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The New Jersey Highlands preserve a diverse assemblage of Mesoproterozoic rocks, whose geologic evolution correlates in part to other Grenville terranes in eastern North America, mainly north of the Blue Ridge. Voluminous undated—but postulated to be >1200 Ma—calc-alkaline metaplutonic and metavolcanic rocks of the Losee Metamorphic Suite were formed in a continental-margin magmatic arc, and metamorphosed supracrustal rocks >1174 Ma were formed along eastern Laurentia in a marginal back-arc basin. They include terrigenous to shallow marine metasand-stones, a shelf sequence of sand-dominated metaclastic rocks, stromatolitic marble, locally pillowed mafic volcanics, and deep-water volcanogenic metagraywacke. Sub-duction and calc-alkaline magmatism had ceased by 1176 Ma, but timing of accretion of the arc complex to Laurentia is uncertain.

Between 1160 and 1130 Ma, supracrustal rocks were intruded by thin sheets and dikes of meta-anorthosite and megacrystic amphibolites likely coeval with anorthosite, mangerite, charnockite, granite (AMCG) magmatism in the Adirondack Highlands. Meta-anorthosite and megacrystic amphibolites in New Jersey were intruded by Atype granite of the 1110 ± 25 Ma Byram and 1095 ± 9 Ma Lake Hopatcong Intrusive Suites. Emplacement of these suites was followed by upper amphibolite- to granulite-facies metamorphism at 1090–1030 Ma, during the Ottawan orogeny. Sheets of late synorogenic microperthite alaskite were emplaced during the latter part of Ottawan orogenesis. Postorogenic 1020 ± 4 Ma Mount Eve Granite and undeformed 1029 ± 1 Ma trondhjemite date the close of the Ottawan orogeny in the New Jersey Highlands. Undeformed discordant pegmatites and small granite bodies were emplaced between 1004 and 989 Ma.

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