Chemical Th–U–total Pb dating by electron microprobe analysis of monazite, xenotime and zircon from the Archean Napier Complex, East Antarctica: evidence for ultra-high-temperature metamorphism at 2400 Ma

Asami, Masao; Suzuki, Koji; Grew, Edward S.

doi:10.1016/s0301-9268(01)00228-5

Cited by 84 publications

(27 citation statements)

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“…The age of satellite dikes falls within the 2.51-2.41 Ga range [Söderlund et al, 2010]. Rocks that underwent HT and UHT granulite-facies metamorphism in the early Palaeoproterozoic 2.56-2.42 Ga ago are known from cratons in India (Nilgiri Complex), Antarctica (Napier Complex), and elsewhere [Raith et al, 1990[Raith et al, , 1999Harley, 1998;Konilov et al, 2001;Asami et al, 2002;. At the passive margins of the Pilbara Craton in Australia and the Kaapvaal Craton in South Africa, the time interval from 2.51 to 2.45 Ga was characterized by a peak of metamorphism and the origin of BIFs under extension related to the impact of a global plume [Barley et al, 2005].…”

Section: Superplume-related Evolution Beyond Lauroscandiamentioning

confidence: 99%

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

2007

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Paradoxically, the lists of "proxies" of both plate-and plume-related settings are devoid of even a mention of the high-grade metamorphic rocks (granulite, amphibolite and high-temperature eclogite facies). However, the granulite-gneiss belts and areas which contain these rocks, have a regional distribution in both the Precambrian and the Phanerozoic records. The origin and evolution of the granulite-gneiss belts correspond to the activity of plumes expressed in vigorous heating of the continental crust; intraplate magmatism; formation of rift depressions filled with sediments, juvenile lavas, and pyroclastic flow deposits; and metamorphism of lower and middle crustal complexes under conditions of granulite and high-temperature amphibolite facies that spreads over the fill of rift depressions also. Granulite-gneiss complexes of the East European Craton form one of the main components of the large oval intracontinental tectonic terranes of regional or continental rank. Inclusion of the granulite-gneiss complexes from Eastern Europe, North and South America, Africa, India, China and Australia in discussion of the problem indicated in the title to this paper, suggests consideration of a significant change in existing views on the relations between the plate-and plume-tectonic processes in geological history, as well as in supercontinent assembly and decay. The East European and North American cratons are fragments of the long-lived supercontinent Lauroscandia. After its appearance at ~2.8 Ga, the crust of this supercontinent evolved under the influence of the sequence of powerful mantle plumes (superplumes) up to ~0.85 Ga. During this time Lauroscandia was subjected to rifting, partial breakup and the following reconstruction of the continent. The processes of plate-tectonic type (rifting with the transition to spreading and closing of the short-lived ocean with subduction) within Lauroscandia were controlled by the superplumes. Revision of the nature of the granulite-gneiss complexes has led to a fundamental new understanding of: a more important role than envisaged previously for mantle-plume processes in the juvenile additions to the continental crust, especially during the Neoarchaean-Proterozoic; the existence of the supercontinent Lauroscandia from ~2.80 to 0.85 Ga; the leading role of mantle plumes in the interaction of plate-and plume-tectonics in the Neoarchaean-Proterozoic history of Lauroscandia and perhaps of the continental crust as a whole. We propose that the evolution of the geodynamic settings of the Earth's crust origin can be represented as a spiral sequence: the interaction of mantle-plume processes and embryonic microplate tectonics during the Palaeo-Mezoarchaean (~3.8-2.8 Ga) → plume-tectonics and local plume-driven plate-tectonics (~2.80-0.55 Ga) → Phanerozoic plate tectonics along with a reduced role of mantle plumes.Key words: Precambrian; plate-tectonics; plume-tectonics; granulite-gneiss belts; supercontinent; intracontinent oval orogenRecommended by E.V. Sklyarov Аннотация: Ка...

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Section: Superplume-related Evolution Beyond Lauroscandiamentioning

confidence: 99%

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

2007

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“…However, the expense of this instrumentation hinders the wide application of this technique. Chemical dating by electron microprobe (EMPA) is another important approach for xenotime dating [21][22][23][24][25]. However, the low precision of this technique limits its applications in geological processes.…”

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In situ U-Pb dating of xenotime by laser ablation (LA)-ICP-MS

Liu

Guo

et al. 2011

Chin. Sci. Bull.

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Xenotime is an ideal mineral for U-Th-Pb isotopic dating because of its relatively high U and Th contents, but typically low concentration of common Pb. These characteristics, and the fact that it is widespread throughout various types of rocks, suggest that the U-Th-Pb dating of xenotime has broad applications. Studies of U-Pb dating on xenotime by ion microprobe (such as SHRIMP) have increased in recent years, whereas studies by laser ablation (LA)-ICP-MS are still rare. In this study, we developed a technique for U-Pb dating of xenotime using the 193 nm ArF laser-ablation system and Agilent 7500a Q-ICP-MS. To evaluate the reliability of our method, a xenotime standard, BS-1, was analyzed and calibrated against another xenotime standard, MG-1. The weighted mean 206 Pb/ 238 U ages of 510.1 ± 5.2 Ma (2 n = 21), 509.8 ± 4.3 Ma (2 n = 21) and 510.0 ± 4.6 Ma (2n = 21) were obtained using beam diameters of 16, 24 and 32 m, respectively. These ages are identical to those determined by ID-TIMS method (weighted mean 206 Pb/ 238 U age of 508.8 ± 1.4 Ma), which supports the reliability of our LA-ICP-MS method. We also analyzed xenotimes in leucogranites from South Tibet and granites from Xihuashan in southern China, and obtained accurate and precise ages. Nevertheless, we observed systematic differences in Pb/U fractionation among xenotime, monazite and zircon. The matrix-effect resulted in either under-correction or over-correction of fractionation, and thus led to inaccurate ages. Thus, a matrix-matched material is required for U-Pb dating of xenotime by LA-ICP-MS.

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“…In many cases, this accuracy is sufficient for solving many geological problems; the significantly lower cost of electron probe microanalysis and the possibility of compiling an age map for the whole surface area of the studied crystal should also be taken into consideration [6][7][8].…”

Section: Resultsmentioning

confidence: 99%

“…The high stability of zircon makes it suitable for interpreting the genesis of magmatic rocks [1,2] and determining their age by isotope dilution [3], secondary ion mass spectrometry [4], and the Th-U-Pb method [5], which can be used for determining Th, U, and Pb in zircon [6,7]. In these terms, valuable information can be derived from both morphological features and geochemical parameters, primarily from the distribution of the major and impurity elements in the crystal [9].…”

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Potentials of Electron Probe Microanalysis in Studying Zircons

Romanenko

Petrov

2005

J Anal Chem

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Zircon is a widespread accessory mineral of magmatic rocks; it attracts interest because of its high stability to chemical and mechanical erosion within the geochemical cycle. The high stability of zircon makes it suitable for interpreting the genesis of magmatic rocks [1, 2] and determining their age by isotope dilution [3], secondary ion mass spectrometry [4], and the Th-U-Pb method [5], which can be used for determining Th, U, and Pb in zircon [6,7]. In these terms, valuable information can be derived from both morphological features and geochemical parameters, primarily from the distribution of the major and impurity elements in the crystal [9].Most of the data on zircon geochemistry are usually obtained by analyzing relatively large samples using the methods of nuclear physics (neutron activation analysis), emission spectroscopy, atomic absorption spectroscopy, inductively coupled plasma emission spectroscopy, and others. All these methods are characterized by good detection limits (10 -3 to 10 -7 %), while determining total impurity elements. Spark mass spectrometry [10] is also characterized by insufficient locality properties (more than 100 µ m spot) as compared to electron probe microanalysis and ion microprobe analysis. The latter method, although having unique analytical capabilities [4], is poorly available and presents difficulties with the interpretation of the experimental data. Nuclear microprobes can possibly be used as an alternative, but no data are yet available on the use of these instruments for studying zircons.Electron probe microanalysis was used for studying the ore specialization of granitoids as early as in 1977 [11]. Extensive studies of zircons by electron probe microanalysis were reported in works by Krasnobaev [3,9]. In spite of its good locality, electron probe microanalysis exhibits significant limitations in detection limit compared to the bulk analytical methods mentioned above.The main performance characteristics of any analytical method, including electron probe microanalysis, in determining impurity and trace elements is the detection limit, which is closely related to the signal-to-noise ratio, statistical validity, and reliability of the experimental analytical and background signals. The latter condition is substantially related to the change in the effective (average) atomic number of the sample studied, which (along with the overlap of interfering lines and their diffusely scattered tails) is the major factor that affects background intensity upon the electron excitation of x-ray emission. The value substantially depends on the concentration of the heaviest elements in the sample. In zircon, this is impurity of hafnium ( Zr , Hf ) O 2 · SiO 4 ; therefore, the effective atomic number in the absence of the Hf impurity is = 24.84 ; = 62.3. Even a small impurity of hafnium appreciably affects the intensity of the major background component (bremsstrahlung radiation). This effect may be one of the main reasons for the systematic error in measuring (without losing the analyti...

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Chemical Th–U–total Pb dating by electron microprobe analysis of monazite, xenotime and zircon from the Archean Napier Complex, East Antarctica: evidence for ultra-high-temperature metamorphism at 2400 Ma

Cited by 84 publications

References 44 publications

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

In situ U-Pb dating of xenotime by laser ablation (LA)-ICP-MS

Potentials of Electron Probe Microanalysis in Studying Zircons

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