Water isotopic composition

Although formation waters show a wide range in isotopic composition, waters within a sedimentary basin are usually isotopically distinct. As is the case with surface meteoric waters, there is a general decrease in isotopic composition from low to high latitude settings (Fig. 3.20). Displacements of 5D and 8 0-values from the Meteoric Water Line (MWL) are very often correlated with salinity the most depleted waters in D and O are usually the least saline, fluids most distant from the MWL tend to be the most saline. 

Eig. 4. The bulk oxygen isotopic composition of different meteorite classes where (—) is the terrestial fractionation line. The 5 notation refers to the normalized difference between or ratios to those in standard mean ocean water (SMOW) in relative units of parts per thousand. The... 

The recognition in 1940 that deuterium as heavy water [7789-20-0] has nuclear properties that make it a highly desirable moderator and coolant for nuclear reactors (qv) (8,9) fueled by uranium (qv) of natural isotopic composition stimulated the development of industrial processes for the manufacture of heavy water. Between 1940 and 1945 four heavy water production plants were operated by the United States Government, one in Canada at Trail,... 

After cooling, the reaction mixture is diluted with ether, the organic phase washed with ice-cold water and dried over anhydrous sodium sulfate. Evaporation of the solvent and crystallization of the residue from ether-hexane gives 6,6,8j5-d3-5a-androstan-3j5-ol-7-one (11) in 84% yield mp 141-142,5° isotopic composition 6% d2,93% da and 1 %... 

D2O and the tritium analogue T2O (p. 41). The high bp is notable (cf. H2S, etc.) as is the temperature of maximum density and its marked dependence on the isotopic composition of water. The high dielectric constant and measurable ionic dissociation equilibrium are also unusual and important properties. The ionic mobilities of [H30] and [OH] in water are abnormally high (350 X 10 " and 192 x 10 cms per V cm... 

Evaporitic sulfur has a range of sulfur isotopic composition from +10%o to +30%o, while sedimentary sulfur is depleted in the heavy isotope and has a range of isotopic composition of about —40%o to +10%o. Most of this variation reflects systematic changes with geological age. The source fractions of a river water can be estimated from an isotopic mass balance ... 

The global atmospheric circulation acts as an enormous filtration system, which depletes high-latitude precipitation of heavy isotope-bearing water molecules. Because of this system, measurements of the stable isotopic composition of the ice sheets and of ocean-floor sediments reveal very important paleo-environmental information (see Sections 18.2.2,18.3.2, and 18.3.3). Here we examine this filtration system at a physical level. This system was first understood by a great Danish geochemist named Willi Dansgaard (Dansgaard, 1964). 

Suggestions that phosphatic minerals in mammals could be used, however, revived the interest in climate reconstruction in continental interiors. Aquatic, cold-blooded animals like fish have body temperatures and body water oxygen isotopic compositions that are directly dependent on the water in which they live. For these animals, a commonly used equation describes the relationships among temperature, water oxygen isotopic composition and phosphate oxygen isotopic composition as (Longinelli and Nuti 1973 verified by Kolodny et al. 1983, among others) ... 

Body water oxygen isotopic composition in mammals is a function of the oxygen mass balance of the specific animal. In general, it can be related to three major oxygen sources air oxygen, drinking water, and food (both the... 

Figure 6.4. Percent average humidity compared with 6 0 in bone phosphate. The strong association between the two variables across the species of Australian marsupials (data from Ayliffe and Chivas 1990) and North American white-tailed deer (data from Luz ei a/. 1990) indicates that their body water oxygen isotopic composition is strongly determined by the 8"0 in their diet since plant 8 0 varies in negative correlation with humidity.

This equation predicts a value of 26.8%ofor the zebra at Turkana assuming an average value of 6%o for Lake Turkana water. This predicted value is l%o less than the actual value of 27.8%o. Given the variation in methods of sample preparation and analysis, variation between bone and tooth enamel (Stuart-Williams and Schwarcz 1997), and uncertainty in surface water oxygen isotopic composition, these values are extraordinarily close. Alternatively, if the equation is solved for using the actual value of the Turkana zebra. 

Eleven controlled diet and environment experiments have been designed in a way that can be used to investigate the effects of protein nutrition and heat and/or water stress on diet-tissue A N. Laboratory rats were raised on purified, pelletized diets in which the isotopic composition of proteins, lipids and carbohydrates were well characterized and their proportions accurately and precisely measured (Ambrose and Norr 1993). Four experiments involved manipulation of temperature and/or water availability. Of these four experiments, one used a diet with high (70%) protein concentrations and heat/water stress (36°C) and three used normal (20%) protein concentrations. Seven experiments were conducted at normal temperature (21°C) with water ad libitum. Of these seven experiments, two used diets formulated with veiy low protein (5%), three with normal protein and two with high protein concentrations. 

Farquhar, G.D. Richards, R.A. (1984). Isotopic composition of plant carbon correlates with water-use efficiency of wheat genotypes. Australian Journal of Plant Physiology, 11, 539-52. 

Martin, B.J. Thorstenson, Y.R. (1988). Stable carbon isotope composition (6 C), water use efficiency and biomass productivity of Lycopersicon esculen-tum, Lycopersicon pennellii and the Fi hybrid. Plant Physiology 88, 218-23. 

The most important conclusion derived from the isotopic studies mentioned above is that isotopic characteristics of Kuroko ore fluids were caused dominantly by seawater-volcanic rock interaction at elevated temperature and by the mixing of seawater with small portions of igneous water or the hydrothermal solution whose chemical and isotopic compositions are controlled by water-rock interaction under the rock-dominated condition and also small proportion of mixing of meteoric water. 

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