S isotopic composition

The model traces the reaction path by taking a series of steps along reaction progress, moving forward each step from i to 2- Over a step, the system s isotopic composition can change in two ways reactants can be added or removed, and segregated minerals can dissolve. 

There are many sulfur components in meteorites which may occur in all possible valence states (—2 to +6). TroUite is the most abundant sulfur compound of iron meteorites and has a relatively constant S-isotope composition (recall... 

O, H, C, S, and N isotope compositions of mantle-derived rocks are substantially more variable than expected from the small fractionations at high temperatures. The most plausible process that may result in variable isotope ratios in the mantle is the input of subducted oceanic crust, and less frequent of continental crust, into some portions of the mantle. Because different parts of subducted slabs have different isotopic compositions, the released fluids may also differ in the O, H, C, and S isotope composition. In this context, the process of mantle metasomatism is of special significance. Metasomatic fluids rich in Fe +, Ti, K, TREE, P, and other large ion lithophile (LIE) elements tend to react with peridotite mantle and form secondary micas, amphiboles and other accessory minerals. The origin of metasomatic fluids is likely to be either (1) exsolved fluids from an ascending magma or (2) fluids or melts derived from subducted, hydrothermally altered crust and its overlying sediments. 

Fig. 3.34 S-isotope composition of (a) natural and (b) anthropogenic sulfur sources in the atmosphere, DMS Dimethyl-sulfide...

Fritz P, Basharmel GM, Drimmie RJ, Ibsen J, Qureshi RM (1989) Oxygen isotope exchange between sulphate and water during bacterial reduction of sulphate. Chem Geol 79 99-105 Fry B (1988) Food web structure on Georges Bank from stable C, N and S isotopic compositions. Limnol Oceanogr 3 1182-1190... 

Fry, B. (1988). Food web stmcmre on Georges Bank from stable C, N, and S isotopic compositions. Limnol. Oceanogr. 33, 1182—1190. 

Rudnick R. L., Eldridge C. S., and Bulanova G. P. (1993a) Diamond growth history from in situ measurement of Pb and S isotopic compositions of sulfide inclusions. Geology 21, 13-16. 

Except for elements with one or more radiogenic isotopes, the isotopic composition of an element in Nature can be considered constant for most applications of stable isotope techniques. However, they are not invariable (see also Chapter 1). Stable isotopes of an element differ slightly in mass, which may cause changes in the element s isotopic composition if a chemical or physical transfer process is sensitive to the isotopes masses and if the transfer is incomplete. For reasons of mass balance, the isotopic abundances cannot be changed if all matter is transferred from a source to a target compartment. 

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