Could you please give me examples of Proterozoic terranes that do not conform to modern plate tectonism.
Thanks in advance
Dear Mr. Eric, Goodmorning and Fraternal greetings!
Thank you for your question, in fact there are few and very less examples of Proterozoic terranes that do not conform to modern tectonism. However to the best of my knowledge, the explanation is as follows
Proterozoic terranes consisting mainly of subduction related rocks or their derivatives. Proterozoic crustal belts consisting mainly of older materials recycled via sediments or melting as opposed to simple reactivation are not all that common. The best example studied the Damaran belt of Southern Africa is actually just Proterozoic in age 0.75-0.46Ga, thus extending in the Paleozoic.
Although only small remnants of Proterozoic terranes in south western North America are preserved, it is of interest in terms of continental accretion to compare these to Phanerozoic terranes in North America. The most obvious comparison is with the Mesozoic tertiary Cordilleran terranes in Western North America. More than one tectonic setting is commonly represented in Cordilleran terranes and within a given terrane tectonic setting may change with time.
Early Proterozoic terrane of the South west and Meso Cenozoic Cordilleran terranes are similar in that they are composed of mostly Juvenile crust. However the range in crustal formation ages is 250-300 Ma in many Cordilleran terranes, whereas Southwest Proterozoic crustal formation ages within given terranes are generally less than 50Ma.
Dr. D S Subrahmanyam