A simple model for sector zoning in slowly grown crystals; implications for growth rate and lattice diffusion, with emphasis on accessory minerals in crustal rocks

Abstract

Other| December 01, 1995 A simple model for sector zoning in slowly grown crystals: Implications for growth rate and lattice diffusion, with emphasis on accessory minerals in crustal rocks E. Bruce Watson; E. Bruce Watson Rensselaer Polytechnic Institute, Department of Earth and Environmental Sciences, Troy, NY, United States Search for other works by this author on: GSW Google Scholar Yan Liang Yan Liang Search for other works by this author on: GSW Google Scholar American Mineralogist (1995) 80 (11-12): 1179–1187. https://doi.org/10.2138/am-1995-11-1209 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation E. Bruce Watson, Yan Liang; A simple model for sector zoning in slowly grown crystals: Implications for growth rate and lattice diffusion, with emphasis on accessory minerals in crustal rocks. American Mineralogist 1995;; 80 (11-12): 1179–1187. doi: https://doi.org/10.2138/am-1995-11-1209 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract The occurrence of sector zoning in minerals of regional metamorphic or low-temperature intrusive origin implies that rapid growth is not required for the development of this particular form of homogeneous disequilibrium. It is shown here that sector zoning can be a natural consequence simply of slow lattice diffusion. Given anisotropic surface enrichment coupled with the low difFusivities typical of highly charged elements in refractory accessory minerals such as zircon and titanite, sector zoning can arise even in cases of growth rates as low as a few micrometers per million years. According to the proposed model, the development of sector zoning depends upon the competition between growth rate (V) and lattice diffusion (Di) within the near-surface layer (l), such that above a critical value of Vl/Di (~0.5–3), sector zoning is unavoidable in crystals that exhibit selective enrichment on some growth surfaces. Known diffusivities of rare earth elements in zircon and titanite lead to the expectation of sector zoning in these minerals with respect to REEs for reasonable geologic growth rates. Even in the case of clinopyroxene, diffusion of REEs and high field-strength elements may be slow enough to contribute to the development of sector zoning in laboratory-grown crystals. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.