Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far, in line with the work packages (WPs) and their implementation, are listed as follows:
a. WP 1: Develop solution U-Th dating protocol and enhance the efficiency using jet-interface setup.
First, we adopted the “Jet” interface configuration to enhance the sensitivity to achieve sufficient intensities of the target U-Th isotopes in natural carbonates. After the optimization of the system, the detection efficiency has been enhanced significantly to a useful yield of 1.30% for the solution phase (using a 0.01 ng/g U standard). In WP1, the fellow has successfully improved the efficiency and reduced the uncertainty in accordance with reliable accuracy.
b. WP 2: Establish an in-situ U-Th dating protocol with solution-based correction strategy.
In WP2, the fellow has successfully demonstrated a high sensitivity, in situ U-Th dating approach in carbonates using LA-ICPMS with solution-based correction strategy. Utilizing the “Jet” interface ICPMS setup also improved the detection efficiency to a yield of 1-2% for the solid phase (based on analyses of a NIST 612 standard). An online addition of a well characterized 229Th-233U-236U triple spike (TS) tracer, mixed with the laser generated carbonate aerosol, enabled to monitor and correct for mass discrimination and elemental fractionation effects of U and Th. The efficacy of inter-element fractionation, mass discrimination, and peak tailing baseline corrections are evaluated and optimized. Analysis of a flowstone sample in secular equilibrium, collected from Northern Calcareous Alps, resulted in activity ratios of 1.011 ± 0.066 (2 S.E.) for 230Th/238U, indicating laser ablation data can be generated with good accuracy. There is no significant difference for determined isotopic compositions and ages between our LA-ICPMS and previous multi-collector ICPMS techniques. This approach allows for the revelation of micro-domain age profiles in carbonates and will be applicable for fields like paleoclimatology, oceanography, and archaeology.
c. WP 3: Apply in-situ U-Th dating protocol on carbonate stalagmite to extract precisely timing of giant volcanic eruption(s) in the past.
The fellow envisioned to extract the timing of giant volcanic eruption(s) in the past by means of using this highly sensitive in situ U-Th dating protocol on carbonate stalagmite, however, ultimately the LA dating ages could not give promising results due to the poor quality of the stalagmite sample. The fellow will try to use data treatment approach to filter noisy data in order to obtain reliable dates. WP3 was mainly planned for the “Application study” using the in situ U-Th dating protocol. Thus the fellow shifted the intention of WP3, to focus on “assessing a dating time span 5-190 ka” for natural stalagmite samples. This shift allows ensuring the dating capability and extending the time ranges of this dating protocol.
An overview of the results and their exploitation and dissemination: During the period of the fellowship, the fellow has yielded 5 conference publications, 1 monograph, 1 manuscript underway, and 4 journal publications to date. Our outstanding results and this project have drawn the attention and interests from the scientific community and the public following the presentation in international conferences, workshops, journal publications, and outreach activities. This developed approach is fascinated by geo-oriented community. Future collaborations via this highly sensitive in situ U-Th dating protocol could be expected. Also, the inspiration of young generation to embrace research careers by the communication and outreach activities is definitely the outputs of MSCA.
