Record of paleofluid circulation in faults revealed by hematite(U-Th)/He and apatite fission-track dating: An example from Gower Peninsula fault fissures, Wales

Alexis K. Ault, Max Frenzel, Peter W Reiners, Nigel H. Woodcock, Stuart N. Thomson

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Abstract

Fault rock low-temperature thermochronometry can inform the timing, temperature, and significance of hydrothermal fluid circulation in fault systems. We demonstrate this with combined hematite(U-Th)/He(He)dating, and sandstone apatite fission-track(AFT)and apatite and zircon(U-Th)/He(He)thermochronometry from fault-related fissures on the Gower Peninsula, Wales. Hematite He dates from 141 ± 5.1 Ma to 120 ± 5.0 Ma overlap with a 131 ± 20 Ma sandstone infill AFT date. Individual zircon He dates are 402-260 Ma, reflecting source material erosion, and imply a maximum Late Permian infill depositional age. Burial history reconstruction reveals modern exposures were not buried sufficiently in the Triassic-Early Cretaceous to have caused reheating to temperatures necessary to reset the AFT or hematite He systems, and thus these dates cannot reflect cooling due to erosion alone. Hot fluids circulating through fissures in the Early Cretaceous reset the AFT system. Hematite was either also reset by fluids or precipitated from these fluids. Similar hematite He dates from fault-related mineralization in south Glamorgan(Wales)and Cumbria(England)imply concomitant regional hot groundwater flow along faults. In this example, hydrothermal fluid circulation, coeval with North Atlantic rifting, occurred in higher-permeability fissures and fault veins long after they initially formed, directly influencing local and regional geothermal gradients.

Original languageEnglish (US)
Pages (from-to)379-385
Number of pages7
JournalLithosphere
Volume8
Issue number4
DOIs
StatePublished - 2016

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fission track dating
fissure
hematite
apatite
infill
hydrothermal fluid
fluid
zircon
sandstone
Cretaceous
erosion
geothermal gradient
rifting
groundwater flow
Permian
Triassic
temperature
permeability
mineralization
cooling

ASJC Scopus subject areas

  • Geology

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Record of paleofluid circulation in faults revealed by hematite(U-Th)/He and apatite fission-track dating : An example from Gower Peninsula fault fissures, Wales. / Ault, Alexis K.; Frenzel, Max; Reiners, Peter W; Woodcock, Nigel H.; Thomson, Stuart N.

In: Lithosphere, Vol. 8, No. 4, 2016, p. 379-385.

Research output: Contribution to journalArticle

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