Details for EPMA analyzes

Transcription

1 GSA Data Repository Partial resetting of the U-Th-Pb systems in experimentally altered monazite: Nanoscale evidence of incomplete replacement Grand Homme et al. Details for EPMA analyzes All electron probe micro-analyzer (EPMA) analyses were undertaken at ISTerre laboratory (Grenoble, France) on a Jeol JXA First, high contrast backscattered electron of experimental grain (mounted in epoxy) cross section were realized to identify recrystallized areas with a distinct chemical composition (altered domain) from pristine monazite (Mnz1). Additionally, a consistency standard (Moacyr, e.g. standard details summarized in Didier (2013)) was analyzed several times during each analytical session. Quantitative analyses (Table DR2) were carried using an accelerating voltage of 25 kv and a beam current of 50 na. using following X-ray lines: SiKα, UMβ, ThMα, CaKα, PKα, YLα, DyLβ, GdLβ, SmLβ, PrLβ, NdLα, CeLα, LaLα, PbMβ. Sample spectrometer wavelength scans were used for peak and background positions selection. Background was estimated from a two-steps linear regression. Natural minerals and synthetic glasses standards, including Smithsonian REE phosphates, were used for calibration. A calibrated overlap correction of was applied for peak interference of ThMγ on Umβ. U, Th and Pb contents were measured with counting times (peak plus background) of 400 s. For each analysis, a chemical ages (Table DR4) was calculated (Montel et al., 1996) from quantitative analyses, propagating errors through the age equation to obtain ages at 2σ level. Average ages and diagram (Fig. 3B) were obtained using weighted regression procedure using Isoplot 4.15 (Ludwig, 2001). Although background linear interpolation may lead to age imprecision (e.g. Williams et al., 2007), it has here no clear impact on the ages of the pristine monazite (Manangotry) and the consistency standard (Moacyr). Details for LA-ICPMS analyzes U-Th-Pb geochronology of monazite was performed also by laser ablation inductively coupled plasma spectrometry (LA-ICPMS) at the Laboratoire Magmas et Volcans (LMV), Clermont-Ferrand (France). Analytical procedures for monazite dating are reported in detail in Didier et al. (2013) and Didier et al. (2014). Errors are given at the 2σ level and the spot size is 7 µm (Table DR3). Monazite data are corrected for U Pb and Th Pb fractionation occurring during laser sampling and for instrumental mass discrimination (mass bias) by standard bracketing with repeated measurements of the C83-32 monazite (Corfu, 1988; Didier, 2013). Data reduction was carried out using the GLITTER software package (van Achterbergh et al. 2001; Jackson et al.

2 2004). Calculated ratios were exported and age diagrams were generated using the Isoplot software package by Ludwig (2001). The concentrations of U-Th-Pb were calibrated with respect to the contents of the C83-32 monazite (Corfu, 1988; Didier et al., 2013). Details for TEM The TEM foils were prepared with the HELIOS 600i FIB Dual Beam instrument at LAAS- CNRS RENATECH network. TEM studies were carried out with the JEOL 2100F TEM at the Raimond Castaing center (Toulouse, France), operating at 200 KeV, equipped with an Energy Dispersive Spectrometer (EDS), and a High-Angle Annular Dark Field (HAADF) detector used in the Scanning Transmission Electron Microscopy (STEM) mode. Corfu, F., 1988, Differential response of U-Pb systems in coexisting accessory minerals, Winnipeg river subprovince, canadian shield - implications for Archean crustal growth and stabilization: Contributions to Mineralogy and Petrology, v. 98, no. 3, p , doi: /BF Didier A (2013) Comportement géochimique du chronomètre U-Th-Pb dans la monazite : approche par analyses in-situ au LA-ICP-MS. Phd, Université Blaise Pascal (France) Didier, A., Bosse, V., Boulvais, P., Bouloton, J., Paquette, J.-L., Montel, J.-M., and Devidal, J.- L., 2013, Disturbance versus preservation of U Th Pb ages in monazite during fluid rock interaction: textural, chemical and isotopic in situ study in microgranites (Velay Dome, France): Contributions to Mineralogy and Petrology, v. 165, no. 6, p , doi: /s Didier, A., Bosse, V., Cherneva, Z., Gautier, P., Georgieva, M., Paquette, J.L., and Gerdjikov, I., 2014, Syn-deformation fluid-assisted growth of monazite during renewed high-grade metamorphism in metapelites of the Central Rhodope (Bulgaria, Greece): Chemical Geology, v. 381, p , doi: /j.chemgeo Jackson, S.E., Pearson, N.J., Griffin, W.L., and Belousova, E.A., 2004, The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U-Pb zircon geochronology: Chemical Geology, v. 211, no. 1-2, p , doi: /j.chemgeo Ludwig KR (2001) Isoplot/Ex rev A Geochronological Toolkit for Microsoft Excel. Berkeley Geochronology center. Special publication, No.1a

3 Montel, J.-M., Foret, S., Veschambre, M., Nicollet, C., and Provost, A., 1996, Electron microprobe dating of monazite: Chemical Geology, v. 131, no. 1, p Williams, M.L., Jercinovic, M.J., Goncalves, P., Mahan, K., 2006, Format and philosophy for collecting, compiling, and reporting microprobe monazite ages. Chem. Geol. 225, doi: /j.chemgeo

4 Figure DR1. Localization of LA-ICPMS analyzes on BSE images of reacted monazites. Numbers correspond to the analyzes presented in Table DR3 (first two numbers of the analyzes label).

5 Table DR1 Experimental conditions Run T ( C) P (Mpa) Duration (days) Mnz SiO 2 H 2 O NaOH 1M NaOH 2M Solids and fluids in mg

6 Table DR2 Mean monazite compositions (wt.%) Run Comment n T ( C) P (MPa) duration (days) SiO 2 P 2 O 5 CaO Y 2 O 3 La 2 O 3 Ce 2 O 3 Pr 2 O 3 Nd 2 O 3 Sm 2 O 3 Gd 2 O 3 Dy 2 O 3 PbO ThO 2 UO 2 Total Mnz1 *Starting material mnz SD secondary mnz SD secondary mnz SD secondary mnz SD secondary mnz secondary mnz SD secondary mnz SD *Mean of 51 analyzes in unaltered zones of all experiments listed in Table1. SD: standard deviation

7 Table DR3 LA-ICPMS analyzes Concentrations Isotopic ratios Ages (Ma) 207 Analysis # Run [Th] ppm [U] ppm [Pb] ppm Th/U Pb/ 235 U 206 ± 2 Pb/ 238 U 208 ± 2 Pb/ 232 Th 207 ± 2 Pb/ 235 U ± Pb/ 238 U ± Pb/ 232 Th ± 2 * d * d d d d d d d d d d d d d d d d d d d *: analyzes on grain core (Mnz1)

8 Table DR4 U-Th-Pb EPMA analysis and chemical ages (2 uncertainty) of hydrothermal experiment products Analysis UO 2 ThO 2 PbO Mnz1 domain Age (Ma) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± b ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 25

9 Table DR4 U-Th-Pb EPMA analysis and chemical ages (2 uncertainty) of hydrothermal experiment products Analysis UO 2 ThO 2 PbO Age (Ma) ± ± ± ± ± ± 23 Average 554 ± C ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 24 Average 198 ± C ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 17

10 Table DR4 U-Th-Pb EPMA analysis and chemical ages (2 uncertainty) of hydrothermal experiment products Analysis UO 2 ThO 2 PbO Age (Ma) ± ± 15 Average 163 ± C ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± bdl 0 ± - Average 71 ± 27 bdl : below detection limit