Yangtze River sediments from source to sink traced with clay mineralogy

Journal of Asian Earth Sciences 69 (2013) 60–69

Contents lists available at SciVerse ScienceDirect

Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes

Yangtze River sediments from source to sink traced with clay mineralogy Mengying He a, Hongbo Zheng b,⇑, Xiangtong Huang c, Juntao Jia d, Ling Li a a

Institute of Surficial Geochemistry, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, PR China School of Geography Science, Nanjing Normal University, Nanjing 210046, PR China c State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, PR China d School of Earth Science & Technology, China University of Petroleum, Qingdao 266555, PR China b

a r t i c l e

i n f o

Article history: Available online 13 October 2012 Keywords: Clay minerals Provenance Weathering Erosion The Yangtze River

a b s t r a c t River bed sediments were collected from the main stream and major tributaries of the Yangtze River for clay mineralogy study. Surface sediments from the Yarlung Zangbo River on the Tibetan Plateau were also examined for comparison. The results show that the clay mineral compositions of the Yangtze River display a similar pattern through the whole truck stream, with illite being dominant, kaolinite and chlorite being lesser abundant, and smectite being minor component. Clay mineralogy shows distinct differences in the tributaries, which correspond to the heterogeneous source rocks and weathering intensity of the drainage. The illite crystallity and the illite chemical weathering index (5 Å/10 Å peak ratio) both increase downstream, indicating a increasing trend of hydrolysis along the river. It also indicates that the upperstream of the drainage is characterized with physical weathering while the middle- and lower reaches are controlled by chemical weathering process. In accordance with the result derived by the illite indexes, sediment input from upperstream including Yalong Jiang, Dadu He, Min Jiang and Jialing Jiang accounts for the major sediment load, whereas Wu Jiang, Xiang Jiang, Gan Jiang and Dongting Lake provide relatively less sediments. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction The large river systems draining the Tibetan Plateau are the major transfer of continental masses to the ocean, playing significant roles in global geochemical cycles, and are thus the key areas in the ‘‘source to sink’’ studies. Information about the bedrock lithology, weathering regimes, erosion and sedimentation rates are all fundamental issues in better understanding the catchment behaviors. Heavy minerals and geochemical fingerprints of river sediments are most widely used for the determination of provenance, tectonics and weathering in the source region (Moral-Cardona et al., 1996; Clift et al., 2002a,b,c; Cawood et al., 2003; Kuhlmann et al., 2004; Boulay et al., 2005; Moral Cardona et al., 2005; Lim et al., 2006; Alt-Epping et al., 2007; Lan et al., 2007; Borges et al., 2008; Liu et al., 2008; Yang et al., 2009; Singh, 2010; Wu et al., 2011). Clay mineral assemblages are sensitive to bedrock geology and chemical weathering and therefore have long been regarded as a powerful indicator of the nature of the source areas. In addition, in comparison with heavy minerals, clay minerals are easily transported as suspended load, and are more powerful to trace the provenance (Franz et al., 2001; Gingele et al., 2001; Chen

⇑ Corresponding author. Tel.: +86 25 83597512. E-mail addresses: [email protected] (M. He), [email protected] (H. Zheng). 1367-9120/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jseaes.2012.10.001

et al., 2003; Kessarkar et al., 2003; Liu et al., 2003a,b; Suresh et al., 2004; Liu et al., 2007; Long et al., 2007; Dou et al., 2010). As one of the rivers that originate from the eastern Tibetan Plateau, the Yangtze River is the third longest in the world and the fourth largest in terms of its water discharge. It has numerous tributaries, entering the East China Sea with great amount of water discharge, sediments and associated chemicals. The changes of the Yangtze River deposition area and the process of sediments from ‘‘source to sink’’ transport pattern have been widely discussed. In recent years, various approaches of the sediment source in the Yangtze River have been performed, such as Sr–Nd isotopic compositions (Yang et al., 2007), detrital mineral compositions (Wang et al., 2006; Yang et al., 2006), heavy mineral compositions (Yang et al., 2009), carbon distribution (Wu et al., 2007) and magnetic properties (Wang et al., 2007; Liu et al., 2010), whereas the clay assemblages of the Yangtze River drainage, and their implications, have not been fully investigated. Previous studies examined the clay mineralogy based on scattered samples collected mainly from the Yangtze estuarine and the inner shelf area, and were mostly concerned with their general comparison with other rivers, such as the Yellow River and Pearl River (Yang, 1988; Fan et al., 2001; Zhou et al., 2003; Ding et al., 2004; Fang et al., 2007). In this study, we will examine the clay mineral assemblages of the river bed samples from the main stream and major tributaries of the Yangtze River, as well as the surface (soil) samples from the drainage basin. The principal objectives are to characterize the clay

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

mineral distribution in the Yangtze River drainage, determining the mixing of sediments from different tributaries, and ultimately to understand how tectonics, basement geology and climates interplay to control the erosion and the production of clay mineral in the drainage. 2. The Yangtze River catchment The Yangtze River is one of the world’s great rivers, which is about 6300 km long. With a catchment area of 1.8  106 km2 and an annual average discharge of 9.6  1011 m3, it is the largest river in China and ranks the third in the world. The Yangtze River catchment can be divided into five broad physiographic provinces. From west to east, these include the northeast Tibet Plateau, the high mountains of the Longmen Shan (‘‘Shan’’ is ‘‘Mountain’’ in Mandarin) and associated ranges, the Sichuan Basin, mixed mountain and basin terrains (broadly referred to as the Three Gorges area), and eastern lowlands. Conventionally, the basin is divided into three reaches, the upstream, midstream and the downstream (Chen et al., 2001), but geographically, the upstream can be divided into two segments, the Jinsha Jiang segment and the Chuan Jiang segment (Fig. 1). The Jinsha Jiang (‘‘Jiang’’ means ‘‘River’’) descends from the plateau through the mountains and is joined in the Sichuan Basin by several major tributaries that pass through very deep valleys and gorges in the Longmen Shan, including the Yalong Jiang, the Dadu He (‘‘He’’ is ‘‘River’’ in Mandarin), and the Min Jiang. The Chuan Jiang mainly flows through the Sichuan Basin, containing the tributaries of the Jialing Jiang and the Wu Jiang, which are joined the main stream before passing through the Three Gorges to the eastern lowlands. Further midstream, the Yangtze River is joined by the Han Jiang from the mountainous northwest, and the Yuan Jiang, Xiang Jiang and Gan Jiang from the south. And several large lakes such as Dongting Lake and Poyang Lake separate the tributaries from the mainstream and trap a great deal of sediments. From Hukou downstream, the Yangtze River enters the lower reaches, and tributaries are much smaller in size compared with that in the upper reaches. Geologically, the Yangtze River runs across the Yangtze Craton framed by the Mesozoic Yanshanian orogenic belt. It is characterized by complex rock compositions, including widely distributed carbonate rock, continental sandstone, volcanic rocks and gneiss

61

(Yang et al., 2004; Wu et al., 2005). Different drainage basins in the mainstream and its major tributaries consist of distinct tectonics and source rocks. Generally speaking, in the upper basin, the drainage is covered by Mesozoic rocks with subordinate upper Paleozoic and Cenozoic rocks, the eastern Tibetan Plateau is mainly the metaigneous and metasedimentary rocks, carbonate rock and igneous rock, especially the Himalayan intermediate-acid igneous rock, which is rich in K. The middle-lower basins mostly consist of Paleozoic marine and the Quaternary fluviolacustrine sedimentary rocks, together with intermediate-felsic igneous rocks, and older metamorphic rocks. Clearly, different tributaries consist of distinct tectonic and source rock types (Fig. 2). Tectonically, the upper and lower reaches are very different: the western catchments, dominated by the Longmen Shan, are subject to ongoing uplift, whereas eastern China is comparatively stable. The Longmen Shan rises to over 6000 m, and the rivers receive large inputs of sediment from landslides cascading off steep unstable slopes that rise 1500–2500 m above the local valleys. In contrast, the eastern lowlands are a complex of floodplains and lacustrine basins, rimmed by relatively low mountains. Meteorologically, the Yangtze River catchment is dominated by Asian monsoon system, with seasonal alternation between the warm and wet summer monsoon, and the cold and dry winter monsoon. However, there is slight difference in the patterns of monsoon precipitation between the upper and lower streams, because the upper mainly receives rainfall from the south Asian monsoon. Annual precipitation tends to decrease westward from about 1000 mm in the eastern lowlands to about 700 mm in the Sichuan Basin, but rises to over 1700 mm on the eastern flanks of the central Longmen Shan. West of the Longmen Shan, precipitation decreases across the plateau, from about 600 mm in the middle reaches of the Yalong Jiang to about 400 mm at the head of the Jinsha Jiang. Summer temperatures tend to be warm throughout the Yangtze River catchment, particularly in the eastern lowlands where the average for July can exceed 30 °C. Winter is mild to cool in the eastern lowlands and Sichuan Basin, whereas winter on the plateau is very cold and dry, with sub-zero temperatures. The mountains of the Longmen Shan are covered by permanent snow above 5100–5300 m (The Changjiang Water Resources Commission. See http://www.cjw.gov.cn).

Fig. 1. The landscape of the Yangtze River drainage basin. It can be divided into four parts: the Jinsha Jiang segment, Chuan Jiang segment, Midstream and Downstream.

62

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

Fig. 2. A sketch geology map of the Yangtze River drainage basin. 1–12: major tributaries.

3. Sampling strategy and laboratory analysis This study of large-scale sediment sources and sinks in the Yangtze River system began in the year May 2001 with collection of bulk samples of river sand and mud from the delta, trunk stream and major tributaries. Sampling was extended in July 2004 into selected headwaters of the Yangtze River in the Longmen Shan and adjacent plateau, where samples were collected from exposed bedrock surfaces and top soils, as well as from larger rivers. In March 2008 and 2009, sampling of sand from trunk stream and major tributaries was repeated, because some of the samples collected previously were used up. Channel deposits tend to be preserved stratigraphically, such as mid-channel bars, lateral bars and point bars, and were preferred targets. Sampling was intentionally carried out during seasons of low river levels except in 2004, so that channel deposits are accessible. A number of samples were taken from river dredges or from stockpiles of dredged sand when river levels were high. Aiming to get representative material, our riverbed samples were mixtures of sub-samples taken from several points around each sampling site, whereas dredge and stockpile samples were assumed to have been well-mixed during dredging operations. Sand and mud samples (totally 56 sediment samples) were collected from the mainstream and major tributaries of the Yangtze, including 47 sand samples and nine soil samples which are mainly located in the upstream. The sampling sites cover the whole drainage, from the ‘‘first bend’’ in Shigu to the river mouth in Shanghai (Fig. 3). The samples from the major tributaries were taken at the confluence with the mainstream, surely avoid cities and possible pollution places. In addition, we also took four sand samples and three soil samples in the Yarlung Zangbo River and its tributaries in Tibet. Clay mineral analyses were identified by X-ray diffraction (XRD) on oriented mounts of clay sized particles (<2 lm), which were based on the Stokes settling velocity principle after removal of carbonate and organic matter. Three XRD runs were performed, following air-drying, ethylene-glycol salvation and the slow-scan. The first

two runs were measured from 3° to 36°2h, with a step size of 0.01°, and the last was from 24° to 26°2h, with a step size of 0.0025°. Identification and interpretation of clay minerals were made according to the XRD diagram of ethylene-glycol salvation. Semiquantitative calculations of each peak’s parameters were carried by JADE software. Relative percentages of illite, smectite, kaolinite and chlorite were determined using ratios of integrated peak areas of (0 0 1) series of their basal reflections, and were weighted by empirically estimated factors (Biscaye, 1965). Accordingly, the smectite 17 Å peak area is multiplied by 1, the 10 Å illite peak area by 4 and both the kaolinite and chlorite proportions of their 7 Å peak by 2 (Petschick et al., 1996). Kaolinite with a peak at 3.58 Å and chlorite at 3.54 Å were identified from the slow-scan diagrams. Additionally, some mineralogical characters of illite were determined on the glycolated curve. Illite chemistry index refers to the 5 Å/10 Å peak areas. This ratio can be useful to discover clay mineral sources and hydrolysis strength. According to Esquevin (1969), high 5 Å/10 Å values (>0.4) correspond to Al-rich (muscovite) illite, which is released following strong hydrolysis, while ratios below 0.4 represent (Fe,Mg)-rich illites, which is characterized for physically eroded or unweathered rocks (Liu et al., 2003a,b; Wan et al., 2008). As a measure of the lattice ordering and the crystallite size of clay minerals, illite crystallinity is used to trace source regions and transport paths. It is made by computing the IB (=integral-breadth or integral-width) of the glycolated 10 Å-illite peaks. The IB is the width (in °D2h) of the rectangle, which is of the same height and same area as the measured peak (Petschick et al., 1996). IB-values are more sensitive for peak tail variations than the usually applied FWHM = full width at half maximum (Krumm and Buggisch, 1991). Lower IB-values indicate higher crystallinity, characteristic of weak hydrolysis in continental sources and climate conditions (Ehrmann, 1998). 4. Results It is shown from the X-ray spectra (Fig. 4), the clay mineral assemblages of the Yangtze River drainage consist mainly of illite,

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

63

Fig. 3. Locations of surface samples in the Yangtze River drainage basin and the Yarlung Zangbo River drainage. See Table 1 for detailed geographic positions.

Fig. 4. Characteristic diffraction profiles of typical samples from the Yangtze River drainage basin. Samples YZ27 from Fuling, YZ20 from Yibin and YZ51 from Nanchang contain very scarce smectite, sample YZ2 from Lijiang contains relatively more semctite. Sample YZ51 contains more kaolinite. See Fig. 1 and Table 1 for detail information.

64

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

kaolinite, chlorite and smectite (Table 1). Illite (23–90%) is the most dominant clay mineral with an average of 69%. Kaolinite (1–55%) and chlorite (3–26%) are less abundant with average contents of 15% and 14%, respectively. Smectite is very scarce, and is <5% for most samples with two exceptions (>5%) in the tributaries. Illite chemistry index of all the Yangtze River sediments is between 0.21 and 1.33 with the average of 0.47, indicating that most illite is rich in Al, and forms under a strong hydrolysis environment. Illite

IB-values fall in the range of 0.29–0.89°D2h with the average of 0.45°D2h. The clay mineral distribution of surface sediments through the main stream displays a similar pattern (Fig. 5). In the main stream, the average contents of chlorite and smectite are nearly stable while the average contents of illite and kaolinite have opposite variations. From the Jinsha Jiang to the downstream, chlorite is 16%, 18%, 14% and 17%, respectively, and smectite is 4%, 1%, 3%

Table 1 Geographic locations and clay mineral assemblages of surface sediments in the Yangtze River drainage basin and the Yarlung Zangbo River. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63

Samples YZ01 YZ02 YZ03 YZ04 YZ05 YZ06 YZ07 YZ08 YZ09 YZ10 YZ11 YZ12 YZ13 YZ14 YZ15 YZ16 YZ17 YZ18 YZ19 YZ20 YZ21 YZ22 YZ23 YZ24 YZ25 YZ26 YZ27 YZ28 YZ29 YZ30 YZ31 YZ32 YZ33 YZ34 YZ35 YZ36 YZ37 YZ38 YZ39 YZ40 YZ41 YZ42 YZ43 YZ44 YZ45 YZ46 YZ47 YZ48 YZ49 YZ50 YZ51 YZ52 YZ53 YZ54 YZ55 YZ56 YZ59 YZ61 YZ60 YZ62 YZ65 YZ63 YZ64

Longitude 0

Latitude 00

99°58 52.08 100°02.3750 101°290 25.800 101°310 48.100 101°490 16.200 101°490 13.800 104°240 1200 101°560 14.400 102°480 32.300 102°130 17.100 102°110 49.300 102°110 49.300 102°350 44.800 102°590 41.700 102°410 38.400 102°590 41.700 103°430 8.800 103°370 42.100 103°520 47.400 104°350 900 104°410 26.400 106°320 19.200 106°290 22.200 106°190 8.600 106°290 1.800 106°370 0.600 107°210 8.600 107°320 13.800 107°230 33.800 107°240 37.200 110°200 45.900 111°180 43.700 112°140 27.200 112°240 1500 113°50 31.900 112°550 07.600 111°410 11.200 113°50 31.900 113°060 08.900 112°560 55.200 113°110 27.300 113°530 30.800 114°140 32.300 114°170 25.800 111°470 53.600 112°70 3800 113°250 57.800 114°250 32.900 115°540 29.600 116°120 34.500 115°510 21.500 116°180 26.800 118°200 3.400 118°390 59.000 118°390 59.000 121°460 08.100 90°550 46.600 90°550 46.600 89°350 43.500 88°490 15.100 88°510 29.400 90°100 18.500 90°410 08.500

0

00

26°52 14.46 26°51.6060 26°350 16.200 30°190 42.600 26°460 2.400 26°350 28.800 28°430 24.600 30°540 34.600 30°010 31.200 29°530 32.100 30°000 15.800 30°000 15.800 30°590 4.800 30°530 3200 29°490 48.0600 29°500 54.900 32°050 37.200 32°320 25.800 30°040 36.900 28°470 4.800 28°470 0000 29°280 18.600 29°230 35.400 30°40 23.300 29°330 22.800 29°370 11.400 29°440 1.000 29°240 24.200 29°360 20.800 29°440 8.400 31°30 2.800 30°390 49.500 30°170 43.900 30°10 42.600 29°230 48.800 29°320 49.500 29°010 25.900 29°230 48.800 29°240 02.100 28°080 51.600 29°290 28.500 29°580 56.300 30°280 31.000 30°330 16.900 32°60 5800 32°10 38.600 30°230 33.500 30°400 19.100 29°430 07.500 29°450 11.300 28°380 57.900 29°460 03.100 31°210 12.100 31°590 04.600 31°590 04.600 31°200 38.100 29°260 40.900 29°260 40.900 28°540 37.000 29°190 05.300 29°190 07.300 29°200 52.500 29°190 38.200

Locations

Smectite%

Illite%

Kaolinite%

Chlorite%

Illite chemistry index

Illite IB-values (°D2h)

Shigu Shigu Panzhihua Tagongxiang Panzhihua Panzhihua Yibin Daduhe Qingyijiang Daduhe Daduhe Daduhe Xiaojinchuan Balangshan Daduhe Daduhe Diexihai Minjiang Meishan Yibin Yibin Chongqing Chongqing Yunmen Chongqing Chongqing Fuling Wujiang Fuling Fuling Badong Yichang Shashi Jiangling Jianli Yueyang Changde Dongting Lake Yueyang Changsha Yueyang Jiayu Wuhan Wuhan Xiangfan Xiangfan Xiantao Wuhan Jiujiang Hukou Nanchang Hukou Wuhu Nanjing Nanjing Changxing Island Lasa River Gyantse Nianchu River Xigaze Yarlung Zangbo River Lhasa Yarlung Zangbo River

0.34 7.47 4.99 2.33 1.32 4.44 0.39 0.37 0.71 2.54 2.12 1.27 0.35 0.35 0.54 0.27 0.17 0.26 3.65 0.14 0.21 0.33 0.01 25.52 3.23 3.44 1.11 1.04 0.58 0.64 1.39 0.74 5.73 5.06 4.57 1.34 0.00 0.98 1.02 0.10 4.58 5.04 1.75 2.33 4.94 1.42 9.72 1.15 1.06 0.95 1.02 2.25 0.27 0.91 3.64 0.30 5.00 1.98 0.14 2.17 7.00 1.90 9.86

72.57 75.33 57.29 68.59 55.90 62.27 66.37 88.45 75.28 81.60 80.94 77.50 87.64 89.97 78.31 81.63 82.79 82.76 69.63 69.43 61.56 67.60 68.24 63.21 65.82 62.62 56.82 87.23 74.98 71.78 81.98 62.31 70.29 67.34 69.52 69.69 70.67 45.87 51.31 40.41 58.35 68.18 74.22 70.13 83.92 71.94 63.36 63.36 63.59 63.47 23.49 59.03 79.26 64.94 56.17 56.85 84.03 85.29 78.24 72.81 67.93 83.19 73.20

9.93 9.04 17.56 16.35 23.02 13.16 14.18 2.41 4.86 1.91 3.54 12.01 3.31 1.63 8.91 2.23 5.89 7.37 13.36 9.84 12.42 15.24 15.88 7.20 14.90 15.41 20.91 5.27 12.22 16.98 8.48 20.70 7.60 10.19 11.53 11.91 19.87 30.91 28.19 46.02 18.68 12.91 14.96 9.87 1.43 13.33 23.25 32.44 17.51 25.24 55.08 19.53 8.57 17.10 22.22 23.29 5.33 5.20 1.68 6.96 9.39 3.98 6.73

17.16 8.16 20.17 12.73 19.76 20.13 19.06 8.78 19.16 13.96 13.40 9.21 8.69 8.04 12.24 15.87 11.14 9.61 13.36 20.59 25.81 16.83 15.88 4.06 16.05 18.53 21.16 6.46 12.22 10.60 8.15 16.26 16.39 17.41 14.38 17.06 9.46 22.25 19.48 13.46 18.40 13.87 9.07 17.67 9.71 13.31 3.90 3.06 17.84 10.34 20.41 19.19 11.90 17.05 17.96 19.56 5.64 7.53 19.93 18.06 15.68 10.93 10.21

0.27 0.60 0.42 0.38 0.49 0.36 0.30 0.32 0.40 0.24 0.28 0.43 0.34 0.32 0.32 0.47 0.35 0.33 0.31 0.39 0.53 0.53 0.46 0.33 0.39 0.35 0.50 0.36 0.40 0.64 0.58 0.68 0.49 0.44 0.37 0.42 0.47 0.52 1.16 0.97 0.50 0.43 0.33 0.52 0.21 0.32 0.34 0.49 0.60 0.50 1.33 0.47 0.40 0.39 0.68 0.67 0.13 0.19 0.26 0.66 0.42 0.30 0.50

0.29 0.46 0.38 0.42 0.39 0.36 0.35 0.35 0.45 0.45 0.39 0.41 0.40 0.44 0.57 0.58 0.39 0.36 0.40 0.40 0.48 0.38 0.43 0.49 0.39 0.38 0.40 0.67 0.57 0.67 0.48 0.43 0.47 0.45 0.47 0.46 0.47 0.37 0.46 0.45 0.34 0.49 0.40 0.51 0.52 0.42 0.37 0.41 0.45 0.89 0.52 0.47 0.40 0.46 0.51 0.56 0.77 0.59 0.70 0.77 0.45 0.66 0.65

65

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

Fig. 5. Average clay mineral contents in surface sediments of the Yangtze River drainage basin (1–4: main stream; 5–14: tributaries).

and 1%, respectively. However, the content of illite decreases from 67% to 63%, and kaolinite increases from 12% to 18% (Table 2). For the tributaries, obvious differences are revealed. The average contents of illite in the upstream especially the Dadu He and the Wu Jiang are 80% (Fig. 5:6, 9), but in the midstream, the Dongting Lake, Xiang Jiang and Gan Jiang (Fig. 5:11, 12, 15) are all less than 50%. Whereas the average contents of kaolinite in the midstream such as the Xiang Jiang, Dongting Lake, Gan Jiang and the Poyang Lake (Fig. 5:11, 12, 14, 15) are all above 25%, while the Dadu He, Min Jiang and Wu Jiang in the upstream are below 10% (Fig. 5:6, 7, 9). In addition, the high average content of smectite concentrates on the Jialing Jiang (Fig. 5:8) with an average of 14% and the Han Jiang (Fig. 5:13) which is 5%. There is a clearly changing of Illite IB-values in the main stream, increasing from the average 0.37°D2h in the Jinsha Jiang to 0.44°D2h in the Chuan Jiang, and 0.45°D2h in the midstream to 0.48°D2h in the downstream, which indicate that the crystallinity of the Yangtze sediments becomes poor and the hydrolysis of the drainage gets strong (Table 2). The same as the IB-values, illite chemistry index in the main stream is from 0.41, 0.47 to 0.48 and 0.53, respectively and that of the tributaries also increases along the drainage. In the upstream, the illite chemistry index of

all the tributaries are below 0.4, except the Yalong Jiang, representing a weak hydrolysis, and a mainly physical weathering. But that of the Xiang Jiang, Dongting Lake and Gan Jiang in the midstream are all above 0.8, indicating that the chemical weathering dominates and the hydrolysis is strong in this area (Table 2). The clay mineral distributions in the Yarlung Zangbo River are similar to the Yangtze River. Illite is also the controlled mineral, but the average content is much higher, about 78%. Chlorite (12%) is much more than kaolinite (6%). The average content of smectite is 4%, higher than that of the Yangtze drainage. The illite chemistry index is 0.35, indicating a weak hydrolysis (Table 1 and Fig. 5).

5. Discussion 5.1. Source rock and weathering control on clay mineral associations Clay minerals are practical ubiquitous in modern soils and sediments, they are also the primary component phases in shales, which constitute the surface or nearest-surface bedrock on most of the continents. The formation of clay minerals assemblages in

Table 2 Average clay mineral assemblages of main stream and various tributaries in the Yangtze River drainage basin. Rivers

Sample number

Smectite%

Illite%

Kaolinite%

Chlorite%

Illite chemistry index

Illite IB-values (°D2h)

Jinsha Jiang Chuan Jiang Yalong Jiang Dadu He Min Jiang Jialing Jiang Wu Jiang Midstream Han Jiang Yuan Jiang Dongting Lake Xiang Jiang Gan Jiang Poyang Lake Downstream

4 7 2 9 4 2 2 12 3 1 2 1 1 1 5

4 1 2 1 1 14 1 3 5 0 1 0 1 1 1

67 65 62 82 76 65 81 68 73 71 49 40 23 63 63

12 16 20 5 9 11 9 15 13 20 30 46 55 25 18

16 18 16 12 14 10 9 14 9 9 21 13 20 10 17

0.41 0.47 0.43 0.35 0.35 0.36 0.38 0.49 0.29 0.47 0.84 0.97 1.33 0.50 0.52

0.37 0.44 0.40 0.45 0.39 0.44 0.62 0.45 0.44 0.47 0.42 0.45 0.52 0.89 0.48

66

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

ancient sequences are controlled by pre- and post-burial conditions, containing geologic, climatic, tectonic process and sometimes even anthropogenic (Chamley, 1989; Thiry, 2000; Laura et al., 2002). In general, illite and chlorite are detrital clay minerals, products of physical weathering and glacial scour. Illite is considered as a primary mineral, which reflects decreased hydrolytic processes in continental weathering and increased direct rock erosion under cold and arid climate conditions, it may result from the weathering of micas and feldspars, their formation in soils and sediments is favored by high K+ and moderate silica concentrations. Chlorite is a characteristic mineral for low-grade metamorphic and basic source rocks, but it is not resistant to chemical weathering and transportation. Kaolinite and smectite, in contrast, are products of chemical weathering. Kaolinite often forms from weathering of the potassium feldspar and muscovite mica in rocks such as granite. High concentrations of kaolinite are normally restricted to moist temperate and tropical regions, where long-continued and intense hydrolysis, it is the clay that is most stable under acid-weathering conditions. Smectite normally forms by hydrolysis under climatic conditions between warm-humid and cold-dry, in environments characterized by very slow movement of water. They tend to form early in the weathering of unstable Fe-, Mg-, and Ca-rich minerals in igneous or metamorphic rocks. When smectite is buried in deep sedimentary basins, they are gradually transformed into more stable kaolinite by a combination of time and temperature (Biscaye, 1965; Zhang, 1992; Petschick et al., 1996; Lu, 1997; Ehrmann, 1998; Kong and Xiang, 2003; Liu et al., 2004). Due to the relationship of clay minerals and the source rocks, in the upper basin of the Yangtze River, the soils are frozen or form bogs at very high elevations, resulting in the clay minerals of soils in the eastern Tibetan Plateau are dominated by illite. Additionally, the tributaries in the Jinsha Jiang segment like Yalong Jiang and Min Jiang are covered by Paleozoic carbonate rocks, Permian basalt (the Emeishan basalt), Jurassic red sandstone, Mesozoic–Cenozoic sedimentary and igneous rocks (Pan et al., 1997; Qin et al., 2006). The young intermediate-acid igneous rocks and the basic basalt are available to the formation of illite and chlorite, so the upper region of the Yangtze River contains higher contents of illite and chlorite, especially the illite. Because of the strong tectogenesis of the Tibetan and the strong erosion of the river, the illite can be easily carried from the upstream to the mid-downstream, leading the whole drainage mainly illite (Fig. 5). In contrast, the drainages of Dongting Lake and the Poyang Lake are characterized by the red sandstone, shale and granite, resulting in higher content of kaolinite in this area, naturally, less illite. As for the Jialing Jiang and the Han Jiang, they all come from the Qinling Mountain, where mainly distribute the Quaternary loess, Cenozoic sedimentary rocks and

Paleozoic metamorphic rocks (Zhang et al., 2005). With the basic chemical composition in the upstream, the two drainages constitute more smectite. The uppermost stream of the Yangtze River drainage is strongly influenced by South Asian monsoon climate, while the reminder of the drainage is controlled by East Asian monsoon regime with warm and humid climate during summer season. Chemical weathering in the lower drainage is therefore generally intense. This is reflected by the chemical index of alteration (CIA) values. The CIA values in the upstream of the Yangtze River ranges from 46.5 to 69.2, with an average value of 60.5 in the upper stream, indicating relatively weak weathering degree (Wu et al., 2011). Whereas in the mainstream and major tributaries of the Yangtze River drainage, the CIA values reveal an increased trend, from 54.5 to 81.4, with an average value of 63.4, which represents an increasing chemical weathering (Shao et al., 2012). In this study, the average content of illite decrease about 20% from the upstream to downstream in the tributary rivers, and the illite chemical index and the illite crystallinity increase along the drainage, displaying a warmer and more humid trend climate. It is supposed the physical weathering in the upstream, especially the Jinsha Jiang segment, and the chemical weathering in the mid-downstream, which are accordant with the CIA value. And the change of weathering intensity is consistent with the clay composition. The contents of illite and chlorite are more in the upstream tributaries under a weak hydrolysis and a cold and arid climate conditions, while tributaries in the midstream contain more kaolinite because of the stronger hydrolysis and moist temperate. Obviously, clay mineral assemblages can reflect both the source rock types and weathering intensity. However, undeniable, higher illite content covers the main stream of the whole drainage, not varying with the weathering or the rock types (Fig. 5:1–4). Clearly, the sediments in the main stream can only reflect section information of the drainage. From the main stream alone to identify drainage weathering intensity is inadequate, it must be combined with the result of tributaries also. 5.2. Provenance reflected by the clay mineral distributions Without doubt, most sediment in the main stream of the Yangtze River comes from the tributaries, for that reason, the clay mineral distribution in the tributaries plays an important role in the main stream. The ternary diagrams with end members of illite, smectite and kaolinite + chlorite (Fig. 6) displays a pattern that the clay mineral assemblages in the main stream have few differences, containing more illite, less smectite. The contents of illite in the tributaries of the upstream are all higher than that of the

Fig. 6. The triangular map with end members of illite, smectite and gaolinite + chlorite.

67

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

main stream, like the Dadu He, Min Jiang and Jialing Jiang. Accordingly, we can deduce that the tributaries of the upstream contribute more to the main stream. Similarly, the content of smectite in the Jialing Jiang and Han Jiang is high, meanwhile, that in the midstream are higher than the Chuan Jiang segment, so the contributions to the main stream of these two rivers are more also. Whereas, the Xiang Jiang and Gan Jiang have more kaolinite and chlorite, but the content of them in the mid-downstream of the main stream is not much higher, supposedly, most of the kaolinite is reserved in the Dongting Lake and Poyang Lake. Thus, they contribute little to the main stream. Equally, the illite chemical index and illite crystallinity can also prove the conclusions above. The average illite chemical index increase from the up- to downstream, with highest in the Dongting Lake, the Xiang Jiang and Gan Jiang, but the index in the main stream does not change more from the up- to midstream (Table 2), it is not influenced by this high area, therefore, the Dongting Lake system and the Poyang Lake system not devote more sediments to the Yangtze drainage. Even more, as the tracer of the provenance, the illite crystallinity and the illite chemical index can be finely linearity (Fig. 7). Most samples concentrate in a region while that of the Wu Jiang, the Poyang Lake, Dongting Lake, Xiang Jiang and Gan Jiang are outside, this phenomena can also indicate that these rivers contribute little to the main stream. 5.3. Influence of the Tibetan Plateau on big rivers During the uplift of the Tibetan Plateau and surrounding ranges, tectonic processes have interacted with climatic change and local random effects to determine the development of the major river systems. Borges et al. (2008) investigated the petrography and major, trace and rare earth element compositions of the bed sediments from the large rivers draining the eastern Tibetan Plateau and found that the river sediments are felsic, similar to the upper continental crust. The high physical erosion in such high energy systems manifests a provenance control from local rocks on the sediment compositions. Wu (2011) analyzed the mineralogy and geochemistry of the riverbed sediments in the headwaters of the Yangtze River, concluding that the chemical weathering is very minor. In order to obtain a thoroughly recognition for the effect, we used previously published data of the clay minerals on the upper reaches of the Yellow River (Cheng et al., 2003) and Ganges (Raman et al., 1995). The clay mineral assemblages of these rivers are similar to the Yangtze River (Table 3). Illite is the dominate mineral and chlorite is less abundant, kaolinite and smectite are scarce, with the

Table 3 Clay mineral assemblages in the rivers originating from the Tibetan Plateau. Rivers The Yangtze River a

The Yellow River

The Yarlung Zangbo River The Gangesb a b

Smectite%

Illite%

Kaolinite%

Chlorite%

0 7 42 40 10 7 12 10

73 75 45 45 73 68 66 58

10 9 5 6 7 9 0 4

17 8 8 9 10 16 22 28

Cheng et al. (2003). Raman et al. (1995).

exception of the Yellow River. The content of smectite in the Yellow River is only less than the content of illite due to the widely distribution of loess in the source area. The same distribution of the clay minerals represents these big rivers have close source materials and have been subjected to the similar weathering and tectonics. Although the Yangtze River and the Yellow River originates from the eastern Tibetan Plateau and the Ganges and Yarlung Zangbo River are draining the southwest, they are all of Mesozoic– Cenozoic collisional age, currently active, and are lithologically complex with igneous intrusive and extrusive rocks, metamorphic rocks as well as clastic and carbonate sedimentary rocks, and some with ophiolite sequences (Borges et al., 2008). Higher contents of illite in these rivers reflect the actively eroding of the rocks in the source. In addition, in such high energy stream and fast sediment turnover systems, the local rocks in the source appear to be the first order control on the sediment compositions clearly. What’s more, the uplift of the Tibetan Plateau has dramatically increased the slope of the eastern Tibetan margin, where reside the upper reaches of the Yangtze and Yellow River. More primary minerals such as the illite and chlorite indicate more physical erosion of the plateau. These minerals are transported though the main stream very rapidly to the river delta without much chemical alteration. As well as the surface of the Tibetan Plateau, the Yarlung Zangbo River and the Ganges also reflect a strong mechanical denudation. As a result, the tectonic factors also exert control on the mineralogical variations in sediments. 6. Conclusions The X-rays diffraction analysis (XRD) was applied to measure the clay mineral compositions sediments in the Yangtze River and the Yarlung Zangbo River. Ilite, smectite, chlorite and kaolinite

Fig. 7. Correlations of illite chemistry index with illite IB-values of surface sediments in main stream and tributaries of the Yangtze River drainage basin. See Tables 1 and 2 for mineralogical data.

68

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69

are present as major clay minerals in the sediments. The clay mineral compositions of the Yangtze River display a similar pattern along the main stream, but different in the tributaries. The difference of these tributaries responds to the heterogeneous source rocks and weathering intensity. From the upstream to downstream, the hydrolysis of the drainage get strong, presuming that the upstream is mainly the physical weathering and the mid-downstream are controlled by chemical weathering. The contribution of tributaries in the upstream including the Yalong Jiang, Dadu He, Min Jiang and Jialing Jiang is larger, but Wu Jiang is minor. As for the midstream, except the Han Jiang supplies more volumes of the sediments, the Xiang Jiang, Gan Jiang, and Dongting Lake provide minor sediment to the downstream and the delta. The clay mineral assemblages of the rivers draining the Tibetan Plateau are controlled by the local rocks and tectonics of the source area. Acknowledgements This study was supported by XDB03020300, the Natural Science Foundation of China (Project No. 40930107) and United Nations Educational, Scientific and Cultural Organization (Project No. IGCP-581). We thank the State key laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University and all teachers of Nanjing University who helped us for laboratory work. References Alt-Epping, U., MIL-Homens, M., Hebbeln, D., Abrantes, F., Schneider, R.R., 2007. Provenance of organic matter and nutrient conditions on a river- and upwelling influenced shelf: a case study from the Portuguese Margin. Marine Geology 243, 169–179. Biscaye, P.E., 1965. Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and adjacent seas and oceans. Geological Society of America Bulletin 76, 803–831. Borges, J.B., Huh, Y., Moon, S., Noh, H., 2008. Provenance and weathering control on river bed sediments of the eastern Tibetan Plateau and Russian Far East. Chemical Geology 254, 52–72. Boulay, S., Colin, C., Trentesaux, A., Franck, N., Liu, Z., 2005. Sediment sources and East Asian monsoon intensity over the 1ast 450 ka. Mineralogical and geochemical investigations on South China Sea sediments. Palaeogeography, Palaeoclimatology, Palaeoeco1ogy 228, 260–277. Cawood, P.A., Nemchin, A.A., Freeman, M., Sircombe, K., 2003. Linking source and sedimentary basin: detrital zircon record of sediment flux along a modern river system and implications for provenance studies. Earth and Planetary Science Letter 210, 259–268. Chamley, H., 1989. Clay Sedimentology. Springer, Berlin, pp. 1–623. Chen, Z.Y., Li, J.F., Shen, H., 2001. Yangtze River of China: historical analysis of discharge variability and sediment flux. Geomorphology 41, 77–91 (in Chinese). Chen, T., Wang, H., Zhang, Z.Q., 2003. Clay minerals as indicators of paleoclimate. Acta Petrological Mineralogical 22, 416–420 (in Chinese). Cheng, J., Tang, D.X., Zhang, X.J., 2003. Research on the Holocene climate in the source area of the yellow river by clay mineral. Geoscience 17, 1–5 (in Chinese). Clift, P., Lee, J.I., Clark, M.K., Blusztajn, J., 2002a. Erosional response of South China to arc rifting and monsoonal strengthening: a record from the South China Sea. Marine Geology 184, 207–226. Clift, P.D., Lee, J.I., Eylander, J.B., Joyce, R.J., Layne, G.D., Adler, R.F., Blum, J.D., Turk, F.J., Khan, A.A., 2002b. Nd and Pd isotope variability in the Indus River System: implications for sediment provenance and crustal heterogeneity in the Western Himalaya. Journal of Geophysical Research 114, 91–106. Clift, P.D., Lee, J.L., Hildebrand, P., Shimizu, N., Layne, G.D., Blusztajn, J., Blum, J.D., Garzanti, E., Khan, A.A., 2002c. Nd and Pb isotope variability in the Indus River System: implications for sediment provenance and crustal heterogeneity in the Western Himalaya. Earth and Planetary Science Letters 200, 91–106. Ding, T., Wan, D., Wang, C., Zhang, F., 2004. Silicon isotope compositions of dissolved silicon and suspended matter in the Yangtze River, China. Geochimica et Cosmochimica Acta 68, 205–216. Dou, Y.G., Yang, S.Y., Liu, Z.X., Clift, P.D., Hua, Y., Serge, B., Shi, X.F., 2010. Clay mineral evolution in the central Okinawa Trough since 28 ka: implication for sediment provenance and paleoenvironmental change. Palaeogeography, Palaeoclimatology, Palaeoecology 288, 108–117. Ehrmann, W., 1998. Implications of late Eocene to early Miocene clay mineral assemblages in McMurdo Sound (Ross Sea, Antarctica) on paleoclimate and ice dynamics. Palaeogeography, Palaeoclimatology, Palaeoecology 139, 213–231.

Esquevin, J., 1969. Influence de la composition chimique des illites surcristallinite. Bull Centre Rech Rau-SNPA 3, 147–153. Fan, D.J., Yang, Z.S., Mao, D., 2001. Clay minerals and geochemistry of the sediments from the Yangtze and yellow rivers. Marine Geology & Quaternary Geology 21, 7–12 (in Chinese). Fang, X.S., Shi, X.F., Wang, G.Q., 2007. Distributions of clay minerals in surface sediments from the Changjiang River Subaqueous Delta and their affecting factors. Advances in Marine Science 25, 419–427 (in Chinese). Franz, V.H., Fahle, M., Bülthoff, H.H., Gegenfurtner, K.R., 2001. Effects of visual illusions on grasping. J Exp Psychol Hum Percept Perform 27, 1124– 1144. Gingele, F.X., Deckker, P.D., Hillenbrand, C.D., 2001. Clay mineral distribution in surface sediments between Indonesia and NW Australia—source and transport by ocean currents. Marine Geology 179, 135–146. Kessarkar, P.M., Rao, V.P., Ahmad, S.M., Babu, G.A., 2003. Clay minerals and Sr–Nd isotopes of the sediments along the western margin of India and their implication for sediment provenance. Marine Geology 202, 55–69. Kong, X.L., Xiang, H.G., 2003. A discussion on the study of clay minerals from ocean sediments and global change. Transactions of Oceanology and Limnology, 23– 26. Krumm, S., Buggisch, W., 1991. Sample preparation effects on illite crystallinity measurements: grain size gradation and particle orientation. Journal of Metamorphic Geology 9, 671–677. Kuhlmann, G., de Boer, Poppe L., Pedersen, Rolf B., Wong, Theo E., 2004. Provenance of Pliocene sediments and paleoenvironmental changes in the southern North Sea region using Samariun–Neodymium (Sm/Nd) provenance ages and clay mineralogy. Sedimentary Geology 171, 205–226. Lan, X.H., Wang, H.X., Li, R.H., Lin, Z.H., Zhang, Z.X., 2007. Major elements composition and provenance analysis in the sediments of the south yellow sea. Earth Science Frontiers 14, 197–203 (in Chinese). Laura, I.Net., Susana, A.M., Limarino, C.O., 2002. Source rock and environmental control on clay mineral associations, Lower Section of Paganzo Group (Carboniferous), Northwest Argentina. Sedimentary Geology 152, 183– 199. Lim, D.I., Jung, H.S., Choi, J.Y., Yang, S., Ahn, K.S., 2006. Geochemical compositions of river and shelf sediments in the Yellow Sea: grain-size normalization and sediment provenance. Continental Shelf Research 26, 15–24. Liu, Z.F., Trentesaux, A., Clemens, S.C., 2003a. Clay mineral assemblages in the northern South China Sea: implications for East Asian monsoon evolution over the past 2 million years. Marine Geology 201, 133–146. Liu, Z.F., Trentesaux, A., Clemens, S.C., 2003b. Clay minerals recording in Quaternary of ODP1146 station in north sloping South China Sea: ocean current transportetions and evolvement of East Asia monsoon. Science in China (D) 33 (3), 271–280. Liu, Z.F., Colin, C., Trentesaux, A., Blamart, D., 2004. Clay mineral records of East Asian monsoon evolution during Late Quaternary in the southern South China Sea. Science in China (Ser. D) 34, 272–279. Liu, Z.F., Colin, C., Wei, H., Chen, Z., Trentesaux, A., Chen, J.F., 2007. Clay minerals in surface sediment s of the Pearl River drainage basin and t heir contribution to the South China Sea. Chinese Science Bulletin 52, 448–456. Liu, Z.F., Tuo, S.T., Colin, C., Liu, J.T., Huang, C.Y., Selvaraj, K., Arthur Chen, C.T., Zhao, Y.L., Siringan, F.P., Boulay, S., Chen, Z., 2008. Detrital fine-frained sediment contribution from Taiwan to the northern South China Sea and its relation to regional ocean circulation. Marine Geology 255, 149–155. Liu, S., Zhang, W.G., He, Q., Li, D.J., Liu, H., Yu, L.Z., 2010. Magnetic properties of East China Sea shelf sediments off the Yangtze Estuary: influence of provenance and Particle size. Geomorphology 119, 212–220. Long, H., Wang, C.H., Liu, Y.P., 2007. Application of clay minerals in paleoenvironment research. Journal of Salt Lake Research 15, 21–29 (in Chinese). Lu, C.X., 1997. Clay minerals as indicators of paleoenvironment. Journal of Desert Research 17, 456–460 (in Chinese). Moral Cardona, J.P., Gutiérrez Mas, J.M., Sánchez Bellón, A., Domínguez-Bella, S., Martínez López., J., 2005. Surface textures of heavy-mineral grains: a new contribution to provenance studies. Sedimentary Geology 174, 223–235. Moral-Cardona, J.P., Sánchez Bellón, A., López-Aguayo, F., Caballero, M.A., 1996. The analysis of quartz grain surface features as a complementary method for studying their provenance: the Guadalete River Basin (Cádiz, SW Spain). Sedimentary Geology 106, 155–164. Pan, G.T., Cheng, Z.L., Li, X.Z., 1997. Geological-Tectonic Evolution in the Eastern Tethys. Geological Publishing House, Beijing, 218pp (in Chinese). Petschick, R., Kuhn, G., Gingele, F., 1996. Clay mineral distribution in surface sediments of the South Atlantic: sources, transport, and relation to oceanography. Marine Geology 130, 203–229. Qin, J.H., Huh, Y.S., Edmond, J.M., 2006. Chemical and physical weathering in the Min Jiang, a headwater tributary of the Yangtze River. Chemical Geology 227, 53–69 (in Chinese). Raman, C.V., Rao, G.K., Reddy, K.S.N., Ramesh, M.V., 1995. Clay mineral distributions in the continental shelf sediments between the Ganges mouths and Madras, east coast of India. Continental Shelf Research 15, 1773–1793. Shao, J.Q., Yang, S.Y., Li, C., 2012. Chemical indeces (CIA and WIP) as proxies for integrated chemical weathering in China: Inferences from analysis of fluvial sediments. Sedimentary Geology 265–266, 110–120. Singh, P., 2010. Geochemistry and provenance of stream sediments of the Ganga River and its major tributaries in the Himalayan region, India. Chemical Geology 268, 220–236.

M. He et al. / Journal of Asian Earth Sciences 69 (2013) 60–69 Suresh, N., Ghosh, S.K., Kumar, R., Sangode, S.J., 2004. Clay mineral distribution patterns in late Neogene fluvial sediments of the Subathu sub-basin, central sector of Himalayan foreland basin: implication for provenance and climate. Sedimentary Geology 163, 265–278. Thiry, M., 2000. Palaeoclimatic interpretation of clay minerals in marine deposits: an outlook from the continental origin. Earth-Science Reviews 49, 201– 221. Wan, S.M., Li, A.C., Xu, K.H., 2008. Clay minerals an Asian monsoon record of Miocene in the northern part of South China Sea. Earth Sciente-Journal of China University of Geosciences 33, 289–300 (in Chinese). Wang, Z.B., Yang, S.Y., Li, P., 2006. Detrital mineral compositions of the Changjiang River sediments and their tracing implications. Acta Sedimentologica Sinica 24, 570–578 (in Chinese). Wang, Z.B., Yang, S.Y., Wang, R.C., 2007. Magnetite compositions of Changjiang River sediments and their tracing implications. Geochimica (Beijing) 36, 176– 184 (in Chinese). Wu, Weihua, Xu, Shijun, Lu, Huayu, Yang, Jeidong, Yin, Hongwei, Liu, Wen, 2011. Mineralogy, major and trace element geochemistry of riverbed sediments in the headwaters of the Yangtze, Tongtian River and Jinsha River. Journal of Asian Earth Sciences 40, 611–621. Wu, Y.Y., Chen, Z.Y., Wang, Z.H., 2005. Distribution of clay minerals in the Yangtze Delta Plain and its paleoevnironmental implicaion. Journal of East China Normal University 1, 92–98 (in Chinese). Wu, Y., Zhang, J., Liu, S.M., 2007. Sources and distribution of carbon within the Yangtze River system. Estuarine. Coastal and Shelf Science 71, 13–25 (in Chinese).

69

Yang, Z.S., 1988. Mineralogical assemblages and chemical characteristics of clays from sediments of the Huanghe, Changjiang, Zhujiang Rivers and their relationship to the climate environment in their sediment source areas. Oceanologia Et Limnologia Sinica 19, 336–346 (in Chinese). Yang, S.Y., Jung, H.S., Li, C.X., 2004. Two unique weathering regimes in the Changjiang and Huanghe drainage basins: geochemical evidence from river sediments. Sedimentary Geology 164, 19–34. Yang, S.Y., Li, C.X., Yokoyama, Kazumi, 2006. Elemental compositions and monazite age patterns of core sediments in the Changjiang Delta: implications for sediment provenance and development history of the Changjiang River. Earth and Planetary Science Letters 245, 762–776. Yang, S.Y., Jiang, S.Y., Ling, H.F., Xia, X.P., Sun, M., Wang, D.J., 2007. Sr–Nd isotopic composition of Changjiang River sediments: implications for tracing sediment sources. Science in China (D) 37, 682–690. Yang, S.Y., Wang, Z.B., Guo, Y., 2009. Heavy mineral compositions of the Changjiang (Yangtze River) sediments and their provenance-traing implication. Journal of Asian Earth Sciences 35, 56–64. Zhang, N.X., 1992. Clay minerals and weathering. Building Geological Magazine 6, 1–6 (in Chinese). Zhang, H.F., Jin, L.L., Zhang, L., Nigel, H., Zhou, L., Hu, S.H., Zhang, B.R., 2005. Geochemical and Pb–Sr–Nd isotopic compositions of granitoids from western Qinling belt: constrains on basement nature and tectonic affinity. Science in China (Series D) 35, 914–924. Zhou, X.J., Gao, S., Jia, J.J., 2003. Preliminary evaluation of the stability of Changjiang clay minerals as fingerprints for material source tracing. Oceanologia Et Limnologia Sinica 34, 683–692 (in Chinese).