Zirconium and hafnium in meteorites

Abstract

Abstract– The ratio of the two refractory trace elements zirconium (Zr) and hafnium (Hf) in meteorites has been proposed to be uniform. The most precise value available is 34.3 ± 0.2 (1σ). It was obtained by isotope dilution ICP‐MS applied to 15 chondrites, most of which were carbonaceous chondrites, and six achondrites. We reinvestigated the case and determined Zr/Hf ratios of a broad spectrum of meteoritic samples via laser ablation ICP‐MS. Our sample suite comprised 29 chondrites and five achondrites. The main objective of the study was two‐fold: we intended to verify the accuracy and precision of a relatively fast and inexpensive sample preparation method combined with expeditious laser ablation ICP‐MS techniques. Furthermore, we were looking into the possibility of systematic fine‐scale Zr/Hf variations among bulk meteoritic matter of different classes. The applied fusion technique together with laser ablation ICP‐MS turned out to be well suited to determine relative refractory trace element abundances. Absolute Zr/Hf ratios yield uncertainties of approximately 4% (1σ). As opposed to the most recent findings, we observed variable Zr/Hf ratios in different meteorites ranging from approximately 28 to approximately 38. Our value for Orgueil (CI1) is 34.0 ± 0.3 (1σ). Including literature data, we propose a solar system value of 34.1 ± 0.3. Our data also suggest that H chondrites tend to exhibit higher Zr/Hf ratios (average of 35.6 ± 0.5 [1σ]) while EL6 chondrites rather show low values (average of 30.8 ± 0.6 [1σ]). In addition to examining Zr/Hf ratios, we also explored the content of refractory major elements in different meteorite groups. Here, we found that EL6 chondrites often show very low Ca/Al ratios. The CI1 value for CaO/Al2O3 is 0.804. EL6 chondrites, however, display ratios as low as approximately 0.3. While the variation in Zr/Hf can be explained by fractional condensation processes in the early solar nebula, the observed low Ca/Al ratios in EL6 chondrites are probably attributable to deficits in oldhamite (CaS).

Analysis of 60 elements in 616 ocean floor basaltic glasses

“…Zr/Hf versus Nd for (a) different tectonic settings and (b) different ocean basins. Zr/Hf in chondrite from Patzer et al [2010]. See text for discussion.…”

Chemistry and oxygen isotopic composition of cluster chondrite clasts and their components in LL3 chondrites

“…Furthermore, these chondrules show strongly elevated Zr/Hf ratios (41-61; Fig. 5), in contrast to the value of 34.4 (equal to the solar value; Patzer et al 2010) for the average of all other analyzed chondrules. Similar REE patterns and even stronger Zr/Hf fractionations (88, 123) were observed in pyroxene crystals from two porous (ferroan) pyroxene chondrules in an EH3 chondrite (Sahara 97096; Jacquet et al 2015b).…”

Description of an aerodynamic levitation apparatus with applications in Earth sciences

“…Argon gas was used because we wanted to avoid changes in oxidation state of the samples. High concentrations of ferric Fe in chondritic samples that were levitated in air led to formation of abundant <10 μm sized quenched spinel crystals [28-30]. …”

“…Pack et al [28], Pack [29] and Patzer et al [30] used aerodynamic levitation in conjunction with CO 2 laser melting as preparation technique for analyses of Ca, Y, REEs, Zr, and Hf in bulk chondrites and achondrites. The analyses were conducted using LA-ICPMS.…”

“…Details of the levitation apparatus, however, were not described by Pack et al [28], Pack [29] and Patzer et al [30] and will be presented in this contribution. It will also be demonstrated that laser-assisted melting of ~10 mg rock powders is suitable not only for refractory trace element (Y, REE, Zr, Hf), but also for bulk major and minor element analyses.…”