Eoarchean within-plate basalts from southwest Greenland

• Main Authors: Jenner, Frances, Bennett, Victoria, Yaxley, Gregory, Friend, C R L, Nebel, Oliver
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Geological Society of America Inc 2015
• Subjects: Greenland; Ocean Island
• Online Access: http://hdl.handle.net/1885/71145

The majority of >3 Ga metabasalts have chemical features, such as high field strength element (HFSE) depletions, that are characteristic of modern island-arc basalts. These compositions have been interpreted as evidence for subduction of oceanic crust early in Earth's history. Alternatively, the apparent absence of Archean mafic rocks with mid-oceanic ridge basalt (MORB) and ocean island basalt (OIB) compositions and the ubiquitous occurrence of metabasalts with HFSE anomalies suggest that these chemical features may instead be a widespread characteristic of the Archean mantle related to early chemical differentiation and unrelated to modern-style recycling of crust. Here we present major- and trace-element data for a suite of metabasalts from Innersuartuut Island, southwest Greenland, which have a minimum age constraint of 3.75 Ga and are likely as old as ≥3.85 Ga. Samples from Innersuartuut show no evidence for crustal contamination or subduction-related magmatism, and have a petrogenesis comparable to modern OIB. The new data demonstrate that a compositional range for volcanic rocks comparable to that seen in the Phanerozoic existed in the Eoarchean. Therefore, rather than a global anomaly, subduction-related processes are the likely origin for the compositions of the most commonly preserved Archean mafic rocks with island-arc basalt characteristics.