Martin, Ellinor; Schmitz, Birger; Alvarez, Walter; Aguirre-Palafox, Luis; Terfelt, Fredrik (2020): Chemistry of sediment-dispersed chrome spinel grains from the Early Cretaceous (Albian/Aptian) Calera Limestone, Pacifica Quarry, California [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.920972

Chemistry of chrome spinel grains extracted from samples of the Calera Limestone, Pacifica Quarry, California (37°36'49"N and 122°29'45"W). Chrome spinel grains mounted in pucks 271 to 300 were analyzed with a JEOL "Hyperprobe" JXA 8530-F field-emission electron microprobe (FE-EPMA) at the Vienna Natural History Museum; An accelerating voltage of 15 kV, a 1 μm beam diameter with a beam current of 20 nA, and a counting time of 10 s, giving ~250.000 counts, and 5 s for background were used for all element Kα lines.

Chrome spinel grains mounted in pucks 434, 435, and 442 were analyzed at Lund University using an Oxford Inca X181-sight energy-dispersive spectrometer with a Si detector mounted on a Hitachi S-3400 scanning electron microscope was used for chemical analysis. Cobalt was used as standard to monitor drift of the instrument. An acceleration voltage of 15 kV, a sample current of ~1 nA, and a counting live-time of 80 s were used. Analytical accuracy was controlled by analyses of the USNM 117075 (Smithsonian) chromite reference standard (Jarosewich et al., 1980).

Chemical data presented as oxide weight percentages.