Data to: Molybdenum and titanium isotopic signatures of arc-derived cumulates
Description
We investigated Mo and Ti isotopic signatures of upper crustal magmatic cumulates comprising hornblendites and gabbros from the Alpine orogen, the Sierra Nevada batholith, the Sanandaj-Sirjan zone and the Kos volcano-plutonic system. Along with the isotope data, also bulk rock major and trace elements as well as in-situ microprobe data of individual minerals were measured. The cumulates and mafic enclaves exhibit Ti isotopic compositions ranging from that of arc-basalts/andesites to significantly lighter values (δ49Ti between −0.15 and + 0.08‰), which is in agreement with a Rayleigh distillation model. The δ49Ti correlates negatively with the abundance of Fe-Ti oxides, suggesting that in samples which have δ49Ti signatures similar to those of arc-basalts, most of the Ti is hosted in pyroxene and amphibole. This indicates that the degree to which Ti isotopes are fractionated in a melt is controlled by the fraction of Ti incorporated into silicate phases versus that incorporated into Fe-Ti oxides. In contrast, the corresponding Mo isotopic compositions of the upper crustal magmatic cumulates and mafic enclaves are more dispersed (δ98MoNIST = −0.02 ± 0.22‰, 2 s.d.) and similar to average arc-basalts. However, Mo concentrations throughout several cumulate and mafic enclave bulk rocks measured are too enriched to be explained by pure fractional crystallization as they do not match modelled melt-cumulate fractionation trends. We distinguish between purely magmatic and predominantly fluid mediated processes leading to Mo enrichment in cumulates, and show that both can play an important role in the generation of high Mo cumulates. Further information can be found in the open access publication, which should be cited when using the data: Storck, J. C., Greber, N. D., Duarte, J. F. V., Lanari, P., Tiepolo, M., & Pettke, T. (2023). Molybdenum and titanium isotopic signatures of arc-derived cumulates. Chemical Geology, 617, 121260.
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Analytical techniques to the dataset can be found in the open access publication: Storck, J. C., Greber, N. D., Duarte, J. F. V., Lanari, P., Tiepolo, M., & Pettke, T. (2023). Molybdenum and titanium isotopic signatures of arc-derived cumulates. Chemical Geology, 617, 121260.
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Swiss National Science Foundation
181172