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Late Silurian bimodal volcanism of southwestern New Brunswick, Canada: Products of continental extension

2002; Geological Society of America; Volume: 114; Issue: 4 Linguagem: Inglês

10.1130/0016-7606(2002)114 2.0.co;2

1943-2674

Nancy A. Van Wagoner, Matthew I. Leybourne, K.A. Dadd, Diane K. Baldwin, Wayne McNeil,

Geological formations and processes

Research Article| April 01, 2002 Late Silurian bimodal volcanism of southwestern New Brunswick, Canada: Products of continental extension Nancy A. Van Wagoner; Nancy A. Van Wagoner 1Acadia University, Department of Geology, Wolfville, Nova Scotia B0P 1X0, Canada Search for other works by this author on: GSW Google Scholar Matthew I. Leybourne; Matthew I. Leybourne 2Department of Geosciences, University of Texas at Dallas, Box 830688, Richardson, Texas 75083-0688, USA Search for other works by this author on: GSW Google Scholar Kelsie A. Dadd; Kelsie A. Dadd 3Department of Earth and Planetary Sciences, Macquarie University, Sydney, New South Wales 2109, Australia Search for other works by this author on: GSW Google Scholar Diane K. Baldwin; Diane K. Baldwin 4Acadia University, Department of Geology, Wolfville, Nova Scotia B0P 1X0, Canada Search for other works by this author on: GSW Google Scholar Wayne McNeil Wayne McNeil 4Acadia University, Department of Geology, Wolfville, Nova Scotia B0P 1X0, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Nancy A. Van Wagoner 1Acadia University, Department of Geology, Wolfville, Nova Scotia B0P 1X0, Canada Matthew I. Leybourne 2Department of Geosciences, University of Texas at Dallas, Box 830688, Richardson, Texas 75083-0688, USA Kelsie A. Dadd 3Department of Earth and Planetary Sciences, Macquarie University, Sydney, New South Wales 2109, Australia Diane K. Baldwin 4Acadia University, Department of Geology, Wolfville, Nova Scotia B0P 1X0, Canada Wayne McNeil 4Acadia University, Department of Geology, Wolfville, Nova Scotia B0P 1X0, Canada Publisher: Geological Society of America Received: 09 Aug 2000 Revision Received: 11 Oct 2001 Accepted: 11 Oct 2001 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2002) 114 (4): 400–418. https://doi.org/10.1130/0016-7606(2002)114 2.0.CO;2 Article history Received: 09 Aug 2000 Revision Received: 11 Oct 2001 Accepted: 11 Oct 2001 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Nancy A. Van Wagoner, Matthew I. Leybourne, Kelsie A. Dadd, Diane K. Baldwin, Wayne McNeil; Late Silurian bimodal volcanism of southwestern New Brunswick, Canada: Products of continental extension. GSA Bulletin 2002;; 114 (4): 400–418. doi: https://doi.org/10.1130/0016-7606(2002)114 2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Silurian–Devonian bimodal volcanism—a common feature of the northern Appalachians of the northeastern United States and eastern Canada—forms major belts of igneous rocks including the Coastal volcanic belt of New England and New Brunswick. The Coastal volcanic belt is one of the largest bimodal volcanic provinces in the world. Controversy remains regarding the tectonic setting of this volcanism; suggestions range from volcanic arc, to extensional continental rift, transpressional basin, backarc, or plume-modified subduction zone. The mapped Passamaquoddy Bay volcanic sequence of the Coastal volcanic belt of southwestern New Brunswick has a minimum thickness of 4 km and comprises 63 lithologic units that are divided into four distinct cycles of mafic-felsic volcanism. A preliminary U-Pb zircon date indicates an age of 423 Ma, similar to the age of the Cranberry Island bimodal volcanic series of the Coastal volcanic belt in Maine. Our analysis of 115 volcanic rocks for major and trace element concentrations indicates that the sequence is subalkalic and bimodal (basalt-rhyolite) with within-plate tectonic affinities. Most mafic rocks range in composition from basalt to basaltic andesite. The Mg# [defined as 100 × MgO/(MgO + FeO), where FeO = FeOT × 0.9] of the basalts ranges from 30 to 70, and there is a trend toward more primitive compositions upward in the section. The light rare earth element abundances of the basalts are enriched to levels of 30–130 times chondritic values. The flows are enriched in incompatible elements with respect to primitive mantle and show distinct Nb, Hf, and Sr anomalies. We interpret the basalts to be mantle melts modified by crustal contamination and mantle metasomatism from a previous subduction event. Most of the chemical variation can be explained by replenishment and fractionation of small magma chambers. The rhyolitic rocks are crustal melts, modified by crystal fractionation. Within each of the rhyolitic cycles there is an upward trend toward more evolved compositions as a result of an evolving magma chamber and magma-chamber zonation. We suggest that the rocks were erupted in an extensional environment and that there was a significant zone of continental extension during the Late Silurian in the northern Appalachians. However, controversy remains regarding the precise nature of the tectonic setting and the duration and extent of this volcanism. 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