The Rocks That Link Australia, New Zealand, Antarctica & New Caledonia

#australia #newzealand #antarctica The modern landscapes of New Zealand, Australia, Antarctica, and New Caledonia hold within them a long-lost geological mystery—an ancient volcanic arc that once stretched across what is now the southwest Pacific. This arc, born from a subduction zone along the eastern margin of Gondwana during the Permian period approximately 280–250 million years ago, was part of a vast network of volcanic island chains forming in the vast Palaeo-Pacific Ocean. Over millions of years, this arc was slowly deformed, broken apart, and scattered across the remnants of Gondwana as continents shifted and fragmented. Today, remnants of this once-mighty volcanic arc can be found in the Brook Street Terrane of New Zealand’s South Island, the Gympie Terrane in Queensland, the Teremba Terrane in New Caledonia, and parts of Northern Victoria Land in Antarctica. This video explores the origins of this volcanic arc, how it formed, and how geological forces violently tore it apart, leaving behind fragmented pieces across multiple continents. The arc was the product of a major subduction event, where an oceanic plate was being forced beneath a continental plate at an active convergent boundary. As this process continued, magma was generated deep within the Earth’s mantle, rising to the surface to fuel a chain of explosive volcanoes. These volcanoes formed in an oceanic setting, much like modern island arcs such as the Marianas, the Tonga-Kermadec Arc, or the Izu-Bonin Arc. These fiery islands would have been surrounded by a volatile seascape, shaped by repeated eruptions, seismic activity, and the constant motion of subduction. Despite the arc’s isolated origins, it did not remain an independent system forever. As subduction continued, the volcanic arc was gradually pushed toward the Gondwanan margin, colliding with the continental crust over time. This collision caused intense deformation, faulting, and the incorporation of the arc’s volcanic and plutonic rocks into what would eventually become the geological foundations of modern New Zealand, eastern Australia, and Antarctica. This process, known as accretion, left behind distinct geological terranes—pieces of crust that originated in a completely different tectonic setting before becoming sutured onto a continent. The Brook Street Terrane in New Zealand, the Gympie Terrane in Australia, and the Teremba Terrane in New Caledonia all share striking similarities, suggesting they were once part of a single volcanic arc system before being fragmented and displaced. As Gondwana began to break apart, the forces that had originally created the volcanic arc now worked to dismantle it even further. As Zealandia, the submerged continent that includes modern New Zealand and New Caledonia, began to rift away from Australia and Antarctica, fragments of the volcanic arc were carried along with it. This rifting, which eventually led to the opening of the Tasman Sea and the separation of Zealandia from the rest of Gondwana, further isolated the volcanic arc remnants, scattering them across different landmasses. The Brook Street Terrane was incorporated into Zealandia, while other pieces ended up in Queensland, New Caledonia, and Antarctica. The geological evidence that connects these terranes is found in the unique chemical signatures of the volcanic and plutonic rocks they contain. Geochemical studies have shown that these rocks exhibit characteristics of island arc magmatism, including tholeiitic basalts, andesites, and high-Mg ankaramites—volcanic rocks commonly associated with primitive island arcs. Additionally, intrusive rocks such as trondhjemites and gabbros, which formed deep within the magmatic roots of the arc, provide further evidence that these terranes were once part of the same system. Dating techniques, including zircon geochronology, have confirmed that the volcanic activity recorded in these terranes occurred during the Permian period, further strengthening the connection between them. Studies Used To Construct This Video: New Zealand: Implications for Permian tectonics of eastern Gondwana and magma genesis in modern intra‐oceanic volcanic arcs https://doi.org/10.1080/00288306.2005.9515107 Petrogenesis of Gympie Group volcanics: evidence for remnants of an early Permian volcanic arc in eastern Australia: https://doi.org/10.1016/0024-4937(88)90012-6 Updated Gondwana (Permian–Cretaceous) earth history of Australia: https://www.sciencedirect.com/science/article/pii/S1342937X05000304#fig3 Unraveling the New England orocline, east Gondwana accretionary margin https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011TC002864 🎥 If you would like to support this channel, consider joining our Patreon: https://patreon.com/OzGeology Join this channel to get access to perks: https://www.youtube.com/channel/UCxLrvjGBzYmj8W1rJToPasg/join