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1.
《吉林大学学报(地球科学版)》2015,(Z1)
化学风化作用是引起河流沉积物相对其源岩发生地球化学分异的重要因素。在化学风化的初始阶段,长石含量减少,转化为黏土矿物,主要形成2:1型层状黏土矿物,如伊利石。随着风化作用的进行,伊利石脱K转化为1:1型层状黏土矿物,如高岭石(Nesbitt and Young,1982)。水动力分选同样显著影响沉积物的矿物和元素地化组成,粒度较粗、密度较大的石英、长石与重矿物一般富集于表层沉积物中,细粒级的,具片层状结构的黏土矿物则富集于悬浮物中(Garzanti et al,2011)。本研究讨论了长江、椒江、瓯江、木兰溪浊水溪等河流沉积物(包括悬浮物与表层沉积物)的化学风化与水动力分选。这些河流分属不同的源汇体系,长江属于"大河-大三角洲-宽广陆架"的源汇体系,作为世界性的大河,其下游干流悬浮物代表整个流域上陆壳细颗粒风化物质的混合,反映整个流域的化学风化强度。台湾河流属构造隆升背景下的山溪性小河流,有"瞬时大通量—极端气候影响—快速物质转换"的特点。其河流沉积物的源岩为多旋回的沉积岩和变质沉积岩,反映出强物理风化,弱化学风化的特点。浙闽河流同属于山溪性小河流,但其流域区域构造较稳定,地形起伏也较小,加之气候炎热多雨,所以化学风化较强,反映出流域受季风气候的控制。沉积物的Al2O3/Si O2值可作为一个可靠的矿物分选指标,Al2O3/Si O2与CIA,WIP,αAl值等化学风化指标的相关关系可以指示分选与风化作用对沉积物组成的影响。WIP受石英稀释作用影响较大,而CIA几乎不受石英稀释作用影响,二者的相关关系可以指示沉积多旋回性对沉积物组成的影响(Garzanti et al,2013)。沉积物地球化学组成的"粒度控制",是由于不同粒级沉积物中矿物组成差异所致,"粒度分异"的实质是"矿物分异"。本研究从矿物入手,讨论了水动力分选及化学风化作用对河流入海沉积物的影响,揭示出分选和化风化作用共同影响沉积物的矿物及元素地化组成。元素的表生地球化学行为,本质上是由元素在不同矿物中富集及迁移的规律决定的。化学风化和水动力分选都影响碎屑沉积物矿物组成的变化,继而引起沉积物元素地球化学组成的变化。 相似文献
2.
《矿物岩石地球化学通报》2017,(3)
<正>化学风化作用是地球表面演化的重要过程之一,是地表物质循环的关键环节。然而,对于长时间尺度上硅酸盐风化的强度以及控制风化作用的因素,目前还存在争议。由于在水岩反应中会发生显著同位素分异,锂同位素被认为可以示踪硅酸盐风化。英国Durham大学的Dellinger和他的合作者汇总了全球几大水系(如亚马逊河、刚果河、长江等)的河流沉积物数据, 相似文献
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贵州省地处世界岩溶发育最复杂、类型最齐全、分布面积最大的东亚岩溶区域中心, 也是我国碳酸盐岩分布面积最大、岩溶最发育的省区, 同时也是我国水土流失严重的地区之一。由于河水的地球化学反映了流域盆地的化学风化、气候和上地壳的化学组成的重要信息, 本工作对贵州喀斯特地区两条主要水系(乌江水系、沅江水系)河流的主要阴、阳离子和Sr2＋离子及锶同位素组成变化进行了系统研究, 对河水地球化学组成变化特征及其控制因素进行了解释。 贵州喀斯特地区两条主要水系河流的水化学组成代表了典型碳酸盐岩地区河流的相应化学组成, 显示了与世界主要河流不同的水化学特征, 反映了喀斯特环境地表化学风化作用的特点。 相似文献
4.
本文对西南极地区纳尔逊冰盖边缘N1沉积序列化学元素组成特征和风化作用地球化学过程进行了研究。结果表明:N1沉积序列中元素的组成与该地区玄武质火山岩的化学组成具有密切的关系,该序列沉积物是自然环境下风化的产物,因此本文分析样品元素的平均含量可以作为该地区冰缘沉积物的背景值;冰缘沉积物所记录的源区化学风化作用强度显得非常微弱,处于脱Ca、Mg、Na早期风化阶段,碎屑矿物的风化过程多处在蒙脱石阶段;沉积序列中元素的活动强度及其比值变化,反映了局部的风化作用强度不同和气候环境的变化。上述研究结果有助于进一步研究南极冰缘环境的演变 相似文献
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6.
古红河沉积物稀土元素特征及其物源指示意义 总被引：1，自引：0，他引：1
莺歌海盆地内的大量沉积物是验证与青藏高原隆升有关的河流流域变化争论的理想材料.因此,对南海西北部莺歌海盆地6口井沉积物样品进行了稀土元素分析,结果发现,位于盆地中央轴部位的N4、N5及N6井沉积物自晚渐新世到更新世具Eu元素正异常的特征,显示其母岩应为红河流域内大量基性-超基性变质岩和火山岩;位于盆地东侧斜坡带的N1和N2井沉积物则受控于以Eu元素负异常为标志的海南岛;位于盆地东南侧的N3井沉积物晚渐新世明显受到基性物源的影响,使Eu元素呈现正异常的特征,到上新世该井沉积物主要受控于海南岛物源.越南中北部马江断裂带中古生界变质岩区以及红河流域的变质岩区为该地区提供了大量基性沉积物,造成该地区沉积物具Eu元素正异常的特征.可以认为,红河源区从晚渐新世一直到更新世时期流域内母岩类型基本保持稳定,没有大的流域母岩类型突变事件发生.因此,如果红河在其演化历史上发生过流域面积袭夺事件,其时间也只能在晚渐新世之前或更新世之后. 相似文献
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通过辽宁铁岭地区柴河流域的多介质采样研究，系统阐述了铅锌矿开采对流域地球化学特征和生态地球化学特征的改变，揭示了元素迁移转化规律，以及对矿区居民的影响。矿山开采造成其下游土壤、水、水系沉积物中Ca、Mg、Cd、Hg、Pb、Zn和s等元素的高度积累，受河流沉积作用影响而表现出纵向和垂向上的有规律变化。土壤、水、水系沉积物等介质中的重金属积累通过河流活动对生态环境构成影响，造成不同种植区域农作物籽实中含量的差异性。重金属元素通过进食和饮水等生理活动进入人体，在头发中聚集，使矿区居民头发中cd等重金属含量高于辽宁其他地区。 相似文献
9.
黄河、长江与韩国Keum、Yeongsan江沉积物常量元素地球化学特征 总被引：22，自引：3，他引：19
运用同样的样品采集和测试方法比较分析了我国的长江和黄河以及韩国的Keum和Yeongsan江的常量元素地球化学特征。韩国河流沉积物中Ca及碳酸盐含量显著低于长江和黄河,而其他元素含量则在二者之间;黄河沉积物以总无机碳(TIC)、Na和Ca含量高为特征,而长江沉积物则显著富集Ti和P。Keum和Yeongsan江沉积物中P、Ca、Fe和Mg在酸溶相中比例可达30％～66％,而K、Al和Ti则富集在残渣相中。韩国河流沉积物极低的Ca含量同流域缺乏碳酸盐源岩密切相关,其沉积物主要由侏罗一晚白垩纪的花岗岩经过中等程度的化学风化而成。虽然Ca在中韩河流沉积物之间含量差异显著,但必须谨慎运用全钙含量来识别海区物源。而沉积物中非碳酸盐态钙(Ca^*)及相应的K／Ca^*和Al／Ca^*比更适合用来示踪黄河及Keum和Yeongsan江沉积物;Ti则可以用来区分长江与其他河流沉积物。 相似文献
10.
地球化学方法示踪东亚大陆边缘源汇沉积过程与环境演变 总被引：1，自引：0，他引：1
《矿物岩石地球化学通报》2015,(5)
东亚大陆边缘发育特征的河控型边缘海沉积,其源汇沉积过程的深入研究对于深入理解地球表生过程、物质循环和大陆边缘构造沉积演化特征,具有重要意义。东亚边缘海沉积地球化学研究主要集中于几方面:入海河流沉积物的地球化学组成示踪沉积物源区的风化剥蚀特征,河口陆架区沉积地球化学行为;通过大陆边缘的沉积地球化学记录,探讨不同时空尺度河流入海沉积物的通量、搬运扩散方式及其蕴含的季风气候和海区环境演化信息。目前相关研究与国际前沿水平依然存在较大差距,需要从海陆结合的地球系统科学角度,通过地球化学与其他学科方法交叉的研究手段,从整体上研究东亚大陆边缘的沉积过程,揭示从流域到河口、陆架至开阔海的沉积物源汇系统过程和环境演变规律,及东亚大陆边缘沉积和海陆相互作用的全球意义。 相似文献
11.
通过对克里雅河、毛布拉格孔兑以及西拉木伦河三流域的河流-沙漠过渡带地表沉积物的7种常量氧化物以及15种微量元素进行因子分析,结果显示:三个流域之间或不同河段因子分析提取的公因子均可以概括为较稳定的铁锰矿物、较不稳定的长石类和方解石（白云石）类等硅酸盐矿物以及稳定的稀土元素和重矿物等类别;河流间因子分析结果表明,自西向东三个流域沿河地表沉积物的化学元素富集与迁移程度呈递增趋势,化学风化程度增强;流域内因子分析结果表明,自上游至下游,样点化学组成均愈变复杂,不同河段或不同河岸沉积物化学元素空间分布规律与其物源、地貌格局以及水分条件等因素有关;自河床至阶地,不同地貌单元地表沉积物化学元素呈相异的递变规律,这与在距离河道远近不同,物源、动力因素的分配不同有关。 相似文献
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Geochemistry of the headwaters of the Yangtze River, Tongtian He and Jinsha Jiang: Silicate weathering and CO2 consumption 总被引：1，自引：0，他引：1
Water and sediment samples were collected from the headwaters of the Yangtze River, Tongtian He and Jinsha Jiang (upstream of the Yangtze River which flows on the eastern Qinghai-Tibet Plateau). A detailed geochemical study of the river system was carried out to determine: (i) temporal and spatial variations of the major ions and their implications; (ii) contribution of carbonate, silicate and evaporite to the river dissolved load and (iii) CO2 consumption via silicate weathering. Results show that cations derived from evaporite dissolution account for 44.7–82.8% of the total cations in the headwaters of the Yangtze River and increasing from SE to NW of the drainage basin. The contribution from silicate weathering gradually increases from the headwaters due to exposure of intrusive rocks and volcanic rocks in the Jinsha Jiang suture belt. Proportion of cations derived from silicate weathering to the total cations in river waters reaches a maximum at Panzhihua City, which is consistent with the abundant exposure of Cenozoic granitoids and Precambrian high-grade metamorphic rocks around Panzhihua. The Jinsha Jiang basin has higher silicate weathering rates but lower carbonate weathering rates than the middle and lower reaches of the Yangtze River. The calculated enrichment factors of potentially harmful metals in the river sediments are within the range of 0.33–2.59, indicative of level 1 or 2 contamination. The highest enrichment factor for Co, Cr and V is found in Panzhihua City, indicating that it has been influenced by anthropogenic sources. 相似文献
13.
Geochemistry and provenance of bed sediments of the large rivers in the Tibetan Plateau and Himalayan region 总被引：1，自引：0，他引：1
Weihua Wu Hongbo Zheng Shijun Xu Jiedong Yang Hongwei Yin 《International Journal of Earth Sciences》2012,101(5):1357-1370
We investigated the geochemical characteristics of major, trace and rare earth elements and Sr–Nd isotope patterns of bed sediments from the headwaters and upper reaches of the six large rivers draining the Tibetan Plateau (the Jinsha River—Yangtze, Lancang River—Mekong, Nujiang River—Salween, Huang He—Yellow, Indus, and Yarlung Tsangpo—Brahmaputra). By using Ca/Al versus Mg/Al, La/Sc versus Co/Th, and 87Sr/86Sr versus εNd (0) binary differentiation diagrams of provenance, some typical contributors to the different catchment sediments can be identified. In the Three-River (the Jinsha, Lancang, and Nujiang Rivers) tectonomagmatic belt, acidic–intermediate-acidic volcanic rocks are very important provenance of sediments. Carbonate rocks and Permian Emeishan basalts are dominant in the Jinsha River. The Yellow River sediments have similar geochemical characteristics with loess in catchments. The Indus and Yarlung Tsangpo Rivers sediments are mainly from ultra-K volcanic rocks and Cenozoic granitoids widely distributed in the Indus–Yarlung suture. The intensity of chemical weathering in these river catchments is evaluated by calculating the chemical indices of alteration (CIA) of sediments and comparing them with bedrocks. The CIA values of the six river sediments are from 46.5 to 69.6, closing to those of bedrocks in the corresponding catchment, which indicates relatively weak chemical weathering intensity. Lithology, climate, and topography affect the chemical weathering intensity in these river catchments. 相似文献
14.
长江上游水系沉积物锶-钕同位素组成及物源示踪 总被引：3，自引：1，他引：2
泥沙资料表明,现代长江干流沉积物主要源自上游地区。因此,长江上游干支流沉积物主控关系及其源汇过程在长江水系沉积物物源示踪研究中极为重要。为探讨上述过程,详细测定了上游水系沉积物Sr-Nd同位素组成。结果显示,金沙江及闽江沉积物具有较高的εNd(0)值,主要受控于流域内大面积分布的峨眉山玄武岩的高εNd(0)背景值;嘉陵江水系沉积物具有相对较低的εNd(0)值,反映了其流域内源岩对沉积物Nd同位素组成的控制;与Nd同位素组成相比,水系沉积物87Sr/86Sr值具有更大的变化范围,表明除源岩因素外,沉积物Sr同位素组成受更为复杂的因素制约。支流与干流沉积物Sr-Nd同位素组成对比表明,长江上游干流沉积物主要来源于金沙江流域内的源岩,金沙江流域内的表壳岩系主导了上游干流沉积物的Sr-Nd同位素组成。 相似文献
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Thi Phuong Quynh Le Nhu Da Le Viet Nga Dao Emma Rochelle-Newall Thi Mai Huong Nguyen Cyril Marchand Thi Thuy Duong Thi Xuan Binh Phung 《Environmental Earth Sciences》2018,77(18):658
Global riverine carbon concentrations and fluxes have been impacted by climate and human-induced changes for many decades. This paper aims to reconstruct the longterm carbon concentrations and carbon fluxes of the Red River, a system under the coupled pressures of environmental change and human activity. Based on (1) the relationships between particulate and dissolved organic carbon (POC, DOC) or dissolved inorganic carbon (DIC), and suspended sediments (TSS) or river water discharge and on (2) the available detailed historical records of river discharge and TSS concentration, the variations of the Red River carbon concentration and flux were estimated for the period 1960–2015. The results show that total carbon flux of the Red River averaged 2555?±?639 kton C year?1. DIC fluxes dominated total carbon fluxes, representing 64% of total, reflecting a strong weathering process from carbonate rocks in the upstream basin. Total carbon fluxes significantly decreased from 2816 kton C year?1 during the 1960s to 1372 kton C year?1 during the 2010s and showed clear seasonal and spatial variations. Organic carbon flux decreased in both quantity and proportion of the total carbon flux from 40.9% in 1960s to 14.9% in 2010s, reflecting the important impact of dam impoundment. DIC flux was also reduced over this period potentially as a consequence of carbonate precipitation in the irrigated, agricultural land and the reduction of the Red River water discharge toward the sea. These decreases in TSS and carbon fluxes are probably partially responsible for different negatives impacts observed in the coastal zone. 相似文献
16.
金沙江河流悬浮物与沉积物的矿物学特征及其表生地球化学意义 总被引：1，自引：0，他引：1
为研究金沙江流域表生风化特征,系统采集了金沙江和岷江流域32件河流悬浮物和河床砂样品,对其进行了矿物组成分析。结果表明,不同江段河流悬浮物、沉积物的矿物组成大致相同,以石英、方解石、斜长石和粘土矿物为主,局部有白云石、钾长石和角闪石等;粘土矿物主要有伊利石、绿泥石、高岭石和蒙脱石。河床沉积物中非粘土矿物碎屑(岩屑)含量明显高于悬浮物。伊利石为铁镁质,Kubler指数在轻微变质范围内,主要来源于三叠系碎屑岩和砂板岩。金沙江、岷江的河流悬浮物矿物组成与流域内出露的碎屑岩、砂板岩、火成岩、碳酸盐岩等的分布有较好的对应关系。河流悬浮物和沉积物的矿物组成及伊利石结晶指数特征表明流域内以物理风化为主。 相似文献
17.
Guanqiang Cai Li Miao Hongjun Chen Guihua Sun Jiaoqi Wu Yonghang Xu 《Environmental Earth Sciences》2013,70(1):363-380
Eighty-six surface sediments collected from the northwestern continental shelf of the South China Sea (SCS) were analyzed for grain size distribution, calcium carbonate, organic carbon, and major and trace element compositions to investigate sediment provenance and factors controlling their geochemical composition. Sediments from the eastern continental shelf of Hainan Island have higher sand and lower clay content, while the samples from the nearshore Hainan Island have higher contents of gravel and clay. Calcium carbonate contents in samples show a positive correlation with water depth in northwestern shelf of SCS, suggesting that it is related to biological factors. However, the nearshore sediments have higher contents of organic carbon compared to those of the outer shelf, possibly suggesting that the terrigenous organic matter usually deposited in nearshore environments such as bays and estuaries. Compared with the upper continental crust, the samples have relatively lower contents of SiO2 and Al2O3, higher than those of the Pearl and Red river sediments. The low contents of K2O and Na2O in sediments from the northwestern continental shelf are consistent with intense chemical weathering in the river basin due to the seasonally hot and humid climate regime. The sediments mainly consist of three components, including the gravel fraction composed of calcareous debris, the sand fraction composed of quartz, and the silt and clay fractions mainly composed of clay minerals. The content of each component depends on grain size, sediment source, biogenesis, and hydrodynamic conditions, which finally controls the chemical composition of the sediments. The distributions of Co/Al2O3, Cr/Al2O3, and Zr/Sc ratios for sediments in the northwestern continental shelf suggest that source rocks are mainly composed of felsic rocks rather than mafic rocks. There is a distinct difference in sediment source between eastern and western shelf sediments; the eastern shelf sediments are characterized by high Zr/Sc ratios mainly derived from the Pearl River, while the western shelf sediments have relatively low values of Zr/Sc indicating a main contribution possibly sourced from the Red River Basin. Terrigenous materials from Hainan Island usually influence the geochemistry of sediments deposited in the nearshore area. 相似文献
18.
Northern latitude chemical weathering rates: clues from the Mackenzie River Basin, Canada 总被引：9，自引：0，他引：9
The main scope of this study is to investigate parameters controlling chemical weathering rates for a large river system submitted to subarctic climate. More than 110 river water samples from the Mackenzie River system (northern Canada) have been sampled and analyzed for major and trace elements and Sr isotopic ratios in the dissolved phase. The three main morphological units are reflected in water chemistry. Rivers from the Canadian Shield are very dilute, dominated by silicate weathering (Millot et al., 2002), whereas the rivers of the Rocky and Mackenzie Mountains as well as the rivers of the sedimentary Interior Platform are dominated by carbonate weathering and are SO4 rich. Compared to the rivers of the Mackenzie and Rocky Mountains, the rivers of the interior plains are organic, silica, and Na rich and constitute the dominant input term to the Mackenzie River mainstream. Rivers of the Canadian Shield area do not significantly contribute to the Mackenzie River system. Using elemental ratios and Sr isotopic ratios, a mathematical inversion procedure is presented that distinguishes between solutes derived from silicate weathering and solutes derived from carbonate weathering. Carbonate weathering rates are mostly controlled by runoff, which is higher in the mountainous part of the Mackenzie basin. These rates are comparable to the carbonate weathering rates of warmer areas of the world. It is possible that part of the carbonate weathering is controlled by sulfide oxidative weathering, but its extent remains difficult to assess. Conversely to what was stated by Edmond and Huh (1997), overall silicate weathering rates in the Mackenzie basin are low, ranging from 0.13 to 4.3 tons/km2/yr (Na + K + Ca + Mg), and confirm the negative action of temperature on silicate weathering rates for river basins in cold climates. In contrast to what has been observed in other large river systems such as the Amazon and Ganges Rivers, silicate weathering rates appear 3 to 4 times more elevated in the plains than in the mountainous headwaters. This contradicts the “Raymo hypothesis” (Raymo and Ruddiman, 1992). Isotopic characterization of suspended material clearly shows that the higher weathering rates reported for the plains are not due to the weathering of fine sediments produced in the mountains (e.g., by glaciers) and deposited in the plains. Rather, the relatively high chemical denudation rates in the plains are attributed to lithology (uncompacted shales), high mechanical denudation, and the abundance of soil organic matter derived from incomplete degradation and promoting crystal lattice degradation by element complexation. The three- to fourfold factor of chemical weathering enhancement between the plains and mountains is similar to the fourfold factor of enhancement found by Moulton et al. (2000) between unvegetated and vegetated watershed. This study confirms the negative action of temperature on silicate weathering for cold climate but shows that additional factors, such as organic matter, associated with northern watersheds are able to counteract the effect of temperature. This acceleration by a factor of 4 in the plains is equivalent to a 6°C increase in temperature. 相似文献
19.
松花江水系作为我国七大水系之一,对其沉积物组成的深入探究对揭示源区控制因素和沉积物的搬运—沉积过程具有重要意义。重矿物蕴含着源岩母岩的重要信息,是解开由源到汇过程和物源示踪的重要工具。为了评估物源、河流过程和化学风化对重矿物组成的影响,我们从松花江水系干流和支流的边滩以及阶地共取32个样品,进行分粒级(<63μm、63~125μm和125~250μm)的重矿物分析。结果表明,松花江水系源区母岩信息在嫩江各支流(诺敏河最为典型)的重矿物组成中得到很好的反映,但在嫩江干流中没有得到反映,这表明物源对重矿物组成的控制受到河流过程的影响。松花江水系的重矿物组成以角闪石、绿帘石、钛铁矿和榍石为主。河流沉积物的重矿物组成主要富集在63~125μm组分,同一河流的不同河段的重矿物组成存在显著差异(巴兰河尤为典型),表明了河流搬运—沉积过程对重矿物组成起到重要控制。哈尔滨松花江T2阶地沉积物(弱风化)的重矿物组成基本保留了现代河流砂特征,讷谟尔河T1阶地沉积物(中等风化)的重矿物受到一定程度的改造,而受到严重化学风化影响的通河松花江T3阶地的重矿物组成已遭受严重破坏,不稳定矿物(角闪石和辉石)以及蕴含的母岩信息已完全消失,表明了重矿物组成明显受到沉积物化学风化程度的影响。由于源—汇过程中重矿物的混合和由此导致的稀释作用,使得沉积物携带的物源信息经过长距离搬运之后逐渐变得模糊。因此,我们认为,在进行河流重矿物源—汇过程研究中,宽粒度分析窗口和足够多的样品数量需要考虑以充分获取源区完整的重矿物组成信息。同时,在利用河流阶地重矿物组成进行源—汇联系和古水系演化研究时,需要首先评估阶地沉积物的化学风化程度。 相似文献