Skip to main content

Fragmentation, injection, flow, mingling and mixing of diorite, tonalite and granite magma in a regional stress field: the Abbartello late-Variscan magmatic suite in southern Corsica

In the Variscan Batholith of Corsica large-scale, variably trending magmatic flow patterns are developed with steep magmatic foliation. This pattern is intensified by magmatic layering, mainly km-long lenses and layers of mafic and intermediate intrusions in the granitoids. Fabrics on the macro- to micro-scale indicate magma mingling and mixing. This reflects the complex intrusion history and the compositional variability of the Corsica Batholith on various scales.

At Abbartello, north of Golfe de Valinco (southern Corsica) in an area of at least 100 km2 diorite, tonalite and granite form alternating layers and lenses from several hundred meter down to millimeter thickness. Together with aligned platy feldspars, amphibole and biotite, these layers represent a flow foliation that results from several pulses of fragmentation, magma injection and mingling. Deformation of magma is indicated by boudinage, melt-injected micro shear zones, fragmenting and pseudo-folding with axial-plane parallel alignment of amphibole and biotite. The intensity of grain alignment roughly correlates with the thicknesses of layers. Weak sub-solidus deformation is indicated by chessboard subgrain patterns in magmatic quartz and by rare, up to 1 mm large, recrystallized plagioclase and amphibole grains.

Anisotropy and variable intensity of crystal alignment, together with melt-present fragmentation are interpreted as variations of flow intensity and strain-rate. The repeated injections of mafic to felsic magma and crystallization in the presence of a regional stress field reflect large-scale movements during late-Variscan crustal reorganization and represent an excellent example of localization of deformation into magma-enriched parts of the continental crust.

Details

Author
Jörn H. Kruhl1, Ron H. Vernon2, Ivan Zibra3, Santu Biswas4
Institutionen
1School of Engineering and Design, Technische Universität München, Germany; 2School of Natural Sciences, Macquarie University, Sydney, Australia; 3Geological Survey and Resource Strategy Division, East Perth, Australia; 4Department of Geology & Geophysics, Indian Institute of Technology, Kharagpur, India
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/rtfr-9682