Composition, Structure and Evolution of the Early Precambrian Lower Continental Crust: Constraints from Geological Observations and Age Relationships
- Muawia Barazangi and
- Larry Brown
Published Online: 15 MAR 2013
Copyright 1986 by the American Geophysical Union.
Reflection Seismology: The Continental Crust
How to Cite
Kröner, A. (1986) Composition, Structure and Evolution of the Early Precambrian Lower Continental Crust: Constraints from Geological Observations and Age Relationships, in Reflection Seismology: The Continental Crust (eds M. Barazangi and L. Brown), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD014p0107
- Published Online: 15 MAR 2013
- Published Print: 1 JAN 1986
Print ISBN: 9780875905143
Online ISBN: 9781118670118
- Seismic reflection method—Congresses
Ancient granulite terranes have been interpreted as segments of juvenile crust, added to the continents during accretion along active plate margins. I review the geology and age relationships in the major early Precambrian granulite provinces in the light of this model and conclude that the majority of high-grade terranes display rock assemblages and structures that are unlike those found in modern accretion belts. In Archean terranes age data and isotopic systematics also show that granulite formation preceded greenstone belt formation significantly in the majority of cases examined and that many high-grade complexes have long deformational histories extending over hundreds of Ma. Shallow-water metasediments of continental character predominate in many granulite terranes and display a surprising continuity of lithological layering as exemplified by the supracrustal assemblages in Sri Lanka. I suggest that many of these layers and associated recumbent structures and thrusts constitute near-horizontal seismic reflectors as seen in lower crustal seismic profiles. Granulites may form in a variety of tectonic settings that are all compatible with the plate tectonic concept. However, oversimplification and gross generalization of granulite genesis do not contribute to a better understanding of the evolution of the ancient lower continental crust.