CHARACTERISTICS OF ORANGE CALCITE BODIES IN THE WESTERN NEW JERSEY HIGHLANDS

Rare bodies of calcite that are distinctively colored from pale orange to deep orange to salmon pink occur within Mesoproterozoic rocks of the New Jersey Highlands in Sussex County. Field relationships, trace element geochemistry, and petrographic analysis were conducted on orange calcite bodies at the Sterling Hill zinc mine near Ogdensburg, and the Hamburg Stone Quarry near the town of Hamburg. The Sterling Hill locality is hosted by the Franklin Marble, a narrow band of graphitic marble that was metamorphosed to granulite facies during the Ottowan phase of the Grenville Orogeny (ca.1.09 to 1.03 Ga). Orange calcite bodies at Sterling Hill crop out on a ridge to the south of the main mine workings. They occur as concordant pods within a 6 meter wide interval adjacent to a wide band of zincian calc-silicate strata. Mineralogically, the orange calcite pods are simple: >97% calcite, along with accessory norbergite, clinopyroxene, hornblende, and gahnite. Nearby unaltered Franklin Marble is composed of >95% calcite, with accessory clinopyroxene, hornblende, and graphite. The orange calcite commonly is intergrown and rimmed by white calcite. Trace element compositions of orange and white calcite samples, as determined by ICP-MS, are indistinguishable; they contain an average of 2810ppm Mn, compared with 49600ppm Mn in an adjacent ore-bearing horizon, and approximately 100ppm in the unaltered Franklin Marble. Example metal concentrations in the orange calcite bodies include 50ppm As, 432ppm Ba, 15ppm Cd, 377ppm Pb, 765ppm Sr, 52 ppm Zn. In contrast, the Hamburg Quarry orange calcite contains ~300ppm Sr, 35ppm As, and <10ppm Ba, Pb, and Zn. The Hamburg orange calcite contains an average of 139ppm La and 92ppm Nd, approximately 15x and 12x the respective values at Sterling Hill. The orange calcite bodies in the Hamburg Quarry have distinctly different field relationships, occurring as discordant, highly deformed bodies that cut meta-tonalite. These orange calcite bodies are mineralogically more complex with accessory apatite and titanite and calc-silicate selvages. The contrast in composition, mineral assemblages, and field relationships of these two orange calcite occurrences suggest differing genesis, and color does not appear to be related simply to the presence of a specific coloring metal.