Geological samples minerals

Pickett D, Mtrrrell MT, Williams RW (1994) Determination of femtogram qrrantities of protactinium in geologic samples by thermal ionization mass spectrometry. Anal Chem 66 1044-1049 Porcelli D, Swarzertski PW (2003)The behavior of U- and Th- series nuclides in grormdwater. Rev Mineral Geochem 52 317-361... 

Ulbrich and Waldbaum [14] pointed out that calorimetrically determined third law entropies for many geologically important minerals may be in error because site mixing among cations, magnetic spin disorder, and disorder among water molecules in the crystals is frozen in the samples used for calorimetric measurements. They have calculated corrections based on known crystallographic data for several minerals. 

In this research, the purpose of the cluster analysis Is to obtain groupings of samples with compositions similar to specific minerals or with only a subset of all the minerals In the bulk sample. This Is necessary In most geological samples In order to... 

Real geological samples rarely exhibit a specific number of mineral components. Such samples are composed of a multitude of minerals that are qualitatively referred to as major, minor, and trace components. The sensitivity of the particular analytical method limits our ability to resolve these minerals. Here we determine the number of mineral components (NC) from the elgenanalysls of the raw data matrix. The raw data matrix Is approximated by a successively Increasing number of eigenvectors. When this approximated data matrix Is within the expected uncertainty of the data, we... 

Frequently two or more species are found together in the same geologic sample. As pressure-temperature conditions become more severe, the mineralogy becomes more simple, feldspar appears and finally within the limits of clay mineral stabilities only calcic zeolites are found. However, the calcic minerals are generally confined to rocks of basic... 

Geology Dating of geological samples - rocks and minerals Rb- Sr, Sm- Nd, 187Re 1870s, 238y 206p 3 ... 

This involves the use of mineral or oxidizing acids and an external heat source to decompose the sample matrix. The choice of an individual acid or combination of acids dep>ends upon the nature of the matrix to be decomposed. For example, the digestion of a matrix containing silica, Si02 (e.g. a geological sample), requires the use of hydrofluoric acid (HF). A summary of the most common acids used for digestion and their application is shown in Table 27.3. 

Dc arc spectrography is still a most powerful method for trace determinations in solids even with difficult matrices such as U3Og. Here the detection limits for many elements are down in the sub-pg/g range [358]. It is still in use for survey analysis, especially in the case of ores, minerals and geological samples. In work with unipolar arcs, re-ignition of the arc is often facilitated by providing an hf discharge over the dc arc, by which the arc channel is kept electrically conductive. 

In the analysis of geological samples, sample dissolution with respect to nebu-lization effects but also to ionization interferences is important [399], The analysis of rare earth minerals without [420] and with removal of the matrix has been reported. 

Trace amounts of Th in geological samples were determined after conversion into molybdothoric acid and reaction with basic dyes [4]. Thorium in ores and minerals was determined using the ternary purple-coloured complex formed between Th(IV), bromocresol orange and cetylpyridinium bromide (X = 560 nm e = 9.2 x 10 1 mof cm ) [5]. 

Thompson AC, Underwood JH, Wu Y, Giauque RD, Jones KW, Rivers ML (1988) Elemental measurements with an X-ray microprobe of biological and geological samples with femtogram sensitivity. Nucl Instrum Meth Phys Res A 266 318-323 Thompson HA, Brown GE Jr, Parks GA (1995) Low and ambient temperature XAFS study of U(VI) in solids and aqueous solutions. Physica 208 209 167-168 Thompson HA, Brown GE Jr, Parks GA (1997) XAFS spectroscopic study of uranyl coordination in solids and aqueous solution. Am Mineral 82 483-496... 

This method is more reliable than the helium method since there is very little possibility of any of the lead that has been formed by radioactive decay having diffused or been leached from the mineral during its geologic age. Mineral samples from the earth have yielded values as great as 3 X 10 y by the lead content method. Unfortunately, there is a problem with this method also. The decay series all pass through isotopes of the inert gas radon, and if some of the radon is lost from the mineral the Pb content leads to an erroneously low age. However, if relation (5.13) is used for different decay series (i.e. the and the series) and the same t is obtained, the data are said to be concordant. Such data increases the confidence in the measured age. 

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