| The multi-staged Abbot Breccia in Central Maine is in sharp contact with the Early Devonian Madrid Formation, the predominant provenance of fragments. The four mineral assemblages of the hydrothermal cement are predominantly composed of either biotite, chlorite, albite, or quartz, with lesser calcite or muscovite. The larger second-stage breccia is cemented by the quartz assemblage with other assemblages dominant between aligned fragments found along the contacts of the breccia. Potassic and phyllic hydrothermal alterations of greenschist minerals within the angular fragments and the absence of metamorphism or deformation fabrics in the matrix indicate that the breccia formed after folding and metamorphism of the Madrid during the Acadian Orogeny. The paragenetic sequences of cement and alteration assemblages are comparable to that of alkaline porphyry copper deposits, suggesting formation by a nearby felsic pluton. |
