Original paper

Geochemical constraints on the origin and evolution of early Mesozoic dikes in Atlantic Canada

Dostal, Jaroslav; Durning, Michael

European Journal of Mineralogy Volume 10 Number 1 (1998), p. 79 - 94

56 references

published: Jan 26, 1998
manuscript accepted: Sep 25, 1997
manuscript received: Aug 20, 1996

DOI: 10.1127/ejm/10/1/0079

BibTeX file

ArtNo. ESP147051001009, Price: 29.00 €

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Abstract Two prominent early Mesozoic ( ~ 201 Ma) diabase dikes in eastern Canada (Shelburne dike of Nova Scotia and Caraquet dike of New Brunswick) are part of the eastern North America (ENA) basalt province between Alabama and Newfoundland. The dikes form lineaments more than 200 km long. They consist of quartz-normative tholeiitic basalts. In contrast to the Shelburne dike, the Caraquet dike contains modal olivine and has a lower content of incompatible trace elements with lower (La/Yb)n (1.6-1.8 vs. 3.1-3.9) and isotopically less enriched Sr and Nd isotopes. The dikes have low Mg#, Ni and Cr, indicating that the magmas underwent extensive fractionation. The magmas were variably contaminated with continental crust, particularly the Shelburne dike as evidenced by high Th/La and its radiogenic initial Sr isotope ratios. The Shelburne dike could have been derived from the Caraquet-type magma by a crustal assimilationfractional crystallization process. The Caraquet magma is inferred to be derived from a sub-continental lithospheric spinel-bearing mantle. The Shelburne and Caraquet dikes and possibly other ENA basalts were probably generated in response to lithospheric extension associated with the opening of the North Atlantic over a region of anomalously hot mantle related to a mantle plume