Geochemistry of the Neoproterozoic Metasedimentary Gamble Brook Formation, Avalon Terrane, Nova Scotia: Evidence for a Rifted‐Arc Environment along the West Gondwanan Margin of Rodinia

摘要: Abstract The Neoproterozoic Gamble Brook Formation in the Avalon Terrane of Nova Scotia consists quartzitic, pelitic, and psammitic metasedimentary rocks. formation is generally interpreted to have been deposited an Atlantic‐type passive margin setting along Amazonian Rodinia before main ca. 650–550‐Ma phase Avalonian subduction‐related magmatism. geochemical Sm‐Nd isotopic signature these rocks, however, shows that although quartzites are predominantly derived from ancient cratonic basement, pelites psammites were moderately fractionated mafic intermediate proto‐Avalonian crust. two contrasting sources for rocks incompatible with a instead reflect deposition basin within rifted‐arc environment. Taken as whole, Gondwana preserves evidence episodic subduction western Pacific‐like between 1000 a...