Monazite geochronology is a dating technique to study geological history using the mineral monazite. It is a powerful tool in studying the complex history of metamorphic rocks particularly, as well as igneous , sedimentary and hydrothermal rocks. The uniqueness of monazite geochronology comes from the high thermal resistance of monazite, which allows age information to be retained during the geological history. Also, textures of monazite crystals may represent certain type of events. Therefore, direct sampling techniques with high spatial resolution are required, in order to study these tiny zones individually, without damaging the textures and zonations. The advantage of monazite geochronology is the ability to relate monazite compositions with geological processes. Finding the ages of compositional zones can mean finding the ages of geological processes. Monazite is a rare-earth-element phosphate mineral , with the chemical formula e.
Monazite geochronology (EPMA)
Continue to access RSC content when you are not at your institution. Follow our step-by-step guide. Monazite oxygen isotopes are an ideal tracer of the fluid—rock interaction during metamorphism and hydrothermal activity.
Zircon U–Pb SHRIMP and monazite EPMA U–Th–total Pb geochronology of (d) The weighted average of mean ages from monazite in the sample. Longshoushan block： Constraint from LA-ICP-MS U-Pb zircon dating.
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.
Gold is also present in some of the samples. Together, these ages bracket deposition of the Quamby Conglomerate to between ca and Ma, the latter age most likely representing diagenesis. This depositional age also represents a maximum age for north — south-striking, upright folds of the Quamby Conglomerate and implies that significant ductile deformation has affected parts of the Mt Isa inlier after Ma and probably after Ma. Cited 8 times in Google Scholar.
Improving U Th Pb Electron Microprobe mineral dating
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.
A new electron microprobe dating method. The corresponding author, Patrik Konečný, is a long time user of CAMECA SX EPMA. Leading the.
If you can’t see some “in-line” images in a post, try “refreshing” your browser! Welcome, Guest. Please login or register. News: If you can’t see some “in-line” images in a post, try “refreshing” your browser! Home Help Search Login Register. Julien Professor Posts: 76 The truth is out there There are several points to be aware of for such analyses – always keeping in mind that we are here dealing with TRACE element analysis.
Among numerous potential issues, there is the need for Whereas a two-point background acquisition works for a major or minor element analysis, the need for more accurate background is an absolute necessity.
Multipoint Background Analysis: Gaining Precision and Accuracy in Microprobe Trace Element Analysis
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.
His attraction to the EPMA led him to the University of Massachusetts-Amherst from , where he pursued a post-doc on trace element analysis and monazite.
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.
Electron probe micro-analyzer (EPMA)
Free subscriptions to newsletters, print publications, and more. Electron Probe MicroAnalysis EPMA is a non-destructive technique to determine chemical composition of small amounts of solid materials. A focused beam of high-energy electrons hits the sample and generates characteristic x-rays corresponding to the elements present in the material. The beam current is typically between nA, much more intense than SEM.
Characteristic x-rays are produced by inelastic collisions of the incident electrons with electrons in the inner shell of atoms in the sample.
lytical protocol for chemical dating of monazite using the. LEO VP scanning electron microscope (SEM) at the. Geological Survey of Norway (NGU).
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. The in-situ CHIME dating and mapping of zircon and monazite in polished thin sections coupled with compositional mapping of associate garnet has a great chronological potential for the analysis of the detailed sequence of geologic events.
The improved CHIME method revealed that 1 the garnet granulite and the eclogite in the Hongseong area of the Gyeonggi Massif within the Korean Peninsula have different evolutional histories as opposed to the current view of the formation by a single Permo-Triassic collision, 2 the widespread Permo-Triassic paragneiss in the massif are in fact an exotic metamorphic terrain thrusted over the Proterozoic basement complex at ca.
Improving U Th Pb Electron Microprobe mineral dating
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Keywords: Program, U-Th-Pb geochronology, Electron microprobe, Monazite. Page 4. 3. 1. INTRODUCTION. The electron probe microanalyser .
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. Rent this article via DeepDyve. Allaz, J. Microscopy and Microanalysis , 25 1 : 30—
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CHIME monazite dating using FE-EPMA equipped with R= mm spectrometers. Tuesday, 15 December Poster Hall (Moscone South). Kenji Shibata1.
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, ,
EPMA u-th-pb monazite dating of metamorphic rocks from the mogok metamorphic belt, central myanmar
Electron microprobe trace element analysis is a significant challenge. Due to the low net intensity of peak measurements, the accuracy and precision of such analyses relies critically on background measurements, and on the accuracy of any pertinent peak interference corrections. A linear regression between two points selected at appropriate background positions is a classical approach for electron probe microanalysis EPMA. However, this approach neglects the accurate assessment of background curvature exponential or polynomial , and the presence of background interferences, a hole in the background, or an absorption edge can dramatically affect the results if underestimated or ignored.
The acquisition of a quantitative wavelength-dispersive spectrometry WDS scan over the spectral region of interest remains a reasonable option to determine the background intensity and curvature from a fitted regression of background portions of the scan, but this technique can be time consuming and retains an element of subjectivity, as the analyst has to select areas in the scan which appear to represent background.
This paper presents a new multi-point background MPB method whereby the background intensity is determined from up to 24 background measurements from wavelength positions on either side of analytical lines.
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.
fluorine ever reported for monazite ( 소 wt %, EPMA, 소1σ), and U-Pb dating of monazite and its application to geological problems.
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, [