Results of chemical dating of monazite from the Talnakh economic intrusion (Russia)
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.
Monazite chemical dating shows that –Ma monazites predominate in the Pliocene and –Ma monazites in the Quaternary, indicating a great.
Economic copper, nickel, and platinum-group element PGE deposits are associated with the Talnakh ultramafic—mafic intrusion of the Noril’sk Province in the northwestern part of the Siberian Platform. The results of the chemical Th—U—Pb dating of monazite from the ore-bearing melanotroctolites of the Talnakh intrusion are presented. The isotope-geochemical features of monazite are compared with zircon, sulfides, and baddeleyite.
Results of chemical dating of monazite from the Talnakh economic intrusion Russia. N2 – Economic copper, nickel, and platinum-group element PGE deposits are associated with the Talnakh ultramafic—mafic intrusion of the Noril’sk Province in the northwestern part of the Siberian Platform. AB – Economic copper, nickel, and platinum-group element PGE deposits are associated with the Talnakh ultramafic—mafic intrusion of the Noril’sk Province in the northwestern part of the Siberian Platform.
Widoczny [Schowaj] Abstrakt. Tables, graphs and references. Fluid-induced dis-turbance of the monazite Th—Pb chronometer: In situ dating and element mapping in pegmatites from the Rhodope Greece, Bul-garia. Chemical Geology : , DOI The half-lives of uranium and thorium Chemi-cal Geology : , DOI
Proterozoic. Keywords U-Pb dating · Monazite · Southern India · rim shows oscillatory zoning of chemical composition and exclusively.
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. User Tools. Sign In. Advanced Search.
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The results of the chemical Th–U–Pb dating of monazite from the ore-bearing melanotroctolites of the Talnakh intrusion are presented. The isotope-geochemical.
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.
Kawakami, N. Nakano , F. Higashino, T. Hokada, Y. Osanai , M.
We investigated textures, chemical compositions and U–Pb dates of monazite Monazite grains were separated for U–Pb SHRIMP dating from.
There were press releases posted in the last 24 hours and , in the last days. Instead of piling into vans and hitting the road, more than 30 attendees from the U. Atomic Energy Commission during the Cold War. Army Corps of Engineers. The site consists of a acre chemical plant where DuPont began uranium operations in Grace conducted thorium-processing operations of monazite sands at the facility in the late s under contract with the U.
Atomic Energy Commission. Remediation activities are continuing and collaboration with the property owner will be pivotal when the site transfers to LM.
Canadian Journal of Earth Sciences
Geochronology is the science of providing ages of events in the history of the Earth and extraterrestrial material and of determining the temporal rates of geological processes by using a number of different dating methods. The ages can be absolute e. Most absolute dating methods rely on the analysis of radioactive isotopes and their radiogenic decay products. A number of radioactive isotopes from different elements, such as uranium, thorium, rhenium, samarium, lutetium, rubidium and potassium are used for this purpose.
In these prograde occur- rences, the chemical reactions that produce it are uncertain, but the metamorphic crystallization of monazite must involve a liberation of.
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. Download to read the full article text.
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The main limitation of chemical dating of monazite by EMP, aside from the The feasibility of determining chemical ages of young monazites containing only a.
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