The Trans-Hudson and Trans-North China Orogens: A Comparison Based on Geologic and Geophysical Observations

Similarities and differences between the North American Trans-Hudson orogen (THO), and the Asian Trans-North China orogen (TNCO) have been analyzed. The first-order relationships between these two events are their age, gross spatial scale, and mechanism of orogenesis. Both orogens represent Paleoproterozoic (~1.9-1.8 Ga) collisional events that resulted from ocean closure. Subduction of these oceanic plates led to arc-related magmatism, and ultimately to continental collision and crustal thickening. The present-day geometry of the orogens is also comparable: both have north-south trends, indicating east-west convergence. Although the THO covers 5 times the area of the TNCO (~4600 km x ~400 km versus ~1200 km x ~300 km for TNCO), both orogens are of continental scale. Elevation and Bouguer gravity maps indicate little relationship to tectonic domains in both orogens, which might be related to post-collisional overprinting.

In addition to the similarities, many differences exist between the THO and TNCO. Three Archean cratons collided to form the THO: the Superior, Sask, and Rae-Hearne cratons from east to west. In the TNCO, only two cratons were involved (the Eastern and Western Blocks). The presence of an additional craton in the THO resulted in a much more complex structure than its Chinese analog: the TNCO can be roughly divided into areas of high- and low- metamorphic grade, but the interactions between the three plates in the THO resulted in many different domains within the well-exposed Reindeer zone. Stabilization of the TNCO occurred less than 50 Ma after terminal collision (as evidenced by voluminous sedimentation), while complete stabilization of the THO did not occur until ~100 million years after the final collision.

The Trans-Hudson and Trans-North China orogens are two representative collisions of the Paleoproterozoic. Analysis and comparison of these two events is providing insight into the process of continental growth.