Intrusion of shoshonitic magmas at shallow crustal depth: T–P path, H2O estimates, and AFC modeling of the Middle Triassic Predazzo Intrusive Complex (Southern Alps, Italy)

Casetta, F., Coltorti, M., Ickert, R. B. , Bonadiman, C., Giacomoni, P. P. and Ntaflos, T. (2018) Intrusion of shoshonitic magmas at shallow crustal depth: T–P path, H2O estimates, and AFC modeling of the Middle Triassic Predazzo Intrusive Complex (Southern Alps, Italy). Contributions to Mineralogy and Petrology, 173, 57. (doi: 10.1007/s00410-018-1483-0)

Abstract

The multi-pulse shoshonitic Predazzo intrusive complex represents an ideal igneous laboratory for investigating the chemical and physical conditions of magma emplacement in a crustal context, since numerical models can be constrained by field evidence. It constitutes the most intriguing remnant of the Middle Triassic magmatic systems of the Dolomitic Area (Southern Alps), preserved by the Alpine tectonics. Predazzo Intrusive Complex comprises silica saturated (pyroxenites/ gabbros to syenites), silica undersaturated (gabbros to syenites), and silica oversaturated (granites and syenogranites) rock suites. In this paper, we modeled its emplacement and evolution with a multiple thermo-/oxy-barometric, hygrometric, and EC-AFC approach. At odds with what proposed in literature but according to the field evidence, the emplacement of the Predazzo Intrusive Complex occurred at shallow depth (<6 km). In this context, the different pulses differed slightly in bulk water content, but shared a common thermal regime, with temperatures between 1000 and 1100 °C and ~ 600 °C at low-to-moderate oxidizing conditions (− 0.1 to +0.7 ΔFMQ). The interaction between the intrusion and the shallow crustal rocks was minimal, with Sr and Nd isotopic compositions indicating an average of 5–6% assimilation of crust. A thermoand oxy-barometric comparison with the nearby Mt. Monzoni also enabled to speculate about the solidification time of the intrusion, which we infer took place over about 700 ka.

• Item Type: Articles
• Additional Information: The IUSS Mobility Research Programme of the University of Ferrara, grant n. 570 for Long Period, 2016 (FC), and The Italian National Research Program PRIN_2015/prot. 20158A9 (CB) supported this research.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ickert, Dr Ryan
• Authors: Casetta, F., Coltorti, M., Ickert, R. B., Bonadiman, C., Giacomoni, P. P., and Ntaflos, T.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Contributions to Mineralogy and Petrology
• Publisher: Springer
• ISSN: 0010-7999
• ISSN (Online): 1432-0967
• Published Online: 22 June 2018
• Copyright Holders: Copyright © 2018 Springer Verlag
• First Published: First published in Contributions to Mineralogy and Petrology 173:57
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher