Mineralogical, geochemical, and geotechnical evaluation of Al-Sowera soil for the building brick industry in Iraq

The raw material soil of Al-Sowera factory quarry (quarry soil and mixture) used for building brick industry was tested mineralogically, geochemically and geotechnically. Mineral components of soil are characterized by Clay minerals (Palygoriskite and chlorite) and non-clay minerals like calcite, quratz, feldspar, gypsum and halite. The raw material is deficient in SiO₂, Al₂O₃, K₂O, Fe₂O₃ and MgO, while enriched in CaO. Loss on ignition and Na₂O are in suitable level and appear to be concordant with the standard. Grain size analyses show that the decreasing sand and clay, and increasing silt ratio in both quarry soil and mixture caused decreasing in strength of brick during molding and after firing. The quarry soil is characterized by high plasticity clayey soil of 30.49 plastic index (P.I), whereas the mixture considered a clayey soil has a low plasticity of 7.7 plastic index (P.I). To improve the chemical and physical properties of the raw material, alumina-silicate minerals rich in K₂O, Fe₂O₃ and MgO are recommended as additive materials to the main mixture.     

Mineralogical and Geochemical Constraints on the Sediment Sources of Late Stone Age Pottery from the Birimi Site,Northern Ghana

The mineralogy and bulk chemical compositions of 15 Kintampo (Late Stone Age) potsherds from the Birimi site on the Gambaga Escarpment and eight samples of local sediment were determined with the intent of characterizing these wares and identifying the material used in their manufacture. Sediment from clay pits still used by potters north of the escarpment contains iron‐rich laterite clasts (100 × XFeO_t = 100 × FeO_t/[FeO_t + Al₂O₃ + SiO₂] ≥10). Sedimentary clasts in stream sediments are relatively siliceous and iron‐poor (100 × XFeO_t < 10). Bulk geochemical data together with the compositions of lithic clasts (laterite, siltstone/sandstone) link the pottery to sediment sources, including escarpment sediments not presently used by Ghanaian potters. Fresh granite clasts found in some of the sherds were not found in the analyzed sediment samples, although some of their distinctive mineralogical constituents (e.g., variably barian alkali feldspar) are present. The analytical data suggest that pots found at Birimi were made locally by mixing escarpment sediment with clay and stream sediment brought in from below the escarpment. This contrasts with present‐day practice, whereby the pots themselves are imported. The place where Birimi pottery was made and the outcrop source of aluminous sediment (mudstone with an “escarpment” trace element signature) used in these wares, however, remain unidentified. © 2013 Wiley Periodicals, Inc.     

Lower riphean low-carbonaceous shales in the southern urals: Raw material for the manufacture of porous rubble

A property of swelling on heating to yield firm lightweight granules has first been revealed for lowcarbonaceous shales (LCS) from the Riphean stratotype in the Bashkirian Megaanticlinorium, Southern Urals. These granules possess all technological properties of “keramzite” or claydite (an artificial, expanded clayey material) and can successfully substitute this material. Moreover, the procedure of their manufacture, analogous to the manufacture of “shungizite” (an artificial carbonaceous-clayey material) from Lower Proterozoic clayey rocks of Karelia, is more economical than that for keramzit. Productive beds of the homogeneous LCS make up extended bodies tens of meters thick. At the present time, they can be used as cover rocks during the exploitation of the Bakal siderite deposits. The LCS represent fine-grained quartz-chlorite-sericite aggregates (with variable relationships between the major components), bearing fine-dispersed shungite in amounts of 0.5–1.0%. High-quality raw material of this kind is characterized by a fine-dispersed admixture of a mixed-layer clayey material bearing montmorillonite and vermiculite. Geological, lithological, mineralogical, and chemical prognostic criteria have been developed for the shungizite raw material. It has been concluded that this construction material, new for the Urals, is promising for industrial use     

论江苏若干矿产资源开发利用的新方向

江苏泥炭大多数为低有机质分解较强的低位泥炭，适于制作肥料或制成腐肥使用；江苏硅质原料丰富，一种以硅为主的化肥——硅肥正日益显示其重要性；湖泊淤泥具有颗粒微细、含砂量少、可塑性高、结合力强、干燥敏感性好和收缩率较大等特点，是生产空心砖的最佳原料；高家边组泥页岩和坟头组底部细粉砂质泥岩及泥质粉砂岩是良好的陶粒原料、砖瓦、陶瓷建材以及水泥用粘土质原料；利用矿泉水与茶的结合能够生产出高、中、低多效应的复合型新产品。上述尚未被利用或利用程度不够的矿产资源有着广泛的开发利用前景。     

Mineralogy and geochemistry of laterites from the Morro dos Seis Lagos Nb (Ti,REE) deposit (Amazonas,Brazil)

The Morro dos Seis Lagos niobium deposit (2897.9 Mt at 2.81 wt% Nb₂O₅) is associated with laterites formed by the weathering of siderite carbonatite. This iron-rich lateritic profile (>100 m in thickness) is divided into six textural and compositional types, which from the top to the base of the sequence is: (1) pisolitic laterite, (2) fragmented laterite, (3) mottled laterite, (4) purple laterite, (5) manganiferous laterite, and (6) brown laterite. All the laterites are composed mainly of goethite (predominant in the lower and upper varieties) and hematite (predominant in the intermediate types, formed from goethite dehydroxylation). The upper laterites were reworked, resulting in goethite formation. In the manganiferous laterite (10 m thick), the manganese oxides (mainly hollandite, with associated cerianite) occur as veins or irregular masses, formed in a late event during the development of the lateritic profile, precipitated from a solution with higher oxidation potential than that for Fe oxides, closer to the water table. Siderite is the source for the Mn. The main Nb ore mineral is Nb-rich rutile (with 11.26–22.23 wt% Nb₂O₅), which occurs in all of the laterites and formed at expense of a former secondary pyrochlore, together with Ce-pyrochlore (last pyrochore before final breakdown), Nb-rich goethite and minor cerianite. The paragenesis results of lateritization have been extremely intense. Minor Nb-rich brookite formed from Nb-rich rutile occurs as broken spherules with an “oolitic” (or Liesegang ring structure). Nb-rich rutile and Nb-rich brookite incorporate Nb following the [Fe³⁺ + (Nb, Ta) for 2Ti] substitution and both contain up to 2 wt% WO₃. The laterites have an average Nb₂O₅ content of 2.91 wt% and average TiO₂ 5.00 wt% in the upper parts of the sequence. Average CeO₂ concentration increases with increasing depth, from 0.12 wt% in the pisolitic type to 3.50 wt% in the brown laterite. HREE concentration is very low.     

Geochemical features of nickel-laterite deposits from the Balkan Peninsula and Gordes,Turkey: The genetic and environmental significance of arsenic

Iron–nickel-laterite deposits in the Balkan Peninsula and Turkey, located in the Mirdita–Sub-Pelagonian and Pelagonian geotectonic zones, extending into the Anatolides zone are a major source of nickel. Repeated marine transgression and regression, and the multistage development of allochthonous laterite deposits by re-working and re-deposition in a shallow sea environment are demonstrated by the alternation of Fe–Ni-laterite layers within marine sequences.Geochemical study of these Fe–Ni laterite deposits shows that arsenic contents are generally low, ranging from less than 2 to a few tens of ppm. However, in the Aghios Ioannis deposit, Lokris, Central Greece As varies significantly and attains values up to 0.26 wt.% As and in the Gordes deposit of W. Turkey, the As content ranges from 0.004 to 1.07 wt.% As (average 0.34), reaching values up to 1.94 in the hematite zone. Investigation of the mineral chemistry (SEM-EDS) shows that goethite is the main host of As, ranging between 0.5 and 1.2 wt.% As₂O₃ in the Aghios Ioannis deposit, and between 1.2 to 6.9 wt.% As₂O₃ in the Gordes deposit, whereas, in co-existing calcite As was not detectable. Goethite occurs in fine-grained porous and concretionary, concentric textures. As values are higher in concretionary goethite. Positive correlation (r > 0.74) between As and Al₂O₃, TiO₂ and ∑ REE contents in the laterite deposits of Greece, coupled with the As-enrichment only in certain laterite deposits points to post depositional As-enrichment.Assuming that high pH facilitates the adsorption of As by goethite, due to its high surface area and low values of the activation energy of adsorption (literature data) As-adsorption by goethite is considered to play an important role in its retention. Elevated As-contents in goethite (Fe-oxides) in Fe–Ni-laterites of Greece and Turkey, due to its absorption capacity, are considered to be of particular significance in the remediation of aquifer and soil contamination rather than being a source of environmental risk.     

Geochemistry and mineralogy of laterites in the Sula Mountains greenstone belt, Lake Sonfon gold district, Sierra Leone

Geochemical and mineralogical investigations have been carried out on laterite profiles developed in the Lake Sonfon Au district of northern Sierra Leone. The area is underlain by Archean metavolcanics and constitutes part of the Sula Mountains greenstone belt, which is mineralized in Au. Extensive lateritization has affected the rocks of this region, resulting in a profile which from bottom to top consists typically of a decomposed bedrock zone, a pisolitic laterite layer and a duricrust layer. Both the pisolitic and duricrust layers of the laterite are sometimes punctuated by lenses of ironstones containing high amounts of Cu, Zn, Ni, Co and Ce. Gold occurs as small grains within the heavy mineral fraction recovered from the decomposed rock zones and pisolitic layers of the profiles and also in gravels of streams draining the area. The mineralogy of the duricrust and pisolitic layers is dominated by goethite, gibbsite and quartz, with minor amounts (<5% by volume) of ilmenite, magnetite, haematite, rutile and kaolinite. The kaolinite content increases towards the decomposed rock zone, where talc, vermiculite and other layer lattice silicates become abundant. The heavy-mineral fraction of stream sediments is composed essentially of ilmenite, magnetite, haematite, and traces of rutile, zircon, tourmaline and Au. The Au grains are often characterized by a 10–200-μm-wide rim having a much lower content of Ag (0.3 wt.% or lower) than the grain interior (about 5 wt.% on average). Dissolution effects are also observed on the grain surfaces. It is considered that Au derived from the amphibolite parent rock is dissolved, transported, and redeposited during laterization.The duricrust cover of the laterite profiles is characterized by high contents of Fe₂O₃ (ca. 60 wt.%) and Al₂O₃ (ca. 32wt.%) and low content of SiO₂ (ca. 9 wt.%). In comparison, the pisolitic layer is higher in SiO₂ (ca. 18 wt.%) as well as a slightly higher in Al₂O₃ (ca. 34 wt.%). Lateritic weathering has resulted in the removal of CaO, Na₂O, MgO and SiO₂, with relative enrichment of Fe₂O₃ and Al₂O₃. The geochemical distribution of the trace elements in the laterite profiles can be related to the occurrence of the auriferous mineralization. The significance of these observations is discussed in relation to the origin of the lateritic Au and the role of the associated trace elements as indicators of the mineralization.     

Natural radioactivity of bricks and brick material in the Salihli-Turgutlu area of Turkey

Some of the rocks and soil-originated materials used in building construction are the serious natural radiation sources. Soil-originated bricks and roof-tiles and their raw material in the Salihli-Turgutlu area were tested in situ for natural radiation levels using a gamma-ray spectrometer. The concentrations of the radioelements ⁴⁰K, ²³⁸U and ²³²Th and air-absorbed radiation rates were measured for soil, raw material heaps, brick and roof-tile stacks and waste brick heaps. The radium-equivalent activity Ra_eq of the raw material varied between 187.9 and 216.4 Bq kg^?1. The external radiation hazard index H_ex values ranged between 0.51 and 0.58. For building material and its products, recommended Ra_eq and H_ex levels are 370 Bq kg^-1 and 1.0, respectively. On the other hand, both Ra_eq and H_ex values for waste brick heaps, containing broken brick pieces, coal pieces and ash, were higher than the recommended levels, i.e. Ra_eq values varied from 473.8 to 651.0 Bq kg^-1 and H_ex values were within the range 1.15–1.76. The annual dose rate and radium-equivalent activity values of the brick and roof-tiles were below the level of criteria. Annual dose rate ranged between 0.42 and 0.62 mSv y^?1 and radium equivalent activity was in the range 172.9–245.2 Bq kg^?1. The external and internal radiation hazard indices were all below the value of 1.0 for the Salihli-Turgutlu area bricks and roof-tiles. Results of this study were compared with results of previous studies. Natural radiation levels of construction raw material of study area are generally higher than of those of previous studies.     

Raw Materials for Archaeological Pottery from the Campania Region of Italy: A Petrophysical Characterization

We performed petrophysical analyses on 34 clayey samples of different geological origin within the Campania region of Italy in order to determine possible sources of raw materials used to produce ancient pottery. Possible raw material sources can be grouped into high‐CaO clays (HCC) and low‐CaO clays (LCC). HCC are mainly represented by more recent (Miocene‐Pleistocene) basinal sediments whereas LCC tend to be associated with basinal, alluvial, and pyroclastic deposits. A chemical comparison between clayey raw materials, modern ceramic replicas, and Campanian archaeological ceramics of several typologies (common ware, cooking ware, fine tableware, amphorae, and bricks) from 8th century B.C. to the Middle Ages (a total of 350 ceramic samples) indicates that HCC were extensively used for common wares and that these were either mixed with temper or levigated. In contrast, most of the LCC were used for the production of cookware. We also analyzed the technological potential of the sampled raw materials, taking into consideration their actual and possible uses. We observed that most HCC deposits were well suited for tableware and amphorae, whereas LCC were better for cookware and some fine tableware.     

Sedimentary evolution and environmental history of Lake Van (Turkey) over the past 600 000 years

The lithostratigraphic framework of Lake Van, eastern Turkey, has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years. The lithostratigraphy and chemostratigraphy of a 219 m long drill core from Lake Van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity. An age model was established based on the climatostratigraphic alignment of chemical and lithological signatures, validated by ⁴⁰Ar/³⁹Ar ages. The drilled sequence consists of ca 76% lacustrine carbonaceous clayey silt, ca 2% fluvial deposits, ca 17% volcaniclastic deposits and 5% gaps. Six lacustrine lithotypes were separated from the fluvial and event deposits, such as volcaniclastics (ca 300 layers) and graded beds (ca 375 layers), and their depositional environments are documented. These lithotypes are: (i) graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations; (ii) varved clayey silts reflecting strong seasonality and an intralake oxic–anoxic boundary, for example, lake‐level highstands during interglacials/interstadials; (iii) CaCO₃‐rich banded sediments which are representative of a lowering of the oxic–anoxic boundary, for example, lake level decreases during glacial inceptions; (iv) CaCO₃‐poor banded and mottled clayey silts reflecting an oxic–anoxic boundary close to the sediment–water interface, for example, lake‐level lowstands during glacials/stadials; (v) diatomaceous muds were deposited during the early beginning of the lake as a fresh water system; and (vi) fluvial sands and gravels indicating the initial flooding of the lake basin. The recurrence of lithologies (i) to (iv) follows the past five glacial/interglacial cycles. A 20 m thick disturbed unit reflects an interval of major tectonic activity in Lake Van at ca 414 ka bp . Although local environmental processes such as tectonic and volcanic activity influenced sedimentation, the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes, making Lake Van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years.     

Sediment geochemistry of coastal environments,southern Kerala,India: implication for provenance

Late Quaternary sediments representing the floodplain, estuary and offshore environments of southern Kerala were investigated to infer provenance. The grain size reveals the dominance of sand to silty clay, clay to clayey silt and clayey silt in the floodplain, estuary and offshore sediments, respectively. The chemical index of alteration (CIA) values and A-CN-K plot attributes to high, moderate and low weathering in floodplain, estuary and offshore regions, respectively. The SiO₂/Al₂O₃ values lesser than Post-Archean Australian Shale indicate low to moderate maturity for the estuarine and offshore sediments. The geochemical immaturity indicates its derivation from low to moderately weathered source rocks. The major and trace elemental ratios and discriminant function diagrams attribute that the sediments were derived from intermediate to felsic source rocks. The enrichment of Cr and Ni concentration in the sediments compared to the upper continental crust, related to the contribution of orthopyroxenes, weathered from charnockite and garnets from the granulite terrain, respectively.     

Effect of sodium sulphate on the shear strength of clayey soils stabilised with additives

The effect of sulphates on the soil stabilisation using mineral additives such as lime, cement and fly ash has been reported by several researchers. The effect of sodium sulphate (Na₂SO₄) (0–6% by dry weight of soil) on the behaviour of the grey clayey soil (GS) and red clayey soil (RS) stabilised with lime (L) (0–8%), natural pozzolana (NP) (0–20%) and with a combination of lime-natural pozzolana (L–NP) was investigated. The soil specimens were subjected to testing of direct shear strength after 7, 30, 60 and 120 days of curing period. In the absence of Na₂SO₄, the results show that both clayey soils can be successfully stabilised with L or with a combination of L–NP, which substantially increases their shear strength and produces high values of shear parameters. However, at short curing period and for any content of Na₂SO₄, a further increase in shear strength and shear parameters is observed. Moreover, after 30 days of curing, the RS specimens stabilised with L or with NP alone are altered when the Na₂SO₄ is greater than 2%, whereas the GS specimens are not altered. However, the alteration of RS specimens is little when the L and NP are combined on curing with a high content of Na₂SO₄. Generally, the effect of Na₂SO₄ on both stabilised clayey soils depends on the curing time, percentage of additives used and their type, mineralogical composition of stabilised soils and Na₂SO₄ content.     

Study on the swelling behaviour of blended clay–sand soils

Soils containing expansive clays undergo swelling that can be both detrimental and beneficial in various applications. In the Arabian Gulf coastal region, natural heterogeneous soils containing clay and sand (tills, shales, and clayey sands) support most of the civil infrastructure systems. Likewise, mixes of clay and sand are used for local earthwork construction such as roads and landfills. A clear understanding of the swelling behaviour of such soils is pivotal at the outset of all construction projects. The main objective of this paper was to understand the evolution of swelling with increasing clay content in local soils. A theoretical framework for clay–sand soils was developed using phase relationships. Laboratory investigations comprised of mineralogical composition and geotechnical index properties of the clay and sand and consistency limits, swelling potential, and morphology of clay–sand mixes. Results indicated that soil consistency of mixes of a local expansive clay and an engineered sand depends on the weighted average of the constituents. Mixes with 10% clay through 40% clay capture the transition from a sand-like behaviour to a clay-like behaviour. Influenced by the initial conditions and soil matrix, the swelling potential of the investigated mixes correlated well with soil plasticity (SP(%) = 0.16 (I _p)^1.188). The parameters sand void ratio and clay–water ratio were found to better explain the behaviour of blended clay–sand soils.     

Arsenic remediation by Australian laterites

The efficiency of Australian laterites in arsenic adsorption has been examined using three laterite samples collected from different locations in South Australia. The characteristics such as electrical conductivity, pH, mineral compositions, and isoelectric point of laterite samples have been measured. The laterite samples are mainly composed of iron and aluminum oxides, and rutile (TiO₂). Two batch experiments have been performed to compare the efficiencies of different laterites to remove AS (III) from water at two different doses, and to examine whether pH influences arsenic adsorption. For 50 mg/l arsenic solution, at doses 1,000 g (laterite)/l (arsenic solution) and 200 g/l, the laterites removed more than 97% and 87–97%, respectively. At the dose of 200 g/l, adsorption capacity has been found to be 200–243 mg/kg. Out of the laterite samples from three localities, the Kangaroo Island laterite performed the best. This is probably related to its high content of gibbsite. It has been found that arsenic adsorption by laterite is not significantly affected at the examined pH ranges of 4.7–10.0.     

Rheological properties of clayey soils originating from flow-like landslides

Flow-like landslides in clayey soils represent serious threats for populations and infrastructures and have been the subject of numerous studies in the past decade. However, despite the rising need for landslide mitigation with growing urbanization, the transient mechanisms involved in the solid-fluid transition are still poorly understood. One way of characterizing the solid-fluid transition is to carry out rheometrical tests on clayey soil samples to assess the evolution of viscosity with the shear stress. In this study, we carried out geotechnical and rheometrical tests on clayey samples collected from six flow-like landslides in order to assess if these clayey soils exhibit similar characteristics when they fluidize (solid-fluid transition). The results show that (1) all tested soils except one exhibit a yield-stress fluid behavior that can be associated with a bifurcation in viscosity (described by the critical shear rate \( \dot{\gamma_c} \)) and in shear modulus G; (2) the larger the amplitude of the viscosity bifurcation, the larger the associated drop in G; and (3) the water content (w) deviation from the Atterberg liquid limit (LL) seem a key parameter controlling a common mechanical behavior of these soils at the solid-fluid transition. We propose exponential laws describing the evolution of the critical shear stress τ_c, the critical shear rate \( \dot{\gamma_c} \), and the shear modulus G as a function of the deviation w-LL.     

Compressive strength and microstructural analysis of unfired clay masonry bricks

This paper reports on the compressive strength and microstructure of unfired clay masonry bricks. Blended binders comprising of lime-activated Ground Granulated Blastfurnace Slag (GGBS) and Portland Cement (PC)-activated GGBS were used to stabilise Lower Oxford Clay (LOC) for unfired masonry brick production. The compressive strength of the stabilised bricks incorporating lime–GGBS–LOC was higher than that of PC–GGBS–LOC. Scanning Electron Microscopy (SEM) with a Solid-state Backscattered Detector (SBD) and Energy Dispersive X-ray (EDX) analysis was employed to obtain a view of the microstructure and to conduct an analysis on the morphology and composition of the dried unfired clay brick samples, after 28 days of moist curing. The analytical results together with the physical observations have shown the formation of Calcium Silicate Hydrate (C-S-H) gel and additional pozzolanic (C-S-H) gel. The quantification of the compound content of the unfired bricks showed the presence of Calcite (CaCO₃), Quartz (SiO₂), Alumina (Al₂O₃) and Wollastonite (CaSiO₈) crystals. Traces of other crystals were also detected.     

A new locality of palygorskite-rich clay from the southeastern Yucatán: a potential material source for environmental applications

A palygorskite unit was discovered in a road cut of undifferentiated Tertiary limestone between the villages of El Pariso and San Roman (18°49.309N, 88°37.861W) in the southeastern Yucatán Peninsula, Mexico. This is the southern most locality of a clay-rich sedimentary unit reported in the literature for the Tertiary carbonates of the Yucatán Peninsula. This occurrence indicates a much wider range of palygorskite-rich clay deposition than previously recognized. The lithology is 99% clay and 1% sand to silt size diagenetic quartz grains. The clay consists of approximately 85% palygorskite, 15% montmorillonite and trace amounts of titanium oxides. EDS analyses on palygorskite are largely consistent with sedimentary palygorskites from other coastal marine settings, however palygorskite has a low total Fe content (average = 0.40 wt% expressed as Fe₂O₃) compared to many other sedimentary palygorskites. Montmorillonite chemical compositions are typical and compared to the palygorskite have substantially higher Fe₂O₃ concentrations (average = 3.90 wt%). The low percentage of coarse grains in the lithology combined with a high proportion of palygorskite and lack of detrimental trace minerals suggest the deposit is of industrial grade; however, it has limited reserves (6,000 m³). The unit could be potentially used in a wide array of environmental applications which are needed in the region including liners for landfills and constructed wetlands. The unit is in a geographic location which would serve the expanding economy of the region. This resource has the potential to have great impact on the quality of the local environment and the economy of a region under great environmental threat.     

The Effect of Heavy Tamping on Structured Residual Clay Site

This paper examines the effect of heavy tamping (dynamic compaction) on highly porous structured residual clayey soil. The aim of this study is to analyse the feasibility of this technique when applied on lightly bonded residual soil sites, which are commonly found in tropical and subtropical regions. This soil has some interesting characteristics, such as high fine grain soil percentages (56% clay and 22% silt), a plastic index of 11%, high porosity (initial void ratio of 1.21), high hydraulic conductivity (about 10^?5 m/s) and a high stiffness at small strains (E?=?49.2-MPa). The research involves field [Cone Penetration Test (CPT) and the dynamic compaction] and laboratory (triaxial tests, characterization and hydraulic conductivity) investigation. According to laboratory tests, the void ratio decreased to 0.96, hydraulic conductivity decreased to 2.8?×?10^?7 m/s, the effective peak friction angle (?′) increased from 30.5° (in natural conditions) to about 35.5°, and the triaxial stiffness at small strains decreased to E?=?20-MPa due to dynamic compaction. CPT results have shown an improved depth in which CPT tip strength (q_t) increased from nearly 650-kPa to an average of 1700-kPa and CPT sleeve friction (f_s) increased from approximately 50-kPa to about 130-kPa. Horizontal displacements were observed up to about 4.0 m of depth (approximately the same depth at which CPT results showed soil improvement). It was concluded that heavy tamping reduces soil voids and substantially increases soil strength, but also breaks soil structure and decreases soil stiffness. It is thus not a suitable ground improvement solution for highly porous structured residual clayey soil.

     

Melt impregnation phases in the mantle section of the Ślęża ophiolite (SW Poland)

The ultramafic member of the Variscan Ślęża Ophiolite (SW Poland) consists of heavily serpentinised, refractory harzburgites. Those located down to 1.5 km below paleo-Moho contain scarce grains or aggregates of olivine, clinopyroxene and spinel. Non-serpentine phases occur in various assemblages: M1—olivine (Fo 90.2–91.0%, NiO 0.38–0.47 wt.%) and rounded or amaeboidal aluminous chromite, rimmed by Al poor chromite and magnetite; M2—olivine (Fo 90.5–91.5, NiO 0.32–0.44 wt.%), olivine with magnetite inclusions (Fo 87.1–92.5, NiO 0.01–0.68 wt.%), rounded, cleavaged clinopyroxene I (Mg# 91.1–93.2, Al₂O₃ 3.00–4.00 wt.%, Cr₂O₃ 1.00–1.40 wt.%) and elongated clinopyroxene II and clinopyroxene from symplectites with magnetite (Mg# = 92.2–94.1, Al₂O₃ 2.20–3.20 wt.% and Cr₂O₃ 0.80–1.20 wt.%). Clinopyroxene is depleted in REEs relative to chondrite. The M3 assemblage consists of intergrown olivine (Fo 90.8–92.7, NiO 0.20–0.38 wt.%) and clinopyroxene (Mg# = 96.0–98.1, Al₂O₃ 0.00–1.00 wt.% and Cr₂O₃ 0.20–0.60 wt.%).The M1 assemblage contains chromite which records greenschist-facies metamorphism. Textural relationships and chemical composition of clinopyroxene occurring in the M2 assemblage are similar to those formed in oceanic spreading centres by LREE depleted basaltic melt percolation. Olivine occurring in M1 assemblage and part of that from M2 have composition typical of residual olivine from the abyssal harzburgites and of olivine formed in those rocks by melt percolation. The olivine with magnetite inclusions (M2 assemblage) and that from M3 record later deserpentinization event, which supposedly produced also M3 clinopyroxene. The non-serpentine phases from the Ślęża ophiolite mantle member, albeit very poorly preserved, document depleted basaltic melt percolation in the Variscan oceanic spreading centre.