Fish Canyon Tuff Explained

Fish Canyon Tuff eruption
Date:About 28 million years ago
Location:Colorado, United States
Coordinates:37.7564°N -106.9342°W
Vei:8

The Fish Canyon Tuff is the large volcanic ash flow or ignimbrite deposit resulting from one of the largest known explosive eruptions on Earth, estimated at .[1] (see List of largest volcanic eruptions). The Fish Canyon Tuff eruption was centred at the La Garita Caldera in southwest Colorado; the caldera itself would have formed by collapse, as a result of the eruption. Studies of the tuff show that it all belongs to one eruption due to its uniform bulk-chemical composition (SiO2=bulk 67.5–68.5% (dacite), matrix 75–76% (rhyolite) and consistent phenocryst content (35–50%) and mineralogical composition (plagioclase, sanidine, quartz, biotite, hornblende, sphene, apatite, zircon, Fe-Ti oxides are the primary phenocrysts). This tuff and eruption is part of the larger San Juan volcanic field[2] and the Oligocene Southern Rocky Mountain ignimbrite flare-up.[3]

The Fish Canyon Tuff eruption occurred around 28 Million years ago. Sanidine crystals from the Fish Canyon Tuff (FCTs) are used as a reference mineral in 40Ar-39Ar dating, and the current 'astronomically calibrated' age for the FCTs is 28.175 Ma.[4]

See also

References

  1. https://academic.oup.com/petrology/article/43/8/1469/1483725
  2. Web site: Geologic map of the central San Juan caldera cluster, southwestern Colorado. Peter W.. Lipman. December 7, 2006. 10.3133/i2799 . pubs.er.usgs.gov.
  3. Oligo-Miocene mafic intrusions of the San Juan Volcanic Field, southwestern Colorado, and their relationship to voluminous, caldera-forming magmas. Ethan T.. Lake. G. Lang. Farmer. May 15, 2015. Geochimica et Cosmochimica Acta. 157. 86–108. ScienceDirect. 10.1016/j.gca.2015.02.020. 2015GeCoA.157...86L .
  4. Revised astronomically calibrated 40Ar/39Ar ages for the Fish Canyon Tuff sanidine – Closing the interlaboratory gap. D.. Phillips. E. L.. Matchan. H.. Dalton. K. F.. Kuiper. May 20, 2022. Chemical Geology. 597. 120815. ScienceDirect. 10.1016/j.chemgeo.2022.120815. 2022ChGeo.59720815P . 247563968 .