On the viability of detrital biotite Rb-Sr geochronology

Re-examination of International Ocean Discovery Program (IODP) sediment samples collected from the Bay of Bengal via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) Rb-Sr geochronology demonstrates the viability of the biotite Rb-Sr system for use as a detrital chronometer. The age population defined by the Rb-Sr dates essentially reproduces that previously published for detrital Ar-40/Ar-39 dates. The effect of unknown/assumed initial Sr-87/Sr-86 on the calculated population can be ameliorated by filtering for higher Rb-87/Sr-86 ratios. Such filtering, however, could introduce bias toward more radiogenic populations, especially in younger material that has not had time to accumulate radiogenic product (e.g. limiting the effect of initial Sr-87/Sr-86 to similar to <5 % requires filtering of Rb-87/Sr-86 >500 at 250 Ma and Rb-87/Sr-86 >50 at 2500 Ma). Finally, Ti-in-biotite temperatures calculated based on element concentration data collected during LA-ICP-MS overlap with those calculated for the same material based on electron probe microanalyzer data, demonstrating the potential for in situ biotite petrochronology based on the Rb-Sr system.