Construction of an intraplate island volcano: The volcanic history of Heard Island

• Published in: Bulletin of Volcanology
• Main Authors: Fox, JM, McPhie, J, Carey, RJ, Jourdan, F, Miggins, DP
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2021
• Subjects: Earth Sciences; Geology; Volcanology; Kerguelen; Heard Island; Indian; Drygalski; Big Ben; Laurens Peninsula; Mawson Peak
• Online Access: https://doi.org/10.1007/s00445-021-01452-5; http://ecite.utas.edu.au/144313

Heard Island is a subantarctic volcanic island in the southern Indian Ocean and includes Australias only active volcano, Big Ben (2813 m high, 18km diameter). The most recent eruption of lava at Big Ben occurred in November 2020. Heard Island is the southernmost subaerial exposure of the Kerguelen Plateau, a mainly submerged large igneous province formed as a result of the activity of the Kerguelen plume over the last 130 Myrs. Using published and unpublished data and reports, modern satellite images, and private and public rock collections, we produced a new geological map of Heard Island supplemented by new 40 Ar/ 39 Ar isotopic ages. The volcanoes on Heard Island have been constructed on a ~ 300-m-thick platform of 105-Myr-old submarine volcaniclastic rocks known as the Drygalski Formation, now exposed above sea level. The Drygalski Formation is underlain by the Oligocene Laurens Peninsula Limestones. Exposed Big Ben lavas are dominated by basanite, basalt, and trachybasalt compositions. Two Big Ben lavas were dated at 11.1 1.1ka and 23.9 2.1ka, expanding the range of ages previously reported for nonhistorical lavas from Big Ben (356 5133 52ka). Sector collapse occurred on Big Ben prior to the formation of the current eruptive centre, Mawson Peak (likely after 23 16ka). Laurens Peninsula lies to the west of Big Ben and consists of trachyte and basanite lavas and domes. Laurens Peninsula lavas have ages in the range 5.1 3.5 to 76.6 5.5ka. Young basaltic cones are located around the coast of Heard Island and range in age from 1.9 3.8 to 13.3 4.1ka. Heard Island is a relatively small volcanic edifice with a low average magma discharge rate (~0.0002km 3 /yr) when compared with other intraplate basaltic volcanic islands.