It is similar to El Rojo Norte260 kilometres (160mi) farther north. A mafic andesite lava flow was erupted from the 100 metres (330ft) high cone that also features red scoria. Ages obtained by potassium-argon dating are 2.93±0.13, 3.4±0.4 and 3.23±0.12 mya.
Rojo Sur erupted undifferentiated mafic magmas. Its lead isotope composition is different from the composition of that segment of the Andes, being non-radiogenic. This isotope signature may be the effect of assimilation of deeper basement rocks during magma formation. In addition, the magmas are rich in incompatible elements.
References
1234Wigger, edited by Klaus-Joachim Reutter, Ekkehard Scheuber, Peter J. (1994). "Large- and Fine-Scale Geochemical Variations Along the Andean Arc of Northern Chile (17.5°– 22°S)". Tectonics of the Southern Central Andes Structure and Evolution of an Active Continental Margin. Berlin, Heidelberg: Springer Berlin Heidelberg. pp.81–83. doi:10.1007/978-3-642-77353-2_5. ISBN978-3-642-77353-2. {{cite book}}: |first1= has generic name (help)CS1 maint: multiple names: authors list (link)