%0 Journal Article
%T The earliest low and high 汛18O caldera-forming eruptions of the Yellowstone plume: implications for the 30每40 Ma Oregon calderas and speculations on plume-triggered delaminations
%A Angela N. Seligman
%A Ilya N. Bindeman
%A Jason McClaughry
%A Richard A. Stern
%J Frontiers in Earth Science
%D 2014
%I Frontiers Media
%R 10.3389/feart.2014.00034
%X We present new isotopic and trace element data for four eruptive centers in Oregon: Wildcat Mountain (40 Ma), Crooked River (32每28 Ma), Tower Mountain (32 Ma), and Mohawk River (32 Ma). The first three calderas are located too far east to be sourced through renewed subduction of the Farallon slab following accretion of the Yellowstone-produced Siletzia terrane at ~50 Ma. Basalts of the three eastern eruptive centers yield high Nb/Yb and Th/Yb ratios, indicating an enriched sublithospheric mantle source, while Mohawk River yields trace element and isotopic (汛18O and 汍Hf) values that correlate with its location above a subduction zone. The voluminous rhyolitic tuffs and lavas of Crooked River (41 ℅ 27 km) have 汛18Ozircon values that include seven low 汛18Ozircon units (1.8每4.5㏑), one high 汛18Ozircon unit (7.4每8.8㏑), and two units with heterogeneous zircons (2.0每9.0㏑), similar to younger Yellowstone-Snake River Plain rhyolites. In order to produce these low 汛18O values, a large heat source, widespread hydrothermal circulation, and repeated remelting are all required. In contrast, Wildcat Mountain and Tower Mountain rocks yield high 汛18Ozircon values (6.4每7.9㏑) and normal to low 汍Hfi values (5.2每12.6), indicating crustal melting of high-汛18O supracrustal rocks. We propose that these calderas were produced by the first appearance of the Yellowstone plume east of the Cascadia subduction zone, which is supported by plate reconstructions that put the Yellowstone plume under Crooked River at 32每28 Ma. Given the eastern location of these calderas along the suture of the accreted Siletzia terrane and North America, we suggest that the Yellowstone hotspot is directly responsible for magmatism at Crooked River, and for plume-assisted delamination of portions of the edge of the Blue Mountains that produced the Tower Mountain magmas, while the older Wildcat Mountain magmas are related to suture zone instabilities that were created following accretion of the Siletzia terrane.
%K Yellowstone plume
%K oxygen isotopes
%K hafnium isotopes
%K Oregon
%K calderas
%K delamination
%U http://www.frontiersin.org/Journal/10.3389/feart.2014.00034/abstract