We use this setting to explore the evolution of monazite grain size, texture and composition, and variations in the whole-rock composition of 11 metapelite, metapsammite or metachert samples collected along the metamorphic field gradient. Monazite grain size increases with rising metamorphic grade, regardless of the whole-rock composition. A succession of four compositional domains is recognized in monazite. In the highest-grade sample, zircon grains included in garnet or cordierite show metamorphic rims with sillimanite and Si-rich inclusions. Monazite dating by electron microprobe and laser ablation inductively coupled plasma mass spectrometry reveals two age groups. This contribution is dedicated to the memory of Professor Kazuhiro Suzuki, for his contribution to geochronology and Japanese geology.
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Late Permian volcanic dykes in the crystalline basement. Western Carpathians :. Manuscript received November 29, ; accepted in revised form September 28,
CHIME dating of monazite exsolutions was performed by a JXAM electron microprobe in the State Key. Laboratory for Mineral Deposits Research at Nanjing.
The basement of the Hwacheon area in the northern part of the Gyeonggi massif in the Korean Peninsula comprises granulite and gneiss complexes that are separated by an extensive mylonite zone. Granulites distant from the mylonite zone show little evidence of a retrograde overprint beyond minor growth of biotite along garnet grain boundaries. Monazite grains enclosed in garnet show a core to rim decrease in Y, and those in the matrix show a peripheral enrichment of Y on low-Y interiors.
Similarly, garnet grains decrease in Y from core to rim, with peripheral Yenrichment, which can be attributed to early to peak garnet growth and post-growth modification, respectively. Granulites near the mylonite zone show growth of cordierite and biotite aggregates around garnet grains, and yield Permo-Triassic monazite domains on and within predominantly Paleoproterozoic monazite grains.
Mylonitized granulites have a metamorphic overprint characterized by the growth of the sillimanite and K-feldsper assemblage at ca. Pelitic gneisses in the gneiss complex contain zircon grains with Neoproterozoic detrital cores and monazite grains with unequivocal metamorphic ages of ca. Geological, petrological and chronological evidence suggests differing evolutional histories between two crustal domains prior to amalgamation.
The widespread occurrence of Permo-Triassic paragneisses and mylonites in the Gyeonggi massif can be explained by detachment of the metamorphosed upper crust of the South China block, which was thrust over the Paleoproterozoic granulite complex at ca. Permo-Triassic metamorphic overprints on the latter are attributed to contact metamorphism from the hot allochthon. This is a preview of subscription content, log in to check access.
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Canadian Journal of Earth Sciences
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GR Focus. CHIME dating of monazite, xenotime, zircon and polycrase: Protocol, pitfalls and chemical criterion of possibly discordant age data.
Migmatised metapelites from the Kodaikanal region, central Madurai Block, southern India have undergone ultrahigh-temperature metamorphism degrees C; kbar. In-situ electron microprobe Th-U-Pb isochron CHIME dating of monazites in a leucosome and surrounding silica-saturated and silica-poor restites from the same outcrop indicates three principal ages that can be linked to the evolutionary history of these rocks.
Monazite grains from the silica-saturated restite have well-defined, inherited cores with thick rims that yield an age of ca. This either dates the metamorphism of the original metapelite or is a detrital age of inherited monazite. Monazite grains from the silica-poor restite, thick rims from the silica-saturated restite, and monazite cores from the leucosome have ages ranging from to Ma suggesting a mean age of Ma within the error bars.
In the leucosome the altered rim of the monazite gives an age of ca. Alteration takes the form of Th-depleted lobes of monazite with sharp curvilinear boundaries extending from the monazite grain rim into the core. We have replicated experimentally these altered rims in a monazite-leucosome experiment at degrees C and 2 kbar. This experiment, coupled with earlier published monazite-fluid experiments involving high pH alkali-bearing fluids at high P-T, helps to confirm the idea that alkali-bearing fluids, in the melt and along grain boundaries during crystallization, were responsible for the formation of the altered monazite grain rims via the process of coupled dissolution-reprecipitation.
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U-Pb zircon and CHIME monazite dating of granitoids and high-grade metamorphic rocks from the Eastern and Peninsular Thailand — A new report of Early.
Bernhard Schulz Prof. Date of birth: Deformation, metamorphism and petrography of the Austroalpine basement to the south of the Tauern Window, Eastern Alps. September Korrespondent of the Geologische Bundesanstalt at Vienna. February Appointment as Professor apl. Metamorphic rocks: My research interest centers on metamorphic rocks. The methods of geothermobarometry, geochronology, microstructural study and geochemistry are applied to these rocks for the reconstruction of the geodynamic processes and formation of mineral deposits.
Prof. Dr. Bernhard Schulz
Jercinovic University of Massachusetts. Assumption: No non-radiogenic lead in monazite or at least very little. If you can precisely measure U, Th, and Pb in ppm , you can solve this equation iteratively for lead to obtain an age. Map thin section with the microprobe Ce, Fe, Y to find all monazite crystals.
Monazite is most suitable to the CHIME dating, since it shows a concordant Th-U-Pb relation, contains wt.% ThO2 and wt.% UO2 that can produce.
The granites with I- and S-type affinity in the Variscan segments of the Alpine West-Carpathian edifice belong to the oldest intrusions within the European Variscides. Granites and granodiorites of the West-Carpathian crystalline basement are mostly classified as S-type, whereas tonalities and granodiorites belong to the I-type suite. Both suites probably originated in the volcanic arc setting as product of subduction-related regime in the Galatian superterrane Broska et al. The CHIME age from monazite dating shows Ma because monazite indicate probably early stage of massive granite alteration perhaps during collisional process, younger zircons represents later phase of the event.
The granite showing strong greisenization total degradation of feldspars and formation of quartz – white mica assemblages is dated by SHRIMP on Ma. The greisenised granite contains abundant tourmaline with high dravitic molecule, Sr-rich apatite and common monazite. Abundant tiny stoichiometrically pure apatite grains in this granite indicate their exsolution from feldspars enriched in phosphorus.
The evolution of the I- and S-type granites seems to be rather different from the granite evolution known in the Bohemian Massif and therefore the origin of Variscan hybrid granites from the Western Carpathians we placed on the SW side of Galatian volcanic arc as result of Paleo-Tethys subduction see Stampfli and Borel, , Stampfli et al.
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Posted in Dating. Japan Atomic Energy Agency, 2. Nagoya University. Presentation information Print Tweet. The age spectrum of detrital monazite grains is a useful measure for the provenance analyses of clastic sediments. The CHIME is best suited for dating of detrital monazite where grains are not chronologically uniform and many analyses are required to characterize a population.
U–Th–Pbtotal age determinations in monazite in a noritic anorthosite at CHIME dating of monazite, xenotime, zircon and polycrase: protocol.
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