Abstract

The scanning electron microscope (SEM) provides a powerful new tool for the study of daughter minerals in fluid inclusions, particularly when the instrument is equipped with a solid-state X-ray detector. The general character and abundance of inclusions is first established by conventional optical study of polished plates of the host crystal. These plates or other pieces of the same material are cleaned and then opened by chipping or cleaving. Under the SEM, open inclusions appear as pits in the newly broken surfaces. Upon enlargement, daughter crystal morphology is revealed in great detail and the electron beam produces characteristic X-ray spectra of the daughter mineral which are collected by an energy dispersive detector and visually displayed on a multichannel analyzer. The resulting chemical and morphological information, coupled with previous optical observations, defines or greatly limits the possible identity of the daughter mineral.Three applications of the SEM technique are presented in this paper. The method is first applied to complex inclusions in fluorite of the Emmett mine. Jamestown, Colorado, in which nine previously unidentified daughter minerals were found. Dawsonite [NaAl(CO 3 )(OH) 2 ] is confirmed as a daughter precipitate in inclusions in gold-quartz veins of the Oriental mine, Alleghany, California. Finally, the SEM is used to identify daughter minerals in both magmatic and hydrothermal inclusions from the carbonatite at Magnet Cove, Arkansas.

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