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DIVISION S-9—SOIL MINERALOGY

Secondary Mineral Genesis from Chlorite and Serpentine in an Ultramafic Soil Toposequence

^a Dep. of Agronomy, Purdue Univ., Lilly Hall of Life Sciences, West Lafayette, IN 47907-2054
^b Electron Microscopy Centre, McGill Univ., 3640 University Street, Montréal, QC Canada H3A 2B2
^c Soil and Water Sciences Program, Dep. of Environ. Sci., Univ. of California, Riverside, CA 92521-0424

^* Corresponding author (bdlee{at}purdue.edu)

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
The origin of secondary phyllosilicates in serpentinitic soils of differing moisture regimes is incompletely understood. The objective of this study was to determine the genesis of weathering products in serpentinitic soils along a moisture regime gradient using conventional x-ray diffraction (XRD) methods and high-resolution transmission electron microscopy (HRTEM). The samples studied were obtained from an Aquic Argixeroll and a Cumulic Endoaquoll on the Trinity ophiolite, in the Klamath Mountains, California. The soils are from backslope and toeslope landscape positions associated with a 3.2-ha wetland on a stabilized landslide bench. Chlorite and serpentine are the major primary minerals in the soils. Chlorite is relatively stable and was found in the clay fraction of all horizons studied. Serpentine was observed in all horizons except the Aquic Argixeroll Cr2 horizon. The soil mineral assemblages indicate that chlorite transforms to vermiculite and both randomly and regularly interstratified chlorite/vermiculite by loss of the hydroxide-interlayer sheet. The vermiculite then alters to a high-charge smectite that was found only in the lower horizons of the backslope landscape position. Smectite is the predominant secondary mineral in all horizons. Serpentine transformation products could not be directly identified, but the prevalence of a low-charge smectite in the Cumulic Endoaquoll is interpreted as a precipitate from serpentine dissolution products. Thus, the abundant smectite in these serpentinitic soils is of two origins: (i) a high-charge phase derived from chlorite transformation that is found in the backslope landscape positions, and (ii) a low-charge phase neoformed by precipitation of elements released by serpentine weathering.

Abbreviations: TEM, transmission electron microscopy • HRTEM, high-resolution transmission electron microscopy • n_C, number of C atoms in the alkylammonium chain • ICP-OES, inductively coupled argon plasma optical emission spectroscopy • CEC, cation-exchange capacity • XRD, x-ray diffraction • EDS, energy dispersive x-ray spectrometry

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
THE MINERALOGY of soils formed from serpentinite is strongly controlled by the geochemistry and mineralogy of the parent rock. Phyllosilicates within the clay fraction typically include serpentine, accepted as lithogenic (Graham et al., 1990), and chlorite, which can be lithogenic, but also has been hypothesized to form by extensive hydroxy-interlayering of smectite (Rabenhorst et al., 1982). Smectite, often the most abundant constituent of the <2-µm fraction in serpentinitic soils, has been identified as a weathering product of serpentine (Wildman et al., 1968; Rabenhorst et al., 1982; Graham et al., 1990).

Pedogenic formation of smectite has been linked to topographic position by some researchers. Weathering products of serpentine may be almost entirely removed from highly leached soils on well-drained landscape positions, but they may accumulate and contribute to the synthesis of smectite in poorly drained soils. For example, Istok and Harward (1982) found smectite, chlorite, and serpentine within poorly drained soils, but found only serpentine and chlorite in well-drained upland soils.

The species of smectite formed has also been interpreted to be dependent on drainage conditions. Nontronite and a magnesium silicate gel were formed in the fractures of a weathered serpentinite in France (Fontanaud and Meunier, 1983). Nontronite forms within well-drained landscape positions (Wildman et al., 1968), while saponite forms within poorly drained landscape positions (Senkayi, 1977). This partitioning of smectite species was attributed to the relative immobility of Fe and Al, hence concentration of these elements in well-drained landscape positions. Magnesium and Si are more readily leached from the well-drained upland soils and therefore tend to accumulate in poorly drained landscape positions. Bonafacio et al. (1997) proposed that serpentine weathers to low-charge vermiculite within well-drained landscape positions, and to smectite within poorly drained landscape positions. These researchers further suggested that vermiculite could be translocated within the profile to a poorly drained horizon, where it transforms into smectite. The pathways of smectite and vermiculite genesis in serpentinitic soils proposed by these researchers vary widely; therefore there is a need to further investigate the genesis of secondary minerals in serpentinitic terrain.

X-ray diffraction analysis of clay minerals treated with alkylammonium cations can be used to determine the layer charge of expandable 2:1 clay minerals (Lagaly, 1981). Furthermore, n-alkylammonium cations can be used to stabilize the interlayers of expandable 2:1 clay minerals that otherwise collapse under the electron beam and high vacuum of the transmission electron microscope (TEM). Treatment of 2:1 clay minerals with n-alkylammonium cations has been used in XRD analysis to qualitatively differentiate between a high-charge smectite altering from mica and a low-charge smectite forming from volcanic materials (Senkayi et al., 1985). The advantages of HRTEM over XRD include distinguishing between short-range ordered structures and the ability to characterize all types of particles present, not just coherent sequences, as given by XRD.

Previous researchers have used conventional XRD and chemical dissolution methods to investigate weathering products found in serpentinitic soils (Wildman et al., 1968; Rabenhorst et al., 1982; Graham et al., 1990; Bulmer et al., 1992; Bulmer and Lavkulich, 1994; and Bonafacio et al., 1997). In this study, we combine conventional XRD and chemical methods with XRD and HRTEM analysis of samples treated with n-alkylammonium cations to better illustrate the nature of the secondary minerals found in serpentinitic soils, and thereby, further our understanding of their genesis.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Environmental Setting
The study site is in the Scott Mountains within the Klamath Mountain physiographic province of northern California. The climate is Mediterranean with an average of 1000 mm annual precipitation (Rantz, 1968), falling as rain or snow predominantly (>90%) between October and May (Foster and Lang, 1994). The geology of the area includes cumulate lherzolite peridotite interlayered with minor harzburgite, dunite and pyroxinite with minor inclusions of Cretaceous hornblende diorite porphyry (Lindsey-Griffin, 1982). Landslides are common throughout the terrain.

A stabilized landslide bench and scarps of a rotational slump was selected for intensive examination. Water ponded behind the bulge of the landslide bench supports a wetland meadow. The vegetation on the backslopes surrounding the wetland includes Jeffrey pine (Pinus jeffreyi Grev. and Balf.), incense cedar (Calocedrus decurrens (Torr.) Florin), buckbrush (Ceanothus cuneatus (Hook) Nutt.), and California fescue (Festuca californica Vasey). Vegetation in the wetland meadow is predominantly grasses (Poa pratensis L., Danthonia californica Bol., Glyceria elata (Nash) Hitchc.), rushes (Juncus parryi Englm., Juncus bufonius L.), sedges (Carex sp., Scirpus microcarpus Presl.), and forbs (Trifolium sp., Dodecatheon sp.). A more detailed description of the study site location can be found in Lee et al. (2001).

Field Methods
Two pedons of differing drainage were described and sampled according to conventional procedures (Soil Survey Division Staff, 1993). A clayey-skeletal, magnesic, mesic Aquic Argixeroll was sampled on a south-facing backslope (28% gradient). Fifty meters downslope from the Aquic Argixeroll, a fine, magnesic, mesic Cumulic Endoaquoll was sampled on the toeslope (8% gradient). Morphologic descriptions of the pedons are in Lee (1999) (Pedons 1 and 4). Soil water was collected seasonally from porous cup suction-lysimeters installed across a transect from the backslope to the toeslope landscape positions. Detailed descriptions of the sample locations and procedures are described by Lee et al. (2001) (lysimeters a, b, c, d, e).

Laboratory Methods
Soil samples were air-dried and the <2-mm fraction was separated by sieving (Soil Survey Staff, 1996). Particle-size distribution was determined by sieving and pipette (Gee and Bauder, 1986). Soil pH was determined using 1:1 soil/water mixtures. Cation-exchange capacity (CEC) was determined by saturating exchange sites with Na utilizing 1 M sodium acetate adjusted to pH 7.0, and subsequently rinsing Na from exchange sites with 1 M ammonium acetate (Bower and Hatcher, 1966). Sodium concentrations in ammonium acetate extracts were analyzed by atomic absorption spectrophotometry. The concentrations of Mg and Si in the soil water from the lysimeters were determined by inductively coupled argon plasma optical emission spectroscopy (ICP-OES).

The fine clay (<0.2 µm) and coarse clay (0.2–2 µm) fractions of selected horizons were separated by centrifugation and the medium silt (5–20 µm) was separated by sedimentation, following treatment with Na-hypochlorite to remove organic matter (Jackson, 1975). The <2-µm fraction was subjected to several treatments before analysis by XRD. The treatments included K saturation and heating at 25, 350, and 550°C (K25, K350, K550), and Mg saturation (Mg25), Mg saturation and solvation with glycerol (Gly) or Mg saturation with ethylene glycol (EG). The samples were prepared for XRD analysis using the paste method (Theisen and Harward, 1962; Jackson, 1975). Similarly treated slurry mounts of the medium silt fraction were also analyzed by XRD. Analyses were performed on an x-ray diffractometer with a graphite crystal monochromator using CuK radiation (40 kV and 30 mA). Samples were scanned from 2 to 32° 2 with a step size of 0.02° 2 and a count time of 2.0 s per step. In addition, Na-saturated freeze-dried samples were side-packed as powder mounts and scanned from 54 to 68° 2 with a step size of 0.01° 2 and count time of 10.0 s per step.

Approximately 50 mg of Na-saturated freeze-dried clay intended for XRD analysis was treated with a 0.05 M solution of octadecylamine hydrochloride (n_C = 18) for 5 d at 65°C (Sears et al., 1998). During this period, the solution was replaced three times. At the end of the exchange process, the samples were washed twice by centrifugation with a solution of distilled H₂O and 95% ethanol (1:1) followed by 12 washes in 95% ethanol to remove excess alkylammonium salts and alkylamines (Lagaly 1994). Analysis by XRD was performed on a 12-kW rotating anode automated diffractometer (Rigaku D/Max 2400, Rigaku International Corp., Tokyo, Japan) equipped with a graphite diffracted-beam monochromator (CuK radiation) and a theta-compensating slit assembly using the following analytical conditions: operating voltage of 40kV and a beam current of 160 mA, step-size of 0.04° 2, counting time of 1.0 s per step, a 0.15-mm receiving slit, and a scanning range of 2 to 32° 2. Approximately 30 mg of Na-saturated freeze-dried clay was embedded in low-viscosity TAAB Transmit resin following a procedure modified from Lee et al. (1975). Ultrathin sections were cut from the resin blocks using a Reichert-Jung Ultracut E(C. Reichert AG., Vienna, Austria) equipped with a Diatome diamond knife. Selected sections were transferred to standard Cu TEM grids having formvar and carbon-support films. The mounted sections were treated directly with a dilute solution of n_C = 18 for 20 min at 65°C (Vali and Hesse, 1990; Sears et al., 1998). The ultrathin sections were imaged in bright-field illumination at high-resolution with a JEOL JEM-2000FX TEM (JEOL Limited, Tokyo, Japan) equipped with a PGT Prism energy-dispersive x-ray spectrometer (EDS) (Princeton Gamma-Tech, Inc., Princeton, NJ) at an accelerating voltage of 80 kV. Magnification ranged between 20000 and 100000 times.

Mineralogical interpretations from lattice-fringe images and XRD patterns were based on the reference d-values listed in Table 1.

	RESULTS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

View this table: [in this window] [in a new window]   Table 2. Soil physical, chemical, and mineralogical properties of selected horizons.

Clay Fraction
The A horizon contains serpentine, chlorite, talc, amphibole, interstratified chlorite/vermiculite, and a low-charge smectite-group mineral. The Bt2 horizon contains the same minerals as the A horizon, but the smectite has a more intense peak (Fig. 1). Smectite is the most abundant mineral in the clay fraction of the BC horizon, with minor amounts of talc, serpentine, chlorite, and interstratified chlorite/vermiculite. The Cr2 horizon contains smectite, vermiculite, chlorite, and interstratified chlorite/vermiculite (Table 2).

View larger version (29K): [in this window] [in a new window]   Fig. 1. X-ray diffraction patterns of the clay fraction (<2 µm) from selected horizons of the Aquic Argixeroll.

View larger version (25K): [in this window] [in a new window]   Fig. 2. Clay fraction (<2 µm) x-ray diffraction patterns of the d(060)-values.

View larger version (20K): [in this window] [in a new window]   Fig. 3. X-ray diffraction patterns of the d(060)-values of the fine (<0.2 µm) and coarse clay (0.2–2 µm) fractions from the Cr2 horizon of the Aquic Argixeroll.

View larger version (106K): [in this window] [in a new window]   Fig. 4. Lattice-fringe images from Aquic Argixeroll. (a) A horizon, <2-µm fraction: chlorite expanded to vermiculite with 3.4 nm d-value indicated, (b) BC horizon, <2-µm fraction: high-charge smectite (S) with 2.5 nm d-value indicated, (c) Cr2 horizon, 0.2- to 2-µm fraction, vermiculite (V) and randomly interstratified chlorite/vermiculite (C/V), (d) Cr2 horizon, <0.2-µm fraction: domains of chlorite (C) with 1.4-nm value indicated, vermiculite (V) with 3.4-nm value, and book of chlorite altered to interstratified chlorite/vermiculite (C/V) at its edge, (e) BC horizon, <2-µm fraction: discontinuous and disordered laths representing smectite (S), and vermiculite (V) weathering from a chlorite mineral.

Clay Fraction
The clay mineralogy of the Cumulic Endoaquoll is similar throughout all horizons (Fig. 5, Table 2). On the basis of relative peak height, low-charge smectite is the most abundant clay mineral, with lesser amounts of serpentine, chlorite, and talc.

View larger version (31K): [in this window] [in a new window]   Fig. 5. X-ray diffraction patterns of the clay fraction (<2 µm) from selected horizons of the Cumulic Endoaquoll.

Relative peak heights of the EDS spectra (Table 3) indicate that the serpentine contains almost no Al relative to Si and Mg, while smectite EDS relative peak height ratios suggest Si is much more abundant than Al and Mg. The smectite EDS relative peak height ratio for Al/Mg is 0.9, suggesting near equal abundance of these elements. There is little difference between the EDS spectra of chlorite and vermiculite.

Soil Solution Chemistry
Average concentrations of Mg and Si in the soil solutions collected from lysimeters are listed in Table 4. Magnesium concentrations ranged from 2.8 to 4.8 mmol L^-1 while Si content ranged from to >1.2 to 1.4 mmol L^-1.

View this table: [in this window] [in a new window]   Table 4. Average concentration of Mg and Si in soil water.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

Aquic Argixeroll
Vermiculite most likely formed as a weathering product of chlorite through an intermediate interstratified chlorite/vermiculite mineral. Short packets of chlorite surrounded by vermiculite, together constituting a randomly interstratified chlorite/vermiculite, were identified for the clay fraction of all horizons studied by HRTEM (e.g., Fig. 4a). Regularly interstratified vermiculite was identified in the fine clay (<0.2 µm) fraction of the Cr2 horizon, evident from the frayed edges of the chlorite minerals (Fig. 4d). The removal of all or portions of the interlayer hydroxide sheet within chlorite is a common weathering process that depends on the quantity of interlayer Fe²⁺, the oxidation of Fe²⁺ to Fe³⁺, and the subsequent removal of Fe and Mg from the interlayer OH sheets (Barnhisel and Bertsch, 1989).

A comparison of d(060)-values indicates that the trioctahedral minerals are more abundant and/or crystalline in the coarse clay (0.2–2 µm) than the fine clay (<0.2 µm) of the Cr2 horizon (Fig. 3). Because the Cr2 horizon clay fraction does not contain serpentine (Table 2), the 0.1538-nm 060 diffraction peak is probably from chlorite. The decrease in the 0.1538-nm relative peak height in the fine clay relative to the coarse clay diffraction patterns suggests that chlorite is more stable in the coarse clay fraction.

Smectite was identified in the medium silt fraction as well as in the clay fraction (Table 2). Because neoformed smectite is typically concentrated within the clay fraction, it is likely that much of the smectite in the upper landscape positions is formed, not from the dissolution products of serpentine weathering, but rather the solid-state transformation of chlorite, possibly through an intermediate vermiculite phase. The chlorite or intermediate vermiculite then weathered to a well-ordered, high-charge smectite, as evident by the decrease in the d(001)-value to 2.5 after intercalation with octadecylammonium cations (Fig. 4b). These results agree with Bonafacio et al. (1997), who concluded for moist serpentinitic soils, vermiculite weathers to smectite. The loss of charge and collapse of the vermiculite interlayer may be the result of Fe²⁺ oxidation. The high CEC in the BC and Cr2 horizons relative to that of the solum (Table 2) may be attributed to the high-charge smectite, as well as the abundance of smectite in the silt fraction.

Cumulic Endoaquoll
Smectite is the most abundant mineral in the clay fraction, but is only a minor component of the medium silt fraction (Table 2). The smectite is not well ordered, evident by the incomplete collapse to 1.01 nm when K saturated and heated to 550°C (Fig. 5). The presence of smectite within the clay fraction of lower landscape position soils is consistent with the results of Istok and Harward (1982), who suggested that the dissolution products of serpentine concentrate in lower landscape positions creating conditions favorable for smectite formation. There is a dioctahedral component within the clay fraction (Fig. 2), indicating that the smectite is not saponite. These results are contrary to Wildman et al. (1968) and Senkayi (1977) who reported the precipitation of saponite for lower landscape positions in serpentinitic soils. In this system, the trivalent cation in the octahedral sheet is probably Al. While Al is not a major component in serpentinites (O'Hanley, 1996), Al was found in both serpentine and chlorite (Table 3).

Silicic acid and Mg²⁺ are the major dissolution products of serpentine, and Si and Mg were identified in the soil solutions (Table 4), as is typical of serpentinitic terrain soil solutions (Cleaves et al., 1974; Kram et al., 1997). While other Mg-rich minerals such as talc, amphibole, and chlorite are present, serpentine is likely the largest contributor of soluble Si and Mg within these soils because it is the most abundant mineral and it is easily weathered. The molar ratio of Mg/Si within the soil solutions ranges from 2.3 to 3.3, higher than the Mg/Si ratio of 1.5 for serpentine (O'Hanley, 1996), suggesting that Si is being removed from solution, or is not entering solution as fast as Mg.

Cleaves et al. (1974) attributed a high concentration of Mg relative to Si in stream waters draining a serpentinitic watershed to neoformation of Mg-montmorillonite in the soils. Smectite formation is favored in Si- and Mg-rich, poorly drained soils (Borchardt, 1989), such as those found in this serpentinitic landscape. In this study, while there is no direct evidence, the high Mg/Si ratios in the soil solution and the low Mg/Si ratios of smectite relative to other minerals in the soil (Table 3) support neoformation of smectite in the poorly drained Klamath soils. This interpretation is further supported by a stability diagram plotted with soil solution concentrations, which shows that Mg-rich montmorillonite is stable in these soils (Fig. 6).

View larger version (28K): [in this window] [in a new window]   Fig. 6. Stability relations of clay phases in the system MgO-Al2O3–SiO2–H2O at 25°C and 0.1 MPa, and the matrix solution activity functions, pH– 1/2pMg2+ and pSi(OH)4 (modified from Helgeson et al., 1969). Cross-hatched area represents soil waters collected from lysimeters. Samples used in plot came from soils with pH values ranging from 6.3 to 7.8 (soil water pH not determined).

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

Chlorite in the clay fraction is trioctahedral and lithogenic. The chlorite transforms to trioctahedral vermiculite through an interstratified chlorite/vermiculite phase. This transformation process involves total or partial removal of the hydroxide interlayer sheet. The vermiculite transforms to a high-charge smectite, presumably through a loss of charge in the octahedral sheet as Fe²⁺ is oxidized. The high-charge smectite appears to be formed only in the lower horizons of the upper landscape position, possibly because it is most stable in this environment or because the abundance of low-charge smectite made it difficult to identify in the lower landscape positions.

The following reactions are proposed for serpentine and chlorite in these serpentinitic soils:

1. serpentine low-charge Mg-rich, dioctahedral smectite
   
2. chlorite interstratified chlorite/vermiculite vermiculite high-charge smectite
   

	ACKNOWLEDGMENTS

 
This research was supported by grants from the Clay Minerals Society and the Natural Sciences and Engineering Research Council (NSERC) of Canada (H.V.). The authors would like to thank three anonymous reviewers for their constructive comments on previous versions of this manuscript. The assistance of Tom Laurent, Klamath National Forest is gratefully acknowledged.

Received for publication December 4, 2001.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 

• Bailey, S.W. 1980. Structures of layer silicates. p. 1–123. In Brindley, G.W. and G. Brown (ed.) Crystal structures of clay minerals and their x-ray identification. Monogr. 5. Mineralogical Society, London, UK.
• Barnhisel, R.I., and P.M. Bertsch. 1989. Chlorites and hydroxy-interlayered vermiculite and smectite. p. 729–788. In J.B. Dixon and S.B. Weed (ed.) Minerals in soil environments. 2nd ed. SSSA Book Ser. 1. SSSA, Madison, WI.
• Bonafacio, E., E. Zanini, V. Boero, and M. Franchini-Angela. 1997. Pedogenesis in a soil catena on serpentinite in northwestern Italy. Geoderma 75:33–51.
• Borchardt, G. 1989. Smectites. p. 675–728. In J.B. Dixon and S.B. Weed (ed.) Minerals in soil environments. 2nd ed. SSSA Book Ser. 1. SSSA, Madison, WI.
• Bower, C.A., and J.T. Hatcher. 1966. Simultaneous determination of surface area and cation-exchange capacity. Soil Sci. Soc. Am. Proc. 30:525–527.
• Brindley, G.W. 1980. Order-disorder in clay mineral structures. p. 125–195. In G.W. Brindley and G. Brown (ed.) Crystal structures of clay minerals and their x-ray identification. Monograph 5. Mineralogical Society, London, UK.
• Bulmer, C.E., and L.M. Lavkulich. 1994. Pedogenic and geochemical processes of ultramafic soils along a climatic gradient in southwestern British Columbia. Can. J. Soil Sci. 74:165–177.
• Bulmer, C.E., L.M. Lavkulich, and H.E. Schreier. 1992. Morphology, chemistry, and mineralogy of soils derived from serpentinite and tephra in southwestern British Columbia. Soil Sci. 154:72–82.
• Cleaves, E.T., D.W. Fisher, and O.P. Bricker. 1974. Chemical weathering of serpentinite in the eastern piedmont of Maryland. Geol. Soc. Am. Bull. 85:437–444.[Abstract]
• Fontanaud, A., and A. Meunier. 1983. Mineralogical facies of a weathered serpentinized lherzolite from the Pyrènèes, France. Clay Miner. 18:77–88.[Abstract]
• Foster, C.M., and G.K. Lang. 1994. Soil survey of Klamath National Forest area, California, parts of Siskiyou County, California and Jackson County, Oregon. U.S. Gov. Print. Office, Washington, DC.
• Gee, G.W., and J.W. Bauder. 1986. Particle-size analysis. p. 377–381. In A. Klute (ed.) Methods of soil analysis. Part 1. 2nd ed. Agron. Monagr. 9. ASA and SSSA, Madison, WI.
• Graham, R.C., M.M. Diallo, and L.J. Lund. 1990. Soils and mineral weathering on phyllite colluvium and serpentinite in northwestern California. Soil Sci. Soc. Am. J. 54:1682–1690.[Abstract/Free Full Text]
• Helgeson, H.G., T.H. Brown, and R.H. Leeper. 1969. Handbook of theoretical activity diagrams depicting chemical equilibria in geologic systems involving an aqueous phase at 1 atm. and 0 to 300° C. Freeman Cooper & Co., San Franscisco, CA.
• Istok, J.D., and M.E. Harward. 1982. Influence of soil moisture on smectite formation in soils derived from serpentinite. Soil Sci. Soc. Am. J. 46:1106–1108.[Abstract/Free Full Text]
• Jackson, M.L. 1975. Soil chemical analysis—Advanced course. M.L. Jackson, Madison, WI.
• Kram, P., J. Hruska, B.S. Wenner, C.T. Driscoll, and C.E. Johnson. 1997. The biogeochemistry of basic cations in two forest catchments with contrasting lithology in the Czech Republic. Biogeochemistry 37:173–202.
• Lagaly, G. 1981. Characterization of clays by organic compounds. Clay Miner. 16:1–21.[Abstract]
• Lagaly, G. 1994. Layer charge determination by alkylammonium ions. p. 1–14. In A.R. Mermut (ed.) Layer charge characteristics of 2:1 silicate clay minerals. The Clay Minerals Society, Boulder, CO.
• Lee, S.Y., M.L. Jackson, and J.L. Brown. 1975. Micaceous occlusions in kaolinite observed by ultramicrotomy and high-resolution electron microscopy. Clays Clay Miner. 23:125–129.[Abstract]
• Lee, B.D. 1999. Pedogenesis and mineral weathering in serpentinitic landslide terrain, Klamath Mountains, California. Ph.D. diss. University of California, Riverside, CA.
• Lee, B.D., R.C. Graham, T.E. Laurent, C. Amrhein, and R.M. Creasy. 2001. Spatial distributions of soil chemical conditions in a serpentinitic wetland and surrounding landscape. Soil Sci. Soc. Am. J. 65:1183–1196.[Abstract/Free Full Text]
• Lindsey-Griffin, N. 1982. Structure, stratigraphy, petrology, and regional relationships of the Trinity ophiolite. Doctoral Thesis. University of California, Davis, CA.
• O'Hanley, D.S. 1996. Serpentinites: Records of tectonic and petrological history. Oxford monographs on geology and geophysics No. 34. Oxford Univ. Press, New York.
• Rabenhorst, M.C., J.E. Foss, and D.S. Fanning. 1982. Genesis of Maryland soils formed from serpentine. Soil Sci. Soc. Am. J. 46:607–616.[Abstract/Free Full Text]
• Rantz, S.E. 1968. Average annual precipitation and runoff in north coastal California. Hydrologic investigations atlas HA-298. U.S. Geol. Surv., Washington, DC.
• Sears, S.K., R. Hesse, and H. Vali. 1998. Significance of n-alkylammonium exchange in the study of 2:1 clay-mineral diagenesis, Mackenzie Delta—Beaufort Sea region. Arctic Canada. Can. Miner. 36:1475–1484.
• Senkayi, A.L. 1977. Clay mineralogy of poorly drained soils developed from serpentinite rocks. Ph.D. diss. Univ. of California, Davis, CA.
• Senkayi, A.L., J.B. Dixon, L.R. Hossner, and L.A. Kippenberger. 1985. Layer charge evaluation of expandable soil clays by an alkylammonium method. Soil Sci. Soc. Am. J. 49:1054–1060.[Abstract/Free Full Text]
• Soil Survey Division Staff. 1993. Soil survey manual. USDA handb. 18. U.S. Gov. Print. Office, Washington, DC.
• Soil Survey Staff. 1996. Soil survey laboratory methods manual: Soil survey investigations. Rep. No. 42. Ver. 3.0. USDA, Washington, DC.
• Theisen, A.A., and M.E. Harward. 1962. A paste method for preparation of slides for clay mineral identification by x-ray diffraction. Soil Sci. Soc. Am. Proc. 26:90–91.
• Vali, H., and R. Hesse. 1990. Alkylammonium ion treatment of clay minerals in ultrathin section: A new method for HRTEM examination of expandable layers. Am. Mineral. 75:1443–1446.[Abstract]
• Vali, H., and R. Hesse. 1992. Identification of vermiculite by transmission electron microscopy and x-ray diffraction. Clay Miner. 27:185–192.[Abstract]
• Wildman, W.E., M.L. Jackson, and L.D. Whittig. 1968. Iron-rich montmorillonite formation in soils derived from serpentinite. Soil Sci. Soc. Am. Proc. 32:787–794.

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