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Research article Journal of the Geological Society Published online August 10, 2017 https://doi.org/10.1144/jgs2017-032 | Vol. 175 | 2018 | pp. 146–162

Geochemistry of loess deposits in northeastern China: constraint on provenance and implication for disappearance of the large Songliao palaeolake

Yuanyun Xie1*, Fang Yuan1, Tao Zhan2, Chunguo Kang3, Yunping Chi1 & Yongfa Ma2 1 College of Geographic Science, Normal University, Harbin 150025, China 2 The Second Hydrogeology and Engineering Geology Prospecting Institute of Province, Harbin 150030, China 3 Geography Department, Harbin Institute, Harbin 150086, China * Correspondence: [email protected]

Abstract: The Harbin loess, typical of the loess in NE China, is located in the easternmost margin of the Eurasian loess belt, and was recently investigated from the perspective of an Asian aeolian dust system. Before this study, the geochemical composition and provenance of the Harbin loess remained poorly understood. More importantly, the study of the Harbin loess also provides a unique opportunity to understand the geomorphological evolution process of the large Songliao palaeolake in the Northeast Plain. This study presents the results on the geochemical characteristics (major elements, trace elements, rare earth elements and Sr–Nd isotope) of the Harbin loess. There are markedly consistent geochemical compositions in and between the loess and palaeosol sediments, revealing stable dust sources and identical sources for the loess and palaeosol. Various indicators illustrating weathering and recycling indicate that the Harbin loess–palaeosol sediments were derived from sources with a low degree of weathering and from material with first-cycle alluvial–lacustrine deposits. Combinations of various provenance tracing indicators indicate that the Harbin loess has a strong geochemical affinity with the Songnen Sandy Land and to a certain extent the Horqin Sandy Land but not with the Hulun Buir Sandy Land, which indicates that these loess deposits are derived from a mixed provenance, with the dominant source being the neighbouring Songnen Sandy Land and a second, distal source being the Horqin Sandy Land. Finally, we advocate that the Harbin loess accumulation could serve as the direct record of the Songliao palaeolake disappearance. Supplementary material: Data for the NE Sandy Lands of China, and full provenance discrimination diagrams are available at https://doi.org/10.6084/m9.figshare.c.3835009. Received 6 March 2017; revised 17 June 2017; accepted 20 June 2017

Aeolian-derived Chinese loess deposits, one of the best terrestrial convincingly determine the time at which the large Songliao equivalents of the marine oxygen isotope records (Catt 1991; Pye palaeolake disappeared holds the key to better understanding the 1995; Kemp 2001; Sheldon & Tabor 2009), are an important nature of geomorphological–tectonic–climatic linkage in this region. archive of the geological past and provide the most valuable The NE loess is located at the easternmost edge of the mid- continental monsoonal climate records of global change (Kukla latitude giant desert or sandland in the Asian interior, and also is at 1987; Ding et al. 1994; An 2000; Porter 2001). The Chinese aeolian the eastern boundary of desertification in northern China. It is loess deposits accumulate dominantly on the Chinese Loess commonly suggested, based on comparison of the geochemical Plateau, which is situated downwind of and adjacent to the Gobi compositions of loess with those of materials in the potential source (stony desert) and desert–sandland in northwestern China, and have areas, that the loess of the Chinese Loess Plateau is mainly derived been well studied. Aeolian deposits are also scattered widely outside from the adjacent upwind desert areas with a short distance of the Chinese Loess Plateau, such as the northeast loess in China transportation (e.g. Li et al. 2009, 2011; Chen & Li 2011). It is (hereinafter referred to as ‘NE loess’). In comparison with the therefore reasonable to speculate that these NE loess deposits detailed and systematic studies on the loess of the Chinese Loess originate from the NE Sandy Land of China (e.g. Xie et al. 2014, Plateau, the NE loess deposits have received far less attention. Until 2015; Xie & Chi 2016), including the Horqin Sandy Land, the recently, a limited number of studies on the NE loess deposits have Hulun Buir Sandy Land, the Songnen Sandy Land and, to a certain concentrated on palaeomagnetic stratigraphy (e.g. Zeng et al. 2011, extent, the Onqin Daga Sandy Land (see Fig. 1 for locations). These 2016; Yi et al. 2012, 2015), but their geochemical characteristics sandlands, relatively small areas for each, are geographically and dust sources are still poorly understood. isolated from each other; therefore it is likely that aeolian dust is The NE–SW-extending Songliao Plain, also known as the less affected by other sand lands during its deflation and transport to Northeast (NE) Plain, is located in the central part of NE China and form loess deposits. Thus, the NE loess is supposed to well record it is bounded by the Da Hinggan Mountains to the west, the Changbai source information, which provides a valuable opportunity to better Mountains to the east and the Lesser Khingan Mountains to the north understand the close relationship between loess deposits and the (see Fig. 1 for locations). Therewas a high-level lake in Songliao Plain evolution of the large Songliao palaeolake. in the Early and Middle Pleistocene (Qiu et al. 1983, 1988, 2012; Qiu However, we have only limited knowledge on the geochemistry 2008), which is referred to as the large Songliao palaeolake. The of the NE loess, which restricts our understanding of the relationship disappearance of this palaeolake in the NE Plain has long been an between loess deposition and the geomorphological–tectonic issue of considerable contention (Qiu et al. 1983, 1988 , 2012; Yang evolution process in the past. Here, we fill in this critical gap in et al. 1983; Qiu 2008), and the time of its disappearance is not known this study and present results from a comparatively poorly owing to the lack of available method to determine it. How to investigated region outside the Chinese Loess Plateau. The

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Geochemistry of Harbin loess deposits 147

Fig. 1. (a) Sketch map of East Asia, showing the deserts and sandy land in northern China suggested to be main sources of Asian dust; (b) sketch map of the Northeast Plain in China (after Xie & Chi 2016), showing location of the study area and sampling sites; (c) landform sketch of Harbin area; (D) sketch map of stratigraphic section.

Harbin loess, a well-known northeastern loess, is selected for northeastern China. The Huangshan section is located on the second geochemistry analysis. This study aims to (1) cast light on the terrace of the , c. 35 km east from Harbin city, at an geochemical composition of these northeastern loess deposits, with altitude of 180 m above sea-level. The Huangshan section is a type the particular purpose of constraining their source weathering, section of the Huangshan Formation of the middle Pleistocene. The sedimentary recycling and provenance, and (2) give a convincing section is c. 70 m thick and is composed of four lithological units, scheme to determine a potential time of disappearance for the large which are, from the lowest upward, the Baitushan, lower Huangshan, Songliao palaeolake, as a contribution to tracing Asian aeolian dust upper Huangshan and Harbin Formations. The Baitushan Formation from source to sink and to clarifying the geomorphological (c. 4 m exposed thickness) is dominated by grey–green to yellowish- evolution process in the Northeast Plain. green mucky mild clay with the characteristic of compactness and stickiness, which represents lacustrine deposits. The lower Huangshan Formation (c. 21 m thick) is characterized by sediment- Materials and methods ary features such as horizontal bedding and well-marked iron stain, – – Sediments and sample collection and consists of brown yellow, grey yellow, yellow mild clay, clayey silt, fine- to medium-grained sand, and medium- to coarse-grained The Harbin loess is located at the Huangshan (called Tianhengshan sand, with increasing grain size toward the lower part. Thus the now) (see Fig. 1), Tuanjie town, Harbin, Heilongjiang Province, sedimentary environment of the lower Huangshan Formation as a Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

148 Y. Xie et al. whole was lacustrine. The upper Huangshan Formation (c.20m Reference Materials (GSS1–4, Geochemical Standard Reference thick) is marked by horizontal bedding, brown–yellow to grey– Sample Soils, Ministry of Land and Resources of the People’s yellow mild clay, with grain-size coarsening downward, showing a Republic of China) for rock were used for external calibration. transformation of the sub-clay through yellow–brown clayey silt to Analytical uncertainties (relative standard deviation) were less than rust–yellow medium- to fine-grained sand, which represents 2%, suggesting a high degree of reliability of the measurements. lacustrine deposits. The Harbin Formation, about 25 m thick, is a The sample preparation procedure followed the methods proposed light grey–yellow aeolian loess deposit comparable with the Malan by Yang et al. (2007a,b). loess in the Chinese Loess Plateau, with four interbeds of palaeosol. Calcite was selectively dissolved with purified acetic acid Fifteen loess and five palaeosol samples from the Harbin solution (0.5 mol l−1) at room temperature for up to 8 h and only Formation were collected for analyses of major and trace elements the acid-insoluble residues (i.e. silicate fractions) were investigated (including rare earth elements; REE) as well as Sr and Nd isotopic for Sr–Nd isotopic ratios, which were determined by thermal composition. To constrain the provenance of the Harbin loess ionization mass spectrometry (TIMS) following the method of Chen deposits, 46 representative surface sediment samples from the et al. (2007) at the Analytical Laboratory of Beijing Research Northeast Sandy Land, as a potential dust source of the Harbin loess, Institute of Uranium Geology. Sr and Nd isotope ratios were were also collected for the same analyses as the Harbin samples. Of normalized to 86Sr/88Sr = 0.1194 and 146Nd/144Nd = 0.7219, these 46 samples, 13 are from the Hulun Buir Sandy Land, 13 from respectively. The analytical blanks are insignificant: <1 ng for Sr the eastern edge of the Horqin Sandy Land, and 20 from the Songnen and <50 pg for Nd, respectively. Reproducibility and accuracy were Sandy Land adjacent to the centre of the large Songliao palaeolake. checked by running the Sr standard NBS987 and Nd standard JMC, with a mean 87Sr/86Sr value of 0.710250 ± 7 (2σ) and a mean 143 144 σ Analytical methods Nd/ Nd value of 0.512109 ± 3 (2 ), respectively. Only the <63 μm fractions of all the samples studied here were used because most of the particles forming the Harbin loess have grain Results μ sizes less than 63 m (unpublished data). Such a selection is Major element compositions designed to eliminate the influence of mineral sorting during aeolian transportation and deposition, and to allow geochemical compari- The major element compositions for the Harbin loess are shown in son between the loess deposits and their potential dust sources in the Table 1. A plot of the major elements, normalized to Upper same grain-size ranges. The <63 μm fractions were extracted by dry Continental Crust (UCC, Taylor & McLennan 1985) and post- sieving. Archaean Australian average shale (PAAS, Taylor & McLennan Major elements were analysed by standard X-ray fluorescence 1985), is given in Figure 2. (XRF) spectrometry (AL104, PW2404) on fused glass beads at the Samples for both the Harbin loess and palaeosol have rather Analytical Laboratory of Beijing Research Institute of Uranium uniform major element compositions, with the exception of Mn Geology. The detection limit is c. 0.01 wt% and analytical precision (Table 1 and Fig. 2), the content of which clearly varies from sample (relative standard deviation) is <1% for major elements. Loss on to sample. LOI, reflecting amounts of variable carbonates, clay ignition (LOI) was obtained by weighing before and after 1 h of minerals and organic matter in most samples, has moderate values heating at 950°C. Trace elements, including REE, were determined with a mean value of 4.92% and 6.06% for loess and palaeosol, by inductively coupled plasma mass spectrometry (ICP-MS, respectively. These values are comparable with those of the Finnigan MAT, Element I), also at the Analytical Laboratory of Luochuan loess in the central Chinese Loess Plateau (4.43 – Beijing Research Institute of Uranium Geology. Four Standard 6.72%; Chen et al. 2001). SiO2 for both the Harbin loess and

Table 1. Concentrations (wt%) of major elements for the Harbin loess–palaeosol sediments

Sample SiO2 Al2O3 TFe2O3 MgO CaO Na2OK2O MnO TiO2 P2O5 FeO LOI Loess HS-9 67.71 13.90 4.21 1.34 1.46 2.55 2.99 0.09 0.77 0.11 0.90 4.72 HS-10 67.26 14.05 4.38 1.38 1.45 2.46 2.97 0.06 0.76 0.11 1.02 5.04 HS-11 67.67 14.04 4.27 1.33 1.43 2.48 2.96 0.07 0.75 0.11 0.63 4.82 HS-12 67.32 13.96 4.30 1.35 1.48 2.54 3.02 0.08 0.77 0.11 1.11 4.87 HS-13 67.95 14.00 4.13 1.33 1.44 2.51 3.02 0.06 0.75 0.10 0.91 4.63 HS-14 67.75 14.04 4.17 1.35 1.43 2.45 2.94 0.07 0.75 0.11 1.04 4.93 HS-18 67.8 13.89 4.01 1.30 1.48 2.57 3.07 0.06 0.75 0.09 1.10 4.85 HS-88 67.24 14.01 4.32 1.19 1.57 2.44 2.92 0.07 0.77 0.11 0.65 5.18 HS-89 67.55 13.9 4.17 1.13 1.56 2.43 2.89 0.06 0.77 0.10 0.93 5.37 HS-120 68.74 13.96 4.07 1.15 1.55 2.46 2.86 0.04 0.71 0.12 0.70 4.30 HS-131 67.65 14.12 4.19 1.15 1.6 2.51 2.99 0.05 0.75 0.11 0.75 4.82 HS-180 66.94 14.33 4.46 1.26 1.51 2.31 2.93 0.07 0.78 0.12 0.68 5.28 HS-181 66.99 14.34 4.45 1.27 1.53 2.39 3.01 0.05 0.79 0.11 0.53 4.88 HS-198 67.32 14.22 4.37 1.28 1.57 2.41 2.95 0.05 0.79 0.10 0.95 4.92 HS-199 66.88 14.35 4.47 1.31 1.55 2.36 2.93 0.04 0.78 0.09 0.52 5.15 Palaeosol HS-45 65.96 14.06 4.38 1.17 1.52 2.11 2.68 0.07 0.77 0.14 0.75 6.78 HS-49 66.57 14.10 4.48 1.18 1.52 2.23 2.83 0.07 0.78 0.12 0.65 6.01 HS-111 66.58 14.13 4.60 1.11 1.54 2.23 2.84 0.04 0.76 0.13 0.88 6.01 HS-112 66.89 13.96 4.58 1.12 1.57 2.31 2.91 0.04 0.77 0.13 0.56 5.59 HS-154 67.04 14.04 4.32 1.13 1.54 2.18 2.86 0.05 0.76 0.09 0.86 5.93

Major elements without recalculation on a volatile-free basis. TFe2O3, total iron. Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

Geochemistry of Harbin loess deposits 149

Fig. 2. PAAS-normalized patterns for major and trace elements of the Harbin loess–palaeosol sediments, in comparison with the potential sources. PAAS values are from Taylor & McLennan (1985). palaeosol samples is similar to UCC and PAAS. Both the loess and or slightly lower than those of PAAS (Fig. 2). Y shows slight to palaeosol samples are slightly to moderately depleted in Al2O3, moderate enrichment relative to UCC but is slightly depleted to Fe2O3 and K2O with respect to UCC and PAAS, and moderately slightly enriched for loess and slightly enriched for palaeosol depleted in MgO relative to UCC and PAAS. P2O5 for both the loess relative to PAAS. Zr for the Harbin loess and palaeosol samples is and palaeosol is slightly to moderately depleted compared with comparable with or slightly higher than that for UCC but slightly PAAS but strongly depleted compared with UCC. CaO for all depleted to slightly enriched in the loess in comparison with PAAS aeolian samples is strongly depleted in relation to UCC but slightly and comparable with PAAS in the palaeosol. Hf and Th for the enriched compared with PAAS. Na2O is moderately depleted with Harbin loess samples are slightly depleted to slightly enriched in respect to UCC but moderately to strongly enriched with respect to comparison with UCC, but in the palaeosol are comparable with or PAAS. TiO2 is moderately enriched relative to UCC but slightly slightly higher than PAAS. U is moderately depleted in the Harbin to moderately depleted relative to PAAS. MnO is moderately to loess and palaeosol samples compared with UCC and PAAS. strongly depleted compared with PAAS but intensely varies from moderate enrichment to moderate depletion compared with UCC. Transition trace elements (TTE): Sc, V, Cr, Co, Ni, Cu, Zn, Ga Trace elements The Harbin loess and palaeosol samples are, to a different extent, The trace element results for the Harbin loess samples are listed in depleted in TTE, and are notably depleted especially in V, Cr, Co, Table 2, and those for potential dust sources (i.e. the Northeast Sandy Vi and Cu (Fig. 2). In comparison with UCC, however, Sc, Ni, Cu, Land) are given in the supplementary material for comparison. The Zn and Ga are similar in the Harbin loess and palaeosol. Cr shows normalized trace element patterns of the studied loess deposits with strong enrichment in both the loess and palaeosol when compared respect to PAAS are shown in a spider diagram in Figure 2, where with UCC. V is slightly to moderately enriched in the loess but elements are arranged in order of decreasing compatibility in a moderately enriched in the palaeosol with respect to UCC. Co typical igneous differentiation series (Ghosh & Sarkar 2010; shows comparability or slight depletion in the palaeosol but notable Akarish & EI-Gohary 2011). The most compatible elements are variations in the loess in comparison with UCC. shown to the left, with the incompatible elements towards the right along the x-axis. Analogous to the major element distribution, the Large ion lithophile elements (LILE): Rb, Sr, Cs, Ba, Pb Harbin loess and palaeosol samples show significantly similar trace element patterns normalized to UCC and PAAS (see Fig. 2). Compared with PAAS, the Harbin loess and palaeosol samples show strong enrichment in Cs and moderate enrichment in Rb (Fig. 2). Sr is comparable with or slightly higher than PAAS in the High field strength elements (HFSE): Y, Zr, Nb, Hf, Ta, loess but comparable with or slightly lower than PAAS in the Th, U palaeosol. In comparison with PAAS, Ba shows similarity or slight The Harbin loess samples are moderately to noticeably depleted in depletion in the loess but slight depletion in the palaeosol. The loess Nb and Ta with respect to UCC but their values are comparable with and palaeosol samples show similarity or slight enrichment in Pb 150 − Table 2. Concentrations (μgg 1) of trace elements for the Harbin loess and palaeosols

Element Loess Palaeosol UCC PAAS Downloaded from

HS-9 HS-10 HS-11 HS-12 HS-13 HS-14 HS-18 HS-88 HS-89 HS-120 HS-131 HS-180 HS-181 HS-198 HS-199 HS-45 HS-49 HS-111 HS-112 HS-154 Sc 10.7 10.9 11.7 10.8 11.9 10.5 11.4 10.7 11.1 10.9 11.8 12.6 12.7 11.5 12.9 12.2 11.9 11.4 11.8 11.8 11 16 V 66.5 70 78 67.5 74.4 66.5 80.9 65.3 68.2 72.9 76.9 84.1 79.7 76 84.8 83.5 82.8 96.4 98 81.1 60 150 Cr 51.6 58 60 54.6 63.1 58.4 62.8 59.9 56.8 62 59.2 62.7 59.3 62.8 69.7 67.9 65.8 62.8 61.8 69.8 35 110 Co 9.0 9.4 10.1 10.0 10.1 9.6 11.6 10.3 9.9 7.8 9.5 12.9 9.4 9.4 8.9 9.7 9.9 8.6 9.5 10.2 10 23

Ni 22 22.2 22.1 22 22.3 21.1 23 21.6 20 24.8 22 24.1 22.6 21.8 23.8 22.6 21.3 22.1 21.7 24.6 20 55 http://jgs.lyellcollection.org/ Cu 26.6 28.2 24.8 26.9 24.4 25 25.4 23.4 27.4 23.8 24 23.9 23.7 25.6 26.5 23.6 23.4 25.6 21.5 25 25 50 Zn 68.3 72.9 68.4 71 66 66 65 72.7 72 67.5 66.9 72.5 71.3 67.5 72 67.5 68.2 65.4 65.8 67 71 85 Ga 16.9 17.3 17.5 16.8 17.4 16.5 18.7 16.6 17.8 18.1 17.7 18.6 18.5 17.9 19 17.4 17.6 16.6 17.7 17.5 17 20 Rb 104 108 113 108 114 105 118 104 101 102 115 117 117 109 120 112 117 110 114 114 112 160 Sr 215 215 211 215 215 206 228 199 207 235 240 218 222 212 226 178 183 196 208 205 350 200 Y 23.1 24.3 28.8 24.6 28 25.8 29.7 23.7 27.7 24.9 28.8 28.7 28.6 28.4 30.4 30 29.2 30.4 29.6 27.6 22 27 Nb 16.2 16.9 16.1 16.7 16.2 15.1 16.9 16.2 17.2 16.1 17 16.9 18.1 17.1 17.9 17.3 17 15.4 16.6 16 25 19 Cs 6.8 7.2 7.1 6.9 7.0 6.6 7.3 6.7 6.9 6.4 7.1 7.4 7.5 7.1 7.8 7.5 7.5 6.8 7.0 7.2 3.7 – Ba 609 597 619 604 617 593 667 587 598 608 646 632 634 600 633 625 613 584 607 606 550 650 Ta 1.3 1.4 1.4 1.3 1.3 1.2 1.5 1.2 1.4 1.3 1.3 1.4 1.4 1.3 1.4 1.3 1.4 1.2 1.2 1.4 2.2 1.3

Pb 22.3 21.9 20.7 22.1 21.4 21.3 23 20.4 22.6 22.8 20.7 23.4 22.4 21.4 22.7 22.5 22.3 23.3 25.1 21.6 20 20 byguestonJanuary11,2018 .Xie Y. Th 11.8 10.6 11.2 11.1 11.4 10.6 12 10.2 12.3 10.7 11.3 12.7 12.5 11.1 12.5 13.3 12.6 12.1 12.6 11 10.7 14.6 U 2.2 2.1 2.0 2.0 2.1 2.2 2.1 2.1 2.8 2.2 2.1 2.1 2.0 2.1 2.1 2.0 1.9 2.0 2.1 1.8 2.8 3.1

Zr 208 227 214 227 226 242 233 242 236 238 206 198 182 194 223 215 208 213 218 194 190 210 al. et Hf 6.3 6.8 6.2 6.8 6.4 7.0 6.3 7.1 7.0 7.2 5.9 5.6 5.3 5.7 6.4 6.3 6.2 6.0 5.9 5.5 5.8 5.0 La 37.2 34.9 37 36.3 36.6 32.9 37.3 32.7 38.2 33.0 37.1 38.8 39.7 35.7 37.1 38.2 37.2 36.2 35.8 34.0 30.0 38.2 Ce 71.2 64.9 66.4 66.1 67.2 60.9 68.8 64.9 73.9 60.1 69.4 75 74.8 67.5 70.0 63.9 68.3 66.7 69.4 63.2 64.0 79.6 Pr 8.7 8.2 8.6 8.4 8.4 7.9 8.6 7.9 9.1 7.9 8.5 8.9 9.0 8.2 8.5 8.7 8.6 8.4 8.3 7.8 7.1 8.8 Nd 33.8 31.9 32.8 32.8 32.6 30.8 33.7 30.2 35.3 30.5 32.7 34.4 34.6 32.0 32.5 34.0 33.1 32.0 32.0 29.7 26.0 33.9 Sm 6.35 6.16 6.11 6.46 6.02 6.05 6.23 5.78 6.79 6.06 5.99 6.44 6.22 5.91 6.08 6.13 6.15 5.88 5.76 5.45 4.5 5.55 Eu 1.27 1.22 1.24 1.24 1.22 1.18 1.28 1.17 1.3 1.21 1.27 1.27 1.25 1.21 1.3 1.3 1.24 1.3 1.24 1.18 0.88 1.08 Gd 5.01 4.91 5.57 5.09 5.6 4.91 5.58 4.65 5.61 4.89 5.74 5.95 5.85 5.27 5.55 5.75 5.85 5.87 5.23 5.25 3.8 4.66 Tb 0.888 0.867 1.06 0.896 0.972 0.9 1.02 0.893 1.01 0.883 0.984 1.05 1.01 0.979 1.02 0.985 1.09 1.02 1.03 0.944 0.64 0.77 Dy 4.79 4.71 4.8 4.73 4.86 4.88 5.02 4.73 5.06 4.76 4.76 5.12 4.59 4.59 5.2 5.03 4.83 5.08 4.99 4.61 3.5 4.68 Ho 0.855 0.9 1.04 0.877 1.01 0.922 1.06 0.898 0.977 0.9 1.01 1.04 0.971 0.954 1.08 1.06 1.06 1.05 0.993 0.95 0.8 0.99 Er 2.53 2.69 2.77 2.6 2.54 2.78 3.02 2.71 2.96 2.61 2.71 2.97 2.67 2.59 3.02 2.89 2.97 3.08 2.86 2.66 2.3 2.85 Tm 0.402 0.417 0.503 0.421 0.493 0.427 0.474 0.426 0.472 0.443 0.469 0.508 0.467 0.479 0.514 0.494 0.461 0.497 0.471 0.419 0.33 0.41 Yb 2.65 2.72 3.27 2.67 3.22 2.91 3.53 2.67 3.02 2.89 3.37 3.48 3.24 3.08 3.8 3.35 3.68 3.53 3.33 3.01 2.2 2.82 Lu 0.404 0.402 0.491 0.41 0.429 0.438 0.468 0.414 0.475 0.418 0.47 0.503 0.445 0.437 0.512 0.474 0.475 0.503 0.487 0.462 0.32 0.43 Th/Sc 1.10 0.97 0.96 1.03 0.96 1.01 1.05 0.95 1.11 0.98 0.96 1.01 0.98 0.97 0.97 1.09 1.06 1.06 1.07 0.93 0.97 0.91 La/Sc 3.48 3.20 3.16 3.36 3.08 3.13 3.27 3.06 3.44 3.03 3.14 3.08 3.13 3.10 2.88 3.13 3.13 3.18 3.03 2.88 2.73 2.39 La/Co 4.14 3.72 3.66 3.65 3.62 3.41 3.22 3.17 3.88 4.25 3.91 3.01 4.21 3.79 4.17 3.93 3.75 4.22 3.76 3.33 3.00 1.66 Th/Co 1.31 1.13 1.11 1.12 1.13 1.10 1.03 0.99 1.25 1.38 1.19 0.98 1.33 1.18 1.41 1.37 1.27 1.41 1.32 1.08 1.07 0.63 Cr/Th 4.37 5.47 5.36 4.92 5.54 5.51 5.23 5.87 4.62 5.79 5.24 4.94 4.74 5.66 5.58 5.11 5.22 5.19 4.90 6.35 3.27 7.53 La/Th 3.15 3.29 3.30 3.27 3.21 3.10 3.11 3.21 3.11 3.08 3.28 3.06 3.18 3.22 2.97 2.87 2.95 2.99 2.84 3.09 2.80 2.62 ∑REE 176.09 164.85 171.65 168.98 171.13 157.87 176.11 160.03 184.18 156.54 174.49 185.41 184.81 168.90 176.22 172.30 175.05 171.07 171.88 159.66 146.37 184.77 9.05 8.36 7.80 8.55 7.95 7.69 7.73 8.20 8.40 7.80 7.94 7.99 8.60 8.19 7.51 7.60 7.57 7.29 7.86 7.72 9.54 9.49 Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

Geochemistry of Harbin loess deposits 151

. when compared with PAAS. In comparison with UCC, however, Sr is strongly depleted and Cs is strongly enriched in the loess and palaeosol samples. REE = LREE + ∑ Rare earth elements The results of REE analyses are listed in Table 2 and shown as

Taylor & McLennan (1985) chondrite-normalized patterns in Figure 3, together with those of PAAS, UCC and potential source samples from the Northeast Sandy Land for comparison. The results for the Northeast Sandy Land potential source to the Harbin aeolian deposits are given in the supplementary material for comparison. The Harbin samples exhibit similar REE patterns, characterized by enriched light REE (LREE) and relatively flat heavy REE (HREE) profiles, and consistent pronounced negative Eu anomalies (Fig. 3). These REE

REE is total content of rare earth elements ( patterns, especially those for LREE, show a roughly similar shape to

∑ those for the UCC and/or the PAAS. Some differences, however, occur between the Harbin samples and UCC and/or PAAS. Some of the studied samples show pronounced negative Ho and Er anomalies and pronounced positive Tm and Yb anomalies (see Fig. 3). The total REE (∑REE) values of the Harbin Loess and palaeosol vary from 156.54 to 185.41 μgg−1 and from 159.66 to 175.05 μgg−1, respectively, with average values of 171.82 μgg−1 and 169.99 μgg−1, respectively (Table 2). The REE concentrations of the Harbin loess and palaeosol samples are fairly uniform, and are calculations were chondrite-normalized. UCC and PAAS values are after ∑ μ −1 N comparable with the REE values of 146.37 gg and 184.77 μgg−1 for UCC and PAAS, respectively. The average ∑LREE and ∑HREE values of the Harbin loess are 152.95 and 18.87 μgg−1, and those of the palaeosol are 150.24 μgg−1and and (Gd/Yb) −1 N 19.76 μgg , respectively. The mean ∑LREE/∑HREE and LaN/ YbN ratio is 8.11 and 7.90 for the Harbin loess, and 7.60 and 7.25 for the palaeosol, which suggests markedly fractionated REE , (La/Sm) N patterns. The mean LaN/SmN ratio is 3.70 for the Harbin loess and 3.89 for the palaeosol, denoting distinct fractionation and enrichment in LREE. The mean GdN/YbN ratio is 1.40 and 1.34 for the Harbin loess and palaeosol respectively, indicative of relatively flat HREE patterns with notable HREE depletion. Moderate negative Eu anomalies occur in the Harbin samples, with an average of 0.66 and 0.67 for the loess and palaeosol respectively, close to the typical value of 0.65 for both PAAS and UCC. Ce anomalies are unapparent or absent for the Harbin samples, with average values of 0.91 and 0.89 for the loess and palaeosol respectively.

Sr–Nd isotopic compositions

, missing data in the literature. Ce/Ce*, Eu/Eu*, (La/Yb) The acid-insoluble silicate fraction Sr–Nd isotopic compositions of – . the Harbin samples are given in Table 3. Comparison for Sr–Nd 0.5 ) N isotopic compositions between the Harbin samples and the

×Gd Northeast Sandy Land is shown in Figure 4, together with values N for the loess of the Chinese Loess Plateau (Rao et al. 2008; Li et al. /(Sm

N 2009) and three major potential Asia dust sources (Chen et al. 2007; Li et al. 2009, 2011). The Sr concentration ranges from 199 to 240 μgg−1 (average 217.6 μgg−1) and from 178 to 208 μgg−1 (average 194 μgg−1), , Eu/Eu* = Eu μ −1

0.5 and the Nd concentration varies from 30.2 to 35.3 gg (average ) − − − N 32.7 μgg 1) and from 29.7 to 34 μgg 1 (average 32.2 μgg 1) for

×Pr the Harbin loess and palaeosol samples, respectively. The Harbin N loess and palaeosol samples show notable uniformity in Sr and Nd /(La N concentrations. The 87Sr/86Sr ratios for the Harbin loess samples are

9.493.69 8.671.53 3.57 7.65 1.46 3.81 9.19 1.38 3.54 7.68 1.55 3.83 7.64 1.41 3.42 7.14 1.37 3.77 8.28 1.28 3.560.710655 8.55 1.41 3.54 7.72 1.51 3.43 7.44– 1.370.711362, 3.90 7.53 1.38 3.79 8.28 1.39with 4.02 7.83 1.46 3.80an 6.60 1.39average 3.84 7.71 1.18 3.92 value 6.83 1.39 3.81 6.93of 1.29 3.88 0.711173, 7.26 1.35 3.91 7.63 1.27 3.93 and 9.21 1.41 4.20 9.15 the 1.40 4.33 1.34 87Sr/86Sr ratios for the Harbin palaeosol samples are 0.711325 – N N N 0.711816, with a mean value of 0.711582. The Harbin loess and palaeosol samples have very uniform 143Nd/144Nd ratios and vary HREE Ce/Ce*Eu/Eu*(La/Yb) 0.93 0.69 0.90 0.68 0.87 0.65 0.89 0.66 0.90 0.64 0.89 0.66 0.90 0.66 0.95 0.69 0.93 0.64 0.87 0.68 0.91 0.66 0.95 0.63 0.93 0.63 0.92 0.66 0.92 0.68 0.82 0.67 0.89 0.63 0.90 0.68 0.94 0.69 0.91 0.67 1.03 0.65 1.02 0.65 LREE/ LREE is total content of light rare earth elements (LREE = La + Ce + Pr + Nd + Sm + Eu); HREE is total content of heavy rare earth elements (HREE = Gd + Tb + Dy + Ho + Er + Tm + Yb + Lu); HREE); Ce/Ce* = Ce (La/Sm) (Gd/Yb) within a small range from 0.512122 to 0.512263 (average 0.512182) Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

152 Y. Xie et al.

Fig. 3. Chondrite-normalized REE patterns for the Harbin loess–palaeosol sediments, in comparison with the potential sources. UCC and PAAS patterns are given as a reference. (a, b) Comparison of Harbin loess and palaeosols with UCC and PAAS, respectively; (c) comparison between the Harbin loess and palaeosols and potential source areas. It should be noted that REE pattern for the Harbin loess and palaeosols is located between those for the Songnen Sandy Land and the Horqin Sandy Land. UCC, PAAS and chondrite values are after Taylor & McLennan (1985). and from 0.512116 to 0.512257 (average 0.512178) for the Harbin and the Ordos Desert, lower 87Sr/86Sr values and loess and palaeosol, respectively. The Harbin loess and palaeosol higher 143Nd/144Nd values can be seen in the Harbin samples (see samples have similar εNd(0) values: −10.07 to −7.32 (average Fig. 4), which are close to or comparable with those of the deserts −8.90) for the loess and −10.18 to −7.43 (average −8.97) for around the northern border of China. palaeosol. Accordingly, the Harbin loess and palaeosol samples 87 86 143 144 show fairly good consistency in both the Sr/ Sr and Nd/ Nd Discussion values (see Table 3 and Fig. 4). In comparison with the loess of the Chinese Loess Plateau, the arid lands of the northern margin of the The geochemical characteristics of rocks and sediments are extensively used to constrain the source rock composition and provenance of rocks and sediments (McLennan et al. 1993; Cullers Table 3. Sr and Nd isotopic compositions for the Harbin loess and 1994, 1995; Cox et al. 1995; Asiedu et al. 2000; Gu et al. 2002; Xu palaeosols et al. 2007; Roddaz et al. 2012), especially in the case of Asian aeolian dust (e.g. Ding et al. 2001; Jahn et al. 2001; Chen et al. 87 86 143 144 ε Sample Sr/ Sr Nd/ Nd Nd(0)* 2007; Li et al. 2009; Hao et al. 2010). The geochemical composition Loess of sediments, however, is influenced by many complex factors such HS-11 0.711295 0.512263 −7.32 as source rocks, weathering–sedimentary recycling, grain-size HS-13 0.711207 0.512173 −9.07 sorting during transport and deposition, and post-sedimentary HS-18 0.711094 0.512122 −10.07 alteration (e.g. McLennan et al. 1980, 1983a; Wronkiewicz & HS-131 0.710655 0.512239 −7.78 Condie 1987; Cullers 2000; Lahtinen 2000; Armstrong-Altrin et al. HS-180 0.711312 0.512144 −9.64 2004; Das et al. 2006; Dostal & Keppie 2009; Mazumdar et al. HS-181 0.711362 0.512201 −8.52 2015) and, accordingly, the geochemical composition of sediments HS-198 0.711145 0.512138 −9.75 and that of source rocks does not correlate entirely. Thus special care HS-199 0.711316 0.512172 −9.09 must be taken in relating the geochemical composition of the Palaeosol sediments to that of the source when constraining provenance (e.g. − HS-45 0.711816 0.512141 9.69 McLennan et al. 1983a; Xu et al. 2007; Xie et al. 2014). It is − HS-49 0.711765 0.512136 9.79 therefore necessary to examine the possible influence of these − HS-111 0.711342 0.512116 10.18 factors (especially sedimentary processes) on geochemical compo- HS-112 0.711325 0.512257 −7.43 sitions before drawing conclusions on the provenance of sediments HS-154 0.71166 0.51224 −7.76 by using geochemical characteristics of sediments (e.g. McLennan ε 143 144 143 144 − 143 144 et al. 1983a ; Feng & Kerrich 1990; Hayashi et al. 1997; Xu et al. * Nd(0) = [( Nd/ Nd)sample/( Nd/ Nd)CHUR 1] × 10 000; ( Nd/ Nd)CHUR = 0.512638. 2007; Roddaz et al. 2012). In view of this, we first evaluate the Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

Geochemistry of Harbin loess deposits 153

Fig. 4. Sr–Nd isotopic compositions of the Harbin loess–palaeosol sediments, in comparison with the potential sources of dust in NE China. Also shown are the results of the potential sources of Asian dust and the loess of the Chinese Loess Plateau (CLP) after Chen et al. (2007), Rao et al. (2008) and Li et al. (2009, 2011). NBC, deserts around the northern border of China; NMTP, arid lands of the northern margin of Tibetan Plateau; OD, Ordos Desert (for locations, see Fig. 1). Of special note is that the Sr–Nd isotopic data of Harbin dust deposits plot within the fields of the Songnen Sandy Land and the Horqin Sandy Land but far from those of the Hulun Buir Sandy Land and the Chinese Loess Plateau. influence of weathering and sedimentary recycling on geochemical The CIA values for Harbin samples vary in an extremely narrow compositions, irrespective of grain-size sorting because of the range from 58 to 60 and from 60 to 61 for the loess and palaeosol, comparison of geochemistry compositions based on the same grain respectively. The low CIA values of the Harbin samples suggest size (<63 μm component), and then we discuss the possible sources that these sediments are in the stage of incipient weathering and for the Harbin aeolian loess. have experienced a low degree of weathering, and have geochemistry characteristics similar to their source material. Source weathering and sedimentary recycling Weak chemical weathering is further supported by the weak positive correlation between Al2O3 and TiO2 (r = 0.54). Because Chemical weathering in the source area is likely to modify the Al2O3/TiO2 ratios vary greatly in primitive source rocks, physical chemical composition of rocks or sediments. For instance, chemical sorting without significant chemical weathering would produce 2+ + weathering commonly removes labile cations (e.g. Ca ,Na and sediments with highly variable Al2O3/TiO2 ratios (Young & K+) and retards the loss of stable cations (e.g. Al3+ and Ti4+)from Nesbitt 1998). the residual constituents during the journey from source terrane to The low degree of weathering can also be discerned from the A– depositional site (Fedo et al. 1995). Such a modification depends CN–K diagram constructed for the present study (Fig. 5); the data heavily on the intensity of the weathering process. Therefore, the points for the Harbin samples plot tightly as clusters above and close concentration of particular elements in the sediments is directly to the plagioclase–K-feldspar join (i.e. the feldspar line), which is a affected by variations in concentrations of other elements. The region of less weathering in comparison with PAAS and shows a amount of these elements surviving in sediments is a sensitive slight removal of Ca and Na owing to a low degree of weathering. indicator of the intensity of chemical weathering. The degree of weathering is slightly variable, with palaeosol The degree of source-area weathering can be quantified by samples plotting slightly closer to the CN corner and PAAS. This various indicators. Several indicators of weathering have been demonstrates the progressive enrichment of Al and depletion of Ca proposed based on abundances of mobile and immobile element and Na (owing to plagioclase weathering) with a gradually oxides (e.g. Na2O, CaO, K2O and Al2O3). Among the well-known increasing weathering intensity, whereas the K content (K-feldspar, indicators of weathering, the Chemical Index of Alteration (CIA; micas) remains constant. The combination of low CIA value and Nesbitt & Young 1982) is well constructed as a method of similar degree of weathering of the Harbin loess as the palaeosol quantifying the degree of source weathering. The CIA is defined as indicates that the palaeosol developed in a dry–cold climate that is CIA = [Al2O3/(Al2O3 + CaO* + Na2O+K2O)] × 100, where all apparently unfavourable for the development of the palaeosol. major oxides are expressed as molar proportions (concentrations) The Index of Compositional Variability (ICV) (Cox et al. 1995; and CaO* is the content of CaO incorporated in silicate minerals Cullers & Podkovyrov 2000) is frequently employed to evaluate (i.e. excluding calcite, dolomite and apatite). There is no direct rock or sediment maturity. The ICV is defined as ICV = (CaO + method to distinguish and quantify the contents of CaO belonging K2O+Na2O+Fe2O3 + MgO + TiO2 + MnO)/Al2O3, where total to silicate fractions and non-silicate fractions (carbonates and iron is expressed as Fe2O3 and CaO involves all sources of CaO. apatite). Although Fedo et al. (1995) provided a method to eliminate In this index, the oxides are expressed as weight percentages. Rocks carbonate Ca2+ contained in clastic deposits or sediments, it is or sediments with low ICV values (commonly ICV < 1) are difficult to determine the proportion of calcite and dolomite. generally suggested to be compositionally mature and contain a Therefore, an assumption proposed by some investigators high proportion of clay minerals such as kaolinite, illite and (McLennan 1993; Bock et al. 1998; Roddaz et al. 2006, 2012; muscovite, indicative of recycled sediments in passive margin Xu et al. 2010; Ahmad & Chandra 2013; Liu et al. 2014; Wang settings. On the other hand, those with high ICV values (typically et al. 2014) is adopted. We suppose that CaOR represents the molar ICV > 1) could imply an immature source in active tectonic settings fraction of the remaining CaO after eliminating CaO from apatite; and contain a high proportion of non-clay silicate minerals (i.e. that is, CaOR = mol CaO − (10/3 × mol P2O5). If CaOR ≤ Na2O, rock-forming minerals) such as plagioclase, K-feldspar, amphiboles then the value of CaOR is accepted as CaO*; that is, CaOR = CaO*. and pyroxenes (Cox et al. 1995; Cullers & Podkovyrov 2000). ICV If, however, CaOR >Na2O, then CaO* = Na2O. This method to values for the studied samples vary from 0.97 to 1.05 (average 1) estimate the content of CaO in the silicate fractions has been well and 0.96 to 0.99 (average 0.98) for the loess and palaeosol, used in the reconstruction of source-area weathering (e.g. Tao et al. respectively. This suggests that the loess–palaeosol sediments 2013). studied here are compositionally weakly mature and enriched in Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

154 Y. Xie et al.

∑LREE/∑HREE, ∑REE, Th/Sc, Al/Ti and Al/Nb have been plotted against the CIA (see the supplementary material). As would be expected, a correlation is not apparent between these parameters, with the exception of 87Sr/86Sr and CIA. The positive correlation of 87Sr/86Sr values of the studied samples with the CIA and the lack of a relationship between 143Nd/144Nd value and the CIA collectively suggest that chemical weathering exerts an influence on the 87Sr/86Sr ratio but not on the 143Nd/144Nd isotopic compositions, as concluded by previous researchers (Rao et al. 2006; Hong et al. 2013). However, the ratios involving the immobile elements Al, Ti, Zr, Nb, Th, Sc, Cr, Co, Y, Ni, La and REE, such as Th/Sc, La/Sc, Co/Th, Cr/Th, Al/Ti, Al/Zr, Al/Nb, Y/Ni, Eu/Eu*, ∑LREE/ ∑HREE and ∑REE, show no correlations with the CIA values and Al2O3; this finding indicates that these ratios and the REE (including REE pattern) of the studied samples have not been affected by chemical weathering and are predominantly inherited from the source provenance. These conclusions are corroborated by the uniform geochemical compositions between the Harbin loess and palaeosol (see the Results section). Fig. 5. A–CN–K ternary diagram (in molecular proportions) illustrating Sedimentary sorting and recycling processes are accompanied by weathering trend and primary source rock nature for the Harbin loess– fractionation and enrichment of heavy minerals, notably zircon. palaeosol sediments (after Nesbitt & Young 1982, 1984, 1989; Fedo et al. Zircon is a physically and chemically ultrastable mineral that can 1995). Also plotted are the potential dust sources, PAAS and UCC (after indicate the effect of recycling (McLennan et al. 1993). An example Taylor & McLennan 1985), as well as some rock-forming minerals of this can be illustrated for the Harbin loess–palaeosol sediment. important in silicate rock weathering, together with some igneous rocks The Zr/Sc ratio is plotted against the Th/Sc ratio in Figure 6. The Zr/ representing initial source rocks of weathered sediments, for comparison. Sc ratio is a useful index of zircon enrichment (sediment recycling), CIA values range from 50 for fresh primary igneous rocks to a maximum as Zr is strongly enriched in zircon whereas Sc is not enriched but of 100 for the most weathered rocks (Fedo et al. 1995). The black arrow generally preserves, similarly to REE, a signature of the provenance. represents the weathering trend of the Harbin dust sediments following the However, the Th/Sc ratio is very sensitive to compositional predicted weathering trend. The horizontal dotted lines represent CIA ranges of the Harbin loess–palaeosol sediments. It is of interest to note variations associated with the provenance area, and is a good that the intersection of the weathering trend line of the Harbin loess– palaeosol sediments and the feldspar join is between the fields of granite, felsic volcanic rocks and TTG (tonalite–trondhjemite–granodiorite). The data for felsic volcanic rocks and TTG are after Condie (1993); the data for gabbro, tonalite, granodiorite (Gd) and granite are after Nesbitt & Young (1984, 1989) and Fedo et al. (1995). Calculations of molecular proportions were performed according to the integrating methods of McLennan (1993) and Fedo et al. (1995). both rock-forming minerals and clay minerals, an indication of simple or weakly recycled deposits and/or weak weathering. The SiO2/Al2O3 ratio is sensitive to sediment recycling and weathering processes, and Roser & Korsch (1986) have used it as a signal of sediment maturity, with values increasing as quartz survives preferentially to feldspars, mafic minerals and lithic grains. Average values of <4.0 characterize immature sedimentation, whereas values of >5.0 – 6.0 in sediments are an indication of progressive maturity and values >6.0 indicate mature sediments (Roser et al. 1996). When values exceed 7.0, and peak at >10.0, this suggests strongly mature sediments. SiO /Al O values that range Fig. 6. Th/Sc v. Zr/Sc bivariate plot (after McLennan et al. 1993) for the 2 2 3 Harbin loess–palaeosol sediments identifying whether the sediments are between c. 3.0 and 5.0 characterize immature to weakly mature derived from recycled sedimentation. Linked magmatic rock averages sediments (Roser et al. 1996). SiO2/Al2O3 (wt%) values for the define a model source rock evolution trend line (continuous line) for first- studied samples vary in a very narrow range from 4.7 to 4.9 and cycle magmatogene sediments. Sediments plotting along the from 4.7 to 4.8 for the loess and palaeosol, respectively, higher than differentiation trend of a typical igneous sequence (i.e. compositional the values of 3.3 for PAAS (Taylor & McLennan 1985) and 4.3 for variation trend) indicate compositional variations for Th/Sc and Zr/Sc UCC (Taylor & McLennan 1985), indicating compositionally weak ratios in the igneous source rocks, which are indicative of a minimal maturity. influence of sediment sorting and recycling, and are considered to be first- Although the Harbin loess and palaeosol have undergone a low cycle volcanogenic sediments. However, sediments following the degree of source weathering, it is generally suggested that the sediment recycling trend (arrow) are suggested to be recycled sediments, chemical composition of sediments can be influenced to a certain which show the enrichment of heavy minerals, especially zircon (high Zr/ Sc ratio) owing to sedimentary sorting and recycling. It should be noted extent by chemical weathering, as mentioned above. Also, certain that the deviation of the Harbin loess–palaeosol sediments from this geochemical source tracing indicators are likely to be influenced by igneous differentiation trend is typically characteristic of sedimentary weathering (e.g. Nath et al. 2000). It is therefore necessary to test if recycling; also that the studied data plot near those for felsic volcanic the intensity of weathering of the Harbin loess and palaeosol affects rocks, TTG, PAAS and UCC. UCC and PAAS values are from Taylor & some frequently used geochemical indicators. Some geochemical McLennan (1985). Average compositions of volcanic rocks in the plot are parameters such as 87Sr/86Sr, 143Nd/144Nd, Eu anomalies (Eu/Eu*), after Condie (1993). Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

Geochemistry of Harbin loess deposits 155 overall indicator of igneous chemical differentiation processes Sedimentary recycling is also suggested by Rb/Sr ratios. In most (McLennan et al. 1990). Thus, a plot of Th/Sc v. Zr/Sc can reflect cases, weathering and recycling processes can lead to a significant the degree of sedimentary sorting and recycling (McLennan et al. increase in Rb/Sr ratios, and high Rb/Sr values (>0.5) have been 1993). In first-cycle sediments (or in the absence of recycling), Th/ interpreted as an indicator of strong weathering and sedimentary Sc and Zr/Sc ratios tend to show a similar extent of variation, recycling (McLennan et al. 1993). The Rb/Sr ratios for the studied depending on the source rock composition, whereas in more mature loess–palaeosol samples vary from 0.43 to 0.54 (average 0.51) and or recycled sediments the Zr/Sc ratio varies considerably but the Th/ from 0.55 to 0.64 (average 0.58) for the loess and palaeosol, Sc ratio does not vary significantly (Wronkiewicz & Condie 1987; respectively, between values for UCC (0.32; Taylor & McLennan McLennan et al. 1993; Gu 1994). In the case of the Harbin loess– 1985) and PAAS (0.8; Taylor & McLennan 1985) (see Fig. 7c), and palaeosol sediments, it can be seen in the Zr/Sc v. Th/Sc plot also suggest a weak recycling history. K and Rb are sensitive to (Fig. 6) that these samples do not follow a trend consistent with weathering and sedimentary recycling and have been widely used as igneous differentiation (compositional variations) being controlled indicators for source composition (Floyd & Leveridge 1987; Floyd mainly by magmatic source rocks and instead show distinct et al. 1989; Nath et al. 2000). Our samples have K/Rb ratios of 244– deviation from this trend, showing Zr/Sc increasing substantially 288 (average 269) and 239–258 (average 249) for the loess and but Th/Sc increasing far less, consistent with zircon enrichment palaeosol, respectively (Fig. 7d), between the values of 231 for resulting from sedimentary sorting and recycling. The above PAAS (Taylor & McLennan 1985) and 303 for UCC (Taylor & observations show that the Harbin loess–palaeosol deposits have McLennan 1985). These samples do not occur along the typical been subjected to a weak level of sedimentary sorting and recycling, magmatic differentiation trend (UCC ratio of 300) and instead show mainly because of the low Zr concentration in the loess–palaeosol a slight deviation from this magmatic compositional variation trend samples. In addition, HREE relative to LREE are preferentially along the sedimentary recycling trend (arrow in Fig. 7d) parallel to incorporated into zircon and accumulation of zircon would lead to the UCC–PAAS join. Accordingly, the moderate K/Rb ratio and HREE enrichment and a decrease in LaN/YbN ratio with increasing low Rb concentrations (c. 110), combined with deviation from the Zr contents (e.g. Asiedu et al. 2004). However, the lack of igneous differentiation trend, indicate that these samples show a low systematic correlation of Zr with LaN/YbN ratio again indicates degree of recycling. weak sedimentary recycling because of weak Zr enrichment in the In a supergene environment, the weathering and sedimentary loess–palaeosol deposits. Similarly, weak positive correlations recycling are interrelated. The weathering that has affected the between Zr and SiO2 (r = 0.42) as well as between Al2O3 and TiO2 sediments probably reflects a cumulative effect including several (r = 0.54) also indicate weakly recycled sediment. The characteristic cycles of weathering at the source (Perri et al. 2013; Perri 2014; of simple or weak sedimentary recycling for the Harbin loess– Chen et al. 2016). This includes a first cycle of weathering and palaeosol sediments suggests that these loess sediments are likely to weathering during sedimentary recycling, which indicates that be derived from first-cycle alluvial–lacustrine deposits rather than sedimentary recycling could significantly affect the weathering multi-cycle aeolian deposits (i.e. aeolian sand), because aeolian indices (such as CIA, CIW and PIA, which are used to quantify the sand is commonly believed to be sourced from fluvial deposits and chemical weathering degree of the sediments). However, the to have a more developed recycling history and processes in weathering degree in turn could reflect sedimentary recycling to a comparison with fluvial deposits. certain extent (e.g. Garzanti et al. 2014; Campodonico et al. 2016; Whereas both immobile elements La and Th are enriched in felsic Chen et al. 2016). Despite the lack of a measure for reflecting the sources, La/Th ratios in basic sources are notably higher than in influence of sedimentary recycling on geochemical composition of acidic sources owing to a low content of Th in basic sources the sediments, it has been generally believed that sedimentary (McLennan et al. 1980). Additionally, Hf, like Zr, is enriched in recycling processes have homogenized the geochemical compos- zircon and therefore Hf content increases with the enrichment of ition of sediments (McLennan et al. 1990; Bauluz et al. 2000; Nath zircon owing to sedimentary sorting and recycling. Accordingly, a et al. 2000; Ahmad et al. 2016). However, in spite of this, we would diagram of La/Th against Hf is used to discriminate between still suggest that a poor degree of weathering and recycling is different source compositions of felsic versus mafic components unlikely to notably influence the geochemical composition of the (e.g. Schieber 1992, and references therein) and to indicate Harbin loess deposits, as mentioned above. More importantly, it has sedimentary recycling (Floyd & Leveridge 1987). In the La/Th– recently been proposed that the provenance signals in sediments are Hf diagram constructed for the present study (Fig. 7a) some of the not erased entirely, and can be retrieved, by the use of geochemical studied samples plot along an increasing old sediment component methods, from the immobile elements and their ratios, although a trend, indicating sedimentary recycling. strong degree of chemical weathering processes and sedimentary Sedimentary recycling can also be assessed from Th and U sorting exerts a notable influence on the geochemical composition abundances in sediments (McLennan & Taylor 1980; McLennan of sediments (Schneider et al. 2016). et al. 1993). Sedimentary recycling in oxidizing conditions usually 4+ results in fractionation of Th and U because U is readily oxidized Provenance to U6+ during weathering (McLennan & Taylor 1980). This highly soluble species can be removed from the system, whereas Th In accordance with the comparison of the geochemical composi- remains relatively insoluble (McLennan & Taylor 1980). Hence, if tions of loess with those of sediments in the potential source areas, sedimentary recycling is important in the chemical evolution of the loess of the Chinese Loess Plateau is generally believed to be sediments, it should be accompanied by a steady increase in Th/U dominantly derived from the adjacent upwind deserts and Gobi ratios, as U would be continually lost during successive cycles of desert in northwestern China with a short distance of transportation weathering and redeposition. Th/U ratios >4 are thought to be (e.g. Sun 2002; Chen et al. 2007; Li et al. 2009, 2011; Yang et al. related to weathering and recycling history (McLennan et al. 1993, 2009; Chen & Li 2011). The fingerprint of a neighbouring source 1995; Gu et al. 2002). Th/U ratios of the Harbin loess–palaeosol for aeolian loess makes it reasonable to speculate that the Harbin deposits range from 4.4 to 6.2 (average 5.4) and from 6.0 to 6.7 loess deposits may also have an adjacent derivation from the NE (average 6.3) for the loess and palaeosol, respectively, higher than Sandy Land. However, it remains poorly understood which sandy the average value for UCC (3.8; McLennan & Taylor 1980) and that land is the dominant dust source area for the Harbin loess. for PAAS (4.7; Taylor & McLennan 1985)(Fig. 7b), suggesting According to the above results, although the Harbin loess there has been sedimentary recycling. deposits had experienced a low degree of weathering and a simple Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

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Fig. 7. Plots indicating weathering and sedimentary recycling trend. (a) La/Th–Hf diagram after Floyd & Leveridge (1987), indicating a simple sedimentary recycling as shown by slight enrichment of Hf by sediment recycling and sorting. It should also be noted that the Harbin loess–palaeosol sediments fall within the felsic source field and plot close to the fields of felsic volcanic rocks, TTG, granite, PAAS and UCC. (b) Th/U–Th diagram after McLennan et al. (1993), revealing a weathering and recycling trend from UCC toward PAAS. (c) Rb/Sr–Rb diagram after Xie & Chi (2016), showing a weathering and – recycling trend from UCC to PAAS. (d)K2O Rb diagram after Floyd & Leveridge (1987) and Floyd et al. (1989), revealing a magmatic differentiation trend (corresponding to a K/Rb ratio of 300 for UCC) defined by average volcanic rock composition as well as a weathering and recycling trend from UCC toward PAAS. It should be noted that the Harbin samples show a slight deviation from this magmatic differentiation trend along the sedimentary recycling trend (arrow line), and that the Harbin samples are clustered between the fields of TTG, granite, felsic volcanic rocks, UCC and PAAS. The boundary line between acid–intermediate and basic compositions is after Floyd & Leveridge (1987). UCC and PAAS values are after Taylor & McLennan (1985); average compositions of volcanic rocks in (a) and (d) are after Condie (1993).

sedimentary recycling process, weak or simple weathering and close to that for the Horqin Sandy Land, but far from the field of the recycling do not exert an influence on the ratios of the selected Hulun Buir Sandy Land. This observation is highlighted in immobile element pairs. The information held in these sediments diagrams of the combinations of REE and selected immobile trace thus makes it possible to characterize their provenance. The elements that are the most powerful in source discrimination (see the provenance of sediments can be inferred from the geochemistry of supplementary material). These observations cast new light on selected immobile trace elements, based on the fact that during geochemical affinity of the studied loess–palaeosol sediments with weathering, erosion and transport, certain immobile trace elements the Songnen Sandy Land, and to a certain extent, the Horqin Sandy (such as REE, Th and Sc) remain virtually insoluble and are Land, but not with the Hulun Buir Sandy Land. transferred almost quantitatively into the sedimentary record from The relationships between the loess and palaeosols and the source to sedimentation and, consequently, bear the signature of the potential sources are also seen in ternary diagrams of La–Th–Sc parental rock (McLennan et al. 1983b, 1990; Bhatia 1985; Taylor & (Taylor & McLennan 1985; Bhatia & Crook 1986), Th–Sc–Zr/10 McLennan 1985; Bhatia & Crook 1986; Condie 1991; Armstrong- and Th–Co–Zr/10 (Bhatia & Crook 1986), Ta×10–Cr/10–Nd Altrin et al. 2004; Singh 2009). Additionally, immobile element (Muhs et al. 2008) and 300 × Ti–15 × Al–Zr (Garcia et al. 1994), ratios are more representative than single element concentrations in illustrated in Figure 9. These ternary diagrams have been used discriminating between sources, as they omit the dilution effects of frequently in a variety of provenance identifications (Bhatia & certain minerals owing to sedimentary sorting and allow the Crook 1986; Asiedu et al. 2004; Muhs et al. 2008; Ghosh & Sarkar combination of different trends in REE and trace element patterns 2010; Jorge et al. 2013). The Harbin samples strikingly depart from (Ferrat et al. 2011). Accordingly, the immobile element ratios are those of the Hulun Buir Sandy Land, being located within the field selected to constrain the provenance of the Harbin aeolian loess. of the Songnen Sandy Land and to a certain extent close to the field In Figure 8, which shows binary diagrams involving the ratios of of the Horqin Sandy Land. immobile elements, the studied loess–palaeosol samples fall in the Of special importance is that the evidence from Sr–Nd isotopic field defined by the Songnen Sandy Land, and to a certain extent, compositions further casts light on the provenance of the Harbin Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

Geochemistry of Harbin loess deposits 157

Fig. 8. Provenance discrimination diagrams involving immobile major and trace elements constructed for the Harbin loess–palaeosol sediments. It should be noted that the Harbin dust samples plot within the field of the Songnen Sandy Land and close to that of the Horqin Sandy Land but far from the field of the Hulun Buir Sandy Land, indicative of a geochemical affinity between the Harbin aeolian loess and the former two sandy lands. loess–palaeosol sediments. Sediments from different geological precise information regarding the composition of source areas and bodies have distinct Sr–Nd isotopic compositions dependent on hence are expected to be more useful than the major and trace their origins and ages, and these isotopic ratios remain substantially elements in discriminating the source (Xie et al. 2015). Therefore, unchanged during surficial processes such as weathering, transpor- Sr–Nd isotopic ratios have long been widely used as a powerful tation and deposition (Grousset & Biscaye 2005). More signifi- indicator for deciphering the source areas of Asian aeolian dust (Liu cantly, the Sr–Nd isotopic compositions of sediments provide more et al. 1994; Jahn et al. 2001; Grousset & Biscaye 2005; Chen et al. Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

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Fig. 9. Provenance discrimination ternary diagrams used for the Harbin loess and palaeosols, revealing a striking geochemical resemblance to the Songnen Sandy Land and to a certain extent the Horqin Sandy Land. (a)La–Th–Sc ternary plot (Taylor & McLennan 1985; Bhatia & Crook 1986); (b)Th–Sc–Zr/ 10 ternary plot and (c)Th–Co–Zr/10 ternary plot (Bhatia & Crook 1986); (d)Ta×10–Cr/10–Nd ternary plot (Muhs et al. 2008); (e) 300 × Ti–15 × Al–Zr ternary plot (Garcia et al. 1994). Xifeng loess is after Hao et al. (2010).

2007; Li et al. 2009, 2011; Yang et al. 2009). The Sr–Nd isotopic Harbin dust source areas are mainly the surrounding sandy lands, compositions for the Harbin loess and palaeosols fall near the including the Songnen and the Horqin Sandy Land to the SW, and boundary of the field for the deserts around the northern border of the Hulun Buir Sandy Land to the NW. The dust sourced from the China (see Fig. 4), and are located in the field of the Songnen Sandy Hulun Buir Sandy Land cannot be transported over long distance to Land and the Horqin Sandy Land but further away from those of the the central NE Plain owing to the impediment of the Da Hinggan Hulun Buir Sandy Land, the Chinese Loess Plateau, the northern Mountains, as indicated by the fact that the loess originating from margin of the Tibetan Plateau and the Ordos Desert. Several lines of Hulun Buir Sandy Land is present to the west of the Da Hinggan findings can be seen from these Sr–Nd isotopic data (Fig. 4): (1) the Mountains but not to the east (Qiu 2008). Moreover, source–sink Harbin loess–palaeosol sediments have a significantly different comparison studies of geochemical composition, as performed derivation from the loess of the Chinese Loess Plateau; (2) the above, clearly do not support the Hulun Buir Sandy Land as a northern margin of the Tibetan Plateau and the Ordos Desert are source of the Harbin loess deposits. unlikely to be the provenances for the Harbin loess–palaeosol Based on the geochemical affinities of the Harbin loess and sediments; (3) the studied loess–palaeosol sediments are derived palaeosols with the Songnen Sandy Land and, to a certain extent, the from the Songnen Sandy Land and/or the Horqin Sandy Land; Horqin Sandy Land, we advocate that dust forming the Harbin loess (4) the Hulun Buir Sandy Land can be excluded as a source of the was chiefly derived from the Songnen Sandy Land, with a non- Harbin dust sediments. Identical findings are also revealed in negligible dust contribution from the Horqin Sandy Land (see the diagrams integrating Nd isotopic composition with Th/Sc ratio and supplementary material). Similarly, studies of loess deposits in the Eu anomaly (see the supplementary material). Eastern Mountains suggested a mixed source (Zhang et al. In the Harbin area, the weather linked to dust transport events 2012), with one source being the local or neighbouring clastic mainly occurs in spring when the dominant wind directions are deposits, and another, more distal source, being the same as for the southwesterly (accounting for 85.7%), northwesterly (11.1%) and loess of the Chinese Loess Plateau. This may provide an analogue for easterly (3.2%), with an annual predominant wind direction of SW the neighbouring source (i.e. the Songnen Sandy Land) contributing (Xie et al. 2014, and references therein). Consequently, the potential substantially to the loess deposition in our study region. However, as Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

Geochemistry of Harbin loess deposits 159 indicated by the modern dust-storm pathways (see fig. 1 of Xie & Chi the loess accumulation in the Sanmenxia Gorge has a strong affinity 2016), dust from the distal source (i.e. the Horqin Sandy Land) may with the disappearance of the Sanmen Palaeolake (Jiang et al. 2007; have served as another non-negligible dust source. Zheng et al. 2007). The dryout of the Sanmen Palaeolake not only If this is the case, a mixture of binary geochemical compositions provided abundant dust particles for loess accumulation in this from the Songnen Sandy Land and the Horqin Sandy Land can be region but also considerably increased the loess accumulation rate. documented in the Harbin aeolian loess; that is, the geochemical Analogously, there also is a striking linkage between the Harbin composition for the Harbin aeolian loess is expected to be between loess accumulation and the disappearance of the large Songliao those of the Songnen Sandy Land and the Horqin Sandy Land. The palaeolake. The dried-up lake bed and riverbed were extensively average compositions of the aeolian loess and the three potential exposed when the Songliao palaeolake dried up as a result of the sources plot along a trend line (i.e. mass gain–mass loss paths cold–dry climate and uplift of the Songliao Watershed (Sun 1990; extending from the origin), and, moreover, the studied loess– Zhang 1990). In this context, the dust particles sourced from the palaeosol data plot between those of the Songnen Sandy Land and exposed lake bed and riverbed were transported by surface winds in the Horqin Sandy Land, as would be expected. In addition, the three short-term suspension and accumulated in the adjacent downwind potential sources show a large variation range in geochemical areas in a sufficient thickness to form the Harbin loess. Here, we compositions (see Figs 8 and 9), indicating the heterogeneity of present more convincing evidence supporting this hypothesis from provenance composition. In contrast, comparatively homogeneous the perspective of the stratigraphic structure and depositional source. composition can be seen in the Harbin aeolian loess, suggesting In the Huangshan section studied here, the Harbin loess deposits good mixing during transport. Based on this homogenizing process unconformably overlie the Huangshan Formation (including the in the formation of loess, it can be understood that any one of the lower and upper Huangshan Formation, which are lacustrine three potential provenances alone may be insufficient to form this sediments) (see Fig. 1), which indicates that there is a shift of the composition of the Harbin loess whereas a contribution from both sedimentary environment from lacustrine deposits to aeolian the Songnen Sandy Land and the Horqin Sandy Land can be deposits. The highest lake level of the large Songliao palaeolake, expected. This finding reveals that the Harbin aeolian loess was although a matter of debate, is believed to have affected the Harbin derived from the mixture of sources from the Songnen Sandy Land region and, accordingly, the Huangshan Formation is held to be a and the Horqin Sandy Land. northeastern edge of the large Songliao palaeolake sedimentation. When the lake level of the large Songliao palaeolake retreated Implication for disappearance of the large Songliao gradually toward the SW from the Harbin region, there was a lack of palaeolake sedimentation in the Huangshan area in Harbin and consequently an erosion surface formed at the top of the Huangshan Formation. The large Songliao palaeolake, which formed during the Early When an extensive area of lake bed and riverbed was exposed owing Cretaceous and disappeared during the Palaeogene and then again to gradual shrinkage of the large Songliao palaeolake to appeared in the late Miocene following by its maximum develop- disappearance, abundant amounts of dust particles were deflated ment in the Pliocene (Yang et al. 1983), continued to develop during by surface winds and transported towards the adjacent downwind the Quaternary on the basis of the lake area in the Cretaceous and areas, with the result that the Harbin Formation unconformably Tertiary. It is generally suggested that the large palaeolake had two overlies the Huangshan Formation. Additionally, provenance high lake levels in the Early and Middle Pleistocene (Qiu et al. 1983, studies of the Harbin loess deposits using a proxy-comparison 1988, 2012). The palaeolake was bounded by a long ellipse-shaped method, as described above, confirmed the importance of the region marked by the Qiqihaer–Lindian–Anda–Zhaozhou–Fuyu– Songnen Sandy Land source. Our geochemical data for the Songnen Changling–Taonan–Baicheng sites, the total area of which is about Sandy Land are chiefly from the alluvial–lacustrine sediments of the 5×104 km2. However, little is known about the time of disappear- palaeolake region and, accordingly, the clear correlations between ance of this palaeolake, mainly because of the lack of a reliable the palaeolake sediments and the Harbin loess strongly support our method for determining this time. Thick clay layers, an indicator of hypothesis that there is a good linkage between the large Songliao lacustrine deposits and evolution (Qiu et al. 1983, 1988, 2012; Qiu palaeolake disappearance and Harbin loess accumulation. 2008), are customarily employed to reflect the range and evolution It is, in fact, a significant mode for formation of loess that the process of the large palaeolake (Qiu 2008; Qiu et al. 2012). This adjacent exposed areas of lake beds and river channels act as dust approach requires many bores at different sites in the large sources (e.g. Hu & Yang 2016; Nie et al. 2015). Therefore, we palaeolake to constrain the age of its evolution, because the clay tentatively suggest that the Harbin loess could record the evolution layers in varying locations are of variable accumulative thickness of the large Songliao palaeolake and can serve as direct evidence of and depositional age. Moreover, the time represented by the clay the Songliao palaeolake disappearance, which will allow us to layers is probably only an approximation of the ultimate time of the obtain the ultimate time of the Songliao palaeolake disappearance. large palaeolake disappearance. Therefore, the scheme for con- This suggestion is only preliminary and further precise dating for the straining the time of disappearance of the large palaeolake based on Harbin loess is needed to quantify the timing of the Songliao the clay layers is not a perfect one. palaeolake disappearance. Loess is commonly believed to be the product of a cold and dry climate at both its source and deposition sites. There are three fundamental requirements for the formation of loess (Tsoar & Pye Summary and conclusions 1987; Pye 1995): (1) a sustained source of dust; (2) adequate wind Here we report on detailed geochemical characteristics that will help energy to erode and transport it; (3) a suitable site for dust us understand the chemical weathering, sedimentary recycling and accumulation. A sustained dust supply is essentially related to provenance of the Harbin loess and palaeosols representative of the geomorphological–tectonic processes in the dust source region. NE loess, as well as make an important contribution to under- More specifically, loess accumulation has a close relation to standing the formation history of the Songliao palaeolake. geomorphological or tectonic evolution in the dust source. There is Geochemical investigations have revealed the following. an argument that aeolian loess deposits faithfully record the evolution of a fluvial–lacustrine landform (e.g. Wu et al. 1999; (1) Both the loess and palaeosols have remarkably uniform Wang et al. 2002; Pan et al. 2005; Jiang et al. 2007; Zheng et al. geochemical compositions, reflecting a stable and identical 2007; Kong et al. 2013). Previous investigations have indicated that dust source. Downloaded from http://jgs.lyellcollection.org/ by guest on January 11, 2018

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(2) The source-area weathering and sedimentary recycling Chen, J. & Li, G.J. 2011. Geochemical studies on the source region of Asian dust. – history indicated by various weathering indicators suggests Science China: Earth Sciences, 54, 1279 1301, https://doi.org/10.1007/ s11430-011-4269-z that the Harbin loess and palaeosols experienced a low Chen, J., An, Z.S., Liu, L.W., Ji, J.F., Yang, J.D. & Chen, Y. 2001. Variations in degree of weathering as well as simple or weak recycling chemical compositions of the eolian dust in Chinese Loess Plateau over the processes. Based on this, we speculate that the studied loess past 2.5 Ma and chemical weathering in the Asian inland. Science in China (Series D), 44, 403–413. and palaeosols were more likely to be sourced from Chen, J., Li, G.J. et al. 2007. Nd and Sr isotopic characteristics of Chinese alluvial–lacustrine deposits rather than from aeolian sand. deserts: implications for the provenances of Asian dust. Geochimica et (3) Combinations of various provenance tracing indicators Cosmochimica Acta, 71, 3904–3914. collectively reveal the geochemical affinities of the Harbin Chen, L.Q., Guo, F.S., Steel, R.J. & Li, Y.L. 2016. Petrography and geochemistry of the Late Cretaceous redbeds in the Gan-Hang Belt, southeast China: loess and palaeosols with the Songnen Sandy Land and to a implications for provenance, source weathering, and tectonic setting. certain extent the Horqin Sandy Land. Therefore, it is International Geology Review, 58, 1196–1214. concluded that the Harbin aeolian loess has a mixture of Condie, K.C. 1991. Another look at rare earth elements in shales. Geochimica et Cosmochimica Acta, 55, 2527–2531. provenances, with the dominant source being the neigh- Condie, K.C. 1993. Chemical composition and evolution of the upper continental bouring Songnen Sandy Land and a second, distal source crust: Contrasting results from surface samples and shales. Chemical Geology, being the Horqin Sandy Land. 104,1–37. (4) The Harbin loess could record the evolution of the Cox, R., Lowe, D.R. & Cullers, R.L. 1995. The influence of sediment recycling and basement composition on evolution of mudrock chemistry in the Songliao palaeolake and could be employed as direct southwestern United States. Geochimica et Cosmochimica Acta, 59, evidence of the Songliao palaeolake disappearance. 2919–2940. Cullers, R.L. 1994. The chemical signature of source rocks in size fractions of Holocene stream sediment derived from metamorphic rocks in the Wet Mountains region, Colorado, U.S.A. Chemical Geology, 113, 327–343. Acknowledgements We would like to express our appreciation to Cullers, R.L. 1995. The controls on the major- and trace-element evolution of Youbin Sun and Mu Liu for their help in geochemical and Sr–Nd isotopic shales, siltstones and sandstones of Ordovician to Tertiary age in the Wet composition determination. We are also grateful to two anonymous reviewers and Mountains region, Colorado, U.S.A. Chemical Geology, 123, 107–131. A. F. Bird (Subject Editor) for their very constructive comments and suggestions. Cullers, R.L. 2000. The geochemistry of shales, siltstones, and sandstones of We also thank G. Pearce for detailed language polishing. Thanks also go to Hong Pennsylvanian–Permian age, Colorado, USA: implications for provenance Zhang and Yuxi Xie for their assistance in field sampling. Kui He partly and metamorphic studies. Lithos, 51, 181–203. participated in the fieldwork for the loess–palaeosol sampling. Cullers, R.L. & Podkovyrov, V.N. 2000. Geochemistry of the Mesoproterozoic Lakhanda shales in southeastern Yakutia, Russia: implications for mineral- ogical and provenance control, and recycling. Precambrian Research, 104, Funding This work was funded by the National Natural Science Foundation 77–93. of China (Grant 41471070). Das, B.K., Al-Mikhlafi, A.S. & Kaur, P. 2006. 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