http://hdl.handle.net/2122/181 Sun, 19 May 2013 22:24:10 GMT 2013-05-19T22:24:10Z http://hdl.handle.net/2122/8681 Title: Geochemistry of free and dissolved gases in the Amik basin area (Turkey) and its relationships with the tectonic setting Authors: Galip, Y.; Eskisehir Osmangazi Üniversity, Turkey; Italiano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Yang, T.F.; National Taiwan University, Taiwan; Yalcin, T.H.; Istanbul Technical University, Turkey; Rojay, B.; Middle East Technical University, Ankara, Turkey; Gulbey, A.H.; Eskisehir Osmangazi Üniversity, Turkey; Yasin, D.U.; skisehir Osmangazi Üniversity, Turkey; Ozacar, A.; Middle East Technical University, Ankara, Turkey; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Fu, C.-C.; National Taiwan University, Taiwan; Lai, C.-W.; National Taiwan University, Taiwan Abstract: Twenty-two gas samples were collected in August 2012 in the area of Amik basin (Turkey). Two samples were collected from gas seeps, one was a bubbling gas in a thermal spring, while the remaining were dissolved gases from cold and thermal groundwaters (T 16-43 °C). All gases were analysed for their chemical composition (He, H2, O2, N2, CH4 and CO2) and for their He isotopic composition. Dissolved gases were also analysed for the carbon isotopic composition of the total dissolved carbon (TDC), while free gases also for their higher hydrocarbon (C1 – C5) content and for D of H2 and CH4, 13C of CH4 Basing on their chemical composition, the gases can be roughly subdivided in three groups. Most of the dissolved gases (16) belonging to the first group were collected from springs or shallow wells (< 150 m depth). All these samples contain mainly atmospheric gasses with very limited H2 (< 80 ppm) and CH4 (1 – 2700 ppm) contents and minor concentrations of CO2 (0.5 – 11.2 %). The isotopic composition of TDC evidences an almost organic contribution. The only exception is represented by the CO2-richest sample where a small but significant mantle contribution is found. Such contribution can also be evidenced in its 3He rich isotopic composition. Further three samples of this group evidence a small mantle contribution. These samples were collected in the northern part of the basin along the main tectonic structures delimiting the basin and close to areas with quaternary volcanic activity. A second group is composed by two dissolved gases collected from deep boreholes (> 1200 m depth). Their composition is typical of hydrocarbon reservoirs being very rich in CH4 (> 78 %) and N2 (> 13%). Also the water composition is typical of saline connate waters (Cl- and B-rich, SO4-poor). C-isotopic composition of methane ( 13C -65% ) points to a biogenic origin while He-isotopic composition indicates a prevailing crustal signature for one (R/Ra 0.16) of the sites and small mantle contribution for the other (R/Ra 0.98). To the last group belong four gas samples taken at two sites within the ophiolitic basement that crops out west of the basin. These gases have the characteristic composition of gas generated by low temperature serpentinisation processes with high hydrogen (37 – 50 %) and methane (10 – 61 %) concentrations. While all gases show an almost identical D-H2 of -750h those of one of the two sites display an isotopic composition of methane ( 13C -5h D -105% ) and a C1/[C2+C3] ( 100) ratio typical of abiogenic hydrocarbons and mantle-type helium (R/Ra: 1.33), while those of the other site evidence a contribution of a crustal (thermogenic) component ( 13C-CH4 -30h D -325h C1/[C2+C3] 3000). Such crustal contribution is also supported by higher N2 contents (40% instead of 2%) and lower He-isotopic composition (R/Ra 0.07). The preliminary results highlight contributions of mantle-derived volatiles to the fluids vented along the Amik Basin. The main tectonic structure of the area, the Death Sea Fault, and other parallel structures crossing the basin seem to be the responsible for deep-originated volatiles drainage towards shallow levels. Sun, 07 Apr 2013 22:00:00 GMT http://hdl.handle.net/2122/8681 2013-04-07T22:00:00Z http://hdl.handle.net/2122/8679 Title: The fluids’ geochemistry along the "Sperchios Basin - Northern Evoikos Gulf" Graben, a geodynamically complex area of Central Greece Authors: D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Calabrese, S.; Università di Palermo, Dipartimento DiSTeM; Kyriakopoulos, K.; University of Athens, Dept. Geology and Geoenvironment, Greece Abstract: The study area is a 130 km long fast spreading graben in Central Greece. Its complex geodynamical setting includes both the presence at depth of a subduction slab responsible for the recent (Quaternary) volcanic activity in the area and the western termination of a tectonic lineament of regional importance (the North-Anatolian fault). Its high geothermal gradient is evidenced by the presence of many thermal springs with temperatures from 19 to 82 C, issuing along the normal faults bordering the graben. In the period 2004-2012 about 50 gas and water samples have been collected and their chemical and isotopic analysis revealed a wide range of compositions. Going from west to east the gas composition changes from CH4- to CO2-dominated passing through mixed N2- CH4 and N2-CO2 compositions, while at the same time the He isotopic composition goes from typical crustal values (0.05 R/Ra) up to 0.87 R/Ra (corrected for air contamination), showing in the easternmost sites a small but significant mantle input. Isotopic composition of CH4-C indicates a thermogenic origin for the CH4-rich samples and hydrothermal origin for the remaining samples. Positive 15N values indicate a contribution of crustal derived nitrogen for the N2-rich samples. The 13C values of most the CO2-enriched samples show a mixed origin (mantle and marine carbonates). Also the chemical composition of the waters shows differences along the graben and two main groups can be separated. The first, represented by dilute waters (E.C. < 600 S/cm), is found in the westernmost sites characterised by the presence of CH4-rich and mixed N2-CH4 gases. The remaining waters display higher salinities (E.C. from 12 to 56 mS/cm) due to the mixing with a modified marine component. Only the water composition of easternmost sites in the Giggenbach’s cation triangular graph plots in the field of the partially equilibrated waters giving estimated temperatures at depth of 150-160 C. Sun, 07 Apr 2013 22:00:00 GMT http://hdl.handle.net/2122/8679 2013-04-07T22:00:00Z http://hdl.handle.net/2122/8539 Title: Fluid geochemistry along the Eliki and Aigion seismogenic segments (Gulf of Corinth, Greece) Authors: Pizzino, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Quattrocchi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Cinti, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Galli, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: Three geochemical surveys in ground waters were carried out in the Selianitika–Trapeza area, Gulf of Corinth, with the main purposes: (1) to define the geochemical patterns of the circulating ground waters; (2) to discriminate the role of active fault systems in affecting the ground water chemistry and hydrogeology, exploiting geochemical techniques tested in other areas; (3) to select sites for the continuous geochemical surveillance of the tectonic activity of the area. A total of 50 sites have been sampled, and numerous chemical and stable isotope analyses have been performed. We identify three geochemical active fault zones: (i) the Eliki–Nikolaikea area; (ii) the Selianitika–Rododafni–Nerazes area, and (iii) the Trapeza sector. The Nerazes well site and the Selianitika spa have been selected for exploiting a geochemical-hydrological monitoring surveillance of the tectonic activity. Wed, 20 Mar 2013 23:00:00 GMT http://hdl.handle.net/2122/8539 2013-03-20T23:00:00Z http://hdl.handle.net/2122/8497 Title: Are the Salinelle mud volcanoes threatening human health or are anthropogenic activities threatening the Salinelle mud volcanoes? A comment on “Trace element biomonitoring using mosses in urban areas affected by mud volcanoes around Mt. Etna. The case of the Salinelle, Italy” by Bonanno et al. (DOI 10.1007/s10661-011-2332-z) Authors: D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Calabrese, S.; Università di Palermo, Dipartimento DiSTeM Abstract: no abstract Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8497 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8404 Title: Another kind of “volcanic risk”: the acidification of sea-water. Vulcano Island (Italy) a natural laboratory for ocean acidification studies Authors: Boatta, F.; Università di Palermo, Dipartimento DiSTeM; D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Gagliano, L.; Università di Palermo, Dipartimento DiSTeM; Calabrese, S.; Università di Palermo, Dipartimento DiSTeM; Liotta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Milazzo, M.; Università di Palermo, Dipartimento DiSTeM; Parello, F.; Università di Palermo, Dipartimento DiSTeM Editors: Corsaro, R.A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: Acidification of seawater is one of the aspect tightly linked to volcanic risk, due to the presence of submarine vents releasing abundant volcanic fluids. In aquatic system CO2 gas dissolves, hydrates and dissociates to form weak carbonic acid, which is the main driver of natural weathering reactions [Drever, 1997]. The result of the CO2 increase is seawater acidification. Vulcano Island, the southernmost of Aeolian Islands, is located in the Southern Tyrrhenian Sea (Italy), approximately 18 miles off the NE coast of Sicily. The Baia di Levante can be considered a natural laboratory where almost all of the biogeochemical processes related to the ocean acidification can be studied. In this area many submarine vents release CO2. Four geochemical surveys of the Bay were carried out in April - September 2011 and May - June 2012. The main physic-chemical parameters (T, pH, Eh, electric conductivity) were measured at more than 70 sites and more than 40 samples for chemical analyses were collected at representative points. Major (Na, K, Mg, Ca, Cl, SO4) and some minor components (B, Sr, Fe) and trace elements (Mn, Mo, Al, U, Ce, Pb, Tm, Tb, Nd, Th) dissolved in water, the chemical composition of dissolved gases (He, H2, O2, N2, CH4 and CO2) and the isotopic composition of total dissolved inorganic carbon were determined in the laboratory. The bubbling CO2 produces a strong decrease in pH from the normal seawater value of 8.2 down to 5.5 (Figure 1). In the area close to the main degassing vents, characterized by very low pH, macroorganisms were absent. Acidification of sea water is one of the aspect tightly linked to volcanic risk, due to the presence of submarine vents releasing abundant volcanic fluids. At Baia di Levante, about 300 m from the main vents the seawater is only slightly acidic (pH 6.5 - 7.0) resembling the ocean water conditions in equilibrium with the high atmospheric CO2 concentrations expected in the near future. Therefore environments like this, naturally enriched in CO2, are good laboratories to study the consequences of ocean acidification on aquatic biota [Doney et al., 2009]. Furthermore acidification is tightly linked with the mobility and bio-availability of heavy metals [Millero et al., 2009] in sea water and volcanoes were always the favourite choice for human settlements; as a consequence economic anthropological activity, such as fishing, could be dangerous for human health, because of the presence toxic level of trace metals in the food chain due to the presence of the volcano’s. The present study could provide important information about the best environmental management of volcanic areas such as Vulcano Island Tue, 11 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8404 2012-12-11T23:00:00Z http://hdl.handle.net/2122/7949 Title: Nitrate, sulphate and chloride contents in public drinking-water supplies in Sicily, Italy Authors: D'Alessandro, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Bellomo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Parello, F.; Università di Palermo, Dipartimento CFTA; Bonfanti, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Brusca, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Longo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Maugeri, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia Abstract: Water samples collected from public drinking-water supplies in Sicily were analysed for electric conductivity and for their chloride, sulphate and nitrate contents. The samples were collected as uniformly as possible from throughout the Sicilian territory, with an average sampling density of about 1 sample for every 7600 inhabitants. Chloride contents that ranged from 5.53 to 1302 mg/l were correlated strongly with the electric conductivity, a parameter used as a proxy for water salinity. The highest values are attributable to seawater contamination along the coasts of the island. High chloride and sulphate values attributable to evaporitic rock dissolution were found in the central part of Sicily. The nitrate concentrations ranged from 0.05 to 296 mg/l, with 31 samples (4.7% of the total) exceeding the maximum admissible concentration of 50 mg/l. Anomalous samples always came from areas of intensive agricultural usage, indicating a clear anthropogenic origin. The same parameters were also measured in bottled water sold in Sicily, and they all were within the ranges for public drinking-water supplies. The calculated mean nitrate intake from consuming public water supplies (16.1 mg/l) did not differ significantly from that of bottled water (15.2 mg/l). Although the quality of public water supplies needs to be improved by eliminating those that do not comply with the current drinking-water limits, at present it does not justify the high consumption of bottled water (at least for nitrate contents). Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/7949 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7628 Title: The emergence of ocean biogeochemical provinces: a quantitative assessment and a diagnostic for model evaluation. Authors: Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Allen, J. I.; PML; Masina, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Hardman-Mountford, N.; PML Abstract: The concept of ocean biogeochemical provinces is based on the observation that large ocean regions are characterized by coherent physical forcing and environmental conditions, which are eventually representative of macroscale ocean ecosystems. Biogeochemical models of the global ocean focus on simulating the coupling between prevalent physical conditions and the biogeochemical processes with the assumption that biological properties respond coherently to physics and therefore should produce such provinces as an emergent property. In this paper, we quantitatively assess the emergence of a reference set of predefined biogeochemical provinces in the available global data sets and propose a province‐based approach to the evaluation of one of the most comprehensive models of ocean biogeochemistry. Multivariate statistical tools were applied to model and observation data, verifying the existence, distinctiveness and reliability of the predefined provinces and quantifying the correlation of model results with observations at the global scale. The analysis of similarity between provinces shows that they are statistically separable in data and model output and therefore can be used as reliable metrics. The analyses indicate that provinces can be more easily distinguished in terms of their environmental features rather than using chlorophyll concentration. The characterization of provinces by means of chlorophyll values shows a significant overlap in both the Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS) data and the model. It is likely this is related to the choice of province boundaries based on coarse‐resolution mapped data, which are not necessarily the same as those derivable from high‐resolution satellite data. We also demonstrated through cluster analysis that the long‐term time series data collected at Joint Global Ocean Flux Study (JGOFS) stations are representative of environmental conditions of the respective province and can thus be used to evaluate model results extracted from that province. The method shows promise for helping to overcome problems with model verification due to under sampling of most ocean biogeochemical variables but also gives indications that unsupervised clustering may be required when more spatially resolved data and models are available. Fri, 31 Dec 2010 23:00:00 GMT http://hdl.handle.net/2122/7628 2010-12-31T23:00:00Z http://hdl.handle.net/2122/7472 Title: Geochemistry of groundwater from Graciosa Island (Azores): A contribution to the hydrothermal system conceptual model Authors: Carvalho, M.R.; 1Universidade de Lisboa, Faculdade de Ciencias, Depart. Geologia/CeGUL, Portugal; Carreira, P.; Instituto Tecnologico e Nuclear, Lisboa, Portugal; Marques, J.M.; Instituto Superior Tecnico, Lisboa, Portugal; Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Nunes, J.C.; Universidade dos Açores & INOVA Inst., Azores, Portugal Abstract: Graciosa island is located in the Azores Archipelago, along the so-called Terceira Rift, a major tectonic structure that makes the NE boundary of the Azores Plateau. In general terms, it includes a basaltic plataform on the NW and a silicic poligenetic volcano with caldera on the SE, the Graciosa Caldera Volcano. This volcano has produced significant tephra falls, pyroclastic flows, lahars, and lava flows, both of basaltic s.l. and trachitic s.l. composition. The hydrothermal system shows fumarolic emissions inside the volcano caldera and thermal springs located along the shoreline. This system is exploitated in a thermal building through shallow and deep (110 m) boreholes, near the coast. In Graciosa two types of Na-Cl groundwater systems can be identified: 1) a cold one emerging at springs and exploited by wells for public water supply, and 2) a hydrothermal system with temperatures around 40-44 °C. The cold groundwaters have pH higher than 7 and different degree of mineralization, according to the proximity to the sea. The thermal waters show mixing with seawater, pH varying between 6.20 and 6.94, 166 mg/L of SiO2, and significant concentration of metals, such as Mn, Fe, Co, Ni, Cu and Zn. The thermal water mineralization varies strongly, showing EC from 8.87 mS/cm (shallow water) to 47.4 mS/cm (deeper water). The higher mineralized water is rich in CO2(g), with 2130 mg/L of total dissolved CO2. Geothermometers application reveals aquifer temperature around 167 °C and immature/mixed waters, not reaching complete equilibrium with reservoir rock. The geochemistry of the thermal waters indicates the occurrence of seawater/host rock interaction processes at high temperature and slightly acid conditions, favored by CO2(g) input, and a different degrees of mixing with cold and shallow groundwaters. Sat, 13 Aug 2011 22:00:00 GMT http://hdl.handle.net/2122/7472 2011-08-13T22:00:00Z http://hdl.handle.net/2122/7468 Title: Helium isotopes distribution in NW Iberian peninsula: evidences of a local neotectonic activity Authors: Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Carreira, P.; Instituto Tecnológico e Nuclear, Sacavém, Portugal; Carvalho, M.R.; Universidade de Lisboa, Faculdade CienciasDpt. Geologia, Lisboa; Marques, J.M.; Instituto Superior Técnico, Lisboa; Antunes da Silva, M.; UNICER Bebidas, S.A. S. Mamede de Infesta Editors: Demény, Attila; Instute for geochemical research, Hungarian Academy of Sciences Abstract: In this work we report new data on He abundances and isotope ratios (3He/4He) from gas associated to some thermal and CO2-rich mineral waters in N-Portugal. Collected gas samples are mainly CO2-dominant except two sites where gas is N2-rich. All the sampling sites are characterized by exceptionally high helium contents with 3He/4He ratios, corrected for air contamination, varying considerably from 0.09 to 2.68 Ra. In all sites, the 3He/4He ratios are higher than that typical for stable continental areas thus indicating a variable but not-negligible (up to 30%) contribution of mantle-derived primordial He. In all the CO2-rich waters, CO2/3He ratios and 13CCO2 are comparable with mantle values, thus suggesting a magmatic origin also for CO2. On the contrary, in the N2-rich waters He is mainly radiogenic, and CO2 is organic in origin. Since no recent volcanic activity is observed in NW Iberia, high 3He/4He values could be due, at least, to three processes: a) releasing of gas from the local upper mantle through deep extensional fault systems; b) releasing of magmatic volatiles from crustal reservoir(s) formed during past volcanic activity; c) degassing of a subsurface emplaced magma body. Mantle He flux in N-Portugal has been estimated to be up to 3 orders of magnitude higher than that typical for stable continental areas, thus suggesting, in this area, the presence of a tensional tectonic regime. This implies that mantle gases could migrate upward probably through inherited tectonic structures reactivated by neotectonic activity. The third possible scenario seems to be less plausible since seismic surveys carried out in NW Iberian did not find any significant evidence of mantle intrusion in the crust. The observed spatial variability in mantle-derived contribution could reflect the geometry of the granitic plutons in this area, thus supporting the hypotheses of an upper mantle degassing. Alternatively, it could be the result of a lateral migration of magmatic volatiles stored in a crustal reservoir. Wed, 03 Aug 2011 22:00:00 GMT http://hdl.handle.net/2122/7468 2011-08-03T22:00:00Z http://hdl.handle.net/2122/7467 Title: Stable isotope feature of groundwaters from Graciosa volcanic Island (Azores) – preliminary results Authors: Carreira, P.; Instituto Tecnológico e Nuclear, Sacavém, Portugal; Marques, J.M.; Instituto Superior Técnico, Lisboa, Portugal; Carvalho, M.R.; Faculdade de Ciencias de Lisboa, Lisboa, Portugal; Capasso, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Grassa, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Nunes, D.; Instituto Tecnológico e Nuclear, Sacavém, Portugal; Nunes, J.C.; Universidade dos Açores & INOVA Institute, S. Miguel, Azores, Portugal Editors: Demény, Attila; Instute for geochemical research, Hungarian Academy of Sciences Abstract: The Azores archipelago is made of nine islands all of volcanic origin and a few islets located in the North Atlantic Ocean, about 1800 km west of Portuguese mainland at the triple junction of the Eurasian, North American and Nubian plates (Azores Triple Junction = ATJ). Graciosa Island is part of the Central Group of Azores archipelago and is located on the Terceira Rift, a major tectonic feature of the ATJ. The main hydrothermal manifestations at Graciosa Island occur in the Caldeira volcano (SE part of the island), and particularly inside the huge (150 m wide, 80 m high) Furna do Enxofre lava cave located in the Caldeira, where a bubbling mud pool releases steam and gases, leading to the accumulation of CO2 at the bottom of the cave, filled by a coldwater subterranean lake. Three field work campaigns were carried out at Graciosa Island and 14 water samples have been collected, from boreholes, springs and the subterranean lake for isotopic (18O, 2H and 3H) and chemical analysis. The groundwater samples were plotted along the GMWL, and two water groups were identified in the 18O vs. 2H diagram. The splitting up of the samples is even more visible when the O-18 content is plotted as a function of the temperature or as a function of the electrical conductivity. Besides the differences in mineralization and temperature observed in the groundwater samples from Graciosa Island, an isotopic shift towards more enriched values is also observed. The salinity and isotopic content seems to indicate not a simple mixture between two end-members, i.e. seawater – fresh water: another process of mineralization and isotope enrichment must be considered in this active volcanic environment. A hypothesis to be formulated is that the source of salts could be associated to mixing with boiling seawater, that by evaporation will be able to: i) increase groundwater salinity, ii) strongly change the 2H content to more enriched values, and iii) absent or limited variation in d18O content. Wed, 03 Aug 2011 22:00:00 GMT http://hdl.handle.net/2122/7467 2011-08-03T22:00:00Z