Resolving poly-metamorphic Paleoarchean ages by chemical dating of monazites using multi-spectrometer U, Th and Pb analyses and sub-counting methodology

Prabhakar, N.

doi:10.1016/j.chemgeo.2013.04.012

Cited by 47 publications

(35 citation statements)

References 53 publications

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“…PbMa, ThMa, and UMb spectral lines were calibrated with crocoite (PbCrO 4 ), Th glass (ThO 2 -5 wt.%), and U glass (UO2-5 wt.%) standards and simultaneously analyzed in two spectrometers for 240, 160, and 160 s, respectively, using subcounting methodology (cf. Prabhakar, 2013;Spear & Wark, 2009). The total counts of PbMa were acquired in the exponential mode to better define the distantly located background positions (Gonçalves et al, 2016;Jercinovic & Williams, 2005;Jercinovic et al, 2008;Spear & Wark, 2009).…”

Section: Th-u Total Pb Monazite Geochronologymentioning

confidence: 99%

“…The significant peak interference of ThM2-O4, ThMζ1, ThMζ2, YLC2, YLC3, and LaLa on PbMa and ThMc and ThM3-N4 on UMb was corrected during quantification following the values given in Table S1. More details on monazite dating protocol and interference corrections were outlined in Pant et al (2009), Prabhakar (2013, Deshmukh et al (2017), Chatterjee et al (2017), and Pandey et al (2019). By applying these conditions, detection limit was achieved as 100 ppm for Th, 110 ppm for U, and 80 ppm for Pb.…”

Section: Th-u Total Pb Monazite Geochronologymentioning

confidence: 99%

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Dynamics, EPMA Th‐U‐Total Pb Monazite Geochronology and Tectonic Implications of Deformational Fabric in the Lower‐Middle Crustal Rocks: A Case Study of Ambaji Granulite, NW India

Tiwari

Biswal

2019

Tectonics

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Strain fabric and monazite microstructure were studied and dated by Electron Probe Microanalyser (EPMA) in situ Th‐U‐total Pb monazite geochronology in the Ambaji granulite, South Delhi terrane, NW India. The Ambaji granulite comprises pelitic, calcareous, and mafic granulites with several phases of granite intrusions, G0‐3. The granulites were deformed by three phases of folding, F1–3, during South De lhi orogeny and marked by a subhorizontal pervasive fabric, S1, axial planar to isoclinal‐recumbent F1 folds that developed during granulite facies metamorphism. S1 is overprinted by discrete sets of subvertical shear zones associated with a mylonitic fabric, S2, that were developed axial planar to NE‐SW striking upright F2 folds and facilitated exhumation of granulite facies rocks to the upper crust. The shear zones show early history of high‐temperature thrust sense shear and late stage low‐temperature sinistral shear. The NW‐SE striking F3 folds also affected the granulite facies rocks resulting in interference patterns and variations in regional structural trends. Brittle strike slip, and normal fault (Sf fabric) that developed post F3, led the final exhumation of the granulite facies rocks to the surface. The S1 monazites are Y‐depleted and recrystallized through dislocation creep, and the S2‐Sf monazites are Y‐enriched and recrystallized through dissolution‐precipitation creep. Different monazite population yielded distinct ages of circa 875‐857, 834‐778, and 764‐650 Ma for S1, S2, and Sf strain, respectively, indicating that the South Delhi orogeny spanned 875‐650 Ma overlapping with the early phase of the Pan‐African orogeny or representing a transition between Grenvillian and Pan‐African orogeny.

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Section: Th-u Total Pb Monazite Geochronologymentioning

confidence: 99%

Section: Th-u Total Pb Monazite Geochronologymentioning

confidence: 99%

Dynamics, EPMA Th‐U‐Total Pb Monazite Geochronology and Tectonic Implications of Deformational Fabric in the Lower‐Middle Crustal Rocks: A Case Study of Ambaji Granulite, NW India

Tiwari

Biswal

2019

Tectonics

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“…in the Singhbhum Craton (Basu et al, 1996;Sharma et al, 1994;Mishra et al, 1999;Prabhakar, 2013;Prabhakar and Bhattacharya, 2013), and in the Meso/Early Neoproterozoic crustal domains of NSMB and CGC (Fig. 14).…”

mentioning

confidence: 92%

“…The 2σ error of spot ages in the analyzed monazites varies between 2 and 10% of the absolute age (cf. Prabhakar, 2013) Mojzsis et al (2003). The zircon age standard AS3 (1099 ± 1 Ma, Paces and Miller, 1993) was used for age calibrations ( Table 1).…”

mentioning

confidence: 99%

“…The operating conditions using SX-100, the analytical protocol, and the data reduction methodology are adopted from Prabhakar (2013). For spot age determination, monazite grains larger than 5μm diameter were chosen to eliminate effects induced by grain boundary defects in smaller grains; also, monazite grains with at least 3.5 wt% ThO 2 were analyzed because at lower ThO 2 abundances the 2σ error on spot age increases dramatically (Prabhakar, 2013). The 2σ error of spot ages in the analyzed monazites varies between 2 and 10% of the absolute age (cf.…”

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confidence: 99%

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Restoration of Late Neoarchean–Early Cambrian tectonics in the Rengali orogen and its environs (eastern India): The Antarctic connection

Bhattacharya

Das

Bell

et al. 2016

Lithos

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Ti‐in‐zircon and Ti‐in‐quartz thermometry using electron probe microanalysis: A promising approach in retrieving thermal conditions of granulite facies metamorphism and felsic magmatism in the Sandmata Complex, Aravalli Craton (NW India)

2023

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The titanium (Ti) concentrations in zircon and quartz and corresponding thermometers have been regarded as powerful monitors that constrain petrogenetically meaningful temperature conditions of crystallization and metamorphism. The precise measurement of trace elements by electron probe microanalyzer (EPMA) is quite challenging as their x‐ray intensities are only slightly higher than the Bremsstrahlung background, leading to significant errors while quantifying the elemental abundances (e.g., Ti‐in‐zircon). We present EPMA‐based protocols for analysing Ti concentrations in zircon and quartz by considering recent analytical and instrumental improvements. High counting times at peak and background positions, simultaneous acquisition of Ti in multiple (three) spectrometers and data processing using the non‐central chi2 test for risk determination in sub‐counting method were employed in Ti‐in‐zircon and Ti‐in‐quartz protocols. Applying these protocols to the Mongolian garnet, San Carlos olivine and NIST 610 glass standards yielded Ti concentrations of 0.60 ± 0.02 wt%, 18 ± 3 ppm and 437 ± 26 ppm (in ±2σ), respectively. The Ti concentrations obtained from these standards are consistent with those published based on high‐precision analytical methods. We use the existing Ti‐in‐zircon and Ti‐in‐quartz thermometers to understand the thermal evolution of various lithologies in the Sandmata Complex, Aravalli Craton (north‐western India). The investigated samples include garnet–biotite gneiss, migmatite gneiss, mafic granulite and Anjana granite. The Ti‐in‐zircon temperatures calculated from the patchy‐zoned zircon cores yield HT–UHT conditions (892–959°C) for garnetiferous granite gneiss, migmatite gneiss and mafic granulite, whereas the zircon overgrowths yield temperatures of 725–871°C. The homogeneous zircon cores from Anjana granite yield temperatures (914–984°C) comparable to zirconium saturation conditions (920–960°C), indicating zircon crystallization from “hot” granitic melt. The oscillatory overgrowths on the zircon core obtain variable temperature conditions for inner overgrowth (811–877°C) and outer overgrowth (714–782°C), suggesting the episodic growth of zircon grains from different magma pulses. Additionally, the application of pressure‐dependent Ti‐in‐quartz thermometry yields quartz recrystallization conditions for garnet–biotite gneiss (430–556°C), migmatite gneiss (423–593°C), mafic granulite (430–679°C) and Anjana Granite (444–533°C). The combination of Ti‐in‐zircon thermometry, Ti‐in‐quartz and conventional thermobarometry demonstrates cooling histories for various high‐grade metamorphic and magmatic rocks in the Sandmata Complex. Based on this study, we emphasize that trace element thermometers can decipher high‐temperature metamorphism, which is otherwise erased in conventional thermometers due to diffusional readjustments during long‐lasting near‐peak and post‐peak metamorphism.

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Resolving poly-metamorphic Paleoarchean ages by chemical dating of monazites using multi-spectrometer U, Th and Pb analyses and sub-counting methodology

Cited by 47 publications

References 53 publications

Dynamics, EPMA Th‐U‐Total Pb Monazite Geochronology and Tectonic Implications of Deformational Fabric in the Lower‐Middle Crustal Rocks: A Case Study of Ambaji Granulite, NW India

Dynamics, EPMA Th‐U‐Total Pb Monazite Geochronology and Tectonic Implications of Deformational Fabric in the Lower‐Middle Crustal Rocks: A Case Study of Ambaji Granulite, NW India

Restoration of Late Neoarchean–Early Cambrian tectonics in the Rengali orogen and its environs (eastern India): The Antarctic connection

Ti‐in‐zircon and Ti‐in‐quartz thermometry using electron probe microanalysis: A promising approach in retrieving thermal conditions of granulite facies metamorphism and felsic magmatism in the Sandmata Complex, Aravalli Craton (NW India)

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