Honglin Yuan

This study compared boron (B) isotopic compositions of six chemically diverse tourmalines (including schorl, dravite, and elbaite types) using 257 nm femtosecond (fs) and 193 nm nanosecond (ns) laser ablation coupled with multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). Significant matrix effects were observed when non-matrix-matched standards were used, leading to δ¹¹B deviations of −0.70‰ to −0.41‰ for fs-LA and −0.63‰ to −0.57‰ for ns-LA when using dravite GIGT as a bracketing standard for schorl (TOUR1 and TOUR4) and elbaite (TOUR6). In contrast, using GIGT as the matrix-matched bracketing standard in the B analysis of dravites (TOUR2, TOUR3, and TOUR5) yielded significantly lower deviations of −0.22‰ to −0.18‰ for fs-LA and −0.44‰ to 0.12‰ for ns-LA. These findings necessitate matrix-matched standards for precise and accurate in situ measurements of B isotopes. We characterized four natural tourmaline reference materials (TOUR1, TOUR4, TOUR5, and TOUR6) for in situ B isotope analysis using LA-MC-ICP-MS and confirmed their isotopic homogeneity. The measured mean δ¹¹B values were −11.14 ± 0.40‰ (2SD, n = 597), −13.42 ± 0.57‰ (2SD, n = 509), −9.09 ± 0.60‰ (2SD, n = 486), and −8.57 ± 0.17‰ (2SD, n = 164), respectively, agreeing well with those obtained by solution nebulizer (SN)-MC-ICP-MS. Thus, schorl (TOUR1 and TOUR4), dravite (TOUR5), and elbaite (TOUR6) are recommended as candidate matrix-matched tourmaline reference materials for in situ B isotope determination.

Three synthesized solid blocks (pyrite NWU-Py, gypsum NWU-Gy and arsenopyrite NWU-Apy) using the fast-hot-pressing sintering method (FHP) have been identified as potential reference materials for in situ sulfur isotope analysis by LA-MC-ICP-MS.

We developed a new method for in situ measurement of Mo stable isotope ratios using femtosecond laser ablation coupled with MC-ICP-MS. Additionally, experiments were conducted on nine natural molybdenite samples from different ore deposits in China.

Analyzing sulfur (S) and molybdenum (Mo) isotope ratios in molybdenite, the most common sulfide mineral, is crucial for studying the genesis of ore deposits. However, it is necessary to prepare matrix-matched reference materials for molybdenite. In this study, we employed two different techniques, the high-temperature-high-pressure (HTHP) technique and the rapid hot-pressing technique, to synthesize molybdenites and assessed their suitability as reference materials for in situ Mo and S isotope analysis in molybdenite. The molybdenites synthesized through HTHP and rapid hot-pressing exhibit smooth surfaces and dense structures, making them suitable as reference materials for in situ Mo and S isotope analysis, respectively. These synthesized molybdenites exhibit homogeneous Mo and S isotope compositions based on a large number of LA-MC-ICP-MS measurements. The mean δ⁹⁸Mo_{NIST SRM 3134} values of 0.70 ± 0.06‰ (n = 4, 2SD) and 0.70 ± 0.05‰ (n = 4, 2SD) determined by solution nebulization MC-ICP-MS are suggested as recommended δ⁹⁸Mo/⁹⁵Mo values for Mo-H8 and Mo-P. The mean δ³⁴S_V-CDT value of −0.22 ± 0.10‰ (n = 9, 2SD) determined by elemental analyzer isotope ratio mass spectrometry (EA-IRMS) is suggested as a recommended δ³⁴S/³²S value for Mo-H8 and Mo-P. Therefore, we recommend combining ultrafine powders with a high-temperature–high-pressure technique and/or a rapid hot-pressing technique to synthesize reference materials for isotopic analysis of other minerals.