Cenozoic Structurally Controlled Hydrothermal Activity Revealed by Apatite Thermochronology in the Convoy Range (Southern Victoria Land, Antarctica)

Abstract

The Transantarctic Mountains form the longest and highest extensional mountain range on Earth, marking the boundary between the Antarctic craton and the Mesozoic-Cenozoic rifted Ross Sea lithosphere. During the Cenozoic, deep offshore troughs, such as the Terror Rift, developed at the front of the Transantarctic Mountains in response to transtensional dextral kinematics that overprinted an older phase of orthogonal rifting. On land, few direct age constraints of Cenozoic faulting exist, and evidence of fault activity is often inferred from fission track age dating. In this study, we focused on the Convoy Range block in southern Victoria Land, a region with limited field surveys and thermochronological data. We present the results of multiscale structural analysis, geothermometry, and apatite fission-track thermochronology aimed at reconstructing the fault architecture and timing of deformation. The fault pattern is dominated mainly by nearly N-S striking normal faults, with a subordinate system of right-lateral transtensional faults. Brittle deformation is accompanied by diffuse propylitic alteration and carbonatization, providing evidence of hydrothermal fluid-rock interaction in a mesothermal environment (∼175–325°C). Fission track ages of fault rocks as young as ∼23 Ma are interpreted as local thermal resetting along faults, potentially constraining the age of deformation. These results document a case of structurally controlled hydrothermal fluid flow coeval to Cenozoic transtensional reactivation in Victoria Land, with important implications for the onset of Cenozoic volcanism in the region.