Autonomous anorthosites of the Anabar Shield: Age, geochemistry, and formation mechanism

摘要

The new high-accuracy data on U-Pb zircon geochronology, Sm-Nd systematics, and geochemistry of anorthosites of the Anabar Shield are discussed. It is established that anorthosite massifs are composed of gabbro-anorthosites (1.96 Ga old) and oligoclasites (1.93 Ga old) in association with monzodiorites (1.84-1.90 Ga old) and porphyroblastic granites. These rocks were generated in the Archean (3.2-2.7 Ga ago) in the lower crust from quartz-diorite melts under the plume tectonics regime in line with the filterpressing mechanism. The rocks were successively exhumed to upper levels of the crust owing to the Paleoproterozoic impact-triggered process to form a tectonically juxtaposed complementary magmatic complex.