These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric. Find more information on the Altmetric Attention Score and how the score is calculated. The U—Pb geochronologic analysis of accessory minerals has played an important role in Earth and solar system science in constraining the ages of a wide variety of rocks and minerals.
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.
zircon and monazite samples demonstrate that the SS-LA-ICPMS method is capable of SS-LA-ICPMS FC1 date is too old by Ma (%), which we attribute.
Research article 03 Apr Correspondence : Emmanuelle Ricchi emmanuelle. Thorium—lead Th-Pb crystallization ages of hydrothermal monazites from the western, central and eastern Tauern Window provide new insights into Cenozoic tectonic evolution of the Tauern metamorphic dome. Growth domain crystallization ages range from Fissure monazite ages largely overlap with zircon and apatite fission track data.
Besides tracking the thermal evolution of the Tauern dome, monazite dates reflect episodic tectonic movement along major shear zones that took place during the formation of the dome. Moreover, these two phases overprint earlier phases of fissure formation. In situ thorium—lead Th-Pb dating of hydrothermal fissure monazite- Ce in the following simply monazite has recently been demonstrated to be a reliable method for dating tectonic activity under retrograde metamorphic conditions Bergemann et al.
These studies conducted through the entire Alpine orogenic belt allowed constraining tectonic activity in relation with exhumation and fault activity under retrograde lower greenschist to sub-greenschist facies metamorphic conditions.
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.
We applied these techniques to accessory phases hosted in the (U)HP rocks of the Seve Nappe Complex (SNC), Scandinavian Caledonides (Fig.
Monazite rim formation was facilitated via dissolution—reprecipitation of Neoproterozoic monazite. The monazite rims record garnet growth as they are depleted in Y 2 O 3 with respect to the Neoproterozoic cores. Rims are also characterized by relatively high SrO with respect to the cores. Results of the zircon depth-profiling revealed igneous zircon cores with crystallization ages typical for SNC metasediments. These results show that both monazite and zircon experienced dissolution—reprecipitation under high-pressure conditions.
Caledonian monazite formed coeval with garnet growth during subduction of the Vaimok Lens, whereas zircon rim formation coincided with monazite breakdown to apatite, allanite and clinozoisite during initial exhumation. To understand the subduction—exhumation dynamics of continental lithosphere that reached ultra- high pressure [ U HP] depths, we must extract information regarding the timing and conditions of prograde, peak and retrograde metamorphism. Problematically, continental lithosphere that experienced U HP metamorphism is commonly overprinted by exhumation-related structures and retrogressive metamorphism.
Moreover, peak-temperatures of rocks that experienced U HP metamorphism are typically reached during decompression. Robust geochronometers, such as monazite and zircon, are refractory minerals that can retain their geochronological and geochemical signatures through high temperature conditions, retrogressive metamorphism and deformation e. Engi ; Foster et al.
Monazite is a light rare earth element LREE -bearing phosphate mineral. Crystals typically contain distinct chemical domains, each of which represent successive growth thru geologic history. Electron microprobe analysis can characterize the geometry and U-Th- total Pb age for each domain. This kind of data allow the growth of monazite to be related to geologic events affecting the host rock. Monazite is common in pelitic and psammitic metamorphic rocks at greenschist facies and above where it is often recognized as inclusions in porphyroblasts but may also be in direct connection with the matrix.
This paper outlines an advanced procedure involving the chemical Th-U-total Pb isochron method (CHIME) dating of monazite using a field-emission electron.
Passarelli; Miguel A. Basei; Oswaldo Siga Jr. Sproesser; Vasco A. It provides reliable and accurate results in age determination of superposed events. However, the open-system behavior such as Pb-loss, the inheritance problem and metamictization processes allow and impel us to a much richer understanding of the power and limitations of U-Pb geochronology and thermochronology. Since , the Interdepartmental Laboratory of Isotopic Geology focus the study of the Earth’s geologic processes, dealing with themes such as plate tectonics, plutonism, volcanism, sedimentary rocks, tectono-thermal evolution, and more recently environmental studies.
CPGeo gathers modern laboratories installed inan area of m 2 and is equipped with seven mass spectrometers for radiogenic and stable isotope analysis. The method is considered one of the most precise among the isotopic techniques available for U-Th-Pb geochronology of accessory minerals, because it is relative insensitive to chemical yields or mass spectrometric sensitivity Parrish and Noble , and is therefore largely used by the scientific community.
According to Kosler and Sylvester the in situ U-Pb geochronology was introduced ca.
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.
In particular, whereas monazite dating by a variety of techniques (isotope dilution mass spectrometry, SIMS, electron microprobe dat- ing, and LA-ICPMS) has.
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.
Investigation of the monazite chemical dating technique
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.
Method Overview. 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.
Symposium on Geol. Resources of Madagascar – A good example of the usefulness of the in-situ dating method. Madagascar displays a huge portion of the lower crust and its study is fundamental for the understanding of the evolution of this part of the crust. Unfortunately, our knowledge of this domain is limited. At this time, numerous works structural, geochemical, petrological are in progress in Madagascar, but there are only a few geochronological data. In this context, the fast, non-expensive, reliable electron microprobe monazite dating method, using the Th-U-Pb system, is particularly efficient to obtain many ages see Montel et al.
We applied this method in Madagascar. In the granulitic basement Southern Madagascar, three large areas can be distinguished, from East to West : the Androyan, the Bekily and the Vohibory blocks, separated by transcurrent shear zones : the Bongolava-Ranotsara, the Beraketa and the Ampanihy shear zones. This geometry is interpreted as the result of crustal extrusion towards the S-SE of the South of the island during the Mozambican collision.
Martelat et al. Results are consistent with available datings carried out by conventional methods Andriamarofahatra et al. We suggest that, in the southern part of the island, the peak of the HT metamorphism at Ma is followed by a general cooling until Ma.