Pertanika 13(1), 85-93 (1990)

A Study of the Ferrallitic Weathering of an Amphibole Schist inPeninsular Malaysia

S. ZAUYAH* and G. STOOPS*** Department of Soil Science,

Faculty of Agriculture,Umversiti rertaman Malaysia,

43400 UPM, Serdang, Selangor Darul Ehsan, Malaysia.* * Geologisch Institut, Krijgslaan 281, 9000 Gent, Bebium

ABSTRAKPertukaran mikromorfologi dan mineralogi yang disebabkan oleh luluhawa di dalam satu profil skis amfibol diSemenanjung Malaysia telah dikaji. Sungguhpun batuan hamparan yang keras tidak dijumpai, banyak batu-terasbatuan asal didapati terdedah. Pemerhatian dengan mikroskop elektron pengimbas dan keratan nipis menunjukkanbahawa aktinolit mengalami luluhawa lebih cepat daripada epidot. Kedua-dua mineral ini mengalamiperlarutan kongruendan diganti oleh kaolinit baru yang berbentuk vermi dan haloisit pada bahagian bawah saprolit. Data ini disokongdengan kajian difraktometer sinar-X. Analisis kimia bagi lingkungan luluhawa menunjuk bahawa dalam peringkatpertama luluhawa feralitik, mengikut cara isovolumetrik, unsur-unsur alkali dan bumi beralkali terhilang bersamaandengan sebahagian besar silikon, tetapi aluminium didapati malar. Ferum didapati berkumpul semasa peringkat per-tama luluhawa. Permukaan luluhawa bagi profil skis amfibol ini didapati tajam dan proses pedoplasma berlaku mengikutstruktur-struktur geologi dengan menghasil bahan tanah yang kaya lempung.

ABSTRACTMicromorphological and mineralogical changes resulting from the weathering of an amphibole schist in Peninsular Malaysiahave been studied. Although the hard bedrock mass is not reached, many large corestones of unweathered rock materialare exposed. Thin sections and SEM observations show that the actinolite weathers faster than epidote. Both undergocongruent dissolution and are replaced by new formed vermiform kaolinite and halloysite in the lower saprolite, butby kaolinite and gibbsite in the upper saprolite. This data is corroborated by XRD studies. Chemical analyses of theweathering rims, expressed according to the isovolumetric method, show that they are already in the first stage offerrallitic weathering with the alkaline and alkaline earth elements lost, as is a large part of the silicon, thoughaluminium remains practically constant. Iron accumulates during the first stage of weathering. The weathering front isabrupt, and pedoplasmation follows geological structures, forming a clay-rich soil material.

INTRODUCTION amphibole schist profile under humid tropical,

In Peninsular Malaysia, observations of weather- well drained conditions were investigated,

ing profiles were first cited in the Malayan M A T £ R I A L S A N D M E T H O D S

Geological Survey Memoirs (Roe 1951). Later,soil scientists made several detailed studies on the Location and Geological Settingchemical, mineralogical and micromorphological An amphibol schist profile exposed along thechanges related to the transformation of hard rock Karak-Kuantan Highway at 54 km was sampledmaterial to soil (Yeow 1975; Eswaran and in detail (Zauyah 1986).Wong, 1977). Most of these studies dealt with The amphibole schist outcrops as a lenticular-relatively coarse grained, rather homogeneous shaped body (1 km long) and forms one ofrock material (e.g. granites, gneisses), and little many similar bodies occurring commonly withinattention was given to the heterogeneous meta- a sequence of low-grade regionally metamor-morphic rocks, although they form quite an phosed schists of the Bentong Group (Lowerimportant soil parent material. Palaeozoic). These schists outcrop on the eastern

In this study, the micromorphological and slopes of the Main Range of Peninsular Malaysiamineralogical changes due to weathering of an near the town of Bentong and have given rise

S. ZAUYAH AND G. STOOPS

to a dissected, hilly to undulating terrain. Theamphibole schists occurring in this area havebeen postulated by Richardson (1947) to havedeveloped through the metamorphism of cal-careous sediments.

The climate of this region is equatorial witha mean annual rainfall of 234 cm distributedthroughout the year with a maxima betweenOctober and January and between March andMay. The mean annual temperature is 26°C.

The profile sampled is located on a gentlysloping part of a hill, 130 m above sea level, ina dissected hilly terrain.

A schematic sketch of the weathering profileis shown in Fig. 1 and the profile description inTable 1. The weathering sequence of this rockwas studied starting from the alteration zonesurrounding a corestone as the bedrock mass isnot exposed. Fresh rock samples (R) werecollected from most of the corestones occurring inthe lower, as well as the upper saprolite. Theother samples were collected from the weatheringrims and in between the corestones (Cr). Inaddition, soil material was sampled along jointplanes (R(s) as well as in the overlying soil,

a clayey, kaolinitic, isohyperthermic TypicHapludox.

Laboratory AnalysesThin sections in all rock samples were prepared.For the weathered or soft saprolite, the sampleshad to be impregnated with polyester resin(Eterset 2660P) prior to the preparation of thinsections of 12 cm x 9 cm and 9 cm x 6 cm size.Weathering features were described according toStoops etat. (1979) and Bullock et ai (1985). Freshfracture surfaces of all the samples were examin-ed with a Jeol 35C scanning electron microscope.

Total analysis of the major elements wascarried out by X-ray fluorescence according toHutchison (1974). Active and free iron weredetermined according to Schwertmann (1964),and Mehra and Jackson (1960), respectively.Free iron was removed from uncovered thinsections as proposed by Bullock et al. (1975).

The bulk mineralogy of all the fresh rockand weathered samples and the sand, silt and clayfractions of the soil samples were analysed by X-ray diffraction. The crystallinity of kaolinite wasdetermined on non-oriented powder mounts of

CM (2) (+RJ> >"Crl(3)

lower^saprolite

Xcorestones

86

Fig. 1. Schematic sketch of weathering profile over the amphibole schist showing the sampling points.

FERTANIKA VOL. 13 NO. 1, 1990

STUDY OF THK FKRRALLITIC WEATHKRINt; OF AN AMPHIBOLE SCHIST

d it h ion ite- citrate -bicarbonate -treated claysamples, after Hinckley (1963).

RESULTS AND DISCUSSION

Macroscopic DescriptionThe fresh rock material from the corestones is finegrained, very hard and shows a compositionalbanding (10 to 15 mm) of dark gray (7.5YR 3/10)to gray (7.5YR 6/0) and olive gray (5Y 6/2).

The first 10 cm of the weathering rim showsmany shades of colours. The predominant coloursare pale yellow (2.5YR 8/4) to yellow (10YR 7/8)with black streaks (10YR 2/1). The weatheredrock material is quite coherent closest to the corebut becomes friable towards the outside. At about20 to 30 cm from the hard rock, the coloursbecome more uniformly reddish yellow (7.5YR6/8). The weathered material also becomes softand breaks easily between the fingers, though therock fabric is still preserved.

The samples collected between the corestonesbelong to the lower and upper saprolite. General-ly, the samples in the lower saprolite are reddishyellow (10YR 6/8), while the samples from theupper saprolite are yellowish red (5YR 4/6).These samples may break easily between thefingers but the rock fabric is still evident.

The soil samples along joints in the uppersaprolite are yellow red (5YR 4/6) to red (2.5YR4/6) and have yellow mottles (10YR 8/8). Theygenerally have an angular, blocky to crumbstructure and silty clay texture.

The soil is yellowish red (5YR 5/8 andhas a weak, medium to fine subangular blockystructure and a clayey texture. In the upperAl horizon, the structure tends to be granular.

Microscopic Observation

Petrology of the Fresh Rock MaterialThe amphibole schist is composed of alterna-ting bands of pale coloured minerals (epidote,clinozoisite, quartz) and green coloured actinolite.

The actinolite crystals occur as slender prismsor needles oriented with their lengths parallel toschistosity.

Clinozoisite crystals are present as colour-less granules elongated in the direction of theschistosity. This mineral also occurs as veinsparallel to, as well as cutting across, the schisto-sity. Epidote occurs as pale green grains which arealso elongated in the direction of the schistosity.

PKRTAMKA VOL

Description

Location

ElevationLandform

VegetationDrainageClassificationof soil

TABLE 1of the weathering profile developedover Amphibole Schist.

: Road-cut along Kuala Lumpur-Karak Highway, at 54 km stone.

: 130 m above sea level.: Dissected hilly terrain. Profile is

located on a gently sloping partof a hill.

: Old rubber: Well drained: FAO/UNESCO Legend:

Acric FerralsolSoil Taxonomy:Clayey, kaolinitic, isohyper-thermic Typic Hapludox

Profile Description

Al 0-0.20 mYellowish red (5YR 5/8); clay; weak, granular;very friable; few fine vein quartz fragments; fewfine roots; few fine pores; gradual smoothboundary.

Bol 0.20-0.90 mYellowish red (5YR 5/6); clay; weak, finesubangular blocky breaking into granules; veryfriable; few fine roots; few fine pores; gradualsmooth boundary.

Bo2 0.90-2.0 mYellowish red (5YR 5/6); clay; weak, finesubangular blocky; friable; few fine roots; few finepores; abrupt smooth boundary.

Cr 2.0-5.0 m (Upper saprolite)Yellowish red (5YR 5/6 and 5YR 4/6); softaltered rock with distinct schistosity and jointplanes; breaks easily between the fingers;evidence of faunal activity; diffuse boundary.

Cr + R 5.0-8.4 m (Upper saprolite)Strong brown (7.5YR 5/8) and yellow (10YR8/8); soft altered rock with few corestones whichare coherent; distinct schistosity and joint planes;evidence of faunal activity; gradual smoothboundary.

Cr + R 8.4-15 m (Lower saprolite)Yellowish red (5YR 5/6) and reddish yellow(10YR 6/8); soft altered rock with many large(1 to 2 m) corestones which are very coherent;weathering rims occur on these corestones;schistosity and joint planes are very distinct.

13 NO. 1, 1990 87

S. / A l Y A H AM) G. STOOPS

Fig. 2. Micro fabric of the fresh amphibole schist and its weathering rim in the lower saprolite.

A Tightly packed prismatic crystals of act!nolitr surrounded by granular ones which are probably the epidote minerals.

B : Porous microfabric of the weathering rim consisting of booklets of kaolinite.

C : Booklets of kaolinite are closely associated with tubular halloysite and some globules.

D : Locally the globules, most probably hematitic, form an important component of the fabric.

Polycrystalline quartz is present as veins run-ning parallel to schistosity. A few grains ofmicrocline are associated with it.

Micromorphology of the Weathering StagesIt was not possible to follow closely the alterationof each individual mineral in this profile. Ac-tinolite seems to be the first mineral to weather,mainly by dissolution, leaving a crust which isyellow to dark brown. There is a sharp boundarybetween the fresh rock material and the alterationproduct. At this boundary, the iron released isseen to coat the epidote. The alteration productsare described below as observed in the differentrock samples collected.

(a) Weathering rim around the corestones in the lowersaprolite.

In thin sections, the pale yellow weatheredmaterial shows broad bands composed of vermi-

form kaolinite in a micromass of finer kaolinite.Streaks of opaque brown iron oxyhydrates areoriented parallel to the original schistosity. Inother parts, the groundmass is masked by brownopaque amorphous substances. The iron is onlyslightly extracted when the thin sections aretreated with dithionite-citrate-bicarbonate solu-tion (Bullock et al., 1975).

The changes occurring in the amphiboleschist due to weathering can also be clearlyobserved under SEM. Fig. 2 shows the microfabricof the fresh amphibole schist and its weatheringrim. The fresh rock material (Fig. 2A) has acompact microfabric composed of tightly packedprismatic crystals of actinolite surrounded bygranular epidote. In the weathering rim (Fig. 2B),these prismatic grains have completely dis-appeared. The microfabric is porous and consistsmainly of kaolinite booklets 30 to 50 fim long. At

88 l'KRTANIKA VOL. 13 NO. 1, 1990

STUDY OK THE FERRALLITIC WEATHERING OF AN AMPHIBOLE SCHIST

Fig. 3. Micro fabric of the am phi bo/e schist and its weathering rim in the upper saprolite.

A : The fresh rock is composed of fibrous actinolite showing a preferred orientation,

H : The micro fabric at the boundary of the weathering rim shows an abrupt change from fresh rock (right) to the altered part (left). 'The

fibrous mineral has disappeared in the groundmass

C : 1 he porous microfabnc consists of globules of hematite disseminated in the groundmass.

I) ana h Well crystallized gibbsite occurs in between a framework which follows the orientation of the original acttonolite grains.

/* Detail of the framework, composed of goethitc.

higher magnifications, (Fig. 2C) tubular halloysiteand globules of about 3 \xm in diameter areobserved closely associated with these booklets.These globules (Fig. 2D), which are probably ofhematitic material, correspond to the reddishiron oxyhydrate droplets in the thin sections.

(b) Weathering rim around the corestones in the uppersaprolite.

The weathering rim surrounding the fresh rockof a corestone sampled from the upper saproliteis dark brown in colour and shows a network ofyellowish brown crystalline iron oxyhydrates

PKRTANIKA VOL. 13 NO. 1, 1990 89

S / . U T A H AND (i STCX >PS

oriented parallel to the original schistosity. Finegranular gibbsite occurs in between this networkof iron oxhydrates (probably goethite). In someparts, a mixture of iron oxyhydrates and kaolinitcoccurs as lineaments following the schistosity,with gibbsite filling the spaces in between. Thegibbsite is believed to be the alteration product oiepidote and clinozoisite as both these minerals arcrich in aluminium, and because it occurs in placeswhere these two minerals were observed in thefresh rock material i.e. in between the actinolitecrystals. The weathering of the fresh rock materialoccurring in this part of the profile was alsoobserved under SEM. Fig. 3 shows the microfabricof the fresh amphibole schist and its weatheringrim. The fresh rock material (Fig. 3A) is com-posed of fibrous grains of actinolite showing apreferred orientation. There is an abrupt changein the microfabric at the boundary of the weather-ing rim (Fig. 3B). The altered part is more porousand the fibrous mineral is altered. The followingminerals are identified: globules of hematite(Fig. 3C) are found disseminated in the ground-mass while well crystallized gibbsite (Fig. 3D)occurs in between actinolite grains (Fig. 3E). Athigh magnification, this framework is actuallycomposed of goethite (Fig. 3F).

(c) Material in between the corestonesThe samples are homogeneously stained brown ordark-brown. Much of the groundmass showsdistinct relict schistosity due to the parallel align-ment of the iron oxyhydrate crystalline frame-work. The main clay mineral identified is kaolinitewhich occurs as vermiforms or booklets in thepaler coloured parts. Occasionally, iron oxidesoccur as reddish droplets disseminated throughoutthe groundmass. Gibbsite is rarely detected insuch large masses as seen in the rim samples.

Excremental infillings with crescent-likeinternal fabric commonly occur in between theschistosity planes or along planar voids cuttingacross the schistosity (Fig. 4). In other samples,faunal activity causes breakup of the rock fabricleaving fragments of rock in the voids togetherwith excrements. It is clear that faunal activity isthe most important agent of pedoplasmation inthese materials.

The soil material in the joint planes has alight red, dotted micromass with a mosaic tostipple-speckled b-fabric. Only a few quartz grains

Fig. 4, A planar void excremental infilling nt-like internalfabric which occurs in the saprolite sample (PPL, x 14)

and some iron impregnated rock fragments arepresent, giving rise to an open porphyric c/f-relaied distribution. Many fine (10-30 \xm) round-ed reddish opaque nodules are also present. SEM-observations of the rock fragments show thepresence of tubular halloysite on the edges andbetween the lamellae; the soil material consistsof booklets of kaolinite and globules. Thin veinscontain goethite discoids. The overlying soilmaterial has a crumb to granular microstructure,with a dotted, reddish brown micromass showingdominantly stipple speckled b-fabric. Few grainsof quartz and runiquartz are embedded in theclay.

Mineralogical ChangesThe alteration of the amphibole schist in thelower saprolite is studied by examining the X-raydiffractograms of the fresh rock material (R4),its weathering rim (Cr5(4) and the saprolitematerial above it (Cr4) (Fig. 5). The fresh rockshows diffraction lines of actinolite, epidote andsome trioetahedral chlorite (the 0.29 nm reflectionof epidote is very weak on the diffractogrampresented in Fig. 5} but was much stronger on aless oriented preparation where, however, the1.42 nm reflection of chlorite is missing). In theweathering rim, actinolite, apidote and chloritedisappear immediately and completely, leavingonly high defect kaolinite (no distinct 11 T peak).goethite (0.418 nm) and traces of gibbsite(0.485 nm). Kaolinite becomes the dominantmineral in the saprolite with smaller amounts ofgoethite. X-ray diffraction thus confirms themicromorphological observation.

90 PERTANIKA VOL. 13 NO. 1, 1990

STUDY OF THE FKRRALLITIC WEATHERING OF AN AMPHIBOLE SCHIST

a

I

Fig. 5. X-ray diffraction pattern of the fresh amphibolite schist (R4), its weathering rim (Cr5(4)) and the saprolite material above

it(Cr4). (A m aetionolite, E = epidote, Cl = chlorite, K = kaolinite, Gi = gibbsite, Go = goethite).

The weathering rim of the corestone in theupper saprolite (Rl , R2) shows that gibbsite is thedominant mineral, followed by goethite. A sharppeak at 0.445 nm, indicates the presence ofhalloysite. Kaolinite occurs only as traces.

X-ray diffractograms of saprolite samples inbetween the corestone (Cr6, Cr2(2) and Cr2(3)also show the dominance of kaolinite as well asthe abundance of goethite and gibbsite. In Cr6 nodistinct 11 T peak of kaolinite is present, indicatinga high-defect kaolinite, whereas a somewhatbetter organized kaolinite is found in Cr2(2), witha Hinckley Index of 0.32.

The clay fraction of the soil material in therelict joints of the upper saprolite consists mainlyof kaolinite and goethite, with some traces ofhalloysite. The silt fraction has, in addition, aconsiderable amount of gibbsite. The overlyingsoil material has a similar composition except forthe absence of halloysite and the presence of asmall amount of irregular mixed layers in the BOiand BO2. The crystallinity of the kaolinite is muchbetter than in the saprolite, with values of 0.44for the Hinckely Index, pointing to a mixture ofa low defect (about 6%) and a moderate to highdefect kaolinite.

PERTANIKA VOL. 13 NO. 1, 1̂ 90 91

S. ZAUYAH AND G. STOOPS

Chemical Changes during Isovolumetric RockWeatheringThe isovolumetric weathering can be followedonly over a short distance from the fresh rockmaterial to the weathering rim and the saprolitenearest to it. The chemical composition, bulkdensity and some other parameters of thesematerials are given in Table 2. From the weather-ing index of Parker (1970) one can conclude thatweathering is almost complete in the saprolite.The results of the isovolumetric calculationsaccording to Millot and Bonifas (1955) arerepresented in Table 3, where total iron has beensplit up into iron bound in the mineral lattices andfree iron. Ca, Mg, Na and K are lost rapidlyduring weathering, as is a large part of the silica.Looking to the evolution of the data for iron inprimary minerals (both in silicates and ores), it

TABLE 2Chemical composition of the amphibole schist and

its weathered products (in weight %)(LOI = loss of ignition), free iron content,

Si/Al molar ratio, WIP (weathering index ofParker) and density.

Constituents

SiO2

A12O3

Fe2O3

TiO2

MnO

CaO

MgO

Na2O

K2O

LOI

Total

FREEIRON %

SiO2/Al2O3

mole ratio

WIP

DENSITYg/cc

Rock(R4)

48.15

12.10

9.00

0.67

0.21

15.80

12.00

1.45

0.35

1.50

101.23

0.29

6.8

89.0

2.55

Weathering Rim(Cr5(4))

34.51

17.62

38.11

1.69

0.25

0.19

0

0.59

0

8.05

101.01

32.66

3.3

6.0

1.22

Saprolite(Cr4)

39.49

25.08

23.50

1.88

1.37

0.04

0

0.45

0

10.01

101.82

14.08

2.7

4.2

1.16

TABLE 3Chemical composition of amphibolite schist and

its weathered products recalculated by usingthe isovolumetric method (values expressed

in cgcrrr1). Fe2O3 P : iron in primaryminerals (silicates and ores),

Fe2O3 D : dithionite extractable or free iron.

Constituents Rock Weathering Rim Saprolite(R4) (Cr5(4)) (Cr4)

SiO2

A12O3

Fe2O3 P

Fe2O3 D

T102

MnO

CaO

MgO

Na2O

K2O

LOI

122.8

30.9

22.3

0.7

1.7

0.5

40.3

30.6

3.7

0.9

3.8

42,121.56.7

39.8

2.1

0.3

0.2

0

0.7

0

9.8

45.829.1

10.916.4

2.2

1.6

0.05

0

0.5

0

11.6

is clear that part of the iron-containing mineralshave been weathered (loss of lattice iron), whileothers resist. The latter are most probably theopaque ores, as both chemical and mineralogicaldata show that actinolite and epidote have dis-appeared. On the other hand, a considerable(absolute) accumulation of free iron has takenplace in the weathering rim, corresponding to itsdarker colour. This conclusion is corroborated bythe presence of crystalline goethite and hematitenodules, as shown by XRD and micromor-phology. In the saprolite the iron accumulationis far less pronounced.

The free iron content of the saprolite furtherdecreases towards the soil, but values of 17% arereached in the BO horizon. The amount ofoxalate extractable iron is very low (0.26% in theBOi and 0.14% in the BO2), indicating that allis practically present in a crystalline form.

CONCLUSIONSDue to the fine texture of the rock material, it wasnot possible to follow the weathering scheme ofeach mineral individually. It is evident, however,that actinolite is the first mineral to disappear,followed by the epidote minerals. Similar conclu-

92 PERTANIKA VOL. 13 NO. 1. 1990

STUDY OF THE FERRALUTIC WEATHERING OF AN AMPHIBOLE SCHIST

sions can be drawn from the data presented byDe Coninck et at. (1987). As far as could be seenby SEM, congruent dissolution had taken place.

The alkaline and alkaline-earth elements areremoved immediately and practically completely,as is a part of the silica. The other part recom-bines with the aluminium set free during weather-ing of the epidote minerals to form kanditeminerals. Initially, halloysite and kaolinite areformed in the lower saprolite, and kaolinite andgibbsite in the upper saprolite. This difference inthe secondary products formed can be explainedby stronger leaching in the upper part (gibbsiteformation), and a more moist environment in thelower part (halloysite). At all stages, a typicalferrallitic weathering is observed.

The weathering front is abrupt and weather-ing is immediately almost complete. The rockstructure is preserved, however, over largedistances and pedoplasmation proceeds alonggeological structural planes. The soil materialfound in joint planes has the same properties asthe overlying soil material, except for the presenceof small rock fragments and a denser micro-structure. The soil itself is very clayey with arelatively high free iron content, in accordancewith the composition of the parent rock.

ACKNOWLEDGEMENTSThe first author wishes to thank UniversitiPertanian Malaysia for the research grant extend-ed towards this study. Work at the StateUniversity of Ghent was carried out within theframe of Research Grant No 2.9010.88 of theNational Fund for Scientific Research.

REFERENCES

BULLOCK, P., P.J. LOVELAND and C.P. MURPHY.

1975. A Technique for Selective Solution of IronOxides in Thin Selections of Soil. J. Soil Sci.26 (23): 247-49.

BULLOCK, P., N. FEDOROFF, A. JONGERIUS, G.

STOOPS and T. TURSINA, 1985. Handbook for SoilThin Section Description, 152 p. England: WaineRes. Publ.

DE CONINCK, F., G. STOOP and E. VANRANST, 1987.

Mineralogy and Micromorphology of a Soil Topo-sequence near Mtdi (Lower Zaire) on Chloritic

Green Rocks. In Geochemistry and Mineral Forma-tion in the Earth Surface, ed. R. Clemente andY. Tardy, p. 157-174.

ESWARAN, H. and C.B. WONG, 1977. A Study of

a Deep Weathering Profile on Granite in PeninsularMalaysia. I: Physico-chemical and Micromorpholo-gical Properties. II: Mineralogy of the Clay, Silt andFractions. Soil Set, Soc. Am. J. 42: 144-53.

HlNCKLEY, D.N., 1963. Variability in "Crystallinity"Values among the Kaolin Deposits of Coastal Plainof Georgia and South Carolina. Clays and ClayMinerals 11: 229-235.

HUTCHISON, C.H., 1974. Laboratory Handbook ofPetrographic Techniques. Wiley-Interscience.

M E H R A . O . P . and JACKSON, M.C., 1960, Iron-oxideRemoval from Soils and Clays by Dithionite-citrate System Buffered with Sodium Bicarbonate.Proc. 7th Intern. Conf. on Clay, 1959. p.317-327.

MlLLOT, G and BONIFAS, M., 1955. TransformationIso-volumetrique dans les Phenomenes de Laterisa-tion et al Bauxitisation. Bull. Serv. Carte Geol. Alzs.Lorr., 8: 3-20.

PARKER, A., 1970. An Index of Weathering for SilicateRocks. Geological Magazine 107: 501-504.

RICHARDSON, J . A., 1947. The Origin of the Amphi-bole Schist Series of Pahang, Malaya. GeologicalMagazine 84: 241-249.

ROE, F.W. 1951. The Geology and Mineral Resourcesof the Frasers Hill Area, Selangor, Perak andPahang, Federation of Malaya, with an Accountof the Mineral Resources. Mem. 5 Geol. Survey,Fed. Malaysia 138 p.

SCHWERTMANN, U., 1964.. Differenzierung derEisenoxiden des Bodens durch Extraktion mitAmmoniumoxalat Losung. Z Pflanzenern. Dung.Bodenk 105: 194-202.

STOOPS, G., H J . ALTEMULLER, E.B.A. BISDOM,

J. DELVIGNE, V.V. DOBROVOLSKY, E.A. FITZ-

PATRICK, G. PANEQUE and J. SLEEMAN. 1979.

Guidelines for the Description of Mineral Alterationsin Soil Micromorphology, Pedologie 29: 121-135.

YEOW, Y.H., 1975. Weathering of Rocks in HumidTropical Conditions. PhD Thesis, Univ. Malaya.155 p.

ZAUYAH, S., 1986. Characterisation of some Weather-ing Profiles on Metamorphic rocks in PeninsularMalaysia. Doctorate Thesis, Univ. Gent. 388 p.

(Received 17 October, 1989)

PERTANIKA VOL. 13 NO. 1, 1990 93