Rb/Sr Study of the Stony Creek Granite, Southern Connecticut: A Case for Limited Remobilization

Abstract

The Stony Creek granite is massive to migmatitic rock that crops out in the core of the Stony Creek dome, the most southerly exposed dome along the Branson Hill anti-clinorium. Rb/Sr data do not yield a precise isochron but indicate that the granite or its precursor is 616 ± 78 m.y. old, and perhaps originated during the Avalonian orogeny. The Stony Creek granite apparently was remobilized and emplaced at a higher structural level, possibly as a mantled gneiss dome, during one or more of the later Paleozoic orogenies (Taconian, Acadian, and perhaps Alleghanian) that formed the Bronson Hill anticlinorium and associated Oliverian domes. Local migration of Rb during Late Pennsylvanian to Permian (Alleghanian) metamorphism is sufficient to explain the major discordances in the data, but earlier redistribution of Rb and Sr cannot be disproven. We suggest that the remobilization of the Stony Creek granite was mainly by ductile flow of solid rock and did not involve extensive melting, mixing, or differentiation.