Textural and geochemical discrimination between xenotime of different origin in the Archaean Witwatersrand Basin, South Africa

Kositcin, N; McNaughton, Neal J.; Griffin, Brendan; Fletcher, Ian R.; Groves, David; Rasmussen, Birger

doi:10.1016/s0016-7037(02)01169-9

Cited by 122 publications

(41 citation statements)

References 26 publications

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“…Occasionally, some grains exhibit irregular zonation with a patchy and mottled aspect, alternating between darker and brighter domains. According to Kositcin et al (2003), this texture depicts variable degrees of substitution of HREE, U and Th during magmatic evolution. Zonation within the grains is often closely associated with thorite inclusions, displayed as bright circular white dots.…”

Section: Texture and Composition Of Xenotime-(y)mentioning

confidence: 99%

Occurrence and behavior of monazite-(Ce) and xenotime-(Y) in detrital and saprolitic environments related to the Serra Dourada granite, Goiás/Tocantins State, Brazil: Potential for REE deposits

Santana

Wall

Botelho

2015

Journal of Geochemical Exploration

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The mode of occurrence, mobility and fractionation of REE have been investigated in the geochemical context of the Serra Dourada Granite, an A-type granitic body located in northern Goiás State, Brazil. Several analyses were performed to best characterize each mode of occurrence of REE, from fresh rock to its products of alteration such as the saprolite, placers and clayish horizon. In the fresh rock it was found that the REE budget is related to monazite-(Ce), xenotime-(Y), bastnäsite and allanite. Resistant monazite-(Ce) and xenotime-(Y) withstand fluvial transportation and are concentrated in placers whithin the massif, whereas bastnäsite and allanite do not. The alluvial sediments contain up to 0.87wt% monazite-(Ce) and 0.46wt% xenotime-(Y). Considering only the heavy minerals, monazite-(Ce), zircon and ilmenite represent 60-80% of the total variability, being monazite-(Ce) and xenotime-(Y) the most important REE carriers. The same minerals are also present, although in lower amounts, in the saprolite. Both qualitative and quantitative electron probe microanalysis were carried out in detrital monazite-(Ce) and xenotime-(Y) to assess their main features and composition. Monazite-(Ce) REE contents are 60wt% in average, whilst REE contents in detrital xenotime-(Y) are 55 wt% in average. Low totals are ascribed to the alteration of the minerals caused by the presence of both organic and inorganic ligands present in the system. The results support the idea that REE are mobile under supergene conditions and during granite weathering, tending to be higher and more fractionated towards the products of alteration (saprolite, alluvial sediments and clayish horizon). REE2O3 contents in the fresh granite, saprolite, alluvial sediments and clayish horizon are 0.07, 0.21, 1.2 and 0.11wt% respectively, the clayish horizon being HREE-selective. Placer deposits and the clayish horizon tend to occur in low-slope areas within the Massif, where deposition and accumulation is more favorable. The saprolite occurs preferably in high-slope areas formed in situ at the expense of the granite. The placer deposits could be exploited, but their occurrence is more restricted and local. The saprolite has the advantage of covering extensive areas widely distributed over the granite. Currently a private company, the Serra Verde Mining, posses the mining claims in the area to exploit the REE associated with the saprolite, under the model of ion-adsorption type deposits.

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Section: Texture and Composition Of Xenotime-(y)mentioning

confidence: 99%

Occurrence and behavior of monazite-(Ce) and xenotime-(Y) in detrital and saprolitic environments related to the Serra Dourada granite, Goiás/Tocantins State, Brazil: Potential for REE deposits

Santana

Wall

Botelho

2015

Journal of Geochemical Exploration

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“…This mineral is enriched in rare earth elements (REE), and is an ideal candidate for U-Pb dating because of its high content of U and negligible content of common Pb. Currently, in situ dating of xenotime is commonly conducted by ion microprobe [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], which can yield precise and accurate ages. However, the expense of this instrumentation hinders the wide application of this technique.…”

mentioning

confidence: 99%

In situ U-Pb dating of xenotime by laser ablation (LA)-ICP-MS

Liu

Guo

et al. 2011

Chin. Sci. Bull.

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Xenotime is an ideal mineral for U-Th-Pb isotopic dating because of its relatively high U and Th contents, but typically low concentration of common Pb. These characteristics, and the fact that it is widespread throughout various types of rocks, suggest that the U-Th-Pb dating of xenotime has broad applications. Studies of U-Pb dating on xenotime by ion microprobe (such as SHRIMP) have increased in recent years, whereas studies by laser ablation (LA)-ICP-MS are still rare. In this study, we developed a technique for U-Pb dating of xenotime using the 193 nm ArF laser-ablation system and Agilent 7500a Q-ICP-MS. To evaluate the reliability of our method, a xenotime standard, BS-1, was analyzed and calibrated against another xenotime standard, MG-1. The weighted mean 206 Pb/ 238 U ages of 510.1 ± 5.2 Ma (2 n = 21), 509.8 ± 4.3 Ma (2 n = 21) and 510.0 ± 4.6 Ma (2n = 21) were obtained using beam diameters of 16, 24 and 32 m, respectively. These ages are identical to those determined by ID-TIMS method (weighted mean 206 Pb/ 238 U age of 508.8 ± 1.4 Ma), which supports the reliability of our LA-ICP-MS method. We also analyzed xenotimes in leucogranites from South Tibet and granites from Xihuashan in southern China, and obtained accurate and precise ages. Nevertheless, we observed systematic differences in Pb/U fractionation among xenotime, monazite and zircon. The matrix-effect resulted in either under-correction or over-correction of fractionation, and thus led to inaccurate ages. Thus, a matrix-matched material is required for U-Pb dating of xenotime by LA-ICP-MS.

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“…The high content of thorium in examined samples is characteristic for monazite of magmatic origin (Zhu, O'Nions 1999). The concentration of HREE's, U and Th, as well as numerous uranothorite inclusions in examined xenotime, indicates a magmatic origin of xenotime (Kositcin et al 2003). The xenotime HREE to Y ratio is typical for granitoids of S or I type (Förster 1998), which falls into the existing classification of adjacent magmatic plutons (Schwartz et al 1995).…”

Section: Discussionmentioning

confidence: 85%