Development and applications of new techniques for tests of trace elements and rare earth elements in carbonate minerals

Trace elements and rare earth elements (REEs) are of great value in reconstructing diagenetic environments and tracing the diagenetic fluid evolution. Presently, the solution method is recognized as a well-established, commonly used analytical method, but due to its high demand for powdered samples, it is only applicable to mixed samples of multiple diagenetic microfabrics with relatively low accuracy. With the support of the State Energy Key Laboratory for Carbonate Oil and Gas, we conduct the research and development of new techniques for analyzing trace elements and REEs in carbonate minerals, achieving three significant outcomes. First, upgrading the technique for testing trace elements and REEs in carbonate minerals with solution method. The required quantity of powdered samples gets reduced from 50 mg to 10 mg, meeting the sampling and testing requirements of microfabrics. Moreover, less time is needed for sample analysis and tests, so does the acid consumption, falling from 10 mL to 2 mL, resulting in a lower relative error of analysis and tests of 2 % ~ 5 % from 5 % ~ 10 %. Second, developing a new continuous laser mapping technique for trace elements and REEs using a laser ablation system and a triple quadrupole inductively coupled plasma mass spectrometer (ICP-MS) platform. With this technique, the lower limit of detection content is reduced from 1-10 ppb to a sub-ppb level, while the spatial resolution of images rises from ≥ 5 μm to ≤ 1 μm, and the time efficiency for image scanning and processing is increased by 10 times. Third, besides its applications in reconstructing the diagenetic environments of microfabrics and tracing the diagenetic fluid evolution, this new technique developed can improve the success rate and accuracy of laser-ablation U-Pb isotopic absolute dating.