Early Cenozoic diorite and diabase from Doumer Island, Antarctic Peninsula: zircon U-Pb geochronology, petrogenesis and tectonic implications

Abstract

In order to understand the petrogenesis and tectonic setting of diorite and diabase units on Doumer Island, Antarctic Peninsula, this paper reports new laser ablation—inductively coupled plasma—mass spectrometry (LA-ICP-MS) zircon U-Pb, geochemical, and Lu-Hf isotopic data for the magmatism. The diorite and diabase samples yielded zircon U-Pb ages of 55.4 ± 0.3 and 52.8 ± 0.4 Ma, respectively. These samples are enriched in the large ion lithophile elements and the light rare earth elements, and are depleted in the high field strength elements. The zircons in these samples yield Hf (t) values from 9.03 to 11.87 and model ages (TDM2) of 342–524 Ma. The major, trace, rare earth element (REE), and Hf isotopic data for the diorites indicate that these units were formed by the mixing of magmas generated by (a) the partial melting of mantle wedge material that experienced fluid-metasomatism in a subduction zone setting, and (b) the melting of juvenile crustal material induced by the upwelling of mantle-derived magmas in a subduction–collision setting. The diabase units contain higher total REE concentrations than the diorite, indicating they were derived from a different source region. These samples also have higher Mg# values and contain lower concentrations of Cr and Ni than the diorites, and have weakly negative Nb and Ta anomalies with Nb/Ta values of Citation: Cui J W, Hu J M, Pei J L, et al. Early Cenozoic diorite and diabase from Doumer Island, Antarctic Peninsula: zircon U-Pb geochronology, petrogenesis and tectonic implications. Adv Polar Sci, 2019, 30(2): 149-164, doi: 10.13679/j.advps.2018.0036