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Jean-luc Devidal – One of the best experts on this subject based on the ideXlab platform.

  • Understanding preservation of primary signatures in Apatite by comparing matrix and zircon-hosted crystals from the Eoarchean Acasta Gneiss Complex (Canada)
    Geochemistry Geophysics Geosystems, 2020
    Co-Authors: C. Antoine, Emilie Bruand, Martin Guitreau, Jean-luc Devidal

    Abstract:

    A novel way to investigate the petrogenesis of ancient poly-metamorphosed terranes is to study zircon-hosted mineral inclusions, which are sensitive to melt evolution such as Apatite. Recent contributions on such inclusions in unmetamorphosed granitoids can provide valuable petrogenetic information and, in turn, represent a way to circumvent effects of metamorphism. Yet, the impact of metamorphism on Apatite inclusion has never been studied in detail. To address the issue of chemical and isotopic preservation of primary signals in Apatite crystals both in the matrix and armored within zircons, we have studied Apatite crystals from four 3.6-4.0 Ga TTG granitoids from the Acasta Gneiss Complex (Canada). Our results demonstrate that U-Th-Pb isotope systematics in matrix Apatite crystals were reset at 1.8-1.7 Ga (Wopmay orogen) whereas primary REE signatures were preserved in many crystals. In contrast, zircon-hosted Apatite inclusions all preserved primary REE signatures despite variable ages between 1.7 and 4.0 Ga. We interpret reset ages to be a consequence of metamorphism that managed to affect U-Th-Pb systematics because of advanced radiation damage accumulation in host-zircon lattices. Only the most pristine zircon crystal has an Apatite inclusion with a concordant age consistent with the magmatic age of the zircon (4.0 Ga). In addition, our results show that Apatite crystals from TTG have distinct REE composition from post-Archean granitoids Apatites, that is preserved even in some Apatites with reset ages. This capacity to retain primary information and discriminate granitoid types makes Apatite a very valuable tool for reconstructing the nature and evolution of ancient crustal rocks through the use of detrital minerals.

  • Apatite solubility in carbonatitic liquids and trace element partitioning between Apatite and carbonatite at high pressure
    Geochimica et Cosmochimica Acta, 2010
    Co-Authors: Tahar Hammouda, Julien Chantel, Jean-luc Devidal

    Abstract:

    Abstract We have measured Apatite solubility in calcic carbonatitic liquids and determined Apatite/melt partition coefficients for a series of trace elements, including the rare earth elements (REE), high field strength elements (HFSE), Rb, Sr, U–Th–Pb. Experiments were performed between 4 and 6 GPa, from 1200 to 1380 °C, using the multianvil apparatus. Trace element concentrations were determined by laser ablation ICP-MS and electron microprobe. In addition, a specific protocol was designed to measure carbon concentration in the Apatites, using the electron microprobe. Two starting Apatite samples were used in order to test for the effect of Apatite chemistry on partitioning behavior. Apatite solubility is lower in calcitic melts by a factor 3–5 compared to dolomitic melts (3–5.5 vs. 10–18 wt.% P2O5 in melt). We interpret this difference in terms of solubility product in the liquid and propose an empirical model for Apatite saturation that takes into account melt calcium content. We conclude that calcitic melts that may form by melting of carbonated eclogites could be saturated with residual Apatite, contrary to dolomitic melts formed in carbonated peridotites. Compatibility behavior of the REE depends on Apatite silica content: REE are compatible in Apatites containing 3.5–5 wt.% SiO2, with D REE Apatite/carbonatite values between 1.5 and 4, whereas REE are incompatible in Apatites containing 0.2 wt.% SiO2. HFSE, U, Th, and Y are compatible in silica-rich Apatite, with D Th Apatite/carbonatite ⩾ 5 while D Y Apatite/carbonatite ⩾ 2 . Strontium is always retained in the melt, with D Sr Apatite / carbonatite of the order of 0.5. Lead appears to be incompatible in Apatite, although this finding is weakened by almost complete Pb loss to sample container. High silica concentration favors REE incorporation in Apatite by allowing for charged balanced coupled substitution. Sulfur and carbonate may also favor REE incorporation in Apatite. Our results allow to reconcile previously published experimental determinations of REE partitioning. We use our experimentally determined partition coefficients to investigate the impact of residual Apatite during partial melting of recycled carbonated material (eclogite + sediments) and discuss how the chemical characteristics of the produced liquids can be affected by residual Apatite.

Raymond A Donelick – One of the best experts on this subject based on the ideXlab platform.

  • variability of Apatite fission track annealing kinetics i experimental results
    American Mineralogist, 1999
    Co-Authors: William D Carlson, Raymond A Donelick, Richard A Ketcham

    Abstract:

    Annealing rates for fission tracks in Apatite vary markedly as a complex function of composition, based on an experimental study of 15 well-characterized, compositionally diverse Apatites. Extensive annealing data were obtained in 69 experiments (durations of 1, 10, 100, and 1000 h at temperatures from 75 to 400 °C) on each of four Apatites, three with near end-member occupancy of the halogen site by F, Cl, and OH, plus the well-known Apatite from Durango, Mexico. These results were supplemented by less-comprehensive annealing data from 12 experiments over the same range of time and temperature on each of the remaining 11 Apatites. Measurements of initial fission-track length, a parameter of considerable importance to the derivation of time-temperature paths from fission-track data, reveal substantial variations from one Apatite to another; initial lengths are best predicted from etch figures. Interlaboratory comparisons of data on annealing kinetics highlight discrepancies that appear to result largely from differences in the precision and accuracy of experimental temperatures. None of the factors previously proposed as the dominant compositional controls on annealing rates can account completely for annealing behavior over the full range of compositions studied. Nevertheless, relative rates of annealing among all Apatites are highly systematic, which allows this data set to be used in its entirety to constrain multikinetic annealing models that predict fission-track lengths as a function of time and temperature. In this article, we present experimental data on the rates of fission-track annealing in 15 well-characterized Apatites of widely diverse chemistry, and compare our results to previously published experimental work. Companion articles present a technique for increasing the precision of analyses of natural and experimental fission-track measurements by accounting for the dependence of annealing rate on crystallographic orientation (Donelick et al. 1999, this volume), and introduce (Ketcham et al. 1999, this volume) a multikinetic empirical model, based on these new experimental data, that can be used to predict the thermal annealing behavior of Apatite in compositionally diverse populations as a function of time and temperature. EXPERIMENTAL METHODS

  • variability of Apatite fission track annealing kinetics iii extrapolation to geological time scales
    American Mineralogist, 1999
    Co-Authors: Richard A Ketcham, Raymond A Donelick, William D Carlson

    Abstract:

    A new model for examining fission-track data from natural specimens has been developed on the basis of new laboratory data describing fission-track annealing in a wide variety of Apatites and the empirical correction for fission-track length anisotropy presented in earlier papers. Using revised and simplified statistical methods, we examine how well various empirical equations are able to fit the laboratory data and reproduce expected behavior on geological time scales. Based on the latter criterion, we find that so-called “fanning Arrhenius” models of mean track length are not the best-suited for our data. Instead, we find that fitting c-axis projected lengths with a model that incorporates some curvature on an Arrhenius plot produces results that are in better agreement with the available geological benchmarks. In examining the relative annealing behavior of Apatites with different resistance to annealing, we find that the laboratory-time-scale behavior of any two Apatites can be reproduced well by a simple one- or two-parameter equation. This function is used to convert the reduced fission-track length of one Apatite that has undergone a certain time-temperature history into the length that would be measured in a second, less-resistant Apatite that has undergone the same history. Using this conversion, we create a single model that encompasses the annealing behavior of all of the Apatites we studied. The predictions made by this model match closely those made by fits to data for individual Apatites. We therefore infer that, although the conversion equation is imperfect, it presents an excellent practical solution to characterizing the range of kinetic variability for annealing of fission tracks in Apatite.

Richard A Ketcham – One of the best experts on this subject based on the ideXlab platform.

  • variability of Apatite fission track annealing kinetics i experimental results
    American Mineralogist, 1999
    Co-Authors: William D Carlson, Raymond A Donelick, Richard A Ketcham

    Abstract:

    Annealing rates for fission tracks in Apatite vary markedly as a complex function of composition, based on an experimental study of 15 well-characterized, compositionally diverse Apatites. Extensive annealing data were obtained in 69 experiments (durations of 1, 10, 100, and 1000 h at temperatures from 75 to 400 °C) on each of four Apatites, three with near end-member occupancy of the halogen site by F, Cl, and OH, plus the well-known Apatite from Durango, Mexico. These results were supplemented by less-comprehensive annealing data from 12 experiments over the same range of time and temperature on each of the remaining 11 Apatites. Measurements of initial fission-track length, a parameter of considerable importance to the derivation of time-temperature paths from fission-track data, reveal substantial variations from one Apatite to another; initial lengths are best predicted from etch figures. Interlaboratory comparisons of data on annealing kinetics highlight discrepancies that appear to result largely from differences in the precision and accuracy of experimental temperatures. None of the factors previously proposed as the dominant compositional controls on annealing rates can account completely for annealing behavior over the full range of compositions studied. Nevertheless, relative rates of annealing among all Apatites are highly systematic, which allows this data set to be used in its entirety to constrain multikinetic annealing models that predict fission-track lengths as a function of time and temperature. In this article, we present experimental data on the rates of fission-track annealing in 15 well-characterized Apatites of widely diverse chemistry, and compare our results to previously published experimental work. Companion articles present a technique for increasing the precision of analyses of natural and experimental fission-track measurements by accounting for the dependence of annealing rate on crystallographic orientation (Donelick et al. 1999, this volume), and introduce (Ketcham et al. 1999, this volume) a multikinetic empirical model, based on these new experimental data, that can be used to predict the thermal annealing behavior of Apatite in compositionally diverse populations as a function of time and temperature. EXPERIMENTAL METHODS

  • variability of Apatite fission track annealing kinetics iii extrapolation to geological time scales
    American Mineralogist, 1999
    Co-Authors: Richard A Ketcham, Raymond A Donelick, William D Carlson

    Abstract:

    A new model for examining fission-track data from natural specimens has been developed on the basis of new laboratory data describing fission-track annealing in a wide variety of Apatites and the empirical correction for fission-track length anisotropy presented in earlier papers. Using revised and simplified statistical methods, we examine how well various empirical equations are able to fit the laboratory data and reproduce expected behavior on geological time scales. Based on the latter criterion, we find that so-called “fanning Arrhenius” models of mean track length are not the best-suited for our data. Instead, we find that fitting c-axis projected lengths with a model that incorporates some curvature on an Arrhenius plot produces results that are in better agreement with the available geological benchmarks. In examining the relative annealing behavior of Apatites with different resistance to annealing, we find that the laboratory-time-scale behavior of any two Apatites can be reproduced well by a simple one- or two-parameter equation. This function is used to convert the reduced fission-track length of one Apatite that has undergone a certain time-temperature history into the length that would be measured in a second, less-resistant Apatite that has undergone the same history. Using this conversion, we create a single model that encompasses the annealing behavior of all of the Apatites we studied. The predictions made by this model match closely those made by fits to data for individual Apatites. We therefore infer that, although the conversion equation is imperfect, it presents an excellent practical solution to characterizing the range of kinetic variability for annealing of fission tracks in Apatite.