Mineralogical and gemmological characteristics of garnets associated with xenoliths within trachyte dome, Hisarlikaya (Ankara), Central Anatolia, Turkey

Varol E. , TATAR ERKÜL S., Dogan Kulahci G. D.

TURKISH JOURNAL OF EARTH SCIENCES, vol.30, no.3, pp.379-391, 2021 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 30 Issue: 3
  • Publication Date: 2021
  • Doi Number: 10.3906/yer-2006-14
  • Page Numbers: pp.379-391


Garnet-bearing xenoliths are observed within a trachytic dome extrusion in the Hisarlikaya region (Ankara). These garnets exhibiting greenish-reddish-dark brown colour and ranging in sizes up to 1 cm were examined in terms of mineralogical, geochemical, and gemmological characteristics. Mineralogical studies indicate that these garnets (And(88-)(93)Grs(7)(-1)(2)) are linked to solid solution series, which are dominantly andradite with lower content of grossular. According to major, trace, and rare earth element (REE) analysis, the representative garnet crystal shows high CaO, Fe2O3, Al2O3, MgO, MnO, V, W, and light rare earth elements (LREE) concentrations. These high concentrations might indicate the mobility of these elements during skarn formation related with contact metamorphism, material exchange occurring via hydrothermal fluids, site geometry of the crystal, ionic radius of cations, and charge balance.