Over the past few decades, the Chain Lakes massif and overlying Boil Mountain complex, west-central Maine, have been interpreted in several mutually exclusive ways. For example, the massif has been described as an early Paleozoic fanglomerate and as Precambrian basement, as exotic to North America and as derived from Laurentia, as a high-grade metamorphic terrain and as a low-grade metamorphic terrain. The Boil Mountain complex has been interpreted as a large nappe thrust from the southeast and as an independent block thrust from the northwest. In addition, although the complex has been labeled as part of an ophiolite, it lacks many characteristic features. Other unresolved problems include the relationship between the volcanic and plutonic portions of the Boil Mountain complex, why the contact between the Chain Lakes massif and the Boil Mountain Complex does not appear to be tectonic if the complex was thrust upon the massif, the protolith for the extensive granofels within the massif, and the ages of tectonism, metamorphism, and igneous activity. Use of microstructural, petrologic, and geochronologic techniques not previously applied to this area has highlighted inconsistencies in past interpretations and will aid in addressing the above problems.

Determining the extent, timing of juxtaposition, and provenance of terranes within an accretionary orogenic belt is vital for characterizing the lithosphere-scale metamorphic and deformational processes that take place during terrane collision, and an understanding of the geologic history of the individual blocks that may constitute the terranes is a prerequisite for regional interpretations of those features. The Chain Lakes massif and adjacent Boil Mountain complex, one of the largest exposures of early Paleozoic bedrock within several hundred km along strike, lie in a position critical to regional interpretations of the northern Appalachians, but their origin and history, and therefore their role in Appalachian orogenesis, remain enigmatic. Resolution of unanswered questions concerning the relationship between the Chain Lakes massif, Boil Mountain complex, and surrounding units in west-central Maine will provide insight into Appalachian orogenesis and the general process of accretionary orogenesis.