The Gǎtaia Pleistocene lamproite: A new occurence at the southeastern edge of the Pannonian Basin, Romania

I. Seghedi, Theodoros Ntaflos, Z. Pécskay

Research output: Chapter in Book/Report/Conference proceedingChapter

13 Citations (Scopus)

Abstract

The petrological identity of the lamproite occurrence situated c. 5 km south of Gǎtaia (Banat, western Romania), until now considered to be an alkali basalt, has been revealed by exploration drilling. This drilling programme pierced a slightly vesicular lava flow inside the Şumiga hill (198 m above sea level), revealing a sequence of vesicular lava intercalated with fallout scoria deposits. The isolated lamproite volcano, dated at 1.32 ± 0.06 Ma (whole-rock K/Ar method), is situated at the southeastern margin of the Pannonian Basin and at the western margin of the South Carpathians, along an important NE-SW fault system. The lamproite magma erupted through flat-lying Miocene sedimentary rocks, which overlie older crystalline basement that experienced intense lithospheric deformation and orogeny during Cretaceous times. The lamproite is associated with contemporaneous volcanic activity that lies 50-150 km to the NNE, along the South Transylvanian fault system (Lucareţ alkali basalts, Uroiu shoshonites); these rocks, however, are not consanguineous, and derive from different mantle sources. There are, however, similarities to Oligocene lamproites from Serbia (Bogovina), generated on similar basement. The lamproite is fresh and has a slightly porphyritic texture with phenocrysts of high-Mg olivine and microphenocrysts of euhedral leucite in a glassy matrix. The matrix also contains microcrysts of olivine, armalcolite, apatite, sanidine, low Al-diopside, fluorine-bearing titanium phlogopite, fluorine-bearing amphibole and accessory chrome spinels. Basulphate aggregates fill small vesicles. Very rare clots of corroded Al-phlogopite surrounded by secondary spinels are enclosed by leucite aggregates, suggesting formation during an earlier event. Major and trace element geochemistry and Sr and Nd isotopes show that the rock is a typical lamproite, close to the compositions of Leucite Hills and Gaussberg lamproites. The source for the Gǎtaia lamproite was probably a gamet harzburgite lithospheric mantle, metasomatized by alkaline mafic melts, most probably active at the Cretaceous-Palaeogene boundary. Metasomatism by alkaline melts is indicated by high abundances of incompatible trace elements, such as Ba, Sr, Rb and Zr. The Gǎtaia lamproite probably had a limited available source volume for melting that reflects the ambient thermal regime in the typical post-collisional tectonic setting active during Late Neogene to Quaternary time. Emplacement of this lamproite was probably a result of surface uplift and erosion at the base of the lithosphere, marking the collapse of the Alpine orogen.

Original languageEnglish
Title of host publicationMetasomatism in Oceanic and Continetal Lithospheric Mantle
EditorsM. Coltorti, M. Gregoire
Pages83-100
Number of pages18
DOIs
Publication statusPublished - Jan 28 2008

Publication series

NameGeological Society Special Publication
Volume293
ISSN (Print)0305-8719

ASJC Scopus subject areas

  • Water Science and Technology
  • Ocean Engineering
  • Geology

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  • Cite this

    Seghedi, I., Ntaflos, T., & Pécskay, Z. (2008). The Gǎtaia Pleistocene lamproite: A new occurence at the southeastern edge of the Pannonian Basin, Romania. In M. Coltorti, & M. Gregoire (Eds.), Metasomatism in Oceanic and Continetal Lithospheric Mantle (pp. 83-100). (Geological Society Special Publication; Vol. 293). https://doi.org/10.1144/SP293.5