Phenocryst compositions of late ash-flow tuffs from the central San Juan caldera cluster
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Phenocryst compositions of late ash-flow tuffs from the central San Juan caldera cluster results from Creede drill-hole samples and implications for regional stratigraphy by

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Published by U.S. Dept. of the Interior, U.S. Geological Survey in [Denver, Colo.] .
Written in English


  • Volcanic ash, tuff, etc. -- Colorado -- Creede Region,
  • Phenocrysts -- Colorado -- Creede Region,
  • Boring -- Colorado -- Creede Region,
  • Creede Formation (Colo.)

Book details:

Edition Notes

Statementby Peter W. Lipman, Patricia E. Weston
SeriesPreliminary scientific results of the Creede caldera Continental Scientific Drilling Program, Open-file report -- 94-260-B, U.S. Geological Survey open-file report -- 94-260-B
ContributionsWeston, Patricia E, Bethke, Philip Martin, 1930-, Geological Survey (U.S.), U.S. Continental Scientific Drilling Program
The Physical Object
Pagination43 p.
Number of Pages43
ID Numbers
Open LibraryOL13630568M

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Central San Juan region Central San Juan tuffs Fish Canyon Tuff 22 Carpenter Ridge Tuff 22 Lava flows, S-central San Juans 83 References: Askren, D.R., , Origin of andesites interlayered with large-volume ash-flow tuffs in the western United States: PhD dissertation, University of Georgia, pp. Recurrent eruption and subsidence at the Platoro caldera complex, southeastern San Juan volcanic field, Colorado: New tales from old tuffs August Geological Society of America Bulletin (8. In conjunction with integrated mapping of the Oligocene central San Juan caldera cluster, southwestern Colorado (USGS I-Map , in press), all modern chemical analyses of volcanic rocks for this area determined in laboratories of the U.S. Geological Survey have been re-evaluated in terms of the stratigraphic sequence as presently understood.   The Fish Canyon Tuff is one of the largest currently recognized ash-flow tuffs (> km 3). It is a crystal-rich quartz latite containing about 40 per cent phenocrysts of plagioclase, sanidine, biotite, hornblende, quartz, magnetite, sphene, and ilmenite. Pyrrhotite occurs as inclusions in magnetite, sphene, and by:

A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber/reservoir in a volcanic eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is lost. The ground surface then collapses downward into the emptied or partially emptied magma chamber, leaving a massive . The western Nevada volcanic field is the western third of a belt of calderas through Nevada and western Utah. Twenty-three calderas and their caldera-forming tuffs are reasonably well identified in the western Nevada volcanic field, and the presence of at least another 14 areally extensive, apparently voluminous ash-flow tuffs whose sources are unknown suggests a similar number Cited by: The Pagosa Peak Dacite is an unusual pyroclastic deposit that immediately predated eruption of the enormous Fish Canyon Tuff (~ km3) from the La Garita caldera at 28 Ma. The Pagosa Peak Dacite is thick (to 1 km), voluminous (> km3), and has a high aspect ratio () similar to those of silicic lava flows. It contains a high proportion (%) of juvenile clasts (to m) . The Fish Canyon Tuff, erupted from the La Garita caldera, is the second and largest of eight major ash-flow sheets erupted from the productive central San Juan caldera cluster, which generated approximately km 3 of silicic deposits through eight caldera-related eruptions during Cited by:

The Caetano Tuff in north-central Nevada is one of the volumetrically largest manifestations of vigorous mid-Tertiary (ca. 43–19 Ma) magmatism dominated by voluminous caldera-forming ash flow eruptions (Lipman et al., ; Best et al., ; Christiansen and Yeats, ).Carlin-type gold deposits in northern Nevada, which are among the largest gold deposits in the world and Cited by: A continuum of glass and phenocryst compositions occurs within the Topopah Spring and Rainier Mesa sheets. Variations in phenocryst compositions with FeOt are generally consistent with those expected for crystallization within magma reservoirs characterized by vertical thermal and compositional by: Geology and petrogenesis of ash-flow tuffs and rhyolitic lavas associated with the Gila Cliff Dwellings basin-Bursum caldera complex, southwestern New Mexico: Publication Type: Book: Authors: Seaman, SJ: Year: Keywords: Calderas – New Mexico – Mogollon Mountains, Geology – New Mexico, Petrogenesis – New Mexico, Volcanic ash - tuff.   Nd, Sr and O isotopic data were obtained from silicic ash-flow tuffs and lavas at the Tertiary age (16–9 Ma) Timber (Mountain/Oasis Valley volcanic center (TMOV) in southern Nevada, to assess models for the origin and evolution of the large-volume silicic magma bodies generated in this region. The large-volume (> km3), chemically-zoned, Topopah Spring Cited by: