Titanite petrochronology linked to phase equilibrium modelling constrains tectono-thermal events in the Akia Terrane, West Greenland

摘要: Abstract The Mesoarchean Akia Terrane in West Greenland contains a detailed magmatic and metamorphic mineral growth record from 3.2 Ga to at least c. 2.5 Ga. This time span makes this region an important case study the quest track secular changes geodynamic style which may ultimately inform on development of plate tectonics as globally linked system lateral rigid motions. common accessory titanite has recently become recognised powerful high temperature geochronometer whose chemistry chart thermal conditions its growth. Furthermore, offers potential time-temperature history mafic lithologies, lack zircon. Although suffers higher levels Pb than many other U chronometers, we show how measurement 207Pb/206Pb texturally coeval biotite assist characterization appropriate composition titanite. Titanite extracted two samples gneisses both yield ages 2.54 Ga. coeval, their implies under distinctly different processes. In one case, elevated total REE, Th/U grew in-situ partial melt, consistent with identical date granite dyke contrast, second sample greater Pb, lower Th/U, dominantly hydrothermal fluids. Zr-in-titanite thermometry for melt-derived titanite, activities constrained by phase equilibrium modelling, indicates maxima 690 °C. Elsewhere Terrane, metamorphism is estimated temperatures 670 °C. These new results when coupled existing findings indicate punctuated, repeated events (re)occurred three times between 3.0 2.5 Ga, but crucially changed across 3.0 Ga change point. We interpret reflecting fundamental shift 3.0 Ga, estimates onset widespread tectonic-type