A TECTONIC REGIME TRANSITION FROM MANTLE PLUME TO SUBDUCTION IN THE NEOARCHEAN ABITIBI TERRANE, SUPERIOR CRATON
Seminars
Semester 2
The transition from pre-plate tectonic regimes to modern plate tectonics is a pivotal yet contested event in Earth's history. The Neoarchean Abitibi terrane in the Superior Craton preserves a critical record of this transition. This study integrates field mapping, petrography, whole-rock geochemistry, Sm-Nd isotopes, and zircon U-Pb-Lu-Hf-trace element analyses of tonalitic-trondhjemitic-granodioritic (TTG) gneisses, sanukitoids, and associated metavolcanic rocks. Our results document a tectonic regime transition in the Abitibi terrane from an early vertical, mantle plume-dominated system (ca. 2750-2705 Ma) to a later horizontal, subduction- and collision-driven plate tectonic system (ca. 2705-2665 Ma). This transition is marked by a magmatic evolution from reduced, low-H2O TTGs derived from oceanic plateau basalts to oxidized, hydrous sanukitoids sourced from subduction-metasomatized mantle, a finding strongly supported by regional geophysical and structural studies.
By synthesizing global geological records, we further propose that such tectonic regime transitions occurred diachronously across various cratons during the late Archean (~3.2-2.5 Ga), signaling the global onset of plate tectonics.
For additional information, please contact Mr. Xin HE, u3011623@connect.hku.hk.