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Chemie der Erde 71 (2011) 337–347

Contents lists available at ScienceDirect

Chemie der Erde

journa l homepage: www.e lsev ier .de /chemer

atterns of rare earth and other trace elements in different size fractions of claysf Campanian–Maastrichtian deposits from the Portuguese western marginAveiro and Taveiro Formations)

osa Marquesa,c,∗, M. Isabel Prudêncioa,c, M. Isabel Diasa,c, Fernando Rochab,c

Instituto Tecnológico e Nuclear/GeoBioTec, Estrada Nacional 10, 2686-953 Sacavém, PortugalDepartamento de Geociências, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, PortugalGeoBioTec – GeoBiociências, GeoTecnologias e GeoEngenharias (Foundation for Science and Technology), Portugal

r t i c l e i n f o

rticle history:eceived 20 July 2010ccepted 20 February 2011

eywords:ize fractionsEErace elementseochemistryineralogy

ampanian–Maastrichtian depositsaleoreconstruction

a b s t r a c t

The Upper Cretaceous (Campanian–Maastrichtian) Taveiro and Aveiro Formations belong to the northernsector of the Lusitanian basin (Portuguese western margin). The Taveiro Formation was deposited inalluvial fans, including mud flow beds, lakes and sinuous rivers. The Aveiro Formation was depositedin a flat region with low hydrodynamics channels, with the formation of a barrier island-tidal system.The reconstruction of this sedimentary basin may be difficult due to its complex architecture. This workaims a methodology to be used in the reconstruction of Cretaceous sedimentary environments of theLusitanian basin, through the establishment of geochemical patterns of different size fractions of thosedeposits. Chemical analysis was performed by instrumental neutron activation analysis (INAA), and themineralogical composition obtained by X-ray diffractometry (XRD). The whole rock and different sizefractions (� ≥ 125 �m, 63–125 �m, 20–63 �m, 2–20 �m and � < 2 �m) of selected samples were studiedaiming the rare earth elements (REE) and other trace elements distribution and its correlation with thegrain size and mineralogy.

The results obtained for the studied Cretaceous sediments showed that REE patterns and other traceelements distribution in the different size fractions may be used as a tool to differentiate deposits withinand between sedimentary formations. Within the Taveiro Formation, REE are concentrated in the siltfractions (20–63 �m and 2–20 �m) of the Reveles deposit, and in the clay size fraction of S. Pedro deposit,which is richer in kaolinite. The 1st transition elements, particularly Zn, are correlated with the presence ofsmectite in the clay fraction of Reveles deposit. In the sand and silt size fractions (>2 �m) of samples fromTaveiro Formation correlations were found between: Ga and 1st transition elements, and phyllosilicates;Cs and mica; and Rb and Ba, and K–feldspars.

The Bustos deposit (Aveiro Formation) samples are very fine-grained and with a high proportion of the

fine silt fraction where REE are concentrated, especially the heavy ones. Incorporation of MREE, Co andU in carbonates of the coarser fraction appears to occur. The abundances of the 1st transition elements,Ga and As, are correlated with phyllosilicates.

Significant differences were found in the trace elements patterns of the various analysed size fractionsof the Lusitanian basin of Cretaceous sediments, between and even within formations, which can be used

oach

as a methodological appr

. Introduction

The natural occurrence of the rare earth elements (REE), as wells other trace elements in sediments depends on numerous fac-

∗ Corresponding author at: Instituto Tecnológico e Nuclear/GeoBioTec, Estradaacional 10, 2686-953 Sacavém, Portugal. Tel.: +351 219946169;

ax: +351 219946185.E-mail addresses: rmarques@itn.pt (R. Marques), iprudenc@itn.pt

M.I. Prudêncio), isadias@itn.pt (M.I. Dias), frocha@geo.ua.pt (F. Rocha).

009-2819/$ – see front matter © 2011 Elsevier GmbH. All rights reserved.oi:10.1016/j.chemer.2011.02.002

for a fine paleogeographic reconstruction.© 2011 Elsevier GmbH. All rights reserved.

tors (Kimoto et al., 2006; Compton et al., 2003; Yang et al., 2008).Sediments originate from the chemical and physical weatheringof rocks and minerals, and soils upstream, and transported by theriver water. Flow rates decline in lowland areas where particles set-tle along the river banks and on the bed of the river, and finally mostof the transported materials are deposited in the estuary and coastalzone (ocean floor). Along with other trace elements including REE,

Sc and Th have been considered the most immobile elements duringweathering, transportation, deposition and diagenetic processes(Cullers et al., 1997). Numerous works have been made based onchemical and mineralogical composition of the whole rock of shale

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38 R. Marques et al. / Chemi

nd sandstones, in order to understand provenance and tectonicnvironment (Cox et al., 1995; Cullers and Berendsen, 1998; Cullers,002; Wronkiewicz and Condie, 1990).

The break-up of Pangea developed a complex NNE-oriented sys-em of graben structures in the western margin of Iberia, knowns the Lusitanian basin (Dinis et al., 2008; Azeredo et al., 1998;roenca Cunha and Pena dos Reis, 1995). The western Portugaln-shore Cretaceous sedimentary record is dominated by siliciclas-ics and comprises fluvial and deltaic coastal marine siliciclasticystems, as well as extensive deposits of shallow marine carbon-te platforms, both open and rimmed. The Cretaceous depositsf the Portuguese western margin reflect two main phases: (1)he first phase (Berriasian–Cenomanian) corresponds to the infillf the Lusitanian basin during the late rifting stage, with theepocentre located on the Lisbon peninsula; and (2) the secondhase, with a relocation of the depocentre to the northern sec-or. The post-Cenomanian stratigraphic record is characterized bylow subsidence rate and is dominated by fluvial deposits with

ccasional marine intercalations. The upper Campanian and Maas-richtian deposits of the western Portuguese Cretaceous mirror thend of seafloor spreading in the Bay of Biscay, and the start of incip-ent compression between Iberia and Eurasia, as well as with Africa,uring the mid-Campanian (Dinis et al., 2008).

Several studies have been carried out in Upper Cretaceous lev-ls from Taveiro and Aveiro regions (western-central Portugal),ontributing to a more detailed characterization of different clayeposits, particularly the mineralogical and chemical composi-ion and technological properties of clay deposits. These studiesimed different applications of potential raw materials in ceramicsndustries and in barriers in waste landfills, as well as the under-tanding of sedimentary processes and geotechnical behaviour oflays (Prudêncio et al., 1989; Rocha, 1993; Rocha and Gomes, 1995;alhano et al., 1999; Santos, 1998; Santos et al., 2000; Coroado,000).

Concerning the paleoreconstruction of the overall sedimen-ation phenomena, some problems remained to solve in theusitanian basin by using geochemical patterns of the whole sam-le (Rocha, 1993). In this way, a contribution for the establishmentf a complementary methodology to obtain a more detailed stratig-aphy for the reconstruction of different sectors of the basin is theajor goal of the present paper by studying different size fractions.

even samples of clayey levels of two sedimentary formations ofhe northern sector of the Lusitanian basin (“Argilas de Taveiro” andArgilas de Aveiro” Formations) were selected to make a detailedtudy of trace elements (REE included) in the whole sample andheir distribution in the respective different size fractions. A cor-elation study with mineralogy is also done. The size fractionstudied were: � ≥ 125 �m, 63–125 �m, 20–63 �m, 2–20 �m and< 2 �m. The chemical analysis was performed by instrumentaleutron activation analysis (INAA) and the mineralogical compo-ition was obtained by X-ray diffraction (XRD). It should be notedhat a sub-fractionation of the silt fraction was performed, whichas been rarely done even though these fractions can be a tool tonderstand relations between primary and secondary minerals insoil (Hardy and Cornu, 2006).

Previous works using nuclear methods have been done forhe study of chemical contents distribution in sediments fromestern-central Portugal, particularly the correlation between

race elements in the clay fraction and the clay minerals presentPrudêncio et al., 1989; Marques, 2007). The results obtained so faroint to: (1) an enrichment of 1st transition elements, particularlyinc and gallium in samples rich in smectite; (2) high rubidium and

esium contents when illite dominates; and (3) higher contents ofEE when kaolinite is the dominant mineral (Marques, 2007).

Thus, the main objectives of the present paper are: (a) the estab-ishment of geochemical patterns of trace elements in different size

rde 71 (2011) 337–347

fractions of Campanian–Maastrichtian deposits from Taveiro andAveiro Formations (western central Portugal); and (b) the distribu-tion of REE and other trace elements and its correlation with themineralogy. A contribution for the establishment of a methodologyfor the paleoreconstruction of sedimentary basins is a major goal,which will be particularly useful in the northern sector of the UpperCretaceous deposits of the Portuguese western margin.

2. Study area

2.1. Campanian–Maastrichtian deposits

The Taveiro Formation includes a sequence comprising mostlyyellowish quartz sandstone and reddish and brown lutites withnodular calcareous crusts. The interfingering coarse clastics andlutitic facies can be interpreted as deposited in alluvial fans, includ-ing frequent mud flow beds, lakes, and highly sinuous rivers.This sequence displays a general fining upward trend, althoughthe architecture can be rather complex (Dinis et al., 2008). Con-cerning clay minerals, associations of kaolinite and illite, andsmectite, kaolinite and illite were found in the clay fraction(Marques, 2007).

A regression caused the deposition of the “Argilas de Aveiro”Formation, which is composed of marly–sandy clays and resultedfrom intensive and rapid weathering and erosion that affectedrejuvenated continental areas in a temperate climate. Sedimentswere deposited in a flat region with channels of fresh to brack-ish waters (low hydrodynamics). A barrier island-tidal flat systemwas developed in the region, with a depositional environmentwith three main domains: (1) a central-east, supra-tidal area withanoxic episodes, characterized by clayey–sandy sediments contain-ing the association illite + kaolinite, with pyrite in some layers; (2)a central-west area of lagoonal character with manly illite-richsediments deposited on a tidal flat; and (3) a meridional mar-gin represented by clayey smectite-rich sediments. The “Argilas deAveiro” Formation is characterized by a high illite content showing,as a rule, highly degraded structure and irregular interstratifica-tions (Rocha, 1993).

3. Materials and methods

Seven clay samples collected in Upper Cretaceous levels inTaveiro (Reveles and S. Pedro) and Aveiro (Bustos) Formations(Fig. 1) were studied: (a) Taveiro – three samples from theReveles deposit (RVL-50, RVL-51 and RVL-52) (8◦30′28.1′′W and40◦11′7.7′′N); two samples from S. Pedro (SP-50 and SP-51)(8◦30′44.4′′W and 40◦10′24.4′′N); and (b) Aveiro – two samplesfrom the Bustos deposit (BST-51 and BST-52) (8◦37′4.5′′W and40◦30′39.2′′N). Location sites for sampling where chose avoidingweathering features and contamination evidence. For each sample,2 kg of material was collected and sieved (<2 mm).

In the Reveles deposit three samples were collected in the moreargillaceous levels in the profile: from the bottom towards the topRVL-50, RVL-51 and RVL-52. In the S. Pedro deposit two sampleswere selected according to the granulometry: SP-50 and SP-51were also collected in the most argillaceous areas, being the sam-ple SP-51 collected above the SP-50. Concerning the Bustos deposit,two samples were collected in an active quarry, from the bottomtowards the top the sample BST-51 and BST-52. More details onsampling are given in Marques (2007).

Five size fractions of each sample (� ≥ 125 �m, 63–125 �m,

20–63 �m, 2–20 �m and � < 2 �m) were obtained by: (a) wetsieving for the sand fractions (� ≥ 125 �m, 63–125 �m) and (b) sed-imentation for the silt and clay fractions (20–63 �m, 2–20 �m and� < 2 �m), according to Stokes law (Moore and Reynolds, 1997).

R. Marques et al. / Chemie der Erde 71 (2011) 337–347 339

in TavA

Am

Pp2a(mSta

pc((tb

Fig. 1. Sample locationdapted from Santos et al. (2000).

total of 40 samples were grounded and homogenized in agateortars for mineralogical and chemical analyses.The mineralogical analysis was performed by XRD, using a

hilips diffractometer, Pro-Analytical, with Cu K� radiation, forowders of non-oriented samples aggregates, scanned from 2 to 70◦

� and a step size of 1◦ 2�/min. The minerals identification was doneccording to Brindley and Brown (1980) and Moore and Reynolds1997). Mineral proportions in the different size fractions were esti-

ated by semi-quantification, based on peak areas according tochultz (1964) and Rocha (1993). Peak areas of the specific reflec-ions were calculated and weighted by empirical estimated factorsccording to Galhano et al. (1999) and Oliveira et al. (2002).

The diagnostic peaks used and the corresponding reflectionowers (in parenthesis) were the following: quartz – 3.35 A (2),alcite – 3.03 A (1), alkali feldspar – 3.24 A (1), plagioclase – 3.18 A

1), mica – 10 A (0.5), phyllosilicates – 4.45 A (0.1), hematite – 2.68 A1.3) and goethite – 4.18 A (1.3). Given the uncertainties involved inhe semi-quantification method, the results obtained should onlye taken as rough estimates of mineral percentages.

eiro and Aveiro region.

The concentration of several chemical elements, such as Sc,Cr, Co, Zn, Ga, As, Br, Rb, Zr, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb,Yb, Lu, Hf, Ta, W, Th and U in all samples were determined byINAA, with a relative precision and accuracy of less than 5%, andoccasionally less than 10%. Two reference materials, namely soilsGSS-4 and GSS-5 from the Institute of Geophysical and Geochemi-cal Prospecting (IGGE) were used as standards. The reference valueswere taken from data tabulated by Govindaraju (1994). Irradia-tions were performed in the core grid of the Portuguese ResearchReactor, in Sacavém, at a thermal flux of 3.34 × 1012 n cm−2 s−1;�epi/�th = 1.4%; �th/�fast = 14.14. Two �-ray spectrometers wereused: (1) one consisting of a 150 cm3 coaxial Ge detector connectedthrough a Canberra 2020 amplifier to an Accuspec B (Canberra)multichannel analyser. This system had a FWHM of 1.9 keV at1.33 MeV; and (2) the other consisting of a low energy photon

detector (LEPD) connected through a Canberra 2020 amplifier toan Accuspec B (Canberra) multichannel analyser. This system hada FWHM of 300 eV at 5.9 keV and of 550 eV at 122 keV. Correctionsfor the spectral interference from U fission products in the deter-

340 R. Marques et al. / Chemie der Erde 71 (2011) 337–347

Table 1Grain size distribution (%) of samples from Reveles and S. Pedro deposits (Taveiro Formation) and Bustos deposit (Aveiro Formation), obtained by sieving and sedimentation.

≥125 �m 63–125 �m 20–63 �m 2–20 �m <2 �m

Taveiro RVL-50 35 29 5 15 16RVL-51 25 43 7 13 12RVL-52 4 17 17 34 28SP-50 3 8 14 35 40SP-51 5 9 15 38 33

m(m

tttaltts

TSd

Aveiro BST-51 0 2BST-52 0 1

ination of Ba, REE and Zr were done according to Gouveia et al.1987) and Martinho et al. (1991). More details of the analytical

ethod were published elsewhere (Prudêncio et al., 1986).The joining (tree clustering) using the absolute concentration of

he chemical elements as variables was employed using the Sta-istica program (Statistica, 2008). The amalgamation was done byhe unweighted pair-group average also referred as UPGMA. In thismalgamation method, the distance between two clusters is calcu-

ated as the average distance between all pairs of objects in thewo different clusters. The similarity coefficients calculated washe Pearson correlation coefficient to evaluate correlation betweenamples and variables.

able 2emi-quantitative mineralogical composition (%) obtained by XRD of the different size fraceposit (Aveiro Formation).

Quartz Phyllosilicate K–feldspar

RVL-50 whole rock 58 19 22RVL-50 >125 74 25RVL-50 63–125 64 9 25RVL-50 20–63 54 37 7RVL-50 2–20 15 79 2RVL-50 <2 10 74

RVL-51 whole rock 49 23 26RVL-51 >125 84 14RVL-51 63–125 81 12 5RVL-51 20–63 33 48 9RVL-51 2–20 11 82RVL-51 <2 4 85

RVL-52 whole rock 48 46 3RVL-52 >125 64 7 25RVL-52 63–125 86 6 6RVL-52 20–63 72 22 2RVL-52 2–20 35 59RVL-52 <2 6 86

SP-50 whole rock 76 18 1SP-50 >125 99 1SP-50 63–125 96 3SP-50 20–63 86 11 1SP-50 2–20 70 20 1SP-50 <2 10 51

SP-51 whole rock 63 31 1SP-50 >125 98SP-50 63–125 98 1SP-50 20–63 87 9 1SP-51 2–20 63 26 1SP-51 <2 12 56 1

BST-51 whole rock 21 72 1BST-51 >63 65 8 25BST-51 20–63 83 10 4BST-51 2–20 47 32 2BST-51 <2 4 91

BST-52 whole rock 16 76 3BST-52 >63 47 7 38BST-52 20–63 64 26 6BST-52 2–20 48 30 3BST-52 <2 7 76

1 22 753 22 74

4. Results

4.1. Grain size distribution

The proportions of the different grain size fractions of thestudied samples are presented in Table 1. Significant differenceswere found between and/or within deposits of Taveiro and Aveiro,namely:

(a) Taveiro Formation – high proportions of sand fractions(� ≥ 125 �m and 63–125 �m) and small proportions of silt frac-tion, particularly in the Reveles case.

tions in samples from Reveles and S. Pedro deposits (Taveiro Formation) and Bustos

Calcite Hematite Goethite Plagioclase Mica

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1 316

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R. Marques et al. / Chemie der Erde 71 (2011) 337–347 341

F et al.,F

(

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ig. 2. REE distribution patterns in different size fractions relative to PAAS (Haskinormation).

b) Aveiro Formation – very fine sediments, with high proportionsof fine silt (2–20 �m) and clay fractions.

.2. Mineralogical composition

The results obtained by the semi-quantification of minerals

etected by XRD in the different size fractions are given in Table 2.

(a) Taveiro Formation – quartz is always present and domi-nates in the fractions � > 2 �m, except in the fine silt fraction

1971) and the respective whole rock, of samples from the Reveles deposit (Taveiro

of Reveles samples, where higher proportions of phyllosil-icates were found. Micas are also detected in all studiedfractions from Reveles, and alkali feldspars occur in sig-nificant amounts in the coarser fractions of Reveles. In S.Pedro deposit samples the mineralogical association is simi-lar to Reveles deposit, but traces of iron oxides (hematite andgoethite) also occur. Concerning clay minerals, kaolinite ≥ illite

are present in the � < 2 �m fraction of S. Pedro. Besides these,smectite was also found in significant amounts in the Reve-les deposit (smectite > illite � kaolinite; except RVL-52 whereillite > smectite ∼ kaolinite) (Marques, 2007).

342 R. Marques et al. / Chemie der Erde 71 (2011) 337–347

Fig. 3. REE distribution patterns in different size fractions relative to PAAS (Haskin et al., 1971) and the respective whole rock, of samples from the S. Pedro deposit (TaveiroFormation).

Fig. 4. REE distribution patterns in different size fractions relative to PAAS (Haskin et al., 1971) and the respective whole rock, of samples from the Bustos deposit (AveiroFormation).

R. Marques et al. / Chemie der Erde 71 (2011) 337–347 343

Ft

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contents in the finer fractions, particularly in the � < 2 �m frac-

ig. 5. Trace elements distribution in different size fractions relative to the respec-ive whole rock, of samples from the Reveles deposit (Taveiro Formation).

b) Aveiro Formation – quartz is the dominant mineral in thecoarser fractions, particularly the 20–63 �m fraction. Phyl-losilicates, alkali feldspars and micas are also present. Calcitewas also detected in all size fractions of sample BST-52.Illite > kaolinite occur in the clay fraction; small amounts ofmixed layer illite/smectite were also found (Marques, 2007).

.3. Chemical composition

.3.1. Rare earth elementsThe REE patterns of the different size fractions of the studied

layey samples from Upper Cretaceous deposits relative to PAAS

Fig. 6. Trace elements distribution in different size fractions relative to the respec-tive whole rock, of samples from the S. Pedro deposit (Taveiro Formation).

(Haskin et al., 1971) and to the respective whole rock are presentedin Figs. 2–4.

4.3.1.1. Taveiro Formation.

– Reveles deposit: the normalization to PAAS enhances the differ-ences among the REE patterns in the different size fractionsstudied, particularly the Eu distribution (Fig. 2). In general thiselement is enriched in all size fractions, except in the 20–63 �mfraction (the one with the higher � REE) where a significant neg-ative Eu anomaly and also a higher heavy REE (HREE)/light REE(LREE) ratio exist. In samples RVL-50 and RVL-51 the � ≥ 125 �mfractions present the lower REE contents and a significant posi-tive Eu anomaly. The 63–125 �m fraction of sample RVL-52 is theone with the lower REE contents. The REE patterns of differentsize fractions relative to whole rock present higher contents ofthese elements in the silt and clay fractions, especially in RVL-50. As observed in the normalization to PAAS, the silt fraction20–63 �m is the only presenting a negative Eu anomaly.

– S. Pedro deposit: the REE distribution in the different size fractionsof both samples relative to PAAS is similar (Fig. 3). The sand frac-tions differ clearly from silt and clay fractions due to higher REE

tion. When normalization is done relatively to the whole rock,the differentiation between the coarser and finer fractions is alsoenhanced in S. Pedro deposit. The clay size fraction is the mostenriched in all REE.

344R

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Table 3Chemical contents of trace elements (�g/g) obtained by INAA for different size fractions of samples from Taveiro and Aveiro deposits.

Sc Cr Co Zn Ga As Br Rb Zr Sb Cs Ba La Ce Nd Sm Eu Tb Yb Lu Hf Ta W Th U

RVL-50 T 4.71 30.1 10.1 23.8 6.89 11 2.04 95.7 208 0.42 3.74 223 23.9 47.8 24.6 4.51 0.832 0.638 2.33 0.325 6.41 0.912 1.35 7.49 2.46RVL-50 >125 �m 1.34 10 12.1 13.8 3.58 0.565 n.d. 103 35.4 0.278 2.8 236 8.78 18.9 7.89 1.48 0.364 0.114 0.512 0.062 1.09 0.23 0.453 2.43 0.768RVL-50 63–125 �m 2.98 21.5 5.1 20.7 4.92 0.752 n.d. 89.7 101 0.477 3.03 217 14.3 28.0 13.7 2.54 0.532 0.405 1.59 0.23 3.51 0.867 1.22 5.54 1.9RVL-50 20–63 �m 8.28 49.1 10.7 63.9 12.2 1.61 0.293 101 430 0.634 4.93 218 44.0 88.4 43.6 8.18 1.39 1.09 4.41 0.553 14.2 1.98 2.28 14.4 4.5RVL-50 2–20 �m 11.5 67.7 14.4 73.4 19.2 1.6 0.778 121 152 0.453 6.56 205 32.0 63.3 31.7 6.01 1.27 0.755 2.61 0.346 4.28 1.22 1.61 9.28 2.42RVL-50 <2 �m 12.5 82.6 11 105 21.5 1.87 1.32 111 90.5 0.445 6.54 176 22.9 46.8 23.3 4.74 1.17 0.593 1.68 0.218 2.62 0.849 1.62 7.68 2.03

RVL-51 T 4.03 26.8 4.18 21.9 8.11 2.09 n.d. 94.1 201 0.544 3.47 216 22.1 42.1 20.9 3.76 0.642 0.496 1.95 0.282 6.69 0.99 1.37 7.52 1.57RVL-51 >125 �m 1.85 13.7 3.17 13.6 5.01 1.46 n.d. 132 40.3 0.459 3.78 354 8.4 18.2 7.71 1.33 0.37 0.175 0.71 0.109 1.33 0.29 0.739 2.54 0.521RVL-51 63–125 �m 2.59 19.5 2.57 19.8 4.82 1.54 n.d. 86.8 92.2 0.472 2.86 232 12.8 23.8 11.3 2.04 0.445 0.268 1.08 0.138 2.76 0.664 0.811 4.01 0.797RVL-51 20–63 �m 7.36 49.5 7.52 68.3 11.6 2.88 n.d. 84.7 684 0.716 3.95 200 52.5 105 52.3 9.43 1.34 1.36 5.47 0.694 22.1 2.16 2.59 19 3.39RVL-51 2–20 �m 8.76 54.3 9.15 64.1 17.6 3.5 0.372 81.6 105 0.555 4.63 153 22.1 42.9 21.3 3.98 0.91 0.524 1.78 0.077 3.28 1.01 1.35 7.31 0.776RVL-51 <2 �m 9.21 59.3 8.83 74.2 12.2 4.29 1.73 76.8 66.3 0.476 4.39 139 15.9 32.1 12.5 3.03 0.877 0.391 1.1 0.166 1.79 0.79 1.11 6.19 0.776

RVL-52 T 8.39 52.7 10.7 47.7 13 7.04 n.d. 103 321 1.12 5.53 354 38.8 79.2 37.4 6.85 1.18 0.897 3.17 0.477 10.4 1.64 2.48 12.2 2.37RVL-52 >125 �m 4.57 28.8 12.4 28.6 9.02 7.29 0.204 117 112 1.18 4.54 686 19.5 63.5 18.3 3.38 0.746 0.499 1.67 0.229 3.61 0.771 1.86 6.62 1.1RVL-52 63–125 �m 2.32 16.9 3.15 16.5 4.29 2.35 n.d. 99.0 67.1 0.624 3.25 311 11.3 23.7 10.1 1.81 0.384 0.238 1.01 0.152 2.2 0.667 1.1 4.32 0.661RVL-52 20–63 �m 5.83 38.6 7.28 32.2 4.88 4.32 0.263 76.6 444 0.988 3.87 216 40.7 85.9 41.0 7.37 1.15 1.06 4.12 0.575 14.5 2.04 2.27 13.9 2.87RVL-52 2–20 �m 12.8 74.6 14.8 61.1 13.2 9.19 0.303 133 157 1.39 8.38 280 38.3 76.4 39.4 6.83 1.34 0.914 3.15 0.428 5.7 1.68 2.74 11.9 1.87RVL-52 <2 �m 13.1 79.0 11.6 63.8 14.1 12 0.8 122 112 1.46 7.63 182 22.6 47.8 25.8 4.28 1.01 0.559 1.58 0.233 2.82 1.09 2.03 8.85 1.2

SP-50 T 10.9 68.9 3.85 37.3 16 15.1 2.86 78.7 198 2.16 6.3 233 35.6 66.3 34.8 6.67 1.28 0.889 3.26 0.46 7.39 1.55 2.57 10.1 3.37SP-50 >125 �m 1.9 15.7 0.819 13.2 2.17 4.07 1.25 13.5 36.5 0.767 0.988 48.9 7.65 13.8 7.41 1.4 0.252 0.205 0.793 0.108 1.65 0.371 0.715 2.37 1.06SP-50 63–125 �m 2.39 17.2 1.07 16.5 2.55 3.28 0.451 20.9 71.8 0.803 1.34 60.6 10.4 19.5 10.5 1.98 0.37 0.251 1.01 0.138 2.18 0.764 1.25 3.43 1.03SP-50 20–63 �m 4.65 30.4 2.89 22.6 2.7 5.24 0.518 30.6 348 1.38 1.97 77.1 32.8 67.7 36.9 6.03 1.02 0.834 3.4 0.496 11.6 1.61 2.32 9.59 2.45SP-50 2–20 �m 10.4 60.1 2.91 30.4 8.12 9.37 1.33 71.5 170 1.77 5.47 209 33.3 66.7 34.5 6.18 1.26 0.918 3.42 0.46 5.03 1.35 2.38 8.66 2.46SP-50 <2 �m 24.7 179 8.3 72.5 25.4 43.9 8.21 189 151 4.67 17 481 39.3 80.4 38.9 8.83 2.07 1.19 3.41 0.484 5.17 1.73 3.94 14.5 6.28

SP-51 T 10.4 61.7 2.33 29.7 13.5 12.7 5.21 76.9 231 1.69 7.01 231 42.3 76.9 41.7 7.82 1.55 1.05 3.59 0.504 7.93 1.63 2.83 11.7 3.41SP-51 >125 �m 2.05 17.7 0.832 11.6 2.57 6.28 2.29 16.7 50.0 0.627 1.26 49.2 10.3 19.6 13.0 2.66 0.5 0.322 1.1 0.144 1.7 0.292 0.599 2.99 1.55SP-51 63–125 �m 2.53 18.6 0.87 12.1 2.99 3.95 1.24 21.2 62.5 0.776 1.43 73.4 13.1 23.3 12.8 2.35 0.42 0.305 1.11 0.142 2.25 0.658 1.31 4.47 1.08SP-51 20–63 �m 4.31 24.9 1.8 14.6 2.67 3.66 0.958 23.8 336 1.32 1.61 54.4 33.4 68.0 37.4 6.23 1.04 0.848 3.62 0.501 11.5 1.61 2.15 10.1 2.56SP-51 2–20 �m 8.01 47.7 1.51 17.8 7.25 8.58 2.89 55.8 150 1.3 44.4 162 30.9 59.8 32.2 5.83 1.16 0.886 3.04 0.406 4.48 1.29 2.11 8.27 2.05SP-51 <2 �m 22.8 146 4.23 44.2 23.1 29 12.7 198 182 2.92 19.7 502 61 118 71.4 12.5 2.82 1.63 4.24 0.651 4.85 1.92 4.39 16.9 5.13

BST-51 T 13.6 70.5 13.5 59.6 25 19.4 0.884 236 119 0.994 21.8 245 37.5 69.3 31.3 5.8 0.986 0.726 2.67 0.36 4.89 2.72 5.47 15.7 3.18BST-51 63–125 �m 1.94 27.2 3.74 14 4.97 29.7 n.d. 188 28.7 0.289 10.2 447 10.4 23.6 14.1 2.96 0.679 0.306 0.762 0.086 0.868 0.583 1.46 7.89 4.20BST-51 20–63 �m 3.62 19.5 3.67 23.8 6.49 10.1 n.d. 131 264 0.418 7.49 219 35.4 68.9 33.3 5.97 0.9 0.79 3.45 0.474 9.29 2.22 3.3 15.2 3.05BST-51 2–20 �m 12.7 65.0 12.0 67.0 18.2 11.1 n.d. 209 274 0.861 15.3 391 55.5 105 50.7 8.83 1.54 1.29 4.97 0.667 7.97 3.3 5.26 18.4 3.26BST-51 <2 �m 15.2 80.7 15.3 60.2 19 19.2 0.508 267 102 0.98 26.7 165 33.5 59.1 28.3 4.74 0.849 0.589 2.02 0.258 3.53 2.67 5.72 13.9 2.80

BST-52 T 12.4 63.1 13.5 46.9 20.7 5.88 1.83 232 130 0.707 21.9 189 39 72.9 36.6 6.92 1.14 0.895 2.83 0.393 4.75 2.55 4.88 15.8 4.95BST-52 63–125 �m 1.36 30.8 12.6 25.2 3.39 17.9 0.573 170 51.0 0.241 9.61 238 27.5 80.7 64.2 13.9 2.74 1.84 2.51 0.199 0.66 0.401 0.714 23.5 13.0BST-52 20–63 �m 5.94 31.6 8.01 32.9 12.2 5.72 n.d. 178 230 0.478 12.9 177 37.3 72.7 36.6 7.14 1.14 0.967 3.12 0.418 8.26 2.44 3.76 18.0 4.05BST-52 2–20 �m 12.3 61.9 12.4 57.4 21.4 4.19 n.d. 235 207 0.697 20 277 53 96.4 47.5 9.07 1.47 1.32 4.3 0.579 6.94 3.1 5.11 19.8 4.18BST-52 <2 �m 14.5 74.8 15.9 66 29.5 6.3 0.455 273 123 0.712 26.8 183 36.6 65.1 31.6 6.01 1.07 0.806 2.31 0.319 3.58 2.61 5.63 14.9 3.94

e der Erde 71 (2011) 337–347 345

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R. Marques et al. / Chemi

.3.1.2. Aveiro Formation.

Bustos deposit: the two samples from Bustos present widelydivergent behaviours (when compared to the Taveiro deposits),especially in the sand fraction (� ≥ 63 �m), as shown in Fig. 4.This fraction present a hat-shape REE pattern, particularly in thesample BST-52 where the higher contents of middle REE (MREE)are found. A similar tendency in the REE pattern is observed inthe � ≥ 63 �m fraction of BST-51 indicating a similar distributionof the mineral phases, but with smaller contents of REE.

.3.2. Trace elements distributionThe chemical contents of trace elements (REE included for com-

arative reasons) in the different grain size fractions relative to theespective whole rock of Taveiro samples are plotted in Figs. 5 and 6Table 3).

.3.2.1. Taveiro Formation.

Reveles deposit: the silt and clay fractions (� < 63 �m) presentenrichment of several trace elements relative to the wholerock (Fig. 5), particularly for samples RVL-50 and RVL-51. Thisbehaviour is more evident for the 1st transition elements, Ga, Asand REE. The silt fraction (20–63 �m) of the three studied sam-ples present similar distribution patterns concerning Zr, Hf andREE, Ta, Th and U.S. Pedro deposit: in general, the two samples studied presentsimilar trace elements patterns. The clay sized fraction is theonly enriched in all the studied elements (Fig. 6), but Zr andHf, which are more concentrated in the 20–63 �m fraction. Itshould be noted that Cs is concentrated in the clay fraction ofboth samples. Concerning the other studied fractions, the sandyones (� ≥ 125 �m and 63–125 �m) are the most depleted in alltrace elements relative to the whole rock, especially REE, Zr, Hf,Ta, W, and Th.

.3.2.2. Aveiro Formation.

Bustos deposit: geochemical patterns of both samples (Fig. 7)show that, in the silt and clay fractions there are no significantdifferences in trace elements contents relative to the respectivewhole rock. In the fine silt fraction (2–20 �m) a positive corre-lation is established between REE and Zr–Hf. The sand fraction(� ≥ 63 �m) is depleted in almost all the studied elements, exceptin As, Ba, Th and U. In sample BST-52, besides these elements,MREE are also enriched as referred above. In the coarser fractionthere is a significant depletion of 1st transition elements and Ga.

. Discussion and conclusions

The results obtained for trace elements contents and geo-hemical patterns of the different size fractions studied in bothaveiro and Aveiro Formations (belonging to the Upper Cretaceouseposits, Portuguese western margin) show a diverse distribu-ion of trace elements, correlated with the grain size and the

ineralogical composition within and between deposits. The sub-ractionation of the silt fraction revealed to be a useful tooln differentiating stratigraphic levels of the studied Cretaceouseposits.

Within the Taveiro Formation, in the finer-grained samples (SPnd RVL-52) the REE patterns of the two silt fractions (20–63 �m

nd 2–20 �m) do not differ significantly. However in the SP sam-les, REE are more concentrated in the clay size fraction, richer inaolinite. The coarser fractions of the Reveles deposit (RVL-50 andVL-51 samples) present a significant positive Eu anomaly, which

Fig. 7. Trace elements distribution in different size fractions relative to the respec-tive whole rock, of samples from the Bustos deposit (Aveiro Formation).

is in agreement with the higher feldspars content (see Table 2 andFig. 2). REE are more concentrated in the silt fraction 20–63 �m inall samples, particularly in the coarser ones. In S. Pedro deposit,REE are most concentrated in the clay size fraction relative tothe respective whole rock, especially the LREE and MREE, whichcan be explained by the preferential incorporation of these ele-ments in kaolinite, the dominant clay mineral in these samples. Thecorrelation between REE and kaolinite in the clay fraction of Cre-taceous sediments of the Lusitanian basin has already been found(Prudêncio et al., 1989; Marques, 2007).

The Aveiro Formation samples are clearly differentiated fromTaveiro using REE patterns. The studied samples from Bustosdeposit are very fine, and with a high proportion of the fine silt frac-tion (2–20 �m), where REE are concentrated, especially the heavyones. The coarser fraction (>63 �m) presents a different REE pat-tern with hat-shape, where MREE can present the highest contentsin BST-52 sample (see Fig. 4), probably related with the presence ofcarbonates (see Table 2), as already suggested by Prudêncio (1993)and Compton et al. (2003).

Besides the REE, the 1st transition elements, Ga and As, areenriched relative to the whole rock in the silt and clay fractionsin rocks from the Reveles deposit from the Taveiro Formation.The significant enrichment in Zr and Hf found in the silt frac-tion (20–63 �m), is certainly related to the presence of zircon. In

the same fraction, similar patterns for REE (particularly the heavyones), Ta, Th, and U were also found, and probably related withzircon, in agreement with the higher HREE/LREE ratios, when com-

346 R. Marques et al. / Chemie der Erde 71 (2011) 337–347

F nts ant

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Zpciif(

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ig. 8. Phenogram resulting from the tree clustering using the trace elements contehe Taveiro Formation.

ared with the chemical patterns of the other size fractions. In thene silt fraction (2–20 �m), which is the second one with high REEontents when compared to the whole rock, Zr and Hf are depleted,uggesting the incorporation of REE in other minerals such as phyl-osilicates. The coarser fractions of the Reveles samples present themaller contents of the studied elements relative to the whole rockrobably due to high quartz proportions especially in the samplesVL-50 and RVL-51 (see Table 2). Exceptions were found for Rbnd Ba that may be incorporated in feldspars. It should be notedhat the fine silt and clay fractions of the three samples presentigher contents of Zn and Ga that can be associated to phyllosili-ates. Smectite may explain the enrichment of this sample in thest transition elements, especially Zn (Marques, 2007).

The clay size fraction of S. Pedro deposit presents a depletion inr and Hf, which are more concentrated in the 20–63 �m fraction,ointing to the presence of zircon in this fraction. Cesium is moreoncentrated in the clay fraction of both samples, probably due tots incorporation in micas. In fact, the absorption/adsorption of Cs+

n this mineral has been widely studied for several applications,or instance on radioisotopes retention in sediments rich in micasZachara et al., 2002).

The tree clustering analysis of the different size fractions� > 2 �m) of samples from Taveiro Formation, using trace elementsontents and minerals proportions as variables, is shown in Fig. 8.he correlation between phyllosilicates and Ga and 1st transitionlements is evident, as well as the mica–Cs association. Also theorrelation between the contents of Rb and Ba with K–feldspars ishown in the tree-cluster (Fig. 8).

In rocks of the Aveiro Formation the silt and clay fractions of theustos samples present similar geochemical patterns (see Fig. 7),xcept for 1st transition elements, Ga and As, which are presentn higher concentrations in sample BST-52, most probably due to

he higher phyllosilicate content of this sample (see Table 2). Inhe silt fractions Zr and Hf present higher concentrations togetherith HREE, this can be explained by the presence of zircon in this

raction. A tendency for high Co and U contents in the sample richer

d minerals proportions as variables of the sand and silt fractions of sediments from

in carbonates (BST-52) is observed. Incorporation of Co and U incarbonates was already mentioned by some authors (Xu et al., 1996;Cheng et al., 2000; Kelly et al., 2003).

The results obtained in this work showed how trace elementsmay be distributed in the size fractions of Cretaceous sedimentsof the Portuguese western margin in significantly different ways,even within the same formation, certainly reflecting the prove-nance, environmental conditions of deposition and also diageneticalterations. Therefore this methodology appears to be suitable to beapplied to a larger number of samples (spatial and sequential) fromdifferent sectors of the basin in order to obtain a better correlationbetween stratigraphic levels.

Thus trace elements distribution in sediments may varies sig-nificantly with the grain size, depending on the mineralogy andcertainly reflecting provenance area and sedimentary processes. Itshould be noted that sediments from the Lusitanian basin could notbe so clearly differentiated in the past by studying the whole rock.The methodological approach established in this study appears tobe a promising tool to be used in further studies concerning thepaleoreconstruction of the overall sedimentation phenomena, thuscontributing to obtain a more detailed stratigraphy for the recon-struction of different sectors of the Lusitanian basin, as well as ofother similar sedimentary paleoenvironments.

Acknowledgements

Grateful acknowledgements are made to all the staff of the Por-tuguese Research Reactor (RPI) of ITN for their assistance with theneutron irradiations.

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