No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Late Triassic U-bearing and barren granites in the Miao'ershan batholith, South China: Petrogenetic discrimination and exploration significance
Abstract
The Miao'ershan uranium ore district is one of the most important granite-hosted uranium producers in South China. There are several Triassic granite plutons in the Miao'ershan batholith, but uranium ore deposits mainly occur within the Douzhashan granitic body. Precise zircon U–Pb dating indicated that these Triassic granite plutons were emplaced during 204 to 215 Ma. The Douzhashan U-bearing granite lies in the central part of the Miao'ershan batholith, and has higher U contents (8.0 to 26.1 ppm, average 17.0 ppm) than the nearby Xiangcaoping granite (5.0 to 9.3 ppm, average 7.0 ppm) and the Yangqiaoling granite (6.4 to 18.3 ppm, average 11.5 ppm) in the south part of the batholith. The Douzhashan granite is composed of medium-grained two-mica granite, whereas the Xiangcaoping and Yangqiaoling granites are composed of porphyritic biotite granite. Both the Xiangcaoping and Douzhashan granites have high A/CNK ratios (> 1.10), high (87Sr/86Sr)i ratios (> 0.720) and low εNd(t) values (− 11.3 to − 10.4), suggesting that they belong to strongly peraluminous S-type granites. The Douzhashan granite has low CaO/Na2O ratios, high Rb/Sr and Rb/Ba ratios, indicating a partial melting origin of clay-rich pelitic rocks. In contrast, the Xiangcaoping granite formed from clay-poor psammite-derived melt. The Yangqiaoling granite shows different geochemical characteristics with the Douzhashan and Xiangcaoping granites, indicating a different magma source. The Yangqiaoling granite has higher εNd(t) of − 9.4 to − 8.3 and variable A/CNK values from 0.98 to 1.19, suggesting a mixture source of meta-sedimentary rocks and meta-igneous rocks. Crystallization fractionation is not the main mechanism for U enrichment in the Douzhashan granite. We suggest that U-rich pelitic rock sources may be the key factor to generate peraluminous U-bearing granites in South China. Searching for those granites which are reduced, strongly peraluminous and were derived from U-rich pelitic rocks, is the most effective way for exploring granite-hosted U deposits.
... Fault and Fold structures mainly trend NE-NNE. The batholith is mainly composed of Early Paleozoic and Late Triassic granitic rocks with subordinate Neoproterozoic and Late Jurassic ones (Che et al., 2019;Cheng et al., 2018;Huang et al., 2019;Tian et al., 2020;Zhang, 2021;Zhao et al., 2013Zhao et al., , 2014Zhao et al., , 2016Zhu et al., 2020). The Neoproterozoic granite in the northwestern margin of this batholith consists of the Maoerjie, Yexijiang and Baomuping intrusions and is mainly biotite granite porphyry. ...
... (1972)). Formation ages of granitic rocks and related W deposits are from references (Chen et al., 2016Cheng et al., 2018;Huang et al., 2019;Li et al., 2022a;Lin, 2016;Wu et al., 2012;Yang et al., 2014;Zhang, 2015;Zhang et al., 2015;Zhao et al., 2013Zhao et al., , 2014Zhao et al., , 2016Zhu et al., 2020). Abbreviation: Mol = molybdenite, Sch = scheelite, Ttn = titanite, Zrn = zircon. ...
... (1972)). Formation ages of granitic rocks and related W deposits are from references (Chen et al., 2016Cheng et al., 2018;Huang et al., 2019;Li et al., 2022a;Lin, 2016;Wu et al., 2012;Yang et al., 2014;Zhang, 2015;Zhang et al., 2015;Zhao et al., 2013Zhao et al., , 2014Zhao et al., , 2016Zhu et al., 2020). Abbreviation: Mol = molybdenite, Sch = scheelite, Ttn = titanite, Zrn = zircon. ...
Early Paleozoic Sn mineralization is rarely reported in South China. We carried out the detailed studies of deposit geology, cassiterite U-Pb ages, muscovite geochemistry and H-O isotopes on the Early Paleozoic Lijia Sn deposit in South China to constrain its genesis. The Lijia Sn deposit is hosted in the Yuechengling granitic batholith and characterized by greisen-type and quartz vein-type mineralization. Four stages of alteration and veining are recognized according to mineral assemblages and crosscutting relationships: pre-ore tourmalinization and silicification alteration of the Lijia granite (stage I), cassiterite-tourmaline-quartz vein and associated cassiterite greisen (stage II), and post-ore calcite-quartz-fluorite vein and calcite veinlet (stage III and IV, respectively). Two generations of the cassiterite in the cassiterite greisen, identified by cathodoluminescence imaging, yield the U-Pb concordant ages of 430.5±3.7 Ma and 428±2.2 Ma, respectively. The zircon U-Pb ages and geochemical features of the Lijia granite as well as the characteristics of alteration and mineralization indicate that tin mineralization is related with the Lijia granite. H-O isotopic compositions of the quartz from the Lijia granite reveal that the magmatic fluids have the δ¹⁸O values of 10.6–10.7‰ and the δD values of -57‰ to -62‰. The ore-forming fluids (δ¹⁸O 6.5–7.4‰, δD -64‰ to -69‰) responsible for cassiterite precipitation are derived from the mixing of magmatic fluids with minor meteoric water whereas more meteoric water is involved in the post-ore calcite-quartz-fluorite vein stage. Based on mineral assemblages, internal textures and chemical compositions, muscovite is divided into four generations from early to late: the Mus 1 and Mus 2 in the cassiterite greisen, the Mus 3 in the cassiterite-tourmaline-quartz vein and the Mus 4 in the phyllic alteration in the stage III. From the Mus 1 to the Mus 3, muscovite Rb, Cs, Zn, Li, V, Sc and Ga contents gradually decrease whereas boron shows an increasing trend, which might have been caused by the successive precipitation of hydrothermal minerals such as muscovite. Significantly higher Sr and Ba contents of the Mus 2 than the Mus 1 are likely related with the decomposition of the K-feldspar and plagioclase in the host granites. The combination of the precipitation of the early mineral phases, the decomposition of K-feldspar and the involvement of a large amount of meteoric water gives rise to the decrease of W, Sn, B, Rb, Cs and Sr contents and the increase of Ba, Ti, Mg, Li, Sc, V, Cr, Ga, Nb and Ta contents of the Mus 4 in the stage III. A key mechanism responsible for the formation of the Lijia Sn deposit is the interaction between the ore-forming fluids and the host granite. This study confirms the Early Paleozoic tin mineralization event in South China.
... Granite-related uranium deposits in South China are mainly distributed in the Cathaysia block and the Jiangnan orogen ( Fig. 1), especially in the Motianling, Miao'ershan, Zhuguangshan, Guidong, Taoshan, Jiuyishan, Liuchen, Guidong, Aigao, and Dafuzu batholiths (Zhao, K.D., et al., 2011(Zhao, K.D., et al., , 2016Zhang et al., 2018). Among these batholiths, a close spatial and genetic relationship of uranium mineralization with granites is displayed by several intrusions, such as the Daguzhai granite in the Taoshan batholith (Zhao, K.D., et al., 2011), Xiazhuang granite in the Guidong batholith (Chen et al., 2012), Douzhashan granite in the Miao'ershan batholith (Zhao et al., 2016), and Changjiang and Youdong granites in the Zhuguangshan batholith ; these are all known as U-bearing granites (Zhao, K.D., et al., 2011(Zhao, K.D., et al., , 2016. ...
... Granite-related uranium deposits in South China are mainly distributed in the Cathaysia block and the Jiangnan orogen ( Fig. 1), especially in the Motianling, Miao'ershan, Zhuguangshan, Guidong, Taoshan, Jiuyishan, Liuchen, Guidong, Aigao, and Dafuzu batholiths (Zhao, K.D., et al., 2011(Zhao, K.D., et al., , 2016Zhang et al., 2018). Among these batholiths, a close spatial and genetic relationship of uranium mineralization with granites is displayed by several intrusions, such as the Daguzhai granite in the Taoshan batholith (Zhao, K.D., et al., 2011), Xiazhuang granite in the Guidong batholith (Chen et al., 2012), Douzhashan granite in the Miao'ershan batholith (Zhao et al., 2016), and Changjiang and Youdong granites in the Zhuguangshan batholith ; these are all known as U-bearing granites (Zhao, K.D., et al., 2011(Zhao, K.D., et al., , 2016. ...
... Granite-related uranium deposits in South China are mainly distributed in the Cathaysia block and the Jiangnan orogen ( Fig. 1), especially in the Motianling, Miao'ershan, Zhuguangshan, Guidong, Taoshan, Jiuyishan, Liuchen, Guidong, Aigao, and Dafuzu batholiths (Zhao, K.D., et al., 2011(Zhao, K.D., et al., , 2016Zhang et al., 2018). Among these batholiths, a close spatial and genetic relationship of uranium mineralization with granites is displayed by several intrusions, such as the Daguzhai granite in the Taoshan batholith (Zhao, K.D., et al., 2011), Xiazhuang granite in the Guidong batholith (Chen et al., 2012), Douzhashan granite in the Miao'ershan batholith (Zhao et al., 2016), and Changjiang and Youdong granites in the Zhuguangshan batholith ; these are all known as U-bearing granites (Zhao, K.D., et al., 2011(Zhao, K.D., et al., , 2016. ...
Uraninite is the main contributor to the bulk-rock uranium concentration in many U-rich granites and is the most important uranium source for granite-related uranium deposits. However, detailed textural and compositional evolution of magmatic uraninite in granites during alteration and associated uranium mobilization have not been well documented. In this study, textures and geochemistry of uraninites from the Zhuguangshan batholith (South China) were investigated by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The geochemical data indicate that the Longhuashan and Youdong plutons are peraluminous leucogranite, the Changjiang pluton is highly fractionated high-K calc-alkaline granite, and the Jiufeng pluton belongs to a high-K calc-alkaline association.
Uraninites from the Longhuashan and Youdong granites have lower concentrations of ThO2 (0.9–4.0 wt %) and rare earth elements (REE)2O3 (0.1–1.0 wt %) than those from the Changjiang and Jiufeng granites (ThO2 = 4.4–7.6 wt %, REE2O3 = 0.7–5.1 wt %). Uraninites observed in the Longhuashan, Youdong, Changjiang, and Jiufeng granites yielded chemical ages of 223 ± 3, 222 ± 2, 157 ± 1, and 161 ± 2 Ma, respectively. The samples (including altered and unaltered) collected from the Longhuashan, Youdong, and Changjiang granites are characterized by highly variable whole-rock U concentrations of 6.9 to 44.7 ppm and Th/U ratios of 0.9 to 7.0, consistent with crystallization of uraninite in these granites being followed by uranium leaching during alteration. Alteration of uraninite, indicated by altered domains developing microcracks and appearing darker in backscattered electron (BSE) images compared to unaltered domains, results in the incorporation of Si and Ca and mobilization of U. In contrast, the least altered samples of the unmineralized Jiufeng granite have low U concentrations (5.3–16.4 ppm) and high ΣREE/U (13.6–49.4) and Th/U ratios (2.1–5.6), which inhibit crystallization of uraninite, as its crystallization occurs when the U concentration is high enough to exceed the substitution capacity of other U-bearing minerals. These results indicate that the Longhuashan, Youdong, and Changjiang granites were favorable uranium sources for the formation of uranium deposits in this area. This study highlights the potential of uraninite alteration and geochemistry to assist in deciphering uranium sources and enrichment processes of granite-related uranium deposits.
... Granite-hosted uranium deposits represent the most significant deposit type in this region (Cai et al., 2015;Zhang et al., 2019a). Most of the uranium deposits of the SCUP are spatially associated with Triassic and Jurassic U-rich granites (Zhao et al., 2011a(Zhao et al., , 2016Chen et al., 2012;Zhang et al., 2017aZhang et al., , 2018Chi et al., 2020), which are considered to represent the main metal source of the deposits (e.g., Min et al., 1999;Hu et al., 2012;Bonnetti et al., 2018;Qiu et al., 2018). However, Zhang et al. (2017b), Zhang et al., 2019b suggest that the granites in the South Zhuguang uranium ore field (South China) merely promote favorable conditions for U precipitation rather than representing the main metal sources of the deposits. ...
... Granite-hosted uranium deposits in South China mainly occur in the Motianling, Miao'ershan, Zhuguangshan, Guidong, Taoshan, Jiuyishan, Liuchen, Guidong, Aigao, and Dafuzu batholiths ( Fig. 1; Zhang and Zhang, 1991). Available data both from research and mineral exploration reveal that such deposits are genetically related to specific granite plutons, commonly termed U-bearing granites (Zhang and Zhang, 1991;Zhang, 1996;Zhao et al., 2011aZhao et al., , 2016. The Miao'ershan granitic batholith is one of the most important uranium provinces in South China (Zhao et al., 2016). ...
... Available data both from research and mineral exploration reveal that such deposits are genetically related to specific granite plutons, commonly termed U-bearing granites (Zhang and Zhang, 1991;Zhang, 1996;Zhao et al., 2011aZhao et al., , 2016. The Miao'ershan granitic batholith is one of the most important uranium provinces in South China (Zhao et al., 2016). There are several economical granite-hosted uranium deposits such as Shazijiang, Zhangjia, Hongqiao, Menggongjie, and Shuanghuajiang ( Fig. 2) (Luo et al., 2017;Wang, 2018). ...
Granite-hosted uranium deposits are the most important types of uranium deposits in South China, but the metal sources of these deposits are still poorly constrained. The Miao’ershan batholith (South China) is a natural laboratory to address this issue, as well as to highlight the use of biotite composition as an indicator for the petrogenesis and uranium fertility of granites. Here, we present whole-rock and biotite geochemical data for U-bearing (Zhangjia and Douzhashan) and barren (Xiangcaoping and Paleozoic) granites of the Miao’ershan batholith. Contents of Li, Be, Mn, Sn, In, Nb, Ta, Ga, W, and U in the studied biotites increase from barren to U-bearing granites, while Mg, Ni, Co, V, and Rb display the opposite trend, which may indicate higher degrees of fractionation of the U-bearing granites. An Fe/(Fe + Mg) ratio of 0.65 in biotite appears to be an efficient threshold to discriminate between U-bearing and barren granites. New ternary discrimination diagrams are introduced, based on Li–V×20–Mn and Sn–Co×5–Nb, respectively, to aid the recognition of the U-bearing and barren granites. The relatively high whole-rock U concentrations (8.0−38.6 ppm) and low whole-rock ratios of Th/U (0.5−3.2) and REE/U (2.1−13.5) of the Zhangjia and Douzhashan granites favored the crystallization of uraninite. The samples experiencing fluid-wallrock interaction from the Zhangjia granite are characterized by low whole-rock U concentrations of 3.0 to 4.2 ppm and high Th/U ratios of 8.2 to 10.1, suggesting that a significant part of the U has been leached out by oxidizing meteoric waters. This confirms that the granite represents the primary source of U at the Zhangjia uranium deposit.
... Deciphering the origin of granites has great bearing on our understanding of continental differentiation and their genetic links to mineralization (Gao et al., 2018 and references therein). The Triassic granites in the interior of South China have been regarded as the product of intracontinental orogeny (Gao et al., 2017;Li and Li, 2007;Wang et al., 2013;Zhao et al., 2016;Zhou et al., 2006) and some of the intrusions are closely related to polymet allic mineralization in the region (Hu et al., 2017). Previous studies have shown that these granites are dominantly S-type with only minor I-type and A-type granites being present (Chen et al., 2007;Wang et al., 2013;Zhao et al., 2013a;Zhao et al., 2017;Zhou et al., 2006). ...
... Moreover, previous studies demonstrated that some of the Triassic granites have high U contents and play an important role in the formation of hydrothermal uranium deposits (Chen, 2004;Chen et al., 2012;Dong et al., 2010;Zhao et al., 2016). Although the deposits may be hosted in either granites or volcanic rocks, most of the basement or wall rocks in the vicinity of the deposits are U-rich Triassic granites (Chen, 2004;Chen et al., 2012;Dong et al., 2010;Zhao et al., 2016). ...
... Moreover, previous studies demonstrated that some of the Triassic granites have high U contents and play an important role in the formation of hydrothermal uranium deposits (Chen, 2004;Chen et al., 2012;Dong et al., 2010;Zhao et al., 2016). Although the deposits may be hosted in either granites or volcanic rocks, most of the basement or wall rocks in the vicinity of the deposits are U-rich Triassic granites (Chen, 2004;Chen et al., 2012;Dong et al., 2010;Zhao et al., 2016). Nevertheless, the primary U enrichment mechanism in Triassic granites is still a matter of debate. ...
Numerous Triassic biotite granites and two-mica granites crop out in the interior of South China, and some of them possess high U contents, which have been regarded as the sources for later hydrothermal mineralization. Their petrogenesis is therefore crucial for constraining the possible origins of the U enrichment. Here we report new LA-ICPMS zircon U–Pb ages, mineral geochemistry of biotite and muscovite, whole rock geochemical results and Sr–Nd and zircon Hf isotope data from the Jintan pluton in Central Jiangxi Province, South China. LA-ICPMS zircon U–Pb dating indicates that both biotite granite (BG) and two-mica granite (TMG) in the Jintan pluton crystallized at ~220 Ma. The TMG have higher U contents (7.85 to 48.90 ppm, average18.44 ppm) than theBG (4.99 to 17.72 ppm, average 8.64 ppm). Both BG and TMG show negative whole-rock εNd(t)and zircon εHf(t)values and contain some inherited zircons. The TMG are strongly peraluminous (A/CNK = 1.13–1.33), contain abundant primary muscovite, and display S-type affinity on plots of Yvs Rb and Th vs Rb, suggesting that they are S-type granites. The BG also display S-type granite affinities on plots of Yvs Rb and Th vs Rb. The suites display similar Sr–Nd isotope compositions (BG initial ⁸⁷Sr/⁸⁶Sr values = 0.711389 to 0.714225 and εNd(t) = −9.91 to −9.16, TMG initial ⁸⁷Sr/⁸⁶Sr values = 0.711832 and εNd(t) = −10.02) and are spatially associated, suggesting that the BG should also be classified as S-type granites. The TMG have higher zircon εHf(t)values (−6.4 to −1.1) than the BG (−8.7 to −3.7), indicating the TMG and BG might be derived from similar sediments but possibly with some distinct characteristics in their sources. The BG exhibit linear covariations in chemical compositions with relatively high total REE and light REE contents and MgO contents, while the TMG displays broader compositional variations but with relatively low total REE, light REE and MgO contents. Biotite geochemistry indicates the TMG formed in a more reduced magmatic system than the BG. The temperatures estimated by zircon saturation thermometry indicate the BG had distinctly higher magmatic temperatures than the TMG. The TMG display relatively high Al2O3/TiO2 ratios and low CaO/Na2O ratios than the BG but have higher Sr/Y and La/Yb ratios. The geochemical and petrological data suggest the BG were derived from clay-poor psammite sources at deeper levels with higher temperatures and higher oxygen fugacity, and underwent an extensive fractional crystallization, while the TMG was derived from clay-rich pelitic sources at higher levels and lower temperatures and fugacity with only limited fractional crystallization. We conclude that the combination of U-rich sources, physical-chemical conditions such as low partial melting temperature or low degrees of partial melting, a reduced environment and low REE and LREE contents of magmas controlled the U enrichment in TMG.
... Ore-hosting granites were mainly emplaced at the Triassic and Jurassic era (e.g. Zhao et al., 2011aZhao et al., , 2011bZhao et al., 2016), but uranium mineralization ages mostly concentrate on the Cretaceous to Tertiary period (Hu et al., 2008). The emplacement age of the Maofeng granite is about 227 Ma, and that of the dolerite dykes is about 195 Ma (Wang et al., 2015). ...
... The Maofeng granite is strongly peraluminous and belongs to S-type, similar with other Ubearing granites in South China (e.g. Zhao et al., 2016). In these granites, U is mainly distributed in accessory minerals (e.g. ...
... Generally, W was also enriched in S-type granites (e.g. Ling et al., 2005;Zhao et al., 2016). Thus, both U and W should come from the hydrothermal leaching of the Maofeng granite. ...
The Xiwang uranium ore deposit is one large-scale granite-hosted U deposit in the Xiazhuang U orefield in South China. Uranium orebodies occur as thin veins along the fracture zones within the Maofeng granitic pluton. Pyrite is the main sulfide mineral in the ores. Textural observation suggested that formation of hydrothermal pyrite can be divided into three stages: pre-mineralization stage pyrite (Py I), mineralization stage pyrite (Py II) accompanying with U-minerals, post-mineralization stage pyrite (Py III). In this study, in-situ sulfur isotopic compositions and trace element contents of pyrite from different stages were analyzed by laser ablation (MC-) ICP-MS methods. The δ³⁴S values of Py I vary from −28.5‰ to −12.0‰ with an average value of −18.4‰ Py II from −15.9‰ to −10.2‰ with an average value of −12.5‰ and Py III from −22.3‰ to −14.8‰ with an average value of −19.4‰. The variations of sulfur isotopic compositions of pyrites were caused by the changes of oxygen fugacity of hydrothermal fluids. The hydrothermal fluids at the pre-mineralization stage had relatively higher oxygen fugacity (ƒO2 > 10⁻³⁴). The decreasing of oxygen fugacity (to 10⁻³⁶–10⁻³⁵) at the mineralization stage might promote the precipitation of uraninite. The mineralization was terminated as the increasing of oxygen fugacity of hydrothermal fluids back to 10⁻³⁵. Pyrite from the Xiwang deposit generally contains high U contents (up to ten thousand ppm) and very low Th contents (mostly <0.1 ppm). U and W contents in pyrite show good positive linear relationship, indicating that both U and W came from the hosting granite. Py II shows higher Mo and V contents than Py I, also suggesting more reduced environment at the U mineralization stage. Such high oxygen fugacity for initial hydrothermal fluids supports that the ore-forming fluids should be originated from meteoric water. The circulating meteoric water can leach U and other metals from the hosting granite to form U-rich hydrothermal fluids. In fracture zones and under reduced conditions, U⁶⁺ in the fluids can be reduced to precipitate uraninite (UO2). Thus, U-rich granites, circuiting meteoric water and reduced agents are pre-requisites for the formation of the granite-hosted U deposits in South China.
... Several previous studies have investigated the geology and geochemistry of these deposits (e.g., Du, 1982;Min, 1995;Min et al., 1999; whereas the Jiufeng and Fuxi granites are barren. Understanding the characteristics of the U-bearing and barren granites is not only significant for formulating exploration strategies for granite-hosted uranium deposits in South China, but also for a better insights into the mechanism of U enrichment and mineralization for the granite-hosted uranium deposits (e.g., Zhang and Zhang, 1991;Zhang, 1996;Zhao et al., 2011Zhao et al., , 2016Chen et al., 2012). ...
... Substitution between U and other incompatible trace elements (such as Th, Zr, Ce, and Y) bonded with O 2− might lead to the formation of REE-bearing minerals, such monazite and zircon, which makes the content of the REE lower in the magma. Rich F can replace the bridging oxygen in the silicon-oxygen tetrahedron, thus releasing a large amount of O 2− that can combine with the excessive U to form uraninite (Cuney and Friedrich, 1987;Chen et al., 2012;Zhao et al., 2016). Because uraninite is leached most easily by hydrothermal solutions (Cuney and Friedrich, 1987;Cuney et al., 1990), thus the region with this favorable U-bearing species makes leaching of U by CO 2 -rich hydrothermal fluids easy, releasing substantial active uranium, thereby forming U ores. ...
... The granite-hosted uranium deposits in South China mainly occur in the Zhuguangshan, Guidong, Miao'ershan, and Taoshan complexes (Fig. 1), all of which contain U-bearing and barren granites, and some of these complexes have been investigated (e.g., Zhang, 1990;Zhao et al., 2011Zhao et al., , 2016Chen et al., 2012;Hu et al., 2014). ...
... Granite-related hydrothermal-vein uranium deposits are the Ubearing veins or disseminated mineralization that occurs in granite, adjacent (meta-) sedimentary rocks, or episyenite bodies (Cuney, 2009). Generally, this type of mineralization is related to large-scale, peraluminous two mica/biotite granite complexes that carry fertile and soluble uranium as uraninite (Cuney, 2014;Zhang et al., 2021), e.g., the Hercynian granite of the La Crouzille district of the Massif Central, France (Cuney, 1978), the Guerande granite in the Armorcian Massif (Ballouard et al., 2017), or the Mesozoic granite of the Nanling region, China (Hu et al., 2008;Luo et al., 2015;Zhao et al., 2011Zhao et al., , 2016Zhang et al., 2021). The spatial association between uranium mineralization and hydrothermal alteration has been documented in various scientific publications (Hu et al., 2008;Ballouard et al., 2017;Zhang et al., 2017a;Bonnetti et al., 2018;Qiu et al., 2018;Zhong et al., 2019;Zhang et al., 2021;Zhang et al., 2022). ...
... Uranium deposits in South China are divided into four types based on the lithology of host rocks: carbonaceous-siliceous-pelitic sedimentary-related, granite-related, sandstone-related, and volcanic-related ( Fig. 1, Min et al., 1999;Hu et al., 2008). Granite-related deposits are principally distributed in the Taoshan-Zhuguang and Chenzhou-Qinzhou belts, and have spatial and genetic relationships with several specific Triassic-Jurassic granitic batholiths, such as the Taoshan, Guidong, Zhuguangshan, Miao'ershan, and Dafuzu batholiths (Zhao et al., 2011(Zhao et al., , 2016Zhang et al., 2017bZhang et al., , 2019Zhang et al., 2021). ...
... Granite-related uranium deposits, one of the most important types of uranium deposits in South China (Zhang et al. 2021a), are mainly hosted by and Jurassic (170-150 Ma) granites (Zhang et al. 2017a;Zhong et al. 2019;Chi et al. 2020). Mineral explorations and scientific studies have revealed that such deposits are spatially and genetically associated with a few granitic bodies, which are regarded as uranium-fertile granites (Zhao et al. 2011(Zhao et al. , 2016Zhang et al. 2018a). Generally, the formation of these uranium deposits has been linked to the regional Cretaceous to Tertiary crustal extension and related mafic magmatism, which could have provided thermal energy for fluid circulation that resulted in the mobilization of uranium from U-rich rocks (Min et al. 1999;Hu et al. 2008;Mao et al. 2013;Chi et al. 2020). ...
... They are mainly hosted by or occur adjacent to granites and formed at around 110-50 Ma (Hu et al. 2008;Bonnetti et al. 2018;Zhong et al. 2019;Chi et al. 2020). Most of the granites related to uranium mineralization are of Triassic (251-205 Ma) and Jurassic age (180-142 Ma; Zhao et al. 2011Zhao et al. , 2016Chen et al. 2012;Zhang et al. 2017bZhang et al. , 2018aChi et al. 2020). The formation of granite-related uranium deposits in this region has been linked to regional crustal extension events (Hu et al. 2008;Luo et al. 2015;Zhong et al. 2019;Chi et al. 2020). ...
Allanite is an important rare earth element (REE)-U-bearing mineral in granites, and it can act as a metal source for the formation of some hydrothermal uranium deposits and ion-adsorption REE deposits. To investigate the potential of allanite as a mineral probe of granite-related uranium mineralization processes and the formation of ion-adsorption REE deposits, we present textures, geochemistry, and in situ U-Pb isotope data for allanite from the fertile Changjiang granite associated with the Changjiang uranium ore field and barren Jiufeng granite in the Zhuguangshan batholith, South China. Alteration of allanite in the Changjiang granite is characterized by the altered domains with lower backscattered electron (BSE) intensities than the unaltered domains and replacement by other secondary minerals such as REE fluorocarbonates, calcite, fluorite, thorite, clay minerals, quartz, chlorite, and epidote. Crystals from the Jiufeng granite were partly replaced by the altered domains appearing darker in BSE images and minor REE fluorocarbonates. The darker domains of the Changjiang and Jiufeng allanite grains have higher Fe 3+ /(Fe 3+ +Fe 2+) ratios and U concentrations than those of the brighter domains, indicating that the alteration of allanite was probably related to more oxidized fluids. This study suggests that the Changjiang granite might have been subjected to the influx of F-and CO 2-bearing fluids. The brighter domains of the Changjiang and Jiufeng allanite grains have weighted mean 207 Pb-corrected 206 Pb/ 238 U ages of 156.7 ± 4.3 Ma and 161.6 ± 5.3 Ma, respectively, consistent with the corresponding zircon 206 Pb/ 238 U ages of 156.1 ± 1.4 Ma and 159.8 ± 1.8 Ma. The darker domains of the Changjiang allanite grains yield a weighted mean 206 Pb/ 238 U age of 141.4 ± 5.6 Ma, which overlaps within error the timing of a uranium mineralization event (~140 Ma) in the Changjiang uranium ore field and the age of a crustal extension event (140-135 Ma) in South China. The BSE images and elemental maps reveal that rare earth elements such as La and Ce have been released from the Changji-ang allanites during alteration and were precipitated as REE-fluorocarbonates that are susceptible to chemical weathering, which sets the stage for the formation of an ion-adsorption REE deposit. Our study suggests that the regional crustal extension might have played an important role in the formation of both granite-related uranium and ion-adsorption REE deposits in South China, as it could have triggered alteration or breakdown of REE-U-bearing minerals in source rocks.
... The Pingtan W deposit is located in the western portion of the Etrending Nanling Range in South China (Fig. 1), which formed by the Neoproterozoic amalgamation of the Yangtze Block in the northwest and Cathaysia Block in the southeast ( Fig. 1a; Li et al., 2002;Shu et al., 2011Shu et al., , 2014Song et al., 2015;Yao et al., 2013;Zhou et al., 2009;Zhao et al., 2013Zhao et al., , 2016. Neoproterozoic, Early Paleozoic (Caledonian), Triassic (Indosinian), and Jurassic-Cretaceous (Yanshanian) granites occur throughout the Nanling Range. ...
... Neoproterozoic, Early Paleozoic (Caledonian), Triassic (Indosinian), and Jurassic-Cretaceous (Yanshanian) granites occur throughout the Nanling Range. Most of the W-Sn deposits in the Nanling Range are temporally and genetically associated with the Jurassic--Cretaceous (Yanshanian) granites (Fig. 1b;Mao et al., 2007Mao et al., , 2008Mao et al., ,2013bPeng et al., 2006Peng et al., , 2007Liu et al., 2017Liu et al., , 2018Yuan et al., 2012aYuan et al., , 2012bZhao et al., 2016Zhao et al., , 2018Xiong et al., 2020). However, some newly discovered W-Sn deposits situated in the western portion of the Nanling Range are associated with Early Paleozoic granites (Yang et al., 2014;Chen et al., 2016Chen et al., , 2018Chen et al., ,2019Zhang et al., 2017;Zhu et al., 2020;Fig. ...
... They share the following conclusions: (1) The deposits formed through hydrothermal activity are generally associated with fault systems (Hu et al., 2008;Luo et al., 2015Luo et al., , 2019Zhong et al., 2022) and U ore bodies are often found in high-angle normal fault zones, exhibiting vein or lenticular geometries (Du, 1982;Dahlkamp, 2009). (2) Uranium mineralization is genetically linked to several typical Triassic-Jurassic peraluminous U-fertile granites of South China, such as Fucheng, Zhuguangshan, Guidong, Taoshan, and Miaoershan batholiths (Chen et al., 2012;Zhao et al., 2016;Zhang et al., 2021a). (3) Several types of hydrothermal alterations occurred around the ore bodies, including silicification, chloritization, hydromicazation, hematitization, albitization, and carbonatization. ...
... Based on the petrology of host rocks, these deposits can be divided into three types: carbonaceoussiliceous-pelitic sedimentary rock-related, volcanic rock-related, and granite-related ( Fig. 1, Hu et al., 2008;Zhang et al., 2019). Graniterelated U deposits in South China are mostly found in the Chenzhou-Qinzhou and Taoshan-Zhuguang belts; where it contain several U ore fields, including Xiazhuang, Zhuguang, Taoshan, Miaoershan, and Lujing, etc (Dahlkamp, 2009;Zhao et al., 2016;Zhao, 2017;Zhang et al., 2019;Zhong et al., 2019a). ...
The Mianhuakeng deposit is the largest granite-related U deposit in China, with multiple hydrothermal quartz veins. However, its genesis and ore-forming processes are still under discussion. In the present study, we have attempted to unveil the characteristics of ore-forming fluids and the metallogenesis of Mianhuakeng deposit with the help of cathodoluminescence (CL) imaging, fluid inclusions (FIs), trace elements, as well as hydrogen-oxygen (H-O) isotope compositions of hydrothermal quartz associated with U mineralization. Based on the crystallography and CL textures, four generations of hydrothermal quartz have been identified: early stage QtzⅠ quartz, main stage QtzⅡa and QtzⅡb quartzes, and late stage QtzIII quartz. QtzⅠ was formed by a continuous fluid flow in an open fluid system. The formation of QtzIIa was associated with a brief period of fluid flow in a compressive fluid system, whereas QtzIIb crystallized in an open system with a stable fluid flow. QtzIII was produced by fluid chemical fluctuation in an open system. These quartzes show high Al, variable Li, Na, K, and Ca, moderate Rb and Ba, and low Ti, Fe, Ge, and U contents. Al³⁺ and Ge⁴⁺ were incorporated into the quartz crystal lattice by substituting Si⁴⁺, helped by the change compensators composed of Li, Na, K, Rb, Ca, and Ba. The FIs microthermometry results suggested that ore-forming fluids were NaCl–H2O ± CO2 system with moderate to low temperatures and salinities. A gradually decreasing trend has been recorded for temperatures from 225 to 353 ℃, through 153–302 ℃, and toward 105–161 ℃, respectively, with salinities changing from 6.0 to 10.1 wt.% NaCl equiv, through 0.6–10.1 wt.% NaCl equiv, to 0.5–5.7 wt.% NaCl equiv from early to late stages. The H-O isotopic results indicated that the ore-forming fluids were originated from a mixture of deep magmatic and meteoric waters, with an increase in the amount of meteoric water from early to late stages. Fluid decompression and immiscibility were triggered by episodic fracturing of NS-trending fractures, which resulted in a fluid flow transition from extrusion to opening and the breakdown of uranyl complexes. The Fe²⁺ from altered granites reduced free U⁶⁺ to U⁴⁺, forming pitchblende (UO2) in hydrothermal quartz veins. Therefore, the Mianhuakeng deposit is thought to be of polygenic in origin and is controlled by several geological factors such as fracturing, fluid immiscibility, and redox reaction.
... Granite-related uranium deposits in South China are typically epigenetic in origin and are mainly distributed in the Cathaysia Block and Jiangnan Orogen (Fig. 1). Wholerock geochemical data indicate that their host granites were mainly derived from the partial melting of metasedimentary rocks and belong to S-type granites (Zhao et al., 2011a(Zhao et al., , 2015(Zhao et al., , 2016Chen et al., 2012;Gao et al., 2014;Zhang et al., 2017;Zhang et al., 2018). However, uranium deposits in the Lu-Zong volcanic basin (South China) are spatially related to A-type granites (Fig. 2a), and they are regarded as a product of magmatic processes of these plutons (Zhang and Min, 1985;Zhang and Zhang, 1991;Zheng et al., 1995;Zhao et al., 2004). ...
... Abbreviations: Altaids -Altaids Orogenic Belt, TC -Tarim Craton, K-QDOB -Kunlun-Qinling-Dabie Orogenic Belt, NCC -North China Craton, T-SO -Tibet Plateau and Sanjiang Orogen, YC -Yangtze Craton, CB -Cathaysia Block. Zhao et al., 2011aZhao et al., , 2016Chen et al., 2012;Deng et al., 2012;Zhang et al., 2018). In these granites, uranium is mainly hosted by uraninite (Zhang et al., 2021b). ...
Although most of granite-related uranium deposits in South China are spatially and genetically associated with S-type granites, few are related to A-type granites. In this study, we present whole-rock major and trace elements, zircon U-Pb geochronology, and mineral chemistry data for the Huangmeijiang A-type granite in the Lu-Zong volcanic basin (South China) to investigate the origin of uranium deposits related to this pluton. The uranium ore bodies mainly occur within the Jurassic Luoling formation close to the Huangmeijian pluton. Whole-rock and biotite geochemistry indicates that the F-rich alkaline magmas with relatively high fO2 prompted the partitioning of U into the fluids released from the Huangmeijian pluton with an affinity of A-type granites, which would set the stage for the later concentration of the U into the Jurassic Luoling formation. Thorite, zircon, apatite, and bastnäsite are the dominant accessory minerals that host U in this pluton. Backscattered electron (BSE) images suggest that some zircon and thorite grains can be divided into the unaltered domains and altered domains. The textural features are interpreted as a later hydrothermal event superimposed on the magmatic zircon and thorite. In situ LA-ICP-MS U-Pb dating on the unaltered domains and altered domains of zircon grains yielded weighted mean ages of 127.8 ± 1.0 Ma and 65.7 ± 5.3 Ma, respectively. The former age represents the emplacement age of the Huangmeijian pluton, and the later one overlaps the timing of a uranium mineralization event (∼66.6 Ma) in this area. The altered domains of thorite and high-(U + Th) zircon grains have lower U contents than those of the unaltered domains, indicating that uranium was mobilized from thorite and zircon during fluid infiltration, which might be the main source of uranium for the ∼66.6 Ma uranium mineralization. Our study suggests that the Huangmeijian pluton was the primary source of uranium for the formation of uranium deposits in this area.
... The U-rich granites in this region mainly include the Motianling, Miao'ershan, Jiuyishan, Liuchen, Guidong, Zhuguangshan, Guidong, Taoshan, Aigao, and Dafuzu granitic batholiths, the Anlu quartz syenite belt (including the Huangmeijian, Chenshan, and Dalongshan granites), and the Yaocun granite . These intrusions mainly Lithos 308-309 (2018) [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] formed during Cambrian-Cretaceous (e.g., Chen et al., 2012;Deng et al., 2011Deng et al., , 2012Gao et al., 2017;Jiao et al., 2015;Zhang and Zhang, 1991;Zhao et al., 2011Zhao et al., , 2013Zhao et al., , 2014Zhao et al., , 2015Zhao et al., , 2016. Among these, a close spatial and genetic relationship of uranium mineralization with granitoids is displayed only by several intrusions such as the Daguzhai granite in the Taoshan complex (Zhao et al., 2011), the Xiazhuang granite in the Guidong complex , the Douzhashan granite in the Miao'ershan complex , and the Changjiang granite in the Zhuguangshan complex (L. ...
... Zhang et al., 2017), known as U-bearing granites. Understanding the features of U-bearing granites is not only significant for formulating exploration strategies for granitehosted uranium deposits, but also for a better insight into the mechanism of uranium metallogenesis Cuney, 2009;Zhang and Zhang, 1991;Zhao et al., 2011Zhao et al., , 2016. ...
The Zhuguangshan complex, composed of Caledonian, Indosinian, and Yanshanian granites, and Cretaceous mafic dykes, is one of the most important granite-hosted uranium producers in South China. Here we present LA-ICP-MS zircon U-Pb and hornblende ⁴⁰Ar/³⁹Ar geochronology and whole-rock and biotite geochemistry for the granites in this complex to evaluate the magmatism and its constraints on uranium mineralization. Samples collected from the Fuxi, Youdong, Longhuashan, Chikeng, Qiling, and Sanjiangkou intrusions yield zircon weighted ²⁰⁶Pb/²³⁸U ages of 426.7 ± 5.4 Ma, 226.4 ± 3.5 Ma, 225.0 ± 2.7 Ma, 152.2 ± 3.0 Ma, 153.9 ± 2.1 Ma, and 155.2 ± 2.1 Ma, respectively. A new Ar-Ar dating of the hornblende of the diabase from the Changjiang uranium ore field yields a plateau age of 145.1 ± 1.5 Ma. These results coupled with published geochronological data indicate that six major magmatic events occurred in the study area at 420−435 Ma, 225−240 Ma, 150−165 Ma, ~140 Ma, ~105 Ma, and ~90 Ma. Both U-bearing and barren granites occur in this complex, and they display differences in whole-rock and biotite geochemistry. The barren granites show higher Al2O3, CaO, TFMM, Rb, Zr, Ba, SI, Mg#, (La/Yb)N, and Eu/Eu* but lower SiO2, ALK, Rb, DI, Rb/Sr, and TiO2/MgO than those of the U-bearing granites. Biotites in the U-bearing granites are close to the Fe-rich siderophyllite-annite end member with Fe/(Fe + Mg) ratios higher than 0.66, whereas those in the barren granites are relatively close to the Mg-rich eastonite-phlogopite end member with Fe/(Fe + Mg) ratios <0.66. The U-bearing granites were mainly derived from the partial melting of pelitic sedimentary source, whereas the psammitic source generated the barren granites. In addition, the barren granites show higher TFMM, Ba, and Eu/Eu* but lower SiO2, Rb/Sr and Al2O3/TiO2 ratios with higher zircon saturation temperatures relative to the U-bearing granites. These results indicate that the geochemical compositions of the U-bearing and barren granites are dictated not only by the compositions of source rocks but also the physicochemical conditions of partial melting. Our study suggests that these two factors are also the major factors that control uranium ore potential of the granites in the Zhuguangshan complex. The geochemical variations of U-bearing and barren granites can serve as a potential detector for granite-hosted uranium deposits.
... Therefore, we propose that the monzogranites formed under the Palaeo-Tethys tectonic regime by the Indochina Block and North China Block collision (Fig. 13a, c). Subsequently, the extension of granitoid along the Hunan-Jiangxi-Fujian Province during 225-210 Ma (Li et al., 2012a;Wang et al., 2013b;Fu et al., 2015;Ding et al., 2015;Shu et al., 2015;Zeng et al., 2016;Zhao et al., 2016;Song et al., 2017), the 220 Ma sinistral trans-tension, and the contemporaneous divergent non-coaxial extension in the Yunkai Massif (Wang et al., 2007b) indicate that the South China Block was in an extension environment. Thus, combining the monzogranites, we suggest that the transition from a syn-collision to an extension environment of the South China Block occurred during 226-225 Ma. ...
The Early Mesozoic tectonic transition from the Paleo-Tethys tectonic regime to Paleo-Pacific tectonic regimes in the South China Block has long been debated.
Geochronology and geochemistry were carried out for the Early Mesozoic granitoids in the eastern Hunan Province to investigate their petrogenesis and the associated tectonic transition of the South China Block. Geochronology and petrography show that these plutons developed in two phases: 1) Late Triassic monzongranites, and 2) Late Jurassic alkali-granites. The monzogranites are characteristics by decrease in P2O5 contents when SiO2 contents increasing, low A/CNK index, belonging to I-type granites. They have negative εNd(t) and εHf (t) values with old two-stage crustal Nd-Hf isotopic model ages, together with the high zircon saturation temperatures and geochemical features, indicating a Mesoproterozoic crustal metabasite sources. The alkaligranites are characteristic by high A/CNK values, and Fe# index, and low Al2O3 and CaO contents, which belong to A-type granites. They have negative εNd (t) and εHf (t) values with old two-stage crustal Nd-Hf isotopic model ages, together with the low zircon saturation temperatures and geochemical features, indicating a Neoproterozoic crustal metasedimentary sources. Combined with previous results, we suggest that the Late Triassic monzogranites formed in syn-collision environment that
related to the collision of continents in the Palaeo-Tethys oceans, whereas the Late Jurassic alkali-granites formed in post-orogenic environment that resulted from the break-off/roll-back of the Palaeo-Pacific Plate. The tectonic transition from the Paleo-Tethys tectonic regime to the Paleo-Pacific tectonic regime in the South China Block occurred between the Late Triassic and Early Jurassic.
... Metamorphic and igneous context and especially uranium-rich context, while RC concentration does appear necessarily anomalous, are definitely characterized by larger RF values. Igneous and metamorphic rocks are in any case the most important uranium sources in China (Zhao et al., 2016;Luo et al., 2017) and worldwide (Cuney, 2010;Bezuidenhout, 2019;Fayek et al., 2021). The large domain of higher RF values, associated with the uranium-rich context, confirms that, in the case of relatively deep concealed uranium-rich deposit for which gamma ray prospection will not be successful, then RF and RC measurement could be an efficient exploration tool (Kang et al., 2020). ...
The inert radioactive gas radon-222, ubiquitous in the environment, is the first cause of lung cancer in non-smokers and a powerful asset to trace geological fluids and constrain atmospheric transport models. In all of these applications, radon flux (RF) from the ground needs to be estimated. However, obtaining a large-scale representative estimate of RF in continental land is a challenging task and a starting basis is to focus on large countries in the world. Here, we collected a total of 2622 direct RF measurements carried out in continental China from 1988 to 2021 using 69 publications in a 494-document pool. Over the whole dataset, the RF results were classified into geographical provinces, time periods and substratum types. Mean RF values yield 180±32, 36.9±4.8, 31.1±1.0, 66.1±1.6 and 1510±100 mBq m⁻² s⁻¹ in metamorphic and igneous (n=71), sedimentary (n=24), Quaternary (n=585), faulted areas (n=832) and uranium-related sites (n=898), respectively. Considering geology only, mean RF for China (66±11 mBq m⁻² s⁻¹) is larger than most large-scale estimates worldwide. To account for the distribution of soil thickness, RF values were extrapolated to representative soil thickness values per lithology using a scaling law inferred from natural sites. The inferred corrected mean RF for China yields 20.2±6.1 mBq m⁻² s⁻¹, corresponding to a total radon-222 emission of (191±43) × 10⁹ Bq s⁻¹, and appears compatible with available large-scale estimates in Europe or at global scale. Potential sources of systematic bias and variability, such as vegetation cover, meteorological and seasonal effects, remain. The contribution of urban areas, estimated for the first time, was found significant. Our study suggests future research directions to better constrain the RF source to the atmosphere in China, and, more generally, to extract robust global-scale representative RF values from direct RF measurements.
... Granite-related uranium deposits in South China are mainly distributed in the Cathaysia Block and the Jiangnan Orogen (Fig. 1). Most of the granites associated with granite-related uranium deposits are of Triassic (251-205 Ma) and Jurassic ages Ling et al., 2004Ling et al., , 2005Sun et al., 2005;Zhao et al., 2011Zhao et al., , 2016 Zhou et al., 2006;Hu et al., 2008). 2018). ...
The Xiazhuang uranium ore field contains eighteen uranium deposits and is one of the most important granite-related uranium ore producers in South China. Silicified vein-type and intersection-type uranium deposits are the two main types of uranium deposits in this ore field. To constrain the mineralization ages and sources of uranium of these two types of uranium deposits, we present geochemistry and U-Pb isotopic data of uraninites from the representative Xianshi intersection-type and Xiwang silicified vein-type uranium deposits in the Xiazhuang ore field. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb dating on uraninite from the Xianshi deposit yielded the crystallization age of 89.9 ± 2.1 Ma, which is consistent with the emplacement age (∼90 Ma) of NNE-trending diabase porphyrite dykes in this area. Chondrite-normalized rare earth element (REE) patterns of uraninite from the Xianshi deposit are characterized by slight enrichment of light REE relative to heavy REE and weakly positive Eu anomalies. Our study suggests the involvement of mantle-derived metals in the formation of the Xianshi deposit. In situ LA-ICP-MS U-Pb dating on uraninite from the Xiwang deposit yielded a weighted mean age of 51.3 ± 0.8 Ma, which overlaps the timing of the 55−45 Ma crustal extension event in South China. Uraninite from the Xiwang deposit has much higher contents of W (5768–11305 ppm), Nb (294–1301 ppm), and Y (3013–6263 ppm) than those of uraninite from the Xianshi deposit (W = 291–371 ppm, Nb = 3–14 ppm, and Y = 1658–3149 ppm). Uraninite from the Xiwang deposit has “gull-winged” chondrite-normalized REE patterns with pronouncedly negative Eu anomalies, which resemble whole-rock REE patterns of the Maofeng and Xiazhuang granites. This study suggests that the Maofeng and Xiazhuang granites are probably the primary source of uranium for the Xiwang deposit.
... In some outcrops, the Mao'ershan-Yuechengling granites are overlain by Middle Devonian sedimentary rocks ( [30] and references therein). The early Paleozoic Mao'ershan-Yuechengling granites were intruded by younger Triassic granites with ages of 236-204 Ma ( [31,32] and references therein). The Mao'ershan-Yuechengling batholith is divided into the Mao'ershan and Yuechengling plutons by the Xinzi Fault. ...
Although pegmatites are volumetrically minor in the upper continental crust, these rocks host abundant rare metal deposits (e.g., Li, Be, Rb, Ta, and Nb). Pegmatites can be formed either by extensive fractional crystallization of granitic magmas or by low-degree partial melting of metasedimentary rocks. The Mao’ershan–Yuechengling composite batholith in the Nanling Range in the South China Block (SCB) is of early Paleozoic–Triassic age (440–381 and 236–204 Ma, respectively). Recently, hundreds of pegmatites associated with Nb, Ta, Be, Rb, and Li mineralization have been identified in this batholith. These pegmatites are hosted by granitic wall rocks. However, the relationships between the pegmatites and granitic wall rocks are not well constrained. To address this, we investigated the Mao’antang (MAT) and Tongzuo (TZ) pegmatites and their biotite granite wall rocks in the middle part of the Yuechengling pluton. Laser ablation inductively coupled plasma mass spectrometry zircon U–Pb ages revealed that the MAT pegmatites formed during the Permian (269 Ma) and Triassic (231 Ma) and that the MAT biotite granite wall rock records two stages of magmatic activity (271 and 231 Ma) that are coeval with the pegmatites. The TZ pegmatites probably formed during the Triassic (235 Ma), and the TZ biotite granite wall rock formed during the Silurian (435 Ma). The MAT biotite granite and pegmatites (εNdt=−12.0 to −10.6; εHft=−8.0 to −1.0), TZ pegmatites (εNdt=−10.4 to −6.1), and TZ biotite granites (εNdt=−9.1 to −8.7; εHft=−7.7 to −4.1) have enriched whole-rock Nd and zircon Hf isotopic compositions that are similar to those of early Paleozoic and Triassic S-type granites in the SCB. In addition, the whole-rock Pb isotopic compositions of the MAT and TZ pegmatites and granites are distributed along the upper crust evolution line. We suggest that the MAT and TZ biotite granites were mainly derived from Paleoproterozoic metasedimentary rocks in the middle crust. The MAT pegmatites are fractional crystallization products of the MAT biotite granites, whereas the TZ pegmatites were formed by fractional crystallization of hidden parental S-type granites. We propose that the MAT and TZ pegmatites have potential for rare metal (Nb, Ta, Be, and Li) mineralization, as they record high degrees of fractional crystallization. The MAT and TZ areas in the middle of the Yuechengling pluton are promising targets for rare metal exploration.
... Previous studies have focused on the geochronology and geochemistry of the fresh granites (FG) [9,10] and found that granite hosting U mineralization has a high U content; more than three times the average U content (3.5-4.8 ppm) of typical acidic igneous rocks [13,14]. These granites are generally characterized by genesis through crustal partial melting, high-silica, high-alkali, and peraluminous character [9][10][11]16,17]. It is believed that the prerequisites for the U mineralizing potential of these U-rich granites lie not only in the high U content, but also in the development of active faults and fluid-flow-related hydrothermal alterations. ...
The recently discovered Sanjiu ore field (SJOF) is a granite-related uranium ore field located in the middle of Zhuguangshan (South China). The relationship between hydrothermal alteration of granite and uranium mineralization in the SJOF is crucial yet understudied. In this study, the major- and trace-element contents of granite samples (fresh granite, altered granite, and tectonites) with different uranium contents were analyzed by using X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma–mass spectrometry (ICP–MS). The analytical results show a relative increase in Si, S, Ca, Pb, Mo, and Sb content in altered granites and tectonites, relative to fresh granites. During the mineralization stage, the increase of the aforementioned elements is related to various hydrothermal alterations (e.g., silicification, carbonation, sulfation, etc.) and newly formed minerals (e.g., microfine crystalline quartz veins; calcite agglomerates or fine veins; and metal sulfides, such as pyrite). There is a concomitant relative decrease in Na, K, Al, Fe, Mg, and other elemental contents that may be due to mineralogical alteration processes, such as biotite to chlorite, feldspar-group minerals to clay minerals, and redox of Fe-bearing minerals. The LREE/HREE ratio in altered granites decreases significantly with the increase in uranium content, suggesting that a low LREE/HREE ratio may be a prospecting indicator. The normalized trace-element patterns of mineralized granite (ore) and the relatively high U content of fresh granite imply that granitic rocks may be the primary uranium source in the SJOF. The uranium mineralization is mainly concentrated in the redox zone that occurs at a depth of 100−300 m. The redox zone is characterized by the most developed hydrothermal alterations and enrichment of trace elements, including W, Mo, Sb, Li, and the HREE.
... The construction of the Philippines' Bataan Nuclear Power Plant in 1970s led to a nationwide exploration for U. The close association of U deposits with granitic bodies (Chen et al., 2012;Luo et al., 2017;Zhao et al., 2016) prompted several explorations in the only two known granitic bodies in the country found in San Vicente, Palawan. Bay Peak Pluton is one of the two granitic bodies that intruded the sedimentary and metamorphic rock Formations in Northern Palawan during the Middle Miocene (Encarnación, 2004;Suggate et al., 2014). ...
Past exploration for U deposit in the Philippines discovered the mineralization of radioactive allanite in Palawan. The allanite occurs as sand component in the heavily populated beach of Erawan, San Vicente, Palawan. This work assessed the risks associated with the radionuclides in Erawan beach by in situ ground radiometric survey of K, U, and Th in 694 sampling points. Principal component analysis (PCA) and Pearson correlation coefficient were used to determine the similarity between the radionuclides and to identify other probable anthropogenic sources of radionuclides. Our results show that the mean activity concentrations of K (597.8 Bq kg-1) and Th (93.15 Bq kg-1) are equivalent to 1.5 and 3.1 times of the world average natural radioactivity levels in soil, respectively, while the mean U (34.7 Bq kg-1) is similar to the world average. The mean radiological risk assessments like radium equivalent, gamma specific activity index, external hazard index, internal hazard index, absorbed gamma dose rate, annual effective dose equivalent, annual gonadal equivalent dose, and excess lifetime cancer risk are 213.96 Bq kg-1, 0.78, 0.58, 0.67, 97.24 nGy h-1, 119.25 µSv y-1, 684.39 µSv y-1, and 0.42 (10-3), respectively. Th consistently correlated most to the risks. We attribute the occurrence of Th to the presence of allanite, K to fertilizer use for farming, and U to both the allanite and farming. The results of our study can provide important baseline data for future detailed studies or monitoring of the long-term effects of elevated radiation levels to the local population of Erawan.
... The migration of REE and pitchblende was synchronous, which is the product of crystallization and precipitation at a low-temperature hydrothermal environment. key words：Pitchblende; LA-ICP-MS; Rare Earth Element; Xiangyangping 苗儿山地区是我国南方重要的铀成矿区，分布有向阳坪矿床、沙子江矿床、白毛冲矿床、双滑江矿 床、孟公界矿床等诸多规模较大的花岗岩型铀矿床，其中向阳坪矿床为近年来新发现的矿床。空间上， 向阳坪矿床与沙子江矿床毗邻，沙子江矿床的范围仅限于 F 800 构造带，而向阳坪矿床则包括 F 7 、F 8 (不 包含 F 800 ) 、F 9 、F 10 等断裂构造带组，两者具有相同的成矿地质条件，属同一期构造应力场控制下的产物。 对于该地区构造控矿机制、岩石地球化学、矿床成因、围岩年代学、铀源矿物等方面，前人已经开展了 大量的研究工作 [1][2][3][4][5][6][7][8][9][10] 。在铀成矿年代学方面的研究，近年来主要集中在沙子江矿床，而向阳坪矿床暂未见 有相关报道。具体如下：石少华等 [11] 通过挑选沥青铀矿单矿物样品，采用 U-Pb 等时线方法，获得了沙子 [16,17] [19] 。本次分析的激光束斑和频率分别为 10 µm 和 1 Hz。U-Pb 同位素定年处理中采 用铀矿标准物质 GBW04420 作外标进行同位素分馏校正。每个时间分辨分析数据包括大约 20-30 s 空白信号和 50 s 样品信号。对分析数据的离线处理(包括对样品和空白信号的选择、仪器灵敏 度漂移校正以及 U-Pb 同位素比值和年龄计算)采用软件 ICPMSDataCal [20,21] 完成。样品的 U-Pb 年龄谐和图绘制和年龄加权平均计算采用 Isoplot/Ex_ver3 [22] 完成。 图 2 含沥青铀矿脉花岗碎裂岩(a，b)和沥青铀矿脉背散射电子图像(c) Table 2 REE composition of pitchblende from Xiangyangping uranium ore deposit 点号 3-01 3-04 3-05 3-06 3-07 3-08 3-09 3-10 3-11 3-12 3-13 3-14 3-15 3-17 3-18 3- [44] 。同时，铀矿石 ThO 2 含量最高为 0.09 wt% [12] ， ΣREE 值平均为 0.06 wt%(小于 1 wt%) ，说明测试样 品基本上不含 Th 和具有极低的稀土总量， 亦反映其形成于低温流体环境(T＜350℃) [25,43] ，与石少华等(2011) [45] ...
The Xiangyangping uranium ore deposit is a newly discovered granite-type uranium deposit, which is one of the representative granite-hosted uranium deposits in the Miaoershan uranium ore field. The Xiangyangping uranium deposit has developed a large number of primary pitchblende veins, but the chronology characteristics of uranium minerals are obscure, especially the application of in-situ analyses technique is lacking. In order to further clarify the uranium mineralization age of the uranium deposits, in situ U-Pb isotopic dating of pitchblende veins exposed in the borehole was studied by using LA-ICP-MS. The U-Pb age dating of the pitchblende obtained ages of 51.59 Ma and 41.10Ma, suggesting that there are two phases of uranium mineralization in the Xiangyangping area, which are consistent with the main mineralization periods of 50-65Ma and 40-45Ma for the Shazijiang uranium ore deposit. The former is the main metallogenic age of Xiangyangping uranium ore deposit, while the latter is the thermal event time of late fluid activity leading to pitchblende alteration, indicating that there is a major uranium metallogenic event of about 52Ma in the Miaoershan uranium ore field. The chondrite-normalized patterns of rare earth elements are rich in light-REE, with obvious negative
Eu anomalies. The distribution curve of rare earth elements in pitchblende is characterized by in seagull pattern, which is similar to low-high grade uranium ore are，and different from the "right-dipping type" of fresh granite and altered granitic cataclastic rock. The migration of REE and pitchblende was synchronous, which is the product of crystallization and precipitation at a low-temperature hydrothermal environment.
... The MYGB is a typical composite batholith in the western part of the Nanling Range in that it records multiple episodes of tectonic-magmatic activity in the Neoproterozoic (840-806 Ma; Bai et al., 2010), Paleozoic (437-381 Ma; Zhang et al., 2012;Zhao et al., 2013;Yang et al., 2014;Bai et al., 2014Bai et al., , 2015Chen et al., 2016), and Early Mesozoic (220-215 Ma; Wu et al., 2012;Zhao et al., 2014;Chen et al., 2016;Zhao et al., 2016). New zircon U-Pb data from the present study yield the crystallization age of 153 ± 3 Ma for Gedongping aplite, consistent with magmatism in the Late Mesozoic. ...
The Miao’ershan–Yuechengling granitic batholith (MYGB) in the west Nanling Range, South China, contains multiple intrusive phases including the Paleozoic porphyritic biotite granite and Early Mesozoic two-mica and muscovite granite associated with the W–Cu–U mineralization. In this study, the Gedongping granitic rocks, in the central part of the MYGB are shown to be related to Sn–Nb–Ta–Be mineralization. They comprise albite granite, pegmatite, and aplite, and intrude the Paleozoic granite. Sn–Nb–Ta oxide minerals such as cassiterite, columbite-group minerals, microlite and wodginite are common. Beryl occurs in the pegmatite and aplite. Zircon U-Pb isotopic data yielded an age of 153 ± 3 Ma for the formation of the aplite. In situ U-Pb dating of cassiterite from the albite granite and aplite yielded ages of 147 ± 5 and 155 ± 3 Ma, respectively, for the Sn mineralization. Geochemically, theses granitic rocks are rich in SiO2 (~72 wt%), Al2O3 (~15 wt%), and total alkali (~10 wt%), and the alumina saturation index is 1.0 to 1.1. Combined with the high HfO2 contents (up to 15.1 wt%) and low Zr/Hf ratios (6–35) in zircons, it is indicated that the Gedongping granitic rocks are highly evolved. We infer that the Gedongping granitic rocks underwent magmatic fractionation and subsolidus hydrothermal alteration, based on the textural and compositional variations of the Sn–Nb–Ta oxide minerals. Two fine-grained granite stocks within the MYGB, which were described as Late Mesozoic products, have been confirmed to form during the Paleozoic (420–426 Ma).
... 2.2, 12.3, and ca. 6.7 ppm uranium, respectively (Jiang et al., 2006;Wang et al., 2012a;Qi et al., 2013;Zhao et al., 2016;Arndt et al., 2017), all of which are above the typical concentrations within the continental crust (1.4-1.6 ppm; Gao et al., 1998). This also suggests that the most favorable host rocks for mineralization are the uranium-rich granitic rocks, although uranium deposits occur in various rock types (Min et al., 1999(Min et al., , 2005Hu et al., 2008). ...
Uranium deposits are diverse as a result of their formation in a wide variety of geological environments. However, the source of the uranium within these deposits is difficult to identify and as a result it is usually poorly understood. This study focuses on the hydrothermal Sanqiliu and Sanqisi uranium deposits, both of which formed within NE–SW striking shear zones that cross-cut the Sanfang batholith and low-grade metasedimentary rocks of the Motianling district, southern China. The deposits contain vein-hosted pitchblende–quartz–pyrite–chlorite–mica orebodies. Fluid inclusions within quartz in the orebodies in the district homogenize at temperatures between ∼205 °C and ∼222 °C, indicating the deposit formed as a result of low- to intermediate-temperature hydrothermal activity. Pitchblende-associated hydrothermal pyrite within the Sanqiliu and Sanqisi deposits has δ³⁴S values from −24.7‰ to 19.7‰ and from −6.0‰ to 13.6‰, respectively. Quartz separates from the Sanqiliu deposit yield δ¹⁸O values of −1.4‰–11.5‰ (mean of 5.8‰) for syn-ore hydrothermal fluids. These stable isotope data indicate that the fluids that formed these deposits were derived from the Sanfang granites, sediments of the Sibao Group, and meteoric sources. In addition, uraninite from the host Sanfang granite yields U–Pb ages of ca. 732–773 Ma. Combining these data with the geology of the ore deposits in this region suggests that these deposits were generated from deeply circulating meteoric water and the uraninite within the highly fractionated Sanfang granite is the source of the uranium within the Sanqiliu and Sanqisi uranium deposits.
... Volatile-rich minerals such as tourmaline, topaz, fluorite, and secondary muscovite are often present in this rock type (e.g., Yu et al., 2007b;Gao et al., 2014a). In addition, muscovite-bearing granites may host uranium ore deposits (e.g., Chen et al., 2012a;Zhao et al., 2016). These observations suggest that their parental magmas would have experienced high degrees of fractional crystallization subsequent to their production. ...
Granitic rocks of Phanerozoic age are common in South China. They are spatially and temporally closely associated
with hydrothermal ore deposits. Therefore, many studies have been devoted to these granites regarding
their petrogenesis. This study presents a review on the geochemistry of Triassic granites in South China because
the Triassic is an important period for the Indosinian orogeny in Southeast Asia. Petrographic investigations
indicate that these granites can be categorized into five groups: cordierite-bearing granites, amphibole-bearing
granites, biotite granites, muscovite-bearing granites, and A-type granites. All these granites are distributed in
regions where magmatic rocks of Neoproterozoic age predominate. From the distribution of Triassic granites and
their associated magmatic rocks, three magmatic zones are discerned: a southwestern zone, a northeastern zone,
and a middle zone. Except for cordierite-bearing granites that were only emplaced in the latest Permian to the
earliest Triassic, the other four groups were emplaced from ≥240 Ma to ~210 Ma. Geochemical data do not
support the possibility that amphibole-bearing granites have a petrogenetic link to mafic magmas through either
magma mixing or assimilation-fractional crystallization. Furthermore, biotite granites do not develop from
amphibole-bearing granitic magmas through fractional crystallization, but some muscovite-bearing granites
have indeed evolved from biotite granitic magmas. A-type granites are mostly peraluminous, and many of them
have metasedimentary sources that previously underwent significant extraction of hydrous felsic melts. On the
basis of the major-trace element characteristics, the initial Nd isotope compositions and relict zircon U-Pb ages of
the Triassic granites, and their spatial overlap with the Neoproterozoic rocks, it is inferred that the Triassic
granites were mainly derived from partial melting of the Neoproterozoic rocks, including both sedimentary and
igneous ones. Although there is a tectonic transition from contraction in the Early Triassic to extension in the
Late Triassic, granitic magmatism is mainly driven by tectonic extension. The Indosinian magmatism is predominated
by reworking of the Neoproterozoic metaigneous and metasedimentary rocks, which are outcropped
in the Neoproterozoic orogen.
The Cretaceous extensional province of the South China Block (SCB), and the decratonization-induced extension in the North China Block (NCB), were both controlled by the Late Mesozoic subduction of the Izanagi/Paleo-Pacific Plate. Different from the metamorphic core complexes exhuming deep crustal rocks of the NCB, extension of the SCB is expressed by numerous half-graben basins and detachment of upper-middle crustal rocks, but its mode and mechanism remain unclarified. At the westernmost of this extensional province, the Early Paleozoic Yuechengling-Miao'ershan Massif, composed of the ductilely deformed Yuechengling pluton and undeformed Miao'ershan pluton, records Late Mesozoic detachment and exhumation. Magnetic fabrics of the western Yuechengling pluton are consistent with structural fabrics, while the NE-SW trending magnetic lineation and NE-SW striking magnetic foliation of the Miao'ershan pluton and the undeformed Yuechengling pluton reflect a pre-existing magma flow structure. Integrating our structural observation, anisotropy of magnetic susceptibility (AMS) results with gravity modeling, we reveal the deep geometry of the extensional dome and restore the original structure before the Late Mesozoic Ziyuan detachment. The mode of extension argues for a single batholith split into two separate massifs, thinning the crust of the central SCB. The shallow-dipping Ziyuan detachment fault (10°-30°) may account for the large horizontal extension but low exhumation of mid-crustal rocks in the SCB, in contrast to the large exhumation of deep crustal rocks in the NCB.
The Changjiang U ore field developed typical granite-related U mineralization in the Zhuguangshan complex, China. Pitchblende is the most important ore mineral in these mineralizations. In this study, the mineralogy and geochemistry of pitchblende were investigated by electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) to identify the genesis of the Changjiang U ore field. Pitchblende exhibits colloidal, fragmented, spherulitic and fine-grained crystals in U ores. Its geochemical compositions are similar to those of other granite-related U deposits in South China, which have elevated contents of U, Sr, As and W; low contents of Pb, Th, Zr, Nb, Ta, Hf, Co, Ni and rare earth elements (REEs); and variable amounts of Ca, Si, Bi, Y, V and Zn. These geochemical signatures suggest that mineralization occurred through hydrothermal genesis and that the hosting Youdong and Changjiang granites acted as the dominant U sources. The uraninite in these granites might be the major U source mineral. Uranium mineralization occurred under the following conditions: low temperature (<250°C), low oxygen fugacity (log fO2=-29.5 - -25.5), weakly acidic (pH=5.3-5.9), high CO3²⁻ and F⁻ contents and a silicon-saturated solution. Rapid changes in the physicochemical conditions of the ore-forming fluid are responsible for the precipitation of pitchblende. Combined with previous studies, we propose that U-rich granites, Cretaceous-Tertiary crustal extensions, regional faults and hydrothermal alterations were the critical factors for U formation in the Changjiang ore field.
Knowledge of Mesozoic tectonic evolution of the eastern South China Block (ESCB) plays a crucial role in understanding the formation of the Large Granitic Province and polymetallic mineralization. This review focuses on two controversial issues: (1) which one was the primary controlling factor of the Triassic geodynamic process of the South China Block (SCB), oceanic subduction or intracontinental convergence? (2) what was the subduction style of the Paleo-Pacific plate during the Jurassic–Cretaceous? Based on the studies of regional deformation analysis and published geochronological, petrological, and Nd isotopic data of the magmatic rocks, we reconstructed the Mesozoic tectonic architecture and determined the temporal and spatial evolution of magmatic activities in the ESCB. The analysis of regional deformation shows that two groups of folds, including NE/NNE-trending folds in the Cathaysia Block and NW/NWW-trending folds in the inland, were formed in the Middle–Late Triassic. Subsequently, the Middle–Late Jurassic NW–SE compression led to large-scale NE-trending fold-thrust deformation in the SCB, excepted for roughly S–N extension in the eastern Nanling tectonic belt, which caused the occurrence of the NE-striking dextral-normal oblique faults. Geochronological data indicate that magmatism in the ESCB can be divided into five separate stages: at 250–210 Ma, 210–170 Ma, 170–145 Ma, 145–120 Ma, and 120–85 Ma, respectively. In the first stage, granitic rocks consist mainly of S- and A-type granites, with subordinate I-type granites. These three types of granites were all derived from the partial melting of Proterozoic rocks. In the second stage, the magmatic activities are characterized by mantle-derived magmas in the coastal area, while they are featured by the mixing of predominantly mantle-derived melts with the Neoproterozoic crust in the inland area. In the third stage, widespread I- and A-type granites, which are characterized by the crust-mantle mixing, were formed in the Nanling tectonic belt and adjacent regions in response to the intense extension of lithosphere. In contrast, the development of crust-derived magmas in the Wuyi tectonic belt indicates a relatively weak lithosphere extension. The granitoids of the fourth stage, which are composed of I- and A-type granites, are mainly distributed in two separate areas, the eastern Jiangnan Orogenic Belt and southeastern Guangdong Province. Their petrogenesis is related to the crust-mantle mixing under the extensional setting. The magmatic activities in the last stage propagated eastward and were developed in the coastal area. The intrusive suites comprise major I- and A-type granitoids, and minor gabbroids, which were formed in an enhanced lithospheric extensional setting. Combined with the records of regional deformation, sedimentology, and magmatic evolution, we propose a new tectonic evolution model for the ESCB covering the range of ca. 270 Ma to 85 Ma. This model demonstrates that the ESCB probably experienced a coeval multi-plate convergence during the Triassic, causing the intracontinental deformation belt in the Yangtze Block and Andean-type retro-arc foreland system in the Cathaysia Block. During the Jurassic–Cretaceous period, the subduction of the Paleo-Pacific plate beneath the SCB triggered crustal thickening, local extension, and large-scale lithospheric extension through the advance, tearing, rollback, and breakoff of the oceanic slab.
To explore the potential of apatite geochemistry as an indicator of petrogenesis and uranium fertility of granites, we analyzed the major and trace elements of apatites from U-bearing (Changjiang and Youdong) and barren (Jiufeng and Fuxi) granites in the Zhuguangshan batholith, South China. All the investigated apatites are identified as fluorapatite that is typical for igneous apatite. Apatites from the U-bearing plutons have higher concentrations of Mn, Fe, Na, and Y, and lower Sr, (Eu/Eu*)N, and (La/Yb)N than those from the barren ones. The compositional variations are interpreted to be related to whole-rock parameters such as SiO2 abundance, oxidation state, and aluminum saturation index. In addition, the presence of other REE-Th-rich minerals such as monazite and allanite can affect REE and Th concentrations in apatites by competing for these elements during apatite crystallization. Concentrations of Sr, Y, and Mn in the studied apatites can serve as a proxy of whole-rock compositions. Apatite compositions indicate that magmas of the U-bearing plutons have higher degrees of magmatic differentiation and lower oxygen fugacity than those of the barren ones. Our results suggest that Sr, Mn, Y, Na, Fe, (La/Yb)N and (Eu/Eu*)N in apatites are effective in distinguishing U-bearing granites from the barren ones. This study highlights the potential of apatite geochemistry to assist in deciphering petrogenesis and uranium fertility of granites.
The South China Uranium Province (SCUP) contains the largest number of discovered uranium deposits in China. This province includes seven uranium mineralization belts, at Wuyishan, Taoshan–Zhuguang, Chenzhou–Qinzhou, Gan–Hang, Xixia–Luzong, Mufushan–Hengshan, and Xuefengshan–Jiuwandashan. The uranium deposits can be classified according to their ore-hosting rocks into four general types: granite-, volcanic-, black-shale-, and sandstone-related. These uranium deposits crop out at the peripheries of Cretaceous–Neogene (K–N) redbed basins or are connected to the basins by NE–SW- to NNE–SSW-trending regional faults. Most of the volcanic-related uranium deposits were formed during the mid-Cretaceous (118 to 88 Ma); granite-related deposits have a wider range of ages from 124 to 11 Ma; the black-shale-related deposits have ages of 120 to 7 Ma; sandstone-related deposits yield ages of 111 to 22.5 Ma. As such, these four types of uranium deposits in South China have similar ages, irrespective of location, and are similar in age to K–N redbed basins in this region. δDVSMOW(fluid) and δ¹⁸OVSMOW(fluid) values of the volcanic-related uranium deposits generally range from – 105.9‰ to – 38.0‰ and – 11.1‰ to +5.3‰, respectively. The black-shale-related uranium deposits yield δDVSMOW(fluid) and δ¹⁸OVSMOW(fluid) values of – 74.5‰ to – 33.0‰ and – 4.4‰ to 9.3‰, respectively. However, the granite-related uranium deposits have a much wider range of δDVSMOW(fluid) and δ¹⁸OVSMOW(fluid) values from – 104.4‰ to – 23.1‰ and – 9.4‰ to +7.3‰, respectively. H–O isotopic compositions of the SCUP ore-forming fluids are similar to those of basinal fluids, again demonstrating the link between the uranium deposits and the basins. The spatial–temporal relationships and fluid isotopic similarities between the K–N basins and uranium mineralization indicate that the uranium deposits of the SCUP are genetically related to the K–N redbed basins, and are unconformity-related uranium deposits.
Hydrothermal alteration records the effects of fluid-rock interactions and can therefore be used to constrain metal mineralization. Although hydrothermal alteration is widely developed in the hydrothermal vein-type uranium deposit in South China, consideration of the elemental mass changes during alteration is rare. The Xiangyangping uranium deposit in the Miao’ershan uranium orefield is mainly hosted by the Douzhashan granite in South China. Observations made at this deposit are used to address hydrothermal alterations and their relationship with elemental mass change. The Xiangyangping deposit is characterized by seven types of alteration appearances, including K-feldspathization, K-mica/illitization, silicification, carbonatization, chloritization, pyritization, and hematitization. Based on the field characteristics, the altered samples in the Xiangyangping deposit were divided into the red-altered (type 1) and grey- altered (type 2) zones. Whole-rock geochemistry of the altered samples in this deposit indicated that there are varying element concentrations depending on the different altered zones: (1) the altered samples in type 1 had higher molar K/Al and lower (2Ca+Na+K)/Al ratios and the altered samples in type 2 displayed lower molar K/Al and lower (2Ca+Na+K)/Al ratios than the least-altered host granitoids; (2) the altered samples in type 1 showed Si, K, Al, P, and Rb gains and Na loss, whereas the samples in type 2 showed Si, K, Al, P, Rb, and Na losses. Alteration assessment results revealed that the samples in type 1 experience moderate K-H metasomatism and intensive Si-metasomatism, and the samples in type 2 underwent intensive K-H metasomatism and weak Si-metasomatism. The samples in type 1 were dominated by conversion of plagioclase to K-mica/illite and K-feldspar, while the abundant K-feldspar grains in the samples of type 2 were altered to K-mica/illite.
The Pingtan deposit in southwestern Hunan Province is a newly-discovered, large-sized W-(Mo) deposit. This deposit is situated in the northwestern part of the Miao'ershan granite batholith, western Nanling Range. The tungsten mineralization is mainly hosted in biotite monzogranite, and the alteration related to mineralization is controlled by a NE-trending fault zone. In this paper, we present new molybdenite Re–Os and zircon U–Pb ages, zircon Lu–Hf isotope and REE geochemical data, aiming to constrain the W (Mo) mineralization age and ore-hosting granite petrogenesis in the Pingtan W (Mo) deposit. Molybdenite Re–Os dating of eight ore samples yielded a weighted average model age of 427.0 ± 5.4 Ma (MSWD = 0.24). The LA-ICP-MS Zircon U-Pb analysis of two biotite monzogranite yielded ²⁰⁶ Pb/ ²³⁸ U ages of 430.8 ± 2.4 Ma and 431.0 ± 1.8 Ma, respectively, suggesting that the W-(Mo) mineralization is spatial-temporally associated with the biotite monzogranite. The ore-related granites have high contents of SiO 2 and K 2 O, belong to weakly to strongly peraluminous (A/CNK = 1.00–1.30), and geochemically classified as S-type affinity. Molybdenite Re contents (2.262–7.297 μg/g), zircon ε Hf (t) (−10.34–−5.87) and ¹⁷⁶ Hf/ ¹⁷⁷ Hf (0.282241–0.282376) values of the biotite monzogranite suggest that the ore-forming materials are predominantly derived from the crust. This is the first identification of tungsten mineralization related to Silurian S-type granites Caledonian granites in the Miao'ershan granite intrusion, indicating Caledonian is an important mineralization period of W in the western part of Nanling Range, South China.
The Hetai goldfield, located at the northern edge of the Yunkai Massif in South China, is a significant gold deposit hosted within the Hetai ductile shear zone (HSZ). The deformation history of HSZ and its correlation with the gold mineralization are problematic. In this study, we conducted detailed field observations and microstructure analyses together with zircon U–Pb and muscovite ⁴⁰Ar/³⁹Ar geochronology on mylonitic granites, aiming to study the deformation features and processes of the ductile shear zone (DSZ) along with their further implications to the gold metallogenic mechanisms of the Hetai goldfield (HGF). The HGF and its periphery have undergone three phases of ductile shear event (DS) since the Palaeozoic: The first DS developed from 468 to 413 Ma, with deformation temperatures above 500°C, accompanied by the formation of large‐scale migmatite and magmatism. The second DS developed from 239 to 211 Ma, with deformation temperatures ranging from 400°C to 500°C and resulted in a low‐angle, top‐to‐the‐SE thrusting. The third DS developed from 198 to 162 Ma, with deformation temperatures between 300°C and 400°C and formed steep, dextral strike‐slip shear zones. The DSs in the HGF have close connection with the gold mineralization. The first DS is coeval with the small‐scale gold mineralization or sulfofication and laid the foundation for later large‐scale gold mineralization. The second DS had no obvious gold mineralization, but the DSZ that developed in this period, together with the earlier DSZs, may have provided a migration pathway for the later gold ore‐forming fluid. Occurrence of the third DS was combined with the main gold mineralization, but the large‐scale gold mineralization mainly occurred during 175–157 Ma, that is, the middle and later periods of dextral strike‐slip. Overall, multiphase DS dominated the large‐scale gold mineralization in this area.
The South Zhuguang uranium (U) ore field in South China, which was discovered in the 1950s, contains an estimated >20,000 t of recoverable U. The U ore is hosted by the Zhuguang granite massif, which is located in the South China Block. The main uranium-bearing mineral, pitchblende, is found mainly in veins along high-angle normal faults, associated with hematite, quartz, fluorite, calcite, and locally pyrite. The hydrothermal alteration is generally silicification, illitization, hematization, and chloritization that developed adjacent to the ore-bearing faults and outwards over hundreds of meters into the unaltered granites.
The ore-forming fluids in the South Zhuguang U ore field can be classified into two stages. Stage I fluids were acidic and oxidizing, with fluoride and sulfate complexes of UO2²⁺ being the dominant species in the fluid. Stage II fluids were alkaline and oxidizing, with carbonate and hydroxide complexes of UO2²⁺ being the dominant species. δ¹⁸O values of syn-ore quartz range from +6.29‰ to +14.30‰, with calculated δ¹⁸OW-SMOW values from −1.85‰ to +5.35‰. δDW-SMOW values of the ore-forming fluids were −104.4‰ to −23.1‰. δ¹⁸O values of the altered granites increase gradually from ∼+4‰ close to ore, to ∼+12‰ in the nearly unaltered granites. The δ¹³C and δ¹⁸O values for syn-ore calcite range from −10.3‰ to −4.3‰ and −22.41‰ to −16.8‰ relative to Pee Dee Belemnite, respectively, with calculated δ¹⁸O and δ¹³C values for water and CO2 of −2.97‰ to +2.83‰ and −11.2‰ to −5.2‰, respectively. The δ³⁴SV-CDT values of syn-ore pyrite range from −17.1‰ to −3.4‰. Initial ⁸⁷Sr/⁸⁶Sr ratios of syn- and post-ore fluorite vary from 0.719250 to 0.721327 and 0.714598 to 0.716299, respectively.
The ore-forming fluids in the South Zhuguang U ore field were sourced primarily from Cretaceous–Paleogene redbed basins in the south, and initially derived from meteoric waters. Hydrothermal alteration associated with stage I fluids released considerable amounts of Ca²⁺ and F⁻ into the ore-forming fluids, increased the fluid pH, decreased the stability of the dominant fluoride complexes, and lowered the saturation solubility of the uranyl ions. Reduction of the ore-forming fluid converted U⁶⁺ into U⁴⁺, which resulted in the deposition of pitchblende–fluorite–quartz veins of the stage I ore in fractures along with pyrite. During stage II, the U mineralization was controlled mainly by CO2 degassing, which resulted in decomposition of the carbonate complex UO2(CO3)2–, and deposition of U in pitchblende–calcite–quartz veins as the ore-forming fluid was reduced.
The southeastern part of the Nanling metallogenic province, South China contains numerous economically important granite-hosted, hydrothermal vein-type uranium deposits. The Miao’ershan (MES) uranium ore field is one of the most important uranium sources in China, hosts the largest Chanziping carbonaceous-siliceous-pelitic rock-type uranium deposit and several representative granite-hosted uranium deposits. The geology and geochemistry of these deposits have been extensively studied. However, accurate and precise ages for the uranium mineralization are scarce because uranium minerals in these deposits are usually fine-grained, and may have formed in several stages, thus hindering the understanding of the uranium metallogenesis of this province.
The Menggongjie (MGJ) uranium deposit is one of the largest granite-hosted uranium deposits in the MES ore field. Uranium mineralization in this deposit occurs at the central part of the MES granitic complex, accompanied with silicification, fluorination, K-metasomatism and hematitization. The ore minerals are dominated by uraninite, occurring in quartz or fluorite veinlets along fractures in altered granite. In-situ SIMS U-Pb dating on the uraninite yields the U–Pb isotopic age of 1.9 ± 0.7 Ma, which is comparable to the chemical U-Th-Pbtol uraninite age of 2.3 ± 0.1 Ma. Such ages agree well with the eruption ages of the extension-related Quaternary volcanics (2.1–1.2 Ma) in South China, suggesting that the uranium mineralization have formed at an extensional setting, possibly related to the Quaternary volcanic activities. Therefore, our robust, new dating results of the MGJ uranium deposit make it the youngest granite-hosted uranium deposit reported so far in South China and the mineralization event represents a newly identified mineralization epoch.
SUMMARY: Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs.
In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (≤1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (≤2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by
Metasedimentary granulite enclaves hosted in the Indo-Sinian Darongshan–Shiwandashan granite belt from the southeastern Guangxi province, South China, experienced a three-stage metamorphic evolution: (1) the early prograde metamorphism in the stability field of sillimanite at ~ 800 °C; (2) the peak metamorphism with a mineral assemblage of spinel + quartz at 7.5–8.0 kbar and 950–1000 °C (260–250 Ma); and (3) a near-isothermal decompression stage with orthopyroxene + plagioclase and orthopyroxene + cordierite symplectic textures at 3.2–3.7 kbar and 790–820 °C (240–230 Ma). The clockwise P–T–t path suggested that the granulite enclaves have undergone initial crustal thickening and subsequent rapid exhumation and cooling history.
The Miaoershan uranium (U) ore field in northeastern Guangxi is one of the important granite-related U deposits in south China and is closely related to the Douzhashan U-bearing granite. The Douzhashan granite contains primary U-rich accessory minerals, including monazite (UO2 = 0.98−1.75 wt%) and xenotime (UO2 = 1.48–6.14 wt%). Primary monazite and xenotime yield chemical ages of 231 ± 28 Ma and 230 ± 38 Ma by electron microprobe analysis and U-Pb isotopic ages of 220±6 Ma and 211±7 Ma by laser ablation-inductively coupled-mass spectrometry respectively. These ages demonstrate that the Douzhashan granite formed during the period of Indosinian magmatic activity. Back scattered electron imaging shows that monazite and xenotime are commonly altered to assemblages of low-U synchisite and apatite, which was associated with loss of U to hydrothermal fluids. U-Th-Pb analyses of secondary apatite yielded a chemical age of 136 ± 17 Ma, which corresponds to the timing of Cretaceous-Tertiary crustal extension in south China. We suggest that the heat and CO2 required for mineralization was the result of Yanshanian crustal extension, and that this triggered the breakdown of U-rich accessory minerals in the Douzhashan U-bearing granite. Uranium remobilization from the Douzhashan granite provided materials for mineralization within the granite and/or surrounding country rocks. Therefore, a combination of Indosinian compression and Yanshanian extensional overprint produced the hydrothermal U deposits associated with the Douzhashan granite.
The analysis of ore-forming conditions suggests a common point in the main uranium deposits of Wuyi volcanic uranium mineralization belt that they all have granite as the basement rokes. Gaoxi and Fucheng granitic basement rocks are chosen for geochemistry study in this paper. The two granite rocks are all composite granite batholith, the host body rocks were formed in the late stage of Indosinian epoch (214. 6Ma: 216Ma). The potassium feldspars in the two granites are of highly ordered microcline and biotites are of annite and siderophyllite. In the petrochemical aspect, these two granites are cheracterized by abundant silicon and alkali content and oversaturated aluminium. With respect to their trace elements, Gaoxi and Fucheng granites have low concentration of Co, Ni, Cr, Sr and Ba, low Sr/Ba ratio, and high concentration of Rb, Nb, Pb, Zn and high ratio of Rb/Sr. The REE content of these two granites are high, HREE and LREE/HREE ratios are relatively higher with stong-medium depletion of europium. Gaoxi and Fucheng ganites have high Sr isotope compositions ( 87Sr/ 86Sr)j = 0. 71239 or 0.7198, low Nd isotope compositions ε Nd(i) = -6.-62- -12. 84. Mineralogical, petrochemical, and geochemical features suggest that Gaoxi and Fucheng intrusions are typical transformation type granites. The ratios of active uranium in these two granites are high, espcially in alteration, these ratios increase. According to the study of Pb isotope tracer', it is showed that the uranium in the two granites has been lost in large amount in process of the alteration, and the Pb isotope compositions of granites and ores are both closely located to the evelutionary curve of the orogenic belts, especially the Pb isotope compositions of ore, volcanic rock, granite and metamorphic rock show linear correlation. So it is thought that Gaoxi and Fucheng granites are one of uranium source bodies of 570 and 6722 deposits.
Miaoershan (MES) uranium ore field is one of the most important uranium sources in China, hosts the largest Chanziping carbonaceous-siliceous-pelitic rock type uranium deposit in South China together with many other granite-hosted uranium deposits. The Shazijiang (SZJ) uranium deposit is one of the representative granite-hosted uranium deposits in the MES uranium ore field, situated in the Ziyuan, Guangxi Province, South China. Uranium mineralization in the SZJ deposit mainly occurs as uraninite with quartz and calcite veins that is spatially associated with mafic dykes in the region. The hydrothermal alteration includes silicification, carbonation and hematitization. New uraninite chemical U-Pb geochronology and petrographic evidences provide the timing constraints and new insights into the formation of the SZJ uranium deposit. The results show that the first stage of uranium mineralization formed at 97.5±4.0 Ma, whereas another stage of uranium mineralization occurred at 70.2±1.6 Ma. Two stages of uranium mineralization are fairly consistent with two episodic crustal extensions that occurred at ~100 and ~70 Ma throughout South China. This study indicates that there are two uranium mineralization events in SZJ uranium ore field controlled by mafic dyke, supporting that mafic dykes play an important topochemical role in uranium concentration and/or mobilization. Therefore, geochemical U-Pb age firstly reinforces that ore-forming age of the SZJ uranium deposit mainly yields at 97.5±4.0 and 70.2±1.6 Ma. Additionally, geochemical age method is particularly useful for interest samples which record information on multi-stage uranium mineralizations in South China. © 2015, China University of Geosciences and Springer-Verlag Berlin Heidelberg.
The Xiajiang uranium ore deposit in Jiangxi Province is one of the granite-hosted uranium ore deposits in South China. The uranium orebodies are hosted by the Jintan granitic batholith in the Jiangxi Province. Field geological survey and zircon U-Pb dating indicated that the Jintan batholith is composed of two stage Indosinian granites. The U-bearing two-mica granite was emplaced at 239 ± 1Ma, and the porphyritic biotite granite was emplaced at 226 ±2Ma. The two-mica granite has high SiO2 contents (74.09% ∼ 74.53%) and low TiO2, CaO and MgO contents. A/CNK values of the granites vary from 1.20 to 1.46, which is consisted with that the granite contains muscovite and garnet. The two-mica granite belongs to typical strongly peraluminous S type granite. However, the porphyritic biotite granite shows different geochemical characteristics. It has relatively higher HFSE and REE contents, lower Rb/Sr ratios and less pronounced negative Eu anomalies. A/CNK values of the porphyritic biotite granite vary from 1.05 to 1.13. Both of the granites have low εNd(t) values (-9.0 to -8.8 for the two-mica granite and -9.8 to -9.4 for the porphyritic biotite granite) with Paleo-proterozoic model ages (1.73 ∼ 1.75Ga for the two-mica granite and 1.77 ∼ 1.80Ga for the porphyritic biotite granite). Geochemical and isotopic characteristics indicate that both the two-mica granite and the porphyritic biotite granite belong to S-type granite. However, the two-mica granite should be derived from anatexis of clay-rich pelitic rocks and the porphyritic biotite granite from partial melting of clay-poor psammitic rocks. We suggested that the two-mica granite formed earlier from dehydrate-melting of crust at syn-collisional compressional environment and the porphyritic biotite granite formed later at the post-collisional extensitional environment. The two-mica granite contains higher U contents, and its mineralogical and geochemical characteristics are similar to those of typical U-bearing granites in South China. Comparative studies indicate that Indosinian U-bearing granites in South China are likely formed from anatexis of pelitic rocks during syn-collisional compressional tectonic regime.
The Maofeng granite is of great importance because of hosting several uranium ore deposits though it is small within the Guidong granite composite in northern Guangdong province. Zircon U-Pb dating yields 219.6 ± 0.9Ma, which suggests that it was produced in the Indosinian magmatism event. In geochemistry it is strongly peraluminous and characterized by enrichment of silicon, alkalis, Rb, Th, U, Ce, Sm and Y, by low CaO/Na2O ratios, and by depletion of Ba, Sr and Ti. It displays slight enrichment of LREE (LREE/HREE = 1.70-9.63, (La/ Yb)N=0.41-6.25)) and strong depletion of Eu (δEu = 0.02-0.22). It also has low εNd (t) values (-12.3 - -10.8) with old Nd model ages (1879 - 1996Ma) and has varying δ 18O values from 4.1 to 11.3‰, (87Sr/86Sr): from 0.71049 to 0.73359), 206Pb/204Pb from 18.345 to 22.019, and 207Pb/207Pb from 15.646 to 15.863. These features consistently indicate that the Maofeng granite belonged to crust sourced type of granite and was derived from partial melting of Paleoproterozoic heterogeneous sedimentary metamorphic rocks under a tectonic setting of crust extension in the late Indochina Period.
The Fucheng granitic complex is located in the southeastern Jiangxi province, which is combined with the Hongshan granite in the southwestern Fujian province to be the Fucheng-Hongshan Complex. The Fucheng Complex may be divided to three units, the Fucheng megacrystic porphyrotic biotite monzogranite, the Cushiba middle-grained two-mica granite and the Zhuchangdong andalusite-bearing fine-grained granite. The Fucheng biotite granites have relatively low SiO2, Rb and Nb concentrations and high Al2O3, Ba, Sr, Zr, REE concentrations. Their ACNK are > 1.10 and K2O/Na2,O > 1.60. The Cushiba granites are characterized by high SiO2, K2O and Al2O3 (ACNK = 1.13∼1.20), and low CaO and P2,O5. The rocks are rich in Rb and Nb, and poor in Ba, Sr, Zr and REE. They all have relatively low K/Rb and Eu/Eu ° ratios. The Zhuchangdong andalusite-bearing granites are similar to the Fucheng granites in geochemistry, except for higher ACNK (1.22∼1.36), Cs, Rb, Nb, Ta and Sn concentrations and lower Sr, Ba, Zr, Hf and REE contents. The Fucheng granites have initial 87Sr/86Sr ratios of 0.7135∼0.7196 and εNd (t) of -9.4∼10.2 with the Nd model ages ranging from 1.84Ga to 1.78Ga. The zircons in the Fucheng granite have Hf model ages of 1.70 ∼ 1.89Ga, consistent with bulk Nd model ages. The Cushiba granites have bulk Nd isotope and zircon Hf isotope similar to the Fucheng granites, The Zhuchangdong granite has higher initial 87Sr/86Sr ratio (0.7214) and lower εNd (t) value (-16.9) with older Nd model age (2.37Ga). These geochemical data indicate that the protoliths of granites in the Fucheng Complex are sedimentary rocks consisting of ancient crustal materials. The original magma of the Fucheng and Cushiba granites probably originated from late Paleoproterozoic basement, and the source of the Zhuchangdong granites is early Paleoproterozoic basement. A variety of granites from the three units in the complex do not exhibit coherent geochemical change, suggesting they are not the results evolved from an original magma, which also is supported by field observation and geochronological studies. The difference in geochemistry among granites from three units is likely caused by the source compositions. LA ICPMS zircon U-Pb dating indicates that the Fucheng granite formed at ca. 239Ma, and the Cushiba and Zhuchangdong granites formed at 231 ∼ 229 Ma, which are in accordance with peak time of early Indosinian tectonic-magmatic activity in south China. Coupled with the geochemical characteristics and assemblage of Indosinian rocks, it is suggested that the Fucheng-Hongshan granitic complex was probably formed in the syn-orogenic tectonic setting.
This chapter reviews the present-day composition of the continental crust, the methods employed to derive these estimates, and the implications of the continental crust composition for the formation of the continents, Earth differentiation, and its geochemical inventories. We review the composition of the upper, middle, and lower continental crust. We then examine the bulk crust composition and the implications of this composition for crust generation and modification processes. Finally, we compare the Earth's crust with those of the other terrestrial planets in our solar system and speculate about what unique processes on Earth have given rise to this unusual crustal distribution.
The Douzhashan granite is mainly composed of medium-to fine-grain two-mica monzonitic granite and great importance because of hosting several uranium ore deposits within the middle of the Miaoershan granitic complex in northeastern Guangxi province. Signle zircon SHRIMP U-Pb dating yields 228 ± 11Ma, which suggests that this granite formed during Indosinian. In geochemistry, it is strongly peraluminous and characterized by enrichment of silicon, alkalis, Rb, Th, U and Ta, low CaO/Na2O ratios, depletion of Ba, Sr and Ti. The ΣREE has the range of 30.24 × 10-6 - 139.18 × 10-6, slight enrichment of LREE(LREE/HREE = 4.00 - 6.35, (La/Yb)N = 3.24 - 6.74), and strong depletion of Eu (δEu = 0.14 - 0.19). According to correlative geological data, the Douzhashan granite belongs to crust sourced type granite and was derived from partial melting of metamorphic rocks under a tectonic setting of thinning and extension of crust during the late Indosinian period.
The stable accessories apatite and zircon occur in almost all types of igneous rocks, but for other accessory minerals the initial trace-element contents of the magma, trace-element ratios during magmatic evolution, CaO content of the magma, silica oversaturation, and peralkaline index are important parameters which control their stability and abundance. Physical parameter (P, T, fO2) controls are generally less critical. All these parameters allow deduction of the crystallization logic of accessory minerals in three main types of granites frequently enriched in U: high-Ca metaluminous granites, low-Ca peraluminous granites and peralkaline granites. The low-Ca peraluminous granites are the most favourable for the crystallization of a large part of initial magmatic U content as easily leachable uraninite; this represents the most important source for intra- and perigranitic vein-type deposits. High-Ca metaluminous granites are characterized by the occurrence of sphene; the occurrence of allanite, uranothorite and uraninite depend on the relative abundance of REE, Th and U in the magma and the amounts of REE incorporated in the major rock-forming minerals. Peralkaline granites are characterized by abundant zircon + or - pyrochlore, columbite, uranothorite, monazite, etc; uraninite is generally rare as U is fractionated between abundant accessories. -R.A.H.
Multi-constraints are used in this paper to discuss the ∑CO2 source in ore-forming hydrothermal solution of granite-type uranium deposit in South China. The studies show that highly acidic and uraniferous granitic magma cannot produce the fluid rich in ∑CO2. Controlled by three periods of crust extension and corresponding to three major periods of U-mineralization in South China respectively, the ∑CO2 in each ore-forming hydrothermal solutions is all mantle-derived. Our studies reasonably explain why the mineralization did not occur immediately after the end of differentiation of the granitic magma rich in uranium, and why the ore-forming time of granite-type uranium deposit focuses on the time of crust extension after the formation of the uraniferous granites.
After a discussion on the condensation of elements from the solar nebula, the REE abundances in Ca,Al-rich inclusions in carbonaceous chondrites are described and interpreted. The normalization values for REE in chondrites are examined at some length and the values of REE in other differentiated meteorites are reported.-R.A.H.
Granite-hosted uranium ore deposits are the most important commercial U-producers in South China. These U-bearing granites generally contain high-U-concentration zircons. Zircons in the U-bearing Douzhashan Granite show black rims in cathodoluminescence images, which have very high U concentrations of up to > 25,000 ppm. The high-U black rim domains of zircons show similar REE patterns to those of low-U mantle domains with oscillatory zoning, but have higher REE concentrations and weaker positive Ce anomalies. The high-U black rim domains of zircons may have formed from late-stage evolved U-rich and H2O-rich magma. We carried out a SHRIMP U-Pb dating for these zircons and the results show that the high-U (12,007–26,706 ppm) rim domains of the zircons always yield older 206Pb/238U ages (268 ± 9 Ma, n = 5, MSWD = 2.7) than the low-U (558–3667 ppm) mantle domains (228 ± 11 Ma, n = 4, MSWD = 3.1), and both of these ages are older than the emplacement age (211 ± 3 Ma) of the U-barren Xiangchaoping Granite, which was intruded by the Douzhashan Granite. Hence, these results demonstrate a matrix effect associated with SHRIMP U-Pb analyses of high-U zircons. The reverse discordance for SHRIMP results of high-U zircons was produced by analytical artifact. However, our LA-ICP-MS analyses show that the black rim domains (12,840–26,018 ppm U) of the zircons have the same U-Pb ages as the low-U mantle domains (1215–4075 ppm U). Both domains yield a weighted mean 206Pb/238U age of 203 ± 4 Ma (n = 13, MSWD = 1.4), which is consistent with the 40Ar-39Ar age (207 ± 4 Ma) of muscovite from this granite. It thus indicates that LA-ICP-MS U-Pb analyses for high-U zircons (up to 26,000 ppm U) show an insignificant matrix effect and likely yield more reliable U-Pb ages for the high-U zircons than SHRIMP analyses. In order to get reliable U-Pb ages using the LA-ICP-MS method for the high-U zircons, a pulse-analog cross calibration for the ICP-MS collector should be performed. Our precise U-Pb dating and geochemical studies indicate that the U-bearing Douzhashan Granite was emplaced during the late Indosinian stage and formed in a post-collisional setting of the Indosinian Orogeny. It is distinct from most U-bearing Granites in South China, which were largely emplaced during the early Indosinian stage and formed in a syn-collisional setting.
A skin prick test was conducted to evaluate the skin allergic reaction of piglets caused by allergenic proteins contained in soybean meal. The data accumulated from subcutaneous piglet skin tissue indicated that allergenic proteins contained in soybean meal crude extracts, even in low dosage levels (7 μg), caused immunological redness and inflammation within 5 min. The dosages above 200 μg of β-conglycinin caused inflammation covering a larger area. The glycinin had less of an influence on skin allergenic reaction dosages than β-conglycinin did. The antibodies used for β-conglycinin and glycinin subunits did not exhibit cross-recognition to other subunits or Leguminosae members, such as green beans, lupins and red beans. The polyclonal antibodies further indicated that some allergenic proteins were present after examining soybean meal fermented products individually by Aspergillus or Lactobacillus. None of the allergenic proteins were detected in soybean meal underwent two-stage fermentation. The skin prick test was found to be a convenient method for evaluating the skin allergic reaction of soy allergenic proteins in piglets. The produced polyclonal antibodies are based on subunits of allergenic proteins and can be used to detect the allergenic proteins present in soya products and soybean meal fermented products.
A detailed study utilizing zircon U-Pb dating, major and trace
element geochemistry, and Sr-Nd-Hf isotope geochemistry has
been carried out for the Caijiang granite in Jiangxi Province and the
Gaoxi granite in Fujian Province, South China. The new data indicate
that the Caijiang and Gaoxi granites are Triassic (228-230 Ma) and
have the petrographic and geochemical characteristics of A-type
granites. In both granites, biotite occurs along the boundary of
euhedral plagioclase and quartz, which implies that the primary magma
could have been anhydrous. The two granites show high contents of total
alkalis (Na2O + K2O = 7.81-12.15%), high
field strength elements (e.g. Zr = 240-458 ppm, Y =
16.8-38.0 ppm, Nb = 13.5-33.8 ppm and Zr + Nb + Ce + Y =
382-604 ppm) and rare earth elements (total REE = 211-373
ppm) as well as high Ga/Al ratios (10000 × Ga/Al =
2.41-3.53). The lowest magmatic temperatures estimated from zircon
saturation thermometer were 800-840 °C for the Caijiang
granite and 820-850 °C for the Gaoxi granite, respectively.
The Caijiang granite has relatively high
(87Sr/86Sr)i ratios of 0.71288 to
0.72009, low ɛNd(t) values of - 9.9 to -
9.3, and low zircon ɛHf(t) values (peak value of
- 7.5). Whole-rock Nd isotopic model ages and zircon Hf isotopic
model ages mostly vary from 1.65 Ga to 1.80 Ga. The Gaoxi granite has
also high (87Sr/86Sr)i ratios of
0.71252 to 0.71356, low ɛNd(t) value of - 13.8
and low zircon ɛHf(t) values (peak value of -
12.0). Whole-rock Nd isotopic model ages and zircon Hf isotopic model
ages mostly vary from 1.95 Ga to 2.10 Ga. According to these data, we
suggest that the two granites might have been derived from partial
melting of Precambrian crustal rocks that had been granulitized during
an earlier thermal event. Our study of the Caijiang and Gaoxi granites,
together with previous studies on two Triassic alkaline syenites
(Tieshan and Yangfang) in Fujian Province and one A-type granite
(Wengshan) in Zhejiang Province in South China, indicate a wide
transtensional tectonic environment in the Cathaysia Block that lasted
at least from 254 Ma to 225 Ma. Combined with extant data for the
Indosinian granites and tectonic evolution in South China, we suggest
that the formation of A-type granites was related to the local
NE-trending extensional faults probably caused by collision between the
South China Block and the Indochina Block or the North China Block.
The Luxi and Xiazhuang granitic plutons are parts of the Guidong granite
belt in northern Guangdong Province, China. They occur next to each
other and have similar crystallization ages. However, the Xiazhuang
pluton hosts several important uranium (U) ore deposits, whereas the
Luxi pluton does not. This study compares the two plutons using
whole-rock geochemistry, biotite compositions, zircon U-Pb ages by
LA-ICPMS, and in situ zircon Hf isotope data by LA-MC-ICPMS, to
understand the fundamental controls. Results show that the two plutons
have similar ages, 237 Ma for the Luxi pluton and 234 Ma for the
Xiazhuang pluton. They also have similar geochemical features that are
characteristic of S-type granites. Zircons from both plutons have
negative ɛHf(t) values (- 9 to - 12) and
a Paleoproterozoic two-stage Hf model age (TDM2 = 1838 Ma to
2025 Ma), suggesting that their parental magmas were all derived from
Paleoproterozoic metasedimentary rocks. The geochemical and petrological
data suggest that these two plutons crystallized from magmas derived
from the same parent at different stages, the parental magma of the
Xiazhuang pluton is more evolved than that of the Luxi pluton. This
factor, plus different physical-chemical conditions (such as
temperature, volatile components and oxidation state) resulted in higher
U content and favorable U-bearing species in the Xiazhuang magmatic
hydrothermal system. U occurs mainly as uraninite in the Xiazhuang
pluton, which facilitates U transfer from granite into
CO2-rich hydrothermal fluid to form U ore deposits. In
contrast, U occurs mainly as REE-bearing minerals in the Luxi magmatic
system, preventing U transfer to associated hydrothermal fluids. As a
result, the Xiazhuang pluton hosts several important uranium ore
deposits, whereas the Luxi pluton is ore-barren.