SS14‐28: An Age Reference Material for Zircon U‐Th Disequilibrium Dating

Abstract

U‐Th disequilibrium dating uses the ratio of the intermediate 230Th daughter isotope to the 238U parent isotope to date zircon crystallisation for volcanic and plutonic rocks in Pleistocene–Holocene deposits. It is frequently used to constrain the duration and rate of magma recharge in volcanic systems. While ≲ 350 ka zircon is not in secular equilibrium in the 230Th system, the current U‐Th disequilibrium methodology uses reference materials that are > 350 ka. No reference material ≲ 350 ka has been available to validate the accuracy of the approach and ensure methods are repeatable across laboratories. This study presents zircon SS14‐28 from Jeju Island (South Korea) as a suitable reference material for U‐Th disequilibrium dating. Zircon SS14‐28 was analysed using two analytical approaches (SIMS and LA‐ICP‐MS) and four instruments: CAMECA IMS 1280, ASI SHRIMP II, sector field high‐resolution LA‐ICP‐MS and multi‐collector LA‐ICP‐MS, in four laboratories. These methods each individually result in isochrons gradients within uncertainty (2s) of each other (CAMECA: 0.532 ± 0.051 (MSWD = 0.64); SF‐HR‐LA‐ICP‐MS: 0.536 ± 0.054 (MSWD = 1.3); MC‐LA‐ICP‐MS: 0.533 ± 0.041 (MSWD = 0.67); SHRIMP II: 0.68 ± 0.22 (MSWD = 0.3)). The age proposed in this study is 82 ± 6 ka calculated from a combined isochron gradient of 0.529 ± 0.025 (MSWD = 0.87, n = 132).

Simultaneous U–Pb and U–Th Dating Using LA-ICP-MS for Young (<0.4 Ma) Minerals: A Reappraisal of the Double Dating Approach

“…The SS14-28 is a trachyte sample outcropping in the Hallasan UNESCO World Heritage site on Jeju Island, South Korea [10]. Zircon SS14-28 was previously analyzed using two analytical approaches (SIMS and LA-ICP-MS) and four instruments: CAMECA IMS 1280, ASI SHRIMP II, sector field high-resolution LA-ICP-MS and multi-collector LA-ICP-MS, yielding a proposed age of 82 ± 6 ka [10]. Zircon SS14-28 (Figure 3) was embedded in a The SS14-28 is a trachyte sample outcropping in the Hallasan UNESCO World Heritage site on Jeju Island, South Korea [10].…”

“…Zircon SS14-28 was previously analyzed using two analytical approaches (SIMS and LA-ICP-MS) and four instruments: CAMECA IMS 1280, ASI SHRIMP II, sector field high-resolution LA-ICP-MS and multi-collector LA-ICP-MS, yielding a proposed age of 82 ± 6 ka [10]. Zircon SS14-28 (Figure 3) was embedded in a The SS14-28 is a trachyte sample outcropping in the Hallasan UNESCO World Heritage site on Jeju Island, South Korea [10]. Zircon SS14-28 was previously analyzed using two analytical approaches (SIMS and LA-ICP-MS) and four instruments: CAMECA IMS 1280, ASI SHRIMP II, sector field high-resolution LA-ICP-MS and multi-collector LA-ICP-MS, yielding a proposed age of 82 ± 6 ka [10].…”

“…Zircon SS14-28 (Figure 3) was embedded in a The SS14-28 is a trachyte sample outcropping in the Hallasan UNESCO World Heritage site on Jeju Island, South Korea [10]. Zircon SS14-28 was previously analyzed using two analytical approaches (SIMS and LA-ICP-MS) and four instruments: CAMECA IMS 1280, ASI SHRIMP II, sector field high-resolution LA-ICP-MS and multi-collector LA-ICP-MS, yielding a proposed age of 82 ± 6 ka [10]. Zircon SS14-28 (Figure 3) was embedded in a PFA Teflon sheet without polishing, using the same method as sheet samples Toya4-BP and Toya4-BP2.…”

“…Zircon isochron and model ages were obtained using IsoplotR v.5.5 [24]. The model ages were calculated assuming Th/U of magma to be 4.0 for Toya and 7.8 for SS14-28 [10]. Data with a high (>100% at 2σ) uncertainty were excluded for weighted mean age calculation.…”

“…Apart from the effort to date zircon U-Pb and U-Th simultaneously, recent progress of zircon U-Th dating methodology using LA-ICP-MS is summarized in [9]. In this paper, we follow Guillong et al [8]'s advice for U-Th disequilibrium dating and report simultaneous U-Pb and U-Th ages of Toya and SS14-28, a recently proposed U-Th zircon reference material [10], and demonstrate once again that simultaneous U-Pb and U-Th dating using LA-ICP-MS is viable and useful, although its precision is not so high as dating by U-Th solely (e.g., [9][10][11][12]).…”