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1.
This study reports major, minor, and trace element data and Sr isotope ratios for 11 uranium ore (uraninite, UO2+x) samples and one processed uranium ore concentrate (UOC) from various U.S. deposits. The uraninite investigated represent ores formed via different modes of mineralization (e.g., high- and low-temperature) and within various geological contexts, which include magmatic pegmatites, metamorphic rocks, sandstone-hosted, and roll front deposits. In situ trace element data obtained by laser ablation-ICP-MS and bulk sample Sr isotopic ratios for uraninite samples investigated here indicate distinct signatures that are highly dependent on the mode of mineralization and host rock geology. Relative to their high-temperature counterparts, low-temperature uranium ores record high U/Th ratios (>1000), low total rare earth element (REE) abundances (<1 wt%), high contents (>300 ppm) of first row transition metals (Sc, Ti, V, Cr, Mn, Co, Ni), and radiogenic 87Sr/86Sr ratios (>0.7200). Comparison of chondrite normalized REE patterns between uraninite and corresponding processed UOC from the same locality indicates identical patterns at different absolute concentrations. This result ultimately confirms the importance of establishing geochemical signatures of raw, uranium ore materials for attribution purposes in the forensic analysis of intercepted nuclear materials. 相似文献
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二连盆地是我国砂岩型铀矿的重要产地之一,已相继发现了多个砂岩型铀矿床. 盆地中部赛汉高毕-苏尼特左旗地区南北缘发育大量古-中生代的花岗岩体,铀源丰富;且该区发育北东向展布的巴彦乌拉、赛汉高毕等古河道,为铀矿体的形成和保存提供了有利的构造条件,具有较好的找矿前景. 目前针对该地区砂岩型铀矿的勘查主要是通过地球物理勘探（电法、地震、重力、航磁）和钻探,常规的地球化学勘查方法在该区效果不理想. 为了满足大范围找矿勘查的需求,基于土壤微细粒分离测量技术在赛汉高毕-苏尼特左旗地区开展1∶25万区域化探扫面工作. 2 821件土壤样品中Hg、As、Mo、F、Zr、Sr、Sb、Li、Th、U等元素既有相对较高的富集系数,又有相对较大的变异系数. 通过元素相关分析和R型聚类分析将其分为Zr?Th?U?Mo组合和As?Sb?F?Li?Sr?Hg组合,优选U?Mo为铀矿的成矿指示元素. 依据U?Mo衬值地球化学综合异常圈定了3个铀矿找矿有利地段,其中地段I和II位于盆地次级坳陷内部,异常与古河道砂体有关,寻找砂岩型铀矿的潜力较大. 相似文献
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4.
ANDREOLI MARCO A. G.; HART RODGER J.; ASHWAL LEWIS D.; COETZEE HENK 《Journal of Petrology》2006,47(6):1095-1118
The digital image of airborne radiometric data across SouthAfrica reveals that the largest anomaly, 100 nGy/h, is causedby the granulite-facies rocks of the Namaquan metamorphic complex,whereas most of the country is <60 nGy/h. This observationis consistent with geochemical data that show that the 1900± 100 Ma greenschist-facies Richtersveld Terrane nearNamibia (max. U = 3·4 ppm; Th = 20·1 ppm) andthe adjacent, 1100 ± 100 Ma, amphibolite-facies Aggeneys/SteinkopfTerranes (max. U 10 ppm; Th 52 ppm) are the least enrichedin U, Th and K. In contrast, the lower-T granulite-facies OkiepTerrane near Springbok hosts more enriched granites (max. U 17 ppm; Th 66 ppm) and noritic intrusions (max. U = 14 ppm;Th = 83 ppm). The most enriched rocks are found in the 1030Ma higher-T granulite-facies core of the Namaquan belt and includequartzo-feldspathic gneisses (max. U = 46 ppm; Th = 90 ppm)and charnockites (max. U = 52 ppm; Th = 400 ppm). Our findingscontradict the notion that granulite-facies terrains are characteristicallydepleted in U and Th. In this study we modeled the heat productionin the core of the Namaquan complex, where the granulites havehad a very unusual metamorphic history, and show that ultra-high-T(1000°C, P 10 kbar) metamorphic conditions could have beenachieved by radiogenic heating without invoking external heatsources. However, monazite-rich veins of charnockite and patchesof granulites mark the passage of CO2-dominated melts and fluidsderived from fractionated noritic intrusions. KEY WORDS: charnockite; granulite; Namaqualand; thorium; uranium; radioactive heating; metamorphism 相似文献
5.
Sikta Patnaik G. N. Hegde A. Panneerselvam M. B. Verma R. Mohanty A. K. Rai 《Journal of the Geological Society of India》2016,88(2):151-158
Granite core samples (n=14) from the Gogi-Kurlagere fault zone in the central part of the Bhima basin were studied in terms of LREE, Y and Zr mobility during uranium mineralization. LREE, Zr and Y along with LILE (Ba, Rb) and P show behavioral differences in the mineralised and the non-mineralised samples. Average ΣLREE in mineralised granite (240 ppm) is higher than in non-mineralised samples (157 ppm). The average Zr and Y in the mineralised granite are 193 ppm and 17 ppm, while the corresponding abundances of these elements in non-mineralised portion are 148 ppm and 11 ppm respectively. Besides enrichment of U, Th, Ba, Pb and Rb and depletion of Sr are observed in mineralized granite in comparison to non-mineralized granite. Hydrothermal alteration has led to the mobility of these elements, which again dependent on the overall geochemical behavior of the migrating fluid. REE and Y in association with uranyl [(UO2)2+] ion were transported as carbonate complexes like [UO2(CO3)3]4- and [REE (CO3)3]3- and were later incorporated into favourable structural loci by precipitating minerals like pitchblende and coffinite. 相似文献
6.
Abstract: The black shales of the Lower Cambrian Niutitang Formation in Weng’an, on the Yangtze platform of south China, contain voluminous polymetallic sulfide deposits. A comprehensive geochemical investigation of trace, rare earth, and platinum group elements (PGE) has been undertaken in order to discuss its ore genesis and correlation with the tectono-depositional setting. The ore-bearing layers enrich molybdenum (Mo), nickel (Ni), vanadium (V), lead (Pb), strontium (Sr), barium (Ba) , uranium (U) , arsenic (As), and rare earth elements (REE) in abundance. High uranium/thorium (U/Th) ratios (U/Th>1) indicated that mineralization was mainly influenced by the hydrothermal process. The dU value was above 1.9, showing a reducing sedimentary condition. The REE patterns showed high enrichment in light rare earth elements (LREE) (heavy rare earth elements (HREE) (LREE/HREE=5–17), slightly negative europium (Eu) and cerium (Ce) anomalies (dEu=0.81–0.93), and positive Ce anomalies (dCe=0.76–1.12). PGE abundance was characterized by the PGE-type distribution patterns, enriching platinum (Pt), palladium (Pd), ruthenium (Ru) and osmium (Os). The Pt/Pd ratio was 0.8, which is close to the ratios of seawater and ultramafic rocks. All of these geochemical features suggest that the mineralization was triggered by hydrothermal activity in an extensional setting in the context of break-up of the Rodinian supercontinent. 相似文献
7.
The black shales of the Lower Cambrian Niutitang Formation in Weng'an.on the Yangtze platform of south China,contain voluminous polymetallic sulfide deposits.A comprehensive geochemical investigation of trace,rare earth,and platinum group elements(PGE)has been undertaken in order to discuss its ore genesis and correlation with the tectono.depositional setting.The ore-bearing layers enrich molybdenum(Mo),nickeI(Ni),vanadium(V),lead(Pb),strontium(Sr), bariam(Ba),uranium(U),arsenic(As),and rare earth elements(REE)in abundance.High uranium/thorium(U/Th)ratios(U/Th>1)indicated that mineralization was mainly influenced by the hydrothermal process.The δU value Was above 1.9.showing a reducing sedimentary condition.The REE patterns showed high enrichment in Iight rare earth elements (LREE)(heavy rare earth elements (HREE)(LREE/HREE=5-17),slightly negative europium(EU)and cerium(Ce)anomalies(δEu=0.81-0.93).and positive Ce anomalies(δCe=0.76-1.12).PGE abundance was characterized by the PGE-type distribution patterns,enriching platinum(Pt),palladium(Pd),ruthenium(RuJ and osmium(Os).The Pt,Pd ratio was 0.8.which is close to the ratios of seawater and ultramafic rocks.AII of these geochemical features suggest that the mineralization was triggered by hydrothermal activity in an extensionai setting in the context of break-up of the Rodinian supercontinent. 相似文献
8.
Background values of U and Th in 371 clastic sedimentary rocks from the Catskill Formation correlate negatively with Si and positively with Al and most other major elements because of the low content of U and Th in quartz and the relative enrichment in clays, Fe oxides, and other fine-grained components. Background U also correlates closely with Th. Similar results are obtained from 100 samples from western Colorado near the Uravan mineral belt. Weak anomalies in U are much more easily recognized by study of residuals or deviations from regressions of U against Al or Th than in the raw data.At Penn Haven Junction near Jim Thorpe, Pa., roll-type uranium deposits similar to those in Wyoming are localized around an iron-stained paleo-aquifer of conglomeratic sandstone. Twenty-four rock samples from this paleo-aquifer contain 1–12 ppm U; eight of the samples contain less than 4 ppm U, the background level for shales of the area. Uranium residuals from regressions against Al or Th are clearly anomalous for all samples. Experiments on another group of samples suggest that readily extractable U (H2O2-acetic acid leach) would also show the paleo-aquifer to be anomalous.Anomalies of this type in paleo-aquifers should be useful in evaluation of drill holes, outcrops, and radiometric data in prospective districts, especially when paleo-aquifers are difficult to recognize visually. The anomalies also indicate that U is added to sandstones of the paleo-aquifer rather than leached out to form the ore bodies in reduced rocks at the margins of a geochemical cell. 相似文献
9.
《International Geology Review》2012,54(11):1296-1308
Geochronological, geochemical, and whole-rock Sr–Nd isotopic analyses were performed on a suite of Palaeozoic nepheline syenites from Zijinshan to characterize their ages and petrogenesis. Laser ablation inductively coupled plasma-mass spectrometry U–Pb zircon analyses yield consistent ages of 525.7 ± 2.8 million years for a sample (HYK01). These intrusive rocks belong to the foid syenite magma series in terms of K2O?+?Na2O contents (14.3–15.2 wt.%) and to the shoshonitic series based on their high K2O contents (5.42–5.61 wt.%). The nepheline syenites are further characterized by high light rare earth element contents [(La/Yb) N ?=?29.1–36.1]; show modest negative Eu anomalies (δEu?=?0.5–0.6) and positive anomalies in Rb, Th, U, Pb, Zr, and Hf; are depleted in Ba and high field strength elements (P and Ti). In addition, all the nepheline syenites in this study display relatively low radiogenic Sr (87Sr/86Sr) i (0.7042–0.7043) and positive ?Nd (t) (0.7–0.8). These results suggest that the nepheline syenites were derived from depleted continental crust. The parent magmas likely experienced fractional crystallization of plagioclase, Ti-bearing oxides (e.g. rutile, ilmenite, and titanite), apatite, and zircon during ascent, with negligible crustal contamination before final emplacement at a high crustal level. 相似文献
10.
High‐resolution gamma ray spectrometry was exploited to locate the potential radioactive targets at Kab Amiri granite pluton, Central Eastern Desert, Egypt. The Kab Amiri pluton forms a concentric granitic body of monzogranite to syenogranite composition intruded into mafic‐ultramific rocks. To identify and detect anomalous concentrations of natural radioactive elements in the study area, contour maps of equivalent uranium (eU ppm), equivalent thorium (eTh ppm), potassium (K%) and their geochemical ratios (eU/Th, eTh/K and eU‐eTh/3.5) as well as standard deviation map of uranium were constructed and interpreted. Qualitative and quantitative interpretations of the spectrometric survey data revealed the presence of seven radioactive anomalies in the south of the studied area. These anomalies could be related to the prevailing faulting directions NE and ENE fault trends. The southernmost anomalous zone is related to high episyenitization and uranium concentrations. It exhibits a sharp increase in the eU concentrations reaching 370 ppm resulting in a high eU/eTh ratio reaching 4.5 and characterized by oval shape trending in the NE direction. Constructing the contour map of the (eU‐eTh/3.5) was helpful in defining the trends of uranium migration and enabling the delineation of the limit between the negative contours (leaching) and positive contours (deposition). 相似文献
11.
H. S. Rajaraman G. Nagendra Babu S. J. Chavan K. K. Achar P. V. Ramesh Babu 《Journal of the Geological Society of India》2013,82(1):53-58
A medium tonnage unconformity proximal uranium deposit has been established at Chitrial by the Atomic Minerals Directorate in the Srisailam sub-basin. In this type of deposits, the association of uranium with potassic alteration (illitization) is well-documented. The present study is directed towards understanding such an association in the Chitrial area for which the uranium mineralized borehole core samples were collected and analyzed. It is observed that the average concentrations of K2O, Na2O, Rb, Ba and Sr in the granite of the Chitrial area are 5.35%, 1.78%, 252 ppm, 564 ppm and 52 ppm, respectively, and they show average critical elemental ratios of K/Rb, Ba/Rb and Rb/Sr as 191, 2.37 and 7.13, respectively. The granites show low K/Rb, low Rb/Ba and high Rb/Sr ratios compared to that of the average crust indicating its derivation from crustal source. The samples have higher values of uranium (av. 53 ppm), thorium (av. 66 ppm) and lead (av. 41 ppm). The U/Th ratio in the granite varies from 0.07 to 20.86 with an average of 1.68. They also exhibit high K2O/Na2O ratio typical of post-Archaean granite and very high values suggest the possibility of later potassium enrichment. 相似文献
12.
V. Divakara Rao B.L. Narayana P. Rama Rao N.N. Murthy M.V. Subba Rao J. Mallikharjuna Rao G.L.N. Reddy 《Gondwana Research》2000,3(2)
The Early Proterozoic Bijli rhyolites (2180 ± 25 Ma) constitute an important part of the Nandgaon group in the Central Indian craton, a tectonically active block sandwiched between the Dharwar craton in the south and the Bundelkhand craton in the north. The rhyolites are chemically heterogeneous. They have high SiO2 (74.4%), K2O (4.41%), Ba (834 ppm), and low MgO (0.22%), CaO (1.0%), iron (2.8%) V, Cr and Ni (5, 6 and 1 ppm respectively). They contain moderate Sr (88 ppm), Rb (140 ppm), Th (27 ppm) and U (6 ppm). Total REE ranges from 223 ppm to 453 ppm with high LREE (ΣLREE = 307) and all the rhyolites have low to high negative europium anomalies (Eu/Eu* 0.03 to 0.77). The overall chemical signatures support a crustal anatectic origin for the rhyolites from a source of intermediate composition. Basalt pooling below the crust and associated rifting most likely initiated anatexis. 相似文献
13.
In this paper, we report new whole-rock geochemical and zircon U–Pb data for monzogranites in the NE Xing’an block. These data constrained the petrogenesis of C type (high Sr/Y) adakitic rocks and showed the spatial extent of the influence of the Mongol-Okhostsk ocean tectonic regime and the collision between the Jiamusi Massif and Songliao Terrane. New zircon laser-ablation inductivity coupled plasma mass spectrometry (LA-ICP-MS) U–Pb data indicated that the monzogranites in the studied area were emplaced in the Early Jurassic (~180 Ma). These rocks were characterized by unusally high SiO2 (≥67.49), and Sr (461–759 ppm), but strikingly low Y (4.63–8.06 ppm) and HREE (∑HREE = 3.83–6.49 ppm, Yb = 0.5–0.77 ppm) contents, with therefore high Sr/Y (67.2–119) and (La/Yb)N (29.7–41.5) ratios, showing the geochemical characteristics of C type adakitic granite. The data displayed negligible Eu anomalies (Eu/Eu* = 0.77–1.08), LREE-enriched and pronounced negative Nb and Ta anomalies. The C-type adakites in the studied area were most likely derived from the partial melting of a thickened lower continental curst. The magma source is most likely dominated by amphibolites and garnet amphibolites. In combination with previously-reported data from igneous rocks from the Mesozoic in NE China, we conclude that the Xing’an block was influenced by the Mongol-Okhotsk subduction tectonic system, and experiences compressive settings from the amalgamation of the Jiamusi block in the east of the CAOB. 相似文献
14.
FAN Honghai CHEN Jinyong WANG Shengyun ZHAO Jingyang GU Dazhao MENG Yanning 《《地质学报》英文版》2017,91(6):2126-2137
This paper presents a systematic study of major and trace elements and Sm-Nd isotopes in leucogranites closely related to uranium mineralization in the Gaudeanmus area, Namibia. The results illustrate that the uraniferous leucogranites possess high Si_O_2(68.8 wt%–76.0 wt%, average 73.1 wt%) and K(4.05 wt%–7.78 wt%, average 5.94 wt%) contents, and are sub-alkaline and metaluminous to weakly peraluminous, as reflected by A/CNK values of 0.96–1.07 with an average of 1.01. The leucogranites are rich in light rare earth elements(LREE/HREE = 2.53–7.71;(La/Yb)N = 2.14–10.40), have moderate Eu depletion and high Rb/Sr ratios(2.03–5.50 with an average of 4.36); meanwhile, they are enriched in Rb, K, Th, U and Pb, and depleted in Ba, Nb, Ta, and Sr. The ε_(Nd)(t) values of uraninites range from -14.8 to -16.5, and the two-stage Nd model ages are 2.43–2.56 Ga. Detailed elemental and Sm-Nd isotopic geochemical characteristics suggest that the leucogranites were formed in a postorogenic extensional environment. The U-rich pre-Damara basement was the main source of uranium during the primary mineralization event, which is disseminated in leucogranites, whereas the uranium mineralization in veins possibly resulted from remobilization of the primary uranium minerals. 相似文献
15.
湖南秀才洞铀矿位于诸广山北部的鹿井矿田,极具找矿潜力。为进一步查明秀才洞铀矿成矿条件,揭示岩浆岩与成矿作用关系及成矿成岩机制,本文开展了典型矿床地质特征研究,并对矿区典型岩浆岩进行了主量元素、微量元素地球化学分析。结果表明：矿区岩体属酸性岩,具富Si低Ca偏碱特征;微量元素地球化学显示花岗岩富集Nb、U、Th和Ta等高场强元素,贫Sr、Ba、V、Cr、Co、Ni等元素,具典型A型花岗岩特征。岩浆岩及矿石稀土配分曲线均为“平展型”,具强Eu负异常特征,岩浆岩及矿石具有一定的同源性,可以为同一成矿系统。矿体均产于围岩与花岗岩接触带附近,并受断裂构造控制,岩浆岩和地层均提供了一定的铀源。结合矿床特征、成矿地质特征及与岩体的空间关系认为秀才洞铀矿是花岗岩外接触带型铀矿。 相似文献
16.
本文从化探角度出发,讨论了鑀在岩、矿石和土壤中的分市特征及其与铀成矿作用之间的关系。以鑀和铀、镭之间,其衰变成因联系和不同的地球化学性质为基础,对锾法在寻找铀矿中的应用进行了初步探讨。通过在湘西,湘南四种不同类型的20个铀矿床(点)上的大量综合对比,证明了它不仅对铀、镭放射性平衡破坏研究有其独特之处,并且可以推测出成矿过程中的地球化学变化,从而解释铀矿床的成因,评价异常点、带,因此是铀矿普查勘探攻深找盲的一种有效手段。它具有野外工作方法简便、显示直观、影响因素少和便于综合对比等优点。由于氧化还原反应广泛参加了铀矿床的形成和破坏,所以在其它方法(如伽玛、铀量、氡及其子体测量)反映不明显的情况下,鑀法仍有较好的显示。 相似文献
17.
Ajay Kumar S. N. S. Birua Dheeraj Pande A. R. Nath P. V. Ramesh Babu S. A. Pandit 《Journal of the Geological Society of India》2009,73(4):537-542
Several radioactive quartz-pebble conglomerate (QPC) occurrences at the western margin of Archaean Bonai granite and overlying
Iron Ore Group (IOG) rocks have recently been located over a total strike length of 8–10 km intermittently in a NE-SW to E-W
trend with steep dips due north-west to north in parts of Sundargarh district of Orissa. The QPC samples have analysed up
to 0.039% U3O8 and 0.035% ThO2 with high concentration of Y (74 to 518 ppm), La(<100 to 880 ppm), Cr ( 126 to 633 ppm), Zr (137 to 1250 ppm) and Pb (31
to 581 ppm). Cellulose Nitrate (CN) film studies of few QPC samples indicated adsorbed uranium over goethite and infiltrated
ferruginous material (limonite), secondary uranium as encrustation and fracture filling and discrete sub-rounded grains of
monazite, zircon, allanite and rare xenotime in the matrix of QPC as radioactive phases. Higher content of Th over U, elevated
concentration of Y and La in QPC eliminates the possibility of its low temperature product by epigenetic processes. Poor correlation
of U with elements like Pb, Y, Zr, La and Cr can be explained due to surficial leaching of uranium from QPC after its deposition
as reflected by adsorbed U over iron-oxides and low U/Th ratio in QPC in the area. 相似文献
18.
《International Geology Review》2012,54(3):332-350
Triassic granodiorites in South China (SC) provide an opportunity to examine crust–mantle interactions that may have been caused by a mantle plume. Here we present a combined study of chronological, geochemical, and Sr–Nd–Hf isotopic compositions for Dashenshan granodiorites. These are high-K, calc-alkaline, I-type granodiorites that yield a U–Pb zircon age of 211 ± 3 Ma. They are metaluminous to weakly peraluminous (A/CNK < 1.1), with 3.04–3.89 wt.% Na2O and 3.24–3.86 wt.% K2O, and Na2O/K2O ratio ranging from 0.79 to 1.11. These granodiorites contain 67.7–72.6 wt.% SiO2 but show moderate Mg# values (44.2–57.8) and variable contents of Ni (3.6–29.9 ppm) and Cr (7.6–53.5 ppm). They exhibit light rare earth element (REE) enrichment and flat, heavy REE patterns with negative Eu anomalies (Eu/Eu* = 0.52–0.87). They also display strongly negative Ba, Sr, Nb, Ta, P, and Ti anomalies and positive Rb, Th, K, and Pb anomalies. Dashenshan granodiorites have high whole-rock initial 87Sr/86Sr ratios (0.7121–0.7172), negative εNd (t) values (–8.8 to –6.8), and negative zircon εHf (t) values (–6.6 to –3.3). These results suggest that the Dashenshan granodiorites were generated by a mixing between crustal melt and mantle-derived magma in an extensional setting. We conclude that generation of the Dashenshan pluton may reflect an interaction between a mantle plume and the overlying SC crust. 相似文献
19.
S.J. Hoffman 《Journal of Geochemical Exploration》1983,19(1-3)
The Hornby Bay sandstone basin of the Northwest Territories represents one of three areas in Canada in which the geological environment is favourable for the occurrence of unconformity-type uranium deposits. The project area lies within the zone of continuous permafrost and is associated with relatively thin and locally derived tills and abundant outcrops. Topographic relief is normally in the order of 100 m but may locally exceed 300 m/km in more rugged areas.Geochemical case histories for soil and lake-sediment surveys illustrate: identification of regional anomaly, anomaly follow-up, and detailed investigations. Success in locating uranium occurrences using geochemical surveys is high. Orientation studies trace anomalous dispersion trains 10 to 200 m downslope of recognized sources. Anomaly generation is favoured by active hydromorphic processes in geochemically homogeneous overburden containing an average background of 0.5 ppm uranium (using a 4N nitric acid leach). Anomaly contrasts are typically 2 Xto 3 X this value, and anomalous values exceeding 1.5 ppm uranium are highly reproducible.Copper and radium anomalies act as pathfinders for uranium. Lead is present in anomalous concentrations in specimens from the uranium occurrences but lead enrichment in overburden is not sufficiently great to permit its use as a pathfinder element. Preliminary work based on radon and 210Po has not led to identification of anomalies other than those recognized by more routine geochemical surveys.Association of geochemical anomalies with faults within the sandstone basin constitutes one of four conditions elevating an area to drill target status. Methods for drill testing of geochemical soil anomalies depend on the relationship between the geochemical anomaly and an identifiable fault zone. 相似文献
20.
《International Geology Review》2012,54(14):1786-1800
Geochronology, geochemistry, and whole-rock Sr–Nd–Pb isotopes were studied on a suite of Mesozoic adamellites from eastern China to characterize their ages and petrogenesis. Sensitive high-resolution ion microprobe U–Pb zircon analyses were done, yielding consistent ages of 123.2 ± 1.8 to 122.1 ± 2.1 Ma for the samples. These rocks belong to the alkaline magma series in terms of K2O + Na2O contents (8.45–9.58 wt.%) and to the shoshonitic series based on their high K2O contents (5.23–5.79 wt.%). The adamellites are further characterized by high light rare earth element contents [(La/Yb)N = 14.96–45.99]; negative Eu anomalies (δEu = 0.46–0.75); positive anomalies in Rb, Th, Pb, and U; and negative anomalies in Sr, Ba, and high field-strength elements (i.e. Nb, Ta, P, and Ti). In addition, all of the adamellites in this study display relatively low radiogenic Sr [(87Sr/86Sr)i = 0.7081–0.7089] and negative ?Nd(t) values from –16.70 to –17.80. These results suggest that the adamellites were derived from low-degree partial melting of an enriched lithospheric mantle below the North China Craton (NCC). The parent magmas likely experienced fractional crystallization of potassium feldspar, plagioclase and Fe–Ti oxides (e.g. rutile, ilmenite, and titanite), apatite, and zircon during the ascent of alkaline rocks without crustal contamination. 相似文献