Minerals analysis strategy

Perkins, W. T., Pearce, N. J. G., and Westgate, J. A. (1997). The development of laser ablation ICP-MS and calibration strategies examples from the analysis of trace elements in volcanic glass shards and sulfide minerals. Geostandards Newsletter 21 175-190. 

In addition to providing the means for calculating the isotopic compositions of ancient fluids based on analysis of minerals, mineral-fluid isotope fractionation factors provide an opportunity to combine fractionation factors when there is a common substance such as water. A fundamental strategy for compiling databases for isotopic fractionation factors is to reference such factors to a common substance (e.g., Friedman and O Neil 1977). For example, the quartz-water fractionation factor may be combined with the calcite-water fractionation factor to obtain the quartz-calcite fractionation factor at some temperature. It is now recognized, however, that the isotopic activity ratio of water in a number of experimental determinations of mineral-fluid fractionation factors has been variable, in part due to dissolution of... 

The measurement of isotope fractionation between two equilibrated phases yields one estimate of temperature, and n phases yield (n - 1) temperatures. In the real world where equilibrium may be imperfectly attained, recorded, or preserved, analysis of n minerals provides at least (n - 1) estimates of apparent temperature (Ta) and often many more. These values of Ta may represent the true temperature of a meaningful geologic event or they may be spurious. The choices of both the appropriate strategy of analysis and the correct interpretation will depend on the history of the rock. 

Fine-grained carbonates containing dolomite or siderite require a different strategy. If isotopic value of the bulk carbonate material is desired, the prepared sample can simply be reacted at a high temperature (Rosenbaum Sheppard, 1986) since the reaction rate of dolomite and siderite in phosphoric acid is very slow at 25 or even 70 °C. If isotopic values of individual carbonate minerals are desired, then this can at least be accomplished partially. The prepared material can first be reacted at 25 °C for just 1 hour, which should leave intact resistant fractions such as dolomite and siderite. The residue is then washed and dried and reacted at the requisite high temperature. In my laboratory, when this method is employed, we spot-check some samples by subjecting them to XRD-analysis both before and after the 25 °C reaction. 

Numerous applications for online LC-GC have been described for all important fields of analysis (summarized in Further Reading), but more than half of the methods applied concern mineral oil and edible oil or fat. A few are briefly outlined to illustrate typical strategies and conditions. 

It is clear from this analysis that high entropy is associated with high recovery costs in mineral refining. The same principle applies to recycling strategies where, to be economic, it is necessary to reduce the entropy of a resource like municipal waste by presorting the more valuable components. Furthermore, it seems likely that in most instances, the major component of what is meant by consumption is the increase in entropy which occurs when a resource is consumed. 

While it would be impossible to examine all of the viewpoints that writers represent in all 25 appendices, two documents in particular help us analyze the rhetorical processes by which local knowledge moves into the domain of science and public policy. Appendix F contains Blake s hand written account of his escape, written immediately after the accident. Appendix H contains Nagy s independent analysis of miners testimony following the accident. Blake s narrative enables us to view the uncertain and dynamic geography of a mine from the viewpoint of a miner focused on his own survival. His viewpoint is limited to his own experience, but his narrative reveals how he used sensory cues in the environment to save his life. Nagy s report reveals the rhetorical strategies that one fire consultant employed as he attempted to reconcile conflicting accounts of the disaster in order to reconstruct a coherent and consistent narrative of events and conditions that precipitated the disaster. 

---