Imprints of hydrocarbon-bearing basinal fluids on a karst system: Mineralogical and fluid inclusion studies from the Buda Hills, Hungary

Zsófia Poros, Andrea Mindszenty, Ferenc Molnár, Jacques Pironon, Orsolya Győri, Paola Ronchi, Zoltán Szekeres

Research output: Contribution to journalArticle

23 Citations (Scopus)


Calcite veins and related sulphate-sulphide mineralisation are common in the Buda Hills. Also, abundant hypogenic caves are found along fractures filled with these minerals pointing to the fact that young cave-forming fluids migrated along the same fractures as the older mineralising fluids did. The studied vein-filling paragenesis consists of calcite, barite, fluorite and sulphides. The strike of fractures is consistent-NNW-SSE-concluding a latest Early Miocene maximum age for the formation of fracture-filling minerals. Calcite crystals contain coeval primary, hydrocarbon-bearing- and aqueous inclusions indicating that also hydrocarbons have migrated together with the mineralising fluids. Hydrocarbon inclusions are described here for the first time from the Buda Hills. Mixed inclusions, i. e., petroleum with 'water-tail', were also detected, indicating that transcrystalline water migration took place. The coexistence of aqueous and petroleum inclusions permitted to establish the entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (<1. 7 NaCl eq. wt%) implies that hydrocarbon-bearing fluids were diluted by regional karst water. FT-IR investigations revealed that CO 2 and CH 4 are associated with hydrocarbons. Groundwater also contains small amounts of HC and related gases on the basin side even today. Based on the location of the paleo- and recent hydrocarbon indications, identical migration pathways were reconstructed for both systems. Hydrocarbon-bearing fluids are supposed to have migrated north-westward from the basin east to the Buda Hills from the Miocene on.

Original languageEnglish
Pages (from-to)429-452
Number of pages24
JournalInternational Journal of Earth Sciences
Issue number2
Publication statusPublished - Mar 2012


  • Buda Thermal Karst
  • Calcite
  • Hydrocarbon migration
  • Miocene
  • Pannonian Basin
  • Petroleum inclusion

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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