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The characterisation of relative copper isotope amount ratios (d 65 Cu) helps constrain a variety of geochemical processes occurring in the geosphere, biosphere and hydrosphere. The accurate and precise determination of d 65 Cu in matrix reference materials is crucial in the effort to validate measurement methods. With the goal of expanding the number and variety of available geological and biological materials, we have characterised the d 65 Cu values of ten reference materials by MC-ICP-MS using C-SSBIN model for mass bias correction. SGR-1b (Green River shale), DOLT-5 (dogfish liver), DORM-4 (fish protein), TORT-3 (lobster hepatopancreas), MESS-4 (marine sediment) and PACS-3 (marine sediment) have for the first time been characterised for d 65 Cu. Additionally, four reference materials (with published d 65 Cu values) have been characterised: BHVO-1 (Hawaiian basalt), BIR-1 (Icelandic basalt), W-2a (diabase) and Seronorm TM Trace Elements Serum L-1 (human serum). The reference materials measured in this study possess complex and varied matrices with copper mass fractions ranging from 1.2 µg g -1 to 497 µg g -1 and d 65 Cu values ranging from -0.20‰ to 0.52‰ with a mean expanded uncertainty of ± 0.07‰ (U, k = 2), covering much of the natural copper isotope variability observed in the environment.

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Subduction of intraplate seamounts beneath a geochemically depleted mantle wedge provides a seldom opportunity to trace element recycling and mantle flow in subduction zones.

Chromite occurrences in ophiolite complexes present valuable natural resources and require sophisticated geophysical exploration methods. As chromite does not exhibit significant geophysical anomalies, we propose an indirect method of detection by surveying for magnetic anomalies caused by the serpentinization of the chromite host rock, which contains magnetite developed through petrogenesis. An unmanned airborne vehicle (UAV) magnetometry test survey revealed a known chromite deposit. The results show that mapping for serpentinite is a viable option to find chromite provided the survey is conducted at low flight elevations (<60m above ground). The survey results reveal the location of a known chromite deposit and indicate that the magnetic susceptibility contrast between chromite and the surrounding serpentinite is low. It further indicates a low-grade serpentinization in the area, which requires very sensitive magnetometry surveys in close proximity to the targets provided by terrestrial and UAV platforms. The ability of UAV surveys to acquire observations of the magnetic field in 3-D enables the calculation of magnetic gradients, which show higher sensitivity compared to classical gradient estimation from 2-D observations.