Among the elements which are potentially useful as geochemical tools, chlorine is an ubiquitous candidate, since it constitutes a window on the fluid-rock interactions in the Earth. Due to its volatile character, however, Cl cannot be measured in solid samples by flame or ICP atomic spectrometry. Cl contents higher than tens of ppm are nowadays generally obtained by INAA or EMPA. The SIMS procedure developed at CNR-IGG (PAVIA) for Cl analysis, which relies on 12.5-kV 16O¬ primary beam, energy-filtered (75-125 eV) secondary ions of both isotopes 35Cl+ and 37Cl+, and 30Si+ (as the inner standard) under the 25-?m imaged field, has been optimized to measure low Cl concentrations (ppm level) in silicates, and applied to peridotite minerals. It allows the concomitant detection of light, alkaline, alkaline-earth, HFS and RE elements at the same micro-spot. In this work we report and discuss the SIMS data for Cl obtained on upper-mantle peridotites (previously characterized in terms of light and trace elements, Ottolini et al. 2004) and on a new suite of xenoliths from Massif Central. Preliminary results indicate that the pyrolite contains between 5 and 10 ppm Cl, in the lower range of literature data. Main minerals of depleted peridotites (ol, opx, cpx) host 2-5 ppm Cl, but sp contents are below the SIMS detection limits. In general, the distribution of Cl appears to be very homogeneous in minerals with "primary" geochemical overprints (composition, texture) contrary to metasomatized phases, in which Cl contents can vary by two orders of magnitude at a very small scale. Our SIMS data confirm the highly-incompatible character of Cl in the peridotite-basalt systems. Reference Ottolini L., Le Fèvre B. And Vannucci R., (2004), Earth Planet. Sci. Lett. 228, 19-36.
SIMS analysis of chlorine at low contents in silicates: a new tool for upper-mantle geochemical studies
Ottolini L
2005
Abstract
Among the elements which are potentially useful as geochemical tools, chlorine is an ubiquitous candidate, since it constitutes a window on the fluid-rock interactions in the Earth. Due to its volatile character, however, Cl cannot be measured in solid samples by flame or ICP atomic spectrometry. Cl contents higher than tens of ppm are nowadays generally obtained by INAA or EMPA. The SIMS procedure developed at CNR-IGG (PAVIA) for Cl analysis, which relies on 12.5-kV 16O¬ primary beam, energy-filtered (75-125 eV) secondary ions of both isotopes 35Cl+ and 37Cl+, and 30Si+ (as the inner standard) under the 25-?m imaged field, has been optimized to measure low Cl concentrations (ppm level) in silicates, and applied to peridotite minerals. It allows the concomitant detection of light, alkaline, alkaline-earth, HFS and RE elements at the same micro-spot. In this work we report and discuss the SIMS data for Cl obtained on upper-mantle peridotites (previously characterized in terms of light and trace elements, Ottolini et al. 2004) and on a new suite of xenoliths from Massif Central. Preliminary results indicate that the pyrolite contains between 5 and 10 ppm Cl, in the lower range of literature data. Main minerals of depleted peridotites (ol, opx, cpx) host 2-5 ppm Cl, but sp contents are below the SIMS detection limits. In general, the distribution of Cl appears to be very homogeneous in minerals with "primary" geochemical overprints (composition, texture) contrary to metasomatized phases, in which Cl contents can vary by two orders of magnitude at a very small scale. Our SIMS data confirm the highly-incompatible character of Cl in the peridotite-basalt systems. Reference Ottolini L., Le Fèvre B. And Vannucci R., (2004), Earth Planet. Sci. Lett. 228, 19-36.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
