RESEARCH ARTICLE Can crystallization of olivine tholeiite give rise to potassic rhyolites?—an experimental investigation Matthew L. Whitaker & Hanna Nekvasil & Donald H. Lindsley & Michael McCurry Received: 1 August 2005 / Accepted: 8 March 2007 / Published online: 20 June 2007 # Springer-Verlag 2007 Abstract Experiments were conducted to determine whether the rhyolites and basalts of the intraplate silica- saturated potassic suites could be genetically related through crystallization. Extreme crystallization (96–97%) of a high-MgO (10.62 wt%) olivine tholeiite from the Snake River Plain with an initial bulk water content of 0.4 wt% at a mid-crustal pressure of 4.3 kbar generated potassic rhyolitic liquids similar in major element chemistry to those found in the Quaternary rhyolite domes of the Snake River Plain and their plutonic equivalents in the Proterozoic Laramie Anorthosite Complex. Residual liquids comparable in composition to the bulk rock compositions of intermediate rocks found at the Craters of the Moon and Cedar Butte eruptive centers in the Snake River Plain are also generated along this crystallization path. Keywords Crystallization . Differentiation . Potassic rhyolites . Experimental . Snake River Plain . Tholeiite . Basalt Introduction Rhyolites and granites of continental intraplate magmatic regimes are commonly spatially and temporally associated with a variety of mafic and intermediate rocks that share specific compositional characteristics. These shared char- acteristics have provided the foundation for systematizing the diversity of intra-plate magmatic rock associations into several series (Nekvasil 1998; Nekvasil et al. 2000, 2003). Characteristic of the silica-saturated potassic series (i.e., the continental tholeiitic series of Nekvasil et al. 2000) is the presence of potassic rhyolite/granite in addition to tholeiitic basalt/gabbro. Volcanic suites in this series include those of the hotspot-related large igneous prov- inces (e.g., Yellowstone–Snake River Plain volcanic province) which form the sequence tholeiitic basalt– ferrobasalt–trachybasalt–trachyandesite–trachyte (tristan- ite)–potassic rhyolite (Frost and Frost 1997; Leeman et al. 1976; McCurry et al. 1999, this issue; Stout et al. 1994), or, more commonly, bimodal basalt/potassic rhyo- lite associations. Plutonic suites within this series consist of the non-cumulate rocks of the massif anorthosite complexes (Frost et al. 1993, 1999; Scoates et al. 1996) which follow the sequence olivine gabbro–ferrodiorite (jotunite) –monzodiorite–monzonite–monzosyenite–sye- nite–potassic granite (Fig. 1). Figure 1 shows the characteristic variation in total alkalis vs silica in rocks of the silica-saturated potassic series, Bull Volcanol (2008) 70:417–434 DOI 10.1007/s00445-007-0146-1 This paper constitutes part of a special issue dedicated to Bill Bonnichsen on the petrogenesis and volcanology of anorogenic rhyolites. Editorial responsibility: E. Christiansen M. L. Whitaker (*) : H. Nekvasil : D. H. Lindsley Department of Geosciences, Stony Brook University, Stony Brook, NY 11794-2100, USA e-mail: matthewlwhitaker@aim.com H. Nekvasil e-mail: hanna.nekvasil@sunysb.edu D. H. Lindsley e-mail: dlindsley@notes.cc.sunysb.edu M. McCurry Department of Geology, Idaho State University, Pocatello, ID 83209, USA e-mail: mccumich@isu.edu