TY - JOUR
T1 - Petrology of monogenetic volcanoes, Mount Bailey area, Cascade Range, Oregon
AU - Barnes, Calvin G.
N1 - Funding Information:
This project was the result of the author's MSc thesis research, which was suggested and guided by A.R. McBirney. Comments on the original manuscript by Mac, B.H. Baker, M.A. Kays, and D. Bostok were of great help in clarifying the geology and the text, as were discussions with J.L. Ritchey, C.M. White, and T.L. Robyn. The manuscript was improved by interestingly disparate reviews by C.R. Bacon and R.M. Conrey. Field support was provided by Sigma Xi and the student research fund of
Funding Information:
the Geology Dept., Univ. of Oregon. Analyses were supported by NSF grants to McBirney and to Barnes (EAR-8720141) and by the DOE Reactor Sharing Program at Oregon State University.
PY - 1992/9
Y1 - 1992/9
N2 - The Mt. Bailey area encompasses the contact between Western Cascade and High Cascade volcanic rocks in southern Oregon. Western Cascade rocks are represented by a thick stack of magnetically reversed lavas and intercalated laharic deposits (the "Devils Canyon sequence") that range in composition from calc-alkaline basalt to andesite. The oldest (magnetically reversed) rocks of the High Cascade sequence formed two small andesitic shield volcanoes and, in the northern part of the area, several intracanyon flows of high-alumina olivine tholeiite (HAOT). These eruptions were followed by formation of a basaltic shield volcano (Sherwood Butte) and then by the eruption of andesitic lavas to form Mt. Bailey, and basaltic andesite which formed the adjacent cone of Garwood Butte. The Devils Canyon lavas are enriched in total Fe, total alkalis, K2O, P2O5, and TiO2 relative to the High Cascade lavas. High Cascade lavas display calc-alkaline affinities (e.g., enrichment of large-ion lithophile element and light rare earth elements) except for the intracanyon HAOT, which has trace-element characteristics typical of MORB. Rb/Zr ratios suggest that calc-alkaline lavas from each of the High Cascade volcanoes represent distinct episodes of partial melting. The source of the calc-alkaline magmas was probably mantle enriched by fluids derived from subducted oceanic crust, whereas the source of the HOAT was depleted mantle similar to the source of MORB.
AB - The Mt. Bailey area encompasses the contact between Western Cascade and High Cascade volcanic rocks in southern Oregon. Western Cascade rocks are represented by a thick stack of magnetically reversed lavas and intercalated laharic deposits (the "Devils Canyon sequence") that range in composition from calc-alkaline basalt to andesite. The oldest (magnetically reversed) rocks of the High Cascade sequence formed two small andesitic shield volcanoes and, in the northern part of the area, several intracanyon flows of high-alumina olivine tholeiite (HAOT). These eruptions were followed by formation of a basaltic shield volcano (Sherwood Butte) and then by the eruption of andesitic lavas to form Mt. Bailey, and basaltic andesite which formed the adjacent cone of Garwood Butte. The Devils Canyon lavas are enriched in total Fe, total alkalis, K2O, P2O5, and TiO2 relative to the High Cascade lavas. High Cascade lavas display calc-alkaline affinities (e.g., enrichment of large-ion lithophile element and light rare earth elements) except for the intracanyon HAOT, which has trace-element characteristics typical of MORB. Rb/Zr ratios suggest that calc-alkaline lavas from each of the High Cascade volcanoes represent distinct episodes of partial melting. The source of the calc-alkaline magmas was probably mantle enriched by fluids derived from subducted oceanic crust, whereas the source of the HOAT was depleted mantle similar to the source of MORB.
UR - http://www.scopus.com/inward/record.url?scp=0027095087&partnerID=8YFLogxK
U2 - 10.1016/0377-0273(92)90137-3
DO - 10.1016/0377-0273(92)90137-3
M3 - Article
AN - SCOPUS:0027095087
SN - 0377-0273
VL - 52
SP - 141
EP - 156
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
IS - 1-3
ER -