Influence of Th-rich mineral phases on U–Th radioactive disequilibrium ages of sulfide deposits from the Okinawa Trough

Rapid Extraction Chemistry Using a Single Column for 230Th/U Dating of Quaternary Hydrothermal Sulfides

“…To solve these problems, a rapid extraction procedure using a single column for U and Th in sulfides was designed using the AG 1-X8 resin. In our work, the dissolving efficiency performed better than others [6,7,9]; the separation of U and Th could be completed within one day and the accuracy and precision for the U and Th isotope ratios and the 230 Th age were improved. Using this method, repeated analyses of the Geological Survey of Japan geochemical reference material JZn-1 (about 65 Ma) and an in-house hydrothermal sulfide standard QS-1 gave very consistent results, which suggest that QS-1 is potentially a very good Quaternary U-Th age reference material.…”

“…230 Th/U dating, also called U-Th dating or 230 Th-234 U-238 U dating, is a conventional high-precision tool for dating Quaternary carbonate [1][2][3][4] and sulfides [4][5][6][7][8][9]. This process can act as an accurate chronological control for submarine hydrothermal systems and provides important time constraints for the formation mechanism, the history of transformation and the growth rate of large sulfide deposits [10][11][12][13][14][15].…”

“…As with authigenic carbonate, submarine Quaternary sulfides are known to meet the two preconditions for 230 Th/U dating, namely: (1) a large amount of highly soluble U and almost no Th are taken up during mineral deposition; (2) after deposition, the system remains closed to U and Th. According to the literature, the 238 U content of most submarine hydrothermal sulfide minerals ranges from several ppb to tens of ppm, whereas the 232 Th content is generally less than a few ppb [7][8][9]13,23,24].…”

“…In typical literature procedures, several grams of sulfide are dissolved in concentrated nitric acid at 85 • C for several days, during which any insoluble minerals are discarded [7,9]. Then, Fe 3+ and OH − are added to the solution in sequence to form Fe(OH) 3 precipitate.…”

“…Then, Fe 3+ and OH − are added to the solution in sequence to form Fe(OH) 3 precipitate. U and Th are coprecipitated with Fe(OH) 3 [6] and loaded directly into double columns packed with AG 1-X8 and U/TEVA resins to separate the U and Th [7,9] using HCl and HNO 3 . The separated U and Th fractions are analyzed using MC-ICPMS or thermal ionization mass spectrometry (TIMS) [6,10,12,[26][27][28].…”