An Early Triassic Ar-40/Ar-39 age for a camptonite dyke in Cambridge, Massachusetts, USA

作者：Ross Martin E^*

来源：Atlantic Geology, 2010, 46: 127-135.

DOI：10.4138/atlgeol.2010.007

A 2.4 m-thick megacryst- and xenolith-rich camptonite dyke briefly exposed during excavation of a subway station at Porter Square in Cambridge, Massachusetts, was sampled for petrological study and radiometric dating to constrain its age. The sample yielded a well-defined Ar-40/Ar-39 age of 246 +/- 4 Ma using separates prepared from a ferro-kaersutite mega-phenocryst. This age is the oldest yet reported for a Coastal New England province lamprophyric dyke. The dyke likely reflects regional extension in Avalonia during the initial rifting stage of Pangea to form the North Atlantic Ocean basin. This new age further confirms that mantle upwelling began early in the Late Permian to Triassic as a precursor to the breakup of Pangea some 40 million years later.

• 出版日期2010
• 单位东北大学