Monazite cathodoluminescence - A new tool for heavy mineral analysis of siliciclastic sedimentary rocks

An appropriate technique to distinguish monazite from other similar minerals like zircon and xenotime is of significance in modern heavy mineral analysis since monazite occurs in sands and sandstone and may provide useful information on provenance and history of sedimentary sequences. Monazite differs from the optically very similar zircon by its dark-olive cathodoluminescence (CL) feature. The CL-spectra of monazite and zircon are dominated by characteristically narrow bands of different rare earth elements: Nd3+ and Sm3+ for monazite and mainly Dy3+ for zircon. Because of the different crystal-lattices of both minerals, the splitting of the multiplet level of equally available elements is different. High amounts of rare earth elements within monazite lead to quenching effects, so that the CL-feature visually appears very weak. Detection of monazite in heavy mineral separates from Triassic sandstones of E-Bavaria allows us to reconstruct different crystalline source areas (Bohemian Massif, Erzgebirge). Altogether, the monazites from these areas show the same CL-behaviour like those from other crystalline areas (Dora Maira Massio and from placers (Bahia/Brazil. Taiwan). These investigations underline the considerable potential of the cathodoluminescence technique for heavy mineral analysis and specifically for the distinction of minerals with similar optical properties. (C) 2008 Elsevier B.V. All rights reserved.