Accurate correction for the matrix interference on laser ablation MC-ICPMS boron isotope measurements in CaCO3 and silicate matrices

Knowledge of the boron isotopic composition of natural samples has found wide ranging application in both low and high temperature geochemistry. More recently, the development of boron isotope measurements using...

Rapid determination of the original boron isotopic composition from altered basaltic glass by in situ secondary ion mass spectrometry

Rapid determination of the original boron composition from altered basaltic glass by SIMS boron isotopic profile analysis from the core to rim.

Regulation of calcification site pH is a polyphyletic but not always governing response to ocean acidification

The response of marine-calcifying organisms to ocean acidification (OA) is highly variable, although the mechanisms behind this variability are not well understood. Here, we use the boron isotopic composition (δ11B) of biogenic calcium carbonate to investigate the extent to which organisms’ ability to regulate pH at their site of calcification (pHCF) determines their calcification responses to OA. We report comparative δ11B analyses of 10 species with divergent calcification responses (positive, parabolic, threshold, and negative) to OA. Although the pHCF is closely coupled to calcification responses only in 3 of the 10 species, all 10 species elevate pHCF above pHsw under elevated pCO2. This result suggests that these species may expend additional energy regulating pHCF under future OA. This strategy of elevating pHCF above pHsw appears to be a polyphyletic, if not universal, response to OA among marine calcifiers—although not always the principal factor governing a species’ response to OA.

Insights into B-Mg-Metasomatism at the Ranger U Deposit (NT, Australia) and Comparison with Canadian Unconformity-Related U Deposits

The Ranger deposit (Northern Territory, Australia) is one of the largest uranium deposits in the world. Uranium mineralisation occurs in crystalline basement rocks and is thought to belong to the unconformity-related category. In order to address the sources of magnesium and boron, and the temperature of the fluids related to boron and magnesium metasomatism that occurred shortly before and during the main uranium stage, in situ analyses of chlorite and tourmaline were carried out. The chemical composition of tourmaline shows an elevated X-site vacancy and a low Fetot/(Fetot + Mg) ratio typical of Mg-foitite. Uranium-related chlorite has relatively low Fe content (0.28–0.83 apfu) and high Mg content (3.08–3.84 apfu), with Si/Al = 1.08−1.22 and Mg/(Mg + Fetot) = 0.80−0.93 indicating a composition lying between the clinochlore and Mg-amesite fields. Chlorite composition indicates crystallisation temperature of 101–163 °C. The boron isotopic composition of tourmaline shows a range of δ11B values of ~1–9‰. A model is proposed involving two boron sources that contribute to a mixed isotopic signature: (i) evaporated seawater, which is typically enriched in magnesium and boron (δ11B ~ 40‰), and (ii) boron from the crystalline basement (δ11B ~ −30 to +10‰), which appears to be the dominant source. Collectively, the data indicate similar tourmaline chemistry but significant differences of tourmaline boron isotopic composition and chlorite chemistry between the Ranger deposit and some of the Canadian unconformity-related uranium deposits. However, lithogeochemical exploration approaches based on identification of boron- and magnesium-enriched zones may be usefully applied to uranium exploration in the Northern Territory.