Dating sedimentary rocks using in situ U-Pb geochronology of syneruptive zircon in ash-fall tuffs <1 mm thick
- Rasmussen, Birger
- Fletcher, Ian
DOIAbstract
Absolute ages for sedimentary rocks are required to construct a temporal framework in which to decipher Earth's history. The most reliable method for dating Precambrian sedimentary rocks is U-Pb geochronology of zircon in intercalated volcanic rocks. However, extracting sufficient zircons involves destructive mineral separation procedures, often requiring several kilograms of sample. We have dated felsic tuffs <1 mm thick using single polished thin sections from diamond drill core of Neoarchean shale from the Pilbara craton, Australia. The tuffs contain abundant euhedral zircon crystals, commonly 10–30 μm long. In situ SHRIMP (sensitive high-resolution ion microprobe) geochronology of the zircon in 8 tuffs gives 207Pb/206Pb dates between ca...
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