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Titanite belongs to the common accessory minerals in Variscan (~360–350 Ma) metaluminous to slightly peraluminous tonalites to granodiorites of I-type affinity in the Tatric and Veporic Units, the Western Carpathians, Slovakia. It forms brown tabular prismatic-dipyramidal crystals (~0.5 to 10 mm in size) in association with quartz, plagioclase, and biotite. Titanite crystals commonly shows oscillatory, sector and convolute irregular zonal textures, reflecting mainly variations in Ca and Ti versus Al (1–2 wt. % Al 2 O 3 , 0.04–0.08 Al  apfu ), Fe (0.6–1.6 wt. % Fe 2 O 3 , 0.02–0.04 Fe  apfu ), REE (La to Lu + Y; ≤4.8 wt. % REE 2 O 3 , ≤ 0.06 REE  apfu ), and Nb (up to 0.5 wt. % Nb 2 O 5 , ≤0.01 Nb  apfu ). Fluorine content is up to 0.5 wt. % (0.06 F  apfu ). The compositional variations indicate the following principal substitutions in titanite: REE 3+  + Fe 3+  = Ca 2+  + Ti 4+ , 2REE 3+  + Fe 2+  = 2Ca 2+  + Ti 4+ , and (Al, Fe) 3+  + (OH, F) −  = Ti 4+  + O 2− . The U–Pb SHRIMP dating of titanite reveal their Variscan ages in an interval of 351.0 ± 6.5 to 337.9 ± 6.1 Ma (Tournaisian to Visean); titanite U–Pb ages are thus ~5 to 19 Ma younger than the primary magmatic zircon of the host rocks. The Zr-in-titanite thermometry indicates a relatively high temperature range of titanite precipitation (~650–750 °C), calculated for assumed pressures of 0.2 to 0.4 GPa and  a (TiO 2 ) = 0.6–1.0. Consequently, the textural, geochronological and compositional data indicate relatively high-temperature, most probably early post-magmatic (subsolidus) precipitation of titanite. Such titanite origin could be connected with a subsequent Variscan tectono-thermal event (~340 ± 10 Ma), probably related with younger small granite intrusions and/or increased fluid activity. Moreover, some titanite crystals show partial alteration and formation of secondary titanite (depleted in Fe and REE) + allanite-(Ce) veinlets (Sihla tonalite, Veporic Unit), which probably reflects younger Alpine (Cretaceous) tectono-thermal overprint of the Variscan basement of the Western Carpathians.

geologica carpathica

Titanite composition and SHRIMP U–Pb dating as indicators of post-magmatic tectono-thermal activity: Variscan I-type tonalites to granodiorites, the Western Carpathians