TY - JOUR
T1 - Time span of plutonism, fabric development, and cooling in a Neoproterozoic magmatic arc segment
T2 - U-Pb age constraints from syn-tectonic plutons, Sark, Channel Islands, UK
AU - Miller, Brent V.
AU - Samson, Scott D.
AU - D'Lemos, Richard S.
N1 - Funding Information:
We are indebted to I.R. Tribe for his detailed microstructural observations, which made this study possible. Feldspar Pb data were obtained by B.A. Fowler as part of her M.Sc. thesis at Syracuse University. Funding for this project was provided by National Science Foundation grant EAR-9614620 to S.D.S. and by Oxford Brookes University support to R.S.D. We thank Drew Coleman and Keith Klepeis for their careful reviews and suggestions to improve this paper.
PY - 1999/10/30
Y1 - 1999/10/30
N2 - New U-Pb zircon and titanite dates from syn-tectonic plutons on the British Channel Island of Sark constrain the time span of plutonism, fabric development, and cooling in this part of the Neoproterozoic Cadomian magmatic arc. The Tintageu leucogneiss is a mylonitic unit that was dated previously at 615.6-2.3+4.2 Ma. The Port du Moulin quartz diorite, which intruded the Tintageu unit, contains a high-strain solid-state deformation fabric that is less intense than, but parallel to, fabrics in the leucogneiss and yields a U-Pb zircon date of 613.5-1.5+2.3 Ma. The Little Sark quartz diorite also displays solid-state deformation fabrics in addition to relict magmatic textures, and yields a U-Pb zircon date of 611.4-1.3+2.1 Ma. The North Sark granodiorite is largely penetratively undeformed, exhibits mainly magmatic fabrics and textures and has a U-Pb zircon date of 608.7-1.0+1.1 Ma. Two fractions of titanite from each intrusion are essentially concordant and are identical within error, with mean dates of 606.5 ± 0.4 Ma (Port du Moulin quartz diorite), 606.2 ± 0.6 Ma (Little Sark quartz diorite), 606.4 ± 0.6 Ma (North Sark granodiorite). The new U-Pb data, in combination with previous U-Pb and 40Ar/39Ar data and previous field studies, confirm the syn-tectonic nature of the Sark plutons and quantify the time span (ca. 7 m.y.) required for intrusion and sufficient crystallization of each body to record incremental strain during waning deformation. Titanite U-Pb and hornblende 40Ar/39Ar dates mark final cooling about 2 m.y. after intrusion of the last pluton.
AB - New U-Pb zircon and titanite dates from syn-tectonic plutons on the British Channel Island of Sark constrain the time span of plutonism, fabric development, and cooling in this part of the Neoproterozoic Cadomian magmatic arc. The Tintageu leucogneiss is a mylonitic unit that was dated previously at 615.6-2.3+4.2 Ma. The Port du Moulin quartz diorite, which intruded the Tintageu unit, contains a high-strain solid-state deformation fabric that is less intense than, but parallel to, fabrics in the leucogneiss and yields a U-Pb zircon date of 613.5-1.5+2.3 Ma. The Little Sark quartz diorite also displays solid-state deformation fabrics in addition to relict magmatic textures, and yields a U-Pb zircon date of 611.4-1.3+2.1 Ma. The North Sark granodiorite is largely penetratively undeformed, exhibits mainly magmatic fabrics and textures and has a U-Pb zircon date of 608.7-1.0+1.1 Ma. Two fractions of titanite from each intrusion are essentially concordant and are identical within error, with mean dates of 606.5 ± 0.4 Ma (Port du Moulin quartz diorite), 606.2 ± 0.6 Ma (Little Sark quartz diorite), 606.4 ± 0.6 Ma (North Sark granodiorite). The new U-Pb data, in combination with previous U-Pb and 40Ar/39Ar data and previous field studies, confirm the syn-tectonic nature of the Sark plutons and quantify the time span (ca. 7 m.y.) required for intrusion and sufficient crystallization of each body to record incremental strain during waning deformation. Titanite U-Pb and hornblende 40Ar/39Ar dates mark final cooling about 2 m.y. after intrusion of the last pluton.
KW - Cadomian orogeny
KW - English Channel Islands
KW - Magmatic arc
KW - Syn-tectonic plutonism
KW - Titanite
KW - U-Pb
KW - Zircon
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U2 - 10.1016/S0040-1951(99)00172-9
DO - 10.1016/S0040-1951(99)00172-9
M3 - Article
AN - SCOPUS:0033386794
SN - 0040-1951
VL - 312
SP - 79
EP - 95
JO - Tectonophysics
JF - Tectonophysics
IS - 1
ER -