Geology topics
Priestley Toulmin
Publications and source records attributed to Priestley Toulmin.
Mass spectrometric analysis of organic compounds, water and volatile constituents in the atmosphere and surface of Mars: The Viking Mars Lander
An experiment centering around a mass spectrometer is described, which is aimed at the identification of organic substances present in the top 10 cm of the surface of Mars and an analysis of the atmosphere for major and minor constituents as well as isotopic abundances. In addition, an indication of the abundance of water in the surface and some information concerning the mineralogy can be obtained by monitoring the gases produced upon heating the soil sample. The organic material will simply be expelled by heating to 150°, 300°, and 500° into the carrier gas stream of a gas chromatograph interfaced to the mass spectrometer or by slowly heating the sample in direct communication with the spectrometer. It is planned to analyze a total of up to nine soil samples in order to study diurnal and seasonal variations. The system is designed to give useful data even for minor constituents if the total of organics should be as low as 5ppm. The spectrometer covers the mass range of 12–200 with adequate resolution. The results of these experiments, which are deliberately designed to cover a wide spectrum of possibilities independent of terrestrial models, are expected to produce a good picture of the planet's organic chemistry and its possible biological significance as well as allow conclusions regarding the history of the planet's atmosphere.
Phase relations involving sphalerite in the Fe-Zn-S system
The equilibrium diagram for the Fe - Zn - S System has been worked out in détail from 580° to 850° C. Previous work on this System is proven to be seriously in error and températures heretofore estimated from the " sphalerite geothermometer" are without a sound quantitative foundation. Sphalerite solid solutions lie essentially along the FeS-ZnS join. Neither pyrite nor pyrrhotite takes up appréciable amounts of zinc. The FeS-ZnS binary solvus (équivalent to the assemblage sphalerite + stoichi-ometric FeS) is very steep, passing through 56 mole percent FeS at 850° C and 52 mole percent FeS at 580° C. It is not useful geologically because of the rarity of stoichiometric FeS as a primary minerai in sphalerite -bearing assemblages; however, the relatively large rôle played by total pressure on the binary solvus might permit the iron content of sphalerite to be useful in determining the pressure of équilibration of some météorites. Of greater géologie interest is the sphalerite + pyrite + pyrrhotite assemblage in which the composition of sphalerite changes from 13 mole percent FeS at 742° C to 19 percent at 580° C. Unfortunately, this equilibrium cannot be quantitatively extrapolated to lower températures from the presently available data and therefore quantitative geothermom-etry of pyrite + pyrrhotite + sphalerite assemblages is not feasible at présent. Thermochemical calculations prove that the iron content of sphalerite in pyrite + sphalerite assemblages is very sensitive to variations in température and fugacity of S 2; this relationship provides an explanation of growth-zoned sphalerite as the resuit of fluctuations of sul-fur fugacity, and, in combination with other sulfide assemblages that define isobarically univariant relations between température and sulfur fugacity, forms a potential basis for quantitative geothermometry.
Bedrock geology of the Salem quadrangle and vicinity, Massachusetts
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Geological significance of lead-alpha and isotopic age determinations of "alkalic" rocks of New England
Recent age determinations indicate that at least two groups of " alkalic " igneous rocks exist in New England , with ages of about 185 and 270 million years. Because of their lithologic and geologic similarities, all these rocks had previously been grouped with the White Mountains plutonic-volcanic series of New Hampshire. Until reliable petrographic or geologic criteria become available for distinguishing these age groups, caution should be exercised in assigning any undated body of " alkalic " rock to one or the other group.