GEOL 5903 Seminar: Kyle Kucker
April 6, 2018
6 April 2018
GEOL 5903 Grad Seminar: Kyle Kucker
Title: "Contrasting models for the genesis of Archean tonalite-trondhjemite-granodiorite (TTG) suites in the early continental crust of the Earth"
Time: 12:30 p.m.
Location: Huggins Science Hall, room 324
Abstract: In the early Earth (4.4-3.2 Ga), mantle temperatures were hotter than they are today, modern-day plate tectonics had yet to be initiated, and the crust was composed predominantly of dense, magnesium-rich mafic rocks. However, even at these early stages in Earth’s history, processes were underway to form the first primordial continental crust. Between half and two-thirds of the oldest rocks observed in today’s continental crust were formed in the early Archean (4-3.2 Ga) and are composed of a tonalite-trondhjemite-granodiorite (TTG) series. The TTG series have been classified into low-, medium-, and high-pressure regimes, with present-day volumes of each estimated to be at a ratio of 1:3:1. Two main families of models have been debated over the origins of the Archean TTG crustal rocks. In comparison with natural data from the geological record, these competing models are being utilized to study how the primordial TTG crustal rocks may have formed. One line of thought suggests a history dominated by volcanic processes, producing a cold, thick lithosphere, and incorporates a subduction-like delamination of the lower crust. The other line of thought suggests that a relatively warmer, thinner lithosphere was produced via an intrusive-dominated regime. Both tectonic processes presented by these differing models can produce TTG series, but which of these models can produce an accurate representation of the relative percentages of the Earth's primordial continental crustal rocks is still debated.