就若干矿床的类型、成矿物质来源及辉钼矿含铼量的地质意义等与毛景文研究员商榷

毛景文研究员等多年来将陕西洛南黄龙铺碳酸岩脉型钼(铅)矿床分别更改为碳酸盐(岩)型、热液碳酸盐脉型或脉型,把河南栾川南泥湖斑岩体形成复合的南泥湖—三道庄斑岩—夕卡岩型钼(钨)矿床,分解为南泥湖斑岩钼钨矿床和三道庄夕卡岩型钼钨矿床,和把长江中下游地区的绝大多数夕卡岩型铜(铝)矿床和少数斑岩—夕卡岩型铜(钼)矿床更改为斑岩—夕卡岩—层控铜—金—钼矿床等。本文对毛景文等更改这些矿床的矿床类型,以及毛景文等认为"辉钼矿的Re含量可指示成矿物质来源","大水沟热液型碲(金)矿床的成矿流体及其他物质主要来自于地幔"和"温泉钼矿是与S-型花岗岩有关的斑岩钼矿床是一种新类型和新发现"等所存在的问题进行探讨。希能理清某些矿床学问题,进一步促进矿床学的发展。     

与角岩有关的矿床主要类型及其对深部找矿的意义

作为热接触变质的产物,角岩在石墨、硅灰石、红柱石等变质成因非金属矿床和各种金属矿床以及油气矿藏均可见,但对其调查研究成果并不多。在文献综述的基础上,结合在南岭、冈底斯等重要成矿带地质找矿的实践,通过对与矿产资源有关的角岩广义概念的界定,概述了与角岩有关的各主要类型矿床的地质特征,如石墨、硅灰石、红柱石等变质成因非金属矿床,钨、钼、铁、铜、铀、金、铅锌、锡、银和稀有金属矿床以及油气矿藏;举例阐述了近年来角岩发育矿区深部找矿中的新突破,如江西淘锡坑钨矿,广西大厂铜坑至拉么一带的锡多金属矿床,西藏甲玛铜多金属矿,云南老厂银铅锌矿、羊拉铜矿、雪鸡坪铜矿等矿区;讨论了角岩型矿床成矿预测的准则。结果表明：矿区和矿田大比例尺深部预测时应注意岩石组合、干湿关系、封闭与开放体系、岩石物性和分带性、原岩岩性及其空间配置关系;区域性中、小比例尺成矿评价时应注意角岩的空间分布、岩石学特征与矿产资源的专属性关系等;利用角岩预测隐伏岩体的应用前景广泛,在深部找矿中具有现实意义。建议加强角岩与成矿关系的理论研究,对以往地质填图工作中发现的＂角岩化带＂可重新评价其与成矿的关系。     

小柳沟铜钨矿田矿化特征及找矿方向

小柳沟铜钨矿田现已发现矿床4处，小柳沟铜钨矿床以赋存于云母角闪片岩，夕卡岩，夕卡岩化灰岩中的似层状矿化为主，矿体规模较大，品位高，矿物成分复杂，围岩蚀变发育，世纪铜钨矿床仅以云母角闪片岩中似层状矿化为主，矿体规模较大，品位较高，矿物成分较简单，围岩蚀变较发育。祁宝铜钨矿床以赋存于岩体接触带中夕卡岩型矿化为主，矿体规模较小，品位低，矿石成分简单，围岩蚀变较发育。贵山铜钨矿床以云母角闪片岩中似层状矿化为主，矿体规模小，品位较低，矿石成分简单，围岩蚀变较发育。其找矿方向为：小柳沟铜钨矿床西部，世纪铜钨矿床西部及北部，贵山铜钨矿床东部云母角闪片岩，灰岩及Ⅰ－Ⅱ级重砂异常分布区，花岗岩体接触带各石英脉。     

小柳沟铜钨矿区矿化特征及找矿方向

小柳沟铜钨矿赋存于长城系朱龙关群中，其中以赋存于云母角闪片岩，夕卡岩，夕卡岩化灰岩中的似层状矿化为主，矿体规模大，品位高，矿物成分复杂，围岩蚀变发育，其次为赋存于岩体接触带的夕卡岩型似层状，透镜状矿体，矿体规模较大，但品位低，矿石成分简单，围岩蚀变较发育，另外还有赋存于石英网脉带中的脉状矿体，矿体规模小，品位较低，矿石成分简单，围岩蚀变较发育。根据对矿区控矿条件及矿化富集规律的研究，今后该矿区找矿靶区为：小柳沟铜钨矿区西矿段西部及北部，北矿段及东矿段中的云母闪片岩，灰岩及Ⅰ，Ⅱ级重砂异常分布区，隐伏花岗岩体及地表花岗岩枝与围岩的接触带，石英网脉带脉。     

青藏高原甲玛斑岩成矿系统首例3000 m科学深钻的初步认识

青藏高原碰撞造山带中复杂的地质结构、深部矿产资源潜力和高效的勘查评价技术体系一直是地质学家关注的焦点,也是亟需攻克的重要科学难题.受国家重点研发计划-深地专项资助,在冈底斯成矿带甲玛斑岩成矿系统实施首个3000 m科学深钻.通过多次研讨和反复论证,确定科学施工位置、角度以及施工工艺.历时488天的施工,完成了科学深钻,总进尺3003.33 m.该科学深钻直接揭示甲玛超大型斑岩成矿系统3000 m以浅的地质信息:浅部为角岩型铜钼矿体、中部为矽卡岩型铜多金属矿体、深部为斑岩型钼铜矿体以及核部蚀变与矿化均不发育的无矿核.角岩中主要为细脉浸染状的黄铜矿、辉钼矿化,并发育黑云母化和弱绿泥石化蚀变.矽卡岩中从上到下具有清晰的分带结构,即石榴子石绿泥石角岩、绿泥石石榴子石角岩、透辉石石榴子石矽卡岩、石榴子石矽卡岩、石榴子石硅灰石矽卡岩、硅灰石矽卡岩、矽卡岩化大理岩.矿化主要为浸染状的斑铜矿、黄铜矿、辉钼矿.深部斑岩为复式岩体,主要为二长花岗斑岩,侵位较早,后被花岗闪长斑岩、石英闪长玢岩等以岩脉的形式穿切侵位.花岗闪长斑岩与矽卡岩关系最为密切.多相的复式斑岩体也揭示了甲玛斑岩成矿系统的无矿核.根据现有工业指标,科学深钻共计探获21层矿体,累计厚度583.46 m,以铜、钼矿化为主,局部发育钨矿化,同时伴生金、银矿化.甲玛科学深钻首次直接揭示青藏高原3000 m以浅的地质信息和斑岩成矿系统结构,为青藏高原地质结构研究提了科学样品,也为深部资源探测和勘查技术体系研究提供了关键支撑.后续将针对其开展详细的地球化学分析、地球物理测井、高光谱测量以及指针矿物分析等研究,并结合地表勘查评价成果,建立3000 m以浅的多元信息综合勘查评价模型,进而定位预测深部矿产资源,实现增储示范.     

闽西小康锰银多金属矿地质特征及找矿方向

小康锰银多金属矿受下三叠系溪口组地层、断裂构造破碎带和花岗斑岩接触带控制,氧化锰(银)矿床属"淋积型",含锰层经热液叠加改造和风化淋滤后在层间断裂破碎带中富集成矿;铜铅锌矿体分布于酸性偏中性的花岗岩体外接触带中(部分为层状夕卡岩),呈浸染状赋于夕卡岩中或沿裂隙充填成矿.主要围岩蚀变有夕卡岩化和角岩化.该矿床从上至下具Mn(Fe)-Ag,Pb,Zn-Cu,Pb,Zn的垂直分带规律.     

西秦岭天水范家山夕卡岩型铜金矿床地质特征及成因探讨

范家山铜金矿位于西秦岭北成矿亚带,温泉复式花岗岩天水斑岩夕卡岩钼铜金矿带的核心位置。矿床地质特征表明：范家山铜金矿体主要受岩体与围岩接触带以及岩体附近的断裂破碎带的控制,以金铜矿化为主,围岩蚀变为夕卡岩化、角岩化及硅化、绢英岩化等。范家山铜金矿床主矿脉包裹体温度、盐度及H-O同位素研究显示,主成矿流体的盐度(S)为2.0%～11.0%(w(NaCl)eq),均一温度为120～345 ℃,主要集中在150～280 ℃范围,具有中温和中低盐度的特征,为岩浆水和大气降水的混合。成矿花岗斑岩锆石U-Pb年龄为(248.3±1.9) Ma(MSWD=0.67, N=9),表明成矿活动发生在印支早期。结合区域构造背景,范家山铜金矿为印支期早期陆陆碰撞导致地壳加厚背景下的夕卡岩型矿床,深部具有斑岩型成矿的潜力。     

广西平南县罗平钨矿床地质特征及成因

广西平南县罗平钨矿床位于桂东大瑶山成矿带中部六岑金矿田内,矿体赋存在加里东期花岗斑岩脉中及其外接触带附近。矿石岩性主要为黄铁绢英岩化花岗斑岩和硅化、黄铁矿化变质砂岩,有用金属矿物以白钨矿为主,少量黄铜矿、辉钼矿,矿石构造以细脉浸染状构造为主。围岩蚀变以硅化、黄铁矿化、绢云母化为主,蚀变范围广,总体上呈面状分布。钨矿控矿条件主要有凭祥-大黎深大断裂、加里东期岩浆岩及寒武纪地层,成矿物质主要来自岩浆岩,部分来自地层。成矿时代为加里东晚期,结合矿化特征表明,该矿床成因类型属加里东期斑岩型钨矿床。加里东期花岗斑岩体及其接触带石英细(网)脉发育地段、黄铁绢英岩化蚀变和W-、Mo-Bi-Cu化探异常组合是重要的找矿标志。地球物理资料表明该区深部找矿空间大,地球化学资料亦表明该区找矿前景好,结合矿区成矿地质条件和矿床特征推测该矿床具有寻找大中型以上规模钨矿床的找矿潜力。     

闽西小康锰银多金属矿地质特征及找矿方向

小康锰银多金属矿受下三叠系溪口组地层、断裂构造破碎带和花岗斑岩接触带控制，氧化锰（银）矿床属“淋积型”，含锰层经热液叠加改造和风化淋滤后在层间断裂破碎带中富集成矿；铜铅锌矿体分布于酸性偏中性的花岗岩体外接触带中（部分为层状夕卡岩），呈浸染状赋于夕卡岩中或沿裂隙充填成矿。主要围岩蚀变有夕卡岩化和角岩化。该矿床从上至下具Mn（Fe）-Ag，Pb，Zn—Cu，Pb，Zn的垂直分带规律。     

东秦岭大别山段斑岩型钼(钨、铜)矿床地质特征

东秦岭大别山段矿化中酸性小岩体集中分布在东秦岭钼(钨、铜)矿带东段,呈带状沿深大断裂两侧分布,受构造控制明显.已发现主要钼矿床属斑岩型,成因多与中生代中酸性花岗质斑岩有关.根据斑岩型钼(钨、铜)矿床地质特征,通过控岩控矿构造、围岩蚀变、矿体特征、矿石物质组份及其成矿机制等方面的研究,把东秦岭大别山段斑岩钼(鸽、铜)矿划分为浅成-超浅成斑岩钼(铜)矿床,中-深成斑岩-夕卡岩钼(钨、铜)矿床两种类型.     

Chemical alteration of the oceanic crust

The alteration of the upper oceanic crust through sea water-basement rock interaction produces different and distinct alteration zones with increasing depth. The zonation generally shows a consistent worldwide pattern.The uppermost basement is influenced by oxidative sea water-basalt alteration at low temperatures and high water/rock ratios. With increasing crustal depth or even in a single pillow the temperatures rise, the water/rock ratios become lower, the redox and pH values normally decrease, and the oxidative zone is followed by a non-oxidative one. Below these zones the basement has suffered high-temperature alteration under reducing and acidic conditions.This results in chemical modifications of the rocks by the addition or leaching of certain elements, and has also consequences for the composition of sea water.From our own data and data presently available in the literature I summarize the mineralogical and geochemical characteristica of sea water alteration processes affecting the oceanic crust.

---

Zusammenfassung Die chemische Veränderung der oberen ozeanischen Kruste durch Gestein/Meerwasser-Interaktionen produziert verschiedene und unterscheidbare Alterationszonen die von der Krustentiefe abhängig sind. Diese Zonierung zeigt weltweit vergleichbare Muster.Das oberste Basement wird von einer niedrig temperierten oxidativen Meerwasseralteration beeinflußt. Mit zunehmender Krustentiefe steigen die Reaktionstemperaturen an, die Redox- und pH-Werte werden kleiner, d.h. nichtoxidative Alterationsvorgänge dominieren. Unterhalb dieser Zonen wird die ozeanische Kruste überwiegend von reduzierenden und sauren Hydrothermallösungen alteriert.Im Verlauf der Seewasser/Basalt-Reaktionen werden die Gesteine mineralogisch und chemisch verändert, indem verschiedene Elemente aus den Basalten herausgelöst und wiederum andere aufgenommen werden. Diese Vorgänge haben auch für die Zusammensetzung des Meerwassers drastische Konsequenzen.Mit Hilfe publizierter aber vor allem mit eigenen Daten werden die mineralogischen und geochemischen Charakteristika der unterschiedlichen Alterationsprozesse zusammengefaßt dargestellt.

---

Résumé L'altération de la partie supérieure de la croûte océanique sous l'action de l'eau de mer engendre plusieurs zones distinctes qui se succèdent de haut en bas. Ce zonage présente d'ordinaire une extension mondiale.La partie supérieure de la croûte est affectée d'une altération oxydante de basse température du basalte. Vers le bas, parfois même au sein d'un même pillow, la température s'élève, la quantité d'eau décroît, le potentiel redox et le pH diminuent, de sorte que la zone d'oxydation est suivie d'une zone non oxydante. En-dessous de ces deux zones, les roches ont subi une altération de haute température dans des conditions acides et réductrices.Il en résulte des changements de la composition chimique des roches par apport ou par lessivage de certains élements, ainsi qu'une modification de la composition de l'eau de mer.A partir des données de la littérature et surtout de mes propres observations, je présente une synthèse des caractères minéralogiques et géochimiques des divers processus de l'altération sous-marine.

---

, . . . , pH , .. , . . , , , . . , . . , .

     

Experimental aqueous alteration of the Allende meteorite under oxidizing conditions: Constraints on asteroidal alteration

We have performed an experimental study of the aqueous alteration of the Allende CV3 carbonaceous chondrite under highly oxidizing conditions, in order to examine the alteration behavior of Allende’s anhydrous mineralogy. The experiments were carried out at temperatures of 100, 150, and 200 °C, for time periods between 7 and 180 days, with water/rock ratios ranging from 1:1 to 9:1. Uncrushed cubes of Allende were used so that the spatial relationships between reactant and product phases could be examined in detail. Scanning electron microscope studies show that in all the experiments, even those of short duration (7 days), soluble salts of Ca and Mg (CaSO₄, CaCO₃, and MgSO₄) precipitated on the sample surface, indicating that these elements are rapidly mobilized during alteration. In addition, iron oxides and hydroxides formed on the sample surfaces. The sulfates, carbonates, and the majority of the iron-bearing secondary minerals are randomly distributed over the surface of samples. In some instances the iron oxides and hydroxides are constrained to the boundaries of altering mineral grains. Transmission electron microscope studies show that the FeO-rich olivine in the interior of the samples has altered to form interlayered serpentine/saponite and Fe-oxyhydroxides. The degree of alteration increases significantly with increasing water/rock ratio, and to a lesser extent with increasing duration of heating. The serpentine/saponite forms both by direct replacement of the olivine in crystallographically oriented intergrowths, and by recrystallization of an amorphous Si-rich phase that precipitates in pore space between the olivine grains. The alteration assemblage bears many similarities to those found in altered carbonaceous chondrites, although in detail there are important differences, which we attribute to (a) the relatively high temperatures of our experiments and (b) comparatively short reaction times compared with the natural examples. In terms of mineral assemblage, our experiments most closely resemble alteration in the CI chondrites, although the degree of alteration of our experiments is much lower. CI chondrites contain serpentine/saponite intergrowths and veins of Ca-sulfate and Ca-carbonate as well as the Fe-oxyhydroxide, ferrihydrite. However, the phyllosilicate phases formed in our experiments are somewhat coarser-grained than the finest phyllosilicate fraction present in CI chondrites, suggesting that alteration of the CI chondrites occurred at lower temperatures. In terms of mineral assemblage, our experiments also appear to come close to matching CR chondrites, although we infer that CR alteration probably occurred at temperatures <100 °C, based on the very fine-grained size of phyllosilicates in CR matrices.     

Fluid fluxes during low-temperature alteration: implications of multi-style alteration assemblages from the Welsh Borderland,UK

Localized (domainal) low-temperature alteration may indicate variations in the chemistry of alteration fluids and/or discrete fluid flow paths during metamorphism. Occurrences of epidote- and pumpellyite-dominated domains are often used as evidence for large fluxes of Ca-rich fluids. However, comparative studies of two domainal alteration styles from basaltic to andesitic lavas and volcaniclastic rocks at Builth Wells, Wales, UK suggest that such interpretations cannot be applied universally. Here, only one set of domains can be attributed to large fluxes of Ca-rich fluids. In contrast, the second set of domains formed where the host rock supplied the necessary Ca, and fluid/rock ratios were relatively low. These domains are hosted by rocks which show a Caledonian regional metamorphic imprint, characterized by the alteration assemblage albite+chlorite+titanite±prehnite±pumpellyite±calcite±muscovite±quartz (considered to have formed at c. 200°C and ≤2.5 kbar). Type 1 domains lie along fluid channelways, such as veins. Pumpellyite is the dominant secondary mineral, but the alteration assemblage is variable with pumpellyite±prehnite±calcite±titanite±chlorite (±quartz). The domains formed at temperatures of 130–230°C during Ordovician hydrothermal activity, before the peak of regional metamorphism. In contrast, Type 2 domains are not associated with obvious fluid channelways. A central prehnite-dominated zone typically has a rim with the assemblage pumpellyite+calcite±prehnite±chlorite±titanite±K-rich phyllosilicate. These domains probably formed from pelitic xenoliths which contained a volcaniclastic component at temperatures of 130–230°C and at relatively low fluid/rock ratios. However, the timing of domain formation is uncertain. Pyrobitumen, in veins and disseminated throughout the rock, may have influenced the formation of both types of domain by stabilizing pumpellyite in preference to epidote and causing metamorphic calcite formation through the release of CO₂ to the alteration fluids. © 1996 John Wiley & Sons, Ltd.     

Blueschist alteration during serpentinization

The petrogenesis of Franciscan-type blueschists is controversial or paradoxial in regard to the possible significance of the serpentinite-blueschist association, the isochemical vs. allochemical character of blueschist metamorphism, the significance of high pressure mineralogy, and the physical-geologic-tectonic conditions existing during metamorphism. A model for blueschist alteration during serpentinization is presented that departs from conventional treatments of metamorphism because the reaction path rather then the thermodynamically lowest energy state is considered to be a controlling factor.Alteration of ultramafic rocks to serpentinites requires oxidation of iron in the rock and selective withdrawal of water from saline pore fluids derived from surrounding eugeosynclinal rocks. Pore fluids become concentrated and chemically reducing in the vicinity of serpentinites.The activated pore fluids may react with surrounding rocks via reactions that include a reduction step. The pore fluids may also affect the reaction path through surface chemical effects existing between mineral surfaces and/or growth units and the reducing pore fluid. The degree of polarization of oxygen ions in the silicate structural types, a function of polymerization and aluminum substitution, may control the surface effects and result in the preferential growth of chain silicates, and, more generally, of silicates with low amounts of tetrahedral aluminum.The ratio Mg⁺²/H⁺ in the pore fluid can change during serpentinization depending on the extent to which magnesium is lost from the original mafic rock. This ratio may be an important control on the growth of jadeite vs. glaucophane in the presence of excess quartz.The reduction reactions and those involving conventional fluid-solid equilibria cause a change in pore fluid chemistry as the reaction proceeds. Such reactions may explain short-range metasomatic transitions observed in some blueschists. The kinetic controls involving surface chemical effects are catalytic and may explain isochemical phenomena.The ultimate drive for the process is the large negative free energy change of serpentinization that results when ultramafic rocks are emplaced in eugeosynclinal rocks with which they are not in equilibrium. Removal of this overwhelming disequilibrium may induce secondary disequilibrium and activation of pore fluids, producing Franciscan-type blueschists.     

Geochemical alteration associated with the Selbaie copper-zinc-silver deposit

The object of this study is to establish the nature of geochemical alteration in the wall rocks of the Selbaie Cu-Zn-Ag deposit, and to ascertain whether bedrock geochemistry could be applied in exploration for deposits of this type. The Selbaie Cu-Zn-Ag deposit, in northwestern Quebec, is atypical of base-metal deposits in the Canadian Shield, as mineralization occurs in epigenetic veins and as disseminations in volcanic wall rocks, rather than as syngenetic massive sulfide bodies which have been the focus of extensive comparable studies in the past. The deposit comprises three mineralized zones in felsic tuffs and quartz porphyry. Two of these, the A1 and A2 zones, which are the focus of the present study consist of quartz-carbonate veins containing chalcopyrite, sphalerite, and pyrite, and accessory sulfide minerals. The B zone is not considered in this study. Samples of drill core were collected from sections crossing the A1 and A2 zones and analyzed for total Si, Al, Fe, Mg, Ca, Na, K, Ti, Mn, P, and S by X-ray fluorescence, and for aqua-regia-extractable Cu, Zn, Ni, Pb, Fe, and Mn by atomic absorption. Although the distribution of individual element concentrations is clearly related to bedrock type, rocks proximal to mineralization have higher SiO₂, Fe₂O₃, Cu, Zn, Fe, and S contents, and lower Al₂O₃ and K₂O contents, than rocks more distal from mineralization. MgO content shows an irregular distribution and may also increase toward mineralization. CaO and Na₂O contents are very low in all pyroclastic rocks.In order to take into account the effect of bedrock type, linear regression analysis was performed on the data to estimate the normal concentration of individual elements using SiO₂ contents as the predicted variable. Spatial distributions of residual values of element concentrations indicate that rocks close to mineralization have higher residual Fe₂O₃, Cu, Zn, Pb, and Fe contents, and lower residual Al₂O₃ and K₂O contents, compared to rocks more remote from mineralization. These distribution patterns are clearer than in the case of the single-element data but variations between element responses still exist in some instances. In an attempt to overcome the variation in patterns revealed by some element distributions, discriminant analysis was undertaken to see whether mineralized areas could be distinguished on the basis of an element association. Discriminant functions were calculated for data from areas adjacent to mineralization, and from areas remote from mineralization. Areal distribution of discriminant scores outlined an anomalous area extending up to 200 m beyond the mineralization. Petrographic studies of selected samples correlated high SiO₂ and low Al₂O₃ content with silicification in the most altered rocks adjacent to mineralization. High Fe₂O₃, MgO, and extractable Fe concentrations were found to occur in chlorite- and carbonate-rich zones. Samples rich in S, Cu, Zn, and b, and to a lesser extent Fe, were characterized by the presence of sulfides. High concentrations of Al₂O₃ and K₂O relative to that of SiO₂ are typical of sericitization. On this basis, the results demonstrate that anomalously high or low concentrations of element associations, revealed by discriminant analysis, occur in large coherent zones exceeding the size of the deposit. The procedure is potentially useful as an exploration guide for epigenetic disseminated and vein-type base-metal styles of mineralization as well as the syngenetic massive sulfide type of deposits that have been extensively studied in the past.     

钱家店铀矿床含矿建造后生改造作用探讨:来自蚀变特征及地球化学的证据

基于开鲁盆地钱家店铀矿床含矿砂岩的偏光显微镜、扫描电子镜显微镜下观察以及元素地球化学分析,探讨了该砂岩型铀矿的形成过程.镜下观察结果显示,该矿床矿石中存在5种矿物蚀变作用类型:高岭石化、褐铁矿化、碳酸盐化、重晶石化和水云母化;钻孔伴生元素特征表明,钱家店部分铀矿体在初次形成后,可能又遭受后期流体叠加改造作用;元素迁移特征表明,矿区总体可能经历了两期不同性质的成矿流体,前期流体导致矿化砂岩的形成,后期流体在此基础上叠加改造,使铀再次富集成高品位铀矿石.综合前人研究资料,认为钱家店铀矿床经历三阶段成矿流体作用:第一阶段为同生沉积铀成矿;第二阶段为油气/热液改造叠加成矿;第三阶段为层间氧化铀成矿.     

Assessing sediment regime alteration of the upper Yangtze River

Employing the histogram matching approach, the sediment regime alteration of the upper Yangtze River was assessed and its possible causes and environmental influences were discussed. Daily sediment load and flow data from 1950 to 2008 were collected from Yichang hydrometric station. The annual sediment load series was segmented by heuristic segmentation algorithm in 1986 and 2003, and the multi-year mean values of the three phases were 5.28 × 10⁸, 3.89 × 10⁸ and 0.57 × 10⁸ t, respectively. One change point was found by cross wavelet transform in 2003 when the cross wavelet power became insignificant, which indicates the interruption of the common annual cycle of the sediment load and flow series. The sediment regime from 1986 to 2002 was altered by a total of 41 % compared with the regime from 1950 to 1985. It may be mainly attributed to numerous dams constructed in the tributaries, the Gezhouba Dam constructed in the mainstream, and land use and land cover change, e.g., the increased grassland with a coverage density larger than 50 %. The sediment regime alteration after 2003, assessed to be a total of 83 %, may be mainly attributed to the Three Gorges Reservoir. It breaks the natural process of sediment transport, reduces sediment concentration and releases clear water to the downstream which may result in some environmental problems, e.g., limited nutrients availability, river bed erosion, benthic habitat destruction, etc. The assessment of sediment regime alteration may provide some references for the environmental management and conservation of the Yangtze River.