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. Locating monazite grains can be done on standard geological thin sections via x-ray compositional mapping.
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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.
Abstract. Chemical U– Th – Pb dating of monazite from 12 schists throughout western and central Tasmania define a peak metamorphic age of ca Ma.
American Mineralogist ; 94 7 : — Granitoid monazite is a potential candidate for restitic origin because of its very low dissolution rates. They are interpreted as the result of late-magmatic replacement by a dissolution-reprecipitation mechanism. Garnet is mostly magmatic, with peritectic cores, and the granite is thought to have formed by biotite fluid-absent melting.
Chemical and textural relations enable the distinction of four types of monazite, which have been dated. Monazite types I—III are considered to be inherited from a metamorphic protolith, whereas type IV is interpreted to be the age of the latest magmatism. Shibboleth Sign In. OpenAthens Sign In. Institutional Sign In. Sign In or Create an Account.
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Canadian Journal of Earth Sciences
All publications more feeds DOI: BibTeX file. 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.
Investigation of the monazite chemical dating technique. CW Loehn. Virginia Tech, 4, Monazite Geochronology of the Madison Mylonite Zone and.
China has dominated the rare earth industry for thirty years and there is little indication this will change soon. Now, with a dramatic increase in demand for the rare earth magnets needed to drive electric transportation and produce clean energy solutions, the industrial world remains exposed to Chinese dominance. And the stakes are now higher than ever. Medallion has been developing an approach to achieve significant and low-cost production of these magnet metals by acquiring and processing monazite, a by-product rare earth mineral.
NdPr is the key input to magnets needed in the motors and generators of electric and hybrid vehicles, wind turbines, and a variety of other clean energy applications. These rare-earth magnets are 10 times the magnet strength for the same weight as conventional magnets, and there is currently no known substitute.
Enter monazite. For almost years, monazite has been processed using well-understood metallurgical methods. Monazite and bastnaesite the main rare-earth mineral in Chinese production are the only two rare-earth minerals to have ever successfully produced large commercial quantities of rare earths. Monazite is available as a by-product from North American, Australian and African heavy mineral-sands operators. Medallion believes that this is the best new non-Chinese source of NdPr and other rare earths.
Many of these heavy mineral-sand operations which are targeting titanium and zircon have ore reserves in excess of one billion tonnes of gross ore — this often translates to to years of production.
Electron Microprobe Dating of Monazite
Roberto F. Weinberg , Lauren C. Kylander-Clark, Raul Becchio.
lytical protocol for chemical dating of monazite using the. LEO VP scanning electron microscope (SEM) at the. Geological Survey of Norway (NGU).
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. It appears in a small amount as an accessory mineral in many igneous, metamorphic and sedimentary rocks. These two elements are what make this mineral suitable for radiometric dating.
Investigation of the monazite chemical dating technique
Our in-depth understanding of garnet ore characteristics and experience of production engineering have enabled us to produce superior quality of garnet abrasive for years. The finished products comply with international standards and achieve quotthree high and one lowquot high cleanliness, high dryness, high purity and low impurity content.
The strict structure and quality materials of the strong pressure ball machine make it realize excellent ball pressing effect to handle materials that are hard to be pressed or have high pressing standard. On the basis of domestic mills, fote raymond mill is produced.
Nondestructive chemical dating of young monazite using XRF: 1. Design of a mini-probe, age data for samples from the Central Alps, and.
Although uraninite is regarded as a rare accessory mineral, it is relatively abundant in leucogranitic rocks such as those found in the Himalayan orogen. We apply the U-Th-total Pb electron microprobe chemical dating method to a uraninite crystal from a ca. With this technique, we calculate a mean chemical date that is consistent with isotope-dilution thermal ionization mass spectrometry ID-TIMS U-Pb dates obtained from seven other uraninite grains and a monazite crystal from the same sample.
Monazite is a common accessory mineral in various metamorphic and magmatic rocks, and is widely used for U—Pb geochronology. However, linking monazite U—Pb ages with the PT evolution of the rock is not always straightforward. We investigated the behaviour of monazite in a metasedimentary sequence ranging from greenschist facies phyllites into upper amphibolites facies anatectic gneisses, which is exposed in the Eocene Chugach Metamorphic Complex of southern Alaska.
We investigated textures, chemical compositions and U—Pb dates of monazite grains in samples of differing bulk rock composition and metamorphic grade, with particular focus on the relationship between monazite and other REE-bearing minerals such as allanite and xenotime.
Original paper. Chemical U-Th-Pb dating of monazite by 3D-Micro X-ray fluorescence analysis with synchrotron radiation. Schmitz, Sylvia.
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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.
This paper outlines an advanced procedure involving the chemical Th–U–total Pb isochron method (CHIME) dating of monazite using a field–emission electron.
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.