Tectonic rotations and internal structure of Eocene plutons in Chuquicamata, northern Chile

RUBÉN SOMOZA; ANDREW J. TOMLINSON; CLAUDIA BEATRIZ ZAFFARANA; SILVIA E. SINGER; CARLA G. PUIGDOMENECH NEGRE; M. I. B. RAPOSO; J. H. DILLES

TECTONOPHYSICS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 654 p. 113 - 130

0040-1951

A paleomagnetic and AMS study on Eocene plutonic complexes in the Calama area, northern Chile, reveals high- temperature, high-coercivitymagnetizations of dominantly thermoremanent origin and magnetic fabrics con- trolled bymagnetite. The paleomagnetic results indicate that ~43Ma plutons underwent clockwise tectonic ro- tation,whereas adjacent ~39Ma plutons did not undergo discernible rotation. This points to a middle Eocene age for the younger tectonic rotations associated with the Central Andean Rotation Pattern in the Chuquicamata? Calama area. The petrofabric in these rocks formed under conditions ranging frompurelymagmatic (i.e. before full crystalliza- tion) to low-temperature solid-state deformation. AMS and paleomagnetism suggest that the plutonic bodies were formed by progressive amalgamation of subvertical magma sheets spanning multiple magnetic polarity chrons. The parallelism between magmatic and tectonic foliations suggests that regional tectonic stress con- trolled ascent,emplacement and rock deformation during cooling. In this context,we suggest thatmagma ascent and emplacement in the upper crust likely exploited Mesozoic structures which were locally reactivated in the Eocene.