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The nickel-bearing laterites of Noorabad area are seen in the high Zagros zone along with Kermanshah ophiolitic complex. The ophiolitic complex in the studied area includes serpentinized peridotites, isotropic gabbros, plagiogranite, sheeted dykes, basaltic lavas, andesite, and radiolarite. The peridotites of this ophiolitic complex include dunite, harzburgite, and lherzolite. The tectonic activities have caused tectonization in these rocks in such a way that it has facilitated their alteration process and created laterite zones. The alterations of peridotite rocks include serpentine, dolomite, hematite, and silicification. The laterite zone is layered and lens-shaped red horizon on peridotite rocks and is covered by Miocene limestones. Based on XRD analysis, mineralogy of the lateritic zone includes dolomite, quartz, smectite, and serpentine. The ratio of La/Y changes indicates that the studied laterites were formed in alkaline pH. According to the discrimination diagrams of the source rock, the studied laterites are karst bauxites with ultrabasic origin. Introduction Laterites are formed in areas with long tectonic stability and low erosion rates (Brand et al., 1998). Usually, the source rock of these laterites is serpentinites. Nickel is washed from the profile upper parts and concentrates in the lower parts, causing the enrichment and formation of nickel-bearing laterites. Most nickel-bearing laterite profiles have two ore types, an oxide component and a hydrous silicate or clay silicate component (Brand et al., 1998). The richest deposits of nickel-bearing laterite are formed where oxide-rich regoliths rise and nickel is washed down to the new silicates in saprolite (absolute accumulation) to be concentrated (Butt & Cluzel, 2013). This study tried to investigate the field geology, mineralogy, lateritization process, and geochemistry of Noorabad laterites (northwest of Lorestan province, Iran). Materials and methods The field operations were carried out in several rounds and led to the collection of 30 samples from serpentines and laterites of the studied area. Then, by preparing 25 thin and polished sections, the geological characteristics of ores, especially their texture and associated minerals, were discussed. Then three soil laterite samples, for mineralogical study by XRD method were sent to the central lab of Lorestan University and 10 rock and soil samples from the laterites of the studied area were sent to the Canadian SGS laboratory for determining the amount of major and minor elements by ICP-MS method. Results The peridotite rocks of Noorabad ophiolite complex in the northwest of Lorestan province include dunite, harzburgite, and lherzolite, which have been strongly affected by alteration. The tectonic activities have caused crushing in these rocks in a way that has facilitated their alteration process and created laterite areas. As a result of different alteration processes such as serpentinization, carbonation, hematitization, and silicification, primary minerals such as olivine, pyroxene, and spinel have been altered and secondary minerals such as serpentine, dolomite, quartz, hematite, and smectite have been formed. The laterite zone is a layered red horizon and in some areas is lenticular, which is located on peridotite rocks. In some areas it is covered by Miocene limestones. In some areas, the secondary fractures of laterites formed by tectonic and diagenesis activities are filled by dolomite and silica. According to XRD analysis, there are dolomite, quartz, hematite, smectite and serpentine group minerals in the laterite section. The chemical analysis of the studied samples shows the nickel content of 381-2660 ppm for Noorabad laterites. According to the discrimination diagrams of source rock, the studied laterites are derived from ultramafic rocks. Moreover, the investigations carried out on the La/Y ratio showed that the formation environment for the studied laterite samples is alkaline. Discussion The peridotite rocks of Kermanshah ophiolite are related to suprasubduction ophiolites (Kiani, 2011). Due to the multi-stage replacement mechanism, these types of peridotites undergo the most serpentine alteration, so that their severe crushing during replacement and their migration on the margins of the continents facilitate the intensity of the altered. The peridotites of northwestern of Lorestan province were altered into serpentine during these alterations in the initial stages, and then underwent carbonate, hematite, and silicification alterations. During these changes, the primary minerals of these peridotites, such as olivine, pyroxene, and spinel, have become secondary minerals. The serpentine minerals are the first group of secondary minerals that were formed. Then, the secondary minerals of the second stage replaced the serpentines in such a way that the minerals of the smectite group can directly replace the serpentine (Dixon, 1989; Nahon et al., 1989; Gaudin et al., 2005). Other minerals are formed by substitution and saturation of other elements and form minerals with simple chemical formula such as quartz, dolomite, and hematite. During the first stages of alteration of peridotite rocks, the main elements Si, Mg, Ca, Fe, and Al were washed from the rock and caused the formation of secondary minerals in the lateritic zone. A significant amount of silica is included in the structure of silicate minerals such as serpentine and smectite, and the rest is filled in fractures in the form of chert and chalcedony. During the weathering process, magnesium-bearing minerals are destroyed and Mg2+ is removed from them, so that some of the magnesium in the serpentine mineral are replaced by Ni2+ (Sagapoa et al., 2011) and nickel-bearing serpentine minerals. The Ca element is removed from the pyroxene group minerals during alteration and enters the structure of smectite minerals or forms dolomite mineral. The Ni element has a positive correlation with the Co, Mg, Cr, and Fe elements, and this correlation can be due to the substitution of nickel instead of these elements in the crystal network of secondary minerals or due to the surface absorption of the mentioned elements by the hematite mineral.

Parent material and topography are among the soil-forming factors that affect soil evolution by influencing different parameters. This study was conducted to compare the effect of marl and calcareous parent materials in different slope positions, including the summit, shoulder, foot-, and toe-slopes on soil clay mineralogy in the Karoon 3 Basin, east of Khuzestan Province. Four soil profiles in each of the two topo-sequences were dug. They were sampled based on their genetic horizons and some physical, chemical properties, and clay mineralogy were measured. The results showed that the type and abundance of clay minerals identified for both parent materials were more affected by topo-sequence position. The composition of minerals identified in the topo-sequence with marl parent materials included kaolinite, palygorskite, smectite, chlorite, mica, and quartz, and in the topo-sequence with calcareous parent materials, palygorskite, smectite, chlorite, mica minerals, and quartz, and most of the identified minerals were also observed in all positions in the C horizon. However, in marl parent materials kaolinite, and calcareous parent materials, smectite seems to have been formed pedogenically. The result of the association between Weaver and Beck indicated that most of the clay minerals are in the equilibrium of Palygorskite.

Parent material and topography are among the soil-forming factors that affect soil evolution by influencing different parameters. This study was conducted to compare the effect of marl and calcareous parent materials in different slope positions, including the summit, shoulder, foot-, and toe-slopes on soil clay mineralogy in the Karoon 3 Basin, east of Khuzestan Province. Four soil profiles in each of the two topo-sequences were dug. They were sampled based on their genetic horizons and some physical, chemical properties, and clay mineralogy were measured. The results showed that the type and abundance of clay minerals identified for both parent materials were more affected by topo-sequence position. The composition of minerals identified in the topo-sequence with marl parent materials included kaolinite, palygorskite, smectite, chlorite, mica, and quartz, and in the topo-sequence with calcareous parent materials, palygorskite, smectite, chlorite, mica minerals, and quartz, and most of the identified minerals were also observed in all positions in the C horizon. However, in marl parent materials kaolinite, and calcareous parent materials, smectite seems to have been formed pedogenically. The result of the association between Weaver and Beck indicated that most of the clay minerals are in the equilibrium of Palygorskite. [ABSTRACT FROM AUTHOR]

The nickel-bearing laterites of Noorabad area are seen in the high Zagros zone along with Kermanshah ophiolitic complex. The ophiolitic complex in the studied area includes serpentinized peridotites, isotropic gabbros, plagiogranite, sheeted dykes, basaltic lavas, andesite, and radiolarite. The peridotites of this ophiolitic complex include dunite, harzburgite, and lherzolite. The tectonic activities have caused tectonization in these rocks in such a way that it has facilitated their alteration process and created laterite zones. The alterations of peridotite rocks include serpentine, dolomite, hematite, and silicification. The laterite zone is layered and lens-shaped red horizon on peridotite rocks and is covered by Miocene limestones. Based on XRD analysis, mineralogy of the lateritic zone includes dolomite, quartz, smectite, and serpentine. The ratio of La/Y changes indicates that the studied laterites were formed in alkaline pH. According to the discrimination diagrams of the source rock, the studied laterites are karst bauxites with ultrabasic origin. [ABSTRACT FROM AUTHOR]

Potassium fixation is one of the most important factors influencing the availability of this ion for plants. This research was carried out to evaluate the relationship between potassium (K) fixation with some physical and chemical characteristics of soils and clay minerals and to investigate the effect of the dry and wet cycle on potassium fixation in Kakan Plain, in Kohgilouye & Boyerahmad Province. To measure the amount of Potassium fixation, four levels of K were added to the samples and the samples were shaken for 24 h and then dried in the oven at 50°C for 24 h. The drying and wetting cycle was repeated three times. Another set of soil samples was similarly incubated for a period similar to the previous treatment, but drying was performed at room temperature in an equilibrium state. The results showed that potassium fixation was increased with the potassium concentration increment, whereas K fixation percentage was reduced. Also, potassium fixation showed a positive significant relationship with cation exchange capacity (CEC) as well as clay content, in both normal and dry and wet treatments, and a negative significant relationship with organic carbon. Moreover, potassium fixation was enhanced with the increase of smectite content in both normal and dry and wet treatments. Besides, due to more organic carbon and less smectite, surface horizons fixed K less than the subsurface horizons.

Introduction: Minerals are one of the main components of soils which play different roles in the soils. Minerals make up about 50% of the volume of most soils. They provide physical support for plants, and create the water- and air-filled pores that make plant growth possible. Mineral weathering releases plant nutrients which are retained by other minerals through adsorption, cation exchange, and precipitation. Minerals are indicators of the amount of weathering that has taken place, and the presence or absence of particular minerals gives clues to how soils have been formed. The physical and chemical characteristics of soil minerals are important consideration in planning, constructing, and maintaining of buildings, roads, and airports. Clay minerals can be used for understanding of soil formation, optimum management of dry and wet lands and interpretation of paleo environments. Moreover, clay minerals can provide some valuable information such as the origin of sediments, transportation and precipitation of sediments and also some information about intercontinental weathering regimes. Quaternary sediments have occupied most of the agricultural and natural resources of Urima plain and recognition of mineralogical of these soils is essential to optimum and stabile use of these soils. Additionally, caly mineralogical investigation can provide some information about the intensity of weathering processes and climate change in this area. Thus, in this study clay minerals of quaternary sediments in northeast of Urmia and the mechanisms of their formation and also tracing probable climate change in this area were investigated. Materials and Methods: This study was performed in theUrmia plain in west Azerbaijan Province. The study area is located on quaternary sediments and physiographically, this area is a part of a river alluvial plain with the gentle slope toward Urmia Lake. The mean annual precipitation and temperature of this area are 345.37 mm and 10.83 °C respectively and the soil moisture and temperature regimes are dry xeric and mesic respectively. In this study, eight soil profiles in quaternary sediments were dug and sampled and the morphological, physical, chemical and mineralogical properties were determined using standard methods. Results and Discussion: According to the results, Illite, smectite, Kaolinite, chlorite, vermiculite and hydroxy interlayer vermiculite (HIV) were the dominant clay minerals in these soils. The origin of illite, chlorite and kaolinite were related to inheritance from parent material. Regarding to the present of some smectite in the parent material of these soils, some of smectites have been inherited from parent material. Nevertheless it seems that, the most of smectites in these soils have pedogenic origin. Based on mineralogical results and trends variation of smectite and illite along studied profiles, we concluded that some of smectites in these soils have been formed from illite transformation. In profiles 4 and 6, regarding to low depth water table and consequently poor drainage, high pH and high values of calcium and magnesium cations, provide suitable conditions for the neoformation of smectit and so, some of smectites have been formed via neoformation from soil solution. In these soils, vermiculites were pedogenic and have been formed during transformation of illite to smectite. Small amounts of hydroxy interlayer vermiculites were present in buried horizons and regarding that they were not present in parent material, it might be because these minerals are pedogenic and have been formed in a past wetter climate. The transformation of illite to smectite in lower horizons needs high moisture and regarding to recent semiarid climate of study area, the suitable amount of moisture for this transformation, especially in lower depths and also in buried horizons, is not present. Thus, it seems the transformation of illite to smectite in lower depths and buried horizons has been taken place in a wetter past climate. So we concluded that smectite and hydroxy interlayer vermiculite are evidences of a wetter past climate in this area. Conclusion: In this study the origin of smectite in buried horizons was related to transformation of illite. According to high moisture condition which is necessary for the weathering of illite, the occurrence of this process related to more humid climate of the past. Additionally, the presence of hydroxy interlayer vermiculites was related to previously wetter climate as well. So results of this study can be used for recognition of climatic change in the study area.

Introduction: Soil and geomorphology are closely related to each other. That is why considering geomorphic concepts in soil genesis and classification studies may cause a better understanding of soil genesis processes. Paleosols with argillic horizons were investigated on stable pediment surfaces in Jiroft area, central Iran, by Sanjari et al. (2011). They found that secondary gypsum and calcium carbonate were accumulated in mantled pediments, but moving down the slope toward lowlands, salts more soluble than gypsum have been accumulated. Clay mineralogy in soil researches helps to better studying soil genesis and development. A quantitative and qualitative study of clay minerals together with their structural composition provides valuable data on the absorption, fixation, and desorption of different cations in soils. Smectite, chlorite, illite, vermiculite, kaolinite, palygorskite, and sepiolite were reported as dominant clay minerals found in arid and semi-arid areas. The objectives of the present study are to evaluate the clay mineralogy of Jabalbarez-Jiroft soils on different geomorphic surfaces. Materials and Methods: The study area was located in Jabalbarez, 200 Km south Kerman, Central Iran. Fig. 1 showed the exact location of study area. Soil temperature and moisture regimes of the area were thermic and aridic, respectively. Hill, rock pediment, mantled pediment and piedmont alluvial plain landforms were identified, using aerial photo interpretation, topography and geological map observation, in addition to detailed field works. Air-dried soil samples were crushed and passed through a 2-mm sieve. Routine physicochemical analyses wereperformed on the samples. Undisturbed soil samples from the Bt horizon of pedons 4, 5 and 6 were chosen for micromorphology investigations. Beside, eight samples including A and C2 horizons of pedon 1, A and Bt horizon of pedon 3, Bt and Bw horizons of pedon 4, and Bt and C horizon of pedon 5 were selected for clay mineralogy. Results and Discussion: Argillic horizon found in mantled pediment and piedmont alluvial plain surfaces and stable hill, respectively. In thin horizons coating of clay were observed. Pedofeatures formed in this geomorphic surface, seemed to have been buried in the soil, due to the favorable conditions in terms of the time factor and the presence of moisture in the past. Fig. 2 showed clay coatings in the Bt horizon of pedons 4,5 and 6. The presence of argillic horizons in the arid climate of the research area is attributed to a more humid paleoclimate, which was also reported by Farpoor et al. (2002), Khademi and Mermut (2003), and Sanjari et al. (2011) in Rafsanjan, Isfahan and Jiroft, central Iran, respectively. Clay minerals illite, smectite, chlorite and kaolinite were identified by using X-ray diffractometer. Similar results were also obtained by Sanjari et al. (2011) in the Jiroft area. Kaolinite and illite in soils of arid and semi-arid environments of Iran have been reported with an inherited origin (Khormali and Abtahi, 2003; Sanjari et al., 2011). As the environmental conditions are not favorable for the pedogenic formation of such minerals in soils of this study area , it is proposed that they might be inherited from their parent material. Just as previously stated by other researchers that the origin of the kaolinite minerals in the dry climate regionsis due to itsinheritance from parent materials (Farpoor et al., 2002; Khormali and Abtahi, 2003). The dominant of smectite minerals in soils on stable geomorphic surfaces ofhills and mantled pediment can be cause of stable level and more moisture content in the past and the present, which may be resulted to smectite formation from illite and chlorite transformation. Also, chlorite minerals on stable surface of mantled pediment were not observed. High amount of leaching, low pH level (

This research was carried out to assess the origin and clay minerals characteristics and their relationship with potassium forms in the calcareous soil of this region, with the humid climate conditions. Based on aerial photos and topographic maps, physiographic units were separated and soil sampling was done in each diagnostic horizon. The results showed that smectite was the main and dominant clay mineral in the study area. In well-drained pedons, the convincing process for smectite abundance seemed to be mainly the transformation of palygorskite and mica. According to the results, the exchangeable potassium in the surface horizon was higher than that of the subsurface horizons. The main reason for the higher level of exchangeable K in the soil surface, was more smectite and organic carbon. The results revealed that unlike exchangeable and non-exchangeable K, because of the suitable conditions like temperature and humidity in surface horizons, the relative mean of structural K in the surface soils was less than that in the subsurface. Also, since an increase in calcium carbonate resulted in a decrease in amount of clay and the amount of relative clay minerals (dilution effect), the amounts of exchangeable, non- exchangeable and structural K were decreased. [ABSTRACT FROM AUTHOR]

Introduction: Potassium is an essential element for plant growth and its importance in agriculture is well known. Total soil potassium reserves are generally large; although the distribution of K forms differs from soil to soil as a function of the dominant soil clay minerals present. The objectives of the present study were: (i) the content, forms, and distribution of K as a function of clay mineralogy in different physiographic units; (ii) to investigate the relationship between K fractions and their physiographic units. Materials and Methods: The study area is located in south of eastern Azarbaijan province, north of Iran. The region stands between 37° 45' and 38° 00' N latitudes and 46° 00' and 46° 15' E longitudes. The present climate of the region has dry and hot summers, cold and wet winters; with an average rainfall of 334 mm. soil moisture and temperature regimes of study area are xeric and mesic, respectively. Site selection for studied pedons was based on a reconnaissance survey from different physiographic units, namely, pedons 1, 2 and 3 located on Piedmont Plain (PP), pedons 4, 5 and 6 on Rivera Alluvial Plain (RAP) and pedons 7, 8 and 9 on Low Lands (LL). Soils were described and classified based on soil survey manual and keys to soil taxonomy. Samples were air dried, crushed and passed through a 2mm sieve. Particle size distribution, organic matter, Calcium Carbonate Equivalent (CCE), pH, Electrical Conductivity (EC) and Cation Exchange Capacity (CEC) and different forms of K (total, soluble, exchangeable and nonexchangeable) were determined. X-ray diffractograms were obtained through a Shimadzu XRD 6000 defractometer employing a Ni-filtered CuKa radiation source from oriented clay (40 kV, 30 mA). The content of clay minerals was estimated according to Biscaye method. Results and Discussion: All soil samples were calcareous, calcium carbonate content was between 10 and 17%, with relatively high clay content, ranging from 18 to 36%. Soil organic carbon contents were between 0.3 to 1.9%. Land use affected the amount of organic matter so the pedons located on piedmont plain showed more organic matter than other units. Variation in soil characteristics were considerable, which was most affected by physiography. The variation was also especially noticeable in clay minerals and K pools. Soluble K, ranging from 6 to 14 mg/kg, had higher content in piedmont plain than other units. Nonexchangeable k was between 345 to 545 mg/kg and piedmont plain had higher amount because of existing more illite. Exchangeable K, ranging between 278-416 mg/kg had highest content in piedmont plain and lowest content in river alluvial plain. The release rate of non-exchangeable K is the result of the type and particle size of K bearing minerals and soil conditions. The XRD data for the less than 2 μm fractions of the studied soils indicated that the soils were similar in their clay mineralogy, mainly consisted of illite, smectite, kaolinite and chlorite, but were different in content. Illite and smectite were higher in Piedmont Plain (PP) and Low Lands (LL) had higher content of smectite in comparison with River Alluvial Plain (RAP) due to low drainage condition. Several factors such as differences in geomorphological conditions and clay mineralogy between physiographic units caused the differences in K forms. The statistically significant relationship between clay content and most forms of k was because of high specific surface of clays. A highly significant positive relationship between non exchangeable K and illite content (r2 = 0.81, P

Potassium fixation is one of the most important factors influencing the availability of this ion for plants. This research was carried out to evaluate the relationship between potassium (K) fixation with some physical and chemical characteristics of soils and clay minerals and to investigate the effect of the dry and wet cycle on potassium fixation in Kakan Plain, in Kohgilouye & Boyerahmad Province. To measure the amount of Potassium fixation, four levels of K were added to the samples and the samples were shaken for 24 h and then dried in the oven at 50°C for 24 h. The drying and wetting cycle was repeated three times. Another set of soil samples was similarly incubated for a period similar to the previous treatment, but drying was performed at room temperature in an equilibrium state. The results showed that potassium fixation was increased with the potassium concentration increment, whereas K fixation percentage was reduced. Also, potassium fixation showed a positive significant relationship with cation exchange capacity (CEC) as well as clay content, in both normal and dry and wet treatments, and a negative significant relationship with organic carbon. Moreover, potassium fixation was enhanced with the increase of smectite content in both normal and dry and wet treatments. Besides, due to more organic carbon and less smectite, surface horizons fixed K less than the subsurface horizons. [ABSTRACT FROM AUTHOR]