Oxygen isotope data

Should any scepticism remain concerning the role of human activity in altering the concentration of greenhouse gases in the atmosphere two 

As Williams (2002) has discussed, a considerable proportion of the Earth s interglacial forests have already been removed through human action, a process that continues apace today especially in tropical and 

Organisms, unless consumed by other organisms, decay after death. Decay involves chemical alteration of body tissues and the actions of 

However, it was Carolus Liimaeus (Carl von Liime, 1707-1778), a Swedish naturalist, who established the system of taxonomy which is the basis for the modem classification of organisms (see Frangsmyr, 1983, for a review). This was published in 1735 in a book entitled Systems Naturae. The Lirmaean taxonomic system retains Aristotle s subdivision into plants (Plantae) and animals (Animalia) which are the broadest categories possible and are known as kingdoms. Fmther subdivisions are given in Figme 3.1 which shows fom further levels in this hierarchical or taxonomic system. 

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Two alternate methods have recently been developed and both are used in the present study. A laser probe analytical method provided the majority of the oxygen isotope data (see Kohn et al. 1996 for details on testing and developing the method). Laser probes were originally developed for the stable isotope analysis of silicates, oxides, and sulfides in ciystalline rocks (Crowe... 

Wolery (1978) and Reed (1982, 1983) have indicated based on a computer calculation of the change in chemistry of aqueous solution and mineralogy during seawater-rock interactions that epidote is formed under the low water/rock ratio less than ca. 50 by mass. Humphris and Thompson (1978), Stakes and O Nell (1982) and Mottl (1983) have also suggested on the basis of their chemical and oxygen isotopic data of the altered ridge basalts that epidote is formed by seawater-basalt interaction at elevated temperatures (ca. 200-350°C) under the rock-dominated conditions. If epidote can be formed preferentially under such low water/rock ratio, the composition of epidote should be influenced by compositions of the original fresh rocks. 

Preliminary oxygen isotope data from bulk rocks in a drill core that crosses the main zone (Fig. 3) show that the rocks surrounding the main ore zone at the Lac Cinquante deposit are elevated above normal magmatic values. This has been interpreted to preserve the signature of elevated fluid flow surrounding the ore zone. The trend is characterized by a... 

Oxygen isotope data (Table VII) support conclusions drawn from the chemical data (Tables IV and VI) that clay in the high pH, WD experiments underwent significant chemical reaction, whereas clay... 

Table VII. Oxygen Isotope Data for Various Smectites...

Figure 14. Comparison of A Mg (DSM3) and (SMOW) values for various chondrules and whole-rock chondrite samples. The sources of the oxygen isotope data are given in Table 3. Aqueous alteration on this diagram will move points approximately horizontally on this diagram.

Norton D, Taylor HP (1979) Quantitative simulation of the hydrothermal systems of crystaUizing magmas on the basis of transport theory and oxygen isotope data an analysis of the Skaergaard intrusion. J Petrol 20 421 86... 

Climate changes from the time ofthe disappearance of dinosaurs to our days have also been based up on deep-sea stable isotope data oxygen isotope data provide an insight into the temperature variations, while carbon isotope data are informative on the kind of global carbon cycle perturbation (Zachos 2001). These data suggest that the present conditions of temperature are similar to the late Middle Age. However, the trend toward higher temperatures is now more difficult to contrast because of the drastic deforestation and emission of gases. 

The CLAMP approach (to predict enthalpy and hence paleoelevation) has been independently verified against oxygen isotope data for Tibet, strengthening the argument that foliar physiognomy is not prone to systematic calibration changes over time due either to evolution or variations in C02 concentrations (Spicer et al. 2003 Currie et al. 2005 RA Spicer, written comm, in review 2007). 

Sr, Nd and Pb isotopic ratios of mafic rocks (Fig. 1.7) show large and continuous variations. However, various regions exhibit rather restricted and distinct isotopic signatures (Conticelli et al. 2002 and references therein). Oxygen isotopic data are also variable in the volcanic rocks from central-southern Italy. Data on whole rocks have brought to the conclusion... 

Oxygen isotopic data on whole rocks show 5180 in the range + 5.0 to +5.9 (Marty et al. 1994). Boron isotopic compositions have small but significant variations (8nB -8%o to -3%o), probably derived from both deep (i.e. source contamination) and shallow (i.e. magma contamination) processes (Tonarini et al. 2001b). 

Radiometric evidence for glacial and interglacial events generally corroborate the racemization dates in Table V. Oxygen isotope data (53) suggest a low ice volume (i.e., sea level maximum) at 100,000 years as well as at 120,000 years. Locality 14 may represent the 100,000-year event. Localities 1 and 130 yielded racemization dates of 180,000-... 

For volatile-rich carbonaceous chondrites like Cl and CM chondrites, constraints on thermal histories are derived from carbonate ages and oxygen isotopic data. The former indicate that alteration began soon after CAI formation and lasted —20Myr (Endress et al, 1996 Brearley et al, 2001). Oxygen-isotopic compositions of carbonates provide model-dependent temperatures... 

Most of the matrix data that we review are chemical and mineralogical as there is little isotopic information about individual matrix grains. Bulk oxygen isotopic compositions for matrix samples commonly differ from those of associated chondrules (e.g., Scott et al, 1988), but lack of oxygen-isotope data for samples of key chondrites and specific matrix components severely limits inferences about matrix origins. 

Oxygen-isotopic data for Cl chondrites provide some constraints on the location of alteration. The bulk compositions of Cl chondrites lie close to the terrestrial fractionation line on a three-isotope plot, with a of 4-0.38 0.09%o... 

Oxygen-isotopic data for bulk CM chondrites and mineral separates (Clayton and Mayeda, 1999) lie along a mixing line with slope 0.7, rather than the slope 0.5 carbonaceous chondrite anhydrous mineral (CCAM) (see line Chapter 1.06). This line is attributable to the mixing of anhydrous 0-rich silicate material in chondrules and CAIs, etc. and hydrated 0-poor material, largely phyllosilicates that occurs in the matrix. The bulk of CM chondrites is weakly... 

Oxygen isotopic compositions. The oxygen-isotopic data indicates that there are systematic relationships between the bulk isotopic composition of CM chondrites and the degree of aqueous alteration (Browning et al, 1996). In addition, the compositions of individual phases (carbonates and sulfates) also evolve with... 

Two parent body models have been proposed to explain the oxygen isotopic composition of carbonates in CM chondrites (i) a closed system, two reservoir model (Clayton and Mayeda, 1984, 1999) and (ii) a fluid-flow model (Young et al., 1999 Young, 2001 Cohen and Coker, 2000). Current oxygen-isotopic data are generally most consistent with the closed-system model, but can also be reconciled with the fluid-flow model if the CM chondrites sample a restricted region of the CM asteroid (Benedix et al., 2003), just downstream of the model alteration front proposed by Young (2001). 

Oxygen isotope data from Clayton and Mayeda (1996), Delaney et al. (2000), and Yamaguchi et al. (2002). 

Baker J. A., MacPherson C. G., Menzies M. A., Thirlwall M. F., Al-Kadasi M., and Mattey D. P. (2000) Resolving crustal and mantle contributions to continental flood volcanism, Yemen constraints from mineral oxygen isotope data. J. Petrol. 41, 1805-1820. 

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