Petrology and geochemistry of clastic sedimentary rocks as evidences for provenance of the Late Palaeozoic Madzaringwe Formation,Tshipise-Pafuri Basin,South Africa

Petrography and geochemistry(major, trace and rare earth elements) of clastic rocks from the Late Palaeozoic Madzaringwe Formation, in the Tshipise-Pafuri Basin, Northern South Africa, have been investigated to understand their provenance. Sandstone petrography and detrital modes indicates that the Late Palaeozoic succession was derived from craton interior and recycled orogen provenance. Sandstones in the Madzaringwe Formation are sub-arkosic to sub-litharenite. The sediments may represent a recycled to craton interior provenance. The geochemical data of major elements show that sandstone and shales have the same source. The study of paleoweathering conditions based on modal composition, chemical index of alteration(CIA) and A-CN-K(Al2O3-Ca O+Na2O-K2O) relationships indicate that probably chemical weathering in the source area and recycling processes have been more important in shale and sandstone rocks. The relatively high CIA values(70–90%) indicates moderate to high weathering conditions of the samples and the paleoclimate of the source area was warm. K2O/Na2 O versus Si O2 and Na2O-Ca O-K2 O tectonic setting discrimination plots, suggest a passive continental margin. In the study of trace elements, triangular Th-Sc-Zr/10 and La-Th-Sc plots both suggest a passive margin setting of the basin. Petrographic and geochemical results of the samples suggest uplifted basement source areas dominated by sedimentary rocks and/or granite-gneiss rocks. The source rocks might have been the recycled pre-Soutpansberg Karoo Supergroup rocks and the metasedimentary rocks of the Soutpansberg Group. Other source rocks may have been the pre-Beit-Bridge basement rocks(granites and gneisses).     

Geochemistry of Tertiary sandstones from southwest Sarawak,Malaysia: implications for provenance and tectonic setting

Tertiary sandstones collected from southwest Sarawak, Malaysia, were analyzed to decipher their provenance, weathering, and tectonic setting. The studied sandstones have a sublitharenite composition and are dominantly composed quartz with little mica and feldspar,and a small amount of volcanic fragments. These sandstones were generally derived from quartz-rich recycled orogenic sources. They have relatively high SiO_2 content with low Na_2 O, Ca O, Mn O, and Mg O contents. Values of Chemical Index of Alteration(CIA) of these rock samples vary from 71 to 93, with an average of 81, implying intense chemical alteration during weathering. A felsic igneous source is suggested by a low concentration of Ti O2 compared to CIA, enrichment of Light Rare Earth Elements,depletion of Heavy Rare Earth Elements, and negative Eu anomalies. A felsic origin is further supported by a Eu/Eu*range of 0.65–0.85 and high Th/Sc, La/Sc, La/Co, and Th/Co ratios. This work presents the first reported geochemical data of Tertiary sandstones of the Sarawak Basin. These data led us to conclude that the sandstones were dislodged from recycled orogenic sources and deposited in a slowly subsiding rifted basin in a passive continental tectonic setting.     

Geochemical characteristics of Neogene sandstones of the East and West Siang Districts of Arunachal Pradesh,NE India:implications for source-area weathering,provenance,and tectonic setting

Sandstones from the Neogene Siwalik successions of the East and West Siang Districts of Arunachal Pradesh were analyzed to evaluate source-area weathering,provenance,and tectonic setting by using major,trace,and rare earth elements(REEs)as proxies.The sandstones are classified as lithic arenite and wacke arenite based on their mineralogical compositions.The values of different weathering indices such as Chemical Index of Alteration(CIA;60.93–89.86)and Chemical Index of Weathering(CIW;40–96.8)suggest moderate to intense weathering in the source area.The plot of Th/Sc versus Zr/Sc indicates enrichment of zircon by sediment sorting and/or recycling from a weathered source.The high positive correlation between Al2 O₃ and K2 O points towards a strong influence of the constituent clay minerals on the major oxide composition of the sandstones.Petrographic analysis together with enriched LREE,flat HREE,negative Eu anomalies(Eu/Eu^*=0.47 to 0.90)in the chondrite-normalized diagrams,and the ratios of La/Sc,La/Co,Th/Sc,Th/Co,Cr/Th collectively suggests that the Neogene sediments were derived from felsic igneous and/or reworked sedimentary/metasedimentary sources in an upper continental crustal setting.The geochemical characteristics of the studied Neogene Siwalik sandstones indicate that the sediments were sourced from pre-Himalayan gneisses and granitoids together with metabasic rocks,which had formed in a passive margin tectonic setup.     

Geochemistry of metasedimentary rocks of the Sonakhan and Mahakoshal greenstone belts,Central India:Implications for paleoweathering,paleogeography and mechanisms of greenstone belt development

A comparative study of the Precambrian Sonakhan(SGB)and Mahakoshal(MGB)greenstones belts of Central India has been undertaken to decipher their provenance,paleoweathering,paleogeography,and tectonics.As compared to the Upper Continental Crust(UCC),the MGB samples are enriched while the SGB samples are depleted in mafic elements indicating the presence of mafic rocks in the source of the MGB.This is complemented by the Ni–Cr diagram.The REE concentrations,LREE fractionated patterns and negative Eu anomalies of the MGB and SGB samples indicate derivation of sediments from a highly fractionated granitic source.Since MGB samples also contain the geochemical signature of mafic rocks,it is,therefore proposed that the MGB clastic load were derived from two sources(mafic+felsic)with arc character.This is attested by Cr and Zr relationships,and LILE enrichment,and HFSE depletion.These features suggest that the SGB developed as autochthonous while the MGB developed as an allochthonous belt.The chemical alteration indices such as chemical index of alteration(CIA),plagioclase index of alteration(PIA),and index of compositional variability for MGB samples indicate that they were dominantly derived as the first cycle(with minor recycled)sediments from bimodal sources(dominantly continental arcs)by intense chemical weathering as compared to the SGB samples,which were derived from felsic sources(dominantly cratonic rocks),and partly by recycling through a low chemical weathering.The CIA and PIA values of the samples reveal a change in the climatic conditions from Late Archean to Late Paleoproterozoic.Such change is interpreted in terms of migration of the Indian plate from high latitudes in the Late Archean to lower latitudes during the Late Paleoproterozoic.This is consistent with the paleomagnetic data that placed India in the configuration of 2.45 Ga Ur and 1.78 Ga Columbia supercontinents.     

Sediment recycling and indication of weathering proxies

As a result of recycling, the mineralogical and chemical compositions of riverine sediments may reflect the combined effects of the present-day weathering regime as well as previous weathering and diagenetic alteration history. River sediments can be interpreted as a mixture of non-weathered bedrock—of igneous, metamorphic, or sedimentary origin—and solids formed by the modern weathering system. The correlation between the weathering proxies chemical index of alteration and weathering index of Parker offers an approach to distinguish fine suspended particles, coarse bedload sediments, and recycled sediments under the influence of quartz dilution. Recycling of cation-depleted source rocks formed during past geological weathering episodes may have great impacts on the weathering indices of sediments from the Changjiang(Yangzte) and Zhuoshui Rivers. Special caution is required when using chemical weathering indices to investigate the intensity of chemical weathering registered in fluvial sediments. To minimize the effect of hydrodynamic sorting or sediment recycling, we suggest that the fine sediments(e.g.suspended particles and ﹤2 lm fractions of bedload sediments) in rivers better reflect the average of weatheredcrust in catchments and the terrigenous end-member in marginal seas.     

Rare earth element chemistry indicates chemical alteration of zircons during the evolution of weathering profile

Although rare earth elements(REEs)in magmatic zircons have been widely used to identify the type and compositional evolution of host rocks,REE distribution patterns during the chemical alteration of zircons need clarification.We investigated REE characteristics in zircons with different degrees of chemical weathering through systematic observation of a granodiorite-weathering profile in southeast China.Despite the relatively stable provenance of the studied profile(zircon U–Pb ages are95.2±4.8 Ma),the zircon REEs exhibited systematic differences in abundance and fractionation patterns from the bedrock to upper layers,e.g.∑PREE,(LREE/HREE)_(CN),and Ce/Ce*.This evidence suggests chemical alteration of zircons during intensive chemical weathering and an expected influence on REE variability in the weathered products due to the presence of REE-bearing minerals.     

Mineralogy and geochemistry of sands of the lower course of the Sanaga River,Cameroon: implications for weathering,provenance, and tectonic setting

This study focuses on the mineralogy and bulk chemical composition of 19 sediment samples, collected from the Sanaga River bed, between Nanga-Eboko and the Atlantic Ocean in Cameroon, to infer provenance, weathering, and tectonic setting. The textural analysis revealed that these sediments are mainly coarse-grained sands.X-ray diffraction and heavy mineral analyses show that these sands are made of quartz, microcline, plagioclase,muscovite, ilmenite, anatase, magnetite, opaques, and epidote. The Index of Chemical Variability values(1.07–2.68) indicates that the sands are immature. The Chemical Index of Alteration(53–66 %), Plagioclase Index of Alteration(PIA; 57–75 %), and Mafic Index of Alteration(54–67 %) values revealed a moderate intensity of weathering for these sediments. According to the compositional maturity diagram, the sands are mainly litharenites.The studied sands show enrichment in light rare earth elements relative to heavy rare earth elements and a negative anomaly in Eu(Eu/Eu* = 0.32–0.83). These sands were derived from felsic metamorphic rocks dated Meso to Neoproterozoic from the Pan-African(700–1000 Ma)domain of south Cameroon. Th/U ratios(mean = 5.40; n =19) reveal that these sands originating from felsic source rocks and are low to moderately recycled. On the tectonic discrimination diagrams, all the samples are plotted in the rift and passive margin domains, which is consistent with the tectonic history of Pan African in southern Cameroon.     

Paleoclimatic indication of X-ray fluorescence core-scanned Rb/Sr ratios: A case study in the Zoige Basin in the eastern Tibetan Plateau

The X-ray fluorescence(XRF)core-scanned Rb/Sr ratios of lake sediments have been widely used as a proxy for chemical weathering intensity and past climate change.However,some factors could affect Rb/Sr ratios,causing misinterpretation and limiting its application.In this study,we present a high-resolution XRF core-scanned Rb/Sr record of core ZB13-C1 from the Zoige Basin in the eastern Tibetan Plateau.To validate its application,we correlated this record with the chemical index of alteration(CIA)and other paleoclimatic proxies.Our results showed that(1)the core-scanned Rb/Sr ratios and CIA were reliable proxies of chemical weathering intensity in fine-grained sedimentary sequences;(2)the low values of corescanned Rb/Sr ratios and CIA were significantly correlated with high total organic carbon content,arboreal pollen content,carbonate content,and C/N ratios,confirming its reliability as a proxy for the Asian summer monsoon intensity;(3)the corescanned Rb/Sr ratios at core depths of 25–0.3 and 56–47 m were unable to reliably reflect chemical weathering intensity due to both the grain-size effect and the low test accuracy.Our study highlights the need for mutual verification of multiple indicators before accurately applying Rb/Sr as a paleoclimatic proxy in other similar study areas.     

Rare earth element geochemistry of the Permo-Carboniferous clastic sedimentary rocks from the Spiti Region,Tethys Himalaya:significance of Eu and Ce anomalies

Siliciclastic sedimentary rocks,including sandstones and associated shales,from the Permo-Carboniferous Kanawar Group of NW Tethys Himalaya,Spiti Region,India were examined geochemically to monitor the evolutionary changes in the upper continental crust in the Himalaya.The rocks are characterized by consistent rare earth element(REE) patterns with light REE enrichment(La_N/Yb_N = 5.3-28.2) and flat heavy REE patterns.The∑REE values are high(up to 281 ppm) with large negative Eu anomalies(avg.Eu/Eu~* = 0.57).The REE characteristics of the sediments are similar to those of postArchean Australian shales and North American shale composite.La/Th values(avg.2.34) correspond to a relatively felsic composition of the terrestrial igneous rocks standard(La/Th of G-1 = 2.3).The evolved felsic composition of the sediments probably relates to widespread acidic activity in the source.The REE patterns and Th/U values seem to have been affected by the sedimentary environment as well as by the provenance.The presence of positive Ce anomalies in some sediments may be the result of post-depositional processes.Moreover,the Permo-Carboniferous sediments indicate that hydraulic sorting,even over short transport distances,is capable of concentrating enough accessory phases to influence REE composition and to develop negative Eu anomalies.High ∑REE,La/Yb,and Th/U contents and large negative Eu anomalies reveal that the sediments were deposited in an oxidizing environment,suggesting the surficial environment became oxidizing around the Carboniferous-Permian boundary in the Indian craton.     

Geochemical characteristics of the metapelites from the Xingxingxia group in the Eastern Segment of the Central Tianshan: Implications for the provenance and paleoweathering

Clastic sedimentary rocks record a number of in-formation about the compositions and paleoweathering conditions of the source areas, and the tectonic setting of the depositional basin[1―6]. The traditionallypetrological study commonly utilizes the major com-ponents (Quartz, Feldspar and Lithics) of the silici-clastic sedimentary rocks to investigate the source rock composition and tectonic setting[7]. However, thepetrological method is somewhat limited, because many of the mafic components f…     

Paleogeographic evolution of the Lower Yangtze region and the break of the “platform-slope-basin” pattern during the Late Ordovician

Wide distribution of the black shales and diversification of the graptolite fauna in South China during the Late Ordovician resulted from its unique paleogeographic pattern, which was significantly affected by the paleogeographic evolution of the Lower Yangtze region. In the study, 120 Upper Ordovician sections from the Lower Yangtze region were collected, and a unified biostratigraphic framework has been applied to these sections to establish a reliable stratigraphic subdivision and correlation. Under the unified time framework, we delineate the distribution area of each lithostratigraphic unit, outline the boundary between the sea and land, and reconstruct the paleogeographic pattern for each graptolite zone. The result indicates that, with the uplift and expansion of the ‘Jiangnan Oldland' in the beginning of the late Katian, the oldland extended into the Yangtze Sea gradually from south to north, which finally separate the Jiangnan Slope and the Yangtze Platform. Consequently,the longstanding paleogeographic pattern of "platform-slope-basin" in South China was broken. The paleogeographic change led to sedimentary differentiation among the two sides of the ‘Jiangnan Oldland' during the Late Ordovician. This event also led to the closure of the eastern exit of the Upper Yangtze Sea, and formed a semi-closed, limited and stagnant environment for the development of the organic-rich black shales during the Late Ordovician. The major controlling factors of these paleogeographic changes in the Lower Yangtze region were not consistent from the Katian to the Hirnantian. In the late Katian, the sedimentary differentiation between the east and west sides mostly resulted from regional tectonic movement-the Kwangsian Orogeny.However, during the Hirnantian, the whole Yangtze region became shallower, which was mostly influenced by the concentration of the Gondwana ice sheet and the consequent global sea level drop.     

Crustal electric structure of Haiyuan arcuate tectonic region in the northeastern margin of Qinghai-Xizang Plateau, China

Through the analysis and 2-D inversion for the 5 profiles in Haiyuan arcuate tectonic region (105°～107°E,36°～37.5°N) in the northeastern margin of Qinghai-Xizang Plateau, we have obtained the electric structure within a range of 160 km in width (east-west) and 60 km in depth in the studied area. The results show that the crustal electric structure can be divided into 6 sections, corresponding respectively to Xiji basin (Ⅰ), Xihuashan-Nanhuashan uplift (Ⅱ), Xingrenbu-Haiyuan basin (Ⅲ), Zhongwei-Qingshuihe basin (Ⅳ), Zhongning-Hongsibu basin (Ⅴ) and west-margin zone of Ordos (Ⅵ) from the southwest to the northeast. The crustal electric structure is characterized by a broom-shaped pattern, which scatters to the northwest and shrinks to the southeast. The structures in the top part of Haiyuan arcuate tectonic region are complete and large, however, they diminish from the arc top to the northwest and southeast ends. In the depth from 0 km to 10 km, the resistivity is high in the sections Ⅱ and Ⅵ, but relatively low in the other four sections, showing a similar pattern of basin depression. The electrical basement in the section Ⅲ is the deepest, displaying a "dustpan" shape that is deep in the southwest and shallow in the northeast. A series of discontinuous zones with high conductivity exist in the middle-lower crust in Haiyuan arcuate tectonic region, which is possibly related to the moderate and strong earthquakes in the region. The resistivity distribution in the focal area of the 1920 Haiyuan earthquake is significantly heterogeneous with an obviously high conductivity zone near the hypocenter regime.     

Revisiting the Mg isotopic systematics of siliciclastic components of sediments and sedimentary rocks: A new geochemical proxy of continental weathering in Earth's history

The Mg isotopic compositions of siliciclastic components(δ²⁶Mg_sili) of sediments and sedimentary rocks have been commonly used to constrain the intensity of continental weathering, based on observations of,(1) an upward enrichment of ²⁶Mg in modern weathering profiles,(2) preferential uptake of ²⁶Mg in soil clays, and(3) general positive correlations between weathering intensities and δ²⁶Mg_silivalues. However, not all weathering p...     

Model of rigid and elastic-plastic motion in intraplate blocks and strain status of principal blocks in Chinese mainland

Introduction The Chinese mainland is located in the southeastern part of Eurasia plate and encircled by India, Eurasia, Pacific and Philippine Sea plates. It is one of areas with the strongest tectonic de-formation, especially Qingzang (QinghaiXizang) plateau and NS tectonic zone where the tec-tonic activity is more intensive and intricate. The main part of tectonic activity of Chinese mainland includes a series of tectonic zones and active blocks divided by them. Therefore, the research…     

Essential Features of Tectonic Movement Revealed by Crustal Vertical Deformations in the Mainland of China

Based on the precise reieveling data of more than 260,000 km carried out from 1950 to 1991 in the Chinese mainland,recent crustal vertical movement is studied.By means of some quantitative indices,such as the pattern of crustal vertical movement,the intensity of differential movement,the maximum gradient and its distribution,etc.,the properties of movements are analyzed on a large scale.The results suggest that all the properties have a profound tectonic background of their own and are closely related to the zoning and seismic activity of active subplates.The driving force for the movement comes mainly from the northward push of the India plate acting on the Eurasia plate.The effects of motions of the Pacific and Philippine Sea plates in the east are much less significant.     

Provenance discrimination and Source-to-Sink studies from a dryland fluvial regime： An example from Kachchh,western India

Tracing the sediment delivery from its source terrain to its ultimate sink envisage multiple factors that play a vital role in understanding present day erosional engine.To accomplish this,it is significant to distinguish the variable end-members contributing to the basin.The findings from the study of dryland coastal fluvial regime in Kachchh(Western India),which is one of the end members contributing to the Gulf of Kachchh coast(partial sink) and finally to the Arabian Sea(ultimate sink) have been presented here.Multi-proxy sediment provenance proxies such as grain-size,clay minerals,geochemistry and magnetic minerals have been employed to evaluate the provenance discriminating characteristics of the Kachchh dryland fluvial system and factors influencing them.The results of different proxies indicate that the provenance signatures of uplands are quite characteristic with magnetic susceptibility(χ) values of 20×10~(-7)m~3kg~(-1) and smectite(S)/kaolinite(K) ratio between 0.26 and 0.49.The middle reaches show marked increase in magnetic mineral concentration with χ values(140×10~(-7)m~3kg~(-1))and S/K ratio(4.92),while the estuarine tract shows χ values(80×10~(-7)m~3kg~(-1)),S/K ratio(1.90) and,characteristic heavy minerals(i.e.mica minerals),probably reflect the interplay between land and sea oscillations.Major sources of sediments within catchment scale were identified,viz.,upland sedimentary rocks(Juran and Bhuj Formation sandstone-shale) and middle reaches volcanic(Deccan Trap Formation basalt) rocks.The present study draw cautions in provenance of sediment discrimination in areas influenced by Deccan basalt that has the overwhelming sediment delivery and a comparatively subdued effects of other provenance signatures.The studied proxies of mineralogy of clays,magnetic minerals and geochemistry of heavy and major elements serve as the potential for fingerprint of sediment source regions and hence behold a strong position in source to sink studies globally.     

The Langjiexue Group is an in situ sedimentary sequence rather than an exotic block: Constraints from coeval Upper Triassic strata of the Tethys Himalaya(Qulonggongba Formation)

The Upper Triassic Langjiexue Group in southeastern Tibet has long been an enigmatic geological unit. It belongs tectonically to the northern Tethys Himalayan zone, but provenance signatures of the detritus it contains are significantly different from those of typical Tethys Himalayan sandstones. Because the Langjiexue Group is everywhere in fault contact with Tethys Himalayan strata, its original paleogeographic position has remained controversial for a long time. According to some researchers, the Langjiexue Group was deposited onto the northern edge of the Indian passive continental margin, whereas others interpreted it as an independent block accreted to the northern Indian margin only during final India-Asia convergence and collision in the Paleocene. This study compares the Langjiexue Group and coeval Upper Triassic strata of the southern Tethys Himalayan zone(Qulonggongba Formation). Our new provenance data indicate that Qulonggongba Formation sandstones contain common felsic volcanic rock fragments, minor plagioclase, and euhedral to subhedral zircon grains yielding Late Paleozoic to Triassic ages. These provenance features compare well with those of the Langjiexue Group. Because the Qulonggongba Formation certainly belongs to the Tethys Himalayan zone, the provenance similarity with the Langjiexue Group indicates that the latter is also an in situ Tethys Himalayan sedimentary sequence rather than part of an exotic block. Volcanic detritus including Late Paleozoic to Triassic zircon grains in both Langjiexue Group and Qulonggongba Formation are interpreted to have been derived from the distant Gondwanide orogen generated by Pan-Pacific subduction beneath the southeastern margin of Gondwana. The Qulonggongba Formation, deposited above marlstones of the lower Upper Triassic Tulong Group, is overlain by India-derived coastal quartzose sandstones of the uppermost Triassic Derirong Formation. Deposition of both the Qulonggongba Formation and the Langjiexue Group were most likely controlled by regional tectonism, possibly a rifting event along the northern margin of Gondwana.     

The Activity of Major Faults and the Hydrothermal Alteration Zone at Tianchi Volcano of Changbaishan

It is found by field investigation that the near horizontal top surface of the brown or brick-red hydrothermai alteration zone varies obviously in elevation at different sections of the same layer on the caldera‘s inner wall of Tianchi, with that at the north section near the Tianwen Peak about 110 m higher than that at the south near the Jiangjun Peak in Korea. The top surface of the hydrothermai alteration zone can be taken as key horizon to tectonic movement. The difference indicates that the total uplift height of the NW wall of the Liudaogou-Tianchi-Jingfengshan fault, the principal fault trending NE at Tianchi, is bigger than that of the SE wall ever since the occurrence of hydrothermal alteration. This also explains why the topography in the northwest side of Tianchi is steeper and with more developed river system than in the southeast. The uplifting of the northeastern wall is bigger than that of the southwest along the principal NW-trend fault, namely, the Baishanzhen-Tianchi-Jince fault. It is observed from characters of hydrothermal alteration and the palaeoresiduum, that the recent vertical movement rate along the principal NE-trend fault is larger than that of the principal NW-trend fault. The two faults intersect at Tianchi, dividing the volcano into 4 blocks, with the uplift magnitudes decreasing successively in the order of the north, the west, the east and the south block. The biggest uplift of the north block corresponds well to the shallow magma batch in the north of Tianchi observed by DSS and telluric electromagnetic sounding, and etc. and they may be related with the causes.     

Upper Cretaceous trench deposits of the Neo-Tethyan subduction zone: Jiachala Formation from Yarlung Zangbo suture zone in Tibet,China

The history of convergence between the India and the Asia plates, and of their subsequent collision which triggered the Himalayan orogeny is recorded in the Yarlung Zangbo suture zone. Exposed along the southern side of the suture, turbidites of the the Jiachala Formation fed largely from the Gangdese arc have long been considered as post-collisional foreland-basin deposits based on the reported occurrence of Paleocene-early Eocene dinoflagellate cysts and pollen assemblages. Because magmatic activity in the Gangdese arc continued through the Late Cretaceous and Paleogene, this scenario is incompatible with U-Pb ages of detrital zircons invariably older than the latest Cretaceous. To solve this conundrum, we carried out detailed stratigraphic, sedimentological, paleontological, and provenance analyses in the Gyangze and Sajia areas of southern Tibet,China. The Jiachala Formation consists of submarine fan deposits that lie in fault contact with the Zongzhuo Formation.Sandstone petrography together with U-Pb ages and Hf isotope ratios of detrital zircons indicate provenance from the Gangdese arc and central Lhasa terrane. Well preserved pollen or dinoflagellate cysts microfossils were not found in spite of careful research, and the youngest age obtained from zircon grain was ～84 Ma. Based on sedimentary facies, provenance analysis and tectonic position, we suggest that the Jiachala Formation was deposited during the Late Cretaceous(~88–84 Ma) in the trench formed along the southern edge of Asia during subduction of Neo-Tethyan oceanic lithosphere.     

Hydrochemistry and carbon isotope characteristics of Nujiang River water: Implications for CO2 budgets of rock weathering in the Tibetan Plateau

The Tibetan Plateau is one of the most complicated geographical units worldwide in terms of its tectonic and environmental background.Although a hotspot for continental weathering and carbon cycling studies,accurate determination of the weathering carbon budget is challenging in this area,especially sink and source flux quantification and the controlling mechanisms.Compared with other major rivers on the plateau,the Nujiang River is characterized by less human disturbance and maintains a relativ...