The Yellowstone hotspot in space and time: Nd and Hf isotopes insilici magmas
Over the course of its 16 m.y. history, the Yellowstonehotspot has produced silicic magmas exhibiting systematic, and oftensympathetic, variations in isotopic and chemical composition, temperatureand frequency of eruption. Nd and Hf isotopic ratios vary systematicallyfrom initial eruptions at ~;16 Ma, contemporaneous with basalticvolcanism in eastern Oregon and Washington, to the present dayYellowstone Volcanic Plateau. Nd and Hf isotopic ratios co-vary and spanthe range of most terrestrial samples, reflecting mixing of mantle andcrustal sources. Earliest erupted silicic magmas were hot (in excess of1050oC), relatively less evolved and have isotopic ratios within therange of contemporaneous Columbia River flood basalts. The transit of thehotspot across the lithospheric boundary between the western accretedoceanic terrain and the Precambrian craton at 15 Ma is marked by shiftsin eNd from +4 to -11 and in ?Hf from +10 to -10. The duration of thetransit yields a crustal magma source diameter of ~;70 km. In theinterval from 14 to 9 Ma, ?Nd systematically increases from -11 to -7,recording a minimum increase in the mantle component from 5 percent to 30percent. The mantle component could be twice as great, depending upon theisotopic composition of crust and mantle reservoirs. In this sameinterval, peak temperatures of ~;1000oC occurred at 9 Ma. The last 8 m.y.are characterized by less frequent eruption of lower temperature(830-900oC) and more compositionally evolved magmas.
- Research Organization:
- COLLABORATION - University of Utah, Dept. ofGeology and Geophysics
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 901508
- Report Number(s):
- LBNL-60528; EPSLA2; R&D Project: 468202; TRN: US200714%%74
- Journal Information:
- Earth and Planetary Science Letters, Vol. 247, Issue 1-2; Related Information: Journal Publication Date: 06/09/2006; ISSN 0012-821X
- Country of Publication:
- United States
- Language:
- English
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