Abstract

Outcrop scale mapping indicates that the contact zone between Marcy anorthosite and Tupper-Saranac mangerite on Baker Mountain in northeastern New York consists of mangerite dikes cutting both anorthosite and a granofelsic jotunite. All three units are intruded by younger granitic dikes that have produced contact aureoles in the anorthosite, and all of these rocks were metamorphosed and deformed during the Grenville orogeny. Postorogenic mafic dikes cut all other rocks on Baker Mountain. Patches of exceptionally calcic plagioclase reach a composition of An80 in the Marcy anorthosite.

Rare-earth element analysis reveals that both anorthosite and mangerite have positive europium anomalies, whereas the jotunite and a skarn inclusion have no europium anomalies. Both mangerite and jotunite have high total rare-earth abundances compared to anorthosite.

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