LA-ICP-MS U Pb geochronology of wolframite by combining NIST series and common lead-bearing MTM as the primary reference material:Implications for metallogenesis of South China

Two reliable calibration methods for accuratein situU–Pb dating of scheelite

“…Based on our experiences on garnet and wolframite by LA-SF-ICP-MS 21,22 and considering that we want to obtain a signal for 206 Pb, 207 Pb, and 238 U and keep a high resolution to t small grains and altered crystal zones of some scheelite samples, the ablation settings, i.e., a laser spot size of 32 mm (24 mm in one analytical section), repetition rates of 5 and 10 Hz, and energy densities of 3, 5, and 10 J cm À2 , were mainly used to analyze a relatively well-characterized scheelite sample WX27 for comparison. Normal conditions of 32 mm, 3 J cm À2 , and 5 Hz were applied to analyze all other scheelite samples from typical W deposits.…”

“…Three proposed wolframite standards of MTM, YGX, and WT are more homogeneous than others, but also have variable U and common Pb shown in the Tera-Wasserburg Concordia diagram in previous and our studies. 10,20,21,23 Moreover, they were with different ID-TIMS U-Pb ages of 334.4 AE 1.7 and 316.7 AE 5.8 Ma, 152.8 AE 2.0 and 160.9 AE 0.7 Ma, and 95.2 AE 1.0 and 104.3 AE 0.5 Ma. [17][18][19][20]23 Thus, if there are no concordant YGX spots, a combined calibration method using wolframite YGX and NIST glasses (e.g., NIST612) to correct the mass fractionation of 238 U/ 206 Pb and 207 Pb/ 206 Pb isotope ratios of the unknowns, respectively, is to be used.…”

“…1,10,[17][18][19][20]23 Ferberite, hübnerite, and wolframite were conrmed to get accurate and precise in situ U-Pb ages when using the well-characterized wolframite sample YGX as a primary standard 17 or the combined calibration method. 21 Meanwhile, scheelite as a useful geochronometer to directly date the W mineralization event was also proposed. 14,15 However, the reliability of this U-Pb dating technique for scheelite has not been evaluated due to the lack of matrixmatched reference material.…”

Geochronology and geochemistry of Late Mesozoic diabase in the Litun ore district, North China Craton

“…Zircon U–Th–Pb analyses were performed on an Agilent 7700x ICP–MS with a 193 nm Coherent Ar–F gas laser at the Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China. Analytical procedures were the same as those described by (Tang et al, 2017b, 2020). The beam diameter was ~32 μm.…”

“…Analytical procedures were the same as those described by (Tang et al, 2017b(Tang et al, , 2020. The beam diameter was ~32 μm.…”