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There has already been some interest expressed by archaeologists about the possibility of non-destructive radiocarbon dates. With National Science Foundation support, we thus hope to demonstrate beyond question that we can produce accurate dates and d13C values utilizing plasma-chemical extraction of minute amounts of carbon. The Feidong Complex crops out within the northeastern Yangtze Craton and was previously considered to represent the Paleoproterozoic basement of the craton (Anhui Geological Survey, 1987; Fig. 1b). This study presents new zircon U–Pb and Lu–Hf isotopic, whole–rock geochemical, and Sr–Nd isotopic data for early Paleoproterozoic orthogneisses of the Feidong Complex within the northeastern margin of the Yangtze Craton. These new data, together with data from contemporaneous magmatic and metamorphic events within this region, allow the further delineation of the late Neoarchean–early Paleoproterozoic tectonic evolution of the northern Yangtze Craton.

& Giardini, D. Fate of the Cenozoic Farallon slab from a comparison of kinematic thermal modeling with tomographic images. Hafkenscheid, E., Wortel, M. & Spakman, W. Subduction history of the Tethyan region derived from seismic tomography and tectonic reconstructions. Solid Earth 111, B08401 . Gard, M., Hasterok, D. & Halpin, J. A. Global whole-rock geochemical database compilation.

Luminescence dating methods

One good example is granite, which normally has some potassium feldspar (Figure 14.15). The rubidium-strontium dating method is a radiometric dating technique, used by scientists to determine the age of rocks and minerals from their content of specific isotopes of rubidium and strontium . One of the two naturally occurring isotopes of rubidium, 87Rb, decays to 87Sr with a half-life of 49.23 billion years. The radiogenic daughter, 87Sr, produced in this decay process is the only one of the four naturally occurring strontium isotopes that was not produced exclusively by stellar nucleosynthesis predating the formation of the Solar System. Over time, decay of 87Rb increases the amount of radiogenic 87Sr while the amount of other Sr isotopes remains unchanged.

Geology and geochemistry of the Changba SEDEX Pb–Zn deposit, Qinling orogenic belt, China

Considering the specific isotopic and metallogenic features of the Mesozoic granitoids in the study area, we propose that the western Nanling Range may represent a western extension of Neoproterozoic arc–continent collisional belt in South China. The Mesozoic granitoids of this area may have been generated mainly by reworking of deeply-buried Neoproterozoic arc-related volcanic-sedimentary materials due to thermal perturbations triggered by the subduction of the Paleo-Pacific Plate in Mesozoic time. Fragments of wood incorporated into young sediments are good candidates for carbon dating, and this technique has been used widely in studies involving late Pleistocene glaciers and glacial sediments. An example is shown in Figure 8.16; radiocarbon dates from wood fragments in glacial sediments have been used to estimate the time of the last glacial advance along the Strait of Georgia.

However, the data is not totally tested by ore minerals, the measurement error range is relatively large, and the age is a little older than that of its host rocks. The main objection with regard to sedimentary rock is that you can date the individual mineral grains with isotopic techniques but not when they were laid down together. All metamorphic rocks show some degree of new crystal growth whether through melting of the existing rock or additional material being deposited by transiting geothermal fluids, often both, it is those new crystals that can be dated. Therefore it depends on the mechanism of metamorphosis occurred to determine if you can use isotopic ratios after metamorphosis and which techniques are viable. Rocks that are metamorphosed through the presence of nearby intrusions of igneous rock can be dated to that intrusion using isotopic dating of the resulting deposits.

Nature 535, 140–143 . Torsvik, T. H., Steinberger, B., Gurnis, M. & Gaina, C. Plate tectonics and net lithosphere rotation over the past 150 My. Evolution of Earth’s tectonic carbon conveyor belt. Nature 605, 629–639 .

A more robust mineral to use to date certain types of igneous and metamorphic rocks is zircon. Zircon is a mineral that incorporates uranium into its structure at the time of formation. One of the isotopes of uranium decays to lead with a long half-life (see Table 19.2). Zircon is a mineral of choice for dating because it takes no lead into its structure when it forms, so any lead present is due entirely to the radioactive decay of the uranium parent.

Potassium argon vs radiocarbon dating

The rock sample to be dated must be chosen very carefully. Any alteration or fracturing means that the potassium or the argon or both have been disturbed. The site also must be geologically meaningful, clearly related to fossil-bearing rocks or other features that need a good date to join the big story.

Different methods of radiometric dating vary in the timescale over which they are accurate and the materials to which they can be applied. The importance of internal checks as well as interlaboratory comparisons becomes all the more apparent when one realizes that geochronology laboratories are limited in number. Because of the expensive equipment necessary and the combination of geologic, chemical, and laboratory skills required, geochronology is usually carried out by teams of experts. Most geologists must rely on geochronologists for their results.

To second order, geodetic data reveal that around 14% of the surface of the Earth is presently characterized by morediffuse deformation84,85 across widened boundary regions. Such regions include both compressional, orogenic belts and regions of continental extension . Constraining the timing and magnitude of analogous deformation in the geological past is complex at a broad range of length scales and relies on a diverse range of evidence.