δ30Si and δ29Si Determinations on USGS BHVO-1 and BHVO-2 Reference Materials with a New Configuration on a Nu Plasma Multi-Collector ICP-MS

We report silicon isotopic determinations for USGS rock reference materials BHVO-1 and BHVO-2 using a Nu Plasma multi-collector (MC)-ICP-MS, upgraded with a new adjustable entrance slit, to obtain medium resolution, as well as a stronger primary pump and newly designed sampler and skimmer cones ("B" cones). These settings, combined with the use of collector slits, allowed a resolution to be reached that was sufficient to overcome the (NO)-N-14-O-16 and N-14(2) interferences overlying the Si-30 and the Si-28 peaks, respectively, in an earlier set-up. This enabled accurate measurement of both delta Si-30 and delta Si-29. The delta value is expressed in per mil variation relative to the NBS 28…