Resumen
Serpentinites in the La Cabaña area are part of the Western Series of the Coastal Range Metamorphic Basament of the IX Region, Chile. They consist of partially to completely serpentinized coarse grain dunites. Chromite occurs as an accessory mineral in the serpentinites, where it is variably altered to ferrichromite. In contrast, chromites found in chromitites at Centinela Bajo, have preserved their original composition with only minor alteration, and can thus be used as petrotectonic indicators. Values of 'chromium number' (#Cr-Cr/Cr+Al) in the range of 0.65-0.90 and 'magnesium number' (#Mg=Mg/Mg+Fe+2) in the range of 0.40-0.70, suggest an island arc environment for the emplacement of the peridotites.