A peri-Gondwanan arc-back arc complex in Iapetus; Early-Mid Ordovician evolution of the Exploits Group, Newfoundland

O'Brien, B. H.; Swinden, H S; Dunning, G. R.; Williams, S. Henry; O'brien, F. H. C.

doi:10.2475/ajs.297.2.220

Cited by 36 publications

(38 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Dewey and Bird 1971;Kay 1972Kay , 1976Williams 1979;Lorenz 1985;ColemanSadd et al 1992;O'Brien et al 1997;MacLachlan et al 2001;Zagorevski et al 2007Zagorevski et al , 2010, widely regarded to have formed within the Iapetus Ocean (e.g. Williams 1979;Dewey et al 1983).…”

Section: Geologic Settingmentioning

confidence: 99%

“…1), is composed of volcanic, volcaniclastic, and sedimentary rocks of early to medial Ordovician age that formed during closure of part of the Cambrian to Silurian ocean termed proto-Atlantic (Wilson 1966;Dewey and Bird 1971), Protacadic (Kay 1972), Iapetus (McKerrow and Ziegler 1972), or Appalachian (Kidd et al 1978) Ocean, in the peri-Gondwanan part of that ocean (van Staal et al 1998). These strata are adjacent and related to the Dunnage Mélange, a unit proposed by some to be associated with subduction of, or within, the Iapetus Ocean (Dewey and Bird 1971;Kay 1972Kay , 1976Williams 1979;Nelson and Casey 1979;O'Brien et al 1997;van Staal et al 2009). A series of volcanic flows and related rocks that have volcanic arc chemical affinities form the base of the Exploits Group (O'Brien et al 1997; Penobscot Arc of Zagorevski et al 2007Zagorevski et al , 2010.…”

Section: Introductionmentioning

confidence: 99%

“…These strata are adjacent and related to the Dunnage Mélange, a unit proposed by some to be associated with subduction of, or within, the Iapetus Ocean (Dewey and Bird 1971;Kay 1972Kay , 1976Williams 1979;Nelson and Casey 1979;O'Brien et al 1997;van Staal et al 2009). A series of volcanic flows and related rocks that have volcanic arc chemical affinities form the base of the Exploits Group (O'Brien et al 1997; Penobscot Arc of Zagorevski et al 2007Zagorevski et al , 2010. Sedimentary rocks of the middle section of the Exploits Group are largely volcaniclastic turbidite and lesser debris flow deposits of a deep marine setting, intruded abundantly by gabbro sills, and are overlain by a thick volcanic sequence, the Lawrence Head Volcanics (Helwig 1969); Lawrence Head Formation of some later authors, but we use Helwig's original designation in this paper.…”

Section: Introductionmentioning

confidence: 99%

“…Sedimentary rocks of the middle section of the Exploits Group are largely volcaniclastic turbidite and lesser debris flow deposits of a deep marine setting, intruded abundantly by gabbro sills, and are overlain by a thick volcanic sequence, the Lawrence Head Volcanics (Helwig 1969); Lawrence Head Formation of some later authors, but we use Helwig's original designation in this paper. The sedimentary rocks and the Lawrence Head Volcanics have been interpreted either as deposits of a fore-arc basin/arc-trench gap setting (Dewey and Bird 1971;Kay 1972Kay , 1976 or as an extensional basin related to intra-arc or back-arc rifting (Nelson and Casey 1979;O'Brien et al 1997;Zagorevski et al 2007Zagorevski et al , 2010, above a subduction zone interpreted respectively as either northwest-dipping, or southeast-dipping. The volcanic section, the Lawrence Head Volcanics, emplaced at the time of, or very shortly following cessation of arc activity (Kidd et al 1977), has an E-MORB chemical signature (Wasowski and Jacobi 1984;O'Brien et al 1997;Zagorevski et al 2007) and has been suggested as a possible product of spreading ridge subduction (or ridge-trench interaction) by Kidd et al (1977), van Staal et al (1998) and Zagorevski et al (2007Zagorevski et al ( , 2012.…”

Section: Introductionmentioning

confidence: 99%

“…This paper also evaluates the conflicting tectonic models proposed for these rocks (e.g. Kidd et al 1977;Hibbard and Williams 1979;O'Brien et al 1997;Zagorevski et al 2010).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Lawrence Head Volcanics and Dunnage Mélange, Newfoundland Appalachians: Origin by Ordovician Ridge Subduction or in Back-Arc Rift?

Schoonmaker

Kidd

DeLong

et al. 2014

View full text Add to dashboard Cite

SUMMARYThis paper reviews the geological setting and reports new geochemical trace element data from the Ordovician Lawrence Head Volcanics (LHV) and the underlying gabbro sills in the Exploits Group. In combination with existing published analyses and ages of these rocks, the volcanic rocks and sills are indistinguishable in composition and age, and the data are consistent with the hypothesis that they represent the same (mostly E-MORB composition) magmatic event in the early-mid Darriwilian (~465 ± 2 Ma). The LHV and their enclosing strata show regional evidence for: 1) upward decline of volume and grain size of arc-derived volcaniclastic materials over the uppermost interval of turbidite sedimentary strata below the LHV; 2) change to shallow marine conditions locally by the end of the LHV event, followed immediately by significant subsidence, and 3) no evidence of coarse-grained clastic input, nor of normal faulting, during or immediately after LHV magmatism. Ridge-trench interaction (ridge subduction) at a subduction system is consistent with all of these features and spatial distribution of related elements, but a rift (back-arc) origin over a subduction zone can only accommodate the compositions, and is inconsistent with the geological evidence. The Dunnage Mélange (DM) has been interpreted either as olistostromal in a developing back-arc rift basin, or as a subduction accretionary prism. Peraluminous intrusions in the mélange (Coaker Porphyry --CP) are more readily explained by ridge subduction, and a previously reported zircon age (469 ± 4 Ma) is consistent with the age of the LHV and gabbro sills, also interpreted as products of ridge subduction. Localization of the CP in the eastern area of DM, and of most of the large LHV-derived volcanic blocks in the western DM, suggests a slightly younger age, and perhaps a different mechanism, for the origin of the western DM. HAROLD WILLIAMS SERIESGeoscience Canada, v. 41, http://dx

show abstract

Section: Geologic Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…This paper also evaluates the conflicting tectonic models proposed for these rocks (e.g. Kidd et al 1977;Hibbard and Williams 1979;O'Brien et al 1997;Zagorevski et al 2010).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations