Abstract:Tourmaline, a boron-rich mineral, serves as a robust tracer for fluid-mediated geological processes due to its chemical stability and resistance to environmental influence. Here, we present a novel data reduction scheme (DRS) LCG_B.py, integrated within the Iolite 4 program for in situ boron (B) isotope analysis of tourmaline to investigate fluid activities in subduction zones. The innovative approach enables direct observation of 11B and 10B signal variation during laser ablation, while treating the 11B/10B ratios of reference materials for calibration as a fitted timeseries curve (usually using Spline AutoSmooth), facilitating automated analysis and precise calibration of B isotope ratios across specified ablation interval. Based on this, a high-precision B isotopes analysis protocol achieving spot size below 30 μm with analytical uncertainty better than 0.5 ‰ (2sd) (except Schorl (NaFe3Al6[Si6O18](BO3)3(OH)4) of 0.7 ‰) was developed. Application of this method to tourmalines in ultrahigh-pressure (UHP) eclogites from the Dabie orogen showed positive δ11B values ranging from +4.7 ± 0.2 to +10.5 ± 0.3 ‰, derivation from B-rich fluids sourced from impure marbles. The findings provide refined constraints on fluid-mediated geological processes and enhance our understanding of the complex fluid-rock interactions in the continental subduction zones. The improved analytical protocol and data processing technique establish a powerful tool for future geochemical investigations of subduction zone dynamics.

Abstract:Although various methods have been developed for total organic carbon (TOC) analysis, most of them usually consume large amounts of samples, chemicals, and energy, thus making them only suitable for laboratory analysis. In this work, a new simple liquid electrode discharge microplasma-induced vapor generation (MPI-VG) was successfully developed to efficiently convert the organic compounds contained in water into CO2 on a microfluidic chip. Consequently, the generated CO2 was separated from the liquid phase and further swept into a miniature point discharge optical emission spectrometer (μPD-OES) for the detection of total organic carbon (TOC) in water samples via monitoring the carbon atom emission at 193.0 nm. Under optimal conditions, a limit of detection of 0.15 mg L?1 (as C) was obtained for TOC with a relative standard deviation better than 3.7%. The system is environmentally-friendly and efficient, which consumes only 43 μL of sample and 60 μg oxidant for each analysis. The total analytical time can be significantly reduced to one minute. The reaction mechanism was carefully investigated using quenching tests and gas chromatography. The practicality and anti-interference capabilities of the system were verified by measuring TOC in seawater and river water. Compared to conventional methods, this system demonstrates considerable potential for miniaturization due to the compact size of the microfluidic chip-based MPI-VG and μPD-OES.

Abstract:In this study, we present the novel use of a microwave digestion system (CEM BLADE) to digest geological materials for Re-Os isotopic analysis. This technique employs quartz digestion vessels that are easy to clean and reusable, avoid the complicated steps of opening and sealing, and enable complete digestion of the samples within 30 min at high temperature (max. 310℃) and pressure (max. 700 psi). The microwave digestion system was used to digest samples of four ultramafic rock reference materials (GBW07101, GBW07102, GBW07291, and WPR-1a), one basalt reference material (BIR-1a), and one black shale reference material (SGR-1b). The Re-Os isotope measurement results for GBW07291, BIR-1a, and SGR-1b were in agreement with previously published values, and we are the first to report Re-Os isotopes for GBW07101, GBW07102, and WPR-1a. Therefore, this new microwave digestion system is a simple, efficient, reliable, and safe sample digestion method for prospective applications in Re-Os isotopic analysis.

Abstract:Concentration of trace elements through TeCl4 volatilization in a flow reactor is presented for the first time and the potential of this approach for analysis was assessed. The method was developed for the multi-element analysis of high-purity Te. The matrix was volatilized through the reaction of Te with chlorine gas, which was obtained by the electrolysis of hydrochloric acid. The behavior of 61 trace elements during Te chlorination at 200–270 °С was studied. The maximum number of trace elements (39) quantitatively remained in the concentrate at a volatilization temperature of 240 °С. Trace element concentrations were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES). The limits of detection (LODs) of the 39 trace elements were 0.2–30 ng g–1. The possibility of reaching lower trace element LODs was demonstrated. For Ag, Cd, Mn, and Pd, the LODs were reduced by 3–25 times by using electrothermal atomic absorption spectrometry (ETAAS), with trace element LODs of 0.04–2 ng g–1. The precision of the matrix chemical volatilization procedure was evaluated using spike experiments. Recovery rates ranged from 80 to 119%. The analysis of a Te sample with unknown composition using ICP-OES and ETAAS methods after the proposed matrix chemical volatilization procedure gave comparable results to those obtained by ICP-OES without volatilization.