Constraining the geothermal parameters of in situ Rb–Sr dating on Proterozoic shales and their subsequent applications

Abstract. Recent developments in tandem laser ablation mass spectrometer technology have demonstrated the capacity for separating parent and daughter isotopes of same online. As a result, beta-decay chronometers can now be applied to geological archive situ as opposed through traditional whole-rock digestions. One novel application this technique is Rb–Sr dating Proterozoic shales that are dominated by authigenic clays such illite. This method provide depositional window differentiating signatures early diagenetic processes versus late-stage secondary alteration. However, hydrothermal sensitivity isotopic system across timescales shale-hosted clay minerals not well understood. such, we dated Mesoproterozoic Velkerri Formation from Altree 2 Beetaloo Sub-basin (greater McArthur Basin), northern Australia, using approach. We then constrained thermal history these units common hydrocarbon maturity indicators modelled effects contact heating due intrusion Derim Dolerite. In mature, oil-prone zone yielded ages 1448 ± 81, 1434 19, 1421 139 Ma. These results agree with previous Re–Os unit interpreted recording timing an event soon after deposition. Conversely, overmature, gas-prone anchizone sourced deeper within borehole were at 1322 93 1336 40 younger than expected Formation. Instead, they consistent age Dolerite mafic intersected 800 m below Thermal modelling suggests single 75 thickness would been capable producing significant perturbation radiating sill top. The width proposed model similar thicknesses found elsewhere Basin. extent aureole induced coincides which kerogen becomes overmature. here caused enter gas window, fluids mobilize trace elements, reset chronometer. Consequently, propose chronometer may sensitive temperatures ca. 120 ?C reactions but withstand more 190 systems fluids. Importantly, study demonstrates framework combined use maturation help reveal thermochronological sedimentary basins. approach powerful tool identifying potential source rocks settings.