Analcime phenocrysts in igneous rocks: primary or secondary?

The origin of analcime phenocrysts in volcanic rocks is problematic. Are they primary minerals crystallized directly from melts or are they secondary minerals formed from preexisting igneous minerals, such as leucite? To address this question, stable isotope (H, N, O), electron microprobe, and ion microprobe data has been obtained for analcime-bearing samples from the Crowsnest Formation in Canada and the Colima volcanic complex in Mexico. Isotopic ratios were obtained for the framework (δ¹⁸O_f) and the channel water (δ¹⁸O_cw, δD) for two Crowsnest samples and one Colima sample. Collectively our data for the Crowsnest and Colima samples favor a secondary origin for analcime in these rocks. -from Authors