The geologic occurrence of monazite

Overstreet, William C.

doi:10.3133/pp530

Cited by 143 publications

(89 citation statements)

References 21 publications

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“…Several workers have stressed the effect of excess initial 23°Th on 2°~pb-23SU ages [13,15,23]. For SW-121 monazites analysed by TIMS (Table 1), the 2°6pb-23SU age is < 4 Ma greater than the 2°Tpb-235U age [19].…”

Section: Cp Dewolf Et Al / Earth and Planetary Science Letters 120mentioning

confidence: 99%

“…Second, the monazite inclusions show no textural or chemical evidence for resorption or overgrowths as would be expected if they were detrital and had been exposed to low grade metamorphic conditions where monazite may be unstable. Instead, they are typical in size (< 50 /zm), morphology (round to tabular with aspect ratio less than 2), and chemistry to monazites from other upper amphibolite grade terranes [13,15,21,27]. Third, the age range of the monazite inclusions overlaps the concordia U-Pb age of two zircons analysed by TIMS [19] which have a rounded, football-shaped, morphology indicative of metamorphic origin.…”

Section: Relation Of Inclusions To Garnet Growth and Closurementioning

confidence: 99%

“…On the other hand, monazite, (Ce,La,Nd) PO4, may be a more suitable phase for extracting in situ chronological information that relates to metamorphism. Monazite is a common accessory mineral in upper amphibolite and granulite facies rocks, particularly metapelites and leucocratic gneisses [12,13]. Several authors have suggested that monazite is unstable in rocks of pelitic composition below the amphibolite facies [12,14,15], though apparently detrital monazite has been identified in upper amphibolite paragneisses [14].…”

Section: Introductionmentioning

confidence: 99%

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A metamorphic history from micron-scale 207Pb/206Pb chronometry of Archean monazite

DeWolf

Belshaw

O’Nions

1993

Earth and Planetary Science Letters

163

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Ion microprobe measurements of Pb isotope ratios in monazites have been obtained, in situ, from thin sections using the Cambridge ISOLAB 120. Molecular interferences are sufficiently resolved at an RP of 6500 to allow 2°7pb/Z°6pb dating of monazite with precisions as low as 4-5 Ma (2~r). The results presented here provide important information on the chronological history of the Late Archean metamorphism of the Wind River Range, Wyoming (USA).Matrix monazites and monazite inclusions in garnets from a metapelite from the northern Wind River Range have been analysed by SIMS. In a previous study peak metamorphic conditions (T = 800°C; P = 8 + 1 kb *) were estimated using inclusion assemblages in garnets from this same sample. Isolated monazite inclusions in garnet yield 2°7pb/Z°6pb age estimates of 2781 + 6 to 2809 + 10 Ma. Those along fractures yield lower ages (2603-2687 Ma) which are similar to TIMS and SIMS ages of matrix monazites. A single large (500 /xm) monazite grain locally preserves growth zoning, but has a recrystallised core and a resorbed (recrystallised?) rim. Age estimates for these three regions are 2788 _+ 9 Ma, 2663 _+ 4 and 2523 + 6 Ma, respectively. Thus the inclusion assemblages of Sharp and Essene * may record peak metamorphic conditions at ca. 2.8 Ga, and indicate a phase of metamorphism that predates by over 100 Ma the emplacement of the Bridget Batholith, the major lithologic component of the northern Wind River Range.The analysed monazite grains appear to preserve ca. 300 Ma history, even within a single grain. Monazite inclusions in garnet that are fully armoured may provide estimates for the time of garnet growth, even in high grade terranes where most chronometers are reset. The age pattern preserved by the large monazite grain cannot be simply related to diffusion controlled closure. Instead, a chronology is preserved which can be related to the petrographic setting of individual grains through in situ analysis.

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Section: Cp Dewolf Et Al / Earth and Planetary Science Letters 120mentioning

confidence: 99%

Section: Relation Of Inclusions To Garnet Growth and Closurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A metamorphic history from micron-scale 207Pb/206Pb chronometry of Archean monazite

DeWolf

Belshaw

O’Nions

1993

Earth and Planetary Science Letters

163

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“…The elevated Th contents in the Kovela complex was most probably resulted from a complex, multi-stage process which involved primary magmatic crystallization and superimposed metamorphic-hydrothermal alteration. Förster and Harlov [69], Overstreet [70], Mohr [71] and Kelly et al [72] suggested that metamorphism may generate the breakdown of primary monazite to Th-rich mineral in the monazite-huttonite series by depletion of the Y, HREE, Ca and P content parallel with the relatively enrichment of Th, Si and LREE. …”

Section: Kovela Granitoid Complexmentioning

confidence: 99%

Geology and Mineralogy of Rare Earth Elements Deposits and Occurrences in Finland

et al. 2018

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Rare earth elements (REE) have critical importance in the manufacturing of many electronic products in the high-tech and green-tech industries. Currently, mining and processing of REE is strongly concentrated in China. A substantial growth in global exploration for REE deposits has taken place in the recent years and has resulted in considerable advances in defining new resources. This study provides an overview of the mineralogical and petrological peculiarities of the most important REE prospects and metallogeny of REE in Finland. There is a particularly good potential for future discoveries of carbonatite hosted REE deposits in the Paleozoic Sokli carbonatite complex, as well as in the Paleoproterozoic Korsnäs and Kortejärvi Laivajoki areas. This review also provides information about the highest known REE concentration in the alkaline intrusions of Finland in the Tana Belt and other alkaline rock hosted occurrences (e.g., Otanmäki and Katajakangas). Significant REE enrichments in hydrothermal alteration zones are also known in the Kuusamo Belt (Uuniniemi and Honkilehto), and occurrences of REE-rich mineralisation are also present in granite pegmatite bodies and greisens in central and southern Finland (Kovela monazite granite and the Rapakivi Granite batholith at Vyborg, respectively). REE minerals in all of the localities listed above were identified and analyzed by scanning electron microscopy (SEM) and electron microprobes (EMPs). In localities of northern and central Finland, both primary rock forming and epigenetic-hydrothermal REE minerals were found, namely phosphates (monazite-Ce, xenotime-Y), fluorcarbonates (bastnäsite-Ce, synchysite), and hydrated carbonates (ancylite-Ce), hydrated aluminium silicates (allanite-Ce, Fe-allanite, cerite, chevkinite), oxides (fergusonite, euxenite) and U-Pb rich minerals. The chondrite normalized REE concentrations, the La/Nd ratios and the REE vs. major element contents in several types of REE bearing minerals from prospects in Finland can be used to identify and define variable REE fractionation processes (carbonatites), as well as to discriminate deposits of different origins.

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“…Pb diffusion in the structure of monazite is very low under crustal environments (e.g., Cherniak et al, 2004, Gardés et al, 2007, and it presents relatively wide distribution in continental crust. Monazite appears as primary accessory phase in several igneous, average-to high-grade metamorphic, pegmatite, and diverse hydrothermal rocks; as a detritic phase, in psamitic sediments and rocks (e.g., Overstreet, 1967;Chang, Howie, Zussman, 1998). An unusual occurrence is described in lunar basalts by Lovering et al (1974).…”

Section: Introductionmentioning

confidence: 99%

Th-U-PbT dating by electron probe microanalysis, part I. monazite: analytical procedures and data treatment

Vlach

2010

Geol. USP, Sér. cient.

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Dating methodology by the electron probe microanalyser (EPMA) of (Th, U)-bearing minerals, highlighting monazite, acquired greater than ever importance in literature, particularly due to its superior spatial resolution, as well as versatility, which allow correlating petrological processes at times registered only in micro-scales in minerals and rocks with absolute ages. Although the accuracy is inferior to the one achieved with conventional isotopic methods in up to an order of magnitude, EPMA is the instrument that allows the best spatial resolution, reaching a few μm 3 in some conditions. Quantifi cation of minor and trace elements with suitable precision and accuracy involves the own instrumental and analytical set-ups and data treatment strategies, signifi cantly more rigorous when compared with those applied in conventional analyses. Th-U-Pb T dating is an example of these cases. Each EPMA is a unique machine as for its instrumental characteristics and respective automation system. In such a way, analytical procedures ought to be adjusted for laboratory specifi cities. The analytical strategies and data treatment adopted in the Electronic Microprobe Laboratory from Instituto de Geociências of Universidade de São Paulo, Brazil, with a JEOL JXA8600S EPMA, and a ThermoNoran-Voyager 4.3 automation system, are presented and compared with the ones used in other laboratories. The infl uence of instrumental factors and spectral overlaps on Th, U, and Pb quantifi cation is discussed. Applied procedures to interference correction, error propagation, data treatment, and fi nal chemical age presentation as well as to sampling and analyses are emphasized. Some typical applications are discussed, drawing attention to the most relevant aspects of electron microprobe dating.Keywords: Th-U-total Pb dating; Monazite; Microanalysis; Electron probe microanalyser (EPMA). RESUMOA metodologia de datação de minerais portadores de Th e/ou U com microssonda eletrônica (EPMA), com ênfase em monazita, adquiriu enorme importância em literatura, devido a sua alta resolução espacial e versatilidade, que permitem correlacionar processos petrológicos, por vezes registrados apenas em microescala em minerais e rocha, com idades absolutas. Embora a acurácia seja até uma ordem de grandeza inferior à alcançada com os métodos isotópicos convencionais, o EPMA é o equipamento que resulta na melhor resolução espacial, alcançando alguns poucos μm 3 sob algumas condições. A quantifi cação de elementos menores e em traços com precisão e acurácia adequadas envolve estratégias instrumentais, analíticas e de tratamento de dados específi cas e signifi cativamente mais rigorosas quando comparadas com as empregadas em análises convencionais. A datação Th-U-Pb T é um exemplo destes casos. Cada EPMA é um aparelho único em função de suas características instrumentais e sistema de automação e, desta forma, os procedimentos analíticos devem ser ajustados para as especifi cidades de cada laboratório. As estratégias analíticas e de tratamento de dados ado...

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The geologic occurrence of monazite

Abstract: Stream and beach deposits -268 Washington 269 West Virginia 270 Wyoming________ Fossil placers of Cambrian age 271 Fossil placers of Late Cretaceous age

Cited by 143 publications

References 21 publications

A metamorphic history from micron-scale 207Pb/206Pb chronometry of Archean monazite

A metamorphic history from micron-scale 207Pb/206Pb chronometry of Archean monazite

Geology and Mineralogy of Rare Earth Elements Deposits and Occurrences in Finland

Th-U-PbT dating by electron probe microanalysis, part I. monazite: analytical procedures and data treatment

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The geologic occurrence of monazite

Abstract: Stream and beach deposits __________ -268 Washington____________________________ 269 West Virginia__________________________ 270 Wyoming______________________________ Fossil placers of Cambrian age________ 271 Fossil placers of Late Cretaceous age__

Cited by 143 publications

References 21 publications

A metamorphic history from micron-scale 207Pb/206Pb chronometry of Archean monazite

A metamorphic history from micron-scale 207Pb/206Pb chronometry of Archean monazite

Geology and Mineralogy of Rare Earth Elements Deposits and Occurrences in Finland

Th-U-PbT dating by electron probe microanalysis, part I. monazite: analytical procedures and data treatment

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Abstract: Stream and beach deposits -268 Washington 269 West Virginia 270 Wyoming________ Fossil placers of Cambrian age 271 Fossil placers of Late Cretaceous age