Age and correlation of volcanism in central Livingston Island, South Shetland Islands: K-Ar and geochemical constraints

摘要: Volcanic sequences in central Livingston Island can be divided into two broad groups. The older group consists of basalt-dacite lavas, clastic rocks and associated hypabyssal intrusions. lavas are lithologically compositionally similar to other pre-Pliocene, volcanic arc the South Shetland Islands. outcrops vary from relatively fresh (at Cape Shirreff, Hannah Point Siddons Point) indurated pervasively altered Mount Bowles, Burdick Peak Hurd Peninsula). Samples yielded Late Cretaceous ages for eruption or intrusion, ranging 90.2 ± 5.6 Ma at 73.0 2.3 Point. Chemical analyses suggest that these probably correlated stratigraphically with Byers Group Coppermine Formation, respectively. Two samples conflicting 87.9 2.6 67.5 2.5 centre top sequence, stratigraphical affinities sequence cannot yet determined unambiguously but it is unlikely part Group. All (which correspond Bowles Formation) Eocene-Oligocene K-Ar (44.4 35.0 Ma), interpreted as reset related emplacement cooling a nearby Eocene tonalite pluton responsible much alteration, also dated this study (43.3 2.8 Ma). A eruptive age (possibly Cretaceous) likely proven. By contrast, younger degraded basalt lava flows, tuff cone ring remnants, which Inott Formation. very Pleistocene Recent (≤ 1 They distinctive indistinguishable supra-subduction alkali basalts preserved elsewhere Livingston, Greenwich Penguin islands.