In situ dating

In situ dating of U-Th rich accessory ndnerals. Recent instmmental developments... 

Stern R. A. and Berman R. G. (2001) Monazite U-Pb and Th-Pb geochronology by ion microprobe, with an application to in situ dating of an Archean metasedimentary rock. Chem. Geol. 172(1-2), 113-130. 

Swindle TD (2001) Could in situ dating work on Mars Lunar Planet Sci XXXII, Abstr 1492 (CD-ROM) Swindle TD (2002) Noble gases in the Moon and meteorites Radiogeiuc components and early volatile chronologies. Rev Mineral Geochem 47 101-124... 

FIGURE 31.1 Microphotograph (transmitted light) of small zircon grains exhibiting cracks and inclusions, which can be avoided using in situ dating (scale bar 50 pm). 

Some questions may need to be answered in this preliminary section for scientists not directly involved in geosciences (1) What is the specific interest of in situ dating (2) Why is the U-Pb system so frequently used to date minerals (3) Why is zircon one of the best candidates for dating geological events ... 

J. (2003) Laser-ablation U/Th-Pb in situ dating of zircon and allanite an example from the October Harbour granite, central coastal Labrador, Canada. Can. Mineral, 41, 273-291. 

Basu., B., Date, A.W. Int. J. Heat Mass Transfer, 33 (1990) Nr. 6, S.l 149 Haferkamp, H., Gerken, J., Stegemann, D., Reichert, Ch. In-situ Untersuchung des Hartstofftransports beim Laserstrahl-Dispergieren mittels Hochgeschwindigkeits-Radioskopie, Metall, Nr. 3/96... 

Gewirth A A and Niece B K 1997 Electrochemical applications of in situ scanning probe microscopy Chem. Rev. 97 1129-62 Up to date summary of scanning probe studies with many literature and examples. 

Filter and aggregate must be clearly marked with the type and designation of the filter, date of installation, etc. fn the case of more stringent requirements, in situ checks of the filter are carried out according to Eurovent 4/10. 

The very new techniques of scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) have yet to establish themselves in the field of corrosion science. These techniques are capable of revealing surface structure to atomic resolution, and are totally undamaging to the surface. They can be used in principle in any environment in situ, even under polarization within an electrolyte. Their application to date has been chiefly to clean metal surfaces and surfaces carrying single monolayers of adsorbed material, rendering examination of the adsorption of inhibitors possible. They will indubitably find use in passive film analysis. 

Several volcanic centers from the Kenya Rift Valley in East Africa were studied by Black et al. (1997, 1998). Four U-Th isochrons were obtained from trachytes from Emuruangogolak and Paka volcanoes (Black et al. 1998) their crystallization ages range from 9.3 to 39.5 ka and are in full agreement with in situ Ar- Ar laser dating of... 

Figure 14. ratios vs. model ages obtained by in situ ion mieroprobe dating of... 

Further advances in the interpretation of mineral data could come from in situ analyses (unfortunately only possible presently on U-Th rich accessory minerals like zircon), or from detailed studies of particularly large phenocrysts, whose successive growth zones could be sampled (e g., through microdrillings) and analyzed. Ra measurements in such crystals could allow a direct determination of their growth rates. A systematic study of successive, well-dated eruptions of a given volcano, combining U-series measurements in both whole rocks and minerals, should also help with the interpretation of mineral data. 

The in situ monitoring of high temperature reactions by hpl29Xe magnetic resonance is still in its infancy. Although the previous work on gas phase dynamics in porous media has shown the feasibility of dynamic microscopy and M RI and the first in situ combustion NMR spectra have been collected, much more development remains to be done. To date, hpl29Xe NMR and MRI are currently the only techniques available to study gas dynamics in porous and opaque systems. 

Table 1 summarizes several of the experimental methods discussed in this chapter. A need exists for new or revised methods for transport experimentation, particularly for therapeutic proteins or peptides in polymeric systems. An important criterion for the new or revised methods includes in situ sampling using micro techniques which simultaneously sample, separate, and analyze the sample. For example, capillary zone electrophoresis provides a micro technique with high separation resolution and the potential to measure the mobilities and diffusion coefficients of the diffusant in the presence of a polymer. Combining the separation and analytical components adds considerable power and versatility to the method. In addition, up-to-date separation instrumentation is computer-driven, so that methods development is optimized, data are acquired according to a predetermined program, and data analysis is facilitated. 

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