HR: 0800h
AN: V51A-0326    [Abstracts]
TI: Keeping Track of the Selenide zoo. A Combined Optical Microscopy - EPMA Study of Complex Selenides
AU: * Schlothauer, T
EM: Thomas.Schlothauer@mineral.tu-freiberg.de
AF: Freiberg University Institute of Mineralogy, Brennhausgasse 14, Freiberg, D-09596, Germany
AU: Renno, A D
EM: Axel.Renno@mineral.tu-freiberg.de
AF: Freiberg University Institute of Mineralogy, Brennhausgasse 14, Freiberg, D-09596, Germany
AU: Heide, G
EM: Gerhard.Heide@mineral.tu-freiberg.de
AF: Freiberg University Institute of Mineralogy, Brennhausgasse 14, Freiberg, D-09596, Germany
AB: Hunting for new mineral phases is a fascinating scientific activity. This kind of research not only serves the replenishment of mineralogy textbooks with new mineral names but also the industry with new potential semiconductors, laser crystals and other 'high-tech phases'. Chemical analyses using the electron microprobe are an essential intermediate step in the course of the description of a new mineral. The study of a great number of different Cu-Pb-Ag-As-Hg-Tl-Sb-Bi-Cd selenides from the former uranium deposit Schlema-Alberode (Saxony) in the German part of the Erzgebirge represented a twofold challenge to us. The complex genetic and age relations of the ore minerals and gangue minerals entailed the development of very complex microstructures in a tight space. Typical features are symplectitic intergrowths, exsolutions, fine lamellae, zoned crystals and the development of pseudo- and paramorphs. Altogether we found 34 different selenide, sulfide and arsenide minerals, including 6 dimorpheous phases. Many of these minerals are indistinguishable by electron-optical methods used during different stages of the study. Dimorpheous minerals like bellidoite and berzelianite are as much indistinguishable like intergrowths of the minerals berzelianite, mgriite and lollingite using backscattered and secondary electron images. Optical microscopy is the key to overcome these problems. We show that the step-by-step combination of polarized light microscopy, phase contrast microscopy and differential interference contrast microscopy using transmitted and reflected light allowed a secure discrimination of the different minerals and unknown phases. 16 elements are incorporated into these phases either as main, minor or trace elements. A multitude of overlapping peaks, potenzial fluorescence effects caused by adjacent phases and different matrices in the minerals demanded the development of several specific methods optimized for the analysis of Pb-Se-, Cu-Tl-Se-, Cu-Fe-Zn-As-Se-, Hg-Pb-Ag-Se-, and arsenide phases. The electron microprobe studies will be followed by EBSD, TEM and crystal structure determination by X-ray diffraction using ultra-small amounts of material taken with the help of a New Wave micromill.
DE: 1034 Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424)
DE: 1065 Major and trace element geochemistry
DE: 1094 Instruments and techniques
DE: 3616 Hydrothermal systems (0450, 1034, 3017, 4832, 8135, 8424)
DE: 3665 Mineral occurrences and deposits
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting