neogene ultrapotassic volcanism

C
H
A
P
T
E
R
13
NEOGENE
ULTRAPOTASSIC VOLCANISM
View of the Cabezo María (Vera, Almería): a hill created by
the accumulation of “verite” breccias in a submarine
emission centre.
Bellido Mulas, F.
Brändle Matesanz, J.L.
Figure 1, above. Location of the geosite’s outcrops.
Figure 2, below. Jumillite of La Celia at the entrance
to a gallery of the old apatite mines.
Figure 3, below. Thin section photograph of a massive
jumillite with conspicuous phenocrysts of olivine and
phlogopite (magnified 33 times, parallel nichols).
This chapter deals about the origin and significance of
a small group of rocks resulting from a type of volcanism with very few representatives globally: ultrapotassic (lamproitic) volcanism. Their geodynamical and
volcanological importance lies on the fact that their
knowledge is paramount to study magmas coming
from the Earth’s mantle. One of the most representative zones globally is found in the southeast of the
Iberian Peninsula, in an area between Vera, the region
of Cartagena, and the towns of Cancarix and Jumilla
in the External Betic Domain (Figure 1). The examples
chosen correspond to the type outcrops from which
the rocks earned their generic name (verite, jumillite,
fortunite, and cancalites or cancarixites), with photographs of the most representative samples as they are
seen in the petrographic microscope. Also, in the volcanic area of Campos de Calatrava is the ultrapotassic
emission centre of Morrón de Villamayor, among other
Neogene volcanic edifices of ultra-alkaline character.
Due to the diversity and complexity of the mineralogy of these rocks, they were given their own names,
as they were considered to be different from other
known rocks. The names verite, jumillite, fortunite and
cancalite or cancarixite are all derived from the most
important town near each exposure (Parga Pondal,
1935; Fuster et al., 1967).
Within this volcanic province, it is possible to identify
five magmatic associations: calcalkaline series, highpotassium calcalkaline series, shoshonitic series, ultrapotassic (lamproitic) series, and basaltic alkaline series.
The volcanic events to which the first four series are
linked took place between 15 and 6 million years ago,
although the ultrapotassic volcanic activity is restricted
to the final stages (8-6 million years ago).
This volcanic province is related to the extensional
event explained in the previous chapter, which took
place between the middle and late Miocene (12 million years ago). During this extensional collapse, the
volcanic events hereby considered occurred following the recently formed faults. The exceptional characteristics of the geodynamic
context and volcanic features
of this region have to be
remarked, since they are not
contemporary to the subduction processes. Instead, they
are associated to the melting
due to the extensional stage
affecting the lithospheric mantle during the Miocene, which
had previously been geochemically enriched in the subduction compressive phase, and
also by contamination from
other basement melts.
Data recently obtained about
the interpretation of this volcanism and its placement within
the Betic orogen evolution can
14 0
Bellido Mulas, F. - Brändle Matesanz, J.L.
Figure 4. Flow dome of
Cancarix, formed by
massive cancarixite or
cancalite with columnar
jointing, making up the
main reliefs of Sierra de
Las Cabras.
Figure 5. Thin section
photograph of a
cancarixite with olivine,
chestnut-coloured
phlogopite, yellowish
richterite, and sanidine
(magnified 33 times,
parallel nichols).
be found in the works by López Ruiz et al. (2002,
2004) and Duggen et al. (2005).
These volcanic deposits are mostly associated to volcanic chimneys, domes and dykes. Some of these
edifices (Vera and Barqueros) preserve remains from
the emission centers and flows. In the case of Vera,
the main emission centre and the flows formed under
shallow water.
The ultrapotassic volcanic exposure from Jumilla,
where jumillite was first described, is found in a
place called La Mina – Caserío de La Celia (Figure 2) in
Jumilla (Murcia). The rock shows a massive character,
is brown-grey or dark green in colour, and displays
an intense surface weathering. Their main mineralogy
(Figure 3) consists of olivine phenocrysts, phlogopite
and diopside, with apatite being relatively abundant.
ULTRAPOTASSIC NEOGENE VOLCANISM
In association with the scoria we find uneven concentrations of apatite and hematite (Celia Mines) which
are linked to exhalative processes related to the volcanic activity, and which were developed in the past to
be used in the fabrication of phosphate fertilizers.
According to the absolute dating carried out by
Duggen et al. (2005), the age of this volcanic edifice is
6.76 ± 0.04 million years.
The exposure of Sierra de Las Cabras, between the
villages of Cancarix and Agramón (Hellín, Albacete),
is the type locality for cancalite or cancarixite. It
consists of a volcanic dome with marked escarpments
standing out over the plains, associated to Jurassic and
Tertiary sedimentary exposures upon which it is found.
The escarpments are formed by lavas with beautiful
columnar jointing, rather homogeneous and with a
141
Figure 6, above. Submarine breccias of the Cabezo de
María (Vera, Almería). Notice the vertical structures
corresponding to dykes, and degassing channels of
the emission centre.
Figure 7. Thin section photograph of a verite
(magnified 22 times, parallel nichols) with a vacuole
filled by calcite, carbonated olivines, and pyroxene
microliths in beige-greenish glass matrix (Cabezo
María, Vera).
grey colour with pink shades (Figure 4). Absolute datings provide an age of 7.04 ± 0.01 million years.
These rocks have a main mineralogy formed by olivine, phlogopite, sanidine and potassic richterite. The
most common accessory minerals are the apatite and
calcite (Figure 5).
The main exposures of verite are found in an area
between the towns of Vera, Garrucha, Los Gallardos
and Antas, near the Mediterranean coast, in the
province of Almería. Here, the remains of an emission
centre are located at Cabezo María (Figure 6), as well
as several traces of lava flows scattered between this
volcanic centre and the coast north of Garrucha.
This emission centre is highly degraded and constitutes a promontory formed by tuffs, remains of lava
14 2
flows, submarine hydroclastic breccias, and dykes corresponding to feeder channels. Generally, these rocks
have an abundant vitreous matrix and present olivine
and phlogopite phenocrysts (Figure 7). Their radiometric age is 7.45 ± 0.08 million years.
In La Salaosa and Cañada de las Moreras (Vera) there
are outcrops of submarine lava flows of rather vitreous massive verite (Figure 8) which flowed on a bottom of Miocene marly sediments, scarcely or not even
consolidated at all, which sometimes were injected
in the flows to form so-called neptunian dykes. The
flows are interbedded within Upper Miocene-Pliocene
sandstones and marine marls.
Fortunite (Figure 9) was described for the first time
in the volcanic edifice of Los Cabecitos Negros de
Fortuna (Murcia). It is a volcanic lamproitic rock
Bellido Mulas, F. - Brändle Matesanz, J.L.
Figure 8, above. Light-coloured marly sediments
injected between the black pillow lavas of verite,
typical of submarine lava flows.
Figure 9, above, right. Outcrop of a circular dyke of
fortunite injected in non-consolidated marly
sediments. The dyke dips towards the interior of the
volcanic edifice.
Figure 10, right. Thin section photograph of a
fortunite (magnified 13.5 times, parallel nichols):
olivine and phlogopite phenocrysts in a chestnutcoloured glass matrix. Fortuna (Murcia).
Figure 11, below. Conspicuous relief of lamproitic
(ultrapotassic) lava flows lying on Miocene limestones
and marls at the summit of the Cerro de Salmerón
(Moratalla, Murcia).
whose main mineral composition is orthopyroxene,
phlogopite, sanidine and some diopside (Figure 10).
The volcanic edifice of Cerro de Salmerón (Figure
11) or El Monagrillo (Moratalla, Murcia) is one of the
most typical exposures of ultrapotassic volcanism in
SE of Spain. It includes several units of a volcanic neck
(roots of the point of emission), lava flows, dykes and
breccias associated to its volcanic activity.
The datings show an age of 7.12 ± 0.07 million years.
The main mineralogy consists of olivine, phlogopite,
amphibole and sanidine (Figure 12), with abundant
apatite.
The volcanic edifice of El Cabezo Negro de Zeneta
(Murcia) is around 3 km southeast of Zeneta (Murcia),
on a lonely hill standing out in mid Tortonian (Miocene)
ULTRAPOTASSIC NEOGENE VOLCANISM
sediments. Its morphology is that of a volcanic neck
dome (Figure 13) intruded in Tortonian marls and
sandstones, and has a breccioid chimney in its centre.
The intrusion’s age is 8.08 ± 0.03 million years (postmid Tortonian). These are dark ultrapotassic rocks with
a porphiritic texture and phenocrysts of phlogopite,
biotite and olivine.
Finally, the volcanic edifice of Calasparra (Murcia)
can be seen at an old quarry near the junction of the
road C-3314, 1.5 km to the northwest of Calasparra.
It belongs to a small subaerial emission centre whose
crater has a volcanic neck with columnar jointing
(Figure 14). This geosite presents a magnificent
exposure of ultrapotassic volcanic rocks and their
143
Figure 12. Thin section photograph of the
ultrapotassic vulcanite of Cerro de Salmerón
(Moratalla) with olivine phenocryst and phlogopite
crystals in a sanidine and clinopyroxene matrix
(magnified 13.5 times, crossed nichols).
Figure 13. Morphology of the eastern end of the volcanic dome of Cabezo Negro de Zeneta (Murcia).
Figure 14. Columnar jointing in lamproites of the
central dome of the Cerro Negro volcano, Calasparra
(Murcia).
Figure 15. Thin section photograph of ultrapotassic
lamproite from Calasparra: olivine phenocrysts and
phlogopite in a microcrystalline matrix (magnified 52
times and parallel nichols).
relations to the host sedimentary rocks of Tortonian
age (Miocene). It displays a certain affinity to the
jumillite, being its main mineralogical composition
olivine, clinopyroxene, phlogopite, sanidine and
alkali amphibole (Figure 15).
It is therefore possible to conclude that, thanks to its
global geodynamic, volcanologic and petrologic interest, it is highly important to study, popularize and
protect these rocks, whose names are still used and
quoted in international scientific media. The extreme
rareness of these rocks in the international volcanological record is the reason to promote their protection, as
it has already been done by the regional governments
of Castilla-La Mancha and Murcia in the case of the
Natural Monuments of the Volcanic Neck of Cancarix
and Celia Mines.
14 4
Bellido Mulas, F. - Brändle Matesanz, J.L.
REFERENCES
BAENA, J. (1981). Mapa Geológico de
España a escala 1/50.000 Nº 869
(Jumilla). IGME, Serv. Pub. Ministerio
de Industria, Madrid.
BELLIDO MULAS, F. and BRÄNDLE
MATESANZ, J.L. (2006). Asociaciones
volcánicas ultrapotásicas (lamproíticas)
neógenas del SE de la Península Ibérica.
Informe final para el "Proyecto Global
Geosites", IGME.
BELLON, H., BIZON, G., CALVO, J.P.,
ELÍZAGA, E., GAUDANT, J. and LÓPEZ
MARTÍNEZ, N. (1981). Le volcan du
Cerro del Monagrillo (Province de
Murcia): âge radiométrique et
corrélations avec les sédiments néogènes
du bassin de Hellín (Espagne). Comptes
Rendus Academie Sciences de Paris, 292,
1.035-1.038.
DUGGEN, S., HOERNLE, K., Van den
BOGAARD, P. and GARBE-SCHÖNBERG,
D. (2005). Post-collisional transition from
subduction to intraplate-type
magmatism in the westernmost
Mediterranean: Evidence for continentaledge delamination of subcontinental
lithosphere. Journal of Petrology, 46,
1.155-1.201.
FERMOSO, M.L. (1967). El diópsido de las
rocas volcánicas de Jumilla (SE de
España). Estudios Geológicos, 23, 31-33.
FERNÁNDEZ SANTÍN, S. and HERNÁNDEZPACHECO, A. (1972). Las rocas
lamproíticas de Cabezo Negro, Zeneta
(Murcia). Estudios Geológicos, 28,
269-276
FÚSTER, J.M., GASTESI, P., SAGREDO, J. and
FERMOSO, M. (1967). Las rocas
lamproíticas del SE de España. Estudios
Geológicos, 23, 35-69
ULTRAPOTASSIC NEOGENE VOLCANISM
FÚSTER, J.M. and SAGREDO, J. (1966).
Estudio petrológico de las rocas
lamproíticas de Calasparra. Congreso del
Manto Superior, Madrid, 4-19.
GALLEGO, I.C., GARCÍA de DOMONGO, A.,
JEREZ MIR, L. and LÓPEZ OLMEDO, F.
(1984). Mapa Geológico de España a
escala 1/50.000. Isso. IGME, Serv. Pub.
Ministerio de Industria, Madrid.
GARCÍA-CORTÉS, A., RÁBANO, I.,
LOCUTURA, J., BELLIDO, F., FERNÁNDEZGIANOTTI, J., MARTÍN-SERRANO, A.,
QUESADA, C., BARNOLAS, A. and
DURÁN, J.J. (2000). Contextos
geológicos españoles de relevancia
internacional: establecimiento,
descripción y justificación según la
metodología del proyecto Global
Geosites de la IUGS. Boletín Geológico y
Minero. 111-6, 5-38. Madrid.
GARCÍA-CORTÉS, A., RÁBANO, I.,
LOCUTURA, J., BELLIDO, F., FERNÁNDEZGIANOTTI, J., MARTÍN-SERRANO, A.,
QUESADA, C., BARNOLAS, A. and
DURÁN, J.J. (2001). First Spanish
contribution to the Geosites Project: list
of the geological frameworks established
by consensus. Episodes, 24. 2, 79-92.
LE MAITRE, R.W., BATEMAN, P., DUDEK, A.,
KELLER, J., LAMEYRE, J., LE BAS, M.J.,
SABINE, P.A., SCHMID, R., SÖRENSEN,
H., STRECKEISEN, A., WOOLLEY, A.R.
and ZANETIN, B. (1989).
A classification of igneous rocks
and glossary of terms: Recommendations
of the International Union of Geological
Sciences Subcommision on the
Systematics of igneous rocks. Blackwell
Scientific Publications, Oxford, U.K.
LÓPEZ OLMEDO, F. and DÍAZ de NEIRA, J.A
(en prensa). Mapa Geológico de España
a escala 1/50.000 Nº 890 (Calasparra).
IGME, Madrid.
LÓPEZ RUIZ, J., CEBRIÁ, J.M., DOBLAS, M.
and BENITO, R. (2004). La región
volcánica de Almería - Murcia. El
vulcanismo neógeno peninsular. In: Vera,
J.A. (Ed.), Geología de España, SGEIGME, Madrid, 678-680.
LÓPEZ RUIZ, J., CEGRIÁ, J.M. and DOBLAS,
M. (2002). Cenozoic volcanism I: the
Iberian peninsula. In: Gibbons, W. y
Moreno, T. (Eds.), The Geology of Spain
The Geological Society, London, 417-680.
LÓPEZ RUIZ, J. and RODRÍGUEZ BADIOLA, E.
(1980). La región volcánica neógena del
Sureste de España. Estudios Geológicos,
36, 5-63.
MITCHELL, R.H. and BERGMAN, S.C.
(1991). Petrology of lamproites. Plenum
Pres, New York, 447 pp
NAVARRO, A. and TRIGUEROS, E. (1966).
Plano geológico de la provincia de
Murcia. Instituto Geológico y Minero
de España.
PARGA PONDAL, I. (1935). Quimismo de las
manifestaciones magmáticas cenozoicas
de la Península Ibérica. Trab. Mus. Nac.
Cienc. Nat. de Madrid. Serie Geología,
39, 1-174.
PELLICER, M.J. (1973). Estudio petrológico y
geoquímico de un nuevo yacimiento de
rocas lamproíticas situado en las
proximidades de Aljorra (Murcia).
Estudios Geológicos, 29, 99-106.
RODRÍGUEZ BADIOLA, E. (1973). Estudio
petrogenético del vulcanismo terciario
de Cartagena y Mazarrón: SE de España.
Univ. Complut. de Madrid. Tesis
doctoral, 177 pp.
VENTURELLI, G., CAPEDRI, S., Di BATTISTINI,
A., CRAWFORD, A., KOGARKO, L.N. and
CELESTINI, S. (1984). The ultrapotassic
rocks from southeastern Spain. Lithos,
17, 37-54.
145