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J Vis Exp. 2019 May 20;(147). doi: 10.3791/59098.

Separation of Uranium and Thorium for 230Th-U Dating of Submarine Hydrothermal Sulfides.

Author information

1
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences; Institutions of Earth Science, Chinese Academy of Sciences; University of Chinese Academy of Sciences; wangls@mail.iggcas.ac.cn.
2
Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences; Institutions of Earth Science, Chinese Academy of Sciences.
3
First Institute of Oceanography, State Oceanic Administration.
4
Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration.

Abstract

The age of a submarine hydrothermal sulfide is a significant index for estimating the size of hydrothermal ore deposits. Uranium and thorium isotopes in the samples can be separated for 230Th-U dating. This article presents a method to purify and separate U and Th isotopes in submarine hydrothermal sulfide samples. Following this technique, the separated U and Th fractions can meet measuring requirements by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The age of the hydrothermal sulfide sample can be calculated by measuring the present-day activity ratios of 230Th/238U and 234U/238U. A super clean room is necessary for this experiment. Cleaned regents and supplies are used to reduce the contamination during the sample processes. Balance, hotplate, and centrifuge are also used. The sulfide sample is powdered for analysis and less than 0.2 g sample is used. Briefly, the sample is weighed, dissolved, added to 229Th-233U-236U double spike solution, Fe co-precipitated, and separated on an anion-exchange resin extraction column. Approximately 50 ng U is consumed for 230Th-U dating of sulfides sample by MC-ICPMS.

PMID:
31157761
DOI:
10.3791/59098

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