Ship-board determination of whole-rock (ultra-)trace element concentrations by laser ablation-inductively coupled plasma mass spectrometry analysis of pressed powder pellets aboard the D/V <i>Chikyu</i>

Abstract. The Oman Drilling Project (OmanDP), performed under the International Continental Scientific Program (ICDP), is an international scientific research project that undertook drilling at a range of sites in Semail ophiolite (Oman) to collect core samples spanning stratigraphy ophiolite, from upper oceanic crust down basal thrust. cores were logged Ocean Discovery (IODP) standards aboard D/V Chikyu. During ChikyuOman2018 Leg 3 (July–August 2018), participants described crust–mantle transition (CM) sites. main rock types recovered these gabbros, dunites and harzburgites, rocks typically forming base shallow mantle beneath present-day spreading centres. In addition description, selected analysed by X-ray fluorescence spectrometry (XRF) for their chemical compositions, including major, minor some trace elements. To complement standard procedures, we developed new approaches measure ultra-trace element concentrations using procedure adapted previous works prepare fine-grained pressed powder pellets coupled with laser ablation-inductively plasma mass (LA-ICP-MS) analysis instrumentation First, three (ultra)mafic reference materials investigated test validate our (BHVO-2, BIR-1a JP-1), then was applied selection gabbro dunite CM explore limitations method its current stage development. obtained results are good agreement preferred values subsequent solution replicate analyses same shore-based laboratories following samples. We describe this determination 37 (ultra-)trace elements (transition Ga, Li Large-Ion Lithophile Elements (LILE), Rare Earth (REE), High-Field-Strength (HFSE), U, Th, Pb) mafic ultramafic rocks. presented has major advantage it allows sea “dry”, safe way, without acid reagents. Our approach could be extended other interest and/or improved during future ocean operations Chikyu platforms.