Circum-Superior Belt event in Australia and 1,860 million year old magmatism of the Mashonaland event in Africa. The other questionable suggestion related to the Circum-Superior Belt is the existence of a suggested 1,900 million year old global superplume event. The long Labrador Trough, extending from Ungava Bay through Quebec and Labrador, includes two volcano-sedimentary series, the first ranging from 2,170 to 2,140 million years old and second ranging from 1,883 to 1,870 million years old. This magmatism is considered to have formed as a result of back-arc volcanism. The youngest magmatic series (1883-1870 Ma) contains 1,880 million-year-old carbonatites and lamprophyres. 1,883 to
Circum-Superior Belt margin. The last collision occurred on the southeastern portion of the Superior craton to produce the Grenville orogeny 1,100 million years ago. Because most of the Circum-Superior Belt was formed by widespread mafic-ultramafic magmatism 1,884 to 1,864 million years ago along the Superior craton margin during these orogenies, a number of different suggestions have been made to explain the questionable origins of this large igneous province. It is also not clear if the Circum-Superior Belt has a single origin or it has several origins. Suggestions include back-arc rifting, foredeep flexure, mantle plumes and the breakup of a microcontinent. The geochemical