Choiyoi Group
| Choiyoi Group Stratigraphic range: Permian, Triassic |
|
|---|---|
| Type | Group |
| Sub-units | Upper Choiyoi Lower Choiyoi |
| Area | >200,000 km2 |
| Thickness | 2–4 km |
| Lithology | |
| Primary | Basaltic lava flow, breccia, andesite, rhyolitic ignimbrite |
| Other | Dacite |
| Location | |
| Country | Argentina, Chile |
| Type section | |
| Named by | Stipanicic et al. (1968) |
Choiyoi Group (Spanish: Grupo Choiyoi) is a Permian and Triassic-aged group of volcano-sedimentary formations in Argentina and Chile. The group bears evidence of bimodal-style volcanism related to an ancient subduction zone that existed along the western margin of the supercontinent Gondwana.
The Choiyoi Group has a large areal extent through western Argentina and parts of Chile, covering at least 200,000 km2, but probably around 500,000 km2. While the subsurface extent of the group is large, exposures in Argentina are most common in the Frontal Cordillera, the San Rafael Massif and the Principal Cordillera of southern Mendoza and northern Neuquén. In parts the group reaches thicknesses of 2 to 4 km.
The plutonic equivalent of the Choiyoi Group volcanic material are mostly granitoids. The remnants of the magmatic arc that produced much of volcanic material is now preserved as a series of batholiths, including the Coastal Batholith of central Chile in the Chilean Coast Range. During the Permian the zone of arc magmatism moved 350 km inland from the Chilean Coast Range, reaching San Rafael about 280 million years ago.
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