GHR1 Zircon – A New Eocene Natural Reference Material for Microbeam U‐Pb Geochronology and Hf Isotopic Analysis of Zircon

Abstract

We present multitechnique U-Pb geochronology and Hf isotopic data from zircon separated from rapakivi biotite granite within the Eocene Golden Horn batholith in Washington, USA. A weighted mean of twenty-five Th-corrected 206 Pb/ 238 U zircon dates produced at two independent laboratories using chemical abrasion-isotope dilution-thermal ionisation mass spectrometry (CA-ID-TIMS) is 48.106 ± 0.023 Ma (2s analytical including tracer uncertainties, MSWD = 1.53) and is our recommended date for GHR1 zircon. Microbeam 206 Pb/ 238 U dates from laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ion mass spectrometry (SIMS) laboratories are reproducible and in agreement with the CA-ID-TIMS date to within < 1.5%. Solution multi-collector ICP-MS (MC-ICP-MS) measurements of Hf isotopes from chemically purified aliquots of GHR1 yield a mean 176 Hf/ 177 Hf of 0.283050 ± 17 (2s, n = 10), corresponding to a eHf 0 of +9.3. Hafnium isotopic measurements from two LA-ICP-MS laboratories are in agreement with the solution MC-ICP-MS value. The reproducibility of 206 Pb/ 238 U and 176 Hf/ 177 Hf ratios from GHR1 zircon across a variety of measurement techniques demonstrates their homogeneity in most grains. Additionally, the effectively limitless reserves of GHR1 material from an accessible exposure suggest that GHR1 can provide a useful reference material for U-Pb geochronology of Cenozoic zircon and Hf isotopic measurements of zircon with radiogenic 176 Hf/ 177 Hf.

Linking metamorphism, magma generation, and synorogenic sedimentation to crustal thickening during Southern Appalachian mountain building, USA

“…In accordance with accepted norms, individual spot ages are reported in Table 5 with 1σ uncertainties and weighted averages for individual populations, and all ages in the text are presented with 2σ uncertainties and the mean square of weighted deviates (MSWD). An example of typical SHRIMP-RG precision and accuracy can be found in Eddy et al (2019).…”

SA01 – A Proposed Zircon Reference Material for Microbeam U‐Pb Age and Hf‐O Isotopic Determination

“…A suitable natural reference material should be homogeneous in both chemical and isotopic compositions at the scale of analysis. Previous studies have identified a number of natural zircons as reference materials suitable for geochronology and isotope geochemistry, including SL7 (Kinny et al ), CZ3 (Pidgeon et al ), SL13 (Claoué‐Long et al ), 91500 (Wiedenbeck et al ), Temora (Black et al ), BR266 (Stern ), GJ‐1 (Jackson et al , Morel et al ), Mud Tank (Woodhead and Hergt ), M257 (Nasdala et al ), Plešovice (Slama et al ), Sri Lanka (Gehrels et al ), OG1/OGC (Stern et al , Kemp et al ), Penglai (Li et al ), Qinghu (Li et al ), OD‐3 (Iwano et al ), M127 (Nasdala et al ), BB (Santos et al , Lana et al ), LGC‐1 (Tian et al ), GZ7/GZ8 (Nasdala et al ), LKZ‐1 (Cheong et al ) and GHR1 (Eddy et al ). However, most of them are either exhausted or have limited availability against the increasing demands of the microbeam laboratories.…”

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

“…2004), GHR1 (Eddy et al . 2019), Fish Canyon Tuff (Schmitz and Bowring 2001), RAK‐17 (Webb et al . 2020) and Plešovice zircon (Sláma et al .…”