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Person

Peter W Lipman

Emeritus
Email: plipman@usgs.gov
Office Phone: 650-329-5295
Fax: 650-329-5203
ORCID: 0000-0001-9175-6118

Location
345 Middlefield Road
Mail Stop 910
Menlo Park , CA 94025
US
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This U.S. Geological Survey (USGS) data release provides whole rock major, minor, and trace element geochemical data and zircon U-Pb geochronology and trace element concentrations for samples from pre-ignimbrite volcanoes within the San Juan locus of the mid-Cenozoic Southern Rocky Mountain volcanic field, Colorado. Samples were collected in order to constrain the evolution of the pre-ignimbrite magmatic system.
The dataset includes whole-rock geochemistry, phenocryst/mineral trace element compositions, zircon U–Pb geochronology, and zircon in situ Lu–Hf isotopes for intrusions associated with the Oligocene Platoro caldera complex of the San Juan volcanic locus in Colorado features numerous exposed plutons, both within the caldera and outside its margins, enabling investigation of the timing and evolution of postcaldera magmatism. Intrusion and , coupled with new document distinct pulses of magma derived from different depths beneath the caldera complex. Fourteen intrusions, the Chiquito Peak Tuff, and the dacite of Fisher Gulch were dated, showing intrusive magmatism began after the 28.8 Ma-eruption of the Chiquito Peak...
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This geodatabase contains all the geologic map information for the Geologic Map of the San Juan caldera cluster, southwestern Colorado and is part of U.S. Geological Survey Geologic Investigations Map Series I-2799. The San Juan Mountains are the largest erosional remnant of a composite volcanic field that covered much of the southern Rocky Mountains in middle Tertiary time. The San Juan field consists mainly of intermediate-composition lavas and breccias, erupted about 35-30 Ma from scattered central volcanoes (Conejos Formation) and overlain by voluminous ash-flow sheets erupted from caldera sources. In the central San Juan Mountains, eruption of at least 8,800 km3 of dacitic-rhyolitic magma as nine major ash...
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