Direct dating of gold by radiogenic helium: Testing the method on gold from Diamantina, Minas Gerais, Brazil
ABSTRACT New analytical developments have made radiogenic helium (He-4) applicable to archeological gold artifacts for age determinations. Here we report the application of the U/Th-He-4 method to the direct dating of gold from the historically important gold deposit in Diamantina, Minas Gerais, Brazil. The U/Th-He-4 age of 515 +/- 55 Ma for the Diamantina gold is corroborated by a new U/Pb age of 524 +/- 16 Ma for rutile recovered from auriferous pockets. These ages tie the Diamantina gold mineralization to the Brasiliano orogenic event, in the context of the Gondwana amalgamation. Our results indicate that U/Th-He-4 dating of gold is possible, opening new perspectives for the dating of gold deposits without assuming contemporaneity between gold and datable hydrothermal minerals.