Elemental and isotopic behaviour of Zn in Deccan basalt weathering profiles: Chemical weathering from bedrock to laterite and links to Zn deficiency in tropical soils

Cu and Zn isotope fractionation during extreme chemical weathering

“…The SQ laterite dataset is shown as a full profile and as an integrated signature (larger symbol). Recently published full profile Zn isotope data is also included for the Bidar laterite, developed on Deccan basalt, for comparison (Zn only: Suhr et al, 2018). Literature data:…”

“…For example, Viers et al (2007) observed isotopically light Zn in laterite samples from Cameroon, which they attributed to 'ferrugination', a term which implies preferential incorporation or sorption of light isotopes in or on precipitating Fe oxide phases. Suhr et al (2018) suggested a similar process to explain isotopically light Zn in the residue of a basaltic laterite from Bidar, India. We observe negative correlations of δ 66 Zn and δ 65 Cu with Fe 2 O 3 ( Fig.…”

“…A study of the dissolved phase in rivers found a discharge-weighted Zn isotope composition unfractionated from continental rocks (Little et al, 2014b). The absence of systematic Zn isotope fractionation in rivers implies little or no Zn isotope fractionation during weathering, a hypothesis partially supported by studies of Zn isotopes in soils (Bigalke et al, 2010a;Vance et al, 2016;Opfergelt et al, 2017;Suhr et al, 2018). However, studies carried out in extreme, (sub-) tropical weathering regimes have observed preferential release of heavy Zn isotopes (Viers et al, 2007;Lv et al, 2016;Guinoiseau et al, 2017;Suhr et al, 2018).…”

“…However, studies carried out in extreme, (sub-) tropical weathering regimes have observed preferential release of heavy Zn isotopes (Viers et al, 2007;Lv et al, 2016;Guinoiseau et al, 2017;Suhr et al, 2018). This observation has been explained by various processes, including release of isotopically heavy Zn during oxidative weathering of sulphides (Fernandez and Borrok, 2009;Lv et al, 2016); organic complexation of the heavy isotope in the dissolved pool (Guinoiseau et al, 2017); incorporation or adsorption of isotopically light Zn in/on clays (Viers et al, 2007;Guinoiseau et al, 2017) or Fe oxides (Viers et al, 2007;Suhr et al, 2018); or release of isotopically light Zn from refractory mineral phases and subsequent reprecipitation with Fe oxide phases (Suhr et al, 2018).…”

“…To date, two studies have reported Zn isotope data from lateritic weathering profiles, one developed on granodiorite in Cameroon (Viers et al, 2007) and the other for the Bidar laterite developed on Deccan basalt in central India (Suhr et al, 2018). Both studies observe preferential retention of light Zn isotopes in the laterite residues.…”