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Subduction-related evolution of the eastern and northern Solomon Islands

Artemis E.*, Olierook H., Hameed H., Doucet L.S.

Curtin Frontier Institute for Geoscience Solutions & School of Earth and Planetary Sciences, CurtinUniversity, Bentley, WA 6102, Australia

The tectonic evolution of the Solomon Islands archipelago remains the focus of many present-day studies as it is widely considered the best record of subduction polarity reversal on Earth. These subduction events represent the transformation of an overriding plate to a down-going plate at subduction boundaries, leading to potential increases in regional seismicity, volcanic eruptions and enrichment of resource systems. Contrasting tectonic models have since been developed to constrain the timing and evolution of multi-phase arc initiation, oceanic plateau collision and subduction polarity reversal in the Solomon region. However, all these models are based on limited and mostly inaccurate age data. While geological histories of southwestern, central and northwestern Solomon islands are constrained by limited precisegeochronological data, the eastern and central-northern island extents, Makira and Santa Isabel, lack any robust age estimates, significantly hampering the validity of subduction evolution models. Here we present the first robust U-Pb zircon ages for Makira and Santa Isabel, revealing an Eocene to Oligocene emplacement history at ~43 to 33 Ma. These findings coincide with the first stage of arc growth (Stage 1) occurring within the Solomon region from the Eocene to Early Miocene, before arrival of the Ontong Java Plateau at the subduction channel (~25 to 20 Ma). Importantly, there is neither evidence for pre-45 Ma nor Stage 2 (>5 Ma) arc growth, as had been previously proposed for Isabel and Makira, respectively. A better temporally-constrained subduction history of the Solomon Islands arc will provide crucial insights for further studies on arc–plateau collision and arc reversal mechanisms, contributing to palaeo-climatic reconstructions, natural hazard assessment and resource potential of South Pacific island regions.