Applied Clay Science 101 (2014) 168–176 Contents lists available at ScienceDirect Applied Clay Science journal homepage: www.elsevier.com/locate/clay Research paper Characterization of Fe-smectites and their alteration potential in relation to engineered barriers for HLW repositories: The Nui Nua clay, Thanh Hoa Province, Vietnam Lan Nguyen-Thanh a,b, Thao Hoang-Minh c,⁎, Jörn Kasbohm b, Horst-Jürgen Herbert d, Duong Nguyen Thuy c, Lai Le Thi e a Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Germany Institut für Geographie und Geologie, Ernst-Moritz-Arndt-Universität, Greifswald, Germany c Hanoi University of Science, Vietnam National University, Hanoi, Viet Nam d Gesellschaft für Anlagen- und Reaktorsicherheit mbH, Braunschweig, Germany e Institute of Geological Sciences, Vietnamese Academy of Science and Technology, Viet Nam b a r t i c l e i n f o Article history: Received 24 December 2012 Received in revised form 17 June 2014 Accepted 28 July 2014 Available online 15 August 2014 Keywords: Fe-smectite Fe-montmorillonite Kinetic experiment Alteration HLW repository a b s t r a c t The stability of smectite-rich clay minerals is of interest because they could be candidates for engineered barriers for high-level radioactive waste repositories This research characterized the chemical and mineralogical properties of the Nui Nua clay which forms from the weathering of the Nui Nua serpentinized ultramafic–mafic massif (Thanh Hoa Province, Viet Nam) using several methods (including Fourier transform infrared spectrometry and transmission electron microscopy) The Nui Nua clay, taken from Co Dinh and My Cai valleys, is composed of Fesmectites as the main phase with minor phases of normal smectite, quartz, talc, chlorite, kaolinite, amphibole, antigorite, feldspars and magnetite The Fe-smectites were characterized as mixed-layer minerals (including Fe-montmorillonitic as an end-member) composed of illitic or dioctahedral vermiculitic layers and Fe-rich smectitic layers The proportion of the smectitic layer is approximately 80%; the interlayer sheet is dominated by Ca and Mg, while the octahedral sheet is dominated by Fe3+ (not Al) The stability of the Nui Nua smectites was also investigated by a simulation in saturation of M NaCl and deionized water under kinetic impaction The average tetrahedral-Si content of the smectites increased or decreased depending on the “dynamic solution” or hydraulic regime By chemical identification, the alteration of Fe-smectites is mainly increased by the smectitization process This research suggests that the Nui Nua clay is a potential candidate for an engineered barrier because during the alteration process, neo-formation of a montmorillonitic layer occurs © 2014 Elsevier B.V All rights reserved Introduction Montmorillonite is well known as an octahedral Al-dominating smectite, whereas nontronite is known as an octahedral Fe-dominating smectite (Brindley, 1980; Güven, 1988; Moore and Reynolds, 1997; Newman, 1987) Smectites containing more than 0.3 Fe per [O10(OH)2] are considered as Fe-rich smectites or Fe-rich montmorillonite (Brigatti, 1983; Güven, 1988) These minerals are formed mostly from serpentinized ultramafic rock (Aleta et al., 2002; Caillaud et al., 2004, 2006; Ducloux et al., 1976; Köster et al., 1999; Lee et al., 2003; Seki and Yurdakoỗ, 2007; Wildman et al., 1968, 1971) In a weathering profile of serpentinite rock, it has been observed that dioctahedral smectite is more stable than trioctahedral smectite and ⁎ Corresponding author at: 334 Nguyen Trai Road, Thanh Xuan District, Hanoi, Viet Nam Tel.: +84 38585097; fax: +84 38583061 E-mail address: hoangminhthao@vnu.edu.vn (T Hoang-Minh) http://dx.doi.org/10.1016/j.clay.2014.07.032 0169-1317/© 2014 Elsevier B.V All rights reserved Fe-montmorillonite, which was replaced with saponite (Wildman et al., 1971) The formation of low-charge Fe-montmorillonite in a weathering profile of serpentine rock is very rapid under tropical monsoon climate conditions and results in several centimeters of formation depth above the local bedrock surface as described by Schnellman (1964) A substitution of trioctahedral silicates (e.g saponite) by dioctahedral silicates (e.g low-charge illite/smectite mixed-layer mineral) and an Fe-pathway of a weathering profile of serpentine rock was also determined by Nguyen-Thanh (2012) These findings were based on research on clay in the Nui Nua area, Thanh Hoa Province, Viet Nam There has been interest in the use of the clay as engineered barriers for a high-level radioactive waste (HLW) repository because the government of Viet Nam has decided to erect nuclear power plants in the next ten years to guarantee electricity supply for the future Smectitic clay is well known as a material for engineered barrier systems (EBS) for HLW repositories because of its engineering properties that can meet many of the required functions (Pusch, 1992; Pusch and Yong, 2006) However, in considering candidate materials for an EBS, L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 it is necessary to assess the stability of all the mineral components, including smectite which forms a substantial proportion of the Nui Nua clay It is primarily the shearing processes associated with movements of the host rock and tension-related expansion of the clay embedding canisters (made of pure iron or iron lined with 50 mm copper on the contact surface) which can fracture the waste canisters exposing the clay to iron (Fe) Iron-related corrosion can accelerate the alteration processes in the smectite by replacing the octahedral sheet of the smectite (Herbert et al., 2011; Nguyen-Thanh, 2012) Increased octahedral Fe has been demonstrated in laboratory experiments (Charpentier et al., 2006; Herbert et al., 2011; Ishidera et al., 2008; Müller-Vonmoss et al., 1991; Nguyen-Thanh, 2012), modeling studies and natural analogs of clay weathering (Herbert et al., 2011; Nguyen-Thanh, 2012; Savage et al., 2010; Wilson et al., 2006a,2006b) Groundwater in the local environment of a HLW repository is likely to have large concentrations of dissolved Ca2+ and Na+ (or even K+ and Mg2+) because of upwelling of saline ground water or extraction of salt from cements (Pearson et al., 2003; Stober and Bucher, 2002) The Alrich smectites may not be stable in this environment (Adamcova et al., 2008; Bauer et al., 2001; Castellanos et al., 2008; Eberl et al., 1978; Hoffman et al., 2004; Herbert et al., 2004, 2008; Karnland et al., 2007; Kaufhold and Dohrmann, 2009, 2010; Suzuki et al., 2008; Zysset and Schindler,1996) Alternatively, this could lead to Si-precipitation and cementation of the smectite forming collapsed quasi-crystals and wider pores (Pusch et al., 1991, 2007) Some researches detected the illitization, kaolinitization and pyrophylitization of the smectite (Herbert et al., 2004; Kasbohm et al., 2004) and several studies have identified changes in the geotechnical properties of smectite including cation exchange capacity, swelling and adsorption capacities (Adamcova et al., 2008; Hofmann et al., 2004; Suzuki et al., 2008; Weiss and Koch., 1961) However, the stability of Fe-rich smectite has not been considered Therefore, this research on the Nui Nua clay, which is a product of natural weathering processes of the serpentinized ultramafic–mafic massif, was performed in order to determine the chemical and mineralogical properties of the smectite The research also investigated the stability of this smectite phase, specifically in relation to simulation of reactions relating to the use of this material as a HLW repository through saturation in M NaCl and deionized water under kinetic impaction Geological setting and materials 169 2.2 Materials The physical samples used in this research were taken in the My Cai and Co Dinh valleys, which are situated in the northeastern part of the Nui Nua massif (Fig 1) The clay body in My Cai is thicker than that in Co Dinh, but both the clays are homogenous and brownish-yellow in color Based on application of the Atterberg sedimentation method, the two clay samples are composed of 65.8–67.3 mass% of the b μm particle size fraction, 19.5–20.0 mass% of 6.3–2 μm fraction, 12.3–12.8 mass% of 6.3–20 μm fraction and only 0.9–1.2 mass% of 20–63 μm fraction; particles with diameters N63 μm could not be detected Experiments and methods 3.1 Kinetic experiments The kinetics of Fe- and Mg-driven alteration processes of the Nui Nua clay as well as the potential of alteration of Fe-smectite were investigated The aim of these experiments was to focus on alteration processes in buffer materials of HLW repositories containing canisters made of iron The hypothesis this research wishes to test concerns the alteration rate of Fe-smectite based on the proposal by Čičel and Novak (1976) that large amounts of Fe and Mg in the octahedral sheet of smectite can accelerate the alteration process The larger ionic diameters of Fe and Mg in comparison with Al may well be responsible for larger sheet stresses, which facilitate dissolution of the smectites The other mechanism proposed by Laird (2006) and Kaufhold and Dohrmann (2008) concerning this process, is the space stabilization of Ca2+ and Mg2+ cations as quasi-crystals in the interlayer The Co Dinh clay samples, ground to b40 μm, were saturated in M NaCl solution and deionized water with a “liquid:solid” ratio of 4:1 and 10:1, respectively for 30 days, followed by the application of soft gels for mechanical agitation by overhead rotating at room temperature at 20 revolutions per minute (rpm) and 60 rpm The higher the speed of overhead rotating, the greater the energy, which leads to the removal of dissolved elements from the particles It is expected that at 60 rpm, the number of dissolved elements removed was higher than that at 20 rpm The reaction products of experiments of saturation in M NaCl solution were dialyzed using the QuickStep-system for mg material in approximately h Below, these products are referred to as Co Dinh clay + M NaCl + 20 rpm and Co Dinh clay + M NaCl + 60 rpm as well as Co Dinh clay + H2O + 20 rpm and Co Dinh clay + H2O + 60 rpm 2.1 Geological setting 3.2 X-ray fluorescence (XRF) spectroscopy The Nui Nua clay deposits are located in the Thanh Hoa Province, in the northern Central region of Viet Nam (Fig 1) The clay is related to the Nui Nua massif The biggest ultramafic–mafic massif in Viet Nam is well known as part of the Song Ma ophiolite zone (Bach et al., 1982; Chuong et al., 2001; Findlay and Trinh, 1997; Hung, 1999; Hutchison, 1975) and is associated with a series of economically important chromite and serpentine mines in this area (Tri, 2005; UNP, 1990) The massif is composed mainly of dunite, harzburgite, lerzolite, gabbro and diabase of Cambrian and Ordovician age (Chien, 1964; Khuc, 2000; Lien, 1980; Thang et al., 1999; Thanh et al., 2005; Thuc and Trung, 1995; Tri, 1979; Tri et al., 1986; Vuong et al., 2006) and was altered to serpentinite and schist of actinolite and talc-actinolite by serpentinization during the Cambrian period (Chien, 1964; Son et al., 1975; Tong-Dzuy and Vu, 2011) More recently (less than million years before present), the Nui Nua rocks have undergone preQuaternary erosion and Quaternary weathering (Tong-Dzuy and Vu, 2011) The weathering continued under tropical climatic conditions creating a large amount of Fe-rich minerals including Fe-rich smectite The Nui Nua clay was concentrated by re-sedimentation in two big valleys, My Cai and Co Dinh (Fig 1) Using the material collected from the field sites, the bulk materials (milled to b40 μm) were analyzed by XRF spectroscopy using a wavelength-dispersive X-ray Philips PW 2404 spectrometer equipped with a kW Rh X-ray source (10 mA, 20 kV) The analyses used a non-wetting agent and/or oxidizer Loss on ignition (LOI) was determined at 1100 °C as an approximate measure of volatile H2O 3.3 X-ray diffraction (XRD) The mineralogical composition of randomly oriented powder samples with b40 μm size fraction of the Nui Nua Fe-rich clay was investigated using a Siemens D5000 X-ray diffractometer (Cu tube, Kα1,2 radiation, 40 kV, 30 mA) Oriented mounts with b μm size fraction including air-dried, ethylene glycolated, and heated (to 550 °C for h) specimens were investigated with a Freiberg Präzitronic diffractometer HZG 4A-2 equipped with a Seifert C3000 control unit (Co tube, Kα1,2 radiation, 30 kV, 30 mA) The XRD data were processed using BGMNRietveld software (Bergmann et al., 1998; Kleeberg et al., 2005; Ufer et al., 2004, 2008) in cross-checking with the XRF results 170 L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 3.4 Fourier transform infrared spectrometry (FT-IR) Infrared spectra of bulk samples milled to b 40 μm were recorded in the mid-infrared range, which extends from 400 cm−1 to 4000 cm−1, using a Nicolet 6700 FT-IR spectrometer (64 scans, cm−1 resolution) The FT-IR spectra were deconvoluted by an Origin Pro Peak Fitting (version 8.5) technique A Gaussian distribution function was applied to smooth the spectra and to obtain exact values of peak positions, full width at half maximum (FWHM), intensity and area The baseline correction of two wavenumber regions surrounding 970 cm−1 and 720 cm−1 was subtracted by the same technique The accuracy of the deconvolution was assessed by the adjustment of peak position to achieve an R2 N 0.98 The stable adjustment was documented by the positions of a band of quartz at ~795 cm−1 and of a significant doublet of quartz at 780 and 800 cm−1 (Farmer, 1974; Craciun, 1984) 3.5 Transmission electron microscopy (TEM) Selected individual clay particles were characterized by their morphology, crystal habit, chemical composition, electron diffraction properties, and element distribution using a JEOL JEM-1210 microscope (120 kV, LaB6 cathode) coupled to an ISIS LINK-OXFORD energydispersive X-ray (EDX) system Suspension of clay samples was prepared on carbon-coated Cu-grids by air-drying The particle morphologies were described according to Henning and Störr (1986) Mineral formulae were calculated using the semi-quantitative data of approximately 150 particles per sample based on the theory of Köster (1977) and the software toolkit of Kasbohm et al (2002) In this study, any illite identified during TEM-EDX analyses is referred to as illite in the sense of Środoń et al (1992); specifically conforming to the following structural formula: FIX0.89(Al1.85Fe0.05 Mg0.10)(Si3.20Al0.80)O10(OH)2 where: FIX represents fixed K + Na cations in the interlayer space Furthermore, K- and/or charge-deficient dioctahedral micas, with tetrahedral Si b 3.3 per O10(OH)2, are referred to as dioctahedral vermiculite The acronyms “IS-ml” and “diVS-ml” refer to an illite/smectite mixed-layer and a dioctahedral vermiculite/smectite mixed-layer, respectively Minerological characterization of Nui Nua clay Bulk chemical compositions of the two clays, as determined by XRF spectroscopy, are presented in Table The My Cai clay contains the larger concentrations of SiO2 and MgO and smaller Al2O3 and Fe2O3 concentrations in comparison with the Co Dinh clay The Fe2O3 concentrations (23.3 mass% for the My Cai clay and 25.5 mass% for the Co Dinh clay) are comparable to the former publications about the Nui Nua clay by Binh and Duc (1998), Lam et al (1998), and Khai and Tau (2003) Such large Fe2O3 concentrations are comparable with that of the Fe-rich Saint-Laurent, Limousin, France (24.4%, lower saprolite zone) (Caillaud et al., 2004), and higher than the Fe2O3 concentrations of the Fe-rich Çamlıca clay, Turkey (9.97% and 12.12%) (Seki and Yurdakoỗ, 2007) The XRD patterns of the Co Dinh and My Cai powder samples (Fig 2) verified the presence of smectite-phases with peaks at 15.4 Å, 4.51 Å, 2.58 Å, 2.26 Å, 1.71 Å and 1.51 Å The occurrence of the following mineral phases was demonstrated by specific XRD positions (as Å units): anitogorite (7.32 Å), quartz (4.26 Å, 3.34 Å, 1.82 Å, 1.54 Å and 1.46 Å), amphibole (3.14 Å, 2.71 Å) and magnetite (2.53 Å) The 15.4 Å basal spacing at room temperature indicated that interlayer space of the smectite is dominated by divalent cations The XRD patterns showed that mineral compositions of these two clay samples from the Co Dinh and My Cai valleys are similar Semi-quantitative mineral compositions of the bulk samples and of the b2 μm fraction samples of these two clays Fig Geological map of the Nui Nua massif and the two sampling locations Adapted from Bach and Quan (1995) L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 171 Table Chemical composition (mass%) of Nui Nua clay Sample SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 LOI Sum My Cai clay Co Dinh clay 49.71 47.67 0.37 0.35 5.99 6.24 23.3 25.5 0.36 0.30 9.34 9.01 1.01 0.66 0.11 0.08 0.36 0.31 0.03 0.03 8.28 8.99 98.86 99.14 are presented in Table Smectite is the dominant mineral phase and its proportion increased significantly from the bulk samples (65–70 mass%) to the b2 μm fraction samples (85–87 mass%) Based on the XRD patterns of the oriented specimens (NguyenThanh, 2012) and calculation of the proportion of illitic layers in the illite/smectite mixed-layer mineral (according to Moore and Reynolds, 1997), the Nui Nua smectite was characterized as an illite/smectite mixed-layer series with around 10% illitic layers The positions of the d06–33 peaks at 1.51 Å indicated that the clay samples contain Fe-rich dioctahedral smectite (Caillaud et al., 2004; Köster et al., 1999; Petit et al., 2002; Seki and Yurdakoỗ, 2007) Mineral characteristics of the two clays were investigated in greater detail by TEM-EDX and shown in Fig 3a and Table Most often, the clay particles of the Nui Nua clay samples presented xenomorphic form, with less distinct edges and aggregates Some particles were present as separate laths Based on the electron diffraction analyses, the Nui Nua clay showed mainly ring-like polytype structure (Fig 3a), which is typical for smectite phases Based on the results from TEM-EDX analyses, the particles can be divided into two groups based on their structural chemical composition The first group was identified as the illite/smectite mixed-layer series including Fe-montmorillonite as the end-member containing the majority of Fe in the octahedral sheet The second group was characterized as the dioctahedral vermiculite/smectite mixed-layer phase including the Fe-rich dioctahedral vermiculite/smectite mixed-layer series (Fe-diVS-ml) and the Al-rich dioctahedral vermiculite/smectite mixed-layer series (Al-diVS-ml) The Al-diVS-ml particles with both tetrahedral and octahedral charges can be assumed composed of a smectitic layer, which is intermediate between an Fe-montmorillonite endmember and beidellite (or nontronite) (Christidis, 2006; Petit et al., 2002) The ratio of the number of the Al-diVS-ml particles and the number of the Fe-diVS-ml was approximately 1:9 for both clays According to Środoń et al (1992), the Fe-rich smectite from the Nui Nua clay belongs to the low-charge mixed-layer phases containing large proportions of montmorillonitic layers; these were mostly 40–80% for the diVS-ml phases and ~100% for the IS-ml series (Table 3) The octahedral sheets of most particles are dominated by Fe, but also contain traces of Cr3+ A comparison of the Co Dinh and My Cai clays shows that the former is characterized by a higher K index, corresponding to a lower interlayer charge and a diVS-ml series with a higher Fe index in the octahedral sheet Further information on the mineral composition was obtained by the FT-IR method The FT-IR spectra (Fig 4) of bulk samples from the Co Dinh and My Cai clays verified the presence of the Fe-smectite based on the strong absorption bands of the OH-stretching region at 3548 cm−1 and 3554 cm−1, respectively (Bishop et al., 2002; Caillaud et al., 2004; Farmer and Russell, 1964; Fialips et al., 2002; Goodman et al., 1976; Madejová and Komadel, 2001; Petit et al., 2002; Vantelon et al., 2001) These publications related these absorption bands to Fe3+\OH\Fe3+ The weak spectral bands observed near 3625 cm−1 were due to stretching vibrations of the Al\OH\Al stretching of octahedral sheet of smectite (Andrejkovičová et al., 2006; Farmer, 1974) Moreover, the other weak bands at 3683 cm− (from My Cai clay) and 3675 cm− (from Co Dinh clay), can be assigned to either Al\OH\Mg stretching of the octahedral smectite sheet (Farmer, 1974) or νMg3OH stretching of trioctahedral occupancy (Caillaud et al., 2004; Decarreau et al., 1992; Petit et al., 2002) In some publications, such as Farmer (1974) and Madejová and Komadel (2001), these bands were interpreted to OH-stretching of inner hydroxyl groups of kaolinite, but the peaks must be sharper Based on the bending region, the Fe3+\OH\Fe3+ bending vibration at 818 cm−1 represents the large content of Fe3+ in the octahedral sheet of smectite (Fialips et al., 2002; Goodman et al., 1976) was observed for both clays The bands observed at 870 cm−1 and 910 cm−1 (My Cai clay) as well as 870 cm−1 and 913 cm−1 (Co Dinh clay) were assigned to the Al\OH\Al and Al\OH\Fe bending bands, respectively In regard to other regions, the spectral feature observed at 1632 cm−1 from both clays demonstrated the presence of the H\O\H bending vibrations at the smectite phase (Seki & Yurdakoỗ, 2007) The tetrahedral Si\O\Al bending and the tetrahedral Si\O\Si bending bands appeared at 519 cm−1 and 465 cm−1 (from My Cai clay) and 515 cm−1 and 467 cm−1 (Co Dinh clay) Additionally, the strong spectral bands at 1023 cm−1 (from My Cai clay) and 1021 cm−1 (from Co Dinh clay) were attributed to typical Si\O stretching vibrations of smectites (Bishop et al., 2002; Madejová and Komadel, 2001) or Fe-rich smectites (Fialips et al., 2002) The bands at 778 cm− and 798 cm− were also typically interpreted to Si\O stretching of quartz (Madejová and Komadel, 2001; van der Marel and Beutelspacher, 1976; Vantelon et al., 2001) This evidence indicated that in the Nui Nua clay, the characteristics of the smectite phase was dominantly characterized by the quantity of Fe3 + and also the minor amount of Al in the octahedral sheet The Fig XRD patterns of a) Co Dinh clay (above), and b) My Cai clay (below) in samples from randomly oriented powder, °2Θ CuKα position 172 L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 Table Mineralogical composition (in mass%) of bulk and b2 μm fraction samples of untreated Co Dinh and My Cai clays as well as Co Dinh clay after kinetic experiments, determined from XRD data with the BGMN-Rietveld software Phases Smectite Kaolinite Quartz Chlorite Talc Amphibole Antigorite Feldspars Magnetite My Cai clay (untreated) Co Dinh clay after kinetic experiments (b2 μm fraction) Co Dinh clay (untreated) Bulk sample b2 μm fraction Bulk sample b2 μm fraction Co Dinh clay + 1M NaCl + 20 rpm Co Dinh clay + 1M NaCl + 60 rpm 65 12 10 Trace Trace Trace 85 4 b1 Trace – Trace 70 8 Trace Trace Trace 87 4 – Trace – Trace 86 2 Trace Trace 87 5 Trace b1 Trace Trace Trace Note: Smectite comprises mainly Fe-montmorillonite, illite/smectite mixed-layer mineral and dioctahedral vermiculite/smectite mixed-layer mineral, which were verified by TEM measurement Al\OH\Mg (bending) bond was not observed in both clays; this could be explained by the relatively low Mg content in the octahedral sheet Therefore, the identified spectral bands of Mg were due to the presence of local trioctahedral magnesian clusters within the dioctahedral Fe3+ and Mg-rich matrix (Petit et al., 2002) In conclusion, based on the good agreement among the reported results by XRD, TEM-EDX and FT-IR studies, the Nui Nua clay (including clays from the Co Dinh and My Cai valleys) formed as the weathering products of the serpentinized ultramafic–mafic Nui Nua massif (Thanh Hoa Province, Vietnam) was characterized by the dominant of lowcharge Fe-smectite The impurities detected in both clay samples included quartz, chlorite, talc, kaolinite, amphibole, antigorite, feldspars and magnetite There is only a small difference between the Co Dinh and the My Cai clay in regard to structural formulae of the smectite as well as chemical and mineralogical compositions From both types of bulk sample and b2 μm sample fraction, the Co Dinh clay was characterized by a larger amount of smectite and a smaller quantity of quartz in comparison with the My Cai clay (Table 2) By contrast with the My Cai clay, measurements on samples of the Co Dinh clay showed that there were slightly smaller concentrations of MgO (Table 1), lower Mg-index values from the structural formulae (Table 2) and a smaller quantity of Mg associated with the less intensive band of νMg3OH stretching vibration (Fig 4) In contrast, the Co Dinh clay was characterized by a higher Fe2O3 mass% (Table 1), a higher Fe3+ amount in the octahedral sheet yielded from TEM-EDX analyses (Table 3) and more intensive bands of Fe3+\OH\Fe3+ stretching and bending vibrations Kinetic experiments: minerological characterization of the Nui Nua clay The Co Dinh clay was selected for kinetic experiments because of its verified larger content of Fe-smectite, larger Fe2O3 mass% and larger Fe3 + quantity in the octahedral sheet of the smectite by comparison to the My Cai clay The XRD curves of the randomly oriented specimens from the reaction products indicated that Fe-smectite is still the main mineral phase after the experiments (Nguyen-Thanh, 2012) The XRD quantitative study of mineralogical composition determined that the Fig TEM bright-field (above) and electron diffraction (below) images of a) Co Dinh clay (untreated ), b) Co Dinh clay + M NaCl + 20 rpm, and c) Co Dinh clay + M NaCl + 60 rpm L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 173 Table Mineral formulae (cations per [O10(OH)2]) of clay mineral phases from untreated My Cai and Co Dinh clays as well as Co Dinh clay after kinetic experiments, determined by TEM-EDX analyses Phases Interlayer space Octahedral sheet Tetra sheet Ca Mg Na K Cr3+ Al Fe3+ Mg Ti Al Si XII nVI My Cai clay (untreated) Fe-IS-ml Fe-diVS-ml Al-diVS-ml average 0.03 0.02 0.01 0.02 0.08 0.08 0.12 0.08 0.00 0.00 0.00 0.00 0.15 0.13 0.16 0.15 0.06 0.05 0.04 0.05 0.50 0.57 1.39 0.61 1.17 1.20 0.49 1.11 0.22 0.16 0.07 0.19 0.01 0.02 0.01 0.01 0.06 0.16 0.37 0.12 3.94 3.84 3.63 3.88 0.37 0.31 0.43 0.35 1.96 2.00 2.00 1.97 97 78 44 85 Co Dinh clay (untreated) Fe-IS-ml Fe-diVS-ml Al-diVS-ml average 0.07 0.03 0.08 0.04 0.07 0.11 0.14 0.10 0.00 0.00 0.00 0.00 0.02 0.03 0.05 0.04 0.04 0.09 0.03 0.08 0.48 0.46 1.48 0.56 1.19 1.25 0.39 1.16 0.16 0.16 0.09 0.17 0.01 0.04 0.01 0.03 0.03 0.19 0.40 0.19 3.97 3.81 3.60 3.81 0.30 0.32 0.50 0.32 1.88 2.00 2.00 2.00 100 73 40 73 Co Dinh clay after kinetic experiments Co Dinh clay + M NaCl + 20 rpm Co Dinh clay + M NaCl + 60 rpm Co Dinh clay + H2O + 20 rpm Co Dinh clay + H2O + 60 rpm 0.02 0.04 0.02 0.03 0.13 0.07 0.11 0.13 0.00 0.02 0.00 0.00 0.04 0.06 0.05 0.02 0.03 0.10 0.03 0.05 0.59 0.48 0.58 0.55 1.21 1.20 1.18 1.13 0.15 0.18 0.19 0.23 0.02 0.02 0.01 0.02 0.21 0.06 0.10 0.11 3.79 3.94 3.90 3.89 0.35 0.30 0.31 0.34 2.00 1.98 1.99 1.98 68 97 89 87 S% Note: the values are average of measured particles; Fe-IS-ml included high-charge and medium-charge Fe-montmorillonite as end-member; Fe-diVS-ml and Al-diVS-ml included lowcharge Fe-montmorillonite and low-charge Al-montmorillonite as end-members, respectively; average was calculated for Fe-IS-ml, Fe-diVS-ml and Al-diVS-ml; XII: interlayer charge, nVI: number of octahedral occupation, S%: proportion of montmorillonitic layer b2 μm fraction of the reaction products contain more than 85 mass% of Fe-smectite (Table 2) The TEM analyses revealed that the initial Fe-smectite particles were changed in morphology and polytype The products presented the finer aggregates and rearranged as mainly M-polytype (Co Dinh clay + M NaCl + 20 rpm, Fig 3b) and ring-like polytype (Co Dinh clay + M NaCl + 60 rpm, Fig 3c) The structural formulae of the smectites are presented in Table The obvious changes of Si indexes of the tetrahedral sheet or proportion of the smectitic layer (S%) (calculated according to Środoń et al., 1992) as well as the accompanied interlayer charge were identified The changes were also observed using the FT-IR method, wherein the higher Si contents in the tetrahedral sheet and the higher wavenumber values of the Si\O stretching-vibration band (around ~1000 cm−1 and ~1100 cm−1; Farmer, 1974; Lerot and Low, 1976; Stubičan and Roy, 1961) were observed Fig shows a linear relationship between the Si indexes of the tetrahedral sheet calculated from TEM-EDX data and the wavenumber Fig FT-IR spectra of Co Dinh and My Cai clay samples 174 L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 values of the Si\O stretching-vibration band fitted using the FT-IR data This verified that the TEM-EDX and FT-IR data are in agreement and the changes of smectites after the similar kinetic experiments are consistent with this trend Two processes are postulated to occur during the kinetic experiment The first, which occurred in only two experiments using M NaCl solution, is an alteration process affecting smectite in the NaCl solution with the “open” dynamic system described by Pusch and Kasbohm (2002) This process leads to a reduction of Si concentrations The second process is the dissolution of smectite, followed by the removal of Si, and finally representing a new montmorillonitic layer This process, called “dynamic solution”, depends on the flow rate of overhead rotating or the energy of the hydraulic regime; the lower the flow rate, the larger the amount of dissolved Si resulting in neoformed montmorillonite The alteration is mentioned by Pusch et al (1991, 2007) and can be proven by the occurrence of finer aggregates of smectite under TEM observations (Fig 3b, c) The observation of the lower tetrahedral Si of smectite in the Co Dinh clay + M NaCl + 20 rpm (Table 3, Fig 5) demonstrates that the first alteration process was dominant With the Co Dinh clay + H2O + 20 rpm, there was only “dynamic solution” at the low energy, so that the tetrahedral Si content was slightly increasing in comparison with the starting material When the speed of overhead rotating was increased to 60 rpm, the influence of “dynamic solution” was more significant in comparison to the alteration by salt solution Therefore, the Co Dinh clay + M NaCl + 60 rpm and the Co Dinh clay + H2O + 60 rpm resulted in a larger tetrahedral Si concentration (or S%) in comparison with the starting material (Table 3, Fig 5) Conclusions Under tropical monsoon climate conditions, low-charge Femontmorillonite is formed very rapidly by weathering of serpentine rock This study of the Nui Nua clay (formed from the weathering of the Nui Nua serpentinite, Viet Nam) based on chemical, TEM-EDX, XRD, FT-IR analyses indicated that the clay contains mainly smectite, including Fe-smectite and normal smectite (N65 mass% of bulk samples and N85 mass% of b2 μm fraction samples) and impurities of quartz, chlorite, talc, amphibole, kaolinite, antigorite, feldspars and magnetite (Table 2; Figs 2, 3a, 4) The Fe-smectite phases were specifically characterized as mixed-layer minerals (including Fe-montmorillonitic as endmember) composed of illitic or dioctahedral vermiculitic layers and a Fe-rich smectitic layer In regard to the Fe-smectite, the proportion of the smectitic layer (%S) is 80%, while the remainder is formed from an interlayer sheet dominated by Ca and Mg, and an octahedral sheet dominated by Fe3+ but not Al (Table 3; Fig 4) The normal smectite phase made up approximately 10% of all the smectite phases They were characterized as mixed-layer minerals with large proportions of smectitic layer phases, which is intermediate between Fe-montmorillonite endmember and beidellite (or nontronite), and a smaller quantity of Fe in comparison to the Fe-smectite phases By investigating the alteration processes of the Nui Nua clay using simulation by saturation in M NaCl and deionized water under kinetic impaction, this study showed that the smectite phase of the Co Dinh clay (Nui Nua clay) could be altered by two processes which have implications for its potential use as an engineering barrier The first is an alteration process due to the NaCl solution which influences the smectite phase, and the second one is “dynamic solution” The “dynamic solution” process, which leads to the dissolution of smectite then removal of Si, and finally leading to neo-formed montmorillonite, depends strongly on flow rate of the overhead rotating activity Each smectite may have a specific alteration potential, which was observed with some other clays such as the MX-80 and the Friedland clay (Herbert et al., 2011; Nguyen-Thanh, 2012) With the Fe and Mg-rich octahedral sheet and bivalent cation-dominated interlayer sheet, the Co Dinh Fe-smectite has a high alteration or dissolution potential because the larger ionic radius of Fe and Mg compared to Al increases the mechanical stresses in the octahedral sheet (Čičel and Novak, 1976) and the larger proportion of divalent cations (e.g Ca, Mg) in the interlayer sheet promotes unmixing of monovalent and divalent interlayer cations or leads to the stabilization of quasi-crystals (Laird, 2006; Kaufhold and Dohrmann, 2008) The alteration processes may lead to the formation of a richer smectitic phase; the alteration process is smectitization This hypothesis is consistent with natural formation processes, which under ideal conditions leads to the complete alteration of serpentinite to montmorillonite This study also indicates that a clay dominated by Fe-smectite (illite/ smectite mixed-layer and dioctahedral vermiculite/smectite mixedlayer series) like the Nui Nua clay can be a good candidate for a buffer or backfill material of a HLW repository because clay-mineral alteration of this kind leads to neo-formation of montmorillonite which has effective barrier properties Otherwise, if we use Fe-smectite with a proportion of the smectitic layer (S%) of approximately 100% or pure Femontmorillonite as original material end-members, reaction processes will lead to Si-cementation or Si-clogging as described by Pusch and Touret (1988) This process would cement collapsed quasicrystals together and broaden the pores, which can allow other external agents to penetrate channel-like pathways into the clay and increase the hydraulic conductivity and the shear strength Acknowledgements We gratefully acknowledge the support from the National Foundation for Science and Technology Development, Vietnam (project code 105.02.54.09) We also thank the support from the Gesellschaft für Anlagenund Reaktorsicherheit (GRS) mbH and the Mineralogical Laboratories — University of Greifswald, Germany We are very grateful to Prof Reto Gieré (University of Freiburg, Germany) for the XRF data, Dr Le Thi Thu Huong for the FT-IR measurement, and Dr Barry Rawlins (British Geological Survey) for upgrading the use of English in the manuscript We also thank two anonymous reviewers and the associate editor for their evaluation References Fig Comparison between Si indexes of tetrahedral sheet (TEM-EDX) and wavenumber values of the Si\O stretching band (FT-IR) as proof for alteration of smectite after the kinetic experiments Symbols: gray-filled diamond: starting material (untreated Co Dinh clay); empty diamond: reaction products (Co Dinh clay after kinetic experiments) Adamcova, J.,Hanusova, I.,Ponavic, M.,Prikryl, R., 2008 Alteration processes in bentonites In: Stastny, M (Ed.), Book of Abstracts 18th Clay Conference in Czech Republic, p 19 Aleta, D.G.A.,Tomita, K.,Aleta, J.T.,Lucero Jr., A.R.,Kawano, M., 2002 Clay mineralogy of the weathered materials from the serpentinized peridotite in Minglanilla, Cebu Province, Phillippines Rep Fac Sci 35 Kagoshima Univ, pp 17–35 Andrejkovičová, S., Madejová, J., Czímeravá, A., Galko, I., Dohrmann, R., Komadel, P., 2006 Mineralogy and chemistry of Fe-rich bentonite from the Líekovec deposit (Central Slovakia) Geol Carpath 57 (5), 371–378 Bach, L.D., Quan, D.T (Eds), 1995 Geological and mineral resources map of Vietnam on 1:200 000 — Thanh Hoa E-48-IV sheet Department of Geology of Vietnam (in Vietnamese) Bach, L.D.,Chau, V.M., Hung, T.Q., Thanh, H.H., 1982 The Song Ma ophiolite J Earth Sci 4, 97–106 (in Vietnamese) L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 Bauer, A., Schäfer, T., Dohrmann, R., Hoffmann, H., Kim, J.I., 2001 Smectite stability in acid salt solutions and the fate of Eu, Th and U in solution Clay Miner 36, 93–103 Bergmann, J.,Friedel, P.,Kleeberg, R., 1998 BGMN — a new fundamental parameters based Rietveld program for laboratory X-ray sources, it's use in quantitative analysis and structure investigations Commission of Powder Diffraction, International Union of Crystallography CPD Newsletter 20, 5–8 Binh, L.D.,Duc, K.C., 1998 Quality characteristics and recommendation for use of bentonites in Vietnam J Econ Geol Miner Mater 14, 1–7 (Hanoi, Vietnam, in Vietnamese) Bishop, J.,Madejova, J.,Komadel, P.,Fröschl, H., 2002 The influence of structural Fe, Al and Mg on the infrared OH bands in spectra of dioctahedral smectites Clay Miner 37, 607–616 Brigatti, M.F., 1983 Relationships between composition and structure in Fe-rich smectites Clay Miner 18, 177–186 Brindley, G.W., 1980 Order–disorder in clay mineral structures In: Brindley, G.W., Brown, G (Eds.), Crystal Structures of Clay Minerals and their X-ray Identification Mineralogical Society, London, pp 125–195 Caillaud, J.,Proust, D.,Righi, D.,Martin, F., 2004 Fe-rich clays in a weathering profile developed from serpentine Clay Clay Miner 52 (6), 779–791 Caillaud, J.,Proust, D.,Righi, D., 2006 Weathering sequences of rock-forming minerals in a serpentinite: influence of microsystems on clay mineralogy Clay Clay Miner 54 (1), 87–100 Castellanos, E., Villar, M.V., Romero, E., Lloret, A., Gens, A., 2008 Chemical impact on the hydro-mechanical behavior of high-density FEBEX bentonite Phys Chem Earth 33, 5516–5526 Charpentiera, D., Devineau, K., Mosser-Ruck, R., Chathelineau, M., Villieras, F., 2006 Bentonite–iron interactions under alkaline condition: an experimental approach Appl Clay Sci 32, 1–13 Chien, N.V., 1964 Nui Nua ultramafic massif J Geol 31 (3), 3–6 (in Vietnamese) Christidis, G.E., 2006 Genesis and compositional heterogeneity of smectites Part III: Alteration of basic pyroclastic rocks — a case study from the Troodos Ophiolite Complex, Cyprus Am Mineral 91 (4), 685–701 Chuong, V.D., Tung, V.D., Thang, T.V., 2001 Mafic and ultramafic formations in ophiolite archs of Vietnam J Earth Sci 23 (3), 231–238 (in Vietnamese) Čičel, B.,Novak, I., 1976 Dissolution of smectites in hydrochloric acid I Half-time of dissolution as a measure of reaction rate 7th Conference on Clay Mineralogy and Petrology, Karlovy Vary, p 163 Craciun, C., 1984 Influence of the Fe3+ for Al3+ octahedral substitutions on the IR spectra of montmorillonite minerals Spectrosc Lett 17, 579–590 Decarreau, A.,Grauby, O.,Petit, S., 1992 The actual distribution of octahedral cations in 2:1 clay minerals: results from clay synthesis Appl Clay Sci 7, 147–167 Ducloux, J., Meunier, A., Velde, B., 1976 Smectite, chlorite and a regular interlayered chlorite–vermiculite in soils developed on a small serpentinite body, Massif Central France Clay Miner 11, 121–135 Eberl, D., Whiteney, G., Khoury, H., 1978 Hydrothermal reactivity of smectite Am Mineral 63, 401–409 Farmer, V.C (Ed.), 1974 The Infrared Spectra of Minerals (Monograph 4) Mineralogical Society, London Farmer, V.C., Russell, J.D., 1964 The infrared spectra of layer silicates Spectrochim Acta 20, 1149–1173 Fialips, C.-I., Huo, D., Yan, L., Wu, J., Stucki, J.S., 2002 Effect of Fe oxidation state on the IR spectra of Garfield nontronite Am Mineral 87, 630–641 Findlay, R.H., Trinh, P.T., 1997 The structural setting of the Songma region, Vietnam and Indochina–South China plate boundary problem Gondwana Res 4, 11–33 Goodman, B.A., Russell, J.D., Fraser, A.R., Woodhams, F.W.D., 1976 A Mössbauer and IR spectroscopic study of the structure of nontronite Clay Clay Miner 24, 52–59 Güven, N., 1988 Smectites In: Bailey, S.W (Ed.), Hydrous Phyllosilicates Mineralogical Society of America, Washington, DC, pp 497–560 Henning, K.H.,Störr, M., 1986 Electron Micrographs TEM, SEM of Clays and Clay Minerals Akademie Verlag, Berlin Herbert, H.J., Kasbohm, J., Henning, K.H., 2004 Long-term behaviour of the Wyoming bentonite MX-80 in high saline solutions Appl Clay Sci 26, 275–291 Herbert, H.J., Kasbohm, J., Sprenger, H., Fernandez, A.M., Reichelt, C., 2008 Swelling pressured of MX-80 bentonite in solutions of different ionic strength Phys Chem Earth 33, 327–342 Herbert, H.J., Kasbohm, J., Nguyen-Thanh, L., Meyer, L., Hoang-Minh, T., Xie, M., 2011 Fe-bentonite — Experiments and Modelling of the Interactions of Bentonites with Iron GRS-295 978-3-939355-72-4 Hofmann, H.,Bauer, A., Warr, L.N., 2004 Behaviour of smectite in strong salt brines under conditions relevant to the disposal of low- to medium-grade nuclear waste Clay Clay Miner 52 (1), 14–24 Hung, T.Q., 1999 Early Paleozoic ultramafic formations in Bac Trung Bo, Vietnam J Earth Sci 21 (2), 119–122 (in Vietnamese) Hutchison, C.S., 1975 Ophiolites in Southeast Asia Geol Soc Am Bull 86, 797–806 Ishidera, T., Ueno, K., Kurosawa, S., Suyama, T., 2008 Investigation of montmorillonite alteration and formation of iron corrosion products in compacted bentonite in contact with carbon steel for 10 years Phys Chem Earth 33, 269–275 Karnland, O., Olsson, S., Nilsson, U., Sellin, P., 2007 Experimentally determined swelling pressures and geochemical interactions of compacted Wyoming bentonite with highly alkaline solutions Phys Chem Earth 32, 275–286 Kasbohm, J., Tarrah, J., Henning, K.-H., 2002 Transmissionselektronen-mikroskopische Untersuchungen an Feinfraktionen der Ringversuchsprobe “Ton Stoob” In: Ottner, F., Gier, S (Eds.), Beiträge zur Jahrestagung Wien, 18.-20.9.2002 Berichte der Deutschen Ton- und Tonmineralgruppe e.V Band 9, pp 71–84 Kasbohm, J.,Pusch, R.,und Henning, K.-H., 2004 Short term experiments with different bentonites in saline solutions In: Nüesch, R., Emmerich, K (Eds.), Beiträge zur Jahrestagung Karlsruhe Berichte der Deutschen Ton- und Tonmineralgruppe e.V Band 10 175 Kaufhold, S., Dohrmann, R., 2008 Detachment of colloidal particles from bentonites in water Appl Clay Sci 39, 50–59 Kaufhold, S.,Dohrmann, R., 2009 Stability of bentonites in salt solutions: I Sodium chloride Appl Clay Sci 45, 171–177 Kaufhold, S., Dohrmann, R., 2010 Stability of bentonites in salt solutions: II Potassium chloride solution — initial step of illitization? Appl Clay Sci 49, 98–107 Khai, T., Tau, T.K., 2003 Properties and application of bentonite Co Dinh Thanh Hoa and Tam Bo Lam Dong provinces Soil Sci 17, 126–137 (Hanoi, Vietnam, in Vietnamese) Khuc, V (Ed.), 2000 Lexicon of Geological Units of Vietnam Department of Geology and Mineral of Vietnam, Hanoi (in Vietnamese) Kleeberg, R.,Ufer, K.,Bergmann, J., 2005 The quantification of disordered clay minerals by the Rietveld method — some practical aspects Presentation at the 42nd Annual Meeting of the Clay Minerals Society, June 11–15, 2005, Burlington/Vermont Köster, H.M., 1977 Die Berechnung kristallchemischer Strukturformeln von 2:1Schichtsilikaten unter Berücksichtigung der gemessenen Zwischenschichtladungen und Kationenaustausch-kapazitäten, sowie die Darstellung der Ladungsverteilung in der Struktur mittels Dreiecks-koordinaten Clay Miner 12, 45–54 Köster, H.M., Ehrlicher, U., Gilg, H.A., Jordan, R., Murad, E., Onnich, K., 1999 Mineralogical and chemical characteristics of five nontronites and Fe-rich smectites Clay Miner 34, 579–599 Laird, D.A., 2006 Influence of layer charge on swelling of smectites Appl Clay Sci 34, 74–87 Lam, C.V., Tiet, N.D., Hoe, P., 1998 Dry activation of Co Dinh clay J Econ Geol Miner Mater (19), 33–39 (Hanoi, Vietnam, in Vietnamese) Lee, B.D., Sears, S.K., Graham, R.C., Amrhein, C., Vali, H., 2003 Secondary mineral genesis from chlorite and serpentine in an ultramafic soil toposequence Soil Sci Soc Am J 67 (4), 1309–1317 Lerot, L.,Low, F., 1976 Effect of swelling on the infrared absorption spectrum of montmorillonite Clay Clay Miner 24, 191–199 Lien, N.N., 1980 Geology and metamorphism in the Song Ma zone of Vietnam Geol Geofiz 21, 61–71 Madejová, J., Komadel, P., 2001 Baseline studies of the clay minerals society source clays: infrared methods Clay Clay Miner 49, 410–432 Moore, D.E., Reynolds, R.C., 1997 X-Ray Diffraction and the Identification and Analysis of Clay Minerals, second ed Oxford University Press Müller-Vonmoos, M.,Kahr, G.,Bucher, F.,Madsen, F.,Mayor, P.A., 1991 Untersuchungen zum Verhalten von Bentonit in Kontakt mit Magnetit und Eisen unter Endlagerbedingungen Nagra Technical Report NTB 91–14, Nagra, Wettingen, Switzerland Newman, A.C.D., 1987 Chemistry of Clays and Clay Minerals John Wiley & Sons Nguyen-Thanh, L., 2012 Mineralogical Characterization of Fe-driven Alteration in Smectites Dissertation Ernst-Moritz-Arndt-University Greifswald Pearson, F.J.,Arcos, D.,Bath, A.,Boisson, J.Y.,Fernández, A.M.,Gäbler, H.E.,Gaucher, E.,Gautschi, A.,Griffault, L.,Hernán, P.,Waber, H.N., 2003 Mont Terri Project — geochemistry of water in the Opalinus clay formation at the Mont Terri rock laboratory Reports of the Federal Office for Water and Geology (FOWG) Geology Series Petit, S.,Caillaud, J.,Righi, D.,Madejova, J.,Elsass, F.,Köster, H.M., 2002 Characterization and crystal chemistry of an Fe-rich montmorillonite from Olberg Germany Clay Miner 37, 283–297 Pusch, R., 1992 Use of bentonite for isolation of radioactive waste products Clay Miner 27, 353–361 Pusch, R., Kasbohm, J., 2002 Alteration of MX-80 by hydrothermal treatment under high salt content conditions SKB Technical Report TR-02-06 Swedish Nuclear Fuel and Waste Management Co, Stockholm, Sweden Pusch, R., Touret, O., 1988 Heat effects on soft Na bentonite gels Stockholm Geol Fören Stockh Förh 110 (2), 183–190 Pusch, R., Yong, R., 2006 Microstructure of Smectite Clays and Engineering Performance Taylor & Francis, London Pusch, R.,Karnland, O.,Hökmark, H.,Sanden, T.,Börgesson, L., 1991 Final report of the Rock Sealing Project — sealing properties and longevity of smectitic clay grouts Stripa Project Technical Report 91–30, SKB, Stockholm, Sweden Pusch, R., Kasbohm, J., Pacovsky, J., Cechova, Z., 2007 Are all smectite clays suitable as “buffers”? Phys Chem Earth Parts A/B/C 32, 116–122 http://dx.doi.org/10.1016/j pce.2006.03.008 (Clay in natural and engineered barriers for radioactive waste confinement — Part 1) Savage, D.,Watson, C.,Benbow, S., Wilson, J., 2010 Modelling iron–bentonite interactions Appl Clay Sci 47, 91–98 Schnellmann, W., 1964 Zur lateritischen Verwitterung von Serpentnite Geol Jahrb 81, 645–678 (English abstract) Seki, Y., Yurdakoc, K., 2007 Identification and characterization of Fe-rich smectites in the Camlica Region of western Turkey Clay Miner 42, 153–160 Son, P et al., 1975 Report of the geological map of Son La at the scale of 1:200,000 geological map (Hanoi) Department of Geology of Vietnam 46, 4–11 (in Vietnamese) Środoń, J.,Elsass, F.,McHardy, W.J.,Morgan, D.J., 1992 Chemistry of illite–smectite inferred from TEM measurements of fundamental particles Clay Miner 27, 137–158 Stober, I., Bucher, K., 2002 Origin of salinity of deep groundwater in crystalline rocks Terra Nova 11, 181–185 Stubičan, V., Roy, R., 1961 Isomorphous substitution and infra-red spectra of the layer lattice silicates Am Mineral 46, 32–51 Suzuki, S.,Sazarashi, M.,Akimoto, T.,Haginuma, M.,Suzuki, K., 2008 A study of the mineralogical alteration of bentonites in saline water Appl Clay Sci 41, 190–198 Thang, N.D.,Truong, P.D.,Hoa, B.C., 1999 Mineral composition in ophiolite Song Ma Mineral and Geology (Part III) in Proceedings of 40th year of Mapping Geology in Vietnam, pp 117–141 (in Vietnamese) Thanh, D.T.V., Duong, N.T., Nhan, T.T.T., 2005 Characteristic of minerals in peridotite, Nui Nua, Thanh Hoa In Proceedings of the 60th year Geology in Vietnam, pp 201–207 (in Vietnamese) 176 L Nguyen-Thanh et al / Applied Clay Science 101 (2014) 168–176 Thuc, D.D., Trung, H., 1995 Geology of Vietnam, Part II, Magmatic Formations General Department of Geology, Hanoi, (in Vietnamese) Tong-Dzuy, T., Vu, K., 2011 Stratigraphical Units of Vietnam Vietnam National University, Hanoi Tri, T.V., 1979 Geology of Vietnam, the North Part Science and Technology Publishing House, Hanoi, (in Vietnamese) Tri, T.V (Ed.), 2005 Mineral Resources of Vietnam, second ed Dept Geol Min of Vietnam, Hanoi (in Vietnamese) Tri, T.V.,Uy, N.D.,Ngoc, D., 1986 The main tectonics features of Vietnam Proceedings of the 1st Congress of the Geology of Indochina (CIG) 1, pp 361–366 (Hanoi, in Vietnamese) Ufer, K., Roth, G.,Kleeberg, R.,Stanjek, H.,Dohrmann, R.,Bergmann, J., 2004 Description of X-ray powder pattern of turbostratically disordered layer structures with a Rietveld compatible approach Z Kristallogr 219, 519–527 Ufer, K., Kleeberg, R., Bergmann, J., Curtius, H., Dohrmann, R., 2008 Refining real structure parameters of disordered layer structures within the Rietveld method Z Kristallogr (Suppl 27), 151–158 UNP, 1990 Atlas of Mineral Resources of the Escape Region Vol United Nations Publication, Vietnam 92-1-119559-4 Van der Marel, H.W.,Beutelspacher, H., 1976 Atlas of Infrared Spectroscopy of Clay Minerals and Their Admixtures Elsevier, Amsterdam Vantelon, D.,Pelletier, M.,Michot, L.J.,Barres, O.,Thomas, F., 2001 Fe Mg and Al distribution in the octahedral sheet of montmorillonites An infrared study in the OH-bending region Clay Miner 36, 369–379 Vuong, N.V.,Chuong, M.H.,Thang, T.T., 2006 Isotope age and thermal tectonic evolution of ophiolite rocks in Song Ma satural zone J Geosci 28, 165–173 (in Vietnamese) Weiss, A., Koch, G., 1961 Über einen Zusammenhang zwischen dem Verlust des innerkristallinen Quellungsvermögens beim Erhitzen und dem Schichtaufbau bei glimmerartigen Schichtsilikaten Z Naturforsch 16b, 68–69 Wildman, W.E., Jackson, M.L., Whittig, L.D., 1968 Iron-rich montmorillonite formation in soils derived from serpentinite Soil Sci Soc Am Proc 32, 787–794 Wildman, W.E.,Jackson, M.L.,Whittig, L.D., 1971 Serpentine stability in relation to formation of iron-rich montmorillonite in some California soils Am Mineral 56, 587–602 Wilson, J.,Cressey, G.,Cressey, B.,Cuadros, J.,Ragnarsdottir, K.V.,Savage, D.,Shibata, M., 2006a The effect of iron on montmorillonite stability (II) Experimental investigations Geochim Cosmochim Acta 70 (2), 323–336 Wilson, J., Savage, D., Cuadros, J., Shibata, M., Ragnarsdottir, K.V., 2006b The effect of iron on montmorillonite stability (I) Background and thermodynamic considerations Geochim Cosmochim Acta 70 (2), 306–322 Zysset, M., Schindler, P.W., 1996 The proton promoted dissolution kinetics of Kmontmorillonite Geochim Cosmochim Acta 60, 921–931 ... Experiments and methods 3.1 Kinetic experiments The kinetics of Fe- and Mg-driven alteration processes of the Nui Nua clay as well as the potential of alteration of Fe-smectite were investigated The. .. (including clays from the Co Dinh and My Cai valleys) formed as the weathering products of the serpentinized ultramafic–mafic Nui Nua massif (Thanh Hoa Province, Vietnam) was characterized by the dominant... depends on the flow rate of overhead rotating or the energy of the hydraulic regime; the lower the flow rate, the larger the amount of dissolved Si resulting in neoformed montmorillonite The alteration