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In this work, we prepared three CaWO4 single crystals (CaW‐0, CaW‐1 and CaW‐3) doped with rare earth elements (REEs) at nominal mass fractions of 50, 250 and 5000 μg g‐1 using the Czochralski method. Electron probe microanalysis (EPMA) and laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) were employed to evaluate the within‐ and between‐unit homogeneity of major elements and REEs, respectively. The within‐unit variation (sr) of 0.40–0.84% and between‐unit sr of 0.14–1.48% for major elements were obtained. Within‐ and between‐unit sr of 0.53–5.56% were also found for REEs by LA‐ICP‐MS spot analyses. A comparison of the sr of repeat analyses was compared with the analytical uncertainty (u), i.e., the mean square weighted deviation (MSWD), which is close to or slightly higher than 1, indicating that no obvious chemical heterogeneity was found in these crystals. Reference values for these elements were obtained through various analytical methods across four different laboratories and applications of the reference materials to calibrating REE mass fractions in a natural scheelite were performed. No significant difference of the results was found as t values are less than 2.75 at the 99% confidence interval. The excellent linearity (R2 > 0.98) between the REE mass fractions and both LA‐ICP‐MS signal intensity and wafer absorbance was found, but the crater height and the absolute mass transported into ICP‐MS decreased when REE mass fractions as well as the colour of crystals increased. These results suggest that the reference materials have the potential to calibrate REE mass fractions in natural scheelite. [ABSTRACT FROM AUTHOR]

The Lunpola oil shale is the largest oil shale resource in Tibet. Twenty-four samples were collected from this deposition to determine the platinum group element (PGE) characteristics. The total PGE contents in terrestrial oil shale are low (average 2.386 ng/g). The PGEs are enriched in the oil shale samples near the boundary between the oil shale and its underlying strata. The PGE enrichment may be the result of a change of oxic–anoxic conditions. The individual PGEs of oil shale samples from the Lunpola oil shale exhibit similar modes of occurrence, and their distributions are controlled mainly by Fe-bearing minerals (pyrite). The source of PGEs in the Lunpola oil shale is probably related to water chemistry and terrigenous supply. [ABSTRACT FROM PUBLISHER]

The Bilong Co oil shale, located in the South Qiangtang depression, northern Tibet Plateau, may record the Early Jurassic anoxic event in the eastern Tethys. New geochemical data from the Bilong Co oil shale section are presented in order to determine the mechanism of organic accumulation and to evaluate Early Jurassic anoxia in the eastern Tethys. In organic-rich oil shales, many redox proxies including the relationship of Mo to total organic carbon (TOC), Re/Mo ratios, and pyrite framboid size distribution suggest deposition under euxinic conditions. However, the correlation between TOC and P and Mo contents indicates that organic matter accumulation was controlled mainly by primary productivity. The Sr/Al ratios and clastic influx proxies such as Si, Ti, Th, Zr, and Al concentrations suggest a continuous supply of fresh water from a nearby continent during oil shale deposition. This supply could have initiated stratification of the water so that the upper zone became favourable for marine life. Increased primary productivity could have led to formation of anoxic/sulphidic bottom waters, which enhanced the preservation of organic matter. Deposition of organic-rich oil shales terminated when primary productivity decreased, leading to more oxic bottom water conditions. [ABSTRACT FROM PUBLISHER]

The parameter of tensile strength for transformer bushing insulating paper occupies an important position in the structural design and life evaluation of transformer bushing. In order to precisely achieve the effect of aging time and moisture content on the tensile strength of transformer bushing paper, transformer insulating paper samples with a thickness of 0.13 mm were prepared for tensile strength and dielectric strength testing under different moisture contents and aging states. The results show that the tensile strength (MPa) of insulating paper decreases linearly in the range of 0–648 h under accelerated thermal aging at 130 °C. However, there is a more serious exponential decline in the tensile strength (MPa) of insulation paper with its moisture content is boosted. The moisture content in insulation paper is the most important factor for insulation paper deterioration in oil-impregnated paper insulation equipment, which could accelerate the end of insulation service life. The value of capacitance increment ΔC of the insulation paper samples displayed closely linear growth with a moisture content from 0.5% to 5.9%. Strictly controlling the moisture content by monitoring the ΔC value of transformer insulation paper is of significance for prolonging its service life. [ABSTRACT FROM AUTHOR]

The Lesser Himalayan Belt in the northern margin of Indian Shield preserves abundant sedimentary and magmatic records related to the assembly and breakup of the Columbia supercontinent. However, the Palaeoproterozoic tectonic history of the northern margin of the Indian Shield and its position in the Columbia supercontinent are still controversial. Based on detailed geological investigations in the Dailekh area of western Nepal, we conducted zircon U–Pb dating and Lu–Hf isotopic analysis for meta‐granitoids that intruded into the Lesser Himalayan Crystalline and Metasediments. The Dungeshworl granitic augen gneiss, meta‐monzogranite, and tonalitic gneiss yielded crystallization ages of 1,829 ± 12 Ma, 1,856 ± 11 Ma, and 1,852 ± 11 Ma respectively, which demonstrate that the deposition limits of both the Lesser Himalayan Crystalline and Metasediments are the Palaeoproterozoic. Zircon εHf(t) values of these meta‐granitoids range from −3.99 to +0.18, with corresponding depleted mantle two‐stage model (TDM2) ages of 2.41–2.62 Ga, indicating that they formed by reworking of Neoarchean to Palaeoproterozoic crust. Synthesizing existing geochronological, petrochemical, and zircon Lu–Hf isotopic data for metamorphic sedimentary and igneous rocks from the entire Lesser Himalayan Belt, we suggest that the Palaeoproterozoic magmatism in the northern margin of Indian Shield may be formed within subduction‐related tectonics responded to the assembly of Columbia supercontinent. [ABSTRACT FROM AUTHOR]

The Qiangtang Basin is the biggest petroleum-bearing basin in the Qinghai-Tibet Plateau. This basin experienced a foreland basin evolution during the Early- Middle Triassic and a rift basin evolution during the Late Triassic-Early Cretaceous. Triassic and Jurassic hydrocarbon source rocks were widely distributed throughout the basin. The Triassic Tumen Gela Formation coal-bearing mudstones represent the best source rocks because of high total organic carbon (TOC) content (1.25–3.45%) and HI values (2.8–123 mg/g Toc), and the Xiali Formation mudstones are moderately-good source rocks with an average TOC content ranging from 0.55 to 7.30% and HI values ranging from 7.0 to 165 mg/g Toc. The Jurassic Buqu Formation and Suowa Formation carbonates, however, exhibit poor-to fair-quality as hydrocarbon source rocks. Excellent dolomite and paleokarst reservoirs and mudstones and bearing-evaporite marl cap rocks, together with well-developed structural traps are recognized in the basin. Additionally, a large paleo-oil-reservoir zone has also been discovered. Based on an integrated petroleum systems analysis, nine favorable hydrocarbon exploration areas are proposed, of which the Tuonamu area and Badaohu area are selected as the potential targets for the exploration for oil and gas resources in the basin. Good reservoir quality dolomites in the Buqu Formation are considered to have a significant exploration potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • Zircon U-Pb age for newly discovered K-bentonite (ca. 1.6 Ga) constrained the deposition time of the Lakharpata Group. • The Lakharpata Group in Nepal Lesser Himalaya is coeval sediment with the Lower Vindhyan in India. • The Lakharpata Group was deposited in a passive continental margin basin during the Columbia breakup. The Lakharpata Group, a set of marine sediments with a thickness of over 5000 m, occupies the middle part of the Lesser Himalayan sequence and records important tectono-sedimentary evolution in the northern margin of the Indian continent. However, the duration of deposition and tectonic background of the Lakharpata Group are poorly defined. This study presents zircon U-Pb ages and Hf isotopes, as well as petrochemical data for the newly discovered K-bentonite layers in the Aru Formation, the upper part of the Lakharpata Group. Integrating the detrital zircon ages of the underlying metasedimentary rocks and the sedimentation rate of dolomite in the South China Block, we suggest that the Lakharpata Group was deposited during the late Paleoproterozoic to early Mesoproterozoic (ca. 1680–1580 Ma) rather than from Mesoproterozoic to Early Paleozoic as previously presumed. Stratigraphic correlations show the Lakharpata Group in Nepal Lesser Himalaya correlates to the Lower Vindhyan Supergroup, as well as to the Deoban and Rautgara formations in Kumaun Lesser Himalaya and the Baxa Group in Sikkim Lesser Himalaya, India. The Lakharpata Group comprises two depositional sub-sequences that record two transgression-regression sedimentary processes, which are comparable to the Lower Vindhyan. Geochemical and sedimentological studies suggest that the Lakharpata Group may represent the deposition of a passive continental margin basin during the breakup of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

Two hundred km of 2D seismic survey was carried out at the Lesser Himalayan Thrust Belts in Dailekh district, western Nepal. The main motivation is to elucidate the geologic relationship between the known oil and gas seeps, subsurface structure, and stratigraphy in the area. This is a challenging task which is from its extreme structural and geological complexity such as thrust faulting, tight folding, steep dip layers, and strong lateral variations in seismic velocity. Seismic data were acquired with SERCEL 428XL system and processed by GEOEAST computer software. In order to increase signal-to-noise ratio (SNR), suppress interference, and search for optimum acquisition parameters, a series of comparative tests on the different charge depth and size, group interval, CDP fold, geophone array, and single high-sensitivity geophone were conducted. We also tested 2S3L (two lines shooting and three lines receiving) wide line profiling. The results indicate that single hole with charge depth of 12 m, 4-16 kg charge size (less charge size for the densely populated areas), single high-sensitivity geophone, and 1S2L wide line profiling with 132 folds are the optimum acquisition parameters. On the basis of comparative process experiment, data processing workflow consisting of data preparation, prestack denoising, amplitude compensation, deconvolution, tomography static correction, velocity analysis, residual static correction, CRS stack, poststack migration, prestack time migration (PSTM), and prestack depth migration (PSDM) was selected. Maybe affected by problem of conflicting dip in complex media, CRS stack section does not show satisfactory geological characteristics. PSTM profile has moderate signal-to-noise (S/N) ratio; the shallow, medium, and deep continuous reflections can be observed in section. More details of the geological structures can be observed in PSDM section, especially in medium and shallow layers (less than 3000 ms or 4000 m), but PSDM method is more expensive and highly time consuming than that of CRS stack and PSTM. So, the PSTM section can be reasonably used for geological interpretation. By reference to field mapping, thrust characteristics, and MT data, the final interpretation to the PSTM section identified the interfaces of 6 geological units (Paleoproterozoic Nabhisthan Fm., Paleoproterozoic Dubidanda Fm., Neogene to Late Cretaceous Surkhet group, Late Carboneferous to Early Cretaeous Gondwana group, Mesoproterozoic Upper Lakharpata group, and Lower Lakharpata group) and delineated Main Boundary Thrust (MBT), Ramgarh Thrust (RMT), Padukasthan Thrust (PT), and Dailekh Thrust (DT). The bottom of Surkhet group which is our top target zone is about 4250 meters deep. [ABSTRACT FROM AUTHOR]

With the aim of better understanding geochemistry of trace elements in marine oil shale and its combustion residues, 23 raw samples, 17 oil shale combustion residues, and 18 selected minerals from Bilong Co oil shale are studied. Potentially hazardous trace elements in raw samples include As, B, Cd, Mo, and Se, while Se, Mo, Cd, As, Bi, and U are potentially hazardous trace elements in combustion residues. As is controlled mainly by Fe-bearing minerals. B occurs mainly in clay minerals. Cd is enriched mainly in calcite. Mo is controlled mainly by organic matter. Se is mainly controlled by P-bearing minerals. [ABSTRACT FROM PUBLISHER]

The Qiangtang Basin is a significant prospective area for hydrocarbon and gas hydrate resources in the Tibetan Plateau, China. However, relatively little work has been performed to characterise heat flow in this basin, which has restricted petroleum and gas hydrate exploration. In this study, we compare present and palaeo-heat flow in the Qiangtang Basin to provide information on geothermal regime, hydrocarbon generation and permafrost that is necessary for further petroleum and gas hydrate exploration. We base our study on temperature data from a thermometer well, thermal conductivity tests, vitrinite reflectance data, homogenisation temperature data from fluid inclusions, stratigraphic information and a time-independent modelling approach. Our results indicate that in the central Qiangtang Basin, the present thermal gradient is approximately 15.5 °C/km, and heat flow is approximately 46.69 mW/m 2 . Heat flow in the Qiangtang Basin is not relatively stable since the Early Jurassic, as previous research has suggested, and it is generally decreasing with time. Additionally, there is a clear difference between the hottest thermal regime of the southern and northern Qiangtang Depressions during Cretaceous to Pleistocene time. In the southern Qiangtang Depression, the palaeogeothermal gradient is approximately 32.0 °C/km, and palaeo-heat flow is approximately 70 mW/m 2 . However, in the northern Qiangtang Depression, the palaeogeothermal gradient exceeds 81.8 °C/km, and palaeo-heat flow is greater than 172.09 mW/m 2 . The high thermal regime in the northern Qiangtang Depression is driven mainly by hydrothermal convection. Gas reservoirs are possible targets for hydrocarbon exploration in this depression. Currently, the northwestern part of the northern Qiangtang Depression is the most favourable area for gas hydrate exploration in the Qiangtang Basin. [ABSTRACT FROM AUTHOR]

Abstract: The Tumen coal mine has the largest coal resources in Tibet, which have been developed and utilized as an important energy source in the last decades. It has raised some health problems during the coal exploration and utilization in Tibet. Fifty Late Triassic coal (or coaly) samples were picked up from the Qiangtang Basin (Tumen mine, Woruoshan and Hongshuihe areas) to determine the minerals, potentially hazardous elements and their mode of occurrence and possible sources. Coal samples from the Qiangtang Basin have medium- and high-ash yields (15.20–47.88%) with low or medium-high total sulfur content (0.04–4.86%). Minerals in Qiangtang Basin coal include clay minerals, dolomite, quartz, pyrite, siderite, and hematite, and trace amounts of halite, feldspar, anhydrite, barite, chromite, and galena. Potentially hazardous trace elements in coal samples include As, Hg, Pb, and Se. Arsenic is controlled mainly by aluminosilicate minerals. Mercury occurs mainly as an organic-bound form. The organically bound Pb is dominant. Selenium is controlled mainly by Fe-bearing (probably pyrite). A proportion of the elevated concentrations of As, Hg, Pb and Se in Qiangtang Basin coal may be related to underlying shale bed. These elements might have been eroded or leached from the shale bed, which were subsequently transported and accumulated syngenetically in the coal-forming peat swamps. The enrichment of As, Hg, Pb, and Se in Qiangtang Basin coal, however, is also partly to be related to magmatic/hydrothermal fluids. [Copyright &y& Elsevier]

Highlights: [•] Qiangtang Basin is the biggest residual petroleum-bearing basin in Tibet Plateau. [•] The Late Triassic Tumen Gela Formation is the most important gas source rock. [•] Seventy-one potential anticline structural traps have been found. [•] A favorable geothermal condition for gas hydrate formation. [•] A large number of mud volcanoes were discovered in the basin. [ABSTRACT FROM AUTHOR]

Abstract: The Lunpola oil shale is the largest oil shale resource in Tibet. Twenty-four samples of oil shale, mudstone, and dolomite were collected from the Lunpola oil shale for mineralogical and trace element analyses. The vertical distribution and mode of occurrence of trace elements in this terrestrial oil shale were also discussed. Oil shale samples from the Lunpola area have high TOC contents (5.1–10.6%), high ash yields (74.8–84.7%), low total sulfur contents (0.19–1.03%), and high shale oil contents (5.0–10.3%). The major minerals in the oil shale samples are clays, quartz, calcite and dolomite, with minor quantities of feldspar, siderite, hematite, magnesite and pyrite. Other minerals such as halite, zeolite, barite, anhydrite, and mirabilite were detected in some oil shale samples. The contents of As, Ba, Be, Bi, Cd, Ce, Cs, Hg, La, Li, Mo, Nd, Pb, Pr, Rb, Se, Sm, Th, U, W, and Zr are enriched from 1.30 to 125 times as compared to their average crust abundance (Clarke values), whereas the other elements are slightly higher or lower than their respective Clarke values. Compared to common Australian oil shale, the Lunpola oil shales contain higher As, Ba, Be, Ce, Co, Cs, Ga, Gd, Hf, Nb, Nd, Pb, Pr, Rb, Sc, Sm, Sn, Th, and Zr, but lower Cd, Cu, Lu, Mo, Ni, Se, Sr, U, V, and Zn. Elements associated with organic matter and/or Fe-sulfides are highly enriched in all oil shale deposits, suggesting that their speciation in oil shale is governed by general processes (e.g., high organic matter content and anoxic environment), whereas elements associated with clay minerals exhibit various enrichments indicating that their speciation in oil shale is governed by individual geochemical mechanisms (e.g., source rocks). The elements in the Lunpola oil shale may be classified into three groups of associations according to their modes of occurrence. Group A elements (TiO2, Sc, Hf, Zr, Be, Li, W, V, Zn, SiO2, Al2O3, Rb, Ga, Sn, Cr, Ta, Cs, K2O, Th, Na2O, REEs, and ash yield) have high positive correlations with ash yield and a mainly inorganic affinity. Group B elements (As, TOC, MnO, Ni, Fe2O3, Cd, Co, Cu, Mo, Se, MgO, Bi, Pb, and Hg) show a negative correlation with ash yield, and most elements possibly have a likely organic affinity and/or Fe-sulfide affinity. Group C elements (Sr, CaO, U, and P2O5) show a weak or negligible correlation with ash yield (with the exception of CaO). Elements of environmental concern (As, Bi, Hg, Mo, Pb, Se, and U) are present in high contents, and are clustered in the second association, i.e. they are hosted mainly in Fe-sulfides and/or organic matter. [Copyright &y& Elsevier]

Abstract: The Shengli River–Changshe Mountain oil shale zone, located in the North Qiangtang depression, northern Tibet plateau, represents a potentially largest marine oil shale resource in China. Eighteen samples, including oil shale and micritic limestone, were collected from the Changshe Mountain oil shale to determine the concentrations, the modes of occurrence, and origins of platinum group elements (PGEs) in marine oil shale. The oil shale samples from the Changshe Mountain area exhibit low total PGE contents ranging from 3.196 to 8.071ng/g with a weighted mean value of 5.383ng/g, while the micritic limestone samples from the Changshe Mountain area exhibit a little lower ranging from 0.471 to 5.669ng/g. PGEs in oil shale samples are characterized by high contents in Pd (3.23ng/g), Pt (1.60ng/g), and Os (0.32ng/g), as compared to Rh (0.083ng/g), Ru (0.112ng/g), and Ir (0.043ng/g). The individual PGEs of oil shale samples from the Changshe Mountain area exhibit various modes of occurrence. Ru and Ir are mainly controlled by clay minerals and partly present as sulfide. Rh is mainly associated with sulfide and possibly present as clay minerals. Pt is associated with clay minerals and sulfide, and Pd is controlled by organic matter and pyrite, while Os is mainly present in organic matter. Three possible sources of PGEs were identified in oil shale seams in the Changshe Mountain area. Ru and Ir are mainly terrigenous inputs. Rh and Pt are derived from mixed sources (seawater and terrigemnous supply), while Pd and Os are mainly derived from seawater. The terrestrial source of the oil shale seams in the Changshe Mountain oil shale was the Suowa Formation limestone and the Nadi Kangri felsic volcanic rocks. [Copyright &y& Elsevier]

Abstract: The Bilong Co oil shale zone is located in the South Qiangtang depression. This zone, together with the Shengli River-Changshe Mountain oil shale zone in the North Qiangtang depression, northern Tibet plateau, represents a potentially large marine oil shale resource in China. With the aim of better understanding geochemistry of marine oil shale, 18 samples from the Bilong Co area are studied and 56 elements in them are determined. The contents of Mo, Se, Cd, Cs, As, Bi, U Rb, Pb, Th, Li, Sr, and Zn are enriched from 1.3 to 35.0 times as compared with the average concentration in the crust (Clarke values), whereas the other elements are slightly higher/lower than the respective Clarke values. Compared to common Australian oil shales, the contents of Ce, Co, Cs, F, Ga, Hf, Nb, Nd, Pb, Pr, Rb, Sc, Sn, Th, and Zr in the Bilong Co oil shale samples exhibit relatively high levels, whereas As, Br, Cd, Cr, Cu, Dy, Er, Eu, Ho, Lu, Mo, Ni, Se, Tb, Tm, U, V, Y, Yb, and Zn are relatively depleted. However, the distribution patterns of trace elements are quite similar indicating that trace-element speciation in oil shale is governed by general processes rather than by individual geochemical mechanisms within one particular sample. The elements in the Bilong Co oil shale may be classified into three groups of association according to their modes of occurrence, i.e. Groups A, B, and C. Group A (Si–Al–K–Na–Ti–Zr–Sc–Th–Sn–Nb–Ga–Ta–Be–Hf–Cs–Li–Rb–ash–REEs) is strongly correlated with ash yield and mainly has an inorganic affinity. Group B (Cr–W–Mg–Mn–Br–F–Sr–Ba) has weakly or negatively positive correlation coefficients (with an exception of F) with ash yield. Group C (Zn–Bi–Cd–Ca–Fe–Pb–Hg–Co–Cu–Ni–P–Mo–Se–U–As–V) shows negative correlation coefficients with ash yield (with an exception of Bi) and possibly has an organic affinity. [Copyright &y& Elsevier]

Abstract: The Shengli River–Changshe Mountain oil shale zone, located in the North Qiangtang depression, northern Tibet plateau, represents a potentially large marine oil shale resource in China. Twenty-one samples including oil shale, micritic limestone and marl were collected from the Shengli River area to determine the contents, distribution patterns and modes of occurrence of platinum group elements (PGEs) in marine oil shale. Oil shale samples from the Shengli River area have high ash yield (61.86–67.48%) and total organic carbon content (8.02–13.67%) with low total sulfur content (0.76–1.39%) and intermediate shale oil content (3.60–16.30%). The total PGE content in oil shale samples is very low (average 1.749ng/g), approximately half the mean value of Chinese coals, but higher than that of USA coals. PGEs in oil shale samples from the Shengli River area are characterized by high Pd (average 0.82ng/g), Os (average 0.15ng/g) and Pt (average 0.66ng/g) contents compared with Ru (average 0.05ng/g), Rh (average 0.05ng/g) and Ir (average 0.02ng/g). Distribution patterns of individual PGEs are not uniform in the Shengli River oil shale section. The lower marl layer is characterized by the highest Ru and Rh concentrations, whereas the upper marl layer is characterized by the highest Os and Ir concentrations. The highest Pt and Pd concentrations are found in the lower and upper parts of oil shale seams, respectively. The individual PGEs in the oil shale samples from the Shengli River area exhibit various modes of occurrence. Ru is mainly present in P-bearing minerals and partly associated with the clay and Ca-bearing minerals. Rh is mainly controlled by clay minerals and partly present in the form of apatite. Os occurs mainly in clay minerals and, to a lesser extent, in pyrite and apatite. Pd and Ir are mainly associated with Ca-bearing minerals and apatite. Pt is mainly present in Ca-bearing minerals and partly related to organic matter and apatite. [Copyright &y& Elsevier]

Abstract: The Shengli River–Changshe Mountain oil shale zone, located in the North Qiangtang depression, northern Tibet plateau, represents a potentially large marine oil shale resource in China. The contents and distribution patterns of rare earth elements (REEs) in selected oil shale and micritic limestone samples from the Changshe Mountain area were studied by inductively-coupled plasma mass spectrometer (ICP-MS). Analyzed oil shale samples from the Changshe Mountain area are characterized by high total organic carbon (TOC) contents (7.02–16.32%) and ash yields (53.22–82.12%) with shale oil contents from 3.85% to 11.76%. The total rare earth element (∑REE) contents in oil shale samples are 68.19μg/g, close to those of US coals, and higher than those of micritic limestone samples (37.69μg/g) from the Changshe Mountain area, but lower than those of world-wide black shales, common Chinese coals, and North American Shale Composite. There are two types, A and B, of distribution patterns of REEs in the Changshe Mountain oil shale samples. Type A shows negligible Ce anomalies (0.97–1.01), with slightly higher ∑REE concentrations (36.87–118.38μg/g) and LREE/HREE (6.79–10.74) and (La/Yb) n (6.68–8.36) ratios, whereas type B exhibits a slightly negative Ce anomaly (0.84–0.88), with slightly lower ∑REE concentrations (13.73–15.31μg/g) and LREE/HREE (5.54–6.34) and (La/Yb) n (5.03–6.65) ratios. Both types A and B oil shales are characterized by distinctly sloping LREE trends (La n /Sm n =3.60–5.44) accompanied by flat HREE trends, with distinct Eu negative anomalies (0.51–0.69). The vertical variations of ∑REE contents are similar to those of ash, Si, Al, K, Na, Ti and Fe, and show a negative correlation with organic sulfur and organic carbon, indicating that the REE contents in oil shale seams are mainly controlled by land-derived detritus. [Copyright &y& Elsevier]