OREGON STATE UNIVERSITY

Stop 20: La Torta

La Torta

22°27.503'S, 67°58.547'W

 

 

To the southwest of the Tatio geothermal fields lies the Tocopuri volcanic complex. The name Tocopuri refers to the large composite cone that sits on the border of Chile and Bolivia. To the west of this cone lies La Torta, which was the focus of our stop here. True to its name, La Torta is in fact another “torta” shaped lava dome with steep sides, a flat top and small talus field surrounding the base.  La Torta is moderately sized at 5km3 in volume. An age estimate of less than 1 million years has been reported to the Tocopuri system with La Torta being slightly younger.

 

(((PICTURE NEEDED!!!)))

 

La Torta is dacite to rhyolite in composition and like all the lava domes of the area is extremely crystal rich, generally over 60%. Mineralogically, La Torta contains phenocrysts of Quartz, Plagioclase, hornblende and biotite in a glassy matrix.

 

Petrographic and mineralogic details