Kinematic markers III: Extension Nodes

Standard
Columnar basalts at Racoșul de Jos/ Alsórákos are yielding a 1200 ka to 600 ks old (Harangi et al., 2013)  effusive product in one of the  Perșani Mountain tension nodes, tracing the location of cross-cutting strike-slip  faults

Columnar basalts at Racoșul de Jos/ Alsórákos are yielding a 1200 ka to 600 ka old (Harangi et al., 2013) effusive product in one of the Perșani Mountain tension nodes, tracing the location of cross-cutting strike-slip faults

In the GSST approach, rising of magmas is related to the opening of crustal scale tension fractures. Because pure shear related stress field and deformation is unlikely to exist in nature, even within compressional belts there will exist some transtensional fracture components, which are characterized by significantly lower stress values. These tension fractures always form perpendicularly to the σ3 direction, and will serve as pathways for rising of magmas.

Cross-cutting fault systems are quite common in nature. While in regional compressional fault intersections stress nodes may form, in tensional fault intersections, extension nodes may appear. Here, in these extension nodes magmas have the highest chance to rich to the surface. As a consequence, volcanic craters are the best markers of regional extension nodes. In addition to volcanic craters, other parts of the volcanic build-ups may also serve as passive kinematic indicators, because of the pronounced hardness and brittleness of lavas and volcano sedimentary successions, in comparison to the surrounding environment.

Example: Columnar basalts at Racoșul de Jos/ Alsórákos are yielding a Pleistocene, 1200 ka to 600 ks old (Harangi et al., 2013) effusive product in one of the Perșani Mountain tension nodes, tracing the location of cross-cutting strike-slip faults.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.