Just over the pass near Linsor dome and to the east of the Chao complex and Cerro Lean, we come across Chillahuita, yet another large silicic lava dome. Like Chanka and many of the domes yet to come, Chillahuita has the “torta” shape often exhibited by these large domes - flat tops and steep sides with some talus around the flanks.
Along with close proximity, Chillahuita has many similar characteristics to Chao, it is thought to be nearly contemporaneous in age and contains similar texture and mineralogy. It does, however, differ to Chao in that it was build on a much more gentle slope, and thus is smaller in size – 5 km3 in volume.
Petrographic and Mineralogic details
Like most of the domes we have seen, and will see, Chillahuita is dacitic in composition and extremely rich in crystals (50%+). Mineralogically, the phenocrysts consist of plagioclase, quartz, hornblende, and sphene. The texture, like Chao, is friable due to microvesiculation of the matrix.