Spotted on Rob Ixer's academic blog site -- from December. More on the rhyolites on the way........ not sure if the paper is fully published yet. It is available online for subscribers.
Provenancing the rhyolitic and dacitic components of the stonehenge landscape bluestone lithology: New petrographical and geochemical evidence. Bevins, Richard E. / Ixer, Rob A. / Webb, Peter C. / Watson, John S., Journal of Archaeological Science, In Press, Accepted Manuscript, Dec 2011
“Craig Rhos-Y-Felin, Pont Saeson is the dominant source of the Stonehenge rhyolitic ‘debitage’”, by RA Ixer & RE Bevins, Archaeology in Wales 50 (2011), 21–31
“Stonehenge rhyolitic bluestone sources & the application of zircon chemistry as a new tool for provenancing rhyolitic lithics”, by RE Bevins, NJP Pearce, & RA Ixer, Journal of Archaeological Sciences 38 (2011), 605–22
“The petrography, affinity and provenance of lithics from the Cursus Field, Stonehenge”, by RA Ixer & RE Bevins, Wiltshire Archaeological & Natural History Magazine 103 (2010) 1–15
“The detailed petrography of six orthostats from the bluestone circle, Stonehenge”, by RA Ixer & RE Bevins, Wiltshire Archaeological & Natural History Magazine 104 (2010), 1–14