Dating mylonitic overprinting of ancient rocks

Kirkland, Christopher L.; Olierook, Hugo K.H.; Danišík, Martin; Liebmann, Janne; Hollis, Julie; Ribeiro, Bruno Vieira; Rankenburg, Kai

doi:10.1038/s43247-023-00709-5

Cited by 8 publications

(4 citation statements)

References 72 publications

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“…Rubidium-Strontium (Rb-Sr) geochronology using laser ablation -inductively coupled plasmatandem mass spectrometry (LA-ICP-MS/MS) has become a popular method to constrain the formation or cooling age of potassium-bearing minerals (Gorojovsky and Alard, 2020;Hogmalm et al, 2017;Jegal et al, 2022;Kirkland et al, 2023;Larson et al, 2023;Laureijs et al, 2021; Li specialized laboratories, the laser-ablation method allows rapid acquisition of Rb-Sr dates directly from thin sections or rock blocks with minimal sample preparation. The method involves the use of an ICP-MS/MS, equipped with a reaction cell where isobaric isotopes can be chemically separated due to their significant differences in reactivity with an introduced reaction gas (Balcaen et al, 2015 and references therein).…”

Section: Introductionmentioning

confidence: 99%

Calibration methods for laser ablation Rb–Sr geochronology: comparisons and recommendation based on NIST glass and natural reference materials

Glorie,

Gilbert,

Hand

et al. 2023

Preprint

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Abstract. In-situ Rb–Sr geochronology using LA-ICP-MS/MS technology allows rapid dating of K-rich minerals such as micas (e.g. biotite, muscovite, phlogopite) and K-feldspar. While many studies have demonstrated the ability of the method, analytical protocols vary significantly and to date no studies have provided an in-depth comparison and synthesis in terms of precision and accuracy. Here we compare four calibration protocols based on commonly used reference materials for Rb–Sr dating. We demonstrate that downhole fractionation trends (DHF) for natural biotite, K-feldspar and phlogopite contrast with that for the commonly used Mica-Mg nano-powder reference material. Consequently, Rb–Sr dates calibrated to Mica-Mg can be up to 5 % inaccurate and the degree of inaccuracy appears to be unsystematic between analytical sessions. Calibrating to Mica-Mg also introduces excess uncertainty that can be avoided with a more consistent primary calibration material. We propose a calibration approach involving NIST-610 glass as the primary reference material (RM) and a natural mineral with similar DHF characteristics to the analysed samples as secondary RM to correct for matrix-dependent fractionation. In this work, MDC phlogopite (the source mineral for Mica-Mg nano-powder) was used as the secondary RM, consistently producing accurate Rb–Sr dates for a series of natural biotites and K-feldspars with well-characterized expected ages. However, biotite from the Banalasta Adamellite, Taratap Granodiorite and Entire Creek pegmatite are also suitable secondary RMs for Rb/Sr ratio calibration purposes with consistently <1.5 % fully propagated uncertainties in our methodological approach. Until calibration using isochronous natural standards as the primary RM becomes possible in data-reduction software, the two-step calibration approach described here is recommended.

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Section: Introductionmentioning

confidence: 99%

Calibration methods for laser ablation Rb–Sr geochronology: comparisons and recommendation based on NIST glass and natural reference materials

Glorie,

Gilbert,

Hand

et al. 2023

Preprint

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“…Metamorphic recrystallization is also evidenced from the textures (Figures 2 and 3). In the case of the meta-carbonates, we were not able to date sulfides, but the Rb-Sr ages of the mica (Figure 8d) agree with the Proterozoic ages of shear zones in the Mesoarchean Akia terrane of Greenland (Kirkland et al, 2023). This opens the possibility of metasomatic alteration associated with shearing at a post-Archean time.…”

Section: Evidence and Effects Of Metamorphism And Alterationmentioning

confidence: 80%

“…Nearby indicating a shearing event and possibly metasomatic alteration at that time (cf. Kirkland et al, 2023). Hence it is conceivable that the meta-sedimentary rocks initially contained a large MIF signal that was perhaps reduced in magnitude by magmatic hydrothermal overprinting.…”

Section: Con Clus I On and Impli C Ati On Smentioning

confidence: 99%

Evaluating the multiple sulfur isotope signature of Eoarchean rocks from the Isua Supracrustal Belt (Southwest‐Greenland) by MC‐ICP‐MS: Volcanic nutrient sources for early life

Macdonald,

Sugden,

Dumont

et al. 2024

Geobiology

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On the anoxic Archean Earth, prior to the onset of oxidative weathering, electron acceptors were relatively scarce, perhaps limiting microbial productivity. An important metabolite may have been sulfate produced during the photolysis of volcanogenic SO2 gas. Multiple sulfur isotope data can be used to track this sulfur source, and indeed this record indicates SO2 photolysis dating back to at least 3.7 Ga, that is, as far back as proposed evidence of life on Earth. However, measurements of multiple sulfur isotopes in some key strata from that time can be challenging due to low sulfur concentrations. Some studies have overcome this challenge with NanoSIMS or optimized gas‐source mass spectrometry techniques, but those instruments are not readily accessible. Here, we applied an aqua regia leaching protocol to extract small amounts of sulfur from whole rocks for analyses of multiple sulfur isotopes by multi‐collector inductively coupled plasma mass spectrometry (MC‐ICP‐MS). Measurements of standards and replicates demonstrate good precision and accuracy. We applied this technique to meta‐sedimentary rocks with putative biosignatures from the Eoarchean Isua Supracrustal Belt (ISB, >3.7 Ga) and found positive ∆33S (1.40–1.80‰) in four meta‐turbidites and negative ∆33S (−0.80‰ and −0.66‰) in two meta‐carbonates. Two meta‐basalts do not display significant mass‐independent fractionation (MIF, −0.01‰ and 0.16‰). In situ Re–Os dating on a molybdenite vein hosted in the meta‐turbidites identifies an early ca. 3.7 Ga hydrothermal phase, and in situ Rb–Sr dating of micas in the meta‐carbonates suggests metamorphism affected the rocks at ca. 2.2 and 1.7 Ga. We discuss alteration mechanisms and conclude that there is most likely a primary MIF‐bearing phase in these meta‐sediments. Our new method is therefore a useful addition to the geochemical toolbox, and it confirms that organisms at that time, if present, may indeed have been fed by volcanic nutrients.

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“…In this context, faults can be characterised by the superposition of deformation events from the ductile to the brittle regime (e.g. Mitra, 1984;Holm et al, 1989;Gueydan et al, 2005;Fusseis and Handy, 2008;Rolland et al, 2009;Fossen 30 and Cavalcante, 2017;Fossen et al, 2019;Perret et al, 2020;Kirkland et al, 2023). These fault zones typically have important associated fractures that allow channelized fluid circulation.…”

Section: Introductionmentioning

confidence: 99%

Evolution of fluid redox in a fault zone of the Pic de Port-Vieux thrust in the Pyrenees Axial Zone (Spain)

Charpentier,

Milesi,

Labaume

et al. 2024

Preprint

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Abstract. In mountain ranges, crustal-scale faults localize multiple episodes of deformation. It is therefore common to observe current or past geothermal systems along these structures. Understanding the fluid circulation channelized in fault zones is essential to characterize the thermo-chemical evolution of associated hydrothermal systems. We present a study of a paleo-system of the Pic de Port-Vieux thrust fault. This fault is a second-order thrust associated with the Gavarnie thrust in the Axial Zone of the Pyrenees. The study focused on phyllosilicates, which permit to constrain the evolution of temperature and redox of fluids at the scale of the fault system. Combined X-ray absorption near-edge structure (XANES) spectroscopy and electron probe microanalysis (EPMA) on synkinematic chlorite, closely linked to microstructural observations were performed in both the core and damage zones of the fault zone. Regardless of their microstructural position, chlorite from the damage zone contains iron and magnesium (Fetotal/(Fetotal+Mg) about 0.4), with Fe3+ accounting for about 30 % of the total iron. Chlorite in the core zone is enriched in total iron, but individual Fe3+/Fetotal ratios range from 15 % to 40 % depending on the microstructural position of the grain. Homogeneous temperature conditions about 300 °C have been obtained by chlorite thermometry. A scenario is proposed for the evolution of fluid-rock interaction conditions at the scale of the fault zone. It involves the circulation of a single hydrothermal fluid with homogeneous temperature but several redox properties. A highly reducing fluid evolves due to redox reactions involving progressive dissolution of hematite, accompanied by crystallization of Fe2+-rich and Fe3+-rich chlorite in the core zone.

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Dating mylonitic overprinting of ancient rocks

Cited by 8 publications

References 72 publications

Calibration methods for laser ablation Rb–Sr geochronology: comparisons and recommendation based on NIST glass and natural reference materials

Calibration methods for laser ablation Rb–Sr geochronology: comparisons and recommendation based on NIST glass and natural reference materials

Evaluating the multiple sulfur isotope signature of Eoarchean rocks from the Isua Supracrustal Belt (Southwest‐Greenland) by MC‐ICP‐MS: Volcanic nutrient sources for early life

Evolution of fluid redox in a fault zone of the Pic de Port-Vieux thrust in the Pyrenees Axial Zone (Spain)

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