S-TYPE GRANITOIDS PRODUCED BY SEDIMENT FUSION IN THE THERMAL AUREOLE OF EARLY JURASSIC DIABASE IN THE NEWARK BASIN

I-, S- and A- type granites plotted on mantle-normalized spider diagrams show similar negative slopes, HREE enrichment, LREE depletion, and negative Nb, P, Ti anomalies. It is almost impossible to differentiate these granite types on the basis of spider diagrams alone. However chemical compositional distinctions exist, particularly some REE ratios, but isotopic data is crucial to avoid ambiguity, and there are few unequivocal standards to use as a basis for comparison. We therefore offer the complete chemical composition, together with isotopic data, of the fusion product of a Triassic sedimentary rock as a new unambiguous S-type granite standard. The S-type granite occurs at the lower contact with the Palisades sill, Fort Lee, NJ. and is the leucosome component of a migmatite that was formed during the intrusion of the sill. Consistent with most other S-Type granites the Fort Lee occurrence is peraluminous and corundum normative. Similar granitoids were also studied by us over the last 20 years at: (1) a partially fused xenolith in the Palisades sill at Graniteville, S.I., NY ; (2) the I-95 road cut through the Palisades sill in NJ; (3) the thermal aureole of the Lambertville sill at Brookville, NJ; (4) the trondhjemite-syenite dikes in the thermal aureole of the basaltic plug of Snake (Laurel)Hill near Secaucus, NJ; and (5) the fusion zone of siltstone at the base of the Orange Mountain basalt in the UBC quarry, NJ. We have concluded on the basis of field observations, petrographic data, geochemical data and mineralogical data that each of these leucocratic rocks has a sedimentary precursor and therefore would be considered S-type granitoids. Furthermore, these S-type granitoids have a distinct trace element pattern which is different from that of the enclosing early Jurassic diabase or basalt and are not differentiates of the tholeiitic magma.