Sand and clay mineralogy of sal forest soils of the Doon Siwalik Himalayas

The peteromineralogical characterization of the soil was carried out for the 12 soil profiles exposed in the Shorea robusta dominated forests of the Siwalik forest division, Dehradun. The quartz was observed as the dominating light mineral fraction (64–80%) in all the profiles studied. Biotite, hornblende, zircon, tourmaline, rutile and opaques comprising of iron minerals constituted the heavy mineral fraction (20%). The mineralogy of both the sand and clay fractions revealed a mixed mineralogy. The clay minerals in the order of their dominance were vermiculite, illite, kaolinite and mixed layer minerals. The presence of vermiculite and illite in appreciable quantities indicates that these were synthesized from the K-rich soil solution, as orthoclase and micas were present in significant quantities in the sand minerals. The mineral suites identified in the study shows that the geological, climatological and topographical factors of the region collectively played a dominant role in their formation and transformation. After critical appraisal of the results, it may be deduced that the mineralogical composition, physicochemical properties and total elemental analysis of the soils do not show any deficiency of the bases and other plant nutrients in general. The inherent fertility of the soil is good as indicated by the sand and clay mineralogy of the soil and the biotite and feldspar together with the mica is an important source of nutrients for the vegetation in the soils of the Doon valley.     

Heavy minerals from the Siwalik formations of the northwestern Himalayas

The heavy-mineral assemblage of the Siwalik sequence consists of zircon, tourmaline, rutile, garnet, chlorite/chloritoid, staurolite, epidote, biotite, kyanite and sillimanite. The opaque fraction constitutes a sizable proportion of the heavies and includes magnetite, hematite, limonite, ilmenite, rarely pyrite and sporadic chromite. Staurolite is the marker for the Lower Siwaliks, the appearance of kyanite marks the base of the Middle Siwaliks while the Upper Siwaliks are characterized by the presence of sillimanite in addition to the heavy-mineral assemblage encountered in the Lower and Middle Siwaliks.     

Genesis and clay mineralogy of soils on different geomorphic surfaces in Mahan-Joupar area, central Iran

Soil genesis and clay mineralogy studies play an important role in sustainable soil and agriculture management. Soil properties are highly affected by geomorphic position. To study the physicochemical soil properties and clay mineralogy related to geomorphic surfaces, 12 representative pedons on different landforms in the Mahan-Joupar area, central Iran, were selected. Soil moisture and temperature regimes of the area were aridic and mesic, respectively. Rock and mantled pediments, alluvial fan, inselberg, plain, and transitional surfaces were among the different landforms studied. Alluvial fan was also divided into stable and unstable surfaces according to detailed field studies. Argillic horizon found in stable alluvial fan surfaces was attributed to the presence of a more humid paleoclimate in the history of the area. Coating of calcite on clay films observed by SEM showed that clay was illuviated in more humid periods of the past and then followed by calcium carbonate illuviation during arid climates. Smectite, kaolinite, chlorite, illite, and palygorskite clay minerals were identified by X-ray and SEM observations. Finally, a close relationship between the geomorphology and soil genesis and clay mineralogy was found in the area.     

The clay mineralogy of the Scottish Dalradian meta-limestones

The clay mineralogy of the Scottish Dalradian meta-limestones has been studied mainly by X-ray diffraction. In the samples from the north-east part of the Dalradian outcrop, which often show evidence of intense metamorphism, clay minerals found include saponite, regularly and irregularly interstratified smectite-chlorite, swelling chlorite, normal chlorite, illite and kaolinite. Limestones from the weakly metamorphosed South-West Highlands area contain only kaolinite, illite and chlorite. The genesis of the clay minerals is considered, particular attention being paid to the swelling minerals from the north-east region.     

不同气候带森林土壤粘粒矿物XRD物相分析

以我国7个不同气候带下的森林土壤为研究对象,从不同温度及降水对森林土壤的影响方面入手,通过野外取样和室内分析相结合的方法,测定其阳离子交换量、土壤颗粒组成、化学组成特征情况,进行选择性溶解分析,并使用X射线衍射分析方法,分析不同森林土壤粘粒矿物XRD物相特征,深入探讨在不同气候带下、受不同温度及降水影响的森林土壤的粘粒矿物的组成特点及含量变化.结果 表明,7种供试森林土壤除雾灵山外,其他森林土壤粘粒含量均达到30％以上,雾灵山为壤土,西双版纳为砂质粘壤土,其他森林土壤为粘壤土.7种供试森林土壤粘粒化学组成以SiO2、Al2O3和Fe2O3为主,Sa值大小顺序为蛟河＞漠河＞太白山＞雾灵山＞天童山＞西双版纳＞黄连山.由北到南随着温度及降水的增加,森林土壤的Sa值、Saf值呈逐渐减少的趋势,土壤风化程度增加.寒温带漠河、中温带蛟河、暖温带雾灵山、北亚热带太白山的粘粒矿物以2:1型伊利石为主,中亚热带天童山、南亚热带黄连山、热带西双版纳的粘粒矿物以1:1型高岭石为主.随着温度及降水的升高,伊利石含量呈现逐渐减少的趋势,蒙脱石有所下降,高岭石有所上升,供试土壤粘粒矿物随着气候的变化表现出一定的规律性.     

Palaeogeography and clay mineralogy of mid-Cretaceous flysches in the Gibraltar Arc area

A combined sedimentological and mineralogical study of several mid-Cretaceous sequences of the western Betic Cordillera and northern Rif has lead to the distinction of three main palaeogeographic areas. The basins of these areas received influxes of terrigenous sediments from different source areas. The southern Iberian margin was fed from the Iberian palaeocontinent and its clay-mineral association is characterized by a high content of well crystallized illite and kaolinite; the distal part of this margin was locally starved of continental sedimentation, but contains a considerable clayey contribution, probably oceanic in origin, made up mainly of smectites, illite and palygorskite. The sediments in the North African margin and the southern part of the North African Flysch Trough came from the African continent, the typical Aptian-Albian clay-mineral association being well crystallized illite, illite-smectite mixed layers, kaolinite, chlorite and lesser quantities of vermiculite. The terrigenous supply to the Mauritanian Realm of the North African Flysch Trough came from the Meso-Mediterranean terrane, and its usual Aptian-Albian clay association is illite, vermiculite, illite-smectite mixed layers and kaolinite. A significant change in the clay mineralogy occurred during the late Albian-early Cenomanian in the two former areas, consisting of a decrease in the detrital supply and a concomitant increase in smectites and palygorskite.The sedimentological and mineralogical evolution of this area was controlled by a combination of tectonic, eustatic and climatic changes in the westernmost Tethys during the mid-Cretaceous.     

Insight into the effects of clay mineralogy on the cyclic behavior of silt–clay mixtures

Results of a systematic testing program showed that the cyclic behavior of silt–clay mixtures is greatly influenced by the dominant clay minerals in the mixture. In particular, it was demonstrated that given the same amount of clay/clay mineral and/or same value of plasticity index, the montmorillonitic soils have the highest cyclic strength, followed by the illitic soils, and then by the kaolinitic soils. Moreover, the rate of increase in cyclic strength with increasing % clay mineral and PI is again the highest in the montmorillonitic soil, lowest in the kaolinitic soil and intermediate in the illitic soil. Therefore, without considering clay mineralogy, the % clay fraction, % clay mineral and plasticity index are unreliable indicators of the liquefaction susceptibility of fine-grained soils. The differing adhesive bond strength each clay mineral develops with the silt particles is deemed to largely explain the observed differences in the response of the three different soil mixtures to cyclic loading.     

Radiation and energy balance dynamics over young chir pine (Pinus roxburghii) system in Doon of western Himalayas

The regional impacts of future climate changes are principally driven by changes in energy fluxes. In this study, measurements on micrometeorological and biophysical variables along with surface energy exchange were made over a coniferous subtropical chir pine (Pinus roxburghii) plantation ecosystem at Forest Research Institute, Doon valley, India. The energy balance components were analyzed for two years to understand the variability of surface energy fluxes, their drivers, and closure pattern. The period covered two growth cycles of pine in the years 2010 and 2011 without and with understory growth. Net short wave and long wave radiative fluxes substantially varied with cloud dynamics, season, rainfall induced surface wetness, and green growth. The study clearly brought out the intimate link of albedo dynamics in chir pine system with dynamics of leaf area index (LAI), soil moisture, and changes in understory background. Rainfall was found to have tight linear coupling with latent heat fluxes. Latent heat flux during monsoon period was found to be higher in higher rainfall year (2010) than in lower rainfall year (2011). Higher or lower pre-monsoon sensible heat fluxes were succeeded by noticeably higher or lower monsoon rainfall respectively. Proportion of latent heat flux to net radiation typically followed the growth curve of green vegetation fraction, but with time lag. The analysis of energy balance closure (EBC) showed that the residual energy varied largely within ±30% of net available energy and the non-closure periods were marked by higher rainspells or forced clearance of understory growths.     

Lime stabilization of clay minerals and soils

Clay soil can be stabilized by the addition of small percentages, by weight, of lime, thereby enhancing many of the engineering properties of the soil and producing an improved construction material. In order to illustrate such improvements, three of the most frequently occurring minerals in clay deposits, namely, kaolinite, montmorillonite and quartz were subjected to a series of tests. As lime stabilization is most often used in relation to road construction, the tests were chosen with this in mind. Till and laminated clay were treated in similar fashion. With the addition of lime, the plasticity of montmorillonite was reduced whilst that of kaolinite and quartz was increased somewhat. However, the addition of lime to the till had little influence on its plasticity but a significant reduction occurred in that of the laminated clay. All materials experienced an increase in their optimum moisture content and a decrease in their maximum dry density, as well as enhanced California bearing ratio, on addition of lime. Some notable increases in strength and Young's Modulus occurred in these materials when they were treated with lime. Length of time curing and temperature at which curing took place had an important influence on the amount of strength developed.     

Heavy metal distribution and environmental status of Doon Valley soils, Outer Himalaya, India

 Doon Valley is surrounded by two major river systems (Ganga and Yamuna) on either side, with a water divide passing nearly across the centre of the valley, and is sandwiched between two mountain ranges in the fragile ecological systems of the Himalayan foothills. In total 398 soil samples were collected from the valley in a grid pattern (∼1 sample per 2 km²) and investigated for their heavy metal (Cr, Cu, Ni, Pb and Zn) abundances that are environmentally sensitive. Comparison of the heavy metal abundances with the contamination threshold values (CTV) revealed that most of these elemental abundances in Doon Valley soils fall well within the range of the uncontaminated to slightly contaminated category. In the case of Cr and Ni, a sizeable number of samples exceeded the CTV (250 and 100 mg kg^–1 respectively) with an overall background value of 109 and 52 mg kg^–1 respectively. Sites of high Cr and Ni mostly occur in the Ganga Catchment (GC) sector that includes even relatively undisturbed forestland. The source of this contamination is attributed to geological factors which indicate contribution from the mafic volcanics of the Lesser Himalaya. This is also consistent with the distribution pattern of Mn and Fe, though their abundance levels are not alarming. The background concentration of Pb is low (22 mg kg^–1) in Doon Valley soils; however, signs of gradual Pb contamination are palpable in and around the centre of the Dehra Dun city and along the highways. Aluminium normalized heavy metal ratios were found to exhibit narrow variability in the case of Cu, Ni and Cr and had good correlation with Al, indicating their affinity and association with the clay minerals. On the other hand, Pb and Zn seem to be associated with non-silicate sources. Received: 7 January 2000 · Accepted: 30 July 2000     

Effect of diagenesis on clay mineralogy and organic matter in the Tunisian southern subsurface

This study aims to follow the effect of the diagenetic transformations on the clayey fraction and the organic matter of the Tunisian southern sub-surface. 61 samples from oil well named NWA-1 were recuperated for series of analyses. This study follows a comparative approach between the mineralogical, geochemical and petrographic studies. To discuss results from a statistical viewpoint, the Principal Component Analysis (PCA) was applied in order to find out any correlation between different components. The associated minerals quartz, feldspar, calcite, pyrite, anhydrite, gypsum, dolomite and olivine are also detected. These associated minerals remove by-products by the illitization reaction. The Index of Crystallinity (IC) of illite shows that, except some anomalies, the studied samples are between the epizone and the anchizone. Downward, samples show the effect of diagenetic processes and weak signs of low-grade metamorphism. As regards to the organic matter, values of Tmax range between 333°C and 463°C. On the other hand, potential hydrocarbon compounds (S2) show low values compared to those of (S1); but they maintain a similar variability from 0.63 to 21.12. SEM observations and X-ray microanalyses supported the formation of authigenic micro-quartz. The PCA of clay minerals, chemical components, and the depth shows three different populations. Feldspar, chlorite and quartz make up a population positively correlated with the depth. The second population seems to be indifferent to depth variation; it is made up of two sub-populations: the population of illite, gypsum and anhydrite, which is obtained by a counter clock rotation of depth population; and the population of pyrite, kaolinite, olivine phyllosilicate, which is obtained by an anticlockwise rotation of depth population. Third, the population of smectite, calcite and dolomite is inversely proportional to the depth variation. On the other hand, the PCA of TOC, Tmax, HI, S1, S2 and the depth make up a homogenous statistical population following the depth evolution.     

Palynology and clay mineralogy of the Deccan volcanic associated sediments of Saurashtra,Gujarat: Age and paleoenvironments

The intertrappean sediments associated with Deccan Continental Flood Basalt (DCFB) sequence at Ninama in Saurashtra, Gujarat yielded palynoassemblage comprising at least 12 genera and 14 species including Paleocene taxa such as Intrareticulites brevis, Neocouperipollis spp., Striacolporites striatus, Retitricolpites crassimarginatus and Rhombipollis sp. The lava flows of Saurashtra represent the northwestern most DCFB sequence in India. It is considered that the Saurashtra lava flows represent the earliest volcanic activity in the Late Cretaceous of the Reunion Mantle Plume on the northward migrating Indian Plate. The present finding of the Paleocene palynoflora from Ninama sediments indicate Paleocene age for the associated lava flows occurring above the intertrappean bed which suggests that the Saurashtra plateau witnessed eruption of Deccan lava flows even during Paleocene. The clay mineral investigation of the Ninama sediments which are carbonate dominated shows dominance of low charge smectite (LCS) along with the presence of mica and vermiculite. Based on the clay mineral assemblage it is interpreted that arid climatic conditions prevailed during the sedimentation. The smectite dominance recorded within these sediments is in agreement with global record of smectite peak close to the Maastrichtian–Paleocene transition and climatic aridity.     

The chemistry and mineralogy of the clay fraction of sediments from the southern Barents Sea

The separated clay fraction (material <μ) of surface and sub-surface sediment samples from the southwestern Barents Sea is described. The partitioning of the major and minor elements within the different grain-size fractions of the sediment and between detrital and non-detrital phases demonstrates that the clay chemistry of these oxic shelf sediments is terrigenous in origin.The clays are a variable mixture of micaceous debris and illite with chloritic material, minor expandable clay and occasional kaolinite. Carbonate debris and amphibole occur locally. The semi-quantitative analysis suggests the existence of a considerable variation in the relative content of the principal mineralogical components and this is confirmed by the investigation of the major and minor elements. The terrigenous chemistry provides a more sensitive index of clay variability and allows the recognition of three distinct petrographic provinces.     

Shear strength behavior and parameters of microbial gellan gum-treated soils: from sand to clay

Microbial biopolymers have recently been introduced as a new material for soil treatment and improvement. Biopolymers provide significant strengthening to soil, even in small quantities (i.e., at 1/10th or less of the required amount of conventional binders, such as cement). In particular, thermo-gelating biopolymers, including agar gum, gellan gum, and xanthan gum, are known to strengthen soils noticeably, even under water-saturated conditions. However, an explicitly detailed examination of the microscopic interactions and strengthening characteristics between gellan gum and soil particles has not yet been performed. In this study, a series of laboratory experiments were performed to evaluate the effect of soil–gellan gum interactions on the strengthening behavior of gellan gum-treated soil mixtures (from sand to clay). The experimental results showed that the strengths of sand–clay mixtures were effectively increased by gellan gum treatment over those of pure sand or clay. The strengthening behavior is attributed to the conglomeration of fine particles as well as to the interconnection of fine and coarse particles, by gellan gum. Gellan gum treatment significantly improved not only inter-particle cohesion but also the friction angle of clay-containing soils.