Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis
<p>Interpreting the ages of supergene mineralogical phases in laterite is complex because they consist of polycrystalline mixtures of different phases at the microscopic scale that could be crystalized at different epochs. Among the geochronometers, the <span class="inline-formula"...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-06-01
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| Series: | European Journal of Mineralogy |
| Online Access: | https://ejm.copernicus.org/articles/35/383/2023/ejm-35-383-2023.pdf |
| _version_ | 1797804315710062592 |
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| author | K. P. P. Marques K. P. P. Marques T. Allard C. Gautheron B. Baptiste R. Pinna-Jamme G. Morin L. Delbes P. Vidal-Torrado |
| author_facet | K. P. P. Marques K. P. P. Marques T. Allard C. Gautheron B. Baptiste R. Pinna-Jamme G. Morin L. Delbes P. Vidal-Torrado |
| author_sort | K. P. P. Marques |
| collection | DOAJ |
| description | <p>Interpreting the ages of supergene mineralogical phases in
laterite is complex because they consist of polycrystalline mixtures of
different phases at the microscopic scale that could be crystalized at
different epochs. Among the geochronometers, the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="f4b2fa0b999292f48cb1b1e04a07aa2a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00003.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00003.png"/></svg:svg></span></span> method on
hematite and goethite is more often used, but ages can be difficult to interpret
due to phases mixing. To resolve this issue, this study proposes a
methodology for performing detailed mineralogical analysis of hematite and
goethite single grains prior to their dating using the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="26d53101b6c836ab0b6ef325d9bca65f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00004.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00004.png"/></svg:svg></span></span> method.
Strictly non-destructive mineralogy of single grains is not achievable by
classical tools, such as conventional powder XRD (X-ray diffraction; requiring at least some milligrams
of powder) or SEM (scanning electron microscopy; that can contaminate the grain by coating or fixing).
Therefore, we performed X-ray diffraction patterns of single grains using
high-flux X-ray beams from both a rotating anode (XRD_rotat)
laboratory diffractometer and a synchrotron beamline (XRD_synch) and compared the results in order to design a method based on
XRD_rotat only. For this purpose, two samples from the
pisolitic facies of a Brazilian ferruginous duricrust (Alto Paranaíba
region, Minas Gerais State, Brazil) were chosen because they presented a
usual heterogeneity. Rietveld refinements of the XRD patterns obtained from
both XRD_rotat and XRD_synch yielded similar
results for the weight percentage ratio of the main phases and mean coherent domain
sizes and less similar results for Al substitution rates, thus validating the
XRD_rotat approach. No beam damage was observed when
increasing X-ray exposure time, neither on XRD patterns nor on <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="c9cf0718e10396f6e2182a01dacbca3e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00005.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00005.png"/></svg:svg></span></span> ages. Hence, sub-millimeter, undisturbed grains can be used to analyze the
mineralogy of ferruginous duricrusts by XRD_rotat with a
short exposure, and the same grains can subsequently be dated by <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="1b812d81e06111d524c50b551af57291"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00006.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00006.png"/></svg:svg></span></span> geochronology analysis. The <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="9d21999f80ac3e5cb55b34a6e125d8e4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00007.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00007.png"/></svg:svg></span></span> dating of pisolitic core and cortex
grains also provided meaningful ages: they revealed two evolution phases of
the ferruginous duricrust, which occurred at or before the Oligocene for
the pisolitic core and middle Miocene for the pisolitic cortex, agreeing with the
previous model for the development of pisolites. The mineralogy of single
grains selected for dating is helpful for discussing the crystallization
ages, and the high-flux XRD approach may be applied to other supergene
mineral parageneses used for absolute dating.</p> |
| first_indexed | 2024-03-13T05:34:18Z |
| format | Article |
| id | doaj.art-2f3a972d248b4db0aeec9185d7e1fac1 |
| institution | Directory Open Access Journal |
| issn | 0935-1221 1617-4011 |
| language | English |
| last_indexed | 2024-03-13T05:34:18Z |
| publishDate | 2023-06-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | European Journal of Mineralogy |
| spelling | doaj.art-2f3a972d248b4db0aeec9185d7e1fac12023-06-14T10:17:12ZengCopernicus PublicationsEuropean Journal of Mineralogy0935-12211617-40112023-06-013538339510.5194/ejm-35-383-2023Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysisK. P. P. Marques0K. P. P. Marques1T. Allard2C. Gautheron3B. Baptiste4R. Pinna-Jamme5G. Morin6L. Delbes7P. Vidal-Torrado8“Luiz de Queiroz” College of Agriculture, University of São Paulo, 13418-900, Piracicaba, São Paulo, BrazilInstitut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Sorbonne Université, IRD, MNHN, 75252, Paris CEDEX 05, FranceInstitut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Sorbonne Université, IRD, MNHN, 75252, Paris CEDEX 05, FranceUniversité Paris-Saclay, CNRS, GEOPS, 91405, Orsay, FranceInstitut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Sorbonne Université, IRD, MNHN, 75252, Paris CEDEX 05, FranceUniversité Paris-Saclay, CNRS, GEOPS, 91405, Orsay, FranceInstitut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Sorbonne Université, IRD, MNHN, 75252, Paris CEDEX 05, FranceInstitut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR CNRS 7590, Sorbonne Université, IRD, MNHN, 75252, Paris CEDEX 05, France“Luiz de Queiroz” College of Agriculture, University of São Paulo, 13418-900, Piracicaba, São Paulo, Brazil<p>Interpreting the ages of supergene mineralogical phases in laterite is complex because they consist of polycrystalline mixtures of different phases at the microscopic scale that could be crystalized at different epochs. Among the geochronometers, the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="f4b2fa0b999292f48cb1b1e04a07aa2a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00003.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00003.png"/></svg:svg></span></span> method on hematite and goethite is more often used, but ages can be difficult to interpret due to phases mixing. To resolve this issue, this study proposes a methodology for performing detailed mineralogical analysis of hematite and goethite single grains prior to their dating using the <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="26d53101b6c836ab0b6ef325d9bca65f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00004.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00004.png"/></svg:svg></span></span> method. Strictly non-destructive mineralogy of single grains is not achievable by classical tools, such as conventional powder XRD (X-ray diffraction; requiring at least some milligrams of powder) or SEM (scanning electron microscopy; that can contaminate the grain by coating or fixing). Therefore, we performed X-ray diffraction patterns of single grains using high-flux X-ray beams from both a rotating anode (XRD_rotat) laboratory diffractometer and a synchrotron beamline (XRD_synch) and compared the results in order to design a method based on XRD_rotat only. For this purpose, two samples from the pisolitic facies of a Brazilian ferruginous duricrust (Alto Paranaíba region, Minas Gerais State, Brazil) were chosen because they presented a usual heterogeneity. Rietveld refinements of the XRD patterns obtained from both XRD_rotat and XRD_synch yielded similar results for the weight percentage ratio of the main phases and mean coherent domain sizes and less similar results for Al substitution rates, thus validating the XRD_rotat approach. No beam damage was observed when increasing X-ray exposure time, neither on XRD patterns nor on <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="c9cf0718e10396f6e2182a01dacbca3e"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00005.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00005.png"/></svg:svg></span></span> ages. Hence, sub-millimeter, undisturbed grains can be used to analyze the mineralogy of ferruginous duricrusts by XRD_rotat with a short exposure, and the same grains can subsequently be dated by <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="1b812d81e06111d524c50b551af57291"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00006.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00006.png"/></svg:svg></span></span> geochronology analysis. The <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mo>(</mo><mi mathvariant="normal">U</mi><mo>-</mo><mi mathvariant="normal">Th</mi><mo>)</mo><mo>/</mo><mi mathvariant="normal">He</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="9d21999f80ac3e5cb55b34a6e125d8e4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-35-383-2023-ie00007.svg" width="58pt" height="14pt" src="ejm-35-383-2023-ie00007.png"/></svg:svg></span></span> dating of pisolitic core and cortex grains also provided meaningful ages: they revealed two evolution phases of the ferruginous duricrust, which occurred at or before the Oligocene for the pisolitic core and middle Miocene for the pisolitic cortex, agreeing with the previous model for the development of pisolites. The mineralogy of single grains selected for dating is helpful for discussing the crystallization ages, and the high-flux XRD approach may be applied to other supergene mineral parageneses used for absolute dating.</p>https://ejm.copernicus.org/articles/35/383/2023/ejm-35-383-2023.pdf |
| spellingShingle | K. P. P. Marques K. P. P. Marques T. Allard C. Gautheron B. Baptiste R. Pinna-Jamme G. Morin L. Delbes P. Vidal-Torrado Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis European Journal of Mineralogy |
| title | Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis |
| title_full | Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis |
| title_fullStr | Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis |
| title_full_unstemmed | Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis |
| title_short | Supergene phases from ferruginous duricrusts: non-destructive microsampling and mineralogy prior to (U–Th) ∕ He geochronological analysis |
| title_sort | supergene phases from ferruginous duricrusts non destructive microsampling and mineralogy prior to u th he geochronological analysis |
| url | https://ejm.copernicus.org/articles/35/383/2023/ejm-35-383-2023.pdf |
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