Mineralogical and geochemical characterization and implications for provenance of Roman granite columns in ancient Tripolis (Denizli, Turkey)

Abstract

Roman granite columns of the monumental fountain (Nymphaeum) in Tripolis ancient city (Denizli, Western Turkey) have porphyro-phaneritic texture and are characterized by the presence of a K-feldspar megacrysts. The columns mainly consist of K-feldspar (microcline and orthoclase), quartz, plagioclase, mafic minerals (biotite and amphibole), and minor amount of titanite, apatite, zircon, and opaque minerals. Electron probe microanalysis (EPMA) reveals that plagioclase is oligoclase (An16–23), trioctahedral mica is ferro-biotite and siderophyllite (Mg#: 0.20–0.24), and amphibole is hastingsite (Mg#: 0.19–0.24) in composition. Calculated temperature and pressure values from amphibole–plagioclase mineral pairs are 933 to 1000 °C (average 971 ± 13.5 °C) and are 3.5 to 6.9 kbar (average 4.8 ± 0.7 kbar), respectively. Roman granite columns are mildly alkaline and characterized by metaluminous nature. In Primitive Mantle (PM), Oceanic Ridge Granite (ORG), and Continental Crust (CC) multi-element normalization diagrams, the columns show LILE enrichment relative to HFSE. Furthermore, they bear A-type parental magma characteristics that occurred in a late/post-orogenic tectonic setting. Detailed mineralogical–petrographic, mineral chemistry, geochemical, and some archeological data support the assumption that Roman granite columns have similar features to Red Aswan Granite in Egypt and were imported to Tripolis.