Isotope and trace element data bearing of the sources and evolution of magmas in the Katmai region, Alaska
The Katmai volcanic province, Alaska Peninsula, includes the catastrophic 1912 Valley of Ten Thousand Smokes (VTTS) eruption, and five andesite-dacite stratovolcanoes. The VTTS is markedly uniform in /sup 143/Nd//sup 144/Nd (0.51301) and delta/sup 18/O (6.0 per thousands) but has a small but significant variation in /sup 87/Sr//sup 86/Sr (0.70354 in andesite and dacite, 0.70368 in rhyolite). The rhyolite's low Sr content (63 ppm) makes it particularly susceptible to crustal contamination; assimilation of only 1% of Jurassic country rock (0.70480, 400 ppm Sr) is sufficient. Dacite from the 1959 eruption of nearby Mt. Trident and a basalt boulder from the rim of Mt. Katmai are isotopically similar to the VTTS andesite and dacite. Dacite from Mt. Mageik has higher /sup 87/Sr//sup 86/Sr, whereas the least-silicic in situ lava in the region, an andesite from Mt. Griggs, has the lowest /sup 87/Sr//sup 86/Sr (0.70335). The Katmai Province falls within the narrow range of /sup 143/Nd//sup 144/Nd for Quaternary lavas from the Aleutians and SW Alaska Peninsula (0.51298-0.51310) but at the high end of the /sup 87/Sr//sup 86/Sr range. Along with the greater abundance of evolved lavas, this probably reflects progressively thicker crust northward along the Alaska Peninsula, although simple assimilation of upper crust cannot explain all of the isotopic data. Isotopic systematics, and Aleutian-type trace-element patterns (La/Yb > chondrites, high Ba/La), indicate that the parental magmas at Katmai are likewise derived from a time-integrated depleted mantle, recently modified by a component from the subducted slab.
- Research Organization:
- Lamont-Doherty Geologicl Observatory, Palisades, NY (USA)
- OSTI ID:
- 6317356
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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QUANTITATIVE CHEMICAL ANALYSIS
QUATERNARY PERIOD
STRONTIUM ISOTOPES
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