Hey all you etymology freaks...can anyone enlighten me as to the origin of the term "pseudosection", or as to its proper usage. The term is currently in common usage to describe P-T or T-X assemblage stability diagrams drawn for specific bulk compositions (e.g. Powell, et al., 1998, JMG, 557-588). The context here is a diagram that outlines the fields in which a particular mineral assemblage is stable, and lines on the diagram are defined where the mode of one phase is zero. Many authors refer to Hensen (1971; CMP, 33, 191-214) as the originator of these types of diagrams, and he does, indeed, seem to have published the first such diagram (his Fig. 8), but he doesn't (that I can find) ever use the word "pseudosection". Alan Thompson (1976; AJS, 276 401-424) uses the term "pseudo-binary diagram" to describe T-X or P-X sections drawn at a constant Al content (reference the AFM diagram). As I understand it, he used the term "pseudo" because the diagram is not a rigorous projection, such that crossing tie lines do not necessarily reflect reaction relationships. This usage of "pseudo" seems fine. In my dictionary, the adjective "pseudo" means "an imitation intended to deceive or mislead" (i.e. fake, counterfeit, spurious, bogus, phoney, false). Is this the connotation we wish for these types of diagrams? I guess I would prefer a term such as "mineral or assemblage stability diagram". Cheers to all the pedants out there. Frank ---------------------------------------------- Frank Spear Professor and Chair Department of Earth and Environmental Sciences, JRSC 1C25 Rensselaer Polytechnic Institute Troy, New York 12180 Phone (office): 518-276-6103 (lab) : 518-276-4899 Fax: 518-276-6680 http://www.rpi.edu/dept/geo/spear/spear.html