These rocks exhibit calc-alkaline affinities and may have originated by partial melting of the crust in a post-collision, anorogenic setting. Orthogneisses derived from biotite-bearing leucogranites occur within aprobably cambrian heterogeneous series. Petrological and geochemical features suggest that they might be genetically related to the ordovician vulcanites. Basic sills and volcanoclastic rocks occur intercalated within a mainly pelitic formation in the lower part of the Silurian sequence. The silurian igneous rocks are alkali basalts and may reflect an extensional regime

Gil Ibarguchi, José Ignacio

Navidad, M.

Ortega Cuesta, Luis Ángel

GIL IBARGUCHI, J.I.

NAVIDAD, M.

ORTEGA CUESTA, Luis A.

Revistes CientÃ­fiques de la Universitat de Barcelona

English

Ordovician and Silurian igneous rocks and orthogeneisses in the Catalonian Coastel Ranges

Revistes Catalanes amb Accés Obert

ACTA GEOLOGICA HISPANICA, v. 25 (1990), nV-2,  pigs. 23-29 
PROJECT 276 
Paleozoic of 
the Tethys 
Ordovician and Silurian igneous rocks and orthogneisses in the 
Catalonian Coastal Ranges 
J. I. GIL IBARGUCHI ( I ) ,  M. NAVIDAD L. A. ORTEGA ( I )  
I 
(1) Departamento de Mineralogia-Petrologia, Facultad de Ciencias, Universidad del País Vasco-EHU, Aptdo. 644,48080 Bilbao, Spain 
(2) Departamento de Petrologia y Geoquímica, Facultad de Ciencias Geológicas, Universidad Complutense, 28040 Madrid, Spain 
ABSTRACT 
These rocks exhibit calc-alkaline affinities and may have originated 
by partia1 melting of the crust in a post-collision, anorogenic 
setting. Orthogneisses derived from biotite-bearing leucogranites 
occur within aprobably cambrian heterogeneous series. Petrological 
and geochemical features suggest that they might be genetically 
related to the ordovician vulcanites. Basic sills and volcanoclastic 
rocks occur intercalated within a mainly pelitic formation in the 
lower part of the Silurian sequence. The silurian igneous rocks are 
alkali basalts and may reflect an extensional regime. 
Key words: Pre-hercynianmagmatism. Metavolcanites. Orthogneisses. 
Bulk-rock chemistry. 
RESUMEN 
Las rocas volcBnicas ordovicicas aparecen intercaladas en una 
secuencia arenoso-pelítica de edad Caradoc. Se trata de materiales 
piroclásticos Bcidos con niveles subordinados de riolitas masivas. 
Poseen afinidades calcoalcalinas y se podrian haber formado por 
fusi6n crustal en un contexto anorogénico post-colisional. Los 
ortogneises aparecen en una serie heterogénea probablemente de 
edad cámbrica. Corresponden a leucogranitos biotíticos y presen- 
tan afinidades geoquímicas con las vulcanitas ordovicias, pudiendo 
estar relacionados genéticamente. En la base del Silúrico aparecen 
aparecen sills con composición de basaltos alcalinos y rocas 
volcanoclásticas básicas intercalados en una serie esencialmente 
pelítica que podrían haberse originado en un régimen de distensión 
crustal. 
Palahras clave: Magmatismopre-hercínico. Metavulcanitas. Ortogneises. 
Composición química. 
ORDOVICIAN METAVULCANITES 
Upper Ordovician volcanic rocks, variably affected 
by the Hercynian regional metamorphism, form a 
number of outcrops of different extensions along the 
Catalonian coastal ranges. The main outcrops are 
situated in the Gavarres, Guilleries, Montseny and 
Pedritxes areas (Fig. 1). These rocks occur intercalated 
within the lower part of a mainly greywacke-shale 
sequence of Caradoc age (Meléndez and Chauvel, 
198 1; Villas etal., 1987; Barnolas andGarcia Sansegundo, 
inpress; Julivert et al., 1987). Discontinuous levels of 
metaconglomerates occurring locally at the base of 
this series have been interpreted in comparable sectors 
of the Eastern Pyrenees as a basal discordance of 
Upper Ordovician age (Hartevelt, 1970; Santanach, 
1974; Laumonier, 1988). The Lower Paleozoic materials, 
probably Cambrian age (Laumonier, 1988), which 
crop out underlying this sequence are composed of 1) 
an upper portion of metapelites ('lower heterolithic 
series?, Barnolas and Garcia Sansegundo, in press) 
and 2)  a lower member ('Guilleries series') comprising 
pelitic gneisses, marbles, calc-silicate rocks and 
amphibolites, along with orthogneissic bodies which 
have been genetically correlated with the ordovician 
metavulcanites (Durán et al., 1984). 
The metavulcanites as a whole form a sequence of 
variable thickness defined by an alternance of variably 
metamorphosed pyroclastic and volcanoclastic materials 
, . . .  
e . . . .  
. . . , . . . 
. . . e . .  
e . . .  
EBRO B A S I N  . . . .  
. . . .  
PALEOZOIC ROCKS 
0 IAlNLY NEOGENE GRABEN INFlLLlNGS 
~ ~ , " , " 3 E , ~ ~ l M E N T S  OF 
0 OTHER POST-PALEOZOIC ROCKS 
UNDIFFERENTIATED PALEOZOIC ROCKS 
SlLURlAN VOLCANIC ROCKS 
ORDOVlClAN VOLCANIC AClD ROCKS 
Fjgure 1.-  Geological sketch of the Catalonian Coastal Ranges showing the location of the Ordovician and Silurian igneous rocks and 
orthogneisses. 
with subordinated levels of massive rhyolites. These these studies, with additional data from Durán (1986) 
materials correspond to an explosive volcanism that and Julivert et al. (1987), are summarized herein. 
gave rise to subaereal air-fall deposits and ash-flow 
tuffs (ignimbrites). The amount of sedimentary mate- The pyroclastic rocks correspond to tuffs and cinerites 
rial is highly variable, one of the most conspicuous of dacitic to rhyolitic composition. Relict ignimbritic 
features being the association in some places of volcanic features ('fiame' andresidual flow banding) and structures 
materialswithturbidites. ThissuggeststhattheOrdovician characteristic of subaereal deposits (laminations, 
acid volcanism was not totally subaereal, which accounts, imbrications between tuffs and cinerites, as well as 
in part, for the marked Na-enrichment in most of the gradational structures) can be recognized in these 
samples (see below). A detailed account of the main rocks. The volcanoclastic rocks must be the result of 
petrographic and geochemical features of these rocks phreatomagmatic processes and are characterized by 
rnay be found in Durán et al. (1984) and Navidad and the abundance of volcanic components with lithic 
Barnolas (in press). The most important results from fragments and subvolcanic clasts. The massive materials 
24 
-- - -- -- -- 
16 
12 
o 
s? 
+ 8 -  O 
2 
4 
o 
- Orthogneisses 
a Pedritxes 
14 H Guilleries 
Gavarres 
O Tibidabo - 
a. 
- 
B m  
- I I I I I I I 1 I I I I I I 
41 45 49 53 57 61 65 69 73 77 81 85 89 
Si02 
E'igure 2.- Chemical composition of Ordovlcian (solid squares) and Silurian (open circles) igneous rocks and orthogneisses (open squares) 
from the Catalonian Coastal Ranges. Diagram after Zanettin (1984). Data from Durán et al. (1984), Durán (1986) and Gil Ibarguchi and 
Julivert (1988). 1: picrobasalt, 2: basalt, 3: basaltic andesite, 4: andesite, 5 :  dacite, 6: rhyolite (alkali rhyolite P.I.>l), 7: trachybasalt, 8,9: 
trachyandesite, 10: trachyite (alkali trachyte, P.I.>l), 11: basanite and tephrite, 12: phonotephrite, 13: tephriphonolite, 14: phonolite. 
correspond to levels of metarhyolites with relict igneous reported Rb, Y, Nb contents and other incompatible 
flow textures as well as perlitic and spherulitic structures elements of these magmas arc intermediate between 
resulting from devitrification those of collisional and anorogenic type, which suggests 
The rhyolitic and dacitic character of most ordovician apost-collisional geodynamic setting for this magmatism 
metavulcanites in this area has been established by (cf. Fig. 4). The REE contents (Fig. 5A) are different 
Durán et al. (1984) and Durán (1986) on the basis of from those of typical anorogenic acid magmas, giving 
the major element composition of these rocks (Figure amore fractionatedpattern, with less significant negative 
2). Important post-deposition hydrothermal transformation EU anomaly, although Ce/Yb ratios (2.5-4.72) are 
was responsible for an enrichment in Na, and to a similar to those of A-type granites elsewhere (2.2-5.5, 
lesser extent in Si, of most of the samples analyzed Whalen et al., 1987), the origin of which could be 
(Figure 3). The overall compositions reported by interpreted in terms of the partia1 melting of recycled 
these authors suggest a calc-alkaline affinity for this continental crust. 
volcanism; nevertheless, the scarcity of rocks with 
intermediate composition rather precludes the possibility 
of it being defined as a calc-alkaline series. 
An attempt to characterize this volcanism using ORTHOGNEISSES 
less mobile elements has been carried out by Navidad 
and Barnolas (in press). According to these authors, Orthogneiss bodies are found in the Montseny and 
the Zr, Ti, Nb and Y contents suggest a kind of calc- Guilleries sectors (Fig. 1) in the lowermost part of the 
alkaline magmatism, with a considerable crustal Paleozoic sequence(Duránetal., 1984). Theemplacement 
participation, where only the more acid terms of the of the igneous protoliths tookplace during pre-Hercynian 
sequence (rhyolites-dacites) would be present. The times, since these rocks exhibit the same structural 
25 
p~ 
1 1 
' B  I 
' . 
I 
l i  Orthogneisses x 4 I 
Pedritxes 
- 
Guilleries 
Gavarres 
O Tibidabo 
- 
- 
I L I I A 
Figure 3.- Chemical composition of Ordovician (solid quares) and Silurian (open circles) igneous rocks and orthogneisses (open squares) from 
the CatalonianCoastalRanges. Diagram after Church (1975), 1: Highwoodlava, 2: Cascade lava, B: basalt, A: andesite, D: dacite, R: rhyolite. 
Data from Duran et al. (1984), Durán (1986) and Gil Ibarguchi and Julivert (1988) 
features as the enclosing metasediments which were 
affected by the Hercynian events. 
The orthogneisses form apparently concordant, 
kilometre-size, sheet-like bodies and exhibit sharp 
contacts withtheenclosing Lower Paleozoic metasediments. 
Descriptions of these rocks, together with data on 
major element composition can. be found in Durán et 
al. (1984), Durán (1986) and Navidad and Barnolas (in 
press). Most of the orthogneisses are biotite-bearing 
leucogneisses and often show traces of ductile deformation. 
The orthogneisses are Si- and alkali-rich, aluminous 
metagranites with normative corundum. From their 
trace element composition (cf. Navidad and Barnolas, 
inpress) these rocks are characterized as non-peralkaline 
granitoids from anorogenic domains. The major, trace 
and rare earth element composition of the orthogneisses 
is broadly similar to that of the ordovician metavulcanites 
(Figs. 2,3 and 4A). They are slightly richer in incompatible 
elements and have greater negative EU anomaly than 
the metavulcanites; however, is the REE composition 
of both rock-types markedly different from that of the 
typical A-type granitoids (Fig. 5A). 
Inview of these geochemical similarities andconsidering 
their petrography and field relatioships, most authors 
working in this area have considered that the magmas 
origining the vulcanites and orthogneisses were genetically 
related, although, in the absence of geochronological 
data for the granitoids, this possibility is open to doubt 
(cf. Durán et al., 1984, Julivert et al., 1987 and Na- 
vidad and Barnolas, inpress). Since there is no evidence 
of collisional events during Ordovician times in the 
u 
region studied the setting was apparently anorogenic. 
It may have been an extensional environment, but, as 
mentioned above, partia1 melting of the pre-existent 
crust did not give rise to typical anorogenic magmatism; 
aluminous magmas with calc-alkaline affinities were 
produced instead. This suggests local heat influx from 
the mantle (uprising of mantle slices along deep frac- 
tures) in the lower part of the pre-existent crust and 
fusion of recycled-crust (~adomian  granitoids) to 
TABLE 1.-  Chemical composition of Ordovician metavulcanites from the Guilleries area* 
Sample GMA11 GMA12 GMA14 GMAl5 GMA16 
SiO, 
TiO, 
MnO 
MgO 
C a 0  
Na,O 
K2O 
I.L. 
TOTAL 
*Analyses from Duran (1986) included in Figs. 3 and 4 of Julivert et al. (1987) 
TABLE 2.- Rare earth element composition of Silurian metabasites from the Tibidabo area 
Sample 431C 43 1A 430A 43 1B 
~ roduce  a large quant i t~  of acid magmas in a short Collcerola area. Silurian metabasites occur in two 
period of time. forms: 1) as sills or interlayered bodies, metric to 
decamentric in thickness, often rnicrogabroic in appearance; 
2) as centimetric to milimetric beds within an essentially 
metapelitic matrix; the microtextures and field relatioships 
SILURIAN IGNEOUS ROCKS of the latter suggesting an origin as basic tuffs or 
volcano-sedimentary materials. These rocks were 
affected by Hercynian regional metamorphism under 
Basaltic igneous rocks occur at the base of the greenschist facies conditions, and, locally, by the 
Silurian sequence in various places in the Sierra de thermal effects of late-kinematic Hercynian granite 
100 
episode of apparently static partia1 melting of the pre- 
existent continental crust. Hence the same process of Ordovician 
metavulcanite localized decompression might be responsible for the heating of the lower crust and, subsequently, the ascent U Orthogneiss 
of deep, mantle-derived magmas and their emplacement 
- Mull into or near surface levels during the Lower Silurian. 
1 o  Chile 
0 
e: 
s O 
2 1 
1000 - 
- Ordovician metavulcanite 
4- Orthogneiss 
;ranites from Gabo Suite 
.1 
(dA h m r  9 9  $ d * $  
Figure 4.- Spidergram (rock vs. ORG) for Ordovician metavulcanites 
and orthogneisses from the Catalonia Coastal Ranges. Diagram 
and data for anorogenic (Mull) and orogenic (Chile) granites after 
Pearce et al. (1984). Data from Navidad and Barnolas (in press). 
intrusions, giving rise to hornblende- to pyroxene- 
hornfels associations. Some data on the petrography 
and major element chemistry of these rocks may be 
found in Julivert et al. (1987) and Gil Ibarguchi and 
Julivert (1988). New data obtained by ICP methods 100 (cf. Govindaraju andMeveíle,1987, foranalytical technique 
o O)
details) on their REE composition are presented in this 4 
study. Samples analyzed are the same as those reported 
by Gil Ibarguchi and Julivert (1988) for major elements 8 
and correspond to the massive, sill-like varieties. . 
3 10 Geochemically the Silurian rocks are very different 2 from the Ordovician metavulcanites and orthogneisses. 
Both major elements and rare earths of the Silurian 
rocks are alkaline. According to their major element 
composition these rocks may be classified as alkali 
o e 
- 131C 
-3- 4 3 1 A  
 4 3 0 A  
.__+_ 4 3 1 B  
r 
: 
B 
1 -  i 1 I 1 1  
basalts (TAS classification, Fig. 3), while the REE d s  a f i s a  A 
spectra are also very similar to those of alkali basalts a u  z m w o  a 2 $ 3  
from continental areas elsewhere, showing continously 
fractionated patte~rns from LREE to HREE and minor 
negative or slight~y positive anomalies ( E ~ / E ~ *  = Figure 5.- Chondrite normalized REE distribution for the Ordovician 
0.99-1.08, Fig. 5B). metavulcanites and orthogneisses (part A), and for the Silurian 
metabasites (part B) from the Catalonia Coastal Ranges. Data in A 
~h~ geodynamics involved in the origin of this type fromNavidadandBarnolas(inpress),inBfromthisstudy. Compositional 
range of akali basalts and tephrites from Rotschild Island in A after 
0f magmatism is nOrmall~ with distensive/ Hole (1988), and of anorogenic granites from Gabo and Mumbulla 
anorogenic environments. in the present case this in B after Coliins et al. (1982). Normalization values after Evensen 
could be related with the previous Upper Ordovician et al. (1978). 
28 
ACKNOWLEDGMENTS 
Financial support to JIGI and L A 0  by the Spanish CAICYT under 
Project No. 84-0971 is gratefully acknowledged. 
REFERENCES 
BARNOLAS, A.and GARCIA SANSEGUNDO, J., in press: Ca- 
racterizacidn estratigráfica y estructural del Paleozoico de 
Les Gavarres. Libro Homenaje a Faura i Sans. Serv. Geolog. 
Generalitat de Catalunya. 
CHURCH, B. N., 1975: Quantitative classification and chemical 
comparison of common volcanic rocks. Geol. Soc. Amer. Bull., 
86: 257-263. 
COLLINS, W. J., BEAMS, S. D., WHITE, A. J. R and CHAPPELL, 
B. W., 1982: Nature and origin of A-type granites with 
particular reference to Southeastern Australia. Contrib. Mine- 
ral. Petrol.,80: 189-200. 
DURAN, H., 1986: El Paleozoico de Les Guilleries, Abst. Ph. D. 
Thesis, Univ. Autónoma Barcelona, pp. 1-34. 
DURAN, H., GIL IBARGUCHI, J. I., JULIVERT, M. and UBACH, 
J., 1984: Early Paleozoic acid volcanism in the Catalonian 
Coastal Ranges , Northwestern Mediterranean:. In: Sassi, F. 
P., Julivert, M., Eds., IGCP No. 5, Newsletter, 6: 33-43. 
EVENSEN, M. M., HAMILTON, P. J. and O'NIONS, R. K., 1978: 
Rare-earth abundances in chondritic meteorites. Geochim. Cos- 
mochim. Acta,42: 1199-1212. 
GIL IBARGUCHI, J. I. and JULIVERT, M., 1988: Petrologia de la 
aureola metamórfica de la granodiorita de Barcelona en la 
Sierra de Collcerola, Tibidabo:. Estudios Geol., 44: 353-374. 
GOVINDARAJU, K. and MEVELLE, G.,, 1987: Fully automated 
dissolution and separation methods for inductively coupled 
plasma atomic emission spectrometry rock analy sis. Application 
to the determination of rare earth elements. Jour. Anal. Atom. 
Spectrom., 2: 615-621. 
HARTEVELT, J. J. A., 1970: Geology of the Upper Segre and 
Valira valleys, Central Pyrenees, AndorraISpain. Leidse Geol. 
Meded., 45: 167-236. 
HOLE, M. J., 1988: Post-subduction alkaline volcanism along the 
Antarctic Peninsula. Journal of the Geol. Society, London, 145: 
985-998. 
JULIVERT, M., DURAN, H., GARCIA LOPEZ, S. ,GU. IBARGUCHI, 
J. I., TRUYOLS MASSONI, M. and VILLAS, E., 1987: Pre- 
Carboniferous rocks in the Catalonian coastal ranges: volcanism, 
stratigraphic sequence and fossil content. In : Flügel, H.W., 
Sassi, F. P., Grecula, P., Eds.:, Pre-Variscan and Variscan events 
in the Alpine-Mediterranean mountain belts, Mineralia Slovaca, 
Monography, Alfa Bratislava, pp. 313-322. 
LAUMONIER, B., 1988: Les groupes de Canaveilles et Jujols, 
<<Paléozoi'que Inférieurs: des Pyrinées orientales. Arguments 
en faveur de l'age essentiellement Cambrien des series. Hercynica, I 
4 (1): 25-38. 
MELENDEZ, B. and CHAUVEL, J., 1981: Surquelques Cystoidées 
cités par les Drs. J. Almera et M. Faura dans I'Ordovicien de 
Barcelona. Acta Geol. Hisp., 14: 318-321. 
NAVIDAD, M. and BARNOLAS, A., in press: El mgmatismo del 
Paleozoico Superior deLos Catalanides, Gerona: Bol. Geol. Min. 
PEARCE, 3. A., HARRIS,N. B. W. and TINDLE, A. G., 1984: Trace 
element discrimination for the tectonic interpretation of granitic 
rocks. Jour. Petro1.,25 (4): 956-983. 
SANTANACH, P., 1974: Estudi tectónic del Paleozoic inferior del 
Pirineu entre la Cerdanya i el riu Ter. Tesis, Univ. Barcelona, 
Publ. Fund. S. Vives Casajuana, pp. 1-131. 
VILLAS, E., DURAN, H. and JULIVERT, M., 1987: The Upper 
Ordovician clastic sequenceof the Catalonian Coastal Ranges 
and its brachiopod fauna. Neues Jhb. Geol. Palaont. Abh.; Mh.; 
174: 55-74 
WHALEN, J. B., CURRIE, K. L. and CHAPPELL, B. W., 1987: A- 
type granites: geochemical characteristics, discrimination and 
petrogenesis. Contrib. Mineral. Petrol., 95: 407-419. 
ZANETTIN, B., 1984: Proposed new chemical classification of 
volcanic rocks. Episodes, 7, (4): 19-20. 


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Ordovician and Silurian igneous rocks and orthogeneisses in the Catalonian Coastel Ranges

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Ordovician and Silurian igneous rocks and orthogeneisses in the Catalonian Coastel Ranges

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