Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Rougvie, J. R. Articles by Sorensen, S. S. Search for Related Content GeoRef GeoRef Citation

Cathodoluminescence record of K-metasomatism in ash-flow tuffs: Grain-scale mechanisms and large-scale geochemical implications

¹ Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560-0119, USA

Near-surface, low-temperature, K-metasomatism of rhyolitic to dacitic ash-flow tuffs is a volumetrically and petrologically significant feature of the western United States and may be a primary alteration path in arid lands. Cathodoluminescence (CL) petrography of K-metasomatized ash-flow tuffs quickly yields information about the mineralogical changes and reaction mechanisms that take place during alteration for large sample suites and links these properties to geochemical changes. Tertiary volcanic rocks from Creede (Colorado), Socorro (New Mexico), and the Harcuvar Mountains (Arizona), were altered in different geologic settings, yet have very similar CL textures and chemistry. Original igneous feldspars were replaced by adularia primarily by dissolution and crystallization that occurred preferentially along preexisting fractures, surfaces, compositional zoning features, and cleavages. Fluid flow was primarily along grain boundaries, but was in some cases inhomogeneous at the thin-section scale.

Key Words: alteration • ash-flow tuff • cathodoluminescence • feldspar • Tertiary