Upwelling too melting of Earth’s pall at mid-ocean ridges, every bit good every bit the eruption of novel magmas on the seafloor, drive the continual production of the oceanic crust. As the oceanic crust moves away from the mid-ocean ridges too cools it becomes denser than the underlying mantle. Over fourth dimension the bulk of this oceanic crust sinks dorsum into the mantle, which tin compass notice trigger farther volcanic eruptions. This procedure is known every bit subduction too it takes house at plate boundaries.
Volcanic eruptions that are triggered past times subduction of oceanic crust are chemically distinct from those erupting at mid-ocean ridges too oceanic isle chains, such every bit Hawaii. The differences betwixt the chemical scientific discipline of magmas produced at each of these tectonic settings render ‘geochemical fingerprints’ that tin compass notice endure used to endeavor to seat the types of tectonic action taking house early on inward Earth’s history.
Previous geochemical studies receive got used similarities betwixt modern subduction zone magmas too those erupted nearly 3.8 billion years ago, during the Eoarchean era, to scrap that subduction-style tectonic action was taking house early on inward Earth’s history. But no ane was able to locate whatever suites of volcanic rocks alongside compositions comparable to modern mid-ocean ridge or oceanic isle magmas that were older than iii billion years too were every bit good gratis from contamination past times continental crust.
Because of this missing slice of the puzzle, it has been ambiguous whether the subduction-like compositions of volcanic rocks erupted 3.8 billion years agone actually were generated at subduction zones, or whether this magmatism should endure attributed to other processes taking house early on inward Earth’s history. Consequently, testify for subduction-related tectonics before than iii billion years agone has been highly debated inward scientific literature.
Jenner too her squad collected 3.8 billion-year-old volcanic rocks from Innersuartuut, an isle inward southwest Greenland, too flora the samples receive got compositions comparable to modern oceanic islands, such every bit Hawaii.
“The Innersuartuut samples may correspond the world’s oldest recognized suite of oceanic isle basalts, gratis from contamination past times continental crust,” Jenner said. “This testify strengthens previous arguments that subduction of oceanic crust into the pall has been taking house since at to the lowest degree 3.8 billion years ago.”