Constraining recycled detritus in quartz‐rich sandstones: Insights from a multi‐proxy provenance study of the Mid‐Carboniferous, Clare Basin, western Ireland

Autor: Martin Nauton-Fourteu, Shane Tyrrell, David Chew, Andrew C. Morton, Gary O'Sullivan, Chris Mark
Rok vydání: 2020
Předmět:
Zdroj: Basin Research. 33:342-363
ISSN: 1365-2117
0950-091X
DOI: 10.1111/bre.12469
Popis: [Abstract Quartz‐rich sandstones can be produced through multiple sedimentary processes, potentially acting in combination, such as extensive sedimentary recycling or intense chemical weathering. Determining the provenance of such sedimentary rocks can be challenging due to low amounts of accessory minerals, the fact that the primary mineralogy may have been altered during transport, storage or burial and difficulties in the recognition of polycyclic components. This study uses zircon and apatite U‐Pb geochronology, apatite trace elements, zircon‐tourmaline‐rutile indices and petrographic observations to investigate the sedimentary history of mineralogically mature mid‐Carboniferous sandstones of the Tullig Cyclothem, Clare Basin, western Ireland. The provenance data show that the sandstones have been dominantly and ultimately sourced from three basement terranes: older Laurentian‐ associated rocks (ca. 900–2500 Ma) which lay to the north of the basin, peri‐Gondwanan terranes (ca. 500–700 Ma) to the south and igneous intrusive rocks associated with the Caledonian Orogenic Cycle (ca. 380–500 Ma). However, the multi‐proxy approach also helps constrain the sedimentary history and suggests that not all grain populations were derived directly from their original source. Grains with a Laurentian or a Caledonian affinity have likely been recycled through Devonian basins to the south. Grains with a peri‐Gondwanan affinity appear to be first cycle and are potentially derived from south/southwest of the basin. Taken as a whole, these data are consistent with input into the basin from the south and southwest, with the reworking of older sedimentary rocks, rather than intensive first‐cycle chemical weathering, likely explaining the compositional maturity of the sandstones. This study highlights the need for a multi‐proxy provenance approach to constrain sedimentary recycling, particularly in compositionally mature sandstones, as the use of zircon geochronology alone would have led to erroneous provenance interpretations. Zircon, together with U‐Pb geochronology from more labile phases such as apatite, can help distinguish first‐cycle versus polycyclic detritus., This multi‐proxy provenance approach identifies partly recycled sandstones in the mid‐Carboniferous Tullig Cyclothem of the Clare Basin. Taken as a whole, these data are consistent with input into the basin from the south and southwest, with first cycle peri‐Gondwanan grains and recycling of Caledonian and Laurentian grains through Devonian basins to the south. ]
Databáze: OpenAIRE
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