SERPENTINITES AND CHROMITITES FROM LA CABANA, COASTAL RANGE OF CENTRAL CHILE

Serpentinites in the La Cabana area are part of the Western Series of the Coastal Range Metamorphic Basement of the IX Region, Chile. They c onsist 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 composit ion 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 0.4 0-0.70, suggest an island are environment for the emplacement of the p eridotites.