A PALEO-MESOPROTEROZOIC SUPERCONTINENT: ASSEMBLY, GROWTH AND BREAKUP

Abstract

Geological and paleomagnetic data support the hypothesis that a Paleo-Mesoproterozoic supercontinent, referred to as Columbia, existed before the formation of Rodinia. This pre-Rodinia supercontinent was assembled along global-scale 2.1–1.8 Ga collisional orogens and contained almost all of Earth's continental blocks. Following its final assembly at ∼1.8 Ga, the supercontinent Columbia underwent long-lived (1.8–1.3 Ga), subduction-related growth via accretion at key continental margins, forming a 1.8–1.3 Ga large magmatic accretionary belt along the present-day southern margin of North America, Greenland and Baltica. It includes the 1.8–1.7 Ga Yavapai, Central Plains and Makkovikian Belts, 1.7–1.6 Ga Mazatzal and Labradorian Belts, 1.5–1.3 Ga St. Francois and Spavinaw Belts and 1.3–1.2 Ga Elzevirian Belt in North America; the 1.8–1.7 Ga Ketilidian Belt in Greenland; and the 1.8–1.7-Transscandinavian Igneous Belt, 1.7–1.6 Ga Kongsberggian–Gothian Belt, and 1.5–1.3 Ga Southwest Sweden Granitoid Belt in Baltica. Other cratonic blocks also underwent marginal outgrowth at about the same time. In South America, a 1.8–1.3 Ga accretionary zone occurs along the western margin of the Amazonia Craton, represented by the Rio Negro, Juruena and Rondonian Belts. In Australia, 1.8–1.5 Ga accretionary magmatic belts, including the Arunta, Mt. Isa, Georgetown, Coen and Broken Hill Belts, occur surrounding the southern and eastern margins of the North Australia Craton and the eastern margin of the Gawler Craton. In China, a 1.8–1.4 Ga accretionary magmatic zone, called the Xiong'er belt (Group), extends along the southern margin of the North China Craton. Fragmentation of this supercontinent began about 1.6 Ga ago, associated with continental rifting along the western margin of Laurentia (Belt–Purcell Supergroup), southern margin of Baltica (Telemark Supergroup), southeastern margin of Siberia (Riphean aulacogens), northwestern margin of South Africa (Kalahari Copper Belt), and northern margin of North China (Zhaertai–Bayan Obo Belt). The fragmentation corresponded with widespread anorogenic magmatic activity, forming anorthosite–mangerite–charnockite–granite (AMCG) suites in North America, Baltica, Amazonia and North China, and continued until the final breakup of the supercontinent at about 1.3–1.2 Ga, marked by the emplacement of the 1.27 Ga MacKenzie and 1.24 Ga Sudbury mafic dike swarms in North America.