Arc related Jurassic igneous and meta-igneous rocks in the Coastal Cordillera of northern Chile/Region Antofagasta

A deep section of the Jurassic, 200-150 Ma old magmatic arc is exposed in the Coastal Cordillera south of Antofagasta in northern Chile. The chemical compositions of metabasic and plutonic rocks from the deep level are compared with those of Jurassic volcanic rocks and ≈ 150 Ma old dykes. The metabasites, most of the plutonic rocks, and the dykes have calc-alkaline characteristics. However, small postmetamorphic gabbro plutons are tholeiitic. The composition of the volcanic rocks is not related to the plutonic rocks, metabasites and dykes. All igneous and meta-igneous rocks of the arc are derived from a similar source in the upper mantle and evolved without major crustal contamination.

The general tectonic setting was dominated by extension, and Pre-Jurassic crust is extremely thinned or absent in the area. Details of the tectonic, magmatic and metamorphic development remain still a matter of speculation.