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Available online at Gondwana Research 14 () – EPMA and PIXE dating of monazite in.
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.
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this lab, monazite U-Th-Pbtotal dating by EMP is on the top of my list! • Monazite = light rare-earth element (REE) phosphate: La, Ce, Nd, Pr.
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.
Small-volume granitic melts are usually produced by anatexis of peraluminous crustal rocks at temperatures low enough that complete zircon dissolution does not occur, and thus some degree of inheritance is expected in all melts. Inherited zircon varies from forming a minor part of the zircon population as rare cores within newly formed zircon to forming a large part as plentiful whole grains.
Monazite saturation in granitic melts occurs in a similar way to zircon saturation Rapp et al. The best known examples are two Himalayan leucogranites with sparse inherited monazite Copeland et al. Discerning inherited from non-inherited zircon is central to some of the most intense geochronological debates, including that regarding the age of the oldest chemical evidence of life on Earth Nutman et al.
Improving U Th Pb Electron Microprobe mineral dating
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Monazite are light rare earth (LREE)-bearing and xenotime are heavy rare earth (HREE)-bearing phosphate minerals that are found as.
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, , Journal of Geophysical Research 89, , Pre-Cretaceous Terranes of Japan, , Tectonics and Metamorphism The Hara Volume , , Monograph, the Association for Geological Collaboration in Japan 49, , Explanatory text of the geological map of Japan, scale , Oeyama, Kyoto no.
Explanatory text of the geological map of Japan, scale , Maizuru, Kyoto no. Journal of Mineralogy, Petrology and Economic Geology 89, , Journal of Geological Society of Japan 67, , Journal of Geological Society of Japan 68, ,
Multipoint Background Analysis: Gaining Precision and Accuracy in Microprobe Trace Element Analysis
Evins, P. Australian Journal of Earth Sciences 54 1 , pp. These ages are particularly significant with respect to the timing of deposition, iron and gold mineralisation, and deformation in the Mt Isa inlier. The oldest age probably represents provenance from igneous rocks. In the sample, the majority of monazite growth occurred at Ma, coeval with peak metamorphism in the Eastern Succession.
The low metamorphic grade of the conglomerate and wide compositional range of monazite bearing this age indicates that the monazite grew elsewhere and was later deposited in the conglomerate.
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.
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.
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Electron probe micro-analyzer (EPMA)
E-mails: regiane. E-mails: rmoraes usp. E-mail: monica.
Electron Probe MicroAnalysis (EPMA) is a non-destructive technique to film analysis; Monazite age dating; LaB₆ Electron Source for maximum versatility.
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. Andrew DuFrane.
Significance of monazite EPMA ages from the Quamby Conglomerate, Queensland
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.
Characterization and metamorphic evolution of Mesoproterozoic granulites from Sonapahar (Meghalaya), NE India, using EPMA monazite.
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. Shrimp u-pb geochronological studies of monazite in u-pb monazite standard reference materials with.
Analyses of the timing of techniques, and seek you. Jump to pervasive ga polymetamorphism is used to chemical data is an r mm spectrometer and its. U-Pb geochronological studies of how chemical geology, east antarctica: as chemical aging method which is supplied by electron microprobeth-u-pb monazite dating a.
EPMA u-th-pb monazite dating of metamorphic rocks from the mogok metamorphic belt, central myanmar
The wide utilization of radiometric ages for orogen analyses would not been possible without monazite and zircon that are sufficiently robust to preserve their original U and Th and accumulated radiogenic Pb even through overgrowth during high temperature geologic events. Monazite and zircon discriminate strongly against the daughter Pb during crystallization. Although the EPMA dating inherits the classic Th-U-Pb chemical dating, the CHIME method provides a significant advantage by adopting the regression-based technique that has the ability to work with minerals containing substantial initial Pb.
The age- and composition-mapping can identify two or more chronologically homogeneous domains that are separated by age gaps within a single grain. Critical comments include the chemical criteria that discriminate possibly concordant EPMA zircon and monazite analyses from discordant ones.
use of EPMA in acquiring major and trace element compositions of monazite, particularly high-precision analysis of U, Th, and Pb for dating;.