泰国湾西部表层沉积物自生矿物分布及组成

Generation, morphology, and distribution of authigenic minerals directly reflect sedimentary environment and material sources. Surface sediments were collected from the western Gulf of Thailand during 2011–2012, and 159 samples were analyzed to determine detrital minerals. Authigenic minerals, including siderite, pyrite, and glauconite, are abundant whereas secondary minerals, such as chlorite and limonite, are distributed widely in the study area. Siderite has a maximum content of 19.98 g/kg and appears in three types from nearshore to continental shelf, showing the process of forming-maturity-oxidation. In this process, the Mn O content in siderite decreases, but Fe_2O_3 and Mg O content increase. Colorless or transparent siderite pellets are fresh grains generated within a short time and widely distributed throughout the region; high content appears in coastal area where river inputs are discharged. Translucent cemented double pellets appearing light yellow to red are mature grains; high content is observed in the central shelf. Red-brown opaque granular pellets are oxidized grains,which are concentrated in the eastern gulf. Pyrite is mostly distributed in the central continental shelf with an approximately north–south strip. Pyrite are mainly observed in foraminifera shell and distributed in clayey silt sediments, which is similar to that in the Yangtze River mouth and the Yellow Sea. The pyrite in the gulf is deduced from genetic types associated with sulfate reduction and organic matter decomposition. Majority of glauconite are granular with few laminar. Glauconite is concentrated in the northern and southern parts within the boundary of 9.5° to 10.5°N and is affected by river input diffusion. The distribution of glauconite is closely correlated with that of chlorite and plagioclase, indicating that glauconite is possibly derived from altered products of chlorite and plagioclase. The K_2O content of glauconite is low or absent, indicating its short formation time.     

Sediments on the continental shelf and slope between Napier and castlepoint,New Zealand

Sediments from the seabed off the eastern side of the North Island, New Zealand, are divided into 12 facies on the basis of grain size and mineralogy of the sand fraction. The facies are grouped into three types; modern detrital sediments, relict detrital sediments, and non‐detrital sediments. The sediments are described in terms of a modified Wentworth grain‐size scale and a modified Folk sediment classification.

The modern detrital sediments range from fine sand near the shore to clayey fine silt on the lower slope. At most places they are bimodal, probably because floes and single grains are deposited together. The relict detrital sediments, which include sands and gravels, occur where deposition is slow on the inner continental shelf and near the shelf edge. Those near the shelf edge include Last Glacial sandy muds that have been winnowed and mixed with Holocene volcanic ash and glauconite. The non‐detrital sediments, which contain forarninifera, volcanic ash, and glauconite, but no detrital sand, occur on anticlinal ridges on the continental slope. In places they overlie muddier sediment deposited during the last glaciation when the sources of river‐borne detritus were nearer than at present and when mud was deposited more rapidly on the ridges than at present.     

The distinctive compositional evolution of glauconite in the Cretaceous Ukra Hill Member (Kutch basin,India) and its implications

An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of glauconite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of glauconite pellets indicate an ‘evolved’ stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al^3+-Fe³⁺ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K₂O as well as Fe₂O₃ contradicts the two popular theories, ‘layer lattice’ and ‘verdissement’, and support replacement origin of glauconite in a high a_Si+ and high a_K+ pore water environment. Incipiently formed glauconite records a marginal increase in K₂O content accompanied by release of Al₂O₃ and SiO₂ to form evolved glauconite pellets; those forming within quartz grains involve an addition of Fe₂O₃ (total) content during maturation. The minimal increase in K₂O content of incipiently formed glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K₂O and Fe₂O₃ (total) content of glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability.     

东海西北部陆架表层沉积物重矿物组合及其沉积环境指示

研究了东海陆架360个表层沉积物的碎屑矿物和粒度组成,利用R型聚类方法提取稳定重矿物和重矿物分异指数作为矿物分布规律的指示因子;根据快速聚类结果将重矿物组成分为3个区:东海陆架海侵体系域晚期残留砂体区、高位体系域晚期长江水下前三角洲和浙闽沿岸流泥质沉积区、高位体系域扬子浅滩沉积区。结合粒度参数和特征矿物分布、沉积物14C年龄对各区沉积环境进行讨论,确定陆架残留沉积和改造沉积的成因、长江水下三角洲和浙闽沿岸流泥质区的范围,以及对应不同海侵层序的矿物分异特征和物质"源-汇"关系。聚类分析虽能够指示同一物源碎屑矿物分布与沉积动力关系,但物源不同,聚类结果可能误导沉积环境分析。扬子浅滩表层砂体是在距今6~4和3~2 ka 的两个潮流沉积发育期形成的多期改造沙波沉积。     

南海南部大陆架的残留沉积

研究了南海南部大陆架的残留沉积物的粒度、石英砂表面结构特征、生物分布等，并指出残留沉积普遍遭受改造。按其早期的形成环境差异和改造作用不同，划分出加里曼丹－巴拉望残留沉积区和亚南巴斯－纳土纳残留沉积区。     

Sediment texture,distribution and transport on the Ayeyarwady continental shelf,Andaman Sea

The Ayeyarwady continental shelf is a complex sedimentary system characterized by large sediment influx (> 360 million ton/yr), a wide shelf (> 170 km), a strong tidal regime (7 m maximum tidal range), and incised by the Martaban Canyon. Grain size distribution on the Ayeyarwady shelf reveals three distinct areas in terms of sediment texture (i) a near-shore mud belt in the Gulf of Martaban and adjacent inner shelf (ii) outer shelf relict sands and (iii) mixed sediments with varying proportions of relict sand and modern mud in the Martaban Canyon. The bulk of the terrigenous sediment discharged by the Ayeyarwady River is displaced eastwards by a combination of tidal currents and clockwise flowing SW monsoon current and deposited in the Gulf of Martaban resulting in shoaling of its water depths. Part of the sediment discharge reaches the deep Andaman Sea via the Martaban Canyon and the rest is transported westward into the Bay of Bengal by the counter-clockwise flowing NE monsoon currents.     

台湾海峡沉积物中海绿石的矿物学与分布特征

本文研究台湾海峡表层沉积物中海绿石的矿物学特征，分布格局及富集的沉积环境。结果表明，海峡海绿石系高硅富铁的含水硅盐矿的，为二八在体向三八面体过渡型结构类型，具有现代海绿石性质。海峡东北部，中部主要分布黑色颗粒海绿石，南部为灰绿色生物状海绿石。     

冲绳海槽中南部不同环境表层沉积物质来源

对冲绳海槽中南部3种不同沉积环境(东海外陆架、东海陆坡和冲绳海槽)表层沉积物进行了稀土等元素地球化学分析,结果显示,冲绳海槽和陆坡表层沉积物具有与台湾物质来源类似的稀土元素配分模式,La/Sm-Gd/Yb散点图也显示海槽和陆坡沉积物主要分布在台湾物源端元区,表明冲绳海槽中南部海槽和陆坡表层沉积物主要来源于台湾,而外陆架...     

南海北部陆架表层沉积物重矿物分布特征及物源意义

该文根据2007～2010年间对南海北部陆架采集的292个表层沉积物样品0．063～0．125mm粒级矿物的鉴定和分析结果,研究了该海域表层沉积物重矿物的分布特征和物质来源．结果表明：该海域矿物组成以轻组分矿物为主,平均质量百分数高达98．49％,重组分矿物的含量较低,平均值为1．51％,最高质量百分数仅为10．38％,共发现了60种重矿物．影响南海北部陆架表层沉积物重矿物的含量和分布的首要因素是水动力条件,其次是物质来源,其他因素如沉积环境、矿物自身的变质程度等也在一定程度上影响其分布特征．根据因子分析的因子荷载分布及南海北部陆架的地形地貌,研究区可划分为4个主要矿物组合区和2个亚区．分析结果表明,华南沿海的众多河流特别是珠江的入海泥沙是南海北部陆架表层沉积物的主要物质来源．海南岛东南部海底峡谷区处于相对稳定的沉积环境,胶结于有孔虫壳内的海洋自生黄铁矿含量丰富．     

Recent sediment accumulation and origin of shelf mud deposits in the Yellow and East China Seas

Modern (last 100 yr) accumulation rates of shelf mud deposits in the Yellow and East China Seas were investigated using the distribution of excess ²¹⁰Pb (²¹⁰Pb_ex) in sediment core samples. Compilation and merger of new and previously published data helped clarify sediment accumulation in these seas. The estimated accumulation rates, together with data of suspended sediment concentrations, provided findings on the sediment budget, origin, and transport pathway of the mud deposits. The overall accumulation distribution in the Yellow and East China Sea shelf revealed a general, cross-shelf decreasing trend along the sediment dispersal system away from the rivers, except for the South Sea (SSM) and southeastern Yellow Sea (SEYSM) mud patches found along the Korean coast. Notably, ²¹⁰Pb_ex activity profiles within the SSM and the SEYSM yielded a relatively high accumulation rate of 2-5 mm/yr, implying a sedimentation rate of 4-15 × 10⁷ tons per year in this coastal zone. Such an annual accumulation rate is about one order of magnitude greater than the total sediment discharge (6-20 × 10⁶ tons/yr) from Korean rivers, suggesting an additional offshore source. The distribution pattern of the well-defined suspended plume clearly showed the possible transport and exchange of fine-grained sediments between the ECS shelf and the coastal area of Korea, especially during winter. Such a high accumulation in Korean coastal areas is attributable to the sediments supplied from the mud deposit of the ECS (i.e., SWCIM), with origins in Chinese rivers. Therefore, the Korean coastal area may be an important sink for some of Chinese river sediments being transported from the south by the Yellow Sea Warm Current.     

Surficial sediments on the continental margin off the west coast of South Africa

A combination of climatic and oceanic factors has resulted in slow sedimentation rates on the continental shelf off the west coast of South Africa since Tertiary times. This has enabled a study to be made of the residual Late Tertiary, relict Pleistocene and Holocene sediments.Sediments on the continental shelf form rough belts parallel to the coast. Most of the coarse sediment is confined to the littoral zone and Holocene mud is concentrated at the base of a rocky nearshore platform. A veneer of Quaternary quartzitic sand seawards of the Recent mud belt wedges out onto a Tertiary erosion surface on the mid shelf. Residual glauconite and phosphorite sands derived by erosion during Tertiary sea-level fluctuations cover large parts of the mid shelf in the south. Most of the slope and parts of the outer shelf in the north are draped by Recent foraminiferal and coccolithophorid debris.     

Rare earth elements in bottom sediments of major rivers around the Yellow Sea: implications for sediment provenance

Rare earth elements (REEs) of 91 fine-grained bottom sediment samples from five major rivers in Korea (the Han, Keum, and Yeongsan) and China (the Changjiang and Huanghe) were studied to investigate their potential as source indicator for Yellow Sea shelf sediments, this being the first synthetic report on REE trends for bottom sediments of these rivers. The results show distinct differences in REE contents and their upper continental crust (UCC)-normalized patterns: compared to heavy rare earth elements (HREEs), light rare earth elements (LREEs) are highly enriched in Korean river sediments, in contrast to Chinese river sediments that have a characteristic positive Eu anomaly. This phenomenon is observed also in primary source rocks within the river catchments. This suggests that source rock composition is the primary control on the REE signatures of these river sediments, due largely to variations in the levels of chlorite and monazite, which are more abundant in Korean bottom river sediments. Systematic variations in ΣLREE/ΣHREE ratios, and in (La/Yb)–(Gd/Yb)_UCC but also (La/Lu)–(La/Y)_UCC and (La/Y)–(Gd/Lu)_UCC relations have the greatest discriminatory power. These findings are consistent with, but considerably expand on the limited datasets available to date for suspended sediments. Evidently, the REE fingerprints of these river sediments can serve as a useful diagnostic tool for tracing the provenance of sediments in the Yellow Sea, and for reconstructing their dispersal patterns and the circulation system of the modern shelf, as well as the paleoenvironmental record of this and adjoining marginal seas.     

Clay diagenesis in recent marine fecal pellets

Fecal pellets are ubiquitous in sediment collected from deep ocean ridge, continental shelf and fjord-type estuarine environments off the Canadian West Coast. Fecal pellets of the immature diagenetic stage are composed generally of the same mineral suite as the bulk sea-bottom sample; except that degraded biotite and/or illite has absorbed Fe and K to regrade into glauconite. These fecal pellets (<10 years old) contain 10 to 15% glauconite. Highly evolved monomineralic fecal pellets (e.g. glauconite, smectite) of such modern age show that diagenetic minerals commonly associated with burial can be produced by sediment-organism interactions.     

Characterizing the depositional settings for sedimentary organic matter distributions in the Lower Yangtze River-East China Sea Shelf System

Grain-size distributions, total organic carbon (TOC) and total nitrogen (TN) concentrations, and TOC/TN ratios (C/N) were analysed for surface sediments from the Lower Yangtze River-East China Sea (ECS) shelf system. Hierarchical cluster analysis of grain-size parameters (mode, mean, sorting, skewness and kurtosis) has been employed to characterize grain-size compositions. The results suggest there are five grain-size compositional types (type-I–V) that fingerprint distinct depositional conditions. In areas with high sedimentation rates, hydrological sorting preferentially enriches the fraction coarser than 6.4ø (12 μm) in shallow seafloor sediments (water depth<30 m) by transporting the finer fraction to the deeper seafloor (water depth>30 m), and thus forms grain-size compositional type-I (shallow) and type-II (deep). In the open shelf, where modern sediment supply is very limited, grain-size types-III–V are identified according to different winnowing intensity. Overall TOC contents significantly correlate with mud proportions, suggesting muddy sediments are the primary control on OM accumulation. However, de-association of terrestrial OM from fine sediments in the Estuary and the occurrence of presumably relict OM in the open shelf exert additional controls on OM dispersal and carbon cycling in the ECS. By considering geography, oceanography, sediment source, and the relation between sedimentation conditions and sedimentary OM distributions, we define six depositional settings: the lower river, the estuary, the coast, the offshore upwelling area, the erosional area, and the open shelf. These settings describe the sediment dispersal and associated organic matter cycling in the Lower Yangtze River-ECS shelf system.     

基于重矿物地球化学手段的南海东北部陆架沉积物物源研究

物源是研究大陆架沉积物搬运过程、重建陆架古环境以及海洋砂矿资源勘查的重要信息。然而,陆架砂质沉积物普遍经历过多次搬运、分选和混合,这给物源识别带来极大的困难。南海东北部陆架砂质沉积物分布广泛,本文首次采用单矿物化学方法对其物源进行了新的解析。研究区表层砂质沉积物中电气石与角闪石为优势重矿物,两者含量呈现此消彼长的关系。电气石和石榴子石的电子探针数据显示:珠江、韩江沉积物影响海域,火成岩成因的电气石占60%左右,其主要来源为区内广泛发育的燕山期花岗岩的风化产物;莲花山断裂带和长乐?南澳断裂带附近的南海东北部沿岸小河沉积物中变质岩成因的电气石含量显著增高,最高可达70%,其来源为区内与断裂带伴生的变质岩风化物;矽卡岩成因的钙铝榴石在南澳岛以东的陆架沉积物中发现最多,这与华南陆域矽卡岩的分布区吻合。综合分析认为,重矿物的矿物化学方法可以减少分选效应的影响,利用多种矿物的矿物化学分异可以获得多维的信息,为陆架沉积物的物源判定提供便利。     

渤海、黄海、东海沉积物中矿物组合的研究

本文对黄海、渤海、东海以及长江、黄河、辽河表层沉积物中的轻、重矿物进行了研究。分析资料表明,调查区内共有三种类型的矿物:陆源矿物、自生矿物和海底火山喷发形成的火山型矿物。根据轻、重矿物组合的差异,可把调查区分成8个矿物区。其物质来源主要为黄河与长江。黄河物质主要沉积在黄海、渤海;长江物质沉积在东海陆架区,而冲绳海槽则发现有海底火山喷发物质与浊流沉积。     

南海表层沉积类型与沉积作用若干特征

根据底质的粒度分析结果，编制了南海表层沉积类型图。把南海的表层沉积划分为１２种主要的类型，它们的展布与水深线的走势大体一致。大陆架表层沉积物主要由现代沉积、再造沉积、残留沉积和少量残余沉积组成。半深海—深海沉积中生物碎屑的组成和含量往往成为确定沉积类型的重要因素。受碳酸盐溶解作用的影响，随着水深增大，钙质与硅质生物碎清含量呈相互消长的关系，沉积类型因而不同。     

Identification of Pb sources in Yellow Sea sediments using stable Pb isotope ratios

Rapid economic developments in East Asian countries have inevitably resulted in environmental degradation in the surrounding seas, and concern for both the environment and protection from pollutants is increasing. Identification of sources of contaminants is essential to environmental pollution management. In this study, the provenance of anthropogenic lead (Pb), a major pollutant of Yellow Sea sediments, was determined for river mouth sediments, including those of the Changjiang, Huanghe, Han, and Geum Rivers, and for age-determined shelf core sediments through the measurement of Pb isotope ratios in the HCl-leached fraction using multi-collector inductively coupled plasma-mass spectrometry (MC ICP/MS). Anthropogenic Pb has accumulated in shelf core sediments since 1910, and its isotope ratios were estimated as 0.863–0.866 and 2.119–2.125 for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively, from the mixing relationships of the two endmembers. River mouth sediments exhibited enough distinction in anthropogenic Pb isotope ratios to be discriminated: 0.874 (2.144) in the Huanghe, 0.856 (2.129) in the Han, 0.857 (2.122) in the Geum, and 0.854 (2.101) in the Changjiang for ²⁰⁷Pb/²⁰⁶Pb (²⁰⁸Pb/²⁰⁶Pb), respectively. Although isotope ratios of geogenic Pb in sediments dating before 1910 showed narrow ranges (0.842–0.845 and 2.088–2.100 for ²⁰⁷Pb/²⁰⁶Pb and ²⁰⁸Pb/²⁰⁶Pb, respectively), distinct isotope ratios in each core permitted source identification of sediments in the Yellow Sea based on geographic locations and the geogenic Pb of each river. By comparing the isotope ratios of the estimated anthropogenic Pb to source-related materials, the provenances of anthropogenic Pb in Chinese river sediments were presumed to be Chinese coal or ore, which is also a major source of atmospheric particulate Pb. The anthropogenic Pb in the shelf core sediments in the northern Yellow Sea originated from northern Chinese cities such as Beijing and Tianjin through atmospheric pathways. Pb isotope ratios indicated that Pb in Korean river sediments was characteristic of local Korean ores.     

白令海和西北冰洋表层沉积物磁化率特征初步研究

为了准确解释环境磁学参数记录的极地古气候环境变化信息,本研究对白令海和西北冰洋61个站位的表层沉积物进行了高、低频质量磁化率(χ)、非磁滞磁化率(χARM)和磁化率-温度(k-T)分析,以探明该区沉积物中磁性矿物的种类、来源与搬运路径。结果显示,样品的χ具有明显的地域分布特征。白令海的χ值整体高于楚科奇海,并在育空河口外侧和圣劳伦斯岛南侧较高,向北和向西南方向逐渐减小。楚科奇海中东部陆架上表层沉积χ值高于阿拉斯加沿岸,而西北冰洋深海平原和洋脊区的χ值最低。χARM的变化趋势与质量磁化率相似,但频率磁化率的变化趋势与质量磁化率正好相反。k-T分析结果显示阿留申海盆沉积物中的铁磁性矿物以磁赤铁矿占主导,白令海陆架育空河口外侧和圣劳伦斯岛南北两侧为磁铁矿,白令海陆架西部和楚科奇海陆架中东部为磁赤铁矿和磁铁矿,楚科奇海阿拉斯加沿岸为黄铁矿,而西北冰洋陆坡、深海平原和洋脊区为胶黄铁矿和黄铁矿,但高纬度区沉积物中的胶黄铁矿含量更高。沉积物中磁性矿物的区域性分布受沉积物来源、洋流和底质环境等因素的控制。白令海和楚科奇海陆架磁赤铁矿来源于亚洲大陆,白令海陆架东部的磁铁矿来自育空河流域,阿拉斯加沿岸沉积物中的黄铁矿,应为阿拉斯加西北部陆源侵蚀来源的或早期成岩作用形成的,西北冰洋深海盆区的胶黄铁矿,为自生成因的。     

西北冰洋表层沉积物黏土矿物分布特征及物质来源

西北冰洋表层沉积物黏土矿物分析结果显示其黏土矿物组成的区域分布和变化具有明显的规律性:从楚科奇海到北冰洋深水区,随着水深的增加,蒙皂石和高岭石含量增高,绿泥石和伊利石含量降低。自西往东,伊利石结晶度值降低,化学指数升高。根据Q型聚类分析获得的黏土矿物组合特征,结合周缘陆地的地质背景、河流及洋流情况,对研究区进行了黏土矿物组合分区,讨论了其黏土矿物来源。楚科奇海表层沉积物黏土矿物组合在靠近阿拉斯加一侧海域以Ⅰ类为主,靠东西伯利亚海一侧主要有Ⅱ类、Ⅲ类和Ⅳ类,中部主要为Ⅵ类,主要是西伯利亚和阿拉斯加的火山岩、变质岩以及一些含高岭石的沉积物以及古土壤等,经风化、河流搬运入海,在北太平洋的3股洋流及西伯利亚沿岸流的作用下沉积形成的。西北冰洋深水区表层沉积物的黏土矿物组合以Ⅰ类和Ⅴ类为主,表明其沉积物来源为欧亚陆架和加拿大北极群岛周缘海域的海冰沉积和大西洋水体的搬运以及加拿大马更些河的河流物质输入。