Assessing tectonic plate reconstruction models using trends in global geochemical data.

Abstract

The evolution of Earth’s crust is a complex four-dimensional framework. Tectonic plate reconstruction models aim to constrain the global positions and movements of plates through Earth’s history. These models are vital for understanding various Earth processes, theories and phenomena. Models for relatively recent geological time are well-constrained but the further back in time we aim to reconstruct, the more uncertainty arises in models produced. This causes models for the same point in time to have differing configuration hypotheses. Further methods are hence needed to improve and validate proposed models. This study makes use of a vast global geochemical database with over one million samples. Data is grouped into pre-defined geological provinces and normalised, based on the type of province, in terms of its tectonic setting. Province trace geochemical data is then statistically analysed and compared to other provinces in order to determine conjugate province pairs. Reconstructions of Pangea are used to determine known province pairs. Trace geochemistry trends are then assessed across these known pairs via hypothesis testing, yielding a p-value test statistic signifying similarity between province geochemistry. Unrelated province geochemistry is also assessed as a control case for which p-values are also determined. P-value thresholds are defined for each trace element. Hypothesis testing between the geochemistry of two provinces yielding a p-value higher than this threshold signifies a geochemical similarity between provinces unique to conjugate pairs. Using this method, conjugate province pairs for the North China Craton during the Paleoproterozoic are identified. The results from these tests have implications for the configuration of the supercontinent Nuna. Ultimately, the methods employed in this study emphasise the importance of geochemical data in constraining the configuration of continental blocks within past supercontinents and hence plate reconstruction models.