Sodalite-group minerals (SGM) are Na- and Ca-bearing feldspathoids which can contain chlorine, reduced or oxidized sulfur, and water or hydroxyl groups as extraframework volatile species. The most widespread members are sodalite Na8Al6Si6O24Cl2, nosean Na8Al6Si6O24SO4, haüyne Na6Ca2Al6Si6O24Cl2, and lazurite Na8Al6Si6O24S. SGM typically occur in undersaturated alkaline igneous rocks, and in some hydrothermal and metamorphic rocks. SGM are of interest for the study of magmatic systems, and their volatile components can be useful because they can provide key information on the genetic environment, like degassing dynamics and fluids behavior during hydrothermal processes. Besides, SGM are very promising in different fields of material science, due to their particular (ultra)microporous structures (Bellatreccia et al., 2009). The present study is focused on crystal-chemical characterization of cationic and anionic components of SSG occurring in various igneous to metamorphic rocks and ejecta from Somma-Vesuvius volcano (southern Italy), deriving form the collection of Mineralogical Museum (Univ. Napoli Federico II). Detailed electron probe microanalysis (EPMA), secondary ion mass spectrometry (SIMS) and Fourier transform infrared microspectroscopy (?-FTIR) investigations have been carried out on thirty-nine samples, ranging from metamorphic and magmatic xenoliths to lavas related to different eruption times. Microbeam techniques, as SIMS and ?-FTIR, are of key importance to probe trace to ultra-trace contents and speciations of volatiles (Bellatreccia et al., 2009; Ottolini et al., 2006). Our investigations show that the studied SGM correspond to sodalite, nosean (here referred as sulfatic sodalite) and haüyne. SIMS measurements on H, F and C show contents: 0.02 - 5.0 wt.% H2O, 0.01 - 0.14 wt.% F, and 0.69 - 2.95 wt.% CO2. Within the single crystals, F is always very low, whereas concentrations of H2O and, to a lesser extent, CO2 can vary from homogeneous to strongly inhomogeneous. ?-FTIR spectra of SGM can be grouped into sodalites and sulphatic sodalites/haüynes, according to the occurrence of the 12CO2 absorption at 2340 cm-1. The absorption due to H2O and/or OH groups occurs as a very broad band (3700 cm-1 - 3000 cm-1). In all samples FTIR data show the presence of CO32-. Homogeneous vs. inhomogeneous distribution of H and C was also revealed by ?-FTIR focal plane array imaging, which shows an antithetical distribution of CO2 and especially of H2O, in agreement with the SIMS results. The collected data allow us to fully characterize SGM from Somma-Vesuvius, providing also with some constraints about their genesis. Bellatreccia F., Della Ventura G., Piccinini M., Cavallo A. & Brilli M. 2009. H2O and CO2 in minerals of the haüynesodalite group: an FTIR spectroscopy study. Mineral. Mag., 73, 399-413. Ottolini L., Cámara F. & Hawthorne F.C. 2006. Strategies for quantification of light elements in minerals by SIMS: H, B and F. Microchim. Acta, 155, 229-233.
Sodalite-group minerals from Somma-Vesuvius volcano (southern Italy): an EPMA, SIMS and FTIR study
Ottolini L;
2015
Abstract
Sodalite-group minerals (SGM) are Na- and Ca-bearing feldspathoids which can contain chlorine, reduced or oxidized sulfur, and water or hydroxyl groups as extraframework volatile species. The most widespread members are sodalite Na8Al6Si6O24Cl2, nosean Na8Al6Si6O24SO4, haüyne Na6Ca2Al6Si6O24Cl2, and lazurite Na8Al6Si6O24S. SGM typically occur in undersaturated alkaline igneous rocks, and in some hydrothermal and metamorphic rocks. SGM are of interest for the study of magmatic systems, and their volatile components can be useful because they can provide key information on the genetic environment, like degassing dynamics and fluids behavior during hydrothermal processes. Besides, SGM are very promising in different fields of material science, due to their particular (ultra)microporous structures (Bellatreccia et al., 2009). The present study is focused on crystal-chemical characterization of cationic and anionic components of SSG occurring in various igneous to metamorphic rocks and ejecta from Somma-Vesuvius volcano (southern Italy), deriving form the collection of Mineralogical Museum (Univ. Napoli Federico II). Detailed electron probe microanalysis (EPMA), secondary ion mass spectrometry (SIMS) and Fourier transform infrared microspectroscopy (?-FTIR) investigations have been carried out on thirty-nine samples, ranging from metamorphic and magmatic xenoliths to lavas related to different eruption times. Microbeam techniques, as SIMS and ?-FTIR, are of key importance to probe trace to ultra-trace contents and speciations of volatiles (Bellatreccia et al., 2009; Ottolini et al., 2006). Our investigations show that the studied SGM correspond to sodalite, nosean (here referred as sulfatic sodalite) and haüyne. SIMS measurements on H, F and C show contents: 0.02 - 5.0 wt.% H2O, 0.01 - 0.14 wt.% F, and 0.69 - 2.95 wt.% CO2. Within the single crystals, F is always very low, whereas concentrations of H2O and, to a lesser extent, CO2 can vary from homogeneous to strongly inhomogeneous. ?-FTIR spectra of SGM can be grouped into sodalites and sulphatic sodalites/haüynes, according to the occurrence of the 12CO2 absorption at 2340 cm-1. The absorption due to H2O and/or OH groups occurs as a very broad band (3700 cm-1 - 3000 cm-1). In all samples FTIR data show the presence of CO32-. Homogeneous vs. inhomogeneous distribution of H and C was also revealed by ?-FTIR focal plane array imaging, which shows an antithetical distribution of CO2 and especially of H2O, in agreement with the SIMS results. The collected data allow us to fully characterize SGM from Somma-Vesuvius, providing also with some constraints about their genesis. Bellatreccia F., Della Ventura G., Piccinini M., Cavallo A. & Brilli M. 2009. H2O and CO2 in minerals of the haüynesodalite group: an FTIR spectroscopy study. Mineral. Mag., 73, 399-413. Ottolini L., Cámara F. & Hawthorne F.C. 2006. Strategies for quantification of light elements in minerals by SIMS: H, B and F. Microchim. Acta, 155, 229-233.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
