Isotopic and trace element characteristics of rhyolites from the Valles Caldera, New Mexico. Final technical report

Self, S.; Sykes, M. L.; Wolff, J. A.; Skuba, C. E.

doi:10.2172/10189843

Cited by 1 publication

(9 citation statements)

References 16 publications

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“…The LBT consists almost entirely of high-silica rhyolite of constant major element composition with pronounced variations in minor and trace elements (Table V2), accom panied by phenocryst contents from 7.5 to 19.5% (Self et al, 1991). In proximal sections, these variations are systematic from first-erupted to last-erupted units, and closely mimic element zoning patterns seen in the Bishop Tuff (Hildreth, 1979) and other high-silica rhyolites (Fig.…”

Section: Geochemistry Of the Bandelier Tuffmentioning

confidence: 52%

“…Determination of the age of these units has proved difficult; the published 40 Ar/ 39 Ar ages on the El Cajete, Battleship Rock, and Banco Bonito units range from 0.5 to 0.2 Ma (Spell and Harrison, 1993). Self et al (1991) suggest that an eruption at about 300 ka produced the El Cajete-Battleship Rock-VC1 rhyolite units, and that a slightly later eruption at about 200-150 ka yielded the Banco Bonito lava and associated pyroclastic rocks. This scenario is supported by 40 Ar/ 39 Ar ages of Spell and Harrison (1993), see Table V1, but a new study has suggested an age of about 60 ka for these units (Wolff and Gardner, 1995).…”

Section: Valles Rhyolites and Associated Depositsmentioning

confidence: 92%

“…Mafic pumice occurs as a trace component in the LBT; it is most abundant in banded pumice clasts found in pumice swarms at the base of the lowest flow unit at Stop 3. Neodymium and strontium isotopic data indicate these pumice clasts originate by mixing of the LBT high-silica rhyolite with basement Proterozoic granite and by assimilation and melting of Precambrian country rock into the LBT magma shortly before or during the eruption (Self et al, 1991).…”

Section: Geochemistry Of the Bandelier Tuffmentioning

confidence: 99%

“…Eruptions of tephra and rhyolite domes in the caldera moat last occurred at about 0.2 Ma (Self et al, 1991;Spell and Harrison, 1993), or perhaps as young as 60 ka (Wolff and Gardner, 1995); hydrothermal activity persists to the present day. The system must still be considered active.…”

Section: Jemez Mountains Stratigraphymentioning

confidence: 99%

“…The two Bandelier ignimbrites and their associated Plinian deposits resulted from eruptions of zoned magma systems (Smith and Bailey, 1966), with compositions from high-to low-silica rhyolite. Detailed descriptions of their geochemistry can be found in Self et al (1991) and Dunbar and Hervig (1992).…”

Section: Geochemistry Of the Bandelier Tuffmentioning

confidence: 99%

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Field excursions to the Jemez Mountains, New Mexico

Self¹,

Heiken²,

Sykes³

et al. 1996

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Published as public domain, therefore reproducible without permission. Source credit requested.iii Preface This bulletin has been compiled from the field guides for two complementary and somewhat unconventional trips offered as part of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI) General Assembly in Santa Fe, New Mexico, in June, 1989. One, a Field Workshop of the IAVCEI Commission on Explosive Volcanism, was pre-assembly trip 11WA to study ignimbrites and calderas of the Jemez Mountains, New Mexico, and the San Juan Mountains, Colorado. Only the New Mexico part of the original Field Workshop Handbook has been rewritten and updated here for this publication. The original Workshop Handbook was not prepared as a standard geologic road guide but more as a series of volcanologic explanations of individual outcrops, showing how each contributes to the overall picture of ignimbrite eruption and caldera evolution in the Jemez Mountains. Some minor stop omissions, stop sequence changes, and simplifications from the original 11WA Workshop Handbook have been made in this version to improve the field guide's general appeal.The field guide for White Rock Canyon was prepared for a 1-day-long trip to look at maar volcanoes along the Rio Grande. It is an unusual trip in that travel is by rubber raft. There are no odometer readings or road signs-descriptions are linked to side canyons along the Rio Grande. If you have your own raft, kayak, or canoe and know how to use it, you are ready to take this trip, which begins at Otowi Bridge along NM-4 (a permit is required from the main office of San Ildefonso Pueblo) or from Buckman Crossing, which is reached from Santa Fe (no permit required). Most rafters continue through White Rock Canyon to the boat docks at Cochiti Reservoir, where you leave the river. Plan for a very long day or camp along the river overnight. If you want to take the trip and have no way to float down the river, several of the northern New Mexican rafting companies occasionally have float trips through White Rock Canyon.On the raft trip, if you leave White Rock Canyon via the Frijoles (Upper Falls) trail, you are in Bandelier National Monument. Take no samples and pay an entry fee at Monument Headquarters (if someone is picking you up, they will have already paid the fee at the entrance).A few points should be borne in mind when following these field guides. Both trips present some degree of physical challenge, as the rafting and scaling of ignimbrite cliffs, while not requiring special preparation or equipment, are perhaps a little more demanding than usual field trip routes. Weather is another consideration for these trips, especially in the higher elevations of the Jemez Mountains. Unless it is an exceptionally precipitation-free winter, snow and harsh weather conditions are likely to prevail between November and March at many of the stops in the multi-day field guide, and bad snow storms can close much of the area as late as May.Access for the geologist on foot a...

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Section: Geochemistry Of the Bandelier Tuffmentioning

confidence: 52%

Section: Valles Rhyolites and Associated Depositsmentioning

confidence: 92%

Section: Geochemistry Of the Bandelier Tuffmentioning

confidence: 99%

Section: Jemez Mountains Stratigraphymentioning

confidence: 99%