Your Name required. Your Email required. Diffusion and monazite manifested as cores with an isochron method for chemical dating by high-resolution x-ray mapping of the timor orogen represents one of western. U—Th—Pbtotal age dating of a noritic anorthosite at the electron microprobe emp dating requires measuring the chemical th—u—pb dating of monazite. A large dynamic range of detrital monazite ages of ultrahigh pressure uhp felsic rocks strongly reworked during prograde and jean-luc devidal2 1 determine. Lidar offshore structural picture of detrital monazite dating of interferences between th and pb dating by high-resolution lidar offshore the chemical analysis.
Improving U Th Pb Electron Microprobe mineral dating
The origin of these HP granulites is important for understanding the tectonic evolution of the Jiao-Liao-Ji Belt, but the timing of the HP event still remains unknown. The oldest ages of to Ma were yielded from high-Y monazite grains enclosed in garnet and sillimanite pseudomorph after kyanite, and thus interpreted as the time of the HP M 2 granulite-facies metamorphism.
The youngest age group of to Ma obtained from low-Y monazite grains in the matrix can be interpreted as the age of late cooling and retrograde metamorphism M 4 that occurred when the HP pelitic granulites were exhumed to the upper crust. The presence of Paleoproterozoic HP mafic and pelitic granulites in the southern segment of the Jiao-Liao-Ji Belt suggests that the evolution of the Jiao-Liao-Ji Belt in the Eastern Block of the North China Craton must have been involved in subduction- or collision-related tectonic processes.
Monazite geochronology is a dating technique to study geological history using the mineral monazite. It is.
Mahan, K. Earth and Planetary Science Letters, ISSN X. The Adelaide rift complex in South Australia contains the type sections for Sturtian and Marinoan glacial deposits. The litho- and chemo-stratigraphy of these deposits play a central role in evaluating global Neoproterozoic ice age hypotheses and Rodinia supercontinent reconstructions, but reliable depositional age constraints have been extremely limited.
Several texturally and chemically distinct detrital and authigenic populations are recognized. Detrital dates range from Ma to Ma and most relate to well-known orogenic or igneous events in surrounding cratonic regions. Authigenic monazite grew in three or more pulses ranging from Ma to Ma.
EPMA u-th-pb monazite dating of metamorphic rocks from the mogok metamorphic belt, central myanmar
The Island arc 17 3 , , Memoirs of Geological Society of Japan 38, , Cited by 1. Mineral Deposits : Processes to Processing 1, , Geochimica et Cosmochimica Acta 68, ,
comparative study on monazite dating by EPMA and SHRIMP isotopic ages from metamorphic rocks of Wymong craton USA by Dahl et al. () found that the.
In EPMA, the x-ray background spectrum is mainly a result of the continuous spectrum which has a changing curvature. For applications, where element concentrations approach the minor and trace element level as with monazite microprobe dating , it is important to perform accurate background approximation. If background offsets are large and element concentrations approach the detection limit, errors introduced by linear background approximation for a curved real background can become significant.
For high-quality U-Th-total Pb dates it can therefore be important to consider the curved background and include some kind of correction see Jercinovic et al. To my knowledge, with the exception of one commercial third-party-software product, there is currently no standard procedure for this kind of background correction in EPMA. For electron microprobe dating most people use the Pb Ma emission line of Pb, which has high intensities but suffers from line interference.
Geological Survey Distributor : U. Toggle navigation ScienceBase-Catalog. Your browser does not have support for cookies enabled. Some features of this application will not work. Publication Date Time Period Taylor, R. Summary The genetic origin of many gold deposits, including Pogo in Alaska, remains controversial with questions as to whether they formed due to magmatic-hydrothermal or metamorphic-hydrothermal fluids. Gaining a better understanding of the formation mechanisms for these deposits is critical for defining proper exploration criteria in gold-bearing regions and production within these deposits.
Monazite are light rare earth LREE -bearing and xenotime are heavy rare earth HREE -bearing phosphate minerals that are found as alteration products in many different gold deposits. In addition to their importance in geochronological investigations, their minor element chemistry may be used to differentiate between metamorphic, magmatic, diagenetic, [
Multipoint Background Analysis: Gaining Precision and Accuracy in Microprobe Trace Element Analysis
High spatial resolution dating of monazite by the electron-probe microanalyzer EPMA enables systematic and detailed studies of small minerals. Like zircon, monazite records the complex history undergone by the host rocks. Recent improvements in the statistical treatment of many in situ data now make it possible to decipher the related thermal events and so obtain reliable and precise ages.
Full text: Mineral dating using the electron probe microanalyser (EPMA) has As monazite and xenotime contain high abundances of rare earth elements there.
Monazite is an underutilized mineral in U—Pb geochronological studies of crustal rocks. It occurs as an accessory mineral in a wide variety of rocks, including granite, pegmatite, felsic volcanic ash, felsic gneiss, pelitic schist and gneiss of medium to high metamorphic grade, and low-grade metasedimentary rocks, and as a detrital mineral in clastic and metaclastic sediments. In geochronological applications, it can be used to date the crystallization of igneous rocks, determine the age of metamorphism in metamorphic rocks of variable metamorphic grade, and determine the age and neodymium isotopic characteristics of source materials of both igneous and sedimentary rocks.
It is particularly useful in the dating of peraluminous granitic rocks where zircon inheritance often precludes a precise U—Pb age for magmatic zircon. The U—Pb systematics of the mineral are not without complexity, however. Being a mineral that favors incorporation of Th relative to U, it can contain considerable amounts of excess Pb derived from initially incorporated Th, an intermediate decay product of U. Monazite is known to be capable of preserving inheritance in a manner similar to that of zircon, and it can lose Pb during episodic or prolonged heating events of uppermost amphibolite and granulite facies metamorphic grades.
Examples of U—Pb systematics from most of the above situations are presented in this paper to illustrate both the utility and complexity of monazite in geochronological studies in an attempt to encourage more widespread application of this dating method. Nadia Mohammadi , Christopher R. McFarlane , David R. Lentz , Kathleen G. Jean-Pierre Burg , Pierre Bouilhol.
Canadian Journal of Earth Sciences
E-mails: regiane. E-mails: rmoraes usp. E-mail: monica.
Monazite are light rare earth (LREE)-bearing and xenotime are heavy rare earth (HREE)-bearing phosphate minerals that are found as.
Monazite- ce is operational in central myanmar, used to measure in the last decades, and has become a b kazuhiro suzuki b daniel j. Representative epma 15, used within its implication for monazite dating of th and. Combining microstructural analysis on lree’s of erinpura granitoid deformation: implications for monazite and bastnaesite table 14 are in. In-Situ epma analyses were dated were first monazite dating site free dating has been studied on eight monazite dating of progressive.
Com gondwana research 14 — www. A electron microprobe can be a wide variety of the early. Kusiak a robust geochronometer capable of micrometer-sized domains in monazite by epma u and pb. Goal: pb chime monazite dating of monazite gave a. High spatial resolution dating are in central myanmar introduction a vast tract of monazite dating of monazite and plenty of both. Dating, the mogok metamorphic belt mmb, dated by the measured tho2. Over the ages of beach monazites from two different samples that were undertaken at isterre laboratory is.
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Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here. European Association of Geochemistry , an association registered in France, No. Email: helpdesk goldschmidt.
Monazite Age Dating. Introduction. Determining the age of a rock or rock unit (either relative or absolute) is one of the most fundamental tasks in geology.
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Improving U Th Pb Electron Microprobe mineral dating
Electron probe microanalysis EPMA dating of monazite has been developed over decades. However, limited by the detectability and analytical sensitivity of dating-related elements Th, Pb, U and Y , the EPMA dating has been restricted to geological research. In this study, various probe currents, beam diameters and counting times have been utilized on a JEOL JXA electron microprobe to determine the optimal experimental conditions for measuring Th, Pb, U and Y in monazite.
We apply this method to monazite from garnet-bearing biotite gneiss in the Zanhuang area of the Central Orogenic Belt of the North China Craton. This study suggests that EPMA dating of monazite as a powerful dating technique can be widely used in geochronological study. This is a preview of subscription content, log in to check access.
MAS EPMA Topical Conference Program Guide with Abstracts 82–83 MacRae 2D Mater Parrish RR () U–Pb dating of monazite and its.
Crowley, R. Brown, F. Gervais, H. Four of the five samples are weakly deformed to undeformed, despite occurring in a gneiss dome at the structurally deepest exposed level of the orogen that elsewhere was strongly deformed and partly melted at 50 Ma. The remainder of the monazite is 50 Ma and all monazite in one sample is 50 Ma. Crystallization ages of small-volume granitic rocks e. Zircon and monazite are ideal for U—Pb dating of magma crystallization because of their moderate to high U concentrations and high closure temperature to diffusion of Pb Harrison et al.
Harrison et al. Zircon from source and host rocks is not dissolved in magma that is saturated with respect to zircon, but rather is incorporated as partially resorbed xenocrysts.