Isotopic Ages of the Trans-Amazonian Acidic Magmatism and the Nickerie Metamorphic Episode in the Precambrian Basement of Suriname, South America

摘要

Suites of granitoid rocks and acidic volcanics constitute the greater part of the Precambrian basement in Suriname. A Rb-Sr whole-rock isochron analysis on 32 samples (14 plutonic, 17 volcanic, and 1 pegmatite) yields an age of 1810 ± 40 m.y. (120 = 1.47 X 10-11/yr, error with 95 percent confidence level) placing this episode of magmatic activity within the Trans-Amazonian Orogenic cycle. Rb-Sr and K-Ar measurements on micas show that the western part of Suriname and the neighboring southern part of Guyana were affected by a tectonothermal event about 1200 ±100 m.y. ago, the Nickerie Metamorphic Episode.