Calcite mineral laser uranium-lead isotope dating process

Abstract

The invention provides a calcite mineral laser uranium-lead isotope dating process. The process comprises raking via a calcite sample to be detected and standard samples, and the standard sample at least comprising an isotope fractionation correction standard sample, an age correction standard sample and a verification standard sample WC-1; carrying out laser ablation sampling on the calcite sample to be detected and the standard samples, and respectively carrying out isotope detection on obtained ablation products; correcting obtained isotope values by utilizing the isotope fractionation correction standard sample; respectively calculating the test ages of the calcite sample to be detected, the age correction standard sample and the verification standard sample WC-1 by utilizing the corrected isotope values; determining an age correction factor according to the test age and the recommended age of the age correction standard sample; correcting the test age of the calcite sample to be detected and the test age of the verification standard sample WC-1 by using the age correction factor to obtain the final age of the calcite sample to be detected and the final age of the verificationstandard sample WC-1; and judging whether the test result is valid or not according to whether the final age of the verification standard sample WC-1 is within the recommended age range or not.

Description

technical field [0001] The invention relates to a calcite mineral laser uranium-lead isotope dating process, which belongs to the technical field of dating of ancient carbonate rocks in petroleum and natural gas geological exploration. Background technique [0002] At present, the U-Pb dating method has become the most commonly used and most accurate dating method in the field of geology. With the development of modern laser technology and mass spectrometry, laser U-Pb isotope dating methods for various minerals have been developed, especially carbonate laser U-Pb isotope dating has recently received more and more attention. In the process of laser U-Pb isotope dating, different instruments, Different time tests will produce different isotope fractionation. Therefore, it is necessary to correct the isotope values ​​using homogeneous glass standards, and then use homogeneous standards of known age to calculate correction factors for matrix age correction. At present, homog...

AI Technical Summary

Problems solved by technology

Ancient carbonate rocks are often in the age range of hundreds of millions of years, so the standard sample ASH15E is too young to meet the requirement that the age of the sample to be tested is as close as possible, so it is not the best standard sample

Although the recommended age of the WC-1 standard sample is 250.4Ma-254.5Ma, which is closer to the age of the sample to be tested, the inhomogeneity of the standard sample leads to different age values ​​measured at different times, respectively. 250.4±2.7Ma (Q.Li et al., 2014) and 254.5±3.7Ma (Coogan et al., 2016), so the base age correction with WC-1 standard sample is prone to cause the heterogeneity of the standard sample itself which may lead to biased results

[0004] To sum up, among the two existing calcite standard samples, ASH15E is too young, and WC-1 itself has 3%-5% heterogeneity, neither is the best age standard sample for ancient carbonate rocks

Most of the existing laser U-Pb isotope dating methods for ancient carbonate rocks use WC-1 as a standard sample for matrix age correction. On the one hand, there is only one calibration standard in this method, and there is a lack of a verification standard to monitor the accuracy of the data

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