A new orthopyroxene reference material (BL-1) for in situ microanalysis†

Abstract

Orthopyroxene is a significant mineral in both the Earth and the Moon, with its trace element composition playing a critical role in investigations of mantle conditions and magmatic evolution. Microanalysis of trace elements relies on reference materials to evaluate systematic errors and ensure data quality. This study introduces a new orthopyroxene reference material (BL-1), an aluminous enstatite, derived from peridotite xenoliths hosted by the Bailin basalt in southeastern China. The major and trace element concentrations of 16 elements (Si, Al, Fe, Mg, Ca, Na, Sc, Ti, V, Cr, Mn, Co, Ni, Zn, Ga, and Y) have been confirmed to be homogeneous at the micrometer to millimeter scale through X-ray intensity mapping, EPMA, and LA-ICP-MS in situ quantification. Bulk analyses conducted via WD-XRF, ICP-OES and solution-based ICP-MS demonstrate excellent agreement with in situ microanalyses performed using EPMA and LA-ICP-MS. Seven trace elements (Ca, Na, Ti, V, Cr, Mn, and Ni) exhibit concentrations exceeding 100 ppm, making BL-1 suitable as a reference material for routine trace element analyses using EPMA. Therefore, BL-1 orthopyroxene serves as an excellent complementary reference material for elemental in situ microanalysis. Although Ti, Zn, and Y exhibit notable deviations, the NIST SRM 612 and the USGS glasses demonstrate small fractionations for other elements and are effective for calibrating BL-1 orthopyroxene in LA-ICP-MS. EMPA analyses of BL-1 using different primary standards reveal negligible differences.