Origin and age of the Eisenkappel gabbro to granite suite (Carinthia, SE Austrian Alps)

• Published in: Lithos Vol. 125; no. 1-2; pp. 434 - 448
• Main Authors: Miller, C., Thöni, M., Goessler, W., Tessadri, R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.07.2011; Elsevier B.V. [etc.]
• Subjects: Data assimilation; Eastern Alps; Eisenkappel; Gabbro; Magma mixing; Plutonic suite; Sr–Nd correlation; Austria, Alps Mts; Magma mixing; Eisenkappel; Gabbro; Sr–Nd correlation; Plutonic suite; Eastern Alps
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2011.03.003

The northern part of the Karawanken plutonic belt is a gabbro–granite complex located just north of the Periadriatic lineament near the Slovenian–Austrian border. Petrographic and geochemical studies of the Eisenkappel intrusive complex indicate that this multiphase plutonic suite developed by a combination of crystal accumulation, fractional crystallization and assimilation processes, magma mixing and mingling. The mafic rocks are alkaline and have within-plate geochemical characteristics, indicating anorogenic magmatism in an extensional setting and derivation from an enriched mantle source. The mafic melts triggered partial melting of the crust and the formation of granite. The granitic rocks are alkalic, metaluminous and have the high Fe/Fe+Mg characteristics of within-plate plutons. Temperature and pressure conditions, derived from amphibole-plagioclase and different amphibole thermobarometers, suggest that the analysed Eisenkappel gabbros crystallized at around 1000±20°C and 380–470MPa, whereas the granitic rock crystallized at T≤800±20°C and≤350MPa. Mineral-whole rock Sm–Nd analyses of two cumulate gabbros yielded 249±8.4Ma and 250±26Ma (εNd: +3.6), garnet-whole rock Sm–Nd analyses of two silicic samples yielded well-constrained ages of 238.4±1.9Ma and 242.1±2.1Ma (εNd: −2.6). ► The Northern Karawanken Plutonic Belt includes gabbros, intermediate and felsic rocks. ► The alkaline gabbros (Nd: +3.6) crystallized at 1000±20°C and 380-470MPa. ► Intermediate and felsic rocks crystallized at T ≤800±20°C and ≤350MPa. Sm-Nd mineral-whole rock dating of two gabbros yielded 249±8.4Ma and 250±26Ma. ► Grt-whole rock Sm-Nd ages of two silicic samples are 238.4±1.9Ma and 242.1±2.1Ma.