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Mudstone--the most abundant sedimentary rock type, composed primarily of clay- or silt-sized particles--contains most of the quartz found in sedimentary rocks. These quartz grains, which are chemically and mechanically resistant and therefore preserve their characteristics well, have long been considered to be derived from the continental crust. Here we(More)
Observations of martian surface morphology have been used to argue that an ancient ocean once existed on Mars. It has been thought that significant quantities of such water could have been supplied to the martian surface through volcanic outgassing, but this suggestion is contradicted by the low magmatic water content that is generally inferred from(More)
Quartz cement microstratigraphy and high precision in situ δ 18 O values obtained by secondary ion mass spectrometry (SIMS) from μm-size quartz cement zones have been used here to determine the timing of cementation and to evaluate precipitation mechanisms within the basal sandstones of three economically significant Paleoproterozoic basins, the Athabasca(More)
A method for in situ U–Pb isotopic analyses by secondary ion mass spectrometry (SIMS) has been developed for uranium minerals with a range of chemical compositions. This method combines the advantages of conventional U–Pb dating (i.e., use of concordia) and in situ analysis, and therefore is ideally suited for the study of chemically complex and(More)
Bioprecipitated minerals are typically at the nanometer scale, hydrous, and beam-sensitive (i.e., can recrystallize during analysis), making them diffi cult to characterize using standard spectroscopic or electron-beam techniques. We have combined the ion-imaging capabilities of nanoscale secondary-ion mass spectrometry (NanoSIMS) and advanced(More)
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