Evolution of the volcanism in the area of interaction between the arabian, anatolian and iranian plates (Lake van, Eastern Turkey)

Geological investigations of the Lake Van area (Eastern Turkey) have shown the coexistence of a calc-alkaline volcanism, active at least since Lower Miocene, with an alkaline one, beginning around 6 m.y. ago. The calc-alkaline volcanic activity is related to subduction of the Arabian plate under the Anatolian—Iranian continental mass. The alkaline volcanism, on the other hand, is attributed to the fragmentation of such a mass and to the divergent motion of the Anatolian and Iranian plates; a process which began in Upper Miocene as a consequence of the continental collision with Arabia.     

Garibaldi group volcanic rocks of the salal creek area, southwestern British Columbia: Alkaline lavas on the fringe of the predominantly calc-alkaline garibaldi (cascade) volcanic arc

The Salal Creek area, at the north end of the main group of vents for the Quaternary Garibaldi (Cascade) Volcanic Belt, southwestern British Columbia, was the site of several small eruptions of mafic lava during the past 1 Ma. In contrast to the calc-alkaline character of all other parts of the Garibaldi Belt and the geographically nearly coincident Miocene and older Pemberton Volcanic Belt, the Salal Creek area Quaternary lavas are predominantly alkaline basalt and hawaiite with typical alkaline volcanic petrography, chemistry, and fractionation trends. Trace elements Ti-Zr-Y show within-plate character for the suite. As for other Garibaldi Belt volcanic rocks, Rb is low, Rb/Sr very low, and ⁸⁷Sr/⁸⁶Sr ratio is low, averaging 0.7032. The oxygen isotopic composition average, ¹⁸O = 5.9, is normal for mantle-derived volcanic rocks.This distinct change in magma type at the end of a volcanic are may be the consequence of a smaller degree of melting, melting at a slightly greater depth than calc-alkaline magma production, or a descending-plate edge effect.Ponded flows and pillow-palagonite accumulations indicate that several Salal Creek area eruptions occurred in proximity to ice which filled major valleys during pre-Wisconsin glacial periods.     

Distribution of Early Tertiary volcanic rocks in south Sumatra and west Java

Abstract   The evolution of volcanism in Sumatra and Java during Tertiary and Quaternary time can be divided into three phases: (i) lava flows of the Early Tertiary event (43–33 Ma) consisting of island arc tholeiites; followed by (ii) eruption of tholeiitic pillow basalt at the beginning of the Late Tertiary (11 Ma); and succeeded by (iii) medium-K calc-alkaline magmatism in the Pliocene and Quaternary. The present available field data on the occurrence of Paleogene volcanic rocks and subsurface data in south Sumatra and northern west Java indicate a much larger area of distribution of the volcanic rocks than previously recognized. Because the eastward continuation of the northern west Java volcanic rocks had not been found, early investigators were inclined to assume that they continued to south Kalimantan. In contrast, the early Tertiary volcanic rocks that occupy the south coast of Java can be traced further east as far as Flores. The occurrence of Paleogene volcanics in south Sumatra and northern west Java can be interpreted as a Paleogene volcanic arc that was presumably related to the late Cretaceous–Paleogene trench parallel to Sumatra and west Java due to subduction of the Indian Plate toward the northeast (Meratus trend).     

Volcano-stratigraphy and geochemistry of collision-related volcanism on the Erzurum–Kars Plateau, northeastern Turkey

The Eastern Anatolia Region exhibits one of the world's best exposed and most complete transects across a volcanic province related to a continental collision zone. Within this region, the Erzurum–Kars Plateau is of special importance since it contains the full record of collision-related volcanism from Middle Miocene to Pliocene. This paper presents a detailed study of the volcanic stratigraphy of the plateau, together with new K–Ar ages and several hundred new major- and trace-element analyses in order to evaluate the magmatic evolution of the plateau and its links to collision-related tectonic processes. The data show that the volcanic units of the Erzurum–Kars Plateau cover a broad compositional range from basalts to rhyolites. Correlations between six logged, volcano-stratigraphic sections suggest that the volcanic activity may be divided into three consecutive Stages, and that activity begins slightly earlier in the west of the plateau than in the east. The Early Stage (mostly from 11 to 6 Ma) is characterised by bimodal volcanism, made up of mafic-intermediate lavas and acid pyroclastic rocks. Their petrography and high-Y fractionation trend suggest that they result from crystallization of anhydrous assemblages at relatively shallow crustal levels. Their stratigraphy and geochemistry suggest that the basic rocks erupted from small transient chambers while the acid rocks erupted from large, zoned magma chambers. The Middle Stage (mostly from 6–5 Ma) is characterised by unimodal volcanism made up predominantly of andesitic–dacitic lavas. Their petrography and low-Y fractionation trend indicate that they resulted from crystallization of hydrous (amphibole-bearing) assemblages in deeper magma chambers. The Late Stage (mostly 5–2.7 Ma) is again characterised by bimodal volcanism, made up mainly of plateau basalts and basaltic andesite lavas and felsic domes. Their petrography and high-Y fractionation trend indicate that they resulted from crystallization of anhydrous assemblages at relatively shallow crustal levels. AFC modelling shows that crustal assimilation was most important in the deeper magma chambers of the Middle Stage. The geochemical data indicate that the parental magma changed little throughout the evolution of the plateau. This parental magma exhibits a distinctive subduction signature represented by selective enrichment in LILE and LREE thought to have been inherited from a lithosphere modified by pre-collision subduction events. The relationships between magmatism and tectonics support models in which delamination of thickened subcontinental lithosphere cause uplift accompanied by melting of this enriched lithosphere. Magma ascent, and possibly magma generation, is then strongly controlled by strike-slip faulting and associated pull-apart extensional tectonics.     

The pliocene volcanism of the voras Mts (Central Macedonia,Greece)

Major element chemistry, K/Ar ages and trace element data are reported for volcanic rocks from the Voras volcanic complex of Central Macedonia (Greece). Petrological data show that the Voras volcanic rocks consist essentially of intermediate members of the high-K calc-alkaline and shoshonitic series, the most abundant rock types being high-K andesites and dacites, latites and trachytes. K/Ar ages determined on selected samples show values ranging between 5.0 and 1.8 m.y., indicating that the Voras volcanism was active from Pliocene up to the Lower Pleistocene. The high Th, Hf, Ba and LREE shown by some representative samples together with their strongly fractionated light and heavy REE patterns and the absence of significant negative Eu anomalies indicate a magma genesis by low degrees of partial melting of a source enriched in large ion lithophile elements, leaving a garnet-bearing and plagioclase-free residue. This source is believed to be represented by a mantle garnet peridotite enriched in incompatible elements. The geotectonic significance of the K-rich volcanism of the Voras area is discussed within the general framewoek of the late Tertiary tectonic evolution of the Aegean area and its emplacement is related to the distension tectonic movements which have affected the boundary area between the Macedonian microplate and the European craton since the Neogene.     

Magma characterization of the Mexican volcanic belt (Mexico)

Over 330 bulk chemical analyses of rocks (Oligocene or Miocene to Recent) from the Mexican Volcanic Belt (MVB) have been compiled. These analyses all together represent a calc-alkaline sequence of continental margin type. The North-Eastern part of the Belt seems to overlap with another volcanic province, namely. Eastern Cordillera in which magmas are mostly of alkaline sequence. A model involving fractional crystallization as the principal mechanism is proposed for magma genesis in the MVB.     

Late Cenozoic alkaline volcanism in the northwestern Caribbean: tectonic setting and Sr isotopic characteristics

A province of alkaline volcanism has developed over the last 10 m.y. in the northwestern part of the Caribbean plate. Most of the volcanism is Quaternary in age and follows an apparent halving of the spreading rate at the Cayman Rise spreading center 2.4 m.y. ago. Intraplate deformation in Central America and the Nicaraguan Rise has produced a series of north-south orientated grabens. This extensional tectonism is associated temporally and spatially with some of the alkaline magmatism. Strontium isotopic ratios of rocks from sixteen of these centers of volcanism enable three separate areas with different isotopic characteristics to be identified. The largest area corresponds to the Nicaraguan Rise and is characterized by low⁸⁷Sr/⁸⁶Sr ratios (0.7026–0.7031). A more concentrated area of alkaline magmatism in northeastern Costa Rica has intermediate⁸⁷Sr/⁸⁶Sr ratios (0.7036–0.7038) which are within the range shown by the adjacent calc-alkaline volcanoes. In central Hispaniola high⁸⁷Sr/⁸⁶Sr ratios (0.7047–0.7063) are found in strongly alkalic rocks and in rocks that are transitional to calc-alkaline in nature. In both Costa Rica and Hispaniola the increased radiogenic strontium may have come from volatile-rich fluids escaping from adjacent subducting slabs of oceanic crust. The isotopic differences between the two areas may be related to the relative longevity and high rate of subduction in Costa Rica compared to Hispaniola. The Costa Rican alkaline rocks overlie a segment of the Cocos plate which is being subducted at a smaller angle (～ 35°) than at the rest of the Central American arc.     

Geotectonic settings of miocene-quaternary volcanism in and around the eastern Tyrrhenian sea border (Italy) as deduced from major element geochemistry

The volcanic rocks along the south-eastern and eastern Tyrrhenian border of Italy have been classified as converging plate margin magma types by using discriminant functions based on major element patterns. These rocks belong to calc-alkaline and shoshonitic associations (shoshonites, and predominant leucitic rocks) ranging in age from Upper Miocene to, mostly, Quaternary. According to the same method of classification, the remaining Italian volcanic rocks — alkali-sodic and subordinate tholeiitic basalts — around the Tyrrhenian border are found to be rocks of the tensional type of Mesozoic to prevailingly Quaternary age. The volcanic materials of the 650 km long SE and E Tyrrhenian border can be related to the convergence of the African-Adriatic and Tyrrhenian plates.     

Evolution and geodynamic significance of the tertiary orogenic volcanism in Northeastern Greece

The Tertiary volcanism of Eastern Macedonia and Western Thrace (Greece) developed in association with the sedimentary basin which formed, from Eocene to Oligocene, along the southern margin of the Rhodope Massif.The volcanic products, ranging in composition from basaltic andesites to rhyolites, show an overall calc-alkaline orogenic affinity, while chemical characteristics identify different groups of rocks, probably reflecting minor differences among parent magmas. The observed evolution within any group of rocks is compatible with fractional crystallization processes acting on relatively shallow magma bodies.The Sr isotopic composition of rhyolitic member shows an initial⁸⁷Sr/⁸⁶Sr ratio comparable with that of basaltic andesites, reinforcing the hypothesis of a crystal/liquid line of descent.Geochemical and petrographic evidence, on the whole, suggests that the investigated orogenic association developed on an active continental margin characterized by a relatively thick crust, acting as a density filter for the basic magmas and facilitating their storage and fractionation within the crust itself. Minor contamination by interaction with host materials may also have occurred.Stratigraphic and K/Ar geochronological data indicate that the volcanic activity started in Upper Eocene and reached its maximum development in Upper Oligocene. From Lower Miocene, the volcanism shifted southward in the Central Aegean area and in part of Western Anatolia, coming to an end by Middle Miocene.The southward migration of the volcanic front has been interpreted as a consequence of the increase in the dipping of the Benioff zone, due to the decrease of penetrative strength after the main phase of continental collision.     

New unspiked K–Ar ages of Quaternary sub-glacial and sub-aerial volcanic activity in Iceland

Indisputable geochronology of Icelandic volcanism may contribute to improving the use of volcanic proxies for paleoenvironmental studies. Accurate and reliable ages may also provide some useful constraints in studying the possible relationship between volcanism and deglaciation in Iceland. Given the difficulty of dating accurately young and low potassic volcanic samples from Iceland, the relationship between deglaciation and increasing levels of volcanism has been shown only for the last deglaciation. The purpose of this study is to evaluate the potential of the unspiked K–Ar dating method for dating Quaternary Icelandic volcanic rocks, because we consider that reliable K–Ar ages of interglacial and sub-glacial volcanic products may generate useful data sets for paleoclimatic reconstructions, so enabling the link between glaciation and volcanic activity to be better established. Given the ages and precisions obtained, this study demonstrates that the unspiked K–Ar method is a promising tool for reconstructing the recent volcanic activity in Iceland during glacial and interglacial intervals.     

The geological diversity of island arc volcanism: Northeast Russia

Paleovolcanological and paleotectonic reconstructions developed for the continent-ocean transition zone in Northeast Asia demonstrate a high diversity of island arc volcanic settings. There are two main types of island arc volcanism recognized so far, (i) volcanic arcs of euliminary systems (VAES) and (ii) intrageosynclinal volcanic arcs, including areas of insular volcanism (IIV). The volcanic arcs of euliminary systems include the present-day Kuril-Kamchatka, Aleutian, and the Paleozoic- Early Cretaceous Taigonos volcanic arcs. The latter is considered to be a part of the Talovka-Taigonos euliminary system (TTES), an old double island arc system analogous to present-day systems, the Kuril-Kamchatka and Aleutian ones. Both the TTES and similar present-day euliminary systems are structural complexes that confine concentrically-zoned geosyncline areas on the side of the Pacific. The characteristic features of the VAES include a long history of evolution, stable (calc-alkaline) basalt-andesite composition of volcanic products, and transverse geochemical zonation. Geophysical evidence reveals the complicated processes of endogenous crustal accretion and destruction of continental crust within the VAES zones. The IIV follow the structural pattern of the corresponding geosynclinal system. Their evolution is relatively short, while the spatial position and the composition of their magmatic bodies may considerably vary at different stages of evolution of the geosynclinal systems. Most island arc zones are characterized by calc-alkaline volcanism, but potassium alkaline, alkali-ultrabasic, and ultrabasic rocks also occur in some structures. The settings of intrageosynclinal insular volcanism are diverse and include (a) volcanic overcompensation, (b) geoanticlinal uplift, and (c) volcanotectonic downwarping during the orogenic stage of geosynclines. The calc-alkaline volcanism of island environments in geoanticline zones is likely related to the endogenous accretion of continental crust within a geosyncline system. Intrageosynclinal island-arc volcanism is still very poorly understood. Investigation of this phenomenon is one of the urgent tasks of paleovolcanology.     

Field and geochemical data bearing on the development of a mesozoic volcano-tectonic rift zone and back-arc basin in southernmost South America

A broad zone of dominantly subaerial silicic volcanism associated with regional extensional faulting developed in southern South America during the Middle Jurassic, contemporaneously with the initiation of plutonism along the present Pacific continental margin. Stratigraphic variations observed in cross sections through the silicic Jurassic volcanics along the Pacific margin of southernmost South America indicate that this region of the rift zone developed as volcanism continued during faulting, subsidence and marine innundation. A deep, fault-bounded submarine trough formed near the Pacific margin of the southern part of the volcano-tectonic rift zone during the Late Jurassic. Tholeiitic magma intruded within the trough formed the mafic portion of the floor of this down-faulted basin. During the Early Cretaceous this basin separated an active calc-alkaline volcanic arc, founded on a sliver of continental crust, from the then volcanically quiescent South American continent. Geochemical data suggest that the Jurassic silicic volcanics along the Pacific margin of the volcano-tectonic rift zone were derived by crustal anatexis. Mafic lavas and sills which occur within the silicic volcanics have geochemical affinities with both the tholeiitic basalts forming the ophiolitic lenses which are the remnants of the mafic part of the back-arc basin floor, and also the calc-alkaline rocks of the adjacent Patagonian batholith and their flanking lavas which represent the eroded late Mesozoic calc-alkaline volcanic arc. The source of these tholeiitic and calc-alkaline igneous rocks was partially melted upper mantle material. The igneous and tectonic processes responsible for the development of the volcano-tectonic rift zone and the subsequent back-arc basin are attributed to diapirism in the upper mantle beneath southern South America. The tectonic setting and sequence of igneous and tectonic events suggest that diapirism may have been initiated in response to subduction.     

Post-collisional Permian volcanism in northwestern Corsica: an assessment based on mineralogy and trace-element geochemistry

Within the Western Mediterranean Permo-Triassic province, the Scandola-Senino area represents one of the best sites for the study of the successive volcanic episodes and their relationships. With this purpose, new mineralogical and geochemical data on basic and intermediate rocks are presented.The first volcanic episode, including andesites, dacites, and rhyolitic ignimbrites of Early Permian age, is calc-alkaline with a strong LILE enrichment, particularly in K, U and Th. Andesite evolution is controlled by fractional crystallization with an important crustal component.Subsequent permian volcanism corresponds to the emplacement of bimodal volcanic products (basalt-ignimbritic rhyolite) into a caldera structure. The basalts are interpreted as derived from a mantle source still modified by subduction component.The last volcanic episode is represented by doleritic dykes derived from a within plate or OIB-type source devoid of any arc signature (no Ta anomaly).Permian magmatism in Corsica is interpreted as the progressive fading-out of an arc-signature in favour of a primitive mantle source. The magmatic features and the structural setting agree with an inferred post-orogenic geotectonic regime during the period between the Hercynian and Early Alpine orogenic events.     

Episodes of cenozoic volcanism in the circum-pacific region

The tempo of Cenozoic volcanism on opposite sides of the Pacific Ocean has been examined by compiling the numbers of radiometric dates reported for terrestrial volcanic sequences and the numbers of volcanic ash (glass) horizons recorded in Neogene deep-sea (DSDP) sedimentary sections. Within certain limits these data are believed to provide a reliable record of extrusive and explosive volcanism. Although terrestrial and marine records for individual regions reveal important differences in the episodicity of volcanism, a correlation is found between activity in the Southwestern Pacific, Central America and the Cascade Range of western North America. Two important pulses of Neogene volcanism (the Cascadian and Columbian episodes) occurred during the Quaternary (t = 2 m.y. to present) and within the Middle Miocene (t = 16 to 14 m.y. ago), with less important episodes in the latest Miocene to Early Pliocene (t = 6 to 3 m.y. ago) and Late Miocene (11 to 8 m.y. ago). The names Fijian and Andean are proposed to these episodes. Dating of terrestrial sequences indicates that these episodes of intense volcanism took place in relatively short intervals of time, separated by longer more quiescent periods.It has been suggested that synchronous episodic volcanism is related to changes in rates of sea-floor spreading and subduction. If so, volcanism must amplify these changes, because the variations in tempo of volcanism are much too great for proportional rate changes. An apparent correlation of volcanism in orogenic zones of the circum-Pacific region with world-wide changes of sea level and changes of activity in the Hawaiian-Emperor chain suggests that volcanism records fundamental tectonic changes throughout the entire Pacific region.     

Permian to recent volcanism in northern sumatra,indonesia: a preliminary study of its distribution,chemistry, and peculiarities

Sumatra has been a ‘volcanic arc’, above an NE-dipping subduction zone, since at least the Late Permian. The principal volcanic episodes in Sumatra N of the Equator have been in the Late Permian, Late Mesozoic, Palaeogene, Miocene and Quaternary.Late Permian volcanic rocks, of limited extent, are altered porphyritic basic lavas interstratified with limestones and phyllites.Late Mesozoic volcanic rocks, widely distributed along and W of the major transcurrent.Sumatra Fault System (SFS), which axially bisects Sumatra, include ophiolite-related spilites, andesites and basalts. PossiblePalaeogene volcanic rocks include an altered basalt pile with associated dyke-swarm in the extreme NW, intruded by an Early Miocene (19 my) dioritic stock; and variable pyroxene rich basic lavas and agglomerates ranging from alkali basaltic to absarokitic in the extreme SW.Miocene volcanic rocks, widely distributed (especially W of the SFS), and cropping out extensively along the W coast, include calc-alkaline to high-K calc-alkaline basalts, andesites and dacites.Quaternary volcanoes (3 active, 14 dormant or extinct) are irregularly distributed both along and across the arc; thus they lie fore-arc of the SFS near the Equator but well back-arc farther north. The largest concentration of centres, around Lake Toba, includes the >2000 km³ Pleistocene rhyolitic Toba Tuffs. Quaternary volcanics are mainly calc-alkaline andesites, dacites and rhyolites with few basalts; they seem less variable, but on the whole more acid, than the Tertiary. The Quaternary volcanism is anomalous in relation to both southern Sumatra and adjacent Java/Bali: in southern Sumatra, volcanoes are regularly spaced along and successively less active away from the SFS, but neither rule holds in northern Sumatra. Depths to the subduction zone below major calc-alkaline volcanoes in Java/Bali are 160–210 km, but little over 100 km in northern Sumatra, which also lacks the regular K₂O-depth correlations seen in Java. These anomalies may arise because Sumatra — being underlain by continental crust — is more akin to destructive continental margins than typical island-arcs such as E Java or Bali, and because the Sumatran subduction zone has a peculiar structure due to the oblique approach of the subducting plate. A further anomaly — an E-W belt of small centres along the back-arc coast — may relate to an incipient S-dipping subduction zone N of Sumatra and not the main NE-dipping zone to its W. Correlation of the Tertiary volcanism with the present tectonic regime is hazardous, but the extensive W coastal volcanism (which includes rather alkaline lavas) is particularly anomalous in relation to the shallow depth (<100 km) of the present subduction zone. The various outcrops may owe their present locations to extensive fault movements (especially along the SFS), to the peculiar structure of the fore-arc (suggested by equally anomalous Sn- and W-bearing granitic batholiths also along the W coast), or they may not be subduction-related at all.     

Geochemistry of calc-alkaline volcanic rocks from southeastern Iran (kouh-e-shahsavaran)

The Upper Tertiary to Quaternary volcanic complex of Kouh-e-Shahsavaran in southeastern Iran is composed of calc-alkaline rocks of island are type (high-alumina basalts, basic andesites, andesites and dacites) even though it was emplaced on the continental basement. The volcanic rocks of the complex are genetically related and were probably derived by low-pressure fractional crystallization of high-Al basalts. The anomalously high content of Sr in some rocks probably reflects an accumulation of plagioclase. The trace element data are consistent with the origin of the parental magma by partial melting of an “enriched” upper mantle peridotite.     

Geochronology and petrochemistry of Easter and Sala y Gomez Islands: implications for the origin of the Sala y Gomez Ridge

Easter and Sala y Gomez Islands lie along the Sala y Gomez Ridge, a broad zone of high topography and scattered seamounts extending east-southeast from the East Pacific Rise. K-Ar ages and major element abundances of volcanic rocks from these islands are used to test the fixed melting spot hypothesis for the origin of this feature. Poike volcano, the oldest center on Easter Island, was constructed in two episodes, occurring at 2.5 and 0.9 m.y. ago. Eruptive activity on Sala y Gomez was nearly contemporaneous with the earliest volcanism on Easter Island. No migration of volcanism with time is apparent along the Sala y Gomez Ridge. Basaltic rocks from Easter Island have tholeiitic affinities, while those dredged from the base of Sala y Gomez belong to an alkali olivine basalt series. Differences in basalt chemistry suggest that the volcanic rocks from the two islands formed from magmas that equilibrated at different pressures, and a model is presented which relates the character of the erupted liquids to magma segregation at the base of a progressively thickening lithosphere. The islands and seamounts comprising the Sala y Gomez Ridge do not fall on a small circle about the Nazca-mantle pole of absolute motion. Available evidence, therefore, does not support a fixed melting spot origin for Easter Island, Sala y Gomez, and the Sala y Gomez Ridge. Rather, it appears that the Sala y Gomez Ridge formed along a leaky fracture zone, and in response to a major re-orientation of spreading centers in this area.     

Origin of volcanic rocks from Stromboli (Italy)

Quaternary volcanic rocks of Stromboli (Italy) can be divided into older calc-alkaline and younger shoshonitic series. The SiO₂ contents of the rocks range from 50% to 61% but the majority of them are basalts. The rocks show systematic variations in chemical composition which correlate with the volcanic stratigraphy, such that, at a given SiO₂ content, K and other incompatible elements such as REE increase with decreasing age. In addition, the La/Yb ratio increases while the K/Rb, K/Ba, Zr/Ce and Zr/Nb ratios decrease towards the top of the volcanic pile. On the other hand, the abundances of transition elements, V, Co, Sc and Zn, like most major elements are broadly similar in comparable rocks of different ages. It is suggested that the parent magmas were derived by partial melting from upper mantle peridotite enriched in incompatible elements by fluids released from the descending oceanic lithosphere. The temporal chemical variations may probably be related to the lengths of time during which fluids were in contact with the upper mantle source.     

Quantitative petrogenetic constraints on the Pliocene alkali basaltic volcanism of the SE Spain Volcanic Province

Alkali basalts of Pliocene age are the last episode of volcanism in the SE Spain Volcanic Province, postdating a complex series of Miocene calc-alkaline to ultrapotassic rocks. This volcanism is represented by small outcrops and vents NW of Cartagena that has been interpreted as a volcanic episode similar to the contemporaneous monogenetic alkaline basaltic volcanism of the Iberian Peninsula and Western/Central Europe. However, their geochemical signature is characterised by relatively higher ⁸⁷Sr/⁸⁶Sr ratios as well as distinct trace element anomalies which, at different scale, are only found in the spatially related calc-alkaline to ultrapotassic volcanism. Quantitative modelling of these data demonstrate that the geochemical signature of the Pliocene alkali basalts of Cartagena can be explained by the interaction between primitive melts generated from a sublithospheric mantle source similar to that identified for other volcanic regions of Spain, and liquids derived from the overlying lithospheric mantle. This interaction implies that the alkali basalts show some geochemical features only observed in mantle lithosphere-derived melts (e.g. Sr isotope enrichment and Th–U–Pb positive anomalies), while retaining an overall geochemical signature similar to other Iberian basalts (e.g. Rb–K negative anomalies). This model also implies that beneath the SEVP, enriched (metasomatized) portions were still present within the lithospheric mantle after the Miocene magmatic episodes.