Geochemistry and stratigraphic relations of middle Proterozoic rocks of the New Jersey Highlands

Abstract

The New Jersey Highlands are underlain principally by Middle Proterozoic orthogneiss, paragneiss, and marble that were metamorphosed to upper amphibolite to hornblendegranulite facies and were intruded by granitoid rocks. The oldest rocks are dacitic, tonalitic, and trondhjemitic gneiss and granite of calc-alkaline affinity and metabasalt of the Losee Metamorphic Suite. They are associated spatially with quartz-rich and quartz-poor charnockitic rocks. Field relationships and geochemical data support a cogenetic interpretation for the dacitic, tonalitic, and trondhjemitic rocks and the charnockitic rocks. They are herein all included in the Losee Metamorphic Suite. The rocks of the Losee Metamorphic Suite form a basement assemblage that is unconformably overlain by a layered sequence of supracrustal rocks that consist of quartzofeldspathic gneiss of arkosic and (or) graywacke composition, metaquartzite, calc-silicate gneiss, and marble. Quartzofeldspathic gneiss and calc-silicate gneiss are ubiquitous, but marble occurs mainly in the western Highlands. Metaquartzite occurs as thin lenses and layers throughout the Highlands and provides an excellent marker. Amphibolite formed from different protoliths is widespread and is found in virtually all Middle Proterozoic rocks. Widespread synorogenic granitoids include the hornblende-and biotite-bearing rocks of the Byram Intrusive Suite, dated at between 1,116±41 Ma and 1,088±41 Ma, and the clinopyroxene-bearing rocks of the Lake Hopatcong Intrusive Suite, dated at 1,095±9 Ma. Both have similar major-and trace-element abundances and are interpreted as having fractionated from the same magma. They are included as suites in the Vernon Supersuite. The postorogenic Mount Eve Granite has been dated at 1,020±4 Ma and is confined to the extreme northern Highlands. Middle Proterozoic rocks are very locally unconformably overlain by weakly metamorphosed Late Proterozoic rocks of the Chestnut Hill Formation and are intruded by abundant diabase dikes of Late Proterozoic age. The Proterozoic rocks are unconformably overlain by the Lower Cambrian Hardyston Quartzite.

Metal contamination and filtering in soil from an iron (magnetite) mine–smelter complex in the critical Hudson Highlands watershed, New York

“…Both Ca and Ti contents are higher in the most impacted Group A soils than in Group B by 1.69 and 1.49, respectively. The Ti content in the slag (2.95 wt%, Table 4) is higher than the average Ti content (0.64 wt%) in the Highlands calc-silicate rocks (Volkert and Drake 1999) suggesting that large amounts of slag (and ash) have been mixed into the soils in the Group A area. Elevated metal concentrations in Group A soils is the result of contaminants from mining and smelting operations.…”

“…Elevated metal concentrations in Group A soils is the result of contaminants from mining and smelting operations. From previous analysis of the New Jersey Highlands rocks by Volkert and Drake (1999), calc-silicate rocks are found to contain between 31 and 97 mg/kg of Cr. Both magnetite (Fe 2?…”

“…O 4 ) and ilmenite (Fe 2? TiO 3 ) minerals are present in calc-silicate rocks (Volkert and Drake 1999), with magnetite more abundant (avg 2.24-3.23 wt%) than ilmenite (avg 1.1-1.37 wt%). Chromite can occur as an accessory mineral with magnetite and ilmenite (IETEG 2005).…”

“…O 4 ) and ilmenite (Fe 2? TiO 3 ) minerals are present in calc-silicate rocks (Volkert and Drake 1999) and Cr can occur with these minerals (Independent Environmental Technical Evaluation Group (IETEG) 2005a, b). These ferrous-bearing minerals oxidize and breakdown releasing Cr to the soils.…”

Le magmatisme de la région de Kwyjibo, Province du Grenville (Canada) : intérêt pour les minéralisations de type fer-oxydes associées

“…Un lien génétique entre le magmatisme et les gisements de type fer-oxydes a été proposé à de nombreuses reprises du fait de la présence à proximité de la plupart des gisements d'intrusions granitiques de même âge que les minéralisations. C'est le cas des monzodiorites quartziques et des granites felsiques de Roxby Downs à proximité d'Olympic Dam (Reeve et al 1990), des granitoïdes calco-alcalins potassiques du pluton Balachey dans le complexe magmatique zone de Great Bear au Canada (Hildebrand 1986), des granodiorites et monzonites calcoalcalines à proximité de Panulcillo, Chili (Hopper et Correa 2000), des granitoïdes calcoalcalins du batholite côtier au Pérou (Vidal et al 1990;Menard 1995;Sillitoe 2003), des monzonites quartziques d'Iron Spring dans le New Jersey (Volkert 1993) ou des monzogranites et syénogranites de Williams et de Naraku, associés à Lightning Creek dans le Nord de l'Australie (Pollard et al 1998;Perring et al 2001). Ces relations spatiales et les données géochimiques sur les isotopes stables et les inclusions fluides ont ainsi conduit à proposer un lien génétique entre magmatisme et minéralisations pour ce type de gisements (Hildebrand 1986;Hitzman et al 1992;Nyström et Henriquez 1994;Sillitoe 2003).…”