REPLY TO THE DISCUSSION OF PETROGRAPHY AND
GEOCHEMISTRY OF GRANITOID PEBBLES FROM THE
OLIGOCENE-MIOCENE DEPOSITS OF THE INTERNAL RIFIAN
CHAIN (MOROCCO): A POSSIBLE NEW HYPOTHESIS OF
PROVENANCE AND PALEOGEOGRAPHICAL IMPLICATIONS
BY G. CARERI, F. GUERRERA, A. MARTIN-ALGARRA,
M. MARTIN-MARTIN, A. MESSINA & V. PERRONE
LISA GIOCONDA GIGLIUTO, DIEGO PUGLISI & GIUSEPPA PUGLISI
Dipartimento di Scienze Geologiche, University of Catania, Corso Italia 55, 95129 Catania, Italy; geolisa@infinito.it, dpuglisi@unict.it,
gpuglis@unict.it
Introduction
As we can see, it seems evident that the paper Petrography
and geochemistry of granitoid pebbles from the Oligocene-
Miocene deposits of the Internal Rifian Chain (Morocco): a
possible new hypothesis of provenance and paleogeographi-
cal implications (Gigliuto et al. 2004) brought up some ob-
servations within the scientific community working on the
Oligocene-Miocene paleogeographical reconstructions of the
Betic-Rifian Chain.
The criticized points will be considered below and some of
these have already been debated with F. Guerrera and M. Mar-
tín-Martín during the process of revision of this paper, when
they were invited by the Editorial Office of Geologica Car-
pathica, at our suggestion, to revise the manuscript as Referees
(they were two of the four Referees).
F. Guerrera immediately accepted our manuscript for publi-
cation with minor revisions as well as the other two Refer-
ees, whereas M. Martín-Martín strongly condemned the re-
sults obtained and described within the paper up to the end of
the revision process, because they are strongly in contrast with
the paleogeographical models already existing in the Spanish
geological literature.
Now, the number of criticized points increased, probably as
a consequence of the increasing number of people added to
the two old Referees to form the new team of authors of this
Discussion (Careri et al., henceforth A. D., i.e. Authors of the
Discussion).
In the following section we will try to answer their critical
point, but, firstly, we must thank the Editorial Office of Geo-
logica Carpathica for offering us the possibility to reply to the
critical discussion of the A. D. regarding our previous paper.
Response
The first point criticized by the A. D. regards the caption of
Fig. 1, a tectonic sketch map of a big area (from Italy to the
Straits of Gibraltar), where the different units are not suffi-
ciently subdivided into minor tectonic units. We think that it is
a simple tectonic sketch map and an increase of details within
this map is not useful because it lies outside the main topic of
the paper.
The second criticism of the A. D. concerns the use of the
AlKaPeCa term.
This word has firstly been used by Bouillin et al. (1986) to
indicate the internal zones of the Alboran-Kabylian-Pelori-
tani-Calabria ensemble as belonging to the southern paleomar-
gin of the European plate. We know that this hypothesis, al-
ready suggested by Bouillin (1984), Leblanc & Olivier
(1984), Rehault et al. (1984; 1985) and by Dercourt et al.
(1986) and successively supported by many other authors
(Courme & Mascle 1988; Durand-Delga & Olivier 1988;
Dewey et al. 1989; Boccaletti et al. 1990; Weltje 1992), is in
contrast with another hypothesis, which considers these ter-
ranes as an independent block originally located between the
European and African plates.
Nevertheless, we think that to describe also this last hypoth-
esis within a chapter where we must mainly speak about the
geological setting and about the objectives of the paper could
REPLY
GEOLOGICA CARPATHICA, 55, 4, BRATISLAVA, AUGUST 2004
349352
350 GIGLIUTO et al.
represent useless confusion for the reader and, furthermore,
we also think that, at the present, this dualism of paleogeo-
graphical hypotheses cannot be resolved. The data of this pa-
per, in fact, only represent paleogeographical implications
which, perhaps, could emphasize the AlKaPeCa hypothesis of
Bouillin et al. (1986) but without supporting it with certainty.
Furthermore, regarding the petrographic characters of the
analysed granitoid pebbles, we agree with the A. D. because
we also think that these pebbles show very similar petrograph-
ic characters to those of the granitoid rocks of the Calabria-
Peloritani Arc and we have already described this similarity
many times (Puglisi et al. 2001; Zaghloul 2002; Zaghloul et
al. 2002; Zaghloul & Puglisi 2003). Nevertheless, at the time
of those publications, we had no geochemical data and we
could never hypothesize, for these pebbles, a source different
from that suggested by previous authors (Martín-Algarra et al.
1995, 2000).
Now, on the basis of these new results and according to
many authors, we are strongly convinced that petrographic
study alone is not sufficient to obtain all the information nec-
essary to discriminate within the granitoid rock family. For
more than 20 years, in fact, it has been common knowledge
that the modal data of plutonic rocks are considered an obso-
lete methodology also for their classification and, consequent-
ly, they are not useful as parameters to discriminate within the
granitoid rock clan. Geochemical analyses, instead, mainly ad-
dressed to detect the trace element contents, represent the best
methodologies up to now used to distinguish different grani-
toid rocks.
As regards the probable green-schist metamorphic over-
print locally observed in the analysed pebbles, we want to
underline that this feature is not exclusive to the acidic grani-
toid of the Calabria-Peloritani Arc but also occurs in the Iberi-
an Massif (Neiva et al. 1987; Wickham 1987).
Another criticized point regards the probable length of the
transport of the well rounded analysed granitoid pebbles (3 to
10 cm sized and never reaching 30 cm of diameter, as men-
tioned by the A.D.) inferred from some sedimentological
characteristics of the conglomerate lithofacies. These con-
glomerates seem to be linked to debris flows and/or to high
concentrated turbidity current processes which do not neces-
sarily imply short transports. The debris flow process, in fact,
belongs to the mass transport category of sedimentary pro-
cesses, whose cannibalistic feeding provokes the re-mobiliza-
tion and the consequent re-sedimentation of already deposited
sediments. So, the total length of the transport must be calcu-
lated also taking into account the distance between the source
area and the temporary deposition area where the debris flow
processes were triggered off. Furthermore, it is common
knowledge that the roundness of the pebbles in these deposits
is mainly a hereditary characteristic derived from the first
transport (source area to temporary deposition area) rather
than linked to the distance covered by the debris flow process.
This type of sedimentary process, in fact, is not able to pro-
duce high degrees of roundness of the clasts because the high
content of matrix reduces the impacts between the clasts. Of
course, all these considerations regarding the interpretation of
the length of transport may be applied to the high concentrated
turbidity currents.
Finally, concerning the geochemistry chapter, we must
specify that the first assertion of the A. D. is highly inaccurate
because it is absolutely incorrect to affirm that our geochemi-
cal data have been compared with Hercynian and pre-Hercyn-
ian plutonites heterogeneous in composition.
The geochemical data of our analysed granitoid pebbles
have been compared with all the compositions available in lit-
erature (Peloritani Mts., Sicily: Capo Rasocolmo, Calabria:
Aspromonte, Capo Vaticano, Serre and Sila), most of which
(about 60 %) mainly shows more than 70 % of SiO
2
and be-
longs to the subalkaline peraluminous suites (i.e. two
mica±cordierite±Al silicate acidic plutonites). In particular,
the data of the A. D.s Table IVb have also been included in
our comparison, whereas we excluded all the more basic
rocks. A careful control of our selected references, not
checked by the A. D., should have surely testified to this
choice!
Now, also the new data performed by the A. D. (Table IVa)
have been included within the new diagrams (Fig. 1) and our
geochemical considerations have not been modified;
geochemical characters of the analysed granitoid pebbles, in
fact, are always closely compatible with those of the granitoid
rocks of the Iberian Massif. The greater part of the acidic plu-
tonites of the Calabria-Peloritani Arc, instead, shows a differ-
ent chemism (lower Rb and higher Sr and Ba contents).
Furthermore, we think that the Figures 1 and 2 of the A. D.
cannot be significant to prove that the analysed granitoid peb-
bles belong exclusively to the Calabria-Peloritani Arc realm.
As already stated above, in fact, the modal data cannot be suc-
cessfully used to discriminate within the granitoid rock family.
0
200
400
600
800
1000
70
72
74
76
78
80
SiO
2
Rb
Calabria-Peloritani Arc
Analyzed pebbles
Iberian Massif
0
100
200
300
400
500
600
70
72
74
76
78
80
SiO
2
Sr
Calabria-Peloritani Arc
Analyzed pebbles
Iberian Massif
0
200
400
600
800
1000
1200
1400
1600
1800
2000
70
72
74
76
78
80
SiO
2
Ba
Calabria-Peloritani Arc
Analyzed pebbles
Iberian Massif
Fig. 1. Diagrams showing the Rb, Sr and Ba ppm contents vs. the
SiO
2
weight percentages.
GRANITOID PEBBLES OF THE RIFIAN CHAIN (MOROCCO) REPLY 351
Similarly, like many other authors, we also think that to use
the major-oxide compositions as discriminant parameters rep-
resents an obsolete methodology; so, if we include within the
diagrams of Figure 3 and 4 of the A. D. also the chemical data
of the peraluminous plutonites of the Iberian Massif, they will
fall in the same area.
Furthermore, the high Al
2
O
3
contents and the A/CNK > 1
ratio of the studied pebbles allow us to exclude their belong-
ing to I-type granitoids (typically metaluminous), thus con-
firming the inadequacy of the diagrams used by the A. D. in
their Figures 3 and 4.
In the Figures 5 and 6 of the A. D. it is difficult to under-
stand why the data of the Sila plutonites have not been differ-
entiated! In these diagrams, in fact, the data of two different
plutonite suites of the Sila Batholith have been plotted: (1)
pyroxene+amphibole+biotite-bearing gabbros or diorites to
granodiorites and (2) two mica+cordierite+Al-silicate-bearing
granodiorites to leucomonzogranites. In our Figure 2, instead,
we compare the analysed granitoid pebbles only with the
geochemical data of the Sila plutonites available in literature
(Messina et al. 1991a,b, 1993), showing a SiO
2
content >70 %.
Also in this diagram the studied pebbles are well characterized
by higher contents of Rb, which strongly mark the difference
existing between the acidic plutonites of the Sila Batholith and
our granitoid pebbles.
Finally, concerning the trace elements, an enrichment of
light REE coupled with a depletion of heavy REE and with a
negative Eu anomaly is also typical of the Iberian Massif plu-
tonites (Rottura et al. 1989; Holtz & Barbey 1991).
The comparison of a very large number of geochemical data
allowed us to characterize the differences between the Cala-
bria-Peloritani Arc and the Iberian Massif peraluminous and
metaluminous plutonites as mainly related to the average con-
tent of Sr, Rb and Ba.
These differences (higher Rb and lower Sr and Ba contents
Iberian Massif; lower Rb and higher Sr and Ba contents
Calabria-Peloritani Arc), probably connected to very interest-
ing and complicated petrogenetic histories of the two orogenic
complexes, can be very useful to understand the source of the
analysed granitoid pebbles.
Nevertheless, the A. D. persist to consider the analysed
granitoid pebbles as belonging to the Calabria-Peloritani Arc
on the basis of very debatable arguments and they reject the
evidence of the differences existing between these two big
Fig. 2. Rb vs. SiO
2
diagram. Diamond Sila granitoids, dots
pebbles.
50
100
150
200
250
300
350
70
72
74
76
78
80
SiO
2
Rb
Sila granitoids
Analyzed pebbles
orogenic complexes, thus showing that they have a limited
open-mindedness about other opinions and a strong will to re-
ject them without sound arguments.
Conclusions
We are conscious that a new hypothesis of provenance is
very difficult to be supported with the small number of analy-
sed granitoid pebbles; for this reason we entitled our paper as
... a possible new hypothesis of provenance and paleogeo-
graphical implications in order to specify that the obtained
data can only represent suggestions rather than a new paleo-
geographical model.
Otherwise, we also think that the suggestion, today, of an al-
ternative provenance could be important in the future (i) for
the researchers which later, by increasing the number of the
available data, could propose a different paleogeographical
model, and (ii) for the authors which first proposed that sug-
gestion and will be cited.
Thus, we hope that these our geochemical results could rep-
resent a new input of research aimed to detect the paleogeo-
graphical scenario responsible for the feeding of the analysed
granitoid rocks. We think, in fact, that only increasing the
number of geochemical analyses will make it possible to ob-
tain paleogeographical reconstructions rather than implica-
tions and to close this scientific controversy.
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