February 13, 2018
Mr. ZUO, Jiawei Department of Earth Sciences, HKU
There are two broad categories of hypotheses for early Earth’s tectonic mode: plate tectonics and vertical tectonics. All Eo- and Paleo-Archean terranes possess a strikingly similar set of lithologies. Unsurprisingly, most of them were similarly interpreted; both plate and vertical tectonic models have been applied. Only the Isua supracrustal belt, an Eoarchean (>3.6 Ga) terrane located at SW Greenland, has been exclusively interpreted via plate tectonics. However, proposed plate tectonic models of Isua differ in even their basic geometries, kinematics, and subduction polarities. To test the viability of various tectonic models, I am constraining the geological record here for comparison with model predictions. Multi-disciplinary approaches include: 1) phase equilibria work to evaluate metamorphic conditions; 2) strain analysis to better define deformation conditions; and 3) dating of magmatic and metamorphic events. Synthesis of these data sets will provide a reconstruction of the Pressure-Temperature-time-deformation (P-T-t-d) evolutionary pathways across Isua. P-T-t-d paths can in turn test the various tectonic models for this singular terrane (e.g., by identifying / falsifying proposed subduction P-T-t-d pathways), and consequently improve our understanding of early Earth tectonics.