Origin of Ignimbrites

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

The anisotropy of magnetic susceptibility (AMS) of late Cretaceous ash-flow tuffs in Chisulryoung Volcanic Formation, southeastern Korea was studied to define the primary pyroclastic flow azimuth. AMS data revealed a dominant oblate fabric with a tight clustering of k3 (minimum axis of magnetic susceptibility) and shallow dispersal of k1 (maximum axis of magnetic susceptibility) and k2 (interme...

Paleointensity estimates from ignimbrites: An evaluation of the Bishop Tuff

A Metamodel for Crustal Magmatism: Phase Equilibria of Giant Ignimbrites

Diverse explanations exist for the large-volume catastrophic eruptions that formed the Bishop Tuff of Long Valley in eastern California, the Bandelier Tuff in New Mexico, and the tuffs of Yellowstone, Montana, USA.These eruptions are among the largest on Earth within the last 2 Myr. A common factor in recently proposed petrogenetic scenarios for each system is multistage processing, in which a ...

Curie temperatures of titanomagnetite in ignimbrites: Effects of emplacement temperatures, cooling rates, exsolution, and cation ordering

Pumices, ashes, and tuffs from Mt. St. Helens and from Novarupta contain two principal forms of titanomagnetite: homogeneous grains with Curie temperatures in the range 350–500 C and oxyexsolved grains with similar bulk composition, containing ilmenite lamellae and having Curie temperatures above 500 C. Thermomagnetic analyses and isothermal annealing experiments in combination with stratigraph...

Contrasting processes in silicic magma chambers: evidence from very large volume ignimbrites

Very large volume (>1000 km of magma) crystal-rich dacitic ignimbrites that lack pronounced evidence of fractional crystallization or vertical zonation erupt in some continental magmatic arcs (e.g. the Lund Tuff of the Great Basin and the Fish Canyon Tuff of Colorado in western USA). Apparently, their magma chambers were only modestly heterogeneous and not systematically zoned from top to botto...