Geochemistry of high-potassium rocks from the mid-Tertiary Guffey volcanic center, Thirtynine Mile volcanic field, central Colorado

Journal Article · Sun Jul 01 00:00:00 EDT 1990 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1990)018<0642:GOHPRF>2.3.CO;2· OSTI ID:6140437

Wobus, R A; Mochel, D W ^[1]; Mertzman, S A; Eide, E A; Rothwarf, M T ^[2]; Loeffler, B M; Johnson, D A ^[3]; Keating, G N; Sultz, K ^[4]; Benjamin, A E ^[5]; Venzke, E A ^[6]; Filson, T ^[7]

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1. Williams College, Williamstown, MA (USA)
2. Franklin Marshall College, Lancaster, PA (USA)
3. Colorado College, Colorado Springs (USA)
4. Carleton College, Northfield, MN (USA)
5. Smith College, Northampton, MA (USA)
6. Beloit College, WI (USA)
7. Whitman College, Walla Walla, WA (USA)

The Guffey volcanic center is the largest within the 2000 km{sup 2} mid-Tertiary Thirtynine Mile volcanic field of central Colorado. This study is the first to provide extensive chemical data for these alkalic volcanic and subvolcanic rocks, which present the eroded remnants of a large stratovolcano of Oligocene age. Formation of early domes and flows of latite and trachyte within the Guffey center was followed by extrusion of a thick series of basalt, trachybasalt, and shoshonite flows and lahars. Plugs, dikes, and vents ranging from basalt to rhyolite cut the thick mafic deposits, and felsic tuffs breccias chemically identical to the small rhyolitic plutons are locally preserved. Whole-rack major and trace element analyses of 80 samples, ranging almost continuously from 47% to 78% SiO{sub 2}, indicate that the rocks of the Guffey center are among the most highly enriched in K{sub 2}O (up to 6%) and rare earth elements (typically 200-300 ppm) of any volcanic rocks in Colorado. These observations, along with the relatively high concentrations of Ba and Rb and the depletion of Cr and Ni, suggest an appreciable contribution of lower crustal material to the magmas that produced the Thirtynine Mile volcanic rocks.

• OSTI ID: 6140437
• Journal Information: Geology; (USA), Vol. 18:7; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COLORADO
VOLCANIC REGIONS
GEOCHEMISTRY
BARIUM
BASALT
CHEMICAL ANALYSIS
CHROMIUM
CONTINENTAL CRUST
DIKES
ENRICHMENT
EROSION
EXTRUSION
MAGMA
MIXING
MULTI-ELEMENT ANALYSIS
NICKEL
POTASSIUM OXIDES
RARE EARTHS
RHYOLITES
RUBIDIUM
SILICON OXIDES
SOLIDS FLOW
TERTIARY PERIOD
TRACE AMOUNTS
TUFF
VOLCANIC ROCKS
ALKALI METAL COMPOUNDS
ALKALI METALS
ALKALINE EARTH METALS
CENOZOIC ERA
CHALCOGENIDES
CHEMISTRY
EARTH CRUST
ELEMENTS
FABRICATION
FEDERAL REGION VIII
FLUID FLOW
GEOLOGIC AGES
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
MATERIALS WORKING
METALS
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
ROCKS
SILICON COMPOUNDS
TRANSITION ELEMENTS
USA
580000* - Geosciences