Abstract
The evolution and the growth of the continental crust is inextricably linked to the evolution of Earth’s geodynamic processes. The detrital zircon record within the continental crust, as well as the isotopic composition of this crust, indicates that the amount of juvenile felsic material decreased with time and that in geologically recent times, the generation of new crust is balanced by recycling of the crust back into the mantle within subduction zones. However it cannot always have been so; yet the nature of the crust and the processes of crustal reworking in the Precambrian Earth are not well constrained. Here we use both detrital zircon ages and metamorphic pressure-temperature-time (P-T-t) information from metasedimentary units deposited in proposed convergent settings from Archaean, Proterozoic and Phanerozoic terrains to characterize the evolution of minimum estimates of burial rate (km.Ma−1) as a function of the age of the rocks. The demonstrated decrease in burial rate correlates positively with a progressive decrease in the production of juvenile felsic crust in the Archaean and Proterozoic. Burial rates are also more diverse in the Archaean than in modern times. We interpret these features to reflect a progressive decrease in the diversity of tectonic processes from Archaean to present, coupled with the emergence of the uniquely Phanerozoic modern-style collision.
Highlights
The evolution and the growth of the continental crust is inextricably linked to the evolution of Earth’s geodynamic processes
The detrital zircon record in the metasedimentary rocks included in this study demonstrate the Precambrian rocks investigated, where tectonic setting is the subject of debate, display similar convergent or collisional zircon patterns to those formed in much younger sedimentary sequences where the geodynamic environment is clearly defined
The Proterozoic-Phanerozoic transition is marked by an increase in the proportion of rocks displaying a collisional orogenic signature (Fig. 2)
Summary
The evolution and the growth of the continental crust is inextricably linked to the evolution of Earth’s geodynamic processes. The detrital zircon record within the continental crust, as well as the isotopic composition of this crust, indicates that the amount of juvenile felsic material decreased with time and that in geologically recent times, the generation of new crust is balanced by recycling of the crust back into the mantle within subduction zones It cannot always have been so; yet the nature of the crust and the processes of crustal reworking in the Precambrian Earth are not well constrained. In the present Earth, accretion of juvenile material, recycling of crust to the mantle, and crustal reworking by anatexis, all occur in convergent plate boundaries, and in particular in accretionary orogens, which correspond to the compaction of sedimentary wedges and island arcs onto preexisting continental mass. We contrast burial rates of Phanerozoic sediments with relatively well-defined geodynamic settings, with a set of Precambrian rocks from different orogenic belts, where details of the geodynamic processes are less well constrained
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