A REVIEW OF EFFORTS TO DETERMINE THE TIMING OF MAFIC DIKE INTRUSION IN THE EASTERN ADIRONDACK MOUNTAINS

Numerous vertical/subvertical mafic dikes cut the 1.1-1.3 billion year old rocks that make up the eastern Adirondack Mountains. Many of the dikes are believed to have formed in the Neoproterozoic when Rodinia broke apart to form the Iapetus Ocean. Others, however, cut through the Cambrian sedimentary rocks exposed on the margins of the Adirondack dome and these are likely Mesozoic-age magmas associated with the opening of the Atlantic Ocean. The precise emplacement age of the two sets of dikes is not well constrained yet this information is important in understanding the timing of rifting. In this presentation, the current geochronological and geochemical data from the Adirondack dikes will be discussed and recent attempts to date the dikes using the ⁴⁰Ar-³⁹Ar dating method will be presented. These data will be placed in the context of other Neoproterozic dikes found on the Laurentian margin.