Early Cenozoic diorite and diabase from the Doumer Island, Antarctic Peninsula: Zircon U-Pb geochronology, petrogenesis and tectonic implications
Jiawei Cui, Jianmin Hu, Junling Pei, Hong Chen, XingXing Du, Lijie Wei
Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
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 <3. The zircons in these samples yield Hf(t) values from 9.08 to 11.11 and model ages (TDM2) of 389–503 Ma. The major, trace, REE, and Hf isotopic compositions of the diabase units were derived from the mixing of depleted mantle-derived magmas with magmas generated by the melting of juvenile crustal material which was induced by the upwelling of the mantle into the crust. Overall the Cenozoic diorite and diabase on Doumer Island is related to subduction environment.
intrusive; zircon U–Pb dating; Lu-Hf isotope; subduction environment; Early Cenozoic; Doumer Island