Average composition of selected incompatible trace elements in obsidians collected from sources in northern Hokkaido [map].  The composition was determined using energy dispersive x-ray fluorescence (EDXRF) on freshly broken nodules. The standard deviation is listed in red for each element.  bdl= below detection limit.

The locations were determined using a differential GPS.  Coordinates were not obtained for Tokachiishikawa due to obstructing vegetation and the narrowness of the river gorge.  The samples from Tokachimitsumata were obtained from the Hokkaido Bunkazai Center.

Separation of the sources can be seen in the bivariate plots of the incompatible elements.  The Akashiyama outcrop and summit have the same trace element chemistry; these two sources overlap in the plots below.  All the other sources separate from each other.

For more details on this study, read the artcile Hall, M. and Kimura, H., "Quantitative EDXRF Studies of Obsidian Sources in Northern Hokkaido", in JOURNAL OF ARCHAEOLOGICAL SCIENCE.  The article is courtesy of Academic Press, Inc.