Cerro Ratones is a partly eroded

andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained ( aphanitic) to porphyritic in texture, and is composed predomi ...

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and p ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, t ...

, in the eastern edge of the Puna. The Diablillos-Galán fault zone intersects a volcanic lineament named Archibarca-Ratones beneath the volcano. The age of the volcano is equivocal;

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but ...

ages of 30±3

mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...

are found but one

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more alum ...

was dated by Argon-argon dating to be about 7 mya old. Both dates come from lava flows; the older date would make this volcano one of the oldest in the area. Toconquis group ignimbrites crop out next to the Ratones edifice. The Ojo de Ratones system is located northeast of Cerro Ratones and the Galan giant caldera in the south.

References

Oligocene volcanoes Stratovolcanoes of Argentina {{Volcanology-stub