JURASSIC IGNEOUS ACTIVITY OF THE WHITE MOUNTAIN MAGMA SERIES AND THE CENTRAL ATLANTIC MAGMATIC PROVINCE: A TEMPORAL AND POSSIBLE GEODYNAMIC CONNECTION?

The igneous complexes collectively termed the White Mountain Magma Series of New England forms the largest expression of post-orogenic felsic magmatism on the Eastern North American Margin (ENAM). Much debate has surrounded their origin, age distribution, and relationship to other regional features and events. Historically, this NNE-SSW trending series of igneous bodies has been assigned three broad age groupings which are now suspect because of vastly improved radiosotopic techniques: 1) ~230 Ma; 2) ~200 – 155 Ma; 3) ~130 – 100 Ma.

Here, we focus on the Jurassic interval of magmatism and provide constraints on the timing and duration of its emplacement. Our new data, obtained from zircon U-Pb measurements via CA-TIMS and LA-ICP-MS, demonstrate that both the intrusive and extrusive complexes associated with this event were emplaced significantly earlier and over a much shorter interval of time than currently published ages suggest. Several key units have dates only a few million years younger than the peak emplacement age of the mafic Central Atlantic Magmatic Province (CAMP). The apparent spatial and temporal proximity of this felsic event to the CAMP flood basalts and intrusions suggests the possibility of a direct geodynamic linkage and motivates the development of testable tectonic hypotheses, e.g., felsic plutonism caused by plume-head driven subduction or delamination.