克里雅河沿线沙丘沉积物石英砂表面特征分析

对沙漠内部典型河流沿线沙丘石英颗粒表面微形态特征的系统研究尚少。沿塔里木盆地南缘克里雅河下游丹丹乌里克、喀拉墩、圆沙古城、北方墓地及其北部塔里木河一带的沙丘顶部采到5件表沙样品。扫描电镜观察172颗经能谱挑选的石英颗粒表面微形态,筛析法测定5件样品的粒度。结果表明:1）丹丹乌里克样品以极细沙为主,其余均以细沙为主,各样品几乎不含黏土;2）样品磨圆度特征以次棱和次圆状为主,圆状很少,未见棱状特征,次棱状与次圆状特征之间消长关系显著,沙漠南北边缘样品的次棱状特征出现频率较腹地高;3）颗粒中V形坑频率呈现出沙漠边缘较高腹地低的特征,而沙漠边缘的化学作用结构特征低于腹地。石英砂表面特征结构以机械作用为主,同时伴生化学环境作用特征,可认为克里雅河下游沙物质包括了河流、冰川与戈壁成因及风输送而来的颗粒;颗粒表面特征总体新鲜,沙丘应较年轻。纵穿塔克拉玛干沙漠沉积物样品的表面微形态观察与粒度测定,为该地区沉积环境分析与沙丘砂溯源研究增添了新数据。     

大连长兴岛砂质沉积物粒度分布与石英表面结构特征研究

文章对位于渤海东缘的长兴岛地区发现的、以互层形式存在的黄土与砂土沉积剖面各层样品进行粒度分析与石英颗粒扫描电子显微镜观察,阐明了研究区沉积物的沉积特征,并探讨了物质来源与沉积环境。研究结果表明,长兴岛砂质沉积剖面上层黄土沉积（CXD5、CXD7）以粉砂为主,粒度分布频率曲线呈双峰分布且石英颗粒表面形态兼具风成与水成特征,推断其物质来源以近源为主,远源为辅;下层砂质沉积（CXD1、CXD2）粒度以中细砂为主,且石英颗粒表面水成特征明显,推测为近源物质搬运沉积;中间层（CXD3、CXD4和CXD6）粉砂含量显著增加,中细砂含量减少,且石英颗粒的硅质再沉淀作用显著,呈现过渡特征。研究结果表明,长兴岛砂质沉积物剖面存在砂层与黄土层相间分布的特征,且沉积环境以近源为主、远源为辅,为典型的陆架沙漠化沉积环境特征。

     

昌黎海岸风成沙丘砂组构特征及其与海滩砂的比较

对昌黎海岸沙丘砂进行薄片统计,重砂矿物分析,电镜扫描,粒度分析及与海滩砂的对比研究发现,沙丘砂在物质组成、颗粒形态、石英砂表面结构特征和粒度特征方面均继承了海滩砂特征,不过,海滩砂中也有沙丘砂的某些特征,反映了两者沉积的混合。这是由于向岸风和离岸风共同作用的结果。     

云南思茅盆地景谷地区下白垩统曼岗组风成砂岩沉积学特征及其古气候意义

本文通过野外剖面的观察和实测,室内薄片鉴定、阴极发光分析、粒度分析、扫描电镜及能谱测试分析,研究了云南思茅盆地景谷地区下白垩统曼岗组风成砂岩沉积学特征,详细了解了风成砂岩的发育特征,以期为研究区白垩纪古气候研究提供新的资料,为我国钾盐勘探提供一定的地质依据和新的思路。研究结果表明:1研究区曼岗组主要出露一套中—细粒石英砂岩、岩屑石英砂岩,发育中—大型交错层理、平行层理,碎屑颗粒分选中等-好,以次圆状-圆状为主,孔隙不发育,杂基含量少;2曼岗组中段发育具平行层理的石英砂岩,粒度分布呈双众数,带状分布,石英颗粒为浑圆状,颗粒表面见Fe、Mn质薄膜,颗粒表面具明显的碟形坑等特征,属于典型的风成砂岩,初步判定其沉积环境为风成沙丘和丘间沉积;3景谷地区下白垩统曼岗组风成砂岩,整体表现为干热型气候,曼岗组中段为丘间沉积,曼岗组上段和下段为沙丘沉积。其在搬运沉积成岩过程中经历了强烈的物理、化学风化作用,整体表现为氧化环境,风力较大,风速稳定,持续时间长。此外,可能还经历了一段时期的湿润性气候环境,这可能与大气降水、大气环流带的迁移,以及白垩纪海侵作用等有关。     

南京周家山下蜀黄土石英颗粒特征及其物源意义

下蜀黄土的成因和物源一直是学术界研究的热点。对南京周家山下蜀黄土的石英粒度和石英表面微结构进行分析,结果显示:粉砂粒级石英颗粒（5~50 μm）占绝对优势;<20 μm组分平均含量为42.76%,<30 μm组分平均含量为62.98%;粒度分布曲线和累积曲线总体具有颗粒偏细,呈正偏态,分选较差,峰形尖锐,双峰曲线不对称的特征;粒级-标准偏差曲线呈“双峰”分布,两个明显的标准偏差峰值分别出现在7.962 1 μm和39.905 2 μm。石英颗粒表面形态主要以次棱角状为主;表面机械结构具有丰富的蝶形坑、曲脊、贝壳状断口,部分表面出现平行节理面、V形坑;不同粒级组分表面形态和机械结构特征存在差异。分析表明,南京周家山下蜀黄土属典型风成成因堆积物,是多源区物质高度混合搬运堆积的结果。     

福建长乐海岸横向前丘表面粒度分异研究

在我国横向海岸沙丘分布的典型地区之一——福建长乐海岸,选择典型的横向前丘,按与横向前丘走向相垂直方向,分三个采样断面近等间距地采集了共81个沙丘表面沉积物的粒度样品,通过对采集样品平均粒径、分选系数、偏度和峰态等粒度参数的计算与分析,研究横向前丘表面的粒度分异特征。结果表明,福建长乐海岸横向前丘表面粒度的总体特征为细沙、分选较好、近对称和中等峰态,符合海岸沙丘粒度一般规律;长乐海岸横向前丘表面的粒度参数在沙丘表面不同部位基本一致,整个沙丘表面的粒度没有明显差别;粒度无明显差异的分布模式应是该区域风向交替变化的季风、强劲风力的台风、平缓的地势、沙丘高度不够、植被覆盖较好等作用的结果。     

基于SEM的辽南红色风化壳石英颗粒化学成因特征分析

石英颗粒表面形态特征广泛应用于古气候与古环境的重建。本研究选取辽南地区3个红色风化壳剖面,运用扫描电镜对其石英颗粒表面化学成因特征进行分析。然后根据化学成因特征构建化学作用度函数并建立量化指标,以揭示气候因子对石英颗粒表面改造的影响,在此基础上分析辽南地区红色风化壳发育特征的空间差异。结果表明：石英颗粒表面化学成因的特征以代表湿热气候的高能化学环境为主,指示风化壳在形成过程中经历了湿热的气候环境;将石英颗粒表面化学作用度与化学蚀变指数(CIA)进行比较,两者具备较强对应关系,且变化趋势呈现出很好的同步性,具有较强拟合性,进一步证明了石英颗粒表面化学作用度对气候环境的指示作用;对比各剖面化学作用度,剖面之间呈现出一定的差异性,从整体来看,辽南中部红色风化壳发育程度最高,东、西部红色风化壳发育程度次之。

     

甘肃兰州黄河北岸疏松砂岩成因

广泛分布于甘肃兰州黄河北岸红城以东至皋兰以西一带的桔红色疏松砂岩体几乎全由石英颗粒组成,对其研究不仅具有较高的经济价值,而且对于了解中国西北地区干旱环境演变具有极其重要的意义。长期以来,该层砂岩的成因问题一直备受中外地质学家的关注。为此,针对该层疏松砂岩,通过野外沉积构造描述、室内颗粒分析试验及扫描电镜分析等方法,分别从沉积构造、粒度及石英颗粒表面形态特征等方面对其成因进行分析。研究结果表明,兰州黄河北岸水阜乡至曹家湾一带疏松砂岩水平层理沉积特征明显,砂岩粒度累积曲线具有典型水成特性,石英颗粒表面可见比较发育的贝壳状断口及因溶蚀作用而导致的鳞片状剥落等水下沉积特征;朱家井至红城一带疏松砂岩中风成板状斜层理沉积特征明显,其粒度累积曲线具有典型风成特性,石英颗粒表面可见比较发育的麻面、蝶形坑等风成特征。该层砂岩并非单纯的风成或水成,其成因具区域性。     

闽南-台湾浅滩陆架沉积砂中石英颗粒表面的微结构

石英颗粒表面微结构的研究是随着电子显微镜应用到地质学上而发展起来的。近年来利用扫描电镜观察石英颗粒表面形态特征及差异来研究沉积物物质来源、搬运方式和沉积环境已在我国开展起来。本文是在对闽南-台湾浅滩陆架的地形、沉积物粒度研究基础上,用JSM-50A扫描电镜观察、研究石英颗粒表面微结构时,发现调查海区的(中砂)沉积物中的石英颗粒具有各种微结构,反映特有的沉积环境。     

西宁黄土石英颗粒表面结构与黄土物质来源探讨

利用电子扫描电镜分析了西宁黄土地层中的石英颗粒表面形态和机械结构特征,发现近1.2Ma以来西宁黄土石英颗粒形态以尖棱角-棱角为主,颗粒表面具有典型的剪切断口或大贝壳状断口或平行擦痕,且比例较高;有些颗粒表面还具有V形坑、水下磨光面,这类颗粒以次圆状为主,这些信息指示出,西宁黄土物质不是主要来源于沙漠环境,而是来源于青藏高原第四纪冰川和冰缘作用区.     

The soils on the calcareous sand dunes southeast of South Australia

 The properties of soils on previously dated sand dunes from Robe to Naracoorte in South Australia were examined. In these areas younger sand dunes are composed of fresh sand, but older sand dunes are composed of calcarenited sand. The soils on the sand dunes developed successionally by the age of sand dunes. The soil properties of these sand dunes differ depending on the ages of the sand dunes. The properties of sand particles in soils are as follows: (1) On the sand dunes of 4300 years B.P., A/C profile developed (Rendzina). On the sand dunes older than 125 000 years B.P. and on the plateau of Tertiary limestone, soil profiles of A₁/AB/B/C on the sand dunes of 83 000 years B.P. and A₁/A₃/B₁/B₂/C (Terra rossa) are well developed. (2) Within the sand of A/C horizons of the sand dunes with the age of 4300 year B.P., the calcite grain content is about 64%, and the quartz content is about 35%. Within the B horizons of soils on the dunes from 83 000 years B.P. to 347 000 years B.P., the calcite grain content is only 1–2%; however, the quartz grain content is about 92%. In the B₂ horizons of soils on the dune of 690 000 years B.P. and on the Tertiary plateau, there are some calcite grains but the quartz grain content is about 96%. (3) The average size of quartz grains in the soils on the sand dunes from 4300 B.P. to 347 000 years B.P. is generally smaller, but the average size of quartz on the sand dunes of 690 000 year B.P. becomes larger and the grains are well rounded. On the Tertiary limestone plateau, the average quartz size becomes again smaller, and the grains are more rounded. (4) Fe_t in B₂ horizon of the soil profiles increases clearly corresponding to the age. Iron activity expressed by Fe_o/Fe_d also shows a close relation to the chronological sequence. The B horizon of the soil profiles shows a drastic decrease of Fe_o/Fe_d according to the age. Iron crystalinity, (Fe_d-Fe_o)/Fe_t, has a tendency for a positive relation with increasing age. Received: 1 June 1995 · Accepted: 4 December 1995     

The statistical analysis of the sand grain size distribution of Al- Ubay-lah barchan dunes,Northwestern Ar-Rub-Alkhali desert,Saudi Arabia

The paper analyses the statistical parameters of the sand grain size distribution of Al-Ubaylah barchan dunes applying the sieving technique and Folk and Ward, and Trask's equation. The results of the sieving analysis divulged that nearly over 90% of the sand particles fall in the size ranging between 1.50ø and 3.ø. Insignificant amount of sand grains also fall in the size ranging from 0.0ø to 1.50ø and from 3.0ø to 4.0ø respectively. The statistical analysis reveals that the sand is characteristically fine grained, moderately to moderately well sorted with an average diameter of 2.4ø and a standard deviation of 0.64ø. The sand distribution is positively fine skewed and mesokurtic to leptokurtic in nature. No significant variation in the statistical parameters (median, mean, sorting, skewness and kurtosis) of the sand grains samples used in this research is detected. The sand grain size distribution of all the samples can also be considered symmetrical and unimodal in nature. Those abovementioned characteristics are found to be nearly similar to that of other Saudi dune deserts. The miscroscopic investigation undertaken by this researcher displays that quartz represents often more than 99% of the samples. Felsic, mafic and calcium carbonates minerals represent less than 1% of the mineralogical constituents. The sand grains are subrounded to subangular and iron and calcium carbonates coated.     

Variations in the surface texture of suspended quartz grains in the Loire River: an SEM study

Statistical size distribution and scanning electron microscopic studies of suspended sand grains in the Loire River at Montjean, France were carried out over a period of a year (hydrological cycle) to discern seasonal variations. The sand fraction in suspension is better sorted during winter (average mean = 0.69 mm, median = 0.65–0.95 mm, sorting value, σ= 1.1–1.35) and is dominated by quartzo-feldspathic minerals. During summer, on the contrary, this fraction is rich in mica minerals and is poorly sorted (average mean = 1.21 mm, median = 0.33–0.95 mm, sorting value, σ= 1.4–2.0). The grain size of the coarser fraction shows a tendency to increase with river discharge up to an optimum discharge of about 1000 m³ s^-1 and thereafter decreases. Scanning electron photomicroscopy of quartz grains from the suspended sand population indicates that both mechanical and chemical features occur. The former (conchoidal fractures, mechanical fractures and breakage) dominate in the samples collected near the water surface during winter floods and the latter (solution pits, vermicular features, silica flowers, neogene silica and diatoms) in the samples from the bottom during low summer flows. During summer, chemical action takes place on sediments prior to or upon their deposition. Sediments that are resuspended during winter floods undergo mainly physical processes (attrition/abrasion). Mixed surface features are, therefore, observed during average and low river discharge. Inheritance of these surface features from the source area is, however, not completely excluded. Thus, the history of quartz grains in suspension can be reconstructed from SEM exoscopic studies: therefore, it can be proposed that the fluvial quartz grain surface textures result from a combination of alternating chemical and physical processes.     

风成沉积物中不同粒径石英颗粒表面机械结构的变化特征

按搬运方式将风成石英颗粒分级,逐级测量并统计表面机械结构的类型、数量和大小,并计算其面积。发现悬移为主的颗粒表面结构的类型、数量最少,仅见少量不规则坑、V形坑,在颗粒表面分布面积最小;跃移搬运为主的颗粒表面结构类型最丰富,不规则坑、蝶形坑、V形坑、新月形坑、贝壳状断口大而深,在颗粒表面的分布面积最大;滚动搬运为主的颗粒表面结构数量最多,以小而浅的不规则坑为主,伴有Ⅴ形坑、贝壳状断口等,在颗粒表面的分布面积大小适中。不同搬运方式在石英颗粒表面形成的结构不同,撞击频率、颗粒大小、搬运速度共同影响表面结构的发育,高撞击频率、大粒径可以形成并承载更多的表面结构,大动能撞击可形成多种类且大尺寸的表面结构。在借助石英颗粒表面结构进行成因判别时需根据粒径大小选择相应粒级的石英颗粒表面结构特征组合,以及结构的数量、大小特征等进行综合判别。     

Sedimentological characteristics and morphology of the aeolian sand dunes in the eastern part of the UAE,a case study from Ar Rub' Al Khali

The Umm Az Zimul–Al Wijan area is located in the southeastern part of the UAE and covers about 1600 km². It is bounded to the east by the Oman Mountains and to the south and west by the extensive dune area of Ar Rub' Al Khali. Field investigation revealed the common occurrence of parallel to sub-parallel sand ridges with a general east–west orientation. Also present, but less frequent, are barchan, barchanoid and star dunes. Interdune areas are classified into four types that include: dolomite, mixed ancient sabkha and ophiolitic rock fragments, mixed sand sheet and ophiolitic rock fragments, and recent sabkha. The textural characteristics of the sand forming the dunes are unimodal with a modal class in fine sand size, moderately to very well sorted, positively skewed and mesokurtic. Quartz grains are mainly subrounded to subangular. The similarity in roundness properties in different dune types in the eastern province of the UAE seems not to be influenced by dune form. Based on the heavy mineral suites and the angularity of quartz grains, it is believed that the sand sediments are mostly derived from the ultrabasic rocks forming the ophiolitic sequence of the Oman Mountains, acidic rocks of Iran and from the coastal area.     

西藏札达盆地沉积物的石英砂表面特征及其环境意义

在扫描电镜下对札达盆地香孜组、古格组和托林组地层中的石英砂表面结构特征进行观察,三个组中石英颗粒外形磨圆度均不好,以棱角和次棱角状为主,结合区域地质认为,盆地的沉积物源距离盆地沉降区很近,为盆地周围的山地.其中香孜组的上部和中部冰川砂粒表面特征明显,认为是水体较浅冰缘区河湖相沉积环境;香孜组下部为湖泊水体较深的冰缘区河湖相沉积环境.古格组石英砂颗粒表面具有溶蚀坑和沟,属于低化学能的湖相沉积.托林组则表现出河流相沉积的特点.     

大型板状交错层理内部沉积物的分异

本文对取自长江上荆江三八滩大型板状交错层理内部同一细层不同部位的５个样品进行了粒度分析和矿物鉴定，结果表明，在同一细层内沉积物有明显的分异作用。细层中上部以中等粒径、低密度的颗粒为主，分选好。细层的下部和底部主要聚集沉积物的粗尾和细尾部分，因而分选较差。此外，密度较大的矿物亦趋于聚集在细层的底部。沉积物的这种分异主要是因为在沙波运移过程中矿物沿背流面发生重力分异且在背流面附近存在回流所致。大型板状交错层理内部沉积物的这种分异作用对认识其储集性能的层内非均质性有重要的意义