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Econ. Environ. Geol. 2023; 56(6): 817-830

Published online December 29, 2023

https://doi.org/10.9719/EEG.2023.56.6.817

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Alice Springs Orogeny (ASO) Footprints Tracing in Fresh Rocks in Arunta Region, Central Australia, Using Uranium/Lead (U-Pb) Geochronology

Kouame Yao1, Mohammed O. Idrees2,3,*, Abdul-Lateef Balogun4, Mohamed Barakat A. Gibril5

1Macquarie University, Department of Earth and Planetary Sciences, Faculty of Science and Engineering, North Ryde, Australia
2Department of Surveying and Geoinformatics, Faculty of Environmental Sciences, University of Abuja, P.M.B. 117, Abuja, Nigeria
3Department of Surveying and Geoinformatics, Faculty of Environmental Sciences, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria
4Environmental Systems Research Institute (ESRI), Melbourne, Australia
5GIS and Remote Sensing Center, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah 27272, United Arab Emirates

Correspondence to : *dare.idrees@gmail.com, mohammed.idrees@uniabuja.edu.ng

Received: March 13, 2023; Revised: November 4, 2023; Accepted: November 7, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

This study investigates the age of the surficial rocks in the Arunta region using Uranium-Lead (U-Pb) geochronological dating. Rock samples were collected at four locations, Cattle-Water Pass (CP 1610), Gough Dam (GD 1622 and GD 1610), and London-Eye (LE 1601), within the Strangways Metamorphic Complex and crushed by selFragging. Subsequently, the zircon grains were imaged using Cathodoluminescence (CL) analysis and the U-Pb (uranium and lead) isotope ratios and the chrono-stratigraphy were measured. The imaged zircon revealed an anomalous heterogeneous crystal structure. Ellipses of the samples at locations GD1601, CP1610, and GD1622 fall below the intercept indicating the ages produced discordant patterns, whereas LE1601 intersects the Concordia curve at two points, implying the occurrence of an event of significant impact. For the rock sample at CP1610, the estimated mean age is 1742.2 ± 9.2 Ma with mean squared weighted deviation (MSWD) = 0.49 and probability of equivalence of 0.90; 1748 ± 15 Ma - MSWD = 1.02 and probability of equivalence of 0.40 for GD1622; and 1784.4 ± 9.1 Ma with MSWD of 1.09 and probability of equivalence of 0.37 for LE1601. But for samples at GD1601, two different age groups with different means occurred: 1) below the global mean (1792.2 ± 32 Ma) estimated at 1738.2 ± 14 Ma with MSWD of 0.109 and probability of equivalence of 0.95 and 2) above it with mean of 1838.22 ± 14 Ma, MSWD of 1.6 and probability of equivalence of 0.95. Analysis of the zircon grains has shown a discrepancy in the age range between 1700 Ma and 1800 Ma compared to the ASO dated to have occurred between 440 and 300 Ma. Moreover, apparent similarity in age of the core and rim means that the mineral crystallized relatively quickly without significant interruptions and effect on the isotopic system. This may have constraint the timing and extent of geological events that might have affected the mineral, such as metamorphism or hydrothermal alteration.

Keywords geology, rock dating, selFragging, lead loss, Cathodoluminescence imaging

Article

Research Paper

Econ. Environ. Geol. 2023; 56(6): 817-830

Published online December 29, 2023 https://doi.org/10.9719/EEG.2023.56.6.817

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Alice Springs Orogeny (ASO) Footprints Tracing in Fresh Rocks in Arunta Region, Central Australia, Using Uranium/Lead (U-Pb) Geochronology

Kouame Yao1, Mohammed O. Idrees2,3,*, Abdul-Lateef Balogun4, Mohamed Barakat A. Gibril5

1Macquarie University, Department of Earth and Planetary Sciences, Faculty of Science and Engineering, North Ryde, Australia
2Department of Surveying and Geoinformatics, Faculty of Environmental Sciences, University of Abuja, P.M.B. 117, Abuja, Nigeria
3Department of Surveying and Geoinformatics, Faculty of Environmental Sciences, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria
4Environmental Systems Research Institute (ESRI), Melbourne, Australia
5GIS and Remote Sensing Center, Research Institute of Sciences and Engineering, University of Sharjah, Sharjah 27272, United Arab Emirates

Correspondence to:*dare.idrees@gmail.com, mohammed.idrees@uniabuja.edu.ng

Received: March 13, 2023; Revised: November 4, 2023; Accepted: November 7, 2023

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided original work is properly cited.

Abstract

This study investigates the age of the surficial rocks in the Arunta region using Uranium-Lead (U-Pb) geochronological dating. Rock samples were collected at four locations, Cattle-Water Pass (CP 1610), Gough Dam (GD 1622 and GD 1610), and London-Eye (LE 1601), within the Strangways Metamorphic Complex and crushed by selFragging. Subsequently, the zircon grains were imaged using Cathodoluminescence (CL) analysis and the U-Pb (uranium and lead) isotope ratios and the chrono-stratigraphy were measured. The imaged zircon revealed an anomalous heterogeneous crystal structure. Ellipses of the samples at locations GD1601, CP1610, and GD1622 fall below the intercept indicating the ages produced discordant patterns, whereas LE1601 intersects the Concordia curve at two points, implying the occurrence of an event of significant impact. For the rock sample at CP1610, the estimated mean age is 1742.2 ± 9.2 Ma with mean squared weighted deviation (MSWD) = 0.49 and probability of equivalence of 0.90; 1748 ± 15 Ma - MSWD = 1.02 and probability of equivalence of 0.40 for GD1622; and 1784.4 ± 9.1 Ma with MSWD of 1.09 and probability of equivalence of 0.37 for LE1601. But for samples at GD1601, two different age groups with different means occurred: 1) below the global mean (1792.2 ± 32 Ma) estimated at 1738.2 ± 14 Ma with MSWD of 0.109 and probability of equivalence of 0.95 and 2) above it with mean of 1838.22 ± 14 Ma, MSWD of 1.6 and probability of equivalence of 0.95. Analysis of the zircon grains has shown a discrepancy in the age range between 1700 Ma and 1800 Ma compared to the ASO dated to have occurred between 440 and 300 Ma. Moreover, apparent similarity in age of the core and rim means that the mineral crystallized relatively quickly without significant interruptions and effect on the isotopic system. This may have constraint the timing and extent of geological events that might have affected the mineral, such as metamorphism or hydrothermal alteration.

Keywords geology, rock dating, selFragging, lead loss, Cathodoluminescence imaging

    Fig 1.

    Figure 1.The study area. (a) Map of Australia highlighting the location of the site in the central Arunta, south of the Northern Region (b) the Strangways Metamorphic Complex (SMC) where the samples were collected, and (c) geological map of the Arunta block showing the metamorphic and igneous rock types.
    Economic and Environmental Geology 2023; 56: 817-830https://doi.org/10.9719/EEG.2023.56.6.817

    Fig 2.

    Figure 2.Rock samples collected at Location A - (a) Igneous rocks with mainly quartz and feldspar from Cattle Water Pass (CP 1610) close to the Cattle Water Shear Zone (CPSZ), (b) Garnet granite invaded igneous dyke form London Eye (LE 1601); and at Location B – (c) Strained Felsic igneous rock from Gough Dam (GD 1622) and (d) Coarse crystalline igneous rocks from (GD 1610) within the, Shear Zone (GDSZ).
    Economic and Environmental Geology 2023; 56: 817-830https://doi.org/10.9719/EEG.2023.56.6.817

    Fig 3.

    Figure 3.Flowchart for Zircon Geochronology dating.
    Economic and Environmental Geology 2023; 56: 817-830https://doi.org/10.9719/EEG.2023.56.6.817

    Fig 4.

    Figure 4.core-rim structure of the imaged zircon - the inner and outer circles are the core and rim, respectively.
    Economic and Environmental Geology 2023; 56: 817-830https://doi.org/10.9719/EEG.2023.56.6.817

    Fig 5.

    Figure 5.Concordia Plot of zircon grain age intercept of ratios (207Pb / 206Pb) for the sample at (a) CP1610, (b) GD1601, and (c) GD1622 with mean squared weighted deviation (MSWD) of 0.61, 2.1, and 1.6, respectively and (d) LE1601. Except for LE1601 which shows the possible occurrence of an episodic Lead (Pb) loss event of significance that might have affected the zircon grains, all the plots fall below the concordant age curve indicating a discordant age pattern.
    Economic and Environmental Geology 2023; 56: 817-830https://doi.org/10.9719/EEG.2023.56.6.817

    Fig 6.

    Figure 6.Plot of the Mean age of the zircon grains at 95% confidence limit for sample at locations: (a) CP1610 - estimated at 1742.2 ± 9.2 Ma - MSWD = 0.49; probability of equivalence = 0.90; (b) Non-representative mean age of zircon grains: non-representative mean age of sample # GD1601 estimated at 1792 Ma, with 4 and 5 age groups below (b1) and above (b2) the mean, with sub-Mean age =1738 ± 14 Ma, MSWD = 0.109, probability of equivalence = 0.95 and sub- Mean and Mean age = 1838 ± 14 Ma; MSWD = 1.6; probability of equivalence = 0.95, respectively; (c) GD1622 - estimated at 1748 ± 15 Ma - MSWD = 1.02; probability of equivalence = 0.40; and (d) LE1601 with estimated mean age = 1784 ± 9.1 Ma - MSWD = 1.09; probability of equivalence = 0.37.
    Economic and Environmental Geology 2023; 56: 817-830https://doi.org/10.9719/EEG.2023.56.6.817

    Fig 7.

    Figure 7.Schematic sketches of zircon U-Pb age distribution at scale 20 μm indicating the zircon core–rim proportion types and internal rim textures of grain sample from (a) CP 1610, (b) LE1601, (c) GD 1601 and (d) GD 1622. Note that P denote Point; R - Rim, and C – Core.
    Economic and Environmental Geology 2023; 56: 817-830https://doi.org/10.9719/EEG.2023.56.6.817

    Summary of the estimated age of the grain samples at the four locations.


    Rock SampleAGEMSWDProbability of equivalence
    # CP1610Mean1742.2 ± 9.2 Ma0.490.90
    # GD1601Above mean1838 ± 14 Ma1.60.95
    Mean1792 ± 32 Ma--
    Below mean1738 ± 14 Ma0.1090.95
    # LE1601Mean1784.4 ± 9.1 Ma1.090.37
    # GD1622Mean1738.2 ± 15 Ma0.1090.95

    KSEEG
    Apr 30, 2024 Vol.57 No.2, pp. 107~280

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