Osumilite, a New Mineral, and Cordierite in Volcanic Rocks

Miyashiro, Akiho

doi:10.2183/pjab1945.29.321

Cited by 9 publications

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“…A few accessory fragments of intensely welded cordierite-bearing tuff were observed in ash-flow tuff that otherwise has no cordierite and is only weakly chloritized and epidotized. Primary cordierite or the cordieritelike mineral osumilite occur in some peraluminous lavas (Miyashiro, 1953(Miyashiro, , 1956, and it may be that the so-called cordierite in the Elkhorn Mountains Volcanics actually is osumilite and of primary magmatic origin. Or perhaps the cordierite was produced by thermal metamorphism of older welded tuff in the vent of the younger ash-flow eruption.…”

Section: Rhyolite Ash Flowsmentioning

confidence: 99%

Geology and igneous petrology of the northern Elkhorn Mountains, Jefferson and Broadwater Counties, Montana

Smedes¹

1966

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The northern Elkhorn Mountains comprise an area of about 132 square miles in west-central Montana. The area includes parts of four major geologic units : ( 1) in the northern part, a narrow belt of folded and faulted upper Paleozoic and Mesozoic sedimentary rocks more than 5,700 feet thick; (2) in the eastern part, a folded and faulted sequence of Upper Cretaceous volcanic rocks more than 11,500 feet thick, and related intrusive rocks ; ( 3) in the western part and near the northeastern corne-r, plutonic rocks of the Boulder batholith, with small bodies Of Tertiary igneous rocks cutting and resting upon them ; and ( 4) along the northern edge, poorly consolidated and unconsolidated deposits df ash, tuff, and gravel of Tertiary and Quaternary age.

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Section: Rhyolite Ash Flowsmentioning

confidence: 99%