The distribution of lead and thallium in mantle rocks: Insights from the Balmuccia peridotite massif (Italian Alps)

Copper Isotope Variations During Magmatic Migration in the Mantle: Insights From Mantle Pyroxenites in Balmuccia Peridotite Massif

“…Any weathered surfaces were removed prior to processing of the rocks to powder. Petrographic observations confirm the negligible low-temperature alteration of pentlandite and chalcopyrite in these samples (Figure 2), consistent with the low values of loss on ignition (LOI) of 0.35−1.57% ; see more fresh sulfides in previous studies Wang and Becker (2015b) and Wang et al (Wang, Lazarov et al, 2018)). Therefore, the measured δ 65 Cu values of bulk rocks of BM pyroxenites likely represent integrated primary compositions of pentlandite and chalcopyrite.…”

“…Pentlandite and chalcopyrite are the main sulfide phases in the BM pyroxenites with minor pyrrhotite (Figure 2d). Previous in situ analyses on these different sulfide phases of the BM pyroxenites (Wang, Lazarov, et al, 2018) have indicated that >98 wt % of bulk-rock Cu is hosted in chalcopyrite (>22.6 wt %) and only a small fraction in other sulfide phases (several hundred μg/g; Table 2 and Figure 6 ). These sulfide assemblages exsolved from cooling sulfide melts, which led to redistribution of Cu between different sulfide minerals and preferential enrichment of Cu in chalcopyrites (Edmonds & Mather, 2017;Patten et al, 2012;Patten et al, 2013;van Acken et al, 2010;Wang & Becker, 2015b).…”

“…Sulfides in the pyroxenites precipitated with pyroxenes ± spinel from sulfide saturated magmas. The sulfide grains, typically 50−500 μm in size, are mostly aggregates of pentlandite, chalcopyrite, and pyrrhotite ( Figure 2d; Wang, Lazarov, et al, 2018, Figures S1e-S1g in the supporting information). These sulfide assemblages should be the cooling-induced exsolution products of high-temperature sulfide melts saturated from basic magmas (e.g., Edmonds & Mather, 2017;Lorand et al, 2010;Patten et al, 2012).…”

“…The bulk rock S and Cu contents have been reported before (Wang & Becker, 2015b;). a The data are taken from Wang et al (Wang, Lazarov, et al, 2018). The sulfide fractions were calculated from bulk rock S contents.…”

“…The BM pyroxenites are depleted in light REE relative to heavy REE (Figure 8; Mukasa & Shervais, 1999;Wang, Lazarov et al, 2018), and initial Sr-Nd isotope compositions (( 87 Sr/ 86 Sr) i and ( 143 Nd/ 144 Nd) i ) of clinopyroxene separates from Balmuccia pyroxenites are 0.70270−0.70345 and 0.51255−0.51276, respectively (Mukasa & Shervais, 1999). These data suggest that the parental magmas of BM websterites and clinopyroxenites were MORB-like magmas sourced in the depleted mantle (Mukasa & Shervais, 1999;Wang, Lazarov, et al, 2018). Thus, their ΔFMQ should be comparable with the MORB source (Cottrell & Kelley, 2011).…”