Genesis of the volcanic-related Be-U-Mo Baiyanghe deposit, West Junggar (NW China), constrained by mineralogical, trace element and U-Pb isotope signatures of the primary U mineralisation

Bonnetti, Christophe; Liu, Xiaodong; Cuney, Michel; Wu, Bin; Li, Guanglai

doi:10.1016/j.oregeorev.2020.103921

Cited by 13 publications

(4 citation statements)

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“…The radiation-induced destruction of the uraninite structure (i.e., metamictization), as observed in Figure 3e,f, can cause U and Pb depletion and/or enrichment, which may result in significant uncertainties for the U-Pb isotopic ratios [84][85][86][87][88]. Moreover, radiogenic Pb loss due to post-crystallization alteration of uraninite [33] is a common feature that needs to be taken into account for U-Pb isotopic dating as it can lead to the determination of discordant and meaningless ages, and was encountered in various magmatic to hydrothermal U systems [78][79][80].…”

Section: Geochronological Constraint and Comparison With The Previous Ages Of Uraninitementioning

confidence: 99%

“…Minerals 2021, 11, x FOR PEER REVIEW 19 of 27 may result in significant uncertainties for the U-Pb isotopic ratios [84][85][86][87][88]. Moreover, radiogenic Pb loss due to post-crystallization alteration of uraninite [33] is a common feature that needs to be taken into account for U-Pb isotopic dating as it can lead to the determination of discordant and meaningless ages, and was encountered in various magmatic to hydrothermal U systems [78][79][80]. Information regarding the regional metamorphism of the Qinling Group is after [55,83], and the Caledonian magmatic event is after [44,56].…”

Section: Geochronological Constraint and Comparison With The Previous Ages Of Uraninitementioning

confidence: 99%

“…Hence, U/Th ratios (15 to 26) of uraninite from the Guangshigou deposit suggest a magmatic origin. In addition, their Th, REE, and Y enrichments indicate that they most likely crystallized from a fractionated high-K calc-alkaline pegmatitic magma [19,75,[78][79][80]. Indeed, when the high-K calc-alkaline melts become slightly peraluminous and/or when their temperature and Ca content has decreased sufficiently, monazite may become stable and Th-bearing accessory minerals start to fractionate to induce a decrease in Th/U ratios and allow uraninite crystallization [19], which is consistent with cogenetic monazite observed together with uraninite in the Guangshigou deposit (Figure 3c).…”

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SIMS U-Pb Dating of Uraninite from the Guangshigou Uranium Deposit: Constraints on the Paleozoic Pegmatite-Type Uranium Mineralization in North Qinling Orogen, China

et al. 2021

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Pegmatite-type uranium mineralization occurs in the Shangdan domain of the North Qinling Orogenic Belt, representing a significant uraniferous province. The Guangshigou deposit is the largest U deposit of the district. Within the North Qinling area, a series of Caledonian granitic igneous rocks intruded the Proterozoic metamorphic rocks of the Qinling Group in two magmatic stages: (i) the Early Silurian Huichizi granite that was derived from a low degree of partial melting of thickened lower basaltic crust combined with mantle-derived materials following the subduction of the Shangdan Ocean; and (ii) the Late Silurian–Early Devonian Damaogou granite and associated pegmatites derived from the same source but emplaced in a late tectonic post-collisional extension environment. In the Guangshigou deposit, the U mineralization mainly occurs as uraninite disseminated in U-rich granitic biotite pegmatites, which formed by assimilation-fractional crystallization magmatic processes. Petrographic observations showed evidence for coeval crystallization of uraninite and other rock-forming minerals of the host pegmatite including quartz, feldspar, biotite, zircon, monazite, apatite, and xenotime. In addition, the low U/Th ratios (~19) and Th, REE, and Y enrichments characterized a magmatic origin for uraninite, which was likely derived from fractionated high-K calc-alkaline pegmatitic magma that experienced various degrees of crustal material contamination. In situ U-Pb isotopic dating performed by Secondary-Ion Mass Spectrometry (SIMS) on uraninite from the Guangshigou deposit yielded a crystallization age of 412 ± 3 Ma, which is concomitant (within errors) with the emplacement age of the host pegmatite (415 ± 2 Ma) and constrained the U ore genesis to the Early Devonian, which corresponds to the late Caledonian post-collisional extension in the North Qinling area. Uraninite then experienced various degrees of metamictization and/or post-Caledonian hydrothermal alteration characterized by an alteration rim associated with coffinite, chlorite and limonite. Finally, the characteristics of the pegmatite-related Guangshigou deposit exhibiting Th-rich uraninite which was the product of assimilation-fractional crystallization of pegmatitic magma defined a model significantly different than the one established for the world-class Rössing deposit characterized by Th-poor uraninite hosted in alaskite dykes formed by low degree of partial melting of U-rich metasediments.

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Section: Geochronological Constraint and Comparison With The Previous Ages Of Uraninitementioning

confidence: 99%

Section: Geochronological Constraint and Comparison With The Previous Ages Of Uraninitementioning

confidence: 99%

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SIMS U-Pb Dating of Uraninite from the Guangshigou Uranium Deposit: Constraints on the Paleozoic Pegmatite-Type Uranium Mineralization in North Qinling Orogen, China

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“…Due to the radiogenic Pb loss in uraninite related to various degrees of post-crystallization alteration, younger and dispersive ages are commonly obtained on altered uraninite [16], hence preventing constraints on hydrothermal overprinting episodes. Moreover, U-Th-Pb chemical dating does not allow measuring common Pb contents, which could induce older age estimates on uraninite (e.g., [63]). One way to overcome this limitation is to apply statistical age clustering obtained by U-Th-Pb isotopic or chemical dating to their alteration or hydrothermal products (e.g., hydrothermal coffinite, uraninite and uranothorite).…”

Section: Timing Of Uranium Mineralization and Post-crystallization Alteration In The Guangshigou Biotite Pegmatitementioning

confidence: 99%

Uraninite from the Guangshigou Pegmatite-Type Uranium Deposit in the North Qinling Orogen, Central China: Its Occurrence, Alteration and Implications for Post-Caledonian Uranium Circulation

Bonnetti

Liu

et al. 2021

Minerals

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The Guangshigou deposit is the largest pegmatite-type uranium deposit in the Shangdan domain of the North Qinling Orogenic Belt, which is characterized by the enrichment of uraninite hosted in biotite granitic pegmatites. At Guangshigou, uraninite commonly occurs as mineral inclusions in quartz, K-feldspar and biotite or in interstices of these rock-forming minerals with magmatic characteristics (e.g., U/Th < 100, high ThO2, Y2O3 and REE2O3 contents and low concentrations of CaO, FeO and SiO2). It crystallized at 407.6 ± 2.9 Ma from fractionated calc-alkaline high-K pegmatitic melts under conditions of 470–700 °C and 2.4–3.4 kbar as deduced by the compositions of coexisting peritectic biotite. The primary uranium mineralization took place during the Late Caledonian post-collisional extension in the North Qinling Orogen. After this magmatic event, uraninite has experienced multiple episodes of fluid-assisted metasomatism, which generated an alteration halo of mineral assemblages. The alteration halo (or radiohalo) was the result of the combined effects of metamictization and metasomatism characterized by an assemblage of goethite, coffinite and an unidentified aluminosilicate (probably clay minerals) around altered uraninite. This fluid-assisted alteration was concomitant with the albitization of K-feldspar subsequently followed by the coffinitization of uraninite during the major period of 84.9–143.6 Ma, as determined by U-Th-Pb chemical ages. Further investigations revealed that the metasomatic overprinting on uraninite initially and preferentially took place along microcracks or cavities induced by metamictization and promoted their amorphization, followed by the release of U and Pb from structure and the incorporation of K, Ca and Si from the fluids, finally resulting in various degrees of uraninite coffinitization. The released U and Pb were transported by alkali-rich, relatively oxidizing fluids and then re-precipitated locally as coffinite and an amorphous U-Pb-rich silicate under low to moderate temperature conditions (85–174 °C). The compositional changes in primary uraninite, its structure amorphization together with the paragenetic sequence of secondary phases, therefore, corroborate a combined result of intense metamictization of uraninite and an influx of alkali–metasomatic fluids during the Late Mesozoic Yanshanian magmatic event in the region. Hence, the remobilization and circulation of uranium in the North Qinling Orogen was most likely driven by post-Caledonian magmatism and hydrothermal activities related to large-scale tectonic events. In this regards, Paleozoic pegmatite-type uranium mineralization may represent a significant uranium source for Mesozoic hydrothermal mineralization identified in the Qinling Orogenic Belt.

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Granite-related high-temperature hydrothermal uranium mineralisation: evidence from the alteration fingerprint associated with an early Yanshanian magmatic event in the Nanling belt, SE China

et al. 2022

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Genesis of the volcanic-related Be-U-Mo Baiyanghe deposit, West Junggar (NW China), constrained by mineralogical, trace element and U-Pb isotope signatures of the primary U mineralisation

Cited by 13 publications

References 73 publications

SIMS U-Pb Dating of Uraninite from the Guangshigou Uranium Deposit: Constraints on the Paleozoic Pegmatite-Type Uranium Mineralization in North Qinling Orogen, China

SIMS U-Pb Dating of Uraninite from the Guangshigou Uranium Deposit: Constraints on the Paleozoic Pegmatite-Type Uranium Mineralization in North Qinling Orogen, China

Uraninite from the Guangshigou Pegmatite-Type Uranium Deposit in the North Qinling Orogen, Central China: Its Occurrence, Alteration and Implications for Post-Caledonian Uranium Circulation

Granite-related high-temperature hydrothermal uranium mineralisation: evidence from the alteration fingerprint associated with an early Yanshanian magmatic event in the Nanling belt, SE China

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