Mineral Water Springs Research Articles

Climatic impacts on hydrogeochemical characteristics of mineralized springs: a case study of the Garab travertine zone in the northeast of Iran

In this study, we aimed to indicate that hydrogeochemical characteristics of the mineralized spring waters of the Garab travertine zone, in the northeast of Iran, are changed in accordance of regional climatic impacts. Some 18 hydrogeological and 8 meteorological variables from documented data of Garab water samples for the years 1970, 1984, 2001, and 2011 are employed. The temporal trends show that the years 1984 and 2011 are classified as the humid and wet periods and the years 1970 and 2001 are classified as the arid and dry periods in the study area. Our results revealed that the concentrations of Ca2+, Na+, K+, Cl−, and CO32− were enhanced in the wet period by increasing carbonate precipitation and dissolution of surfacial Neogene Na–Cl soils. The recorded 8 °C difference between water temperature and air temperature can be related to thermogene conditions of spring water and thick travertine deposits, while the same variability of water temperature and air temperature in the wet and dry periods exhibits meteogene conditions of spring water and tufa generation. The hydrogeochemical analysis revealed that the abundant values of electrical conductivity (~11,000 μs/cm), total dissolved solids (~6,700 mg/l), and CO2 (~350 mg/l) together with the observed water type (Na–Cl and Ca–HCO3–SO4) are due to thermal water origin and possible leakage of fossil seawaters in deeper ground.

Immunomodulatory effects of balneotherapy with hae-un-dae thermal water on imiquimod-induced psoriasis-like murine model.

BackgroundBalneotherapy, although not a well-established dermatological treatment, is thought to have therapeutic properties for psoriasis and is used as an alternative treatment modality throughout the world.ObjectiveTo evaluate the mechanism underlying the therapeutic immunologic effects of thermomineral water.MethodsA murine model of imiquimod-induced psoriasis-like skin inflammation was used for evaluating the therapeutic effects of balneotherapy with Hae-Un-Dae hot spring mineral water. The clinical improvements were evaluated by a dermatologist. Lesional cytokines, including interleukin (IL)-17A, IL-23, and IL-22, were quantitatively measured by real-time reverse transcriptase polymerase chain reaction. Serum levels of interferon-γ, IL-4, IL-5, and IL-17A were measured by enzyme-linked immunosorbent assay. T cell proportions in the spleen were evaluated by flow cytometry, and histopathological evaluation of the skin was also performed.ResultsThe mineral water balneotherapy group showed faster improvement in skin erythema and scales than the distilled water bathing group. A substantial reduction was observed in the lesional mRNA levels of IL-17A and IL-23 in the mineral water group. Serum levels of IL-4 and IL-5 were significantly decreased in the mineral water group but not in the distilled water group. Normalized T cell proportions were observed after bathing.ConclusionBalneotherapy showed immunomodulatory effects in a psoriasis-like murine model. Balneotherapy suppressed lesional IL-23 and IL-17A, which are important cytokines in the pathogenesis of psoriasis. These results suggest that balneotherapy can be used as an effective and safe treatment for psoriasis.

Trace metal contamination of mineral spring water in an historical mining area in regional Victoria, Australia

Significant global consumption of spring and mineral water is fuelled by perceived therapeutic and medicinal qualities, cultural habits and taste. The Central Victorian Mineral Springs Region, Australia comprises approximately 100 naturally effervescent, cold, high CO2 content springs with distinctive tastes linked to a specific spring or pump. The area has a rich settlement history. It was first settled by miners in the 1840s closely followed by the first commercial operations of a health resort 1895. The landscape is clearly affected by gold mining with geographically proximal mine waste, mullock heaps or tailings. Repeated mineral springs sampling since 1985 has revealed elevated arsenic concentrations. In 1985 an arsenic concentration five times the current Australian Drinking Water Guideline was recorded at a popular tourist spring site. Recent sampling and analyses have confirmed elevated levels of heavy metals/metalloids, with higher concentrations occurring during periods of low rainfall. Despite the elevated levels, mineral water source points remain accessible to the public with some springs actively promoting the therapeutic benefits of the waters.In light of our analysis, the risk to consumers (some of whom are likely to be negatively health-affected or health-compromised) needs to be considered with a view to appropriate and verified analyses made available to the public.

Examples of applications of geothermal waters for recreation, heating and bottling in selected regions of Hungary

Due to the favourable geothermal conditions in Hungary, where the geothermal gradient is about 1.5 times greater than the world average, the country has numerous centers, which use geothermal waters directly for heating, recreation, or bottling purposes. There are plenty of thermal and mineral water springs, most of which were known even 4000 years ago. This article presents different applications of geothermal waters, illustrated with examples of spas, recreation and balneology centers like the largest spa complexes in Europe - Szechenyi Spa and 500 years old Rudas Spa located in Budapest, Egerszalok with unique travertine deposit or Miscolctapolca in the area of Miskolc where a thermal karstic cave system originally carved and dissolved by the water in karstified Triassic limestone was transformed into a complex of geothermal swimming pools. The dynamic development of the geothermal energy uses system in Veresegyhaz, which total installed thermal capacity is nearly 13 MW with the total track length of 15 km geothermal pipe line, classify the Veresegyhaz as one of the most extended geothermal systems in Hungary.

The environmental conditions of the Kavkazskie Mineralnye Vody (Caucasian Mineral Waters) health resort region, methods for their monitoring and improvement

This paper describes the unique environmental conditions of the Kavkazskie Mineralnye Vody (Caucasian Mineral Waters) health resort region with special reference to its paramount importance for the national interests of Russia. It is emphasized, however, that the environmental conditions in the region under consideration are far from being satisfactory. In connection with this, the authors point out to the necessity of expanding areas of protective forest stands and prohibition of the implementation of new building projects in the frontal mountain sanitary zones; they draw special attention to the potential danger of degradation of mineral water springs under the influence of changes in the distribution of vertical hydraulic gradients in the upper part of the lithosphere leading to the deterioration of their composition and the contamination of ground and surface waters with municipal and domestic effluents. Special attention is given to the harm and impermissibility of illegal extraction of mineral waters from producing wells. An original method for water quality control and estimation of the optimal production rate is proposed. The authors hypothesize the possible causes behind the discontinuation of mud formation at the Tambukan deposits and substantiate the necessity of using the resource-saving technologies for processing raw materials and urgent measures to eliminate the factors responsible for desalination and pollution of this mineral mud lake. It is concluded that strict state control should be exercised in the region by means of the introduction of the multilevel automated information system for round-the-clock environmental monitoring. The authors believe that only joint efforts of scientists, legislative and executive authorities can preserve Kavkazskie Mineralnye Vody health resort region for the future generations.

Hydrogeochemical Features of Some Mineral Waters at the Contact between Harghita Mts. (Eastern Carpathians) and the Transylvanian Basin

Abstract The study area, located at the contact zone between the Harghita Mountains and the Transylvanian Basin is well known for the abundance and diversity of mineral water springs. These mineral waters are used by the local people for drinking and also as Spas. This paper focuses on the mineral waters of some traditional Spas from this area, Odorheiu Secuiesc (Seiche Spa, Kapolnas Spa or Solymossy Spa), Upper Vârghis Valley (Selters Spa and Nadasszek Spa) and Chirui Spa. The aim of the present work is to characterize the mineral waters based on the quantification of chemical content and also to establish correlations between the geological structure and the water's chemical composition. The geological setting and tectonics have a large influence on the chemical composition of mineral waters. Two main water types can be described, mineral waters of Na+ – Cl- type, present at Odorheiu Secuiesc, Kapolnas Spa and of HCO3- type with no dominant cation at Chirui Spa. The mineral waters located on a fault at Odorhei Seiche Spa have high CO2 values. Possible mixing zones might be identified between the two types which are present in the Upper Vârghis Valley where mineral waters of Na+ – HCO3-– Cl- type are present except one source, which is of Na+ – Cl- type. The mixing is reflected not only by the chemical composition, but also by the quantity of dissolved CO2. The present paper deals with all the existing mineral water springs in the area providing information in a high resolution about the local hydromineral system.

Sviluppi del turismo e dei centri abitati a Courmayeur e nell'area della Valdigne

Courmayeur and the towns and villages of Valdigne, historical tourist and bathing centres thanks to their mineral water springs, now constitute an appendage of the large cities of the Po Valley megalopolis. The development of tourism has heavily remodelled the settlement and functional characteristics of the inhabited centres. Hotels and ancient aristocratic homes transformed into condominiums stand in an imposing landscape of holiday homes. A blurred conurbation bonds together the old mountain villages. Trade and service businesses ‘chase’ the fluctuating affluent population. The perspective of an ‘active geography’ allows the interpretation of the ‘tourist district’ character of Valdigne to be abandoned to trigger a local debate on policies which will ensure compatible tourism development: a metric of quality must replace that of quantity which dominated in the past.

Investigation of mineral water springs of Miercurea Ciuc (Csíkszereda) region (Romania) with cultivation-dependent microbiological methods

Water samples of ten mineral water springs at Miercurea Ciuc (Csíkszereda) region (Romania) were examined during 2005-2006 using cultivation-dependent microbiological methods. The results of standard hygienic bacteriological tests showed that the Hargita Spring had perfect and five other springs had microbiologically acceptable water quality (Zsögöd-, Nagy-borvíz-, Taploca-, Szentegyháza- and Lobogó springs). The water of Borsáros Spring was exceptionable (high germ count, presence of Enterococcus spp.).Both standard bacteriological and molecular microbiological methods indicated that the microbiological water quality of the Szeltersz-, Nádasszék- and Délo springs was not acceptable. Bad water quality resulted from inadequate spring catchment and hygiene (low yield, lack of runoff, negligent usage of the springs, horse manure around the spring).The 16S rRNA gene-based identification of strains isolated on standard meat-peptone medium resulted in the detection of typical aquatic organisms such as Shewanella baltica, Aeromonas spp., Pseudomonas veronii, Psychrobacter sp,. Acinetobacter spp. and allochthonous microbes, like Nocardia, Streptomyces, Bacillus, Microbacterium , and Arthrobacter strains indicating the impact of soil. Other allochthonous microbes, such as Staphylococcus spp., Micrococcus sp., Lactococcus sp., Clostridium butyricum, Yersinia spp., Aerococcus sp., may have originated from animal/human sources.

Radon in groundwater and dose estimation for inhabitants in Spas of the Sudety Mountain area, Poland

Studies of radon isotope (222)Rn activity concentration in underground water in the Sudety region were performed with the use of the liquid scintillation technique. Waters chosen for investigations were collected in 24 health resorts and towns of the Sudety area from 115 springs, wells and intakes. The (222)Rn activity concentration varied within the range from 4.2+/-0.4 to 1703+/-55 Bq/l. The annual effective doses due to the consumption of (222)Rn with water were calculated for 50 sources of underground spring water or tap water used for consumption. The results were within the range from 0.003 to 1.1 mSv/yr, assuming 0.5 l of tap water per day from which radon is not removed or 0.5 l of mineral spring water consumed daily. The contribution to the effective dose from the inhalation of radon during the daily usage of domestic water substantially increases its effective dose.

Natural radioactivity in underground water from the Outer Carpathians in Poland with the use of nuclear spectrometry techniques

The investigations of natural radioactivity in underground mineral water and spring water in health resorts in the Outer Carpathians were performed. Samples from 40 water springs were collected 3-4 times over a period of 10 years (1997-2007). In order to obtain necessary data, two different nuclear spectrometry techniques were applied: WinSpectral alphabeta 1414 liquid scintillation counter from Wallac and alpha-spectrometer 7401 VR from Canberra-Packard, USA with the silicon surface barrier detector. The activity concentrations of (222)Rn in the investigated samples varied from below 1 to 50 Bq/l. For radium isotopes the concentrations were in a range from below 10 to 490 mBq/l for (226)Ra and from 29 to 397 mBq/l for (228)Ra. The highest concentrations for both radium isotopes were obtained for medicinal water Zuber III from Krynica spa. The activity concentrations for uranium isotopes varied from below 0.5 to 16 mBq/l for (238)U and from below 0.5 to 162 mBq/l for (234)U with the highest values obtained for water Zuber IV. The highest annual effective dose arising from mainly radium isotopes was obtained for Zuber III water and was equal to 75 microSv/yr. Additionally, the annual effective doses due to (222)Rn consumed with water were also estimated. The isotopic ratios between isotopes originating from the same decay chain ((234)U/(238)U, (226)Ra/(238)U) and from different radioactive decay chains ((226)Ra/(228)Ra) were determined. The correlations between different isotopes were presented.

Long-lived center of youngest volcanism in the Borzhomi region of Georgia: Isotopic-geochronological evidence

One of the well-known areas with youngest volcanism in the Lesser Caucasus is located in the vicinity of the Borzhomi City (central Georgia) famous by mineral water springs. This relatively small area hosts four volcanoes (Tsitelidabadzveli, Tsikhisdzhvari, Mukhera, and Sargavi), which yielded extended (from 2 to 13 km long) flows of andesite to, subordinate, basaltic andesite lavas (figure). In scientific works dedicated to different aspects of Neogene‐Quaternary magmatism of the Caucasus region, manifestations of basaltic andesite‐andesite volcanism in the examined part of the Lesser Caucasus mountainous system are usually united into the Bakuriani‐Borzhomi neovolcanic area [1 and others]. It is composed of Upper Cretaceous carbonate bands, Paleocene‐Lower Eocene terrigenous rocks of the Borzhomi series, and Middle Eocene‐Oligocene volcano-sedimentary sequences. Young lava flows a few tens of meters thick known in this area lie with stratigraphic and angular unconformities upon the Paleogene basement spreading over significant part of studied territory (Fig. 1). It should be noted that, according to the recent tectonic map of Georgia [2], magmatic activity in the Bakuriani‐Borhomi area was concentrated in the Adzharia‐Trialeti zone of the Lesser Caucasus fold system with volcanoes confined to the linear near-latitudinal Bakuriani abyssal fault zone at its intersection with the meridional Samsari Fault. Tsitelidabadzveli Volcano (2320 m) is located on the northern slope of the Trialeti Range 12 km south of Borzhomi. It represents an oval meridionally extended edifice up to 100 m high composed of pyroclastics (scoria, breccia, lapillis) with subordinate interbeds of dark gray and reddish lavas. Basaltic andesite lava flows erupted by this volcano fill a spacious depression 8 × 6 km in size and form the Dabadzveli Plateau, the surface of which is located at altitudes of 2100 to 1600 m and is slightly inclined in the northern direction toward the Kura River valley. Basaltic andesites of the Tsitelidabadzveli Volcano (samples YUG-156 from the volcano cone and YUG-157 from lavas of the Dabadzveli Plateau) represent massive to vesicular porphyric to subordinate aphyric rocks. Phenocrysts in porphyric varieties are dominated by plagioclase (labradorite) and clinopyroxene (augite) accompanied by subordinate orthopyroxene (hypersthene) and olivine. Tsikhisdzhvari Volcano (1818 m) is located 2.5 km

Study of mineral water resources from the Eastern Carpathians using stable isotopes

The Eastern Carpathians contain many mineral water springs that feed famous Romanian health resorts such as Borsec, Biborteni and Vatra Dornei. These waters have been used for their different therapeutic effects. In this work, mineral and spring waters from these Romanian regions were investigated by means of chemical and isotopic (deltaD and delta(18)O) analyses in order to understand the recharge mechanisms and also to determine their origins. Most of the investigated springs are of meteoric origin, having the average deuterium content of the local meteoric water. The higher (18)O content with respect to the Meteoric Water Line (MWL) indicated an exchange reaction with crystalline igneous rocks at depth and with other rocks that the water encounters on its journey back to the surface.

Cu(II)-imprinted styrene–divinylbenzene beads as a new sorbent for flow injection-flame atomic absorption determination of copper

The paper reports preparation and analytical features of a new Cu(II)-imprinted polymer, based on salen-OMe ligand 2,2′-[ethane-1,2-diylbis(nitrilo( E)methylylidene)]bis(6-allyl-4-methoxyphenol) and styrene–divinylbenzene matrix, as well as its application to on-line preconcentration and flame atomic absorption determination of copper. Sorbent beads (average diameter of 60–80 µm) were obtained using suspension polymerization technique and employed as a column filling. Copper sorption was the most effective at pH 6.8, whereas the highest elution effectiveness was observed when 0.5% HNO 3 was applied. The sorbent exhibited good long-term stability and acid resistance. Enrichment factor (EF) of 12 was found for 60 s loading time and loading flow rate of 4 mL min − 1 . EF value may be further increased by expanding the loading time and/or flow rate. Batch sorbent capacity in optimal pH conditions was found to be 0.16 mmol g − 1 (9.55 mg g − 1 ) of a dry polymer. Calcium(II) turned out to be the only significant interferent. Cadmium(II), silver(I), nickel(II), zinc(II) in concentrations lower than about 1 mg L − 1 did not disturb copper(II) preconcentration. Different calibration methods such as: set of standards method (SSM), standard addition method (SAM) and combinatory calibration method (CCM) were employed for copper(II) determination in tap water, spring mineral water and certified reference material. Analysis of EU-H-3 reference material confirmed good accuracy of the proposed method. Relative standard deviation (RSD) was 3.2 for standard addition method and 2.8% for set of standard calibration method. Detection limit for sample consumption 16 mL was 1.03 and 1.07 µgL –1 respectively.

Current state of a mineral water spa and a health resort complex in the Republic of Bashkortostan and prospects for its further development

The objective of this study was to consider natural conditions and mechanisms of formation of mineral water sources in the Republic of Baskortostan. A map showing their location within the bounds of the Republic lying at the junction of Europe and Asia is presented. The distribution of mineral water springs is highly non-uniform and dictated by the landscape patterns, climatic, geologic and tectonic history of the territory, its climatic and hydrological conditions. It is concluded that most part of Bshkortostan has very promising prospects for the further development of its spa and resort complex.

Natural radioactivity of 226Ra and 228Ra in thermal and mineral waters in Croatia

Thermal waters are known as valuable natural resources of a country. They contain certain degree of natural radioactivity attributable to the elements of the uranium and thorium natural decay series. Among these elements, the most radiotoxic and the most important is radium that exists in several isotopic forms (226Ra and 228Ra). The focus of attention was the content of radium in samples of thermal and mineral spring water from several spas in Croatia. These waters are mainly used for medical, bathing and recreational purposes, and some of them are used for drinking. Measured activity concentrations of 226Ra ranged from 87 to 6200 mBq l(-1) which, in some springs, exceed the maximal permissible level of 1 Bq l(-1) for drinking water. Measured activity concentrations of 228Ra ranged from 23 to 3480 mBq l(-1). The study showed that radium content for the investigated thermal and mineral waters is below the levels at which negative consequences would arise due to ingestion.

The San Vittorino Sinkhole Plain: relationships between bedrock structure, sinking processes, seismic events and hydrothermal springs

The San Vittorino Plain is located along the Velino River Valley within an intermontane depression, filled with continental deposits. This plain is characterized by the presence of numerous sinkholes, often filled with mineralized spring waters. From a structural point of view, the study area is characterized by four tectonic units with different paleogeographical evolution and deformation styles. From the innermost unit they are: the Reatini Unit, the Navegna Unit, the Salto Unit, and the Nuria Unit. The main tectonic lineaments are represented by the Anzio-Ancona line, the Olevano-Micciani line, the Fiamignano-Micciani Fault and the Cerquara-Piedimozza Fault. The development of sinkholes in the study area is mainly due to deep suffusion and deep piping processes, linked to fluid upwelling along fracture-fault systems and to dissolution (by H2S and CO2) in the continental deposits. The sinkhole distribution suggests that they are mainly formed in a collapsed sector of the Mt. Paterno block whose structural setting, characterized by several splays, with marly-clayey and siliciclastic deposits at the footwalls, favoured the development of confined aquifers. The rise of groundwater to the surface along the network of faults and fractures crossing the carbonate bedrock is likely controlled by hydrostatic pore pressures, which may be strongly increased by earthquake shaking. The surface distribution of sinkholes in the San Vittorino Plain, showing differences within the study area, is strictly linked to the bedrock structure and the related hydrogeological setting, as demonstrated by the detailed survey carried out in the area.

Hepburn Spa: cold carbonated mineral waters of Central Victoria, South Eastern Australia

Hepburn Spring is the major cold carbonated mineral spring of the ‘Spa’ country of Central Victoria, in South Eastern Australia. The spring occurs in a small tributary valley of the Loddon River, 15 km away from the crest of the Great Dividing Range. The waters are effervescent, have an alkalinity of around 1,500 mg/L (as HCO3−), are mildly acidic and have high iron concentrations. Hepburn Spring is one of nearly 100 small cold low flow carbonated mineral water springs that occur in the region. Hepburn Spring has been protected since 1865 in one of 34 ‘Special Mineral Spring Reserves’. By world standards the spring is small and not highly developed, but it retains much of its charm due to the bushland, forest setting. The bedrock of the region consists of indurated arkosic sandstones interbedded with carbonaceous shales and slates. The rocks are folded and cut by swarms of strongly developed meridional fissure fault systems. Hepburn Spring is situated on the fault and fold axes associated with the “Cornish line” and Gold mines have dewatered the spring on several occasions. After dewatering events the water level and flow recovered first and then the water composition and effervescence. The origin of the effervescent waters has attracted much attention; hypotheses include both a volcanic and a rock water reaction origin. The second hypothesis involves weathering of the carbonaceous and sometimes pyritic rock mass which contains only a few percent carbonate. This process produces high bicarbonate groundwater throughout Central Victoria. The Hepburn waters are a variant of these waters and it is suggested that controls on the carbonate solubility and redox conditions in the fissures flow systems results in effervescent waters as the waters ascend.

Anion chromatography and redox photometry in potable water analysis

Anion chromatography with ANIEKS-N selective ion exchanger and redox photometry with an antimony(V) ionic associate as selective oxidizing agent were suggested for determination of low concentrations of toxic (F−, Br−, NO2−, NO3−) and biogenic (SeO32−, I−) ions in some potable waters available from central water supply systems and mineral water springs.

Formation processes of thermal waters in Green Tuff: A geochemical study in the Hokuriku district, central Japan

Thermal waters from Green Tuff region in the Hokuriku district, central Japan were investigated to reveal formation process of water, based on the chemical and isotopic compositions of water and dissolved gases in water. The thermal waters of local meteoric origin are typical Green Tuff-type water, Na–Ca–Cl–SO 4-type or Na–Cl–SO 4-type, which well reacted by water–rock interaction and is found to be saturated with calcite and undersaturated with gypsum. The Green Tuff-type waters have relatively high 3He/ 4He ratio indicating high contribution of mantle-derived helium, and have extremely low total carbon/ 3He (Ct/ 3He) ratio compared with the ratio of MORB due to removal of carbon species from waters caused by calcite deposition. In contrast, a mineral spring water close to an active fault is found to be an immature water with less water–rock interaction containing a large amount of gaseous CO 2 and is undersaturated with both calcite and gypsum. This water has high 3He/ 4He ratio and Ct/ 3He ratio indicating the high contribution of mantle-derived helium and deep-seated CO 2, and likely provided through the fault. We proposed a chemical evolution model considering existence of both chemically immature CO 2 gas-rich water and mature carbon-poor water which well reacted with rocks. Deep-seated CO 2 and mantle-derived helium are upwelling via faults and are supplied to the groundwater of local meteoric origin, and an immature water containing high content of CO 2 and mantle-derived helium is formed. During the circulation of this immature water in the Green Tuff layers, water–rock interaction such as ion exchanges with minerals, dissolution of gypsum and deposition of calcite occurred. At the interaction with rocks, deposition of calcite occurs and results in a loss of Ca 2+, and decrease of Ca 2+ brings dissolution of gypsum and more calcite deposition. Consequently, almost all the supplied CO 2 is eliminated from the water. Furthermore, we made a quantitative evaluation of the chemical evolution of Green Tuff-type water using geochemical modeling code PHREEQC taking account of addition of gas components, and found the good agreement with observational results. This study reveals that the supply of large amounts of CO 2 and subsequent water–rock interaction are necessary for the formation of “Green Tuff-type” water with high 3He/ 4He ratio and extremely low Ct/ 3He ratio.

Cenozoic behind-arc volcanism in the Bolivian Andes, South America: implications for mantle melt generation and lithospheric structure

We develop a model of arc and behind-arc volcanism, as well as constraining the evolution of the lithospheric mantle structure beneath the Bolivian Andes during the last 25 Ma, using new geochronological and geochemical data on behind-arc mafic volcanic rocks, together with a regional isotopic study of geothermal helium emissions, and a comparison with seismic tomographic images of the same region. Helium isotopes measured in natural gas emissions in geothermal and mineral-water springs suggest recent mantle melting in a wide zone extending at c . 20°S from a few tens of kilometres west of the volcanic arc to over 300 km behind the arc, where the subducted slab is at depths increasing from c . 100 to c . 250 km. During the Neogene, there has been behind-arc mafic–felsic magmatism right across the high Andes between 17° and 22°S, in the Altiplano and western margin of the Eastern Cordillera. Modelling of Plio-Pleistocene basalts and basaltic andesites (<5.2 Ma), using REE, suggests that the main melt source region is in spinel and spinel–garnet peridotite, at depths <100 km. In detail, the best-fit REE inversions suggest two spatially distinct melt zones: (1) a c . 15% depleted mid-ocean ridge basalt (MORB) source at depths between c . 75 km and c . 110 km for mafic volcanic rocks that crop out <75 km behind the arc; (2) a slightly enriched MORB source at depths between c . 65 km and c . 90 km for those that crop out >100 km behind the arc. REE inversions for Oligo-Miocene shoshonites and basalts ( c . 25–21 Ma) suggest that they originated at significantly shallower depths ( c . 45 km to c . 100 km) from a slightly enriched MORB source. Eruption of shoshonitic lavas also occurred in the Altiplano between 13 and 11 Ma, and widespread behind-arc intermediate–felsic volcanism has been more or less continuous since the early Miocene. All this suggests that since c . 25 Ma there has been a thin (<100 km) lithosphere beneath the high part of the Bolivian Andes. Long-lived mantle melting is best explained by wet adiabatic decompression in the upwelling part of the corner flow in the mantle wedge, controlled by the lithospheric thickness variations, with depleted melt advected into the melt zone beneath the arc. Widespread arc and behind-arc magmatism may have been triggered at c . 25 Ma by the opening up of a mantle wedge and inflow of hot asthenosphere, as a consequence of the steepening of the subducted slab and detachment of hydrated and weakened mantle lithosphere and possibly mafic lower crust.