Strontium, isotope composition

Strontium isotopes. Strontium isotopic compositions ( Sr/ Sr) of anhydrite, gypsum and barite from Kuroko deposits are summarized in Fig. 1.45 (Farrell et al., 1978 Honma and Shuto, 1979 Farrell and Holland, 1983 Yoneda et al., 1993 Yoneda and Shirahata, 1995). Sr/ Sr values of anhydrite and gypsum are slightly lower than that of seawater, suggesting that most of the strontium was derived from seawater, but a small amount of... 

Yoneda, T., Yin, S. and Shirahata, H. (1993) Strontium isotopic composition in barite from the Minamishiraoi Kuroko-type deposit. Southwestern Hokkaido, Japan. Resource Geology, 43, 427-434. 

Palmer MR, Edmond M (1992) Controls over the strontium isotope composition of river water. Geochim Cosmochim Acta 56 2099-2111... 

Strontium incorporated into the teeth, for example, becomes immobilized after formation of the teeth. The relative amounts of the isotopes of strontium in the teeth is, therefore, related to the average strontium isotope composition that an animal ingested in food or water while growing. Thus teeth retain a kind of record of both early exposure to the isotopes of strontium in the water and food ingested during their growing, early life. In the... 

Nicolussi GK, Pellin MJ, Lewis RS, Davis AM, Clayton RN, Amari S (1998b) Strontium isotopic composition in individual silicon carbide grains a record of s-process nucleosynthesis. Phys Rev Lett 81 3583-3586 Nicolussi GK, Pellin MJ, Lewis RS, Davis AM, Clayton RN, Amari S (1998c) Zirconium and molybdenum in individual circumstellar graphite grains new data on the nucleosynthesis of the heavy elements. Astrophys J 504 492-499... 

B. L. Ingram, P. K. Weber, Salmon origin in California s Sacramento-San Joaquin river system as determined by otolith strontium isotopic composition Geology, 27 (1999), 851-854. 

Figure 6 Volatile/refractory element ratio-ratio plots for chondrites and the silicate Earth. The correlations for carbonaceous chondrites can be used to define the composition of the Earth, the Rb/Sr ratio of which is well known, because the strontium isotopic composition of the BSE represents the time-integrated Rb/Sr. The BSE inventories of volatile siderophile elements carbon, sulfur, and lead are depleted by more than one order of magnitude because of core formation. The values for Theia are time-integrated compositions, assuming time-integrated Rb/Sr deduced from the strontium isotopic composition of the Moon (Figure 8) can be used to calculate other chemical compositions from the correlations in carbonaceous chondrites (Halliday and Porcelli, 2001). Other data are from Newsom (1995).

Figure 8 Initial strontium isotope composition of early lunar highland rocks relative to other early solar system objects. APB Angrite Parent Body CEPB Cumulate Eucrite Parent Body BSSI Bulk Solar System Initial (source Halliday and Porcelli, 2001).

Figure 52 Initial ENd ssr isotope plot of calculated whole-rock eclogites from Africa (Koidu—Hills and Haggerty, 1989 Orapa—Smith et al., 1989 Viljoen et al, 1996 Roberts Victor—Jagoutz et al, 1984 Smith et al., 1989 Jacob and Jagoutz, 1994 Bellsbank—Neal et al., 1990), Yakutia (Snyder et al, 1993 Jacob et al, 1994 Pearson et al., 1995a Snyder et al, 1997), and eclogitic inclusions in diamonds (Richardson, 1986 Richardson et al, 1990 1999 Smith et al, 1991). Eclogite data are initial calculated whole-rock neodymium isotope compositions. Strontium isotope compositions are from clinopyroxene only. Cratonic peridotite minerals and diamond inclusions are plotted for comparison. Arrow points to a sample from Udachnaya that has a calculated initial SNd of 484. dashed lines are...

A number of eclogites have both radiogenic neodymium isotopes and radiogenic strontium relative to bulk Earth. For these samples, some of the Sr/ Sr values exceed modem and Archean seawater compositions (see Chapter 6.17). Hence, in a subduction-type model, the radiogenic strontium isotopic composition of the eclogite protohth is not solely inherited from oceanic cmst but is likely to be a time-integrated response to Rb/Sr enrichment during hydrothermal alteration... 

Although Sr/ Sr isotopic evolution for the mantle is only poorly constrained at present, this system has tremendous potential for revealing details of cmst-formation processes through time as well as for providing precise timescales on Earth formation. The test of this awaits determination of accurate initial strontium isotopic compositions from Precambrian samples. The potential for acquisition of this type of data is high, as advances in techniques including both in situ measurements (e.g., Christiensen et al., 1996) and low-level solution work (e.g., Mueller et al., 2000) now allow precise determination of isotopic compositions from extremely small amounts (<10 g) of strontium. This ability makes feasible analyses of rare, relict high-strontium, low-mbidium phases which may be preserved within ancient rocks and minerals and may accurately record mantle compositions. 

The duration of chemical exchange between seawater and basalt can also be determined by isotopic studies of hydrothermal minerals. A variety of techniques have been used, ranging from direct dating by K/Ar and Rb/Sr isochron techniques to comparisons of the initial strontium isotopic composition of alteration minerals with the isotopic evolution of seawater (Gallahan and Duncan, 1994 Richardson et al., 1980). 

HodeU D. A., Mead G. A., and Mueller P. A. (1990) Variations in the strontium isotope composition of seawater (8 Ma to present) implications for chemical weathering rates and dissolved fluxes to the oceans. Chem. Geol. 80, 291-307. 

Sharp M., Creaser R. A., and Skidmore M. (2002) Strontium isotope composition of runoff from a glaciated carbonate terrain. Geochim. Cosmochim. Acta 66, 595-614. 

Chaudhuri S. (1978) Strontium isotopic composition of several oil field brines from Kansas and Colorado. Geochim. Cosmochim. Acta 42, 329—331. 

McNutt R. H., Frape S. K., and Fritz P. (1984) Strontium isotopic composition of some brines from the Precambrian shield of Canada. Isotope Geosci. 2, 205-215. 

The marine strontium isotope record is the proxy record most commonly used to constrain the geologic history of chemical weathering. However, in recent years it has been widely criticized as a proxy indicator of past silicate weathering rates. The osmium isotope record is analogous to the strontium record in many respects, and can help to constrain interpretations of the marine strontium isotope record. In this section the geochemical factors that influence the osmium and strontium isotope compositions of seawater are reviewed, and the structure of these two records of Cenozoic ocean chemistry is discussed. 

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