Cathodoluminescence, Raman and scanning electron microscopy with energy dispersion system mapping to unravel the mineralogy and texture of an altered CaAl‐rich inclusion in Renazzo CR2 carbonaceous chondrite. (5th September 2021)

• Record Type: Journal Article
• Authors: Tribaudino, Mario; Bersani, Danilo; Mantovani, Luciana; Pizzati, Mattia; Salviati, Giancarlo
• Is Part Of: Journal of Raman spectroscopy. Volume 52:Number 11(2021)
• Page Start: 1892
• Page End: 1901
• Publication Date: 2021-09-05
• Subjects: CaAl‐rich inclusions -- cathodoluminescence -- photoluminescence -- Raman mapping -- SEM‐EDS; Raman spectroscopy -- Periodicals; 535.846
• DOI: 10.1002/jrs.6234
• Languages: English
• ISSNs: 0377-0486

Abstract

Abstract: An altered fluffy type A CaAl‐rich inclusion in the CR2 Renazzo carbonaceous chondrite was examined by combined Raman, scanning electron microscopy with energy dispersion system (SEM‐EDS) and cathodoluminescence (CL) mapping. Blue CL at 450 nm and orange emission at 600 nm were related to anorthite and calcite, respectively. Raman spectra were highly fluorescent, and only the stronger peaks of anorthite, clinopyroxene and calcite were observed. Raman‐induced fluorescence emission was measured using the 632‐nm Raman laser source, up to 850 nm, and used to chart the mineral phases. A fluorescence structured peak at 690 nm, split in three subpeaks at 678, 689 and 693 nm, was found; it is likely related to the fluorescence emission of Cr 3+ from a fassaitic pyroxene in anorthite. Secondary pyroxene in the Wark–Lovering rim does not show the peak at 690 nm; the different fluorescence emission from the secondary rim and the pyroxene patches within anorthite could be a marker to spot the primary pyroxene. From combined imaging, the events in the altered chondrite could be sequenced. Starting from a pristine assemblage of spinel and melilite, with little fassaite, several alteration episodes occurred. Alteration in secondary anorthite, which could be mapped by the blue CL emission at 450 nm, was followed by alkalization, with rims of sodalite and nepheline, and subsequent formation of secondary clinopyroxene, encircling the inclusion. Widespread calcite alteration, present also in the matrix between chondrules, was the last recorded event. Abstract : The altered structure of a CaAl inclusion is unraveled by means of combined SEM‐EDS, cathodoluminescence and Raman mapping. Raman mapping was done using the Raman and the photoluminescence emission. The complementary nature of cathodoluminescence and photoluminescence emission was highlighted.