Twinn, Gary (2022): Apatite U-Th/He analysis of a transect across Antarctic Peninsula [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.942483

Apatite U-Th/He thermochronology data for a set of samples across Alexander Island and Palmer land on the Antarctic Peninsula. Data was collected to constrain the timing of uplift of the region of the southern Antarctic Peninsula and determine if the formation of a slab window beneath the region influences the formation of the mountain ranges in the region. Rock samples were collected during Antarctic expeditions between 1973 and 2001 and were stored in the British Antarctic Survey rock archive until requested in 2019. Samples form a transect across Alexander Island and the Antarctic Peninsula from 69.3°W to 62.8°W at an average latitude of 70.5°S. Data contains Helium, Uranium, Thorium and Samarium levels from individual Apatite grains for a set of samples as well as the size of each grain. Dataset contains calculated raw age and age corrected for alpha ejection. Corrected ages range from 12.6 to 78.6 Ma. Analyses were made at the Birkbeck/UCL London Geochronology Centre. Four to eight whole inclusion- and fracture-free grains were analysed per sample. Grains were hand-picked using a binocular microscope and selected grains further assessed under higher magnification using a Zeiss Axioplan microscope at a magnification of 1250x. Individual grains packed into a platinum tube were heated with an 808 nm iodine laser beam to 900-1000°C for three minutes, in order to degas the crystal for 4He measurement using a Pfeiffer Prisma 100 with Quadstar QS422 software. Gas volumes were determined by isotope dilution using two 5800 cc vacuum tanks with gas pipettes for delivering known aliquots of helium. The 4He Standard Tank (Q Tank), pipette volume 0.3222 cc contains isotopically pure 4He that is used as the gas standard against which samples and blanks are determined. The 3He Spike Tank, pipette volume 0.2258 cc contains isotopically pure 3He and is used for isotope dilution of samples and blanks. Following extraction, the Pt tubes were removed and placed in vials for dissolution. Tube ends were prised open to ensure solutions could get into the tube and dissolve the apatite grain. A 50μl spike with a known concentration of 235U, 230Th and 149Sm, which included HNO3, was added to each vial and left for 24-36 hours at room temperature to dissolve the apatite grains. After this, vials were topped up with 1500 μl of water ready for measurement on an Agilent 7900x ICP-MS. Each solution run included spike, acid and water blanks plus Durango age standards. Spike solutions were re-calibrated for each session. Errors on ages use the reproducibility of the Durango age standard which at the time of analysis was 5.9%.