Echoes from ancient Earth: Zircon clues reveal Easter Island's hidden volcanic history

Echoes from ancient Earth: Zircon clues reveal Easter Island's hidden volcanic history
by Robert Schreiber
Berlin, Germany (SPX) Oct 17, 2024

A recent geological study involving researchers from Cuba, Colombia, and Utrecht University has unveiled surprising evidence that challenges conventional theories about Earth's mantle dynamics. Investigations of zircon minerals on Easter Island have revealed signs of volcanic activity dating back 165 million years, suggesting that the mantle beneath the island may behave differently than previously thought.

The volcanic history of Easter Island, known for its extinct volcanoes, dates back about 2.5 million years. However, recent zircon dating by a team led by Cuban geologist Yamirka Rojas-Agramonte uncovered minerals much older than expected, some as ancient as 165 million years. These findings raise questions about the origins of these minerals since the oceanic plate beneath the island is much younger than 165 million years.

Analysis showed that the zircon minerals' composition matched the magma of present-day volcanoes, pointing to a deep source in Earth's mantle. This discovery hints that the ancient minerals originated in the mantle long before the current volcanoes formed. The findings add complexity to the understanding of "hotspot volcanoes" like those on Easter Island, where mantle plumes rise from deep within the Earth to create volcanic formations.

Collaborating with Utrecht geologist Douwe van Hinsbergen, Rojas-Agramonte examined past geological events in the "Ring of Fire," a region marked by subduction zones where tectonic plates sink into the Earth's mantle. Van Hinsbergen's reconstructions indicated a large volcanic plateau existed near Easter Island 165 million years ago, which later subducted beneath the Antarctic Peninsula. This event coincided with significant geological changes, suggesting that the Easter Island mantle plume might have been active since that time.

The findings challenge the classical "conveyor belt" model, which views the mantle as a well-mixed, constantly moving layer beneath tectonic plates. The presence of ancient zircons suggests that the mantle surrounding the plume may be more stationary, allowing these minerals to remain near the surface despite geological activity.

This research builds on previous studies from the Galapagos Islands and New Guinea, offering new insights into the Earth's mantle's behavior and dynamics.

Research Report:Zircon xenocrysts from Easter Island (Rapa Nui) reveal hotspot activity since the middle Jurassic