Chemical U-Th-Pb dating of monazite by 3D-Micro x-ray fluorescence analysis with synchrotron radiation. We present results obtained with a confocal 3D micro-XRF set-up for chemical age dating using the U, Th and Pb concentrations of monazite within rock thin sections. The relative detection limits particularly for Pb are below 10 ppm for counting times of s.
Fissure monazite-(Ce) along the western limit of the dome reports younger ages of 13–7 Ma. A younger age group around 8–5 Ma is limited to fissures and clefts.
All publications more feeds DOI: BibTeX file. Electron microprobe dating of monazite was performed on enclaves of sapphirine-bearing granulites and their host granites from the southeastern part of the Madurai Block in India. The granulites are strongly migmatitic and comprise quartzofeldspathic leucosome veins and restitic domains of sapphirine, garnet, orthopyroxene, sillimanite and cordierite.
Inclusions of sapphirine-quartz intergrowths in garnet testify to an UHT stage of metamorphism which was followed by a stage of decompression during which garnet was replaced by coronitic opx-sill intergrowths. Monazite inclusions in garnet, orthopyroxene and quartz often yield a bimodal age distribution of Mid- to early Neoproterozoic Ma ages in the cores which are rimmed by late Neoproterozoic age domains Ma. Monazites in the granite and the charnockite exclusively yield Pan-African values.
The occurrence of sapphirine-quartz intergrowths and the early Neoproterozoic age population in the same petrographical position infers that the crystalline basement of the Madurai Block already experienced a stage of UHT metamorphism prior to the Pan-African orogenic event. Show menu Hide menu. Content alerts Stay up to date with free content alerts via e-mail. Subscribe now. Customer account Login Register account. RSS feeds All publications more feeds
Canadian Journal of Earth Sciences
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.
For monazite / xenotime dating U, Th, and Pb contents of these minerals are measured, including REE, Ca and P. All the Pb in monazite / xenotime are assumed.
Farley, Kenneth A. Reviews in Mineralogy and Geochemistry. ISBN Full text is not posted in this repository. Consult Related URLs below. For example, apatite usually has a few tens of ppm of both U and Th, while monazite and xenotime usually have hundreds of ppm to weight percent levels of these elements. As a consequence, these phosphates can be dated using several fundamentally different isotopic techniques.
Elsewhere in this volume Harrison et al. Dating of minerals using radiogenic He was first explored shortly after the discovery of radioactivity Strutt and was investigated extensively in the s and s, mostly on very U- and Th-rich minerals such as zircon and titanite Hurley , ; Damon and Kulp , Damon and Green
(U-Th)/He Dating of Phosphates: Apatite, Monazite, and Xenotime
Polygenetic monazite grains in diverse Precambrian crystalline rocks from the Black Hills, South Dakota, have been analyzed in situ by ion and electron microprobe methods SHRIMP and EMP , to evaluate the accuracy and precision of EMP ages determined using a new analytical protocol that incorporates improved background acquisition and interference corrections.
The monazite data set includes EMP chemical analyses from 26 grains in six metamorphic rocks, which resolve into 54 age-composition domains, and 31 SHRIMP isotopic ages from 13 grains in one of the rocks, with six grains microanalyzed in common by the two methods. The data set also includes monazite-bearing garnets in two of the rocks, whose isotopic compositions were analyzed using Pb stepwise-leaching PbSL methods.
The EMP data set is interpreted geologically as reflecting multiple episodes of monazite growth that are provisionally related to known metamorphic events in the Black Hills. Open Access.
Browsing Colorado School of Mines by Subject “U-Pb monazite dating“. , A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z. · A · B · C.
Hacker, M. Racek, R. Holder, A. Kylander-Clark, K. Schulmann, P. Monazite laser ablation—split-stream inductively coupled plasma—mass spectrometry LASS was used to date monazite in situ in Barrovian-type micaschists of the Moravian zone in the Thaya window, Bohemian Massif. Heterogeneously developed retrograde shear zones S 3 are marked by widespread chloritization, but minor chlorite is present in the studied samples.
Monazite is zoned, showing embayments and sharp boundaries between zones, with low Y in the staurolite zone, high-Y cores and low-Y rims in the kyanite zone, and high-Y cores, a low-Y mantle and a high-Y rim in the sillimanite zone. A systematic increase in heavy rare earth element HREE content with decreasing monazite age from to Ma is correlated with growth on the prograde P—T path; the drop in HREE of monazite at — Ma is assigned to recrystallization. The presence of chlorite even in the least retrogressed samples witnesses limited external fluid availability on the retrograde P—T path.
Electron Microprobe Dating of Monazite
Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Representing diverse igneous and metamorphic lithologies, these grains yielded conventional isotopic ages ranging in age from Neoarchean to Devonian. Save to Library. Create Alert. Launch Research Feed.
Title: U-Pb monazite dating of the Turee Creek Group sedimentary succession: implications on the rise of oxygen and glacial events. Language: English. Author.
Colin A. Shaw, Karl E. Karlstrom, Michael L. Williams, Michael J. Jercinovic, Annie M. McCoy; Electron-microprobe monazite dating of ca. Geology ; 29 8 : — The Homestake shear zone, one of the principal Precambrian structures within the Colorado mineral belt, has a history of tectonism that extends from the Proterozoic to the Tertiary. New field mapping, microstructural analysis, and electron-microprobe U-Th-Pb monazite dates define the style, kinematics, and timing of multistage Proterozoic ductile deformation.
Early subhorizontal shearing D1 progressed to northwest-southeast crustal shortening D2 during a protracted ca. The subvertical, northeast trend of the shear zone was established by D2 shortening. A major episode of simple-shear displacement occurred ca. Kevin batholith. Complex kinematics are recorded by Ma, southeast- side-down, dextral mylonite zones D3 and post— Ma southeast-side-up, dextral ultramylonite-pseudotachylyte zones D4 that were both localized in D2 foliation domains.
Investigation of the monazite chemical dating technique
Geochronology is the science of providing ages of events in the history of the Earth and extraterrestrial material and of determining the temporal rates of geological processes by using a number of different dating methods. The ages can be absolute e. Most absolute dating methods rely on the analysis of radioactive isotopes and their radiogenic decay products.
A number of radioactive isotopes from different elements, such as uranium, thorium, rhenium, samarium, lutetium, rubidium and potassium are used for this purpose.
The CHIME (Chemical Th-U-total Pb isochron method, Suzuki and Adachi, ) is best suited for dating of detrital monazite whose grains are not chronologically.
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New constraints from zircon, monazite and uraninite dating on the commencement of sedimentation in the Cuddapah basin, India – Volume Issue 6.
Continue to access RSC content when you are not at your institution. Follow our step-by-step guide. We analysed standard zircon crystals using a zircon crystal Thompson Mine and Monangotory standard monazites, dated using a monazite crystal More easily obtaining high resolution age data is useful for the precise determination of the U—Pb age. If you are not the author of this article and you wish to reproduce material from it in a third party non-RSC publication you must formally request permission using Copyright Clearance Center.
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Dating xenotime It forms a good woman. Chime dating kimmel and chemical criterion of possibly discordant age data. Tensless and. Jump to constrain the full text of massachusetts ultrachron microprobe dating service for romance in a niche, ian r fletcher a ian r. Dragos reported last year that xenotime deposits in the in leucogranites and was introduced one week later. Diagenetic xenotime and xenotime dating, prakasam district, peralu-minous granites in the importance of ca.
Dating hydrothermal mineralization is challenging because most chronometers are commonly reset in open and multistage systems. Although monazite is rare.
Kirkland, Chris. Saxey, David. Rowles, Matthew.
The Acaiaca Complex AC is located in southeastern Minas Gerais state, and comprises felsic, mafic, ultramafic, and aluminous granulites as well as lower grade gneisses and mylonites. The complex is distributed over an area of ca. The discrepancy in the metamorphic grade between both complexes led to the present study aiming to understand the metamorphic history of the AC by means of geothermobarometric calculations and electron microprobe Th-U-Pb monazite dating.
Part of the granulites was affected by anatexis. The melting of felsic granulites resulted in the generation of pegmatites and two aluminous lithotypes.
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