Tectono-magmatic characteristics of post-collisional magmatism: Case study East Carpathians, Călimani-Gurghiu-Harghita volcanic range

Abstract

This work provides a comprehensive GIS mapping integrated with geological and geophysical data (magnetic and gravimetric) to reveal the interplay between (i) magmatism and volcanic activity, (ii) intra-mountain basin development and (iii) large-scale faulting/tectonic features in the post-collisional setting of the East Carpathians. The geological, geophysical and tectonic data of the Călimani-Gurghiu-Harghita range (CGH) confirm the contemporaneous formation of basins and volcanic activity. The two phenomena propagated southwards in time, parallel to the collisional front, in close relation to the development of the fault systems. The geometry of the faults and alignment of volcanic edifices indicate both strike-slip and normal faulting, with no rotation. The main volcanic range and main tectonic basins evolved along a regional NNW-SSE striking sinistral transtensional fault zone with left stepping stepovers and pull-apart basins in the transfer areas. The fault zones probably acted as least resistance areas that fostered the development of magma ascent paths and plumbing systems. These connected the volcanic centers with numerous magma chambers emplaced at the upper mantle – lower crust boundary and throughout the lower and upper crust. The magma generation is most likely a result of the interplay between large-scale transtensional systems that induced decompression in the previously metasomatised mantle, and asthenosphere upwelling in the post-collisional East Carpathian orogen.