significant amounts of water back to the upper mantle, or hydrous plumes originating from the subduction graveyard beneath the Pannonian Basin. The asthenosphere with such a relatively high ‘water’ content beneath the CPR may have been above the ‘pargasite dehydration’ (<90 km) or the ‘nominally anhydrous’ (>90 km) solidi. This means that neither decompressional melting nor the presence of voluminous pyroxenite and eclogite lithologies are required to explain partial melting. While basaltic partial melts have been present in the asthenosphere for a long time, they were not extracted during the syn-rift phase, but were only emplaced at the onset of the subsequent tectonic inversion stage at ~8–5 Ma. We propose that the extraction has been facilitated by evolving vertical foliation in the asthenosphere as a response to the compression between the Adriatic indenter and the stable European platform. The vertical foliation and the prevailing compression effectively squeezed the partial basaltic melts from the asthenosphere. The overlying lithosphere may have been affected by buckling in response to compression, which was probably accompanied by formation of deep faults and deformation zones. These zones formed conduits towards the surface for melts squeezed out of the asthenosphere. This implies that basaltic partial melts could be present in the asthenosphere in cases where the bulk ‘water’ content is relatively high (>~200 ppm) at temperatures exceeding ~1000–1100 °C. These melts could be extracted even under a compressional tectonic regime, where the combination of vertical foliation in the asthenosphere and deep fractures and deformation zones in the folded lithosphere provides pathways towards the surface. This model is also valid for deep seated transpressional or transtensional fault zones in the lithosphere.

Original languageEnglish
Article number105323
JournalLITHOS
Volume354-355
DOIs
Publication statusPublished - Feb 2020

    Fingerprint

Keywords

  • Alkaline basalts
  • Asthenosphere
  • Carpathian-Pannonian region
  • Deformation
  • Lithosphere
  • Melting
  • Water

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

Cite this

Kovács, I., Patkó, L., Liptai, N., Lange, T. P., Taracsák, Z., Cloetingh, S. A. P. L., Török, K., Király, E., Karátson, D., Biró, T., Kiss, J., Pálos, Z., Aradi, L. E., Falus, G., Hidas, K., Berkesi, M., Koptev, A., Novák, A., Wesztergom, V., ... Szabó, C. (2020). The role of water and compression in the genesis of alkaline basalts: Inferences from the Carpathian-Pannonian region. LITHOS, 354-355, [105323]. https://doi.org/10.1016/j.lithos.2019.105323