Abstract
We present structural data from a Variscan magmatic complex of dominantly lamprophyric (kersantite) and associated felsic (microgranodiorite) sheets - the West Armorican swarm (WAS) - injected into Paleozoic metasedimentary series at the western extremity of a transpressional system in the Armorican belt, Western France. The comparative structural analysis of nearly 100 individual intrusive sheets and their host-rocks demonstrates that the WAS complex is a syntectonic magmatic structure which intruded during the onset of regional shortening via successive pulses alternating with three strain episodes (D1-D2-D3). The moderate/high dipping attitude of a great majority of intrusions, along with their prominent orientation parallel to the regional cleavage (S1), i.e. orthogonal to the direction of shortening, challenge theoretical predictions about magma-filled fractures in contractional settings. These apparently atypical features are reconciled in a kinematic model which emphasizes the influence of both host-rock planar anisotropies (S1 cleavage and D3 shear patterns) and structural inheritance on magma pathways, and instead hypothesizes the negligible role of the ambient stress field. Comparisons are attempted with syncollisional lamprophyre systems present in the European Variscides, and more especially in the SE Bohemian massif.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
