| The duality of orogenic belts (2007) | |||||||||||||||
Abstract | |||||||||||||||
| world is proposed, based in first instance on the facies series of the metamorphic rocks. The Hercynian and Alpine orogens of Europe are reviewed in detail and are found to differ respectively in several ways: (1) low pressure metamorphism with andalusite and cordierite vs. high pressure metamorphism with glaucophane, sodium pyroxene, lawsonite and kyanite, (2) thin vs. thick metamorphic zones, (3) abundant vs. few granites. and migmatites, (4) few vs. abundant ophiolites and, ultrabasites,. (5) broad vs. narrow orogen, (6) small vs. large uplift, (7) scarce vs. dominant nappe structures. The Caledonian orogen of Europe is examined and found to be intermediate in nature between the "Hercynotype" and "Alpinotype" orogens. The Svecofennian- Karelian, belt of the Baltic shield is found to be a typical Hercynotype orogen. The paired metamorphic belts of the Circumpacific region appear to be a new element in the earth's history and tend to emphasize the peculiar character of .the Pacific Ocean. It seems probable that the thermal history of the earth has not appreciably changed during the last 2500 million years. The pressure-temperature fields of the various facies and facies series based on-field and experimental work are, discussed. Finally the causes of regional metamorphism are considered. | |||||||||||||||
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