Geochemistry and U–Pb geochronology of the Williams Brook area, Tobique–Chaleur zone, New Brunswick: stratigraphic and geotectonic setting of gold mineralization

Sánchez-Mora, Dennis; McFarlane, Christopher R.M.; Walker, James A.; Lentz, David R.

doi:10.1139/cjes-2020-0094

Cited by 1 publication

(1 citation statement)

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“…The age of the Eastport Formation is based on two dates, 421 ± 3 Ma and an informal age of 423±1 Ma (Mohammadi et al 2019 andDadd 2003, respectively), which corresponds to the age range of the Coastal Maine bimodal complexes of 424-420 Ma (Seaman et al 1995(Seaman et al , 2019McLaughlin et al 2003;Churchill-Dickson 2004;Turner and Burrow 2018). In contrast, two age groups of bimodal volcanism are recognized in the northern and central part of the Tobique Volcanic Belt; 422-419 Ma and 417-407 Ma (Wilson et al 2017;Sánchez-Mora et al 2021). The ages of magmatism in the Central Volcanic Belt of Maine, are 407-406 Ma (Rankin and Tucker 1995;Bradley et al 2000) corresponding only with the younger of the two age groups of the Tobique.…”

Section: Introductionmentioning

confidence: 99%

Volcanism of the Late Silurian Eastport Formation of the Coastal Volcanic Belt, Passamaquoddy Bay, New Brunswick

Wagoner¹,

Fyffe

Lentz

et al. 2022

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This field trip is an excursion through the exquisite, nearly pristine exposures of a Silurian, felsic-dominated bimodal volcanic and sedimentary sequence exposed in the Passamaquoddy Bay area of southwestern, New Brunswick (Eastport Formation). These rocks form the northwest extension of the Coastal Volcanic Belt that extends from southwestern New Brunswick to the southern coast of Maine. The sequence is significant because it is part of a large bimodal igneous province with evidence for supervolcano-scale eruptions that began to form during the close of the Salinic Orogeny (about 424 Ma), and continued into the Acadian Orogeny (421–400 Ma). The geochemical characteristic of the rocks can be explained by extension related volcanism but the specific drivers of the extension are uncertain. The Passamaquoddy Bay sequence is 4 km thick and comprises four cycles of basaltic-rhyolitic volcanism. Basaltic volcanism typically precedes rhyolitic volcanism in Cycles 1–3. Cycle 4 represents the waning stages of volcanism and is dominated by peritidal sediments and basaltic volcanics. A spectrum of eruptive and emplacement mechanisms is represented ranging from the Hawaiian and Strombolian-type volcanism of the basaltic flows and pyroclastic scoria deposits, to highly explosive sub-Plinian to Plinian rhyolitic pyroclastic eruptions forming pyroclastic density currents (PDC) and high grade rheomorphic ignimbrites. During this field trip we will examine key exposures illustrating this spectrum of eruptive and emplacement processes, and their diagnostic characteristics, along with evidence for the interaction between mafic and felsic magmas and a variety of peperitic breccias formed as a result of emplacement of flows on wet peritidal sediments. The constraints the depositional setting and voluminous bimodal volcanism places on tectonic models will also be considered.

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