Stratigraphy and geochemistry of Ordovician volcanic rocks of the Eel River area, west-central New Brunswick

Abstract

Early Paleozoic turbiditic sedimentary rocks and submarine volcanic-arc rocks in the Eel River area have been designated, respectively, as the Woodstock and Meductic groups and divided into six formations. The Woodstock Group includes interbedded Cambrian to Early Ordovician quartz vvacke. sandstone, and shale of the Baskahegan Formation and overlying Early Ordovician silty mudstone and shale of the Bright Eye Brook Formation. The conformably overlying Meductic Group is divided into the Early Ordovician Porten Road Formation (mainly rhyolite). Eel River Formation (mainly andesite), and Oak Mountain Formation (basalt), and Late Ordovician Belle Lake Formation (feldspathic wacke and shale).Pyroxene-bearing, low-silica andesite in the lower part of the Porten Road Formation is highly enriched in LREE and LFSE. and depleted in HFSE relative to MORB. evidence of subduction in a compressional-continental arc setting. The upper part of the Porten Road Formation comprises an interlayered sequence of quartz-rich rhyolite and quartz-poor dacite. likely derived from melting of continental crust. The Eel River Formation contains hornblende-bearing, high-silica andesite moderately enriched in LFSE. Calc-alkaline basalt from the overlying Oak Mountain Formation includes low-and highalumina basalt varieties like those formed in an extensional-continental arc setting. Volcanic activity in the Meductic Group ceased in the later part of the Early Ordovician as the arc rifted and the subduction zone migrated northwestward with the opening of the Tetagouche back-arc basin. L'andesite a faible teneur en silice qui renferme de la pyroxene dans la partie inferieure de la Formation de Porten Road est fortement enrichie en ETRL (elements de terres rares legers) et en EF1C (elements a faible intensite de champ) et pauvre en EHIC (elements a haute intensite de champ) comparativement aux BDMO (basaltes de la dorsale medio-oceanique). ce qui temoigne d'une subduction au cours de Fetablissement d'un arc compressif-continental. La partie superieure de la Formation de Porten Road comporte une sequence interstratifiee de rhyolite riche en quartz et de dacite pauvre en quartz provenant vraisemblablement de la fusion de la croute continentale. La Formation d'Eel River renferme de Fandesite riche en silice a hornblende moyennement enrichie d'EFIC. Le basalte ealco-alcalin de la Formation sus-jacente d'Oak Mountain comprend des basaltes a faible et forte teneur en alumine comme ceux formes lors de Fetablissement d'un arc d'accretioncontinental. L'activite volcanique dans le groupe de Meductic a cesse vers la fin de FOrdovicien inferieur lorsque Fare s'est effondre et que la zone de subduction a migre vers le nord-ouest avec I'ouverture du bassin marginal de Tetagouche. Traduit par la redaction I n t r o d u c t io nThe Eel River area of west-central New Brunswick (Figs. 1, 2) is underlain by Ordovician volcanic rocks that provide important constraints on the Paleozoic tectonic history of the Appalachian orogen (van Staal and Fyffe 1995a). These vo...

A Review of Proterozoic to Early Paleozoic Lithotectonic Terranes in New Brunswick, Canada and their Tectonic Evolution during Penobscot, Taconic, Salinic and Acadian Orogenesis

“…The Meductic volcanic rocks possess geochemical characteristics consistent with an arc setting; therefore, they are interpreted to represent an arc that formed above a subduction zone dipping to the southeast beneath the leading edge of Ganderia (Dostal 1989;Fyffe and Swinden 1991;Fyffe 1991, 1995;Fyffe 2001). The disconformity at the base of the Belle Lake Formation (Fig.…”

“…2, 5) consists of a quartzose sedimentary sequence and an overlying volcanic sequence, referred to as the Woodstock and Meductic groups, respectively (Fyffe 2001). The Woodstock Group includes quartzose sandstone and shale of the Baskahegan Lake Formation and conformably overlying carbonaceous black shale of the Bright Eye Brook Formation, and is a direct correlative of the Miramichi Group (Fig.…”

“…Since 1990, in particular, a large amount of new stratigraphic, geochemical, geochronological, and structural data have been collected by van Staal and co-workers at the Geological Survey of Canada; Sandra Barr and students at Acadia University; Damian Nance at Ohio University; and staff of the Geological Surveys Branch at the New Brunswick Department of Natural Resources. This work involved detailed mapping of dozens of quadrangles throughout southern New Brunswick (Fyffe and Riva 1990;McLeod et al 1992McLeod et al , 2001McLeod 1995McLeod , 1997White 1996a, b, 1999;Johnson and McLeod 1996;White and Barr 1996;Currie and McNicoll 1999;Fyffe et al 1999;Fyffe 2001Fyffe , 2005Fyffe and Grant 2001;Barr et al 2002) and northern New Brunswick (Wilson 1990(Wilson , 2000(Wilson , 2002van Staal and Fyffe 1995;van Staal et al 2003;.…”

Geochronology and lithogeochemistry of granitoid rocks from the central part of the Central plutonic belt, New Brunswick, Canada: implications for Sn-W-Mo exploration

“…The Bathurst Supergroup comprises volcanic and sedimentary rocks that were deposited during extension and rifting of the Early to Middle Ordovician, ensialic Popelogan arc, leading to opening of the Tetagouche backarc basin (van Staal et al 2003(van Staal et al , 2016. Early Ordovician, pre-rifting volcanic rocks of the Popelogan arc are exposed in the southwestern part of the Miramichi inlier near Woodstock, where they are assigned to the Meductic Group (Fyffe 2001), whereas Middle Ordovician, postrifting arc volcanic rocks are exposed in the Popelogan inlier in northern New Brunswick and assigned to the Balmoral Group (Wilson 2003) (Fig. 1 inset).…”

Arenig volcanic and sedimentary strata, central New Brunswick and eastern Maine

“…The subduction zone changed from northwest-dipping during Penobscot time to southeast-dipping during Popelogan time. Oldest rocks assigned to the Popelogan Arc are volcanic rocks of the Meductic Group within the Miramichi terrane about 80 km southwest of the Napadogan area (Fyffe 2001). The volcanic rocks grade broadly from rhyolite stratigraphically upward to basalt and intruded arc-setting granite, all of early to middle Arenig age, and include intercalated green and maroon manganiferous chert and slate.…”