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THE BENTONITES OF CABO DE GATA

(SOUTHEAST SPAIN) AND OF GUELAYA

VOLCANIC PROVINCE (NORTH MOROCCO)* by

J . L. MXRTLN VIVALDI

Estaci6n Experimental del Zaidin, C.S.I.C., Granada, Spain

ABSTRACT

Volcanic activity was important in Spain during the second half of the Cenozoic Era. I t was closely related to the late kinematic and subsequent periods of the Alpidic orogenic cycle. Manifestations of the volcanic activity are seen in several parts of the Iberian Peninsula, but the main ones were confined to a few rather individualized zones. Cabo de Gata, Cartagena, and MazarrSn show a strong similarity, as does the Guelaya volcanic province, Morocco. The rocks (rhyolites, dacites and andesites) are clearly calcalkaline and, in many places, strong contamination processes have been demonstrated. The eruptions were, at least in part, fissural and fill important fractures, mainly nor theast - southwest. They occurred just after the more hnportant folding in the Betic-Riffien orogen. In these regions bentonite has formed by alteration of volcanic material.

The most important deposits arc in Sierra of Nijar and Gata (Almeria, Spain) and in the Monte Tidinit (Morocco). The Cabo de Gata bentonites are composed mainly of calcie and calcosodie montmorillonites. Palygorskite has been found in some places.

The bentonite of the Monte Tidinit is mainly calcium montmorillonite but some samples contain cristobalite. In Monte Maazza there is also a sedimentary deposit, consisting of a complex mixture of endellite, halloysite, gibbsite, montmorillonite and a luni te-- probably of hydrothermal origin. Halloysito is the main component: it is accompanied by gibbsite in the bot tom layers and by montmorillonite and alunite in the top ones.

The ground clay, after processing by cation exchange or acid activation, is used for several industrialproducts, such as soaps and detergents, cosmetics and pharmacy; but the main use is for drifting muds, foundry molds, and clarification of mineral andvegetable oils.

All the bentonites are amenable to acid activation but the natural mixture of halloysite and montmorifionite from Monte Maazza gave the best results in tests on lubricating otis at a laboratory scale.

Research still in progress on the rheology of suspensions of the Almerla bentonite contaminated with electrolytes gave interesting results using several thinner and filter oss control agents.

M I N E R A L O G Y A N D G E N E S I S O F T H E D E P O S I T S

The Volcanic Regions T h e g e o g r a p h i c con f igu ra t i on o f S p a i n (So16 Sabar i s , 1938, p .267) is d u e to

t h e d i s t r i b u t i o n o f t h e fo l lowing s t r u c t u r a l e l e m e n t s : T h e c e n t r a l p l a t e a u ,

* Presented before the 10th Conference in the Symposium on Bentonites, and published by permission of the Director of the EstaciSn Experimental del Zaidin.

327

328 ELEVENTH NATIONAL CONFERENCE ON CLAYS AND CLAY IV~INERALS

with its mountainous rim; the depressions outside this plateau (Ebro, Guadalquivir) and the peripheral ranges. Among these are the Betic and Pyrenaic orogenic systems. Most hypotheses relating to the trend of these folds in the Iberinan peninsula note their continuation to the north of Africa along the Riffien Atlas, after a deflection at the Strait of Gibraltar.

In relation to the late kinematic and subsequent periods of this Alpidic orogenic cycle, volcanic activity has been important in Spain during the second half of the Cenozoic Era. Manifestations of volcanic activity are seen in several parts of the Iberian Peninsula, but the main ones are confined to a few rather individualized zones. Cabo de Gata, Cartagena and Mazarr6n are par t of a single volcanic region which extends to the south through the Alboran isles to the Guelaya volcanic province. Parga Pondal (1935) names this region "zona orog6nica b6tica"; it is shown as a hachured zone in Fig. 1, where some other volcanic regions in the peninsula can be seen.

-- - L . , ~ , _ . c ~ . % , ~ / ~

ugal ~ . J ~ z "

/ ~ ) . - MADRID -//J-- %,9 \ ~

~' :#BON ~) VALENOI-A'~ ~ - " ~

Cabo de Gata

FIatrR~ 1.--Volcanic regions in the Iberian peninsula (Parga Pondal, 1935).

The Volcanic Rocks

The Cenozoic volcanic rocks of these regions were first studied by CalderSn (1882) and Ossan (1889; 1891a; 1891b) and more recently by Parga Pondal (1935), Bnrri and Parga Pondal (1948), Fuster and Ibarrola (1952), San Miguel, Almela and Fuster (1952), Fuster and de Pedro (1953), and Fuster (1956a; 1956b; 1957).

The volcanic region of Cabo de Gata is composed (Fig. 2) of three almost parallel ranges trending northeast-southwest: the easternmost range (Sierra del Cabo y Mesa de Roldan), a middle range (La Serrata), and the western- most one having centers of eruption in four zones (I-Ioyazo, Vera, Mazarr6n and Cartagena). As the bentonites of this region are found only in the Serrata and recently at several points in Sierra del Cabo, in its northern part, we shall refer only to these rocks. The dominant volcanic rock of the Serrata (Ossan,

THE BENTONITES OF CABO DE GATA 329

1889) is a hornblende daeite. Smaller amounts of a pyroxenic andesite locally intrude the daeite mass. Abundan t volcanic tuff, perlite and, pumice overlie the dacite. I n Sierra del Cabo on the contrary, pyroxene andesites are the most common rocks.

I n a recent s tudy of the volcanic rocks of the Serrata, Fuster (personal communication, 1961) found perlites in welded lavas, amphibolic daeites and pyroxenic andesites. The present au thor has verified the presence of these types of rocks, at least in the regions where the clay deposits are located.

According to the observations o f Ossan, the flow structure or amygdaloid character typical of young volcanic products is absent. He thinks the volcanic rock originated as a great flow t h a t later was eroded, giving birth to dome- shaped hills. However, we have found fragments o f perlites with typical amygdules, f rom 2 to 4 cm in length.

I n regard to the relative age it seems tha t the oldest rocks (Ossan, 1889) are the hornblendic and micaeeous andesites and the hornblendie dacites (pre-Pliocene and subaerial), and tha t the pyroxenie andesites, liparite, and pumiceous tuff are younger (Plioeene). Fuster (personal communication, 1961) thinks the oldest is the perlitie welded tuff.

I n the Guelaya province are two volcanic complexes (Fuster, 1956a;

FIGUI~E 2,---The volcanic region of Cabo do Gata, showing location of bentonites and samples. (1) Archidona deposit; (2) Cortijo Blanco (test pit); (3) Pecho de los Cristos South (test pit); (4) Peeho de los Cristos deposit; (5) Pecho do los Cristos (North) deposit; (6) 1)alma del Muerto, exhausted deposit; (7) Huerta Grande (los Trances) deposit; (8) l~srnbla de los Perez deposit; (9) Cerro del Aire (test pit); (10) I~ambla del Cuervo (~est pit); (ll) Cortijo Colorado deposit; (12) Majada de las Vacas deposit.

330 ELEVENTH NATIONAL CONFERENCE ON CLAYS AND CLAY iVJ~INERALS

1956b): (a) the Gurugu complex, with emission centers at the Gurugu and Tidinit, among others, and made up of an accumulation of basic and intermediate rocks of andesitic composition; and (b) the Tres Forcas complex, composed almost exclusively of acid rocks (dellenitic and rhyolitic) and even more acid pyroclastic products. Volumetrically unimportant basaltic flows are present locally.

The rocks of the Gurugd complex are potassium-rich andesites of vitreous porphyritic texture, with phenocrysts of plagioclase, biotite and pyroxene. In addition to these, Fuster mentions more vitreous and acidic types tha t approach the chemical composition of the dellenitic or rhyolitic lavas of Tres Forcas.

The age of the volcanic activity is cited as pre-Pliocene (Tres Forcas) and Pliocene (Gurugfi and Tidinit). The basaltic flows must be younger latest Pliocene or Quaternary.

The volcanic activity in each complex, then, became progressively more basic. From this fact and after careful study of the chemical composition of the rocks (Fuster, 1956b; 1957), it is deduced tha t the rocks did not originate from simple magmatic differentiation but from the strong sialic formation that is present in all evolving synclinal zones. The volcanic rocks in the Guelaya must represent, then, the production of palingenic acid magmas.

Although we have yet no detailed data for the Serrata and the south of Sierra del Cabo, we may recall that Fuster (1956a), from his researches on the north par t of the latter, concludes that, as for the Guelaya, there are also contaminations. We think thus tha t in the series of andesite-rhyolites ac- companying the Riffien-Betic folding we are dealing withlate-orogenic phases, in the sense of Stille, with at some centers stages of subsequent and final basaltic volcanism.

The Bentonites

The Moroccan bentonite deposits are located in the Tidinit volcanic complex* and the Peninsular bentonites in the Serrata and Sierra de Gata. Deposits of bentonites near Oran have been studied recently by Sadrs Millot and Bonifas (1955); they originated by alteration of rhyolite, and their mineralogical composition is montmorillonite plus kaolinite. The rhyolite was altered along fractures by later volcanic action.

The Tidinit deposit.--Figurc 3 shows the location of the bentonite deposits of the Guelaya. They were fully described by Gutierrez Rios (1948) and Gutierrez Rios and Gonzs Garcia (1949).

In these earlier reports it was pointed out tha t the bentonites formed by alteration of the andesites. From a later and more careful chemical, optical and mineralogical s tudy of tha t series of rocks and alteration products we conclude (Gutierrez Rios, Martin Vivaldi and Pino Vazquez, 1957; Martin Vivaldi and Pino Vazquez, 1956b) tha t the parent rock is a leucorhyodacite,

* Some smaU deposits have been cited also in Tres Forcas and at the west of Cabo Quilates. (A. Gallego Bermejo, personal communication, 1961).

TIIE BENTONITES OF CA/dO DE GATA 331

similar to the more acid rocks cited by Fuster. The lateral gradation from the unaltered rock (sample 37) to the bentonite is illustrated in the analyses of Table 1.

The mineralogical formula for the bentonite (sample 33) is:

S+ 3 + 2 + [All.73sFe0.112Mg0.169] r A 1 3 + ~ia+ 1 L~"o.~2s ~ 3.775J 0 ~ o ( 0 H ) ~ % . 3 s "

FIGUBE

oo;o' o~ oo'7o' dso

3.--Location of bentonite deposits of the Guelay~ (North Morocco). (1) Tidinit deposit; (2) Maazza deposit.

X-ray diffraction maxima at 17 A, DTA curves for the series, and the appearance of the bentonite in the electron microscopes are shown in Figs. 4 and 5 and Plate la. The following facts are obvious: (a) The rock is vitreous, acid, and rich in allmlis; (b) Si02 has been gradually removed and Mg added (see molar ratios, Table 1) ; (c) free SiO2 is less mobile where the concentration of Mg is higher; and (d) samples richer in SiO2 contain more cristobalite.

From these facts the genetic process must be the following (Martin Vivaldi and Pine Vazquez, 1956b): The feldspar (phenocrystal and normative) is altered with removal of alkalis and silica. Every two parts of glass produce one part of montmorillonite, in agreement with Correns and Engelhardt 's (1938) results. Cristobalite is present only in those samples part ly altered to montmorillonite and must be derived from the SiO 2 that is removed, and later coagulated in part by the Mg ions. As the amount of cristobalite is less in

332 ELEVENTH NATIONAL CONFERENCE ON CLAYS AND CLAY MINERALS

TABLE 1.----MOLAL RATmS, pH OF SUSPENSmNS, FREE SiO2, SiO2]AluOs I~ATIO, AND MINERALOGICAL COMPOSITION DEDUCED :FROM X-I~AY DATA (TIDINIT DEPOSIT)

Sample

SiO~/Al~Os Fe20a/Al~Oa MgO/A12Os Ca0/Al~Oa

pH Percent free Si02 Si02/A12Oa*--

Montmorillonite Feldspar glass Cristobalite

37

8.30 0.03 0.00 0.34

8.3

5 +

35 32

5.53 0.07 0.22 0.14

8.59 8.40 1.39 1.71 7.68 5.38

I0 40 15 5 (?) (?)

10

7.73 0.04 0.05 0.23

29

6.44 0.07 0.30 0.09

8.28 10.30 5.51

60 0 (?) 3O

30

5.88 0.07 0.20 0.09

8.31 4.52 5.54

70 0 (?) 25

33

3.95 0.06 0.17 0.08

8.70 1.77 3.61

90

5

31

3.74 0.04 0.21 0.09

8.49 1.71 3.84

100

*Subtracting free silica

samples r icher in montmor i l lon i te i t m a y be supposed to be the basis of the t e t r ahed ra l l ayer of the montmor i l lon i te .

The Maazza deposit.---A bentoni te deposi t t h a t m a y be genet ical ly different is loca ted a t the foothil l of Maazza Mountain . F r o m the first s tudies (Gutierrez l~ios, 1948; Gut ierrez Rios and Gonzs Garcia , 1948) i t was concluded t h a t the ma in minera l was a member of the be ide l l i t e -montmor i l lon i t e iso- morphous series. Later , f rom a more de ta i led s t u d y of the same samples, we concluded t h a t the ma in components are endel l i te and hal loysi te (Mart in Vivaldi and Girela Vilchez, 1958). J eane t t e , Moni t i6n and 0 r t e l l i (1958) a r r ived a t s imilar conclusions. W e have cont inued the s tudy of these samples and a full r epor t will be publ i shed elsewhere (Girela Vilchez, 1961).

Maazza Mounta in , 7 k m from Melilla and nea r Zoco al H a d on the no r th side of the Gurugfi Mountain , is on the r im of T e r t i a r y sediments be tween Melilla and Tres Forcas . F igure 6 shows the s t ra t ig raph ic sect ion a t the loca l i ty from which the group of samples was collected, af ter the descr ip t ion b y Gut ierrez Rios (1948). L imes tone a n d sands tone layers, wi th fossils, are in te rbedded wi th the bentoni te . Above i t are r ed clays, calcareous mar l , l imestones, and a basa l t ic flow a t the top. These sediments are shal low-water deposi ts of Neogene age, contemporaneous wi th the bentoni tes from Tid in i t and Almerla , and thus are re la ted to the volcanism of the region.

The depos i t is r icher in a lumina in the lower layers and more silicic in the upper ones. Chemical analyses of the samples a re shown in Table 2.

Mineralogical analysis b y several exper imen ta l techniques shows t h a t the


4 6 8 EO

~ FIov~ 4.--X-ray diffraction maxima at 17 A for the Tidinit samples

(Gutierrez Rios, Martin Vivaldi and del Pino, 1958).

~~_ -_ ~

15oor {~ 2~176176 - ~

FIGTJ~E 5.--DifferentiM thermal curves for the Tidinit~ samples.

334 ELEVENTH iklATIONAL CONFERENCE ON CLAYS AND CLAY MINERALS

Levels Sample no.

Top of Te r t i a r y formation Zone

not quoted

, , ; - r, ; , , , , . ;" Sm

......::.:.....-.::....i,.~ _ _

Top of H formation ~ - . . . ~ . , o - - ~ . / / ~ , _

15's - 8 - -

1 5 ' s - 7, .

Gallery

13m

Lithology

Debris

Basalt flow

River bed O-

Thin-bedded Is.

Calcareous marl

Strongly altered volcanic rock

Ss. with calc. marl

Ss.

Blockish red cloy

6 _ 4

: 5 - 5 - - Gravel

2 _ _

H Test pit 8m

- 8 - I _ _ ~ _ _ ~ ,

F I o u ~ 6.--Geologic sections of the halloysite deposits (H = halloysite) (Martin Vivaldi and Girela Vilchez, 1959).

SS. Calc. ss. Fossiliferous clay+H

Fossiliferous calc. ss.

H Ls. wi th marine fossils

1.

TJ:IE BEI~TONITES OF CABO DE GATA

TABLE 2.--CHElVIICAI, AI~!ALYSES (MAAZZA DEI~OSIT)

335

SiO2 A1203 TiO2 Fe~O3 CaO MgO SOa Ign. Loss

Total H~O- CO2

M-2 M-3 M-4 ~ - 5 ~ - 6 ~ - 7 M-8 ~ - 9 M-10

39.10 33.19 27.12 35.42 43.65 43.65 45.50 38.82 43.20 37.32 45.65 41.84 43.07 44.75 38 .91 38.63 35.72 36.99 0.33 0.12 - - - - 0.35 0.36 0.27 - - - - 2.48 1.51 - - - - 3.00 1.43 0.70 1.76 0.91 1.60 - - 1.37 0.90 - - 2.48 - - 0.22 0.86 3.34 - - 1.08 - - - - 1.90 1.65 1.90 2.77

6.95 15:82 16 .85 28:32 20.75 9:77 9:84 13:52 13.27 16:05

99.99 100.33 99.73 100.13 101.52 98.57 100.52 98.64 100.78 3.83 3.78 3.36 3.37 4.90 5.5I 6.47 8.18 8.66 0.13 0.20 0.20 0.23 0.23 0.13 0.10 0.13 0.13

lower layers of the deposi t are composed of hal loysi te a n d gibbsi te , w i th some endell i te and sparse aluni te . The upper layers of the bentoni t ie sedi- men t s conta in haUoysite, endell i te , a d ioc tahedra l minera l of the mont - morfl lonite group, and alunite. AUophane is present in all samples.

P l a t e 2 shows X - r a y diffract ion pho tographs for the samples, and Figs. 7, 8 and 9 the i r D T A a n d the rmograv ime t r i e curves. The exis tence of endel l i te and montmor i l lon i te also was demons t r a t ed wi th D T A using the me thods of Sand and Bates (1953) (Fig. 10) and Sudo (1954) (Fig. 11). I t was necessary to de te rmine the ca t ion exchange capac i ty wi th Ba as the resul ts wi th am- monium were too high and var iable , owing to re ten t ion of a m m o n i u m sal ts (Gar re t t and Walker , 1959; W a d a , 1959; Thomas, 1960).

The a m o u n t of endel l i te also was es t ima ted b y re ten t ion of e thylene glycol. As a montmor i l lon i te minera l is also present i t was necessary to desorb samples af ter hea t ing i r revers ib ly a t 150~ B u t if ha l loys i te is m a i n t a i n e d under e thylene glycol for e x t e n d e d per iods of t ime i t swells as does t he endell i te . The electron micrographs (Plate 1) shows the t yp i ca l morpho logy of the hal loysi te crystals .

Semiquan t i t a t i ve spect roehemical analysis ind ica ted the presence of po- tass inm in all samples from the upper layers of the depos i t and i ts scarc i ty in the lower ones. This d i s t r ibu t ion mus t be re la ted to t he va r i a t i on in chemical composi t ion of successive volcanic emissions.

Quan t i t a t i ve de te rmina t ion of the minerals has been m a d e f rom X - r a y diffract ion pho tographs using an in te rna l s t anda rd ; f rom the areas under t he peaks of D T A curves prev ious ly ca l ibra ted wi th s t a n d a r d mix tu res ; from the rmograv imet r i c curves and t h rough re ten t ion of e thy lene glycol (Girela Vilchez, 1961 ; Mar t in Vivald i and Girela Vilchez, 1961). F igure 12 shows the mineralogical composi t ion as deduced from the above de te rmina t ions , b u t omi t t ing the ha l loys i te -endel l i t e di f ferent ia t ion in view of the l imi ta t ions imposed on i ts accuracy b y the a luni te accessory. I t is difficult to pos tu l a t e

336 ELEVENIU~ NATIONAL CONFERENCE ON CLAYS AND CLAY MINERALS

A, r

134 ~ ~ I ,,

Jr"

9 ~ 5

499 A

i55 ~r 9

~ '~581 950

"~ '~ 3 ~ I 5J5 - -

.FIGURE '/.--Differential thermal curves for the samples from Maazza,

PLA~E 1.--Electron micrographs. (A) Bentonite of Tidinit; fraction finer than 2/~. (B) S~mples 1 and 2 from M~azza.

(Facing p. 336)

. . . . . . . . . .

PLATE 2. X - r a y d i f f r a c t i o n p h o t o g r a p h s f o r s a m p l e s f r o m M a a z z a . G = g i b b s i t e ; A l u ~ a l u n i t e ; M e = m o n t m o r i l l o n i t e ; H~ ~ h a l l o y s i t e

" 2 H 2 0 ; H 4 ~ h a l l o y s i t e ' 4 H 2 0 .

PLATE 3.--General view of the mining operation at Los Trancos, in the Sierra de Gata.

THE ]~ENTONITES OF CABO DE GATA

2 2 -

20

18

16 E

14

B _ ~12 o

-JlO

. . . . . . . . . . . . I .~. 1,4 - 4

f / f f

. / ~ M - 5 / / / M - 2 ~ ..2-.-.-M- 3

/ /)i

6

4

2 j/.f~-'~/" 0 I ] I ' l I I I I I

100 200 300 400 500 600 700 800 900 1000 '~C

FIGURE 8.--Thermogravime6ric curves for Maazza samples 2 to 5.

M-10\ ~-9 22 ./~S~ M-9-T 20 . / y

...y . I M - 8 18

.E16 " . ........ .

~ 1 4 /

"if ~12 // ##1

6 / - z

2

0 100 200 300 400 500 600 ")90 800 900 1000 o C

FIGURE 9.---Thermogravimetrie curves for Maazza samples 6 to 10.

337

PLATE 4.--Photomicrographs of sample 120. (A and B) Plagioclase phenocryst in a vitreous mat r ix altered inside to calcium carbonate. (C) Zoned

plagioelase phenocryst. (D) Amphibole phenocryst. (Facing p. 337)

338 ELEVENTII NATIONAL CONFERENCE ON CLAYS AND CLAY MINERALS

/ % . M- 6 + Ethylene Glycol

ozz F m u ~ E 10.~Di f fe ren t ia l thermal curves for Maazza samples 6 and 9 t reated

with ethylene glycol.

FIGURE 1 1 . ~ i f f e r e n t i a l the rmal curve for Maazza sample 9 t rea ted wi th piperidine.


the genetic process for this deposit, but from analysis of the results compared with facts known from synthesis in the laboratory and the origin of similar deposits, we conclude tha t the clay minerals were formed by hydrothermal alteration of volcanic ash. The hydrothermal fluids removed abundant Si02 at moderate temperatures from the lower and presumably earlier-formed

100 - 9 0 -

8 0 -

7 0 -

6 0 -

5 0 -

40 - -

30- 20- 10--

O- l 3

~ AIIophane

~ ] Halloysite

S 6

~ Gibbsite

~ Alunite

7

il!llii~!

i 8 9 10 Sample

m Montrnorillonite

FIOURE 12.--Graph showing quantitative mineralogical composition of samples from Maazza.

parts of the deposit. I t seems tha t the volcanic glass was altered first to aUophane from which endellite crystallized; the excess of alumina produced gibbsite. The materials of the upper par t must have been formed by the action of acid fluids rich in potassium, removing less SiO 2 and thus permitting formation of a montmorillouite mineral together with alunite.

Almerla province deposits.--The bcntonites from Almer~a are found almost exclusively in the amphibole dacite zones. However, our recent field observations, not yet confirmed by laboratory results, indicate tha t these bentonites are linked genetically with perlites and possibly with volcanic ash. We have observed (Majada de las Vacas) localities at which an altered dacite is clearly transformed into bentonite in which the bentonite preserves texture of the parent rock. This is true particularly at Los Trancos, and also in Sierra de Gata. But transitions of altered dacite to bentonite arc not seen in the Serrata even though all the deposits occur where altered dacite is the dominant rock. The bentonite seems to be a subsequent fill, possibly an ash fall, which has since altered. Locally (Archidona), perlites in the bentonitic mass are digested and are transformed to red bentonite.

The descriptions tha t follow refer to samples from only two quarries: one in the Serrata (Palma del Muerto) and the other in Sierra de Gata (Los Trancos)*. A general view of the Los Trancos workings is shown in Plate 3.

* A full report including results On all the samples will be published elsewhere (Linares Gonzalez, 1961).


The series of samples from the Ser ra ta (Pa lma del Muerto) include nos. 1161-1166. They were selected from a zone in which green and red ben ton i t e (1166) grades into a ma te r i a l t h a t seems to be the a l te red pa ren t rock. Sample l13a is a ma te r i a l of qui te different character , loca ted at the ent rance to the gallery. No. 115 was selected from a poin t near 1166, f rom an extens ive green bentoni t ic mass t h a t seemed ve ry pure.

F igure 13 shows the D T A curves, and Table 3 shows the minera logical composi t ion deduced from the X - r a y diffract ion photographs . Table 4 refers to an or iented aggregate of < 2/~ e.s.d, for sample l13a, para l le l and per- pendicular to the X - r a y beam, and shows t h a t only in the perpendicu la r

t65 - - E L 88o J15

1161

1162

1163

1164

355

367

546

357

645

837 64?-

531

I165

I 16 ~ " - - ' - ~ ' x

350

354

675 847

835

V 9,5 84O

170 FIGURE 13.--Differential thermal curves for samples from Palma del

Muerto (Serrata de Nijar, Almeria).

T H E BENTONITES OF CABO DE GATA 341

TABLE 3.--MINERALOGICAL COMPOSITIOk'ff DEDUCED E~OY~ X-RAY DIFFI~ACTION ~EOTOOI~AP]~S (PALMA DEL MUERT0, SERI~ATA)

Sample Montmor i l lon i te F e l d spa r Quar tz Pa lygo r sk i t e Kao l in i t e

l13a 1161 1162 1163 1164 1165 1168 115

+ + + + + + + + + + + + + + + + + + + + + + + + + +

§ 2 4 7 + + + + § § + + § +

+ + +

+

+ + + § +

23

TABLE 4 . - - d SX~ACING A N D I N T E N S I T I E S O B S E I ~ V E D I N X - R A Y

DIF~'~AC~mN P~OTOQ~AP~S ( S ~ e L E l13a, < 2/x e.s.d.)

1" 2~ d I d I

10.59 s 17.60 10.51

8.92 6.50

4.48 4.22 3.94 3.79

3.47 3.34

3.22 2.99 2.91

s

s V l S

vis

v w

w

vis m w

vis vis

vis w

V W

6.50 5.43 4.48 4.20

3.81 3.68

3.28

2.95

2.58 2.45 2.17 2.12 1.79 1.67 1.56 1.54 1.50

v is v is m s s

W

W

V~V

Ff lW

m w

V W

V W

V W

V W

v w

V W

v W

* Or ien ted aggrega te parallel to X - r a y beam. Or ien ted aggrega te n o r m a l to X - r a y beam.

342 ELEVENTH NATIONAL CONFERENCE ON CLAYS AND CLAY I~INERALS

orientat ion can the palygorskite lines and hk b a n d for montmori l loni te be seen to be dis t inct from features which would have been afforded by a ny mica. Table 5 lists specific surface, and Table 6 chemical analyses of red a nd green montmori l loni te , Table 5 also lists the quan t i t a t ive es t imat ion of montmori l loni te for the series of samples, from X- r a y diffraction photographs, using as a s t andard for mixtures the <2/~ e.s.d, fract ion of sample 115 and as in terna l s t andard a sepiolite from Vallecas.

TABLE 5.--SPECIFIC SURFACE, AND PERCENT OF I~ONTMORILLONITE DEDUCED FROM X-RAY DIFFRACTION I)HOTOGRAPHS WITH INTERNAL ~TANDARD (~AL~A DEL

MU~TO, SEm~ATA)

Total Area External Area Swelling Area ~o Sample m2/g m2/g m2/g Montmorillonite

1161 1162 1168 116a 1165 1166 115

624 550 400 660 775 852 804

98 36 43 44

129 23 33

526 514 357 616 746 829 771

55 36 82 83 93 96

* See Table 3. No determination using internal standard was made.

TABLE 6.--C~EMICAL ANALYSES OF MONTMORILLONITE FROM PALliA DEL MUERTO (SERRATA)

SiO2 A1203 Fe203 l~IgO CaO H20 (-)

115 114 (Green) (Red)

61.90 16.39 6.32 4.58 0.65 9.54

99.38

60.55 18.87 6.88 5.30

8.88

100.48

Selected samples horn Sierra de Gata (Los Traneos) represent materials in a different stage of a l terat ion to bentoni te . Figure 14 shows the D T A curves; Table 7 the mineralogical composition from the X- ray data and the exchange capacity, and Plate 4 some aspects of the paren t rock (a hornblende dacite) under the microscope.

The exchangeable cations in all these bentoni tes (Serrata and Sierra de Gata) are about 70 per cent Mg, with 20 per cent Ca and 10 per cent alkali and hydrogen cations. The mineralogical formulas of the montmori l loni tes are:


Los Trancos (Sierra de Gata); sample 124:

3+ 3+ 2+ 3+ "4+ [All.22Feo.29Mgo.6o] [A]o.o6S13.94] "016(OH)2"xo.a3

La Palma del Muerto (Serrata); sample 115:

8+ ~+ 2+ (0H) 2 [A1L26oFeo.8ogMgo.4j [Si~ + ] 01o �9 xo.33

121

122 - - - - - ~ ~ ~ , 7 o f ~ 35o'S-"-"'.---~

447 1050

1 7 0 ~ , ~ " f

M/ 164

Fieu:aE 14.--DifferentiM thermal curves for samples from Los Traneos (Sierra de Gata, Almeria),

TABLE 7.--1V~INEI%AL CO~IPOSITIOIq DEDUCED FROM X-I%AY DIFFRACTION PHOTOGRAPHS, AND CATIO~NT EXCHANGE CAI'ACITY (Los T~-~cos, SIERRA DE GATA)

Montmorillonite Feldspar Quartz Biotite C.E.C

(1neq)

120

+ + + + + § + +

Samp~

121

§ § §

76.6

122

§ 2 4 7 + § §

91.6

124

§ 2 4 7 2 4 7 §

97.8

344 ELEVENTH NATIONAL CONFERENCE ON CLAYS AND CLAY !V[~ERALS

Alteration of the volcanic rocks of Almeria produces then a highly mag- nesian montmorillonite and, in several samples from the Serrata, attapulgite and kaolinite as well.

In the derivation of montmorillonite from its parent rock we note the removal of SiO 2 as well as addition of Mg. A semiquantitative spectrographic analysis of nearly fresh dacite, some altered daeites, and bentonite from Majada de las Vacas clearly shows an increase in Mg and a decrease in K, Rb, Cs, in passing from the unaltered rock to the bentonites. As is shown, this supply of Mg is as characteristic here as it is in the bentonites from Tidinit.

In the earliest research on these bentonitcs (Gonzs Gareia and Martfn Vivaldi, 1949; Martin Vivaldi and Gonz~lez Garcia, 1951), we frequently saw a fibrous mineral in the electron microscope. We later concluded that it was palygorskite and that it commonly is associated with the bentonites of the Serrata. But in the deposits of Sierra de Gata (Los Trancos) a pinkish material that fills cracks in the bentonitic mass shows a fibrous morphology and gives higher spacing in the X-ray diffraction photograph (ea.ll A) than palygorskite. We assumed it to be a member of the sepiolite-palygorskite group (Martin Vivaldi, Cano Ruiz and Fontbot6, 1956) but a more detailed study has led us to the conclusion that it probably is an intergrowth of sepiolite and palygorskitc (Martin Vivaldi and Linares Gonzs 1962).

The supply of Mg is higher in Almerla than in Tidinit. This fact and a less silicic parent rock account for (a) the fact that all silica has become part of silicates, leaving a very small amount that is extractable with Na2COa (less than 2 per cent) and no cristobalite ; and (b) the formation of magnesium- rich minerals of the scpiolite-palygorskite group.

Genetic Conclusions

We hope to get more conclusive experimental evidence but we may conclude that both volcanic regions the southeast of Spain and the Guelaya province--not only are genetically related to the Alpidic orogeny, but also show a clear parallelism in type and age of volcanism, types of volcanic rocks, and contaminants. Further we hope to demonstrate close similarity in the mode of alteration of the rocks and in genesis of bentonite.

In fact, these bentonites have been found in the Guelaya and in Almerla as alteration products from the vitreous and acidic rocks of the rhyolite- dacite series, where the andesites in both zones are only slightly altered. There, a supply of Mg to and removal of Si02 from volcanic vitreous cal- ealkalic acidic rocks with intermediate formation of cristobalite in some cases--seems to be the general outline in the formation of the bentonites. The affinity between both formations--Peninsular and Moroccan--is even closer, in the sense that later, more acidic hydrothermal activity has produced kaolin and jarosite locally in the Sierra de Gata and endellite and alunite in Maazza.

Despite this uniformity, the variety of volcanic rocks, their processes of

THE BENTONITES OF CABO DE ~ATA 345

contamination, and the variety of alteration products show the complexity of the volcanism associated with the late orogenic phase of the Alpidic folding in these regions.

P H u S T U D I E S

Much physico-chemical research carried out in our laboratory on these bentonites has been summarized at these conferences (Albareda, 1956). To these we may add the study of the action of diazomethane on montmorillonite (Martin Vivaldi and Hendricks, 1952 ; Martin Vivaldi and Pine Vazquez, 1956a; Martin Vivaldi, Pine Vazquez and Cane Ruiz, 1956), the study of the thermal decomposition of NH4 montmorillonite (Mart~n Vivaldi, Girela, Hernaiz and Rodriguez Gallego, 1959) the behavior of montmorillonite when treated with different exchange cations at various temperatures (Martin Vivaldi, MacEwan and Rodriguez Gallego, 1957) and the study of organic complexes of montmorillonite by DTA curves in normal and controlled at- mospheres (Martin Vivaldi, Girela Vilehez, Rodriguez Gallego and Fenoll Hath-All, 1.961).

TECHNICAL APPLICATIONS

Table 8 summarizes production and uses of the Almeria bentonites as reported by Minas de Gadar S.A. (Gallego, personal communication, 1961).

The bentonites from Sierra de Gate are activated by acid t reatment and sold as "Tierras decolorantes" for use in decolorizing vegetable and mineral oils. Some are simply ground and screened to several s tandard sizes for use in percolation processes and for treating gasoline in the vapor phase.

The bentonites from the Serrate were found to be poorest for acid activation at an industrial scale. After conversion to sodium bentonites through a process of cation exchange, they are used as drilling muds, as bonds for foundry molds, and in soaps and cosmetics.

Our laboratory experiments (Gutierrez Rios and Lopez Gonzs 1952a; 1952b; 1952c) have shown tha t all the bentonites described in the present paper are amendable to acid activation, but the mixture of endellite and montmorillonite from Maazza gave the best results when tested on a waste lubricating oil. We are now working with a standardized testing procedure for percolation and contact, using as standards a crude petroleum and a worn out lubricating off (Martin Vivaldi, I-Iernaiz and tIuertas, 1960). We have begun a study of the rheology of bentonite suspensions, mainly in the presence of saline contaminants. Up to the present we have tried only a filterloss control agent, a carboxymethylcellulose (here designated as E) ; and a thinner, an extract of humie acid (here designated as A).*

* A full record, including research using quebracho, pines ross, lignosulfonates, several earboxymethylcelluleses and pregelatinized starch, will be published elsewhere (Linares GonzMez, 1961).

346 ELEVENTH NATIONAL CONFERENCE ON CLAYS AND CLAY ~r

TABLE 8. PRODUCTIOI~, SALES AND USES OF ~:BENTONITAS" AND "TIERI~AS DECOLORANTES", i~INAS DE GADOR S.A,, ALiWERIA (GALLEGO, personal

communication, 1961) Production in tons

Product

iodium bentonite ~aleinm bentonite ~Tierras decolorantes" rierras granuladas

1958

2.951 1.711 2.967

40

1959

3.689 1.859 3.468

1960

4.431 1.606 4.092

Sales in per cent (Based on 1958 production)

Uses %

Mineral oils Edible otis Gasoline in vapor phase Drilling muds for oil wells Drilling muds for water wells Foundry molds Conglomerate eoals Soaps, beer, wine and other uses

16.5 24.0 0.5

14.0 2.5

40.5 1.3 0.7

As s tandard bentoni te we used Gadorgel (almost sodic) as a 6 per cent suspension in water, aged 24 hr. Sodium chloride was used at four concentrat ions from 0.3 to 30 per cent.

Th e following cases were studied: 1. Bentoni te suspension unt rea ted .

+ NaC1 at four concentrat ions of NaC1. + E for three concentrat ions of E. + E + NaC1. The four NaC1 concentrat ions for each

2. Bentoni te 3. Bentoni te 4. Bentoni te

B § 5. Bentoni te 6. Bentoni te

B+A.

+ A for the two different concentrat ions of A. + A + NaC1. The four NaC1 concentrat ions for each

Table 9 shows the properties of the bentoni te suspension wi thout a ny addi t ive; Fig. 15 shows the effect of sodic sal ini ty on bentoni te suspensions. Note t ha t a low salinity concentra t ion (about I per cent) gives a m a x i m u m on the viscosity curve typical of con tamina ted muds, b u t no other m a x i m u m is observed even up to 30 per cent salinity, as others (Rogers, 1953, p.299; Bergman and Fisher, 1950) have shown. The viscosity, then, is no t seriously affected b y medium or high concentrat ion of salt, bu t the water loss is strongly affected and the th ixot ropy becomes very low.

THE B E N T O N I T E S O F C A B 0 D E GATA

TABLE 9 . - - I~HEOLOGICAL AND OTHER PROPERTIES OF " G A D O R G E L "

347

Property 1 2

Viscosity (600 rpm) cp ; fresh susp. Viscosity (600 rpm) cp; aged susp. Viscosity at 80~ cp Initial gel, g 10 rain gel, g Thixotropy, g Water loss (ml) Filter cake, mm Yield bbl/Tm. pH

18.5 28 22 25 60 35 17.7

1.2 119.5

7.0

18

15 45 30 16

1. Reported by "Minas do Gador" ; Fresh 6 per cent aqueous suspension. 2. Six per cent aqueous suspension, aged 24 hr.

0 0 ~0

~20-

> 10=

0.3

W,L. BS --A

Visc0. B S

l ,

o 1o Is 2o 2s 3o No Cl q/I00

FIGUX%E 15.--Effect of NaCI on 6 per cent Gadorgel suspensions.

-90

-70 = s

o

-SO ~

..A

-30~

-10

Figures 16, 17, 18 and 19 show the effects of A and E, independent ly , on the bentoni te suspensions, wi thout saline contaminat ion. The water loss, viscosity and th ixot ropy are affected in the expected way, the thixotropie behavior of A being more satisfactory from a technical point of view. Figures 20-25 show the effect of the sal ini ty on both prepared muds (bentoni te + A, and bentoni te + E).

The water loss is corrected as much by the water loss control agent (E) as by the th inner (A), a t least up to medium salt concentrat ion and using the appropriate concentrat ions for A and E.

348 ELEVENTH NATION~m CONFERENCE ON CLAYS AND CLAY MINERALS

7 0 -

50-

> 4 0 -

co t o

10-

0.1 0.2 0.3 0.4 0.5 0.6 Woter Loss Control Agent, g / IO0

FIGUI~E 16.--Effect of water loss control agent (E) on Oadorgel suspensions.

~21

-2o

-19

o -IB .~o

c

-17o E m

--16 g 8

d 15

-14 ~

13

-12

-11

- I0

7O o~

0 6 0 (..9

'o 50

(.9 40

o

30 o

I-- 20

10

O - B E

0:1 ' 0:s 0:4 0:6 Woter Loss Control Agent, g/lOO

:FIGURE 17.--Effect of E on thixotropy of Gadorgel suspensions.


50-

40-

730-

20-

10 Vise. B A

~. i I i , 0~.B 01 0.2 0.3 0,4 0.5 Thinner, g/ lO0

FlOlJI~I~ 18.--Effect of thinner (A) on Oadorgel suspensions.

-21

-20

-19

- 1 8 "-3

-17 ,~o

- 1 6 _~

-14

=13

-12

-11

-10

The viscosity is preserved with E within reasonable values if used at medium concentration. Wi th A, results are good for both tested concentrations.

The thixotropic behavior of the m ud is maintained within correct values if we select the proper concentrat ion for E.

I n resum6: Suspensions of Gadorgel up to saline concentrat ion of 6 per cent have the right characteristics of a water based drilling mud, if there is no saline contamination.

Addit ion of the water loss agent prior to saline contaminat ion is not recommended because, a l though water loss is improved, viscosity and thixo- t ropy are worsened; bu t it can be used in saline water up to almost 6 per cent saline concentration.

The same is t rue for the thinner having the two concentrations tested, bu t in saline water it could be used up to almost l0 per cent salinity. I f the suspected saline contaminat ion is low the thinner can be used safely at a concentrat ion below 0.3 per cent.

We m a y mention, finally, some research pursued in order to prepare a fungicide by heating sulfur in the presence of bentonite (Martin Vivaldi and Rausell Colom, 1955). The best temperature of t rea tment is 200~ and 5 per cent of Mg0 is necessary to get stable suspensions, but with a particle size of less than 2F no Mg0 is necessary, and the pH remains neutral. The sulfur mus t be, at least in part, between the layers of the silicate, as shown


,,~ 60- ._o

'~50- i o

~40-

s 3 0 < # 2 2 0 - 1-

10 B A

0.I 0.3 0.6 Th inner , g / lOO

FIGURE 19.--Effect of A on thixotropy of Gadorgel suspensions.

70-

60

+

50-

&0-

>3

20

10

~ j J

sq~B E~ S

BE~S

BE, S

J ! I I I I I 0.3 3 6 10 15 20 25 30

Na CI, g / 1 0 0

FmU~E 20.---Effect of ~TaC1 on viscosity of Gadorgel suspensions plus E.

THE B E ~ T O ~ T E S oF CABo DE GATA 351

100- BE4S 90- B E ~ S .- B0~

c~70- m - BEIS

50-

~ 40-

~ 2 9

0,3 :3 ; 1'0 1'5 2'0 2'5 :30 No CI, g/IOO

I~'mURE 21.--Effeot of NaOl on water loss of Gadorgel suspensions plus E.

by the X-ray diffraction photographs of heated samples. At any rate, the swelling properties of the bentonite with water and glycol are not affected (Table 10). TechnicMly the product has very high activity as tested in the laboratory and in field experience (Tables 11 and 12).

TABLE 10.--d (001)SPxcI~G OF BENTONITE AND ITS COMPLEX WITH SULFUR

Untrea ted Dried at I10 ~ Dried a t 110 ~ Water t rea ted Ethylene glycol t rea ted Glycerol t rea ted

Tidnit "Bentoni te -su l fur" Bentonite Complex

15,3 9.82

17.0 17.7

15" 15" 11t 19 17.0 17.5

*. Band difficult to read. ~. Sealed in L indemann capillary tubing to avoid rehydrat ion.


90

80

?0

60-

o

.o 50~

..E I -

z,0-

30-

,.5~

1 0

i -1-' 03 :t ~ 10 15 20 25 30

Na CI, g / 1 0 0

FIGURE 22 . - -Ef fec t of NaCI on t h i x o t r o p y of Gadorge l suspens ions p lus E.

B A2S

~ 1 0 -

. . . . I I I t 0.3 3 6 10 1~5 2i0 25 30

Na CI, g/100

FmURE 23 . - -Ef fec t of NaC1 oil v iscos i ty of Gadorgel suspens ions p lus A.

BAtS

50-

.-= 40- E o

o

~

3

~ 2 0 -

10-

THE ~BENTONITES og CABO DE GATA

0.3 :~ 6 lb 1's ~0 2's Io .Na CI, g/lO0

FxouR~ 24.~Effect of NaC1 on water loss of Gadorgel suspensions plus A.

353

30-

~20

o

k5 10

0.3 3 ~ 1l~ 1~ Na CI, g/lO0

2'0 215

60"

FIGURE 25.--Effect of NaC1 on thixotropy of Gadorgel suspensions plus A.


TABLE II.~EFFECT OF "BENTONITE-SULFUR" COMPLEX ON GERMINATION OF Aspergillus sydowi (Bain. and Sart.) T~o~ ANn C~u~cK

Product ~o of Spores Mycelium Tube Germinated* Length (microns)

Sulfur complex with 33.3% S Sulfur complex with 10.0% S Sulfur complex with 5.0% S Sulfur complex with 1.0% S Ground Sulfur Bentonite

3.02 3.70 4.90 6.55

20.20 97.90

5-10 5-10

15 15

30-50 50-100

* 950 spores counted in each experiment.

TABLE 12.--I%EsULTS OF A FIELD EXPERIMENT WITH '~BENTONITE-SULFUR" COMPLEX

ON GRAPE VINE

Fungicide

~q. suspension of sulfur complex containing 1.5 per cent S

[d., containing 3 per cent S ~ulfur powder Blank

No. of Treated Trunks

18 18 16 6

g* Sulfur per Trunk

1.25 2.00

60.00

None None None Strong', with (sehw.) Burr.

Infection

Unclnula necatov

* Calculated from the amount of suspension or sulfur powder, used in every spray, required for proper coverage of fruit.

A C K N O W L E D G M E N T S

I wish first to thank the Clay Minerals Commit tee of the Nat ional Academy of Sciences-Nat ional Research Council and the Univers i ty of Texas for their kind inv i ta t ion to a t t end the Ten th Nat ional Clay Conference. I wish to thank also Prof. Fon tbo tg (Universi ty of Granada) and Prof. Fus te r (Univers i ty of Madrid) for suggestions and help, and m y co l labora to rs - -mos t of t hem men- t ioned in the b ib l iography- - fo r their valuable exper imenta l work. F ina l ly I wish to express m y high appreciat ion to "Minas de Gador, S.A.", for the ldudness and facilities offered us during our repea ted visits to their bentoni te workings.

T~E BE~TONIT~S OF CABO DE GATA 355

R E F E R E N C E S

Albareda, J. M. (1956) Spanish investigations on clay minerals and related minerals: in Clays and Clay Minerals, Natl. Acad. Sci.-Natl. Research Council, pub. ~56, pp.147-157.

Bergman, W. E., and Fisher, H. B. (1950) Bentonite suspensions; effect of NaC1, NaOIt, quebracho and sodium CMC upon physical properties: Ind. Eng. Chem., v.42, pp.1895-1900.

Burri, C., and Parga Pondal, I. (I948) Las rocas eruptivas de la Isle de Albors (Prey. de Almerla, Spain): Publ. Ext. sobre Geol. de Espa~a, C.S.I.C., v.4, pp.453-489.

Caldcron, S. (1882) Estudio petrogrgfico sobre las rocas volcs del Cabo de Gate e Isle de Albors Bol. Com. Mapa Geol., v.9, pp.33-414.

Correns, C. W., and Engelhardt, W. (1938) Ncue Untersuchungen fiber die Verwitterung des Kalifeldspates: Chem. Erde, v.12, pp.l-22.

Fuster, J. M. (1956a) Las erupciones deUenfticas del Terciario Superior de la rosa de Vera (Prey. Almerla): Bol. R. Soc. Espa~wla Hist. Nat., v.54, pp.53-88.

Fuster, J. M. (1956b) La provincia volcs de la Guelaya (Marruecos espafiol) : Est. Geol., v.12, pp.59-94.

Fuster, J. M. (1957) EvoluciSn magms de la provincia de ]a Guelaya (Norte de Marruecos) : Cong. Geol. Int., Mexico, X X Sesidn, Seci6n I, v.1, pp.71-100.

Fustcr, J. M., and De Pedro, F. (1953) Estudio petrolSgico de las rocas volcs lam- proiticas de Cabezo Maria (Almerla) : Est. Geol., v.9, pp.477-508.

Fuster, J. M., and Ibarrola, E. (1952) Estudio petrogrs y genStlco de las andesitas eordieriticas de la zone voles de Mar Menor (Murcia): Est. Geol., v.8, pp.245-299.

Garrett, W. G., and Walker, G. F. (1959) The cation-exchange capacity of hydrated haUoyslte and the formation of halloysite-salt complexes: Clay Min. Bull., v.4, pp.75-80.

Girela Vilchcz, F. (1961) Estudio del yacimiento de haloisita del Monte Maazza (Mar- ruecos), con una eontribuci6n a la t6cniea de A. T. D. y al ans miner~16gico cuantitativo de arcillas: Ph.D. thesis, Univ. of Granada (unpublished).

Gonzs Garcla, F., and Martin Vivaldi, J. L. (1949) Caracterizacidn y propiedades de una bentonite de Almerla: Anal. Edaf., v.8, pp.567-582.

Guti6rrez I~ios, E. (1948) Bentonitas espagolas: C.S.I.C. Ed., Pat. Juan de la Cierva, Madrid, 156 pp.

Guti6rrez l~ios, E., and Gonz~lez Garcia, F. (1948) Sobre le serie isomorfa montmorillonita-beidellita: Anal. Edaf. Fie. Veg., v.7, pp.605-621.

Guti@rrez Rios, E., and Gonzs Garcla, F. (1949) G6nesis de la montmorillonita de Marruecos espafiol: Anal. Edaf. Fie. Veg., v.8, pp.537-566.

Guti6rrez Rtos, E., and Lopez Gonzalez, J. D. (1952a) AcciSn de los s fuertes sobre los silicates de la eerie isomorfa montmorillonita~beidellita. I, Caracterizaci6n, constitutciSn y modificaciSnes en la composlci6n qulmica: Anal. Edaf. 2"is. Vet., v . l l , pp.225-254.

Guti6rrez Rios, E., and Lopez Gonzalez, J. D. (1952b) Id., II, ModificaciSn de la propiedades fisico-quimicas Superficiales: Anal. Edaf. t~is. Veg., v.11, pp.527-538.

Guti@rrez Rios, E., and Lopez Gonzalez, J. D. (1952c) Id., III , AplicaciSn industrial de las bentonitas sometidas a tratamientos s Decoloraei6n de aceites lubrificantes minerales: Anal. Edaf. Fis. Vet., v . l l , pp.539 551.

Guti6rrez Rios, E., Martin Vivaldi, J. L., and Pine Vazquez, C. del. (1957) G6nesis de al montmorillonita de Marruecos espafiol, H: Anal. Edaf. Fie. Veg., v.16, pp.787- 798.

Jeannette, A., MonitiSn, A., and Or~elii, L. (1958) Presence d ~ halloysite a 10 A dane le niveaux bentoniques pliocenes du gite de Maazza (~if. Oriental): Notes Serv. Geol. Maroc., v.16, pp.242-249.

Linares Gonzalez, J. (1961) Los yaeimientos de bentonite de la provincia de Almeria; Estudio mineralSgico y tgcnico : Ph.D. thesis, Univ. of Granada (in preparation).

356 ELEVEI~TH I~ATIOI~AL COlqFEREI~ICE ON CLAYS A2qD CLAY MII~ERALS

Martin Vivaldi, J. L., Cane Ruiz, J., and FontbotC, J. M. (1956) The bentonites from the volcanic region of Cabo de Gate (Almeria) : in Clays and Clay Minerals, 2~atl. Acad. Sei.-Natl. l~es. Council pub. 456, pp.181-184.

Martin Vivaldi, J. L., and Girela Vilchez, F. (1958) A study of the halloysite from Maazza: Silie. Ind., v.24, pp.380-385.

Martin Vivaldi, J. L., and Girela Vilchez, F. (1961) Contribution to the study of DTA technique. II, Standardization and quantitative estimations of some clay minerals (mlpublished).

Martin Vivaldi, J. L., Girela Vilchez, F., Hcrnaiz Bermudez de Castro, M., and Rodiguez Gallego, M. (1959)The thermal decomposition of NH4-montmorillonites, I : Clay Min . Bull., v.4, pp.81-87.

Martin Vivaldi, J. L., Girela Vilchcz, F., Rodriquez Gallego, M., and Fenoll Haeh-All, P. (1961) Estudio tCrmieo de eomplejos orgs de algunos minerales de la areilla (unpublished).

Martin Vivaldi, J. L., and Gonz~lez Gareia, F. (1951) CaraeterizaeiCn y propiedades de una bentonite de Ahneria, 2I: Anal. Edaf. l~is. Veg., v.10, pp.561-584.

Martin Vivaldi, J. L., and Hendricks, S. B. (1952) l~eactividad de los Jones /4 do las arcillas on disolventes no polares. I, AcciCn del diazometano: Anal. Edaf. ~is . Veg., v . t l , pp.601-629.

Martin Vivaldi, J. L., Hernaiz B. de Castro, M., and I:[uertas Gareia, F. (1960) Procedimi- ento standard pare ensayos de deeoloracidn de aeeltes per percolaeiSn y contacto: Internal Rept., Project E.9 (unpublished).

Martin Vivaldi, J. L., and Linares Gonzalcz, J. (1962) A random intergrowth of sepiolite and attapulgite: in Clays and Clay Minerals, 9th Conf., Pergamon Press, N.Y., pp.592-602.

Martin Vivaldi, J. L., MacEwan, D. M. C., and Rodriguez Gallego, M. (1957) Efeeto de la temperature de tratamiento en las dimensiones segdn v del reticule de ]a contmorillonita en funciSn de1 catibn de eatable: Internal Rept., Project E.1O (unpublished).

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