Abstract
The Ordovician peri-Laurentian Grangegeeth Terrane in eastern Ireland and the adjacent Katian to Wenlock Rathkenny Tract are together a relict of the closing Iapetus Ocean. The Rathkenny Tract succession is part of the Laurentian Southern Uplands–Down–Longford Terrane accretionary prism, but the contact between the Rathkenny and Grangegeeth terranes is cryptic. Two cores of Lower Paleozoic strata along a buried projection of the Rathkenny–Grangegeeth outcrops contain volcaniclastic units within a succession of mudstone and siltstone. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircons from volcanogenic horizons yielded a maximum depositional age of c. 450 Ma. Nearly 98% of the zircon ages are 480–445 Ma, indicating a proximal volcanic source. The trace element geochemistry of the Ordovician zircons indicates a host magma sourced from continental crust. A diverse ostracod fauna in the mudstones suggests a Katian age and includes species with Baltic, Laurentian and Avalonian affinities.We propose a paired subduction zone model for the emplacement of the Grangegeeth–Rathkenny succession, with the Rathkenny strata deposited on an oceanic plate between the Laurentian margin accretionary prism and the 480–450 Ma Grangegeeth peri-Laurentian microcontinental arc. Volcaniclastic detritus fed into the Rathkenny basin was then incorporated into the accretionary prism. The mixed fauna indicates that the Iapetus Ocean was narrow by Katian time.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 440-446 |
| Number of pages | 7 |
| Journal | Journal of the Geological Society |
| Volume | 176 |
| Issue number | 3 |
| DOIs | |
| State | Published - May 1 2019 |
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ASJC Scopus subject areas
- Geology
Cite this
Insight into late iapetus tectonics from new U–Pb zircon and micropalaeontological data from the Navan area, Eastern Ireland. / McConnell, B.; Riggs, Nancy R; Sevastopulo, G.
In: Journal of the Geological Society, Vol. 176, No. 3, 01.05.2019, p. 440-446.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Insight into late iapetus tectonics from new U–Pb zircon and micropalaeontological data from the Navan area, Eastern Ireland
AU - McConnell, B.
AU - Riggs, Nancy R
AU - Sevastopulo, G.
PY - 2019/5/1
Y1 - 2019/5/1
N2 - The Ordovician peri-Laurentian Grangegeeth Terrane in eastern Ireland and the adjacent Katian to Wenlock Rathkenny Tract are together a relict of the closing Iapetus Ocean. The Rathkenny Tract succession is part of the Laurentian Southern Uplands–Down–Longford Terrane accretionary prism, but the contact between the Rathkenny and Grangegeeth terranes is cryptic. Two cores of Lower Paleozoic strata along a buried projection of the Rathkenny–Grangegeeth outcrops contain volcaniclastic units within a succession of mudstone and siltstone. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircons from volcanogenic horizons yielded a maximum depositional age of c. 450 Ma. Nearly 98% of the zircon ages are 480–445 Ma, indicating a proximal volcanic source. The trace element geochemistry of the Ordovician zircons indicates a host magma sourced from continental crust. A diverse ostracod fauna in the mudstones suggests a Katian age and includes species with Baltic, Laurentian and Avalonian affinities.We propose a paired subduction zone model for the emplacement of the Grangegeeth–Rathkenny succession, with the Rathkenny strata deposited on an oceanic plate between the Laurentian margin accretionary prism and the 480–450 Ma Grangegeeth peri-Laurentian microcontinental arc. Volcaniclastic detritus fed into the Rathkenny basin was then incorporated into the accretionary prism. The mixed fauna indicates that the Iapetus Ocean was narrow by Katian time.
AB - The Ordovician peri-Laurentian Grangegeeth Terrane in eastern Ireland and the adjacent Katian to Wenlock Rathkenny Tract are together a relict of the closing Iapetus Ocean. The Rathkenny Tract succession is part of the Laurentian Southern Uplands–Down–Longford Terrane accretionary prism, but the contact between the Rathkenny and Grangegeeth terranes is cryptic. Two cores of Lower Paleozoic strata along a buried projection of the Rathkenny–Grangegeeth outcrops contain volcaniclastic units within a succession of mudstone and siltstone. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircons from volcanogenic horizons yielded a maximum depositional age of c. 450 Ma. Nearly 98% of the zircon ages are 480–445 Ma, indicating a proximal volcanic source. The trace element geochemistry of the Ordovician zircons indicates a host magma sourced from continental crust. A diverse ostracod fauna in the mudstones suggests a Katian age and includes species with Baltic, Laurentian and Avalonian affinities.We propose a paired subduction zone model for the emplacement of the Grangegeeth–Rathkenny succession, with the Rathkenny strata deposited on an oceanic plate between the Laurentian margin accretionary prism and the 480–450 Ma Grangegeeth peri-Laurentian microcontinental arc. Volcaniclastic detritus fed into the Rathkenny basin was then incorporated into the accretionary prism. The mixed fauna indicates that the Iapetus Ocean was narrow by Katian time.
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U2 - 10.1144/jgs2018-168
DO - 10.1144/jgs2018-168
M3 - Article
AN - SCOPUS:85065133249
VL - 176
SP - 440
EP - 446
JO - Journal of the Geological Society
JF - Journal of the Geological Society
SN - 0016-7649
IS - 3
ER -