Ekati xenoliths geochemical data and thin section images
The dataset comprises thin section and mount micrographs and geochemical data on forty-one eclogitic and pyroxenitic xenoliths brought to the surface by the Ekati kimberlite 52 Myrs ago. Thin sections images were taken using a Zeiss polarized light microscope equipped with a digital camera. Micro X-ray fluorescence analysis (μXRF) element maps (Si, Ca, Mg, Fe, Al, Ti, Ni, Na, K, P, Cr) of polished surfaces of xenoliths embedded in epoxy resin and of thin sections were generated with a Bruker M4 Tornado Micro-XRF equipped with a Rh anode operating at 50 kV and 200 μA. The chamber was at a 0.5–0.6 mbar vacuum, pixel resolution was 40 μm, with a dwell time 10 ms/pixel. Major element concentrations were determined with a CAMECA SX-50 electron microprobe at C.F. Mineral Research following standard analytical methods. Microprobe calibration procedures were employed using a variety of natural and synthetic oxides and silicates. Analyzing crystals used in the analyses were LiF, PET and TAP. The operating accelerating voltage was 15 kV, with a beam current of 30nA and the beam size maintained at 2 microns. Counting intervals for each element ranged from 10 seconds for major elements and 30-50 seconds for minor elements. The detection limits for K, P and Ni were 0.01 wt%. Trace elements in garnets, clinopyroxenes and ilmenites were analysed in situ by Laser Ablation ICP-MS with an Agilent 7500cs quadrupole ICP-MS coupled with a New Wave Research UP213 Laser at the Department of Geosciences, University of Greifswald, Germany (Jacob, 2006). Ablation was carried out at 10 J/cm2 and 10 Hz, using He as carrier gas. The commercial software GLITTER 4.0 (Griffin et al., 2008) was used for data reduction with NIST SRM 612 as external standard and 43Ca as internal standard using values for CaO from the electron microprobe analyses for the silicates and 47Ti determined as TiO2 for the ilmenites. Optically pure mineral separates of clinopyroxene and garnet for Nd, Sr and O isotope measurements were prepared following methods described in (Jacob et al., 1994). Chemical separation and measurements of the isotopic compositions of Nd and Sr as well as of element concentration of Sr, Nd and Sm by isotope dilution were carried out at the Max-Planck Institut für Chemie using a modified Finnigan MAT 261 mass spectrometer following methods described in (Jacob et al., 1994). Blank contributions were 300 pg for Sr, and 30 pg for Nd and Sm. Neodymium was measured as NdO+ and normalized to 146Nd/144Nd = 0.7219. Values obtained for the La Jolla and the Eimer and Amend standards were 0.51185 ± 3 and 0.70800 ± 4, respectively. Apatite-containing mineral separates of clinopyroxene and garnet from sample GE1 were leached to test for isotopic equilibrium between inclusions and host minerals. The pre-leached mineral separates were finely ground in a thoroughly cleaned boron-carbide mortar (measured blank contribution 15 pg for Nd and Sm) in the clean-lab and the resulting powder was then leached in a Teflon beaker with ultrapure 2.5N HCl at 60°C for 35 min. The residues were washed twice with distilled water, dried down and subjected to the routine dissolution and column separation procedure. Sm and Nd concentrations measured by isotope dilution generally agree within 15% with the Laser ablation ICP-MS data except for garnets from samples LE7 and PGE1. Oxygen isotope ratios were measured at Royal Holloway, University of London (RHUL), using a laser-assisted fluorination technique (Mattey and MacPherson, 1993). Optically clean mineral separates were prepared for analysis, with sample weights for each analysis ranging between 1.0 and 1.8 mg. The grains were rinsed with water and ethanol, but no acid leaching was applied. Values were duplicated and are reported relative to SMOW. Limitations of the dataset are connected to the small sample sizes, which precluded radiogenic isotope analyses for more than four of the samples.
Type
collection
Title
Ekati xenoliths geochemical data and thin section images
Brief Title
Ekati xenoliths
Collection Type
Dataset
Access Privileges
Research School of Earth Sciences
DOI - Digital Object Identifier
10.25911/1a7m-zk43
Metadata Language
English
Data Language
English
Significance Statement
A large dataset on barren eclogite and pyroxenite xenoliths from the Ekati diamond mine in Canada
Brief Description
Major, trace elements and neodymium, strontium, and oxygen isotope data plus thin section and mount images
Full Description
The dataset comprises thin section and mount micrographs and geochemical data on forty-one eclogitic and pyroxenitic xenoliths brought to the surface by the Ekati kimberlite 52 Myrs ago. Thin sections images were taken using a Zeiss polarized light microscope equipped with a digital camera. Micro X-ray fluorescence analysis (μXRF) element maps (Si, Ca, Mg, Fe, Al, Ti, Ni, Na, K, P, Cr) of polished surfaces of xenoliths embedded in epoxy resin and of thin sections were generated with a Bruker M4 Tornado Micro-XRF equipped with a Rh anode operating at 50 kV and 200 μA. The chamber was at a 0.5–0.6 mbar vacuum, pixel resolution was 40 μm, with a dwell time 10 ms/pixel. Major element concentrations were determined with a CAMECA SX-50 electron microprobe at C.F. Mineral Research following standard analytical methods. Microprobe calibration procedures were employed using a variety of natural and synthetic oxides and silicates. Analyzing crystals used in the analyses were LiF, PET and TAP. The operating accelerating voltage was 15 kV, with a beam current of 30nA and the beam size maintained at 2 microns. Counting intervals for each element ranged from 10 seconds for major elements and 30-50 seconds for minor elements. The detection limits for K, P and Ni were 0.01 wt%. Trace elements in garnets, clinopyroxenes and ilmenites were analysed in situ by Laser Ablation ICP-MS with an Agilent 7500cs quadrupole ICP-MS coupled with a New Wave Research UP213 Laser at the Department of Geosciences, University of Greifswald, Germany (Jacob, 2006). Ablation was carried out at 10 J/cm2 and 10 Hz, using He as carrier gas. The commercial software GLITTER 4.0 (Griffin et al., 2008) was used for data reduction with NIST SRM 612 as external standard and 43Ca as internal standard using values for CaO from the electron microprobe analyses for the silicates and 47Ti determined as TiO2 for the ilmenites. Optically pure mineral separates of clinopyroxene and garnet for Nd, Sr and O isotope measurements were prepared following methods described in (Jacob et al., 1994). Chemical separation and measurements of the isotopic compositions of Nd and Sr as well as of element concentration of Sr, Nd and Sm by isotope dilution were carried out at the Max-Planck Institut für Chemie using a modified Finnigan MAT 261 mass spectrometer following methods described in (Jacob et al., 1994). Blank contributions were 300 pg for Sr, and 30 pg for Nd and Sm. Neodymium was measured as NdO+ and normalized to 146Nd/144Nd = 0.7219. Values obtained for the La Jolla and the Eimer and Amend standards were 0.51185 ± 3 and 0.70800 ± 4, respectively. Apatite-containing mineral separates of clinopyroxene and garnet from sample GE1 were leached to test for isotopic equilibrium between inclusions and host minerals. The pre-leached mineral separates were finely ground in a thoroughly cleaned boron-carbide mortar (measured blank contribution 15 pg for Nd and Sm) in the clean-lab and the resulting powder was then leached in a Teflon beaker with ultrapure 2.5N HCl at 60°C for 35 min. The residues were washed twice with distilled water, dried down and subjected to the routine dissolution and column separation procedure. Sm and Nd concentrations measured by isotope dilution generally agree within 15% with the Laser ablation ICP-MS data except for garnets from samples LE7 and PGE1. Oxygen isotope ratios were measured at Royal Holloway, University of London (RHUL), using a laser-assisted fluorination technique (Mattey and MacPherson, 1993). Optically clean mineral separates were prepared for analysis, with sample weights for each analysis ranging between 1.0 and 1.8 mg. The grains were rinsed with water and ethanol, but no acid leaching was applied. Values were duplicated and are reported relative to SMOW. Limitations of the dataset are connected to the small sample sizes, which precluded radiogenic isotope analyses for more than four of the samples.
Contact Email
dorrit.jacob@anu.edu.au
Contact Address
Research School of Earth Sciences, The Australian National University, 142 Mills Road, Canberra, 2600, Australia
Contact Phone Number
+61 2 6125 2487
Principal Investigator
Dorrit Jacob
Collaborators
Agnes Fung
Fields of Research
370302 - Inorganic geochemistry;
370503 - Igneous and metamorphic petrology
Socio-Economic Objective
280107 - Expanding knowledge in the earth sciences
Keywords
Lac de Gras;
xenolith;
diamond;
LA-ICPMS
Type of Research Activity
Pure basic research
Date of data creation
2023
Year of data publication
2024
Creator(s) for Citation
Jacob
Dorrit
Fung
Agnes
Publisher for Citation
The Australian National University Data Commons
Publications
10.1002/gdj3.258
Jacob, D.E. & Fung, A. (2024) Geochemistry of forty-one
eclogitic and pyroxenitic mantle xenoliths from the Central Slave Craton, Canada (Ekati Diamond Mine). Geoscience Data Journal, 11, 825–832. Available from: https://doi.org/10.1002/gdj3.258
Geochemistry of forty-one
eclogitic and pyroxenitic mantle xenoliths from the Central Slave Craton, Canada (Ekati Diamond Mine)
Access Rights
Open Access
Access Rights Type
Open
Rights held in and over the data
Creative Commons Licence (CC BY-NC) is assigned to this data.
Licence Type
CC-BY-NC - Attribution-NonCommercial (Version 4.0)
Retention Period
Indefinitely
Data Size
119 MB
Data Management Plan
No
Status: Published
Published to:
Published to:
- Australian National University
- Australian National Data Service
Related items
- hasAssociationWith:
Prof. Dorrit Jacob [anudc:6265]