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Article

Petrology of Lancang (Upper Mekong) River Sand

by
Daxin Fang
1,2,
Xiumian Hu
1,*,
Eduardo Garzanti
3,
Wen Lai
4 and
Fengting Chen
1
1
School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
2
State Key Laboratory of Tibetan Plateau System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
3
Department of Earth and Environmental Sciences, University of Milano-Bicocca, 20126 Milan, Italy
4
School of Geography and Environmental Engineering, Gannan Normal University, Ganzhou 341000, China
*
Author to whom correspondence should be addressed.
Geosciences 2025, 15(11), 415; https://doi.org/10.3390/geosciences15110415 (registering DOI)
Submission received: 15 July 2025 / Revised: 26 October 2025 / Accepted: 28 October 2025 / Published: 31 October 2025
(This article belongs to the Section Sedimentology, Stratigraphy and Palaeontology)
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Abstract

The texture and composition of river sediments are key to understanding the characteristics of source rocks, chemical weathering in the source area, physical modifications during transport, and human impacts within watersheds. This study analyzes 47 very fine to coarse size sands from the Lancang (Upper Mekong) River in China to monitor compositional variations and assesses the contribution of different geological units to trunk-river sediments. Lancang River sands are mostly feldspatho-quartzo-lithic in composition, with quartz content increasing downstream at the expense of lithic fragments (especially of carbonate lithics). Sand is mostly generated from the Lincang and Baoshan blocks, with subordinate contributions from the Simao and Changdu blocks. This study provides new insights into erosional and depositional processes in the Lancang River and emphasizes the impact of human activities on river sediment transport.

1. Introduction

River sediments can be used to trace erosion patterns across source areas and short-term to long-term watershed evolution under the impact of tectonics, climate, and human activities [1,2,3,4]. By analyzing modern river sediments, we can examine physical and chemical processes within well-constrained geological, geomorphological, and climatic settings, helping us to better understand how sediments are generated, transported, and ultimately deposited [5].
The surface uplift of the Himalayan Mountains and Tibetan Plateau resulted from the continuing collision between the Indian and Asian plates [6,7] and initiated the formation of large Asian rivers, including the Mekong. The Lancang headwaters of the Mekong River contribute ~50% of the total sediment supplied annually to the South China Sea, amounting to 160 million tons [8,9]. Located in a tectonically active cold–humid climatic zone, the Lancang catchment presents excellent conditions for studying sediment provenance and recycling [10,11]. Previous geochronological and geochemical studies of Lancang River sediments revealed predominantly felsic source rocks exposed in the Northern Qiangtang and Yidun blocks [12,13], but without adequate consideration of sediment recycling and quantitative assessment of sediment contribution from different geological units.
This study analyzes the textural and compositional characteristics of river sands and their variations downstream the Lancang River in China, describes the mineralogical signatures of modern sand generated in different geological domains, and estimates sediment yield and contribution rates from different tributary catchments, distinguishing between first-cycle and recycled sediments.

2. The Lancang Basin

The Lancang River (Figure 1) originates from Mount Jifu in Zaduo County, Qinghai Province, at an elevation of 5200 m a.s.l. Within China’s territory, the mainstem is 2129 km long with a drainage area of 167,487 km2 [14]. In the headwaters, runoff ranges from 200 to 300 mm, gradually increasing as the river enters Yunnan Province. The Lancang River’s annual discharge has remained relatively stable through time, although with uneven distribution during the year. Flow is concentrated between May and October and minimal in January and February [15].
The Lancang River (Figure 1C), flowing from the eastern margin of the Tibetan Plateau, runs nearly parallel to the Lancang suture zone [16], a region that has remained tectonically active since the late Cenozoic [17]. The river drains different geological domains (Changdu, Simao, Baoshan, and Lincang blocks [18]; Figure 1B), and its sediments thus represent a mixture of detritus shed from various sources characterized by distinct endmember compositional signatures.

2.1. Changdu Block

The Changdu block mostly consists of Triassic sedimentary rocks. Upper Paleozoic shallow marine carbonate and clastic rocks are overlain by Lower to Middle Triassic continental to transitional volcaniclastic rocks, and in turn by Upper Triassic fluvio-deltaic clastic rocks and marine limestones. Magmatic activity took place during the Triassic [19,20], and the stratigraphic succession is capped by Jurassic and Cretaceous continental red beds.

2.2. Simao Block

The Simao block is dominated by Mesozoic–Cenozoic mudrocks. Older strata, exposed on both eastern and western sides, include mainly deep-water turbidites in the east, followed by Upper Permian volcaniclastic deposits in the east. Continental to shallow marine feldspar-rich sandstones, mudrocks, and carbonates are overlain by Upper Carboniferous–Lower Permian volcano-sedimentary sequences in the west [21].

2.3. Baoshan Block

The Baoshan block mainly consists of Upper Paleozoic carbonates and sandstones [21,22,23]. Cambrian–Ordovician granites dated between 502 and 444 Ma and minor volcanic rocks dated as 499–486 Ma occur; younger granites were also intruded in Upper Paleozoic to Cenozoic strata [24,25,26,27,28,29].

2.4. Lincang Block

The Lincang block mainly consists of quartz-schists, mica-schists, and meta-granulites in the west [30,31,32]. Ordovician mafic-intermediate metavolcanic rocks (463–454 Ma) and granites (458.5 ± 3.0 Ma) [33,34,35] also occur. Devonian–Carboniferous siliciclastic strata are overlain by Permian mudrocks and limestones [21]. The Lincang plutonic belt, bracketed between the western side of the block and the Lancang mélange belt [23], mostly consists of biotite monzogranite dated as 230–200 Ma [36] and locally metamorphosed to gneiss [37,38].

3. Methods

A total of 47 sand samples were collected from active river bars in 2021 and 2023 (24 along the mainstem at 50–100 km intervals, and 23 from major tributaries). Detailed information on sampling locations and grain-size data is provided in Table 1. Grain-size analysis was conducted using a Mastersize 2000 laser particle size analyzer at the School of Geography and Ocean Sciences, Nanjing University. Grain-size parameters were calculated following Folk and Ward [39]; φ values were calculated as φ = −log2D (where D is grain size in mm).
A quartered fraction of each sample was impregnated with Araldite epoxy and cut into a standard thin section. Petrographic analyses were carried out by counting 400–500 grains per section under the microscope according to the Gazzi–Dickinson method (inherent counting error ~5% at 1σ) [40]. The classification scheme for detrital components was based on the relative proportions of the three main constituents: quartz (Q), feldspar (F), and lithic fragments (L) [41]. Polycrystalline quartz was counted as quartz; sedimentary lithics include chert and carbonate [42].
The relative sediment contributions from different tributaries and different geological units were calculated with forward mixing modeling based on petrographic data [43,44]. The forward mixing model computes compositional data (as row vectors, with columns representing variables) as non-negative linear combinations between a fixed endmember composition matrix (rows representing observations, columns representing variables) and coefficient row vectors representing the proportional contributions of each endmember to the observations [43]. We applied a filter to our data to incorporate the uncertainties of our assumptions and address the fact that natural geological complexity often diverges from theoretical models. We only used modeled compositions if the statistical distance was within 110% of the minimum value calculated using both Aitchison and Euclidean methods for each sample. Our final provenance budget and its associated uncertainties were then derived from the standard deviation of this selected set of solutions. The simulation requires first determining the endmember compositions of different tributaries and geological units, then calculating several simulated compositions by assigning different proportions of these sources [43,45]. To enhance simulation accuracy, multiple representative samples are typically averaged to better define the composition of endmember components.

4. Results

4.1. Texture of Lancang River Sands

The studied sand samples (7 very fine, 26 fine, 13 medium, and 1 coarse; Figure 2A,B) are mainly very fine to fine in the upper reaches, medium in the middle reaches, and very fine in the lower reaches, but with great variability and no systematic downstream fining (Figure 3). The sorting coefficient ranges from 0.5 to 3.5; only 4 samples are well sorted, 30 are poorly sorted, and 14 are very poorly sorted (Figure 2C). Skewness ranges from −0.29 to 0.72; only 2 samples show negative skewness, 2 are nearly symmetrical, 6 are positively skewed, and 37 are strongly positively skewed (Figure 2D).
Finer samples in the upper reaches have poor sorting and positive skewness, whereas coarser samples in the middle reaches have extremely positive skewness. Textural variability appears to be influenced by human impacts (e.g., hydropower stations, riverside road development, steep slope cultivations [46,47,48,49,50]). Natural downstream fining and selective transport make minor contributions to the grain size distribution. Eight major dams (Huangdeng, Miaowei, Gongguoqiao, Xiaowan, Manwan, Dachaoshan, Nuozhadu, and Jinghong) were built in the middle and lower reaches (Figure 1C). The proximity of reservoir locations to the site of coarser-grain samples with extremely positive skewness suggests that cascade dams induce sediment coarsening. Because river bedload is efficiently trapped in artificial reservoirs, the enhanced erosion power of clear water downstream of dams leads to erosion and resuspension of older channel and bank deposits [51,52,53], explaining the coarser size and extremely positive skewness of samples collected shortly downstream of dams.

4.2. Petrography of Lancang River Sands

Lancang River sands are mostly feldspatho-quartzo-lithic (Figure 4). Quartz is mainly monocrystalline, feldspars are mostly potassic, and rock fragments are predominantly sedimentary with only minor volcanic and metamorphic types (Figure 5 and Table 2).
The Lancang mainstem is here divided into upper reaches of Changdu (5 samples), middle reaches upstream of Gongguoqiao Dam (14 samples), and lower reaches downstream (5 samples). In the upper reaches, samples are quartzo-lithic and feldspatho-quartzo-lithic (average composition Q25F10L65, Ls88Lv10Lm2, Lsm10Lsc39Lss51). In the middle reaches, samples are mainly feldspatho-quartzo-lithic and subordinately quartzo-feldspatho-lithic and quartzo-lithic (average composition Q23F13L64, Ls78Lv18Lm4, Lsm10Lsc20Lss70). In the lower reaches, samples are feldspatho-litho-quartzose and feldspatho-quartzo-lithic (average composition Q43F15L42, Ls79Lv13Lm8, Lsm11Lsc2Lss87). Carbonate grains thus markedly decrease downstream, whereas quartz, feldspar, and siltstone rock fragments relatively increase.
Tributary samples are classified into four groups (Changdu, Simao, Baoshan 1 and 2, Lincang 1 and 2). The 15 tributaries draining the Changdu block (Changdu group) carry mainly quartzo-lithic and subordinately litho-quartzose, feldspatho-litho-quartzose, and feldspatho-quartzo-lithic sand (average composition Q26F7L67, Ls82Lv13Lm5, Lsm12Lsc23Lss65). The two tributaries draining the Lanping–Simao Basin (Simao group) carry feldspatho-quartzo-lithic and quartzo-feldspatho-lithic sand (average composition Q19F21L60, Ls95Lv4Lm1, Lsm31Lsc10Lss59). The two tributaries draining the Baoshan block carry litho-feldspatho-quartzose (Q56F26L18, Ls79Lv7Lm14, Lsm6Lsc13Lss81; Baoshan 1 tributary) or feldspatho-quartzo-lithic sand (Q23F23L54, Ls85Lv13Lm2, Lsm12Lsc32Lss56; Baoshan 2 tributary). Tributaries draining the Lincang block carry litho-feldspatho-quartzose (average composition Q54F21L25, Ls84Lv14Lm2, Lsm31Lsc1Lss68; Lincang 1 tributaries mainly draining the Lincang plutonic belt) or feldspatho-litho-quartzose sand (average composition Q24F19L57, Ls91Lv4Lm5, Lsm28Lsc6Lss66; Lincang 2 tributary).
Quartz is prevalent and siltstone lithics least abundant in Baoshan 1 and Lincang 1 tributaries, feldspar least abundant in Changdu tributaries, and volcanic and carbonate grains more common in Changdu and Baoshan 2 tributaries. Compositional variability along the Lancang mainstem is illustrated in Figure 6.

5. Discussion

5.1. Provenance Budget Based on Petrographic Data

Forward mixing calculations indicate that final Lancang sand upstream of the China border originates mainly from the Lincang block (52 ± 20%; 6 ± 6% for Lincang 1 and 46 ± 15% for Lincang 2), subordinately from the Baoshan block (32 ± 9%; 2 ± 2% for Baoshan1 and 30 ± 9% for Baoshan 2), and in minor part from the Changdu and Simao blocks (8 ± 7% each) (Figure 7).
Sand is calculated to be overwhelmingly (92 ± 8%) recycled from sedimentary rocks drained by Changdu, Simao, Baoshan 2, and Lincang 2 tributaries, whereas first-cycle contribution from granitic sources drained by Lincang1 and Baoshan 1 tributaries is assessed to be only 8 ± 8%. Taking into account the basin areas occupied by the Changdu (85,335 km2, 53% of total area), Simao (15,660 km2, 10%), Baoshan (13,546 km2, 8%), and Lincang blocks (45,549 km2, 28%), the highest sediment yields are assessed for the Baoshan and Lincang blocks (Figure 7). Sediment supply results are higher for tributaries in the upper reaches than for tributaries in the middle reaches, rising again for tributaries in the lower reaches (Figure 7).
Our estimates differ from previous indications based on U-Pb zircon dating and geochemical research, suggesting that Lancang River sand mainly originates from the Northern Qiangtang block [11,12]. To check for this discrepancy, we analyzed the available hydrological data from five gauging stations (data shown in Supplementary Materials Table S1). The recorded average annual discharges and sediment loads are 30.0 km3 and 22.7 × 106 t for the Gongguoqiao station, 37.1 km3 and 42.5 × 106 t for the Gajiu station, 28.2 km3 and 22.7 × 106 t for the Jiuzhou station, 22.8 km3 and 22.7 × 106 t for the Liutongjiang station, and 56.8 km3 and 82.5 × 106 t for the Yunxianghong station. Based on these data, 22.7 × 106 t, 0.004 × 106 t, 19.2 × 106 t, and 40.1 × 106 t of sediment are produced in the four river tracts delimited by dams, with corresponding annual sediment yields of 295 t/km2, 0.2 t/km2, 1097 t/km2, and 1173 t/km2 (Figure 8). The resulting higher sediment yields from the lower reaches are consistent with the outcome of forward mixing calculations.

5.2. First-Cycle Versus Recycled River Sand

Sedimentary rocks are the primary source of Lancang River sediments. This is testified by the abundance of shale, siltstone, sandstone, and carbonate rock fragments in most samples (e.g., 21LB006, 21LB012, and 21LB013), whereas only a few (e.g., 21LB011, 21LB014, and 21LB015) contain a significant amount of first-cycle detritus, including minor igneous and metamorphic rock fragments and more biotite and heavy minerals. Most Lancang River sand is thus recycled. Regarding optical characteristics, first-cycle samples exhibit quartz and feldspar grains with clear boundaries and smooth surfaces. In recycled samples, quartz grains are instead commonly well-rounded and show turbid surfaces and concave outlines, and feldspars appear notably altered. All samples are, however, mixed, largely first-cycle samples also containing some sedimentary rock fragments and largely recycled samples including volcanic or plutonic grains as well as hornblende, pyroxene, and epidote.

5.3. Durability of Carbonate Grains

Carbonate rock fragments (mostly sparry to bioclastic limestone) are most abundant in the upper reaches (Figure 4), where they represent 50–60% of sedimentary rock fragments (Figure 6C). This proportion decreases to 10–30% in the middle reaches, where carbonate particles are mostly micritic limestone with minor sparite locally containing quartz-rich silt, and becomes very low in the lower reaches, where mainly micritic lithics occur. Such a downstream decrease in carbonate grains primarily reflects provenance, carbonate rocks being mostly extensively exposed in the Changdu block. The presence of large reservoirs prevents the transportation of these grains downstream, where carbonate exposures are sparse. However, cathodoluminescence analysis could help distinguish different types of carbonate fragments and assess their degree of abrasion and roundness, providing valuable insights into source lithologies and transport pathways [54,55].
In large rivers draining humid regions and characterized by high discharge and waters with high pCO2 levels, such as the Brahmaputra, the Congo, or the Pearl River, carbonate grains may be efficiently dissolved [56,57,58,59,60,61]. Selective mechanical breakdown of carbonate grains may also occur (Figure 4 in [59]). These effects are, however, difficult to separate from the effect of downstream dilution by carbonate-poor tributary sands, enhanced in highly man-regulated river systems by efficient sediment sequestration in reservoirs upstream. The natural controls of compositional change between different downstream tracts of the heavily dam-segmented course of the Lancang River are consequently hard to evaluate.

6. Conclusions

Sands carried by the Lancang (Upper Mekong) River are mainly feldspatho-quartzo-lithic with dominant sedimentary rock fragments. Quartz content increases downstream at the expense of lithic fragments. Carbonate rock fragments decrease markedly, whereas siltstone/sandstone fragments relatively increase. Sand is thus mostly recycled from sedimentary rocks, with minor contributions from igneous rocks. Based on forward modeling calculations, sand is mostly derived from the Lancang (52 ± 20%) and Baoshan blocks (32 ± 9%), with minor contributions from the Simao and Changdu blocks (~8% each).
Most textural and compositional variability along the Lancang River was mainly induced by anthropogenic impact. Eight major dams were built in the middle and lower reaches, leading to extreme segmentation of sediment fluxes and thus preventing us from separately identifying and evaluating the effect of natural processes, such as the potential selective chemical or physical breakdown of more labile grains, including carbonate and shale rock fragments. To evaluate erosion rates, we thus resorted to the analysis of the available hydrological data from five gauging stations, which allowed us to constrain provenance budgets and calculate annual sediment yields increasing from ~300 t/km2 in the upper reaches to >1000 t/km2 in the lower reaches.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/geosciences15110415/s1, Table S1: Multiyear flow table and annual sediment transport.

Author Contributions

Conceptualization, X.H.; methodology, X.H.; validation, D.F., X.H. and W.L.; formal analysis, D.F., X.H., W.L. and F.C.; investigation, D.F. and X.H.; resources, X.H. and D.F.; data curation, D.F. and X.H.; writing—original draft, D.F., X.H., and E.G.; visualization, X.H. and D.F.; Supervision, X.H.; project administration, X.H. All authors have read and agreed to the published version of the manuscript.

Funding

This research was financially supported by the Second Tibetan Plateau Scientific Expedition Research Program (STEP, Grant No. 2019QZKK020402) and GeoX’ Interdisciplinary Project of Frontiers Science Center for Critical Earth Material Cycling, Grant No. 20250102.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding authors.

Acknowledgments

The authors are grateful to Wendong Liang, Xiaolong Dong, and Keran Li for their assistance with sample collection and express their sincere gratitude to the editors and the anonymous reviewers for their valuable comments and suggestions.

Conflicts of Interest

The authors declare no conflicts of interest.

Glossary

BlockTectono-stratigraphic terranes accreted to an orogenic belt and characterized by a unique assemblage of lithologies, stratigraphic succession, and tectonic evolution.
First-cycle sedimentSediment typically enriched in feldspars, volcanic and/or metamorphic rock fragments, and heavy minerals derived directly from igneous rocks and/or metamorphic basement.
Recycled sedimentSediment typically enriched in durable minerals (quartz, zircon, tourmaline, rutile) derived from the erosion of pre-existing lithified sedimentary rocks or loose siliciclastic deposits.

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Figure 1. The Lancang River basin (A). (B) Geological map (modified from [13]). (C) Drainage map. Red box is Lancang River basin’s position in tectonic framework.
Figure 1. The Lancang River basin (A). (B) Geological map (modified from [13]). (C) Drainage map. Red box is Lancang River basin’s position in tectonic framework.
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Figure 2. Frequency distribution of grain-size parameters: (A) D50: median diameter; (B) Dmean: mean diameter; (C) σ: sorting coefficient; (D) SK: skewness.
Figure 2. Frequency distribution of grain-size parameters: (A) D50: median diameter; (B) Dmean: mean diameter; (C) σ: sorting coefficient; (D) SK: skewness.
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Figure 3. Variability in mean grain size of the studied sand samples along the Lancang River. Blue dots connected by value curve are mainstream samples, and black dots are tributary samples connected with dashed lines to their respective confluence points on the main stream.
Figure 3. Variability in mean grain size of the studied sand samples along the Lancang River. Blue dots connected by value curve are mainstream samples, and black dots are tributary samples connected with dashed lines to their respective confluence points on the main stream.
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Figure 4. Sandstone petrography. (A) Q: quartz, F: feldspar, L: lithic plot (compositional fields after [41,42]); (B) Lm: metamorphic, Lv: volcanic, Ls: sedimentary lithic plot; (C) Lss: shale, Lsc: carbonate; Lss: sand(silt)stone lithic plot.
Figure 4. Sandstone petrography. (A) Q: quartz, F: feldspar, L: lithic plot (compositional fields after [41,42]); (B) Lm: metamorphic, Lv: volcanic, Ls: sedimentary lithic plot; (C) Lss: shale, Lsc: carbonate; Lss: sand(silt)stone lithic plot.
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Figure 5. Petrography of Lancang River sands. Q: quartz, K: K-feldspar, P: plagioclase; L: lithics (Lv: volcanic, Lm: metamorphic, Lss: siltstone, Lsc: carbonate, Lsm: shale), B: biotite, Pyr: pyroxene.
Figure 5. Petrography of Lancang River sands. Q: quartz, K: K-feldspar, P: plagioclase; L: lithics (Lv: volcanic, Lm: metamorphic, Lss: siltstone, Lsc: carbonate, Lsm: shale), B: biotite, Pyr: pyroxene.
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Figure 6. Compositional variability along the Lancang mainstem. (A) QFL percentages, (B) lithic fragments percentages, (C) sedimentary rock fragments percentages. Q: quartz, F: feldspar, L: lithics (Lm: metamorphic, Lv: volcanic, Ls: sedimentary; Lss: shale, Lsc: carbonate, Lss: siltstone). Mainstem samples are connected with a smooth curve, tributary samples with dashed lines to their respective confluences with the mainstem.
Figure 6. Compositional variability along the Lancang mainstem. (A) QFL percentages, (B) lithic fragments percentages, (C) sedimentary rock fragments percentages. Q: quartz, F: feldspar, L: lithics (Lm: metamorphic, Lv: volcanic, Ls: sedimentary; Lss: shale, Lsc: carbonate, Lss: siltstone). Mainstem samples are connected with a smooth curve, tributary samples with dashed lines to their respective confluences with the mainstem.
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Figure 7. Sediment yields from different geological units in the Lancang catchment.
Figure 7. Sediment yields from different geological units in the Lancang catchment.
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Figure 8. Sediment yield in four tracts of the Lancang catchment based on hydrological data (data from hydrological yearbook of Sanjiang catchment from 1958 to 1987 (Table S1)). River course in blue.
Figure 8. Sediment yield in four tracts of the Lancang catchment based on hydrological data (data from hydrological yearbook of Sanjiang catchment from 1958 to 1987 (Table S1)). River course in blue.
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Table 1. Sampling sites and grain-size parameters.
Table 1. Sampling sites and grain-size parameters.
Sample IDDownstream Distance/kmLatitude (N)Longitude (E)LocationRiverD10/φD50/φD90/φDmean/φσSK
21L006021.85053101.01257Manjucun, JinghongLower Lancang River1.736 3.028 7.117 3.647 2.053 0.513
21L00738.822.01052100.80678Xishuangbanna BridgeLower Lancang River0.069 0.803 1.773 0.831 1.042 0.342
21L008125.922.50944100.57599Simaogang, PuerLower Lancang River0.413 1.413 3.203 1.487 1.307 0.345
21L009338.323.91246100.41335Jiezizhaicun, Yuanxian Lower Lancang River1.528 2.368 3.308 2.385 0.714 0.089
21L011442.524.60885100.46058Manwan, YunxianLower Lancang River0.299 1.453 5.297 1.911 1.788 0.493
21L013763.726.2586699.1335Dabizancun, LanpingMiddle Lancang River1.213 2.506 7.204 3.252 2.213 0.549
21L014793.526.4702299.14607Yingpanqiao, LaningMiddle Lancang River2.061 4.791 8.777 5.100 2.615 0.190
21L01687227.0726199.17453Weideng, DiqingMiddle Lancang River2.574 3.779 7.473 4.222 1.810 0.480
21L017914.627.3666399.0851Baijixun, DiqingMiddle Lancang River0.505 1.576 5.052 1.698 1.583 0.400
21L018963.727.7114999.04798Yezhi, DiqingMiddle Lancang River0.805 1.643 4.407 1.703 1.362 0.401
21L019974.927.7915199.03116Bujiecun, DiqingMiddle Lancang River0.295 1.118 4.042 1.182 1.428 0.417
21L0201047.728.3053498.87471DeqinMiddle Lancang River0.415 1.454 2.815 1.507 1.050 0.221
21L022-11160.829.0971498.61262Quzika, MangkangMiddle Lancang River0.065 1.282 2.823 1.337 1.217 0.207
21L0221165.329.1323598.63051Lajiuxicun, MangkangMiddle Lancang River0.978 1.927 3.383 1.992 1.344 0.364
21L0231232.929.6256198.35249Rumei, MangkangMiddle Lancang River−0.085 1.047 2.881 1.131 1.576 0.361
21L0251386.430.6065597.52622Kagongcun, ChayaUpper Lancang River1.534 2.566 5.804 2.669 1.480 0.385
21L0261433.930.940297.36719Tigongcun, ChangduUpper Lancang River0.589 1.461 2.808 1.516 1.429 0.397
21L0271461.131.0841397.203Botuocun, ChangduUpper Lancang River1.668 2.427 3.378 2.456 0.936 0.304
21L0281514.431.4637797.19023Gaoatongcun, ChangduUpper Lancang River1.205 2.137 7.105 2.813 2.012 0.636
23L291561.131.7871197.00243Jiarongcun, ChangduUpper Lancang River1.758 3.057 5.394 3.223 1.557 0.333
23L301616.832.0684396.76559Bariniangcun, NangqianUpper Lancang River1.541 2.133 2.789 2.143 0.490 0.062
23L311663.532.2728196.46386Zhangjicecun, NangqianUpper Lancang River2.330 3.517 6.943 3.798 1.694 0.434
23L331805.232.8449695.552Duonacun, NangqianUpper Lancang River2.059 2.856 4.145 2.909 1.175 0.374
23L341867.532.9412395.138Suijia, ZaduoUpper Lancang River0.828 2.051 4.998 2.316 1.751 0.430
21LB01533.421.99248100.83041MingjiangyuanLiusha River0.627 1.880 5.298 2.315 1.781 0.452
21LB013139.122.57872100.53739Nuozhadu, PuerZhong River1.081 2.254 7.800 3.422 2.593 0.651
21LB012337.923.91212100.42524Xiushancun, PuerGali River2.508 3.960 7.835 4.463 2.018 0.441
21LB01145524.49335100.30111Yunxian, LincangLuozha River2.276 3.600 6.248 3.852 1.546 0.328
21LB014197.822.64531100.11734Lancang, PuerHei River2.360 3.706 6.452 3.992 1.585 0.336
21LB006639.825.4409499.28604Wayao, YunlongWayao River0.675 2.203 4.155 2.233 1.555 0.209
21LB009580.125.0866799.75802Yongping, DaliYongping River2.804 4.315 8.367 4.902 2.139 0.452
21LB00767325.6254799.35982YunlongPijiang River2.224 3.240 7.321 3.750 1.806 0.558
21LB005863.626.9809399.21461Biyuhexiacun, LanpingTongdian River−0.059 1.212 4.476 1.609 1.953 0.477
21LB004913.327.3523699.0996Baiji, WeixiYongchun River1.171 2.240 5.380 2.542 1.588 0.460
21LB003921.827.4030899.04969Baijixun, WeixiLaochang River0.362 1.688 6.861 2.683 2.448 0.580
21LB002969.627.7502399.04312Xiacun, WeixiLancang River0.680 2.045 5.648 2.230 1.758 0.365
21LB0221389.130.619897.51119Kagongxiang, ChayaSequ River0.089 1.549 3.658 1.655 1.667 0.287
21LB0231397.730.6364597.49381KagongxiangXiqu River0.474 5.835 9.317 5.090 3.463 −0.214
21LB0261476.731.1699397.10522Shagongcun, ChangduAnngqu River1.509 2.289 3.231 2.313 0.935 0.287
21LB021123529.643798.35329Duibacun, MangkangRongqu River0.295 1.339 3.113 1.430 1.472 0.374
21LB0241410.130.6589297.57458Yanduosi, ChayaMaiqu River1.407 3.119 8.597 4.172 2.798 0.527
21LB0251520.131.5043197.21045Sexiongkacun, ChayaRequ River0.642 1.627 7.883 3.016 2.749 0.723
23LB311585.531.9689396.94544Gaiqu Bridge, ChangduZiqu River1.499 2.342 4.986 2.405 1.345 0.397
23LB301597.332.053297.00347Batongcun, ChangduZiqu River1.581 2.599 6.912 2.780 1.612 0.448
23LB271646.432.1413196.54105Jiamashenshan, NangqianQiangqu River0.804 2.290 6.853 2.711 2.170 0.454
23LB281809.132.874695.57029Duonacun, ZaduoShaqunqu River1.645 2.643 6.182 3.002 1.703 0.522
23LB291854.532.8948295.23348ZaduoJinaiqu River1.849 3.967 8.964 4.743 2.757 0.404
Note: Sample 21L006, collected at the most downstream location in the Lancang River, was designated as the 0 km reference point. The along-channel distances between 21L006 and other sampling points were calculated accordingly.
Table 2. Petrographic composition of Lancang River sand (grain counts).
Table 2. Petrographic composition of Lancang River sand (grain counts).
Sample IDDrainage AreaQFLLsmLscLssChtLvLmHMTotal
21L006Lower Mainstem15857164302930201921400
21L007Lower Mainstem1805815511010552957400
21L008Lower Mainstem15664160145122014522402
21L009Lower Mainstem1636715394970301317400
21L011Lower Mainstem1314114421990152784400
21L013Middle Mainstem915925428591590446410
21L014Middle Mainstem76422664359147013422406
21L016Middle Mainstem70942012991390121235400
21L017Middle Mainstem824325912291330642116400
21L018Middle Mainstem1063324738301047551314400
21L019Middle Mainstem664427610301742481214400
21L020Middle Mainstem105342503451393481211400
21L022-1Middle Mainstem974924743510809197400
21L022Middle Mainstem100612281754123127611400
21L023Middle Mainstem9743252123510429278400
21L025Upper Mainstem10345247342116831565400
21L026Upper Mainstem5948288296516502905400
21L027Upper Mainstem129621942339106217715400
21L028Upper Mainstem8555256355513832324400
23L29Upper Mainstem12227229799770331323401
23L30Upper Mainstem1462523461068803317412
23L31Upper Mainstem86332722013393021514405
23L33Upper Mainstem7247274251368102758401
23L34Upper Mainstem69273002812810203935401
21LB015Lincang Block1536183210472130103400
21LB013Lincang Block102732176617105115138400
21LB012Lincang Block797021944615604932400
21LB011Lincang Block170676316135182132432
21LB014Baoshan Block12658432425336180407
21LB006Baoshan Block7978184195086123559400
21LB009Simao Block5859266843913406317400
21LB007Simao Block9310519755812021025400
21LB005Changdu Block1286019215171200192121401
21LB004Changdu Block78132890111770604122402
21LB003Changdu Block6293090191830802726406
21LB002Changdu Block56143200131830556911401
21LB022Changdu Block1164121617141435211627400
21LB023Changdu Block59034167672010600400
21LB026Changdu Block170671532637631111510400
21LB021Changdu Block16337200152612503223403
21LB024Changdu Block10226267592916221415400
21LB025Changdu Block87252836092104101255400
23LB31Changdu Block10531263081126051513412
23LB30Changdu Block11612256072116063516400
23LB27Changdu Block5217317314899065221407
23LB28Changdu Block202617308468019219400
23LB29Changdu Block404031016623105321110400
Qm: monocrystalline quartz, Qp: polycrystalline quartz, Pl: plagioclase, Kf: K-feldspar, L: lithic fragments (Lsm: shale, Lsc: carbonate, Lss: siltstone, Cht: chert, Lv: volcanic, Lm: metamorphic), HM: heavy minerals.
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Fang, D.; Hu, X.; Garzanti, E.; Lai, W.; Chen, F. Petrology of Lancang (Upper Mekong) River Sand. Geosciences 2025, 15, 415. https://doi.org/10.3390/geosciences15110415

AMA Style

Fang D, Hu X, Garzanti E, Lai W, Chen F. Petrology of Lancang (Upper Mekong) River Sand. Geosciences. 2025; 15(11):415. https://doi.org/10.3390/geosciences15110415

Chicago/Turabian Style

Fang, Daxin, Xiumian Hu, Eduardo Garzanti, Wen Lai, and Fengting Chen. 2025. "Petrology of Lancang (Upper Mekong) River Sand" Geosciences 15, no. 11: 415. https://doi.org/10.3390/geosciences15110415

APA Style

Fang, D., Hu, X., Garzanti, E., Lai, W., & Chen, F. (2025). Petrology of Lancang (Upper Mekong) River Sand. Geosciences, 15(11), 415. https://doi.org/10.3390/geosciences15110415

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