Stable Isotope Geochemistry

Dedicated to Professor Dr Jochen Hoefs on the occasion of his 75th birthday Oxygen isotope fractionations in double carbonates of different crystal structures were calculated by the increment method. Synthesis experiments were performed at 60 °C and 100 °C to determine oxygen and carbon isotope fractionations involving PbMg[CO 3 ] 2. The calculations suggest that the double carbon-ates of calcite structure are systematically enriched in 18 O relative to those of aragonite and mixture structures. Internally consistent oxygen isotope fractionation factors are obtained for these minerals with respect to quartz, calcite and water at a temperature range of 0–1200 °C. The calculated fractionation factors for double carbonate–water systems are generally consistent with the data available from laboratory experiments. The experimentally determined fractionation factors for PbMg[CO 3 ] 2 , BaMg[CO 3 ] 2 and CaMg[CO 3 ] 2 against H 2 O not only fall between fractionation factors involving pure carbonate end-members but are also close to the calculated fractionation factors. In contrast, experimentally determined carbon isotope fractionation factors between PbMg[CO 3 ] 2 and CO 2 are much closer to theoretical predictions for the cerussite–CO 2 system than for the magnesite–CO 2 system, similar to the fractionation behavior for BaMg[CO 3 ] 2. Therefore, the combined theoretical and experimental results provide insights into the effects of crystal structure and exchange kinetics on oxygen isotope partitioning in double carbonates.

The data presented here comprise Ryazanian–Valanginian carbon isotope ratios analyzed from fossil wood and belemnites from the shallow marine Boyarka River succession in Siberia. Additional belemnite carbon isotope ratios from the Izhma River succession (also Ryazanian–Valanginian) in Russia are also presented. The wood-derived and belemnite-derived isotope ratios are considered to primarily reflct changes in the terrestrial and marine carbon isotope reservoirs respectively. The δ13Ccarb and δ13Cwood records reveal a distinct mid-Valanginian positive carbon isotope excursion, with the initiation occurring near the Boreal Russian michalskii–polyptychus zone boundary, which is broadly time-equivalent Tethyan campylotoxus–verrucosum boundary. The Ryazanian–Valanginian δ13Ccarb values fluctuate between c. –1 and +1.5‰ but reach a maximum of +4.1‰ in the Late Valanginian, whilst the δ13Cwood values fluctuate between c.–27 and –23.5‰ and reach a Late Valanginian maximum of –21.2‰. The excursion maximum in the Boreal Russian bidichotomus zones corresponds with the peak of the Tethyan marine carbonate excursion in the verrucosum–eperegrinus zones, the peak of a marine carbonate excursion recorded in the Argentinean atherstoni Zone and also with the peak of a terrestrial organic carbon isotope excursion in the Crimean trinodosum–ecallidiscus ammonite zones. The synchroneity of the positive carbon isotope event between the marine and terrestrial records and between the northern and southern hemispheres and Tethys, clearly indicates a strong coupling of the ocean-atmosphere system at this time and also confirms that this was a global event, which would have affected the total exchangeable carbon reservoir.

The nature and geodynamic setting of Inner Makran ophiolites (SE Iran) are controversial and are the focus of a growing debate. The Fannuj-Maskutan ophiolite complex (central Inner Makran) is made up of lherzolites, harzburgites, layered and isotropic gabbros and diabase dikes and basaltic lavas. Here we present new textural description, mineral and whole-rock chemistry of peridotites together with bulk geochemistry of magmatic mafic rocks and U-Pb geochronology and Lu-Hf isotopes of inherited zircons in gabbros, with the aim to reconstruct the petrogenesis of the Fannuj-Maskutan ophiolite. The results indicate to a subduction-metasomatized depleted mantle source experienced 10-20% of partial melting. A transition from IAT-gabbros to E-MORB-basalts is also outlined. We interpret the obtained results as evidence for the Fannuj-Maskutan genesis in a supra-subduction zone (SSZ) basin developed in the Iranian cadomian crust as indicated by the presence of inherited Cadomian zircons (ca. 515 Ma, εHf (t) : −13.6-+11.2). Comparing the Fannuj-Maskutan ophiolites to well-known SSZ-systems such as the South Sandwich SSZ, and integrating with the existing literature on Inner Makran ophiolite belt we interpret the Fannuj-Maskutan ophiolite as a part of a major SSZ-basin opened in the Iranian cadomian crust and evolved during the Neotethys subduction under Central Iran.

Abstract We present a Holocene record of climate
and environmental change in central New York
(USA) inferred using lithologic and stable isotope
data from two sediment cores recovered in Cayuga
Lake. The record was divided into three intervals: (1)
early Holocene (*11.6–8.8 ka), (2) Hypsithermal
(*8.8–4.4 ka), and (3) Neoglacial (*4.4 ka to
present). The early Holocene began abruptly, with
rising lake level and relatively deep water. Between
*10.8 and 9.2 ka, cool and dry conditions prevailed
at a time of maximum solar insolation. This anomaly
has been referred to as the ‘‘post-Younger Dryas
climate interval’’ and lasted *1,600 years, the
approximate length of one ‘‘Bond cycle.’’ The
Hypsithermal was the warmest, wettest and most
biologically productive interval of the Holocene in
central New York. The Hypsithermal was characterized
by centennial to multi-centennial-scale variability.
The 8.2 ka event is one such variation. The
Neoglacial was an interval of generally cooler and
dryer conditions, falling lake levels, and several
prominent climate anomalies. At approximately
2.4 ka, d13C of bulk organic matter increased
abruptly by 5% as lake level declined, and the lake
flora was dominated by Chara sp. during the coldest
interval of the Neoglacial. Numerous sediment variables
display increased variability *2.0 ka, which
continues today. Archaeological data from the literature
suggest that Native American populations may
have been large enough to impact land cover by about
2.4 ka and we hypothesize that the ‘‘Anthropocene’’
began at about that time in central New York. We
also found paleolimnological evidence for the Medieval
Warm Period (*1.4–0.5 ka), which was warmer
and wetter than today, and for the Little Ice Age
(*500–150 years ago), a period with temperatures
colder than today.

Introduction; 1. The properties and geology of marbles: 1.1 - Definition and general properties of marbles; 1.2 - Methods and problems for determining the provenance of marbles; 1.3 - Stable isotope analysis in marble provenancing; 1.4 - The principles of stable isotopes analysis; 1.5 - The isotopic composition of marble protoliths; 1.6 - Metamorphism and its role in determining the isotopic composition of pure marbles; 1.7 - Brief outline of Eastern Mediterranean geology; 2. The database and the ancient quarries: 2.1 - General considerations; 2.2 - Structure of the database; Italian marble quarries: 2.3 - Carrara; 2.4 - Seravezza; Greek marble quarries: attica: 2.5 - Hymettos; 2.6 - Pentelicon; Greek marble quarries: peloponnesos: 2.7 - Doliana; 2.8 - Mani; Greek marble quarries: the islands: 2.9 - Naxos; 2.10 - Paros; 2.11 - Thasos; 2.12 - Tinos; Turkish marble quarries: western anatolia: 2.13 - Afyon (Docimium); 2.14 - Altinta?; 2.15 - Aphrodisias; 2.16 - Denizli; 2.17 - Hierapolis; 2.18 - Thiountas; Turkish marble quarries: aegean coast: 2.19 - Ephesos; 2.20 - Miletos; Turkish marble quarries: the islands: 2.21 - Proconnesos; 3. Data analysis: 3.1 - Introduction; 3.2 - Discrimination and classification; 3.3 - Discriminant analysis; 3.4 - Case study one: the marble of the Michelangelo' s David; 3.5 - Case study two: the provenance of Cyrene marbles; 3.6 - The marble classification problem; Appendix a: Experimental methods; Appendix b: Content of the data disk; Colour plates; Bibliographical abbreviations; Bibliography; Acknowledgements; Index; List of figures; List of colour plates.

Abstract
This paper reviews the ultrastructure and chemistry of fish bone, with an emphasis on zooarchaeology and stable isotope analysis. On the basis of the chemical composition of the collagen and the relationships between the collagen and mineral phases, fish bone is more susceptible to biotic and abiotic degradation than mammalian bone and is therefore less likely to be recovered in archaeological deposits. The amino acid composition of fish bone differs from that of mammals (and other taxonomic groups), most notably with respect to hydroxyproline content. The C:N ratio of fish collagen, however, is very similar and slightly lower than mammalian collagen, and thus the traditional range of acceptable C:N ratios for collagen (2.9−3.6) should not be shifted or extended for fish on the basis of the amino acid composition of collagen. An extensive survey of published archaeological bone collagen C:N ratios demonstrates that fish collagen from archaeological contexts tends to have significantly higher C:N ratios than mammalian collagen. The elevated C:N ratios in fish bone collagen may be the result of abiotic degradation processes that occur within the bone after death, the presence of exogenous humic contaminants, or endogenous lipid contaminants."

The history of definition of the Aptian-Albian boundary is reviewed with particular reference to the ammonite schemes of Brinkmann (1937), Breistroffer (1947), Casey (1961a, 1996, 1999), Kemper (1982), Owen (1996, 1999), and Ruffell & Owen (1995). The classic sequence in the Hannover area of Germany described by Brinkmann (1937) is reviewed in the light of subsequent work. The definition of the base of the Albian Stage at the first occurrence of the ammonite Proleymeriella schrammeni (Jacob, 1907) is rejected as it can only be recognised over a limited area near Hannover; no more widely recognised secondary markers have been documented, and there is no permanent section at the present time. An alternative Aptian-Albian boundary, defined by the first occurrence of the ammonite Leymeriella (L.) tardefurcata (d’Orbigny, 1841) in the expanded Marnes Bleues section at Tartonne, Alpes-de-Haute-Provence, France, is suggested. The palynomorph, coccolith, planktonic foraminiferan, ammonite, and inoceramid bivalve sequence, organic and inorganic carbon, trace, rare earth, and major element record, oxygen and carbon isotope sequence, and strontium isotope data are presented for sections at the Col de Pre ́-Guittard, Arnayon (Droˆme), and Tartonne (Alpes-de-Haute-Provence) and described in detail. The Pre ́-Guittard section, considered as a candidate Global Boundary Stratotype Section (GSS) for the base of the Albian Stage at the Second International Symposium on Cretaceous Stage Boundaries held in Brussels in September 1995, provides a standard section for the boundary interval in SE France. It is, however, unsuitable as a GSS, as there is a hiatus at the critical level in the section. In contrast, the Tartonne section is a potential GSS. The Boundary Point for the base of the Albian Stage suggested here is the first criterion proposed at Brussels: the first appearance of the ammonite Leymeriella (L.) tardefurcata at the base of the Niveau Paquier within the expanded Marnes Bleues sequence. The first appearance is only 60 cm above the last record of its presumed ancestor, L. (L.) germanica Casey, 1957. So defined, the boundary lies within the Prediscosphaera columnata Nannofossil (NF) Zone NC/CC8, and the planktonic foraminiferal Hedbergella planispira Partial Range Zone. There is no major or trace element event associated with the proposed boundary, nor is there any distinctive oxygen or carbon isotopic signal. Strontium isotope data from the Tartonne section are compatible with those elsewhere in the basin, and show that the base of the Albian, defined by the first appearance of L. (L.) tardefurcata corresponds to an 87Sr/86Sr ratio of 0.707339±2. Systematic sections deal with a new palynomorph, calcareous nannofossils and ammonites; full range data and taxonomic indices are given for the first two groups.

Keywords: Paleozoic ophiolites U–Pb zircon dating Zircon εHf(t) Komatiite Supra-subduction zone-type magmatism Middle to Late Paleozoic ophiolites, which are remnants of the Paleo-Tethys Ocean, are aligned in two main zones in northern Iran: Darrehanjir–Fariman–Mashhad, and Rasht in the north and Jandagh–Anarak ophiolites to the south. Our new U–Pb zircon dating results show that the ~200 km long Darrehanjir–Mashhad mafic–ultramafic body is not a single ophiolite but a composite igneous complex composed of Permian pillow lavas and pelagic sediments in fault contact with a small outcrop of Devonian intrusive and ultramafic rocks. Darrehanjir intrusive rocks have U–Pb zircon ages of 380.6 ± 3.7 Ma and 382.9 ± 3.7 Ma respectively, ~100 Ma older than published ages for gabbros and radiolarites intercalated with lavas near Mashhad and Fariman. Mantle peridotites from the Devonian complex contain low Cr# spinel, similar to that in MORB-type peridotites. Devonian Darrehanjir gabbros and Permian Mashhad sequences both have boninitic and calc-alkaline signatures, respectively. The δ 18 O zircon values from the Devonian ferrodiorite (δ 18 O zircon ~ 4.6 ± 0.3‰) are slightly lower than the 5.2 to 5.4‰ expected for MORB-type zircons whereas Devonian plagiogranitic zircons mostly have δ 18 O zircon b5‰, perhaps reflecting involvement of hydrothermally altered crust. Similar, strongly positive values of zircon εHf(t) for plagiogranite (av. +14.9) and ferrodiorite (av. +13.8) indicate melt derivation from depleted astheno-sphere. Darrehanjir–Mashhad ophiolitic rocks can be divided into groups with high εNd (N10.3) and low εNd (b5.4) for both Permian and Devonian suites. Most Darrehanjir–Mashhad rocks are characterized by radiogenic 207 Pb/ 204 Pb and 208 Pb/ 204 Pb, indicating the involvement of subducted terrigenous sediments in the source. The Mashhad–Darrehanjir mafic–ultramafic complex demonstrates that this part of Paleo-Tethys evolved from oceanic crust formation above a subduction zone in Devonian time to accretionary convergence in Permian time. Iranian Paleozoic ophiolites and oceanic igneous complexes along with those of the Caucasus and Turkey in the west and Afghanistan, Turkmenistan and Tibet to the east, define a series of diachronous subduction-related marginal basins that were active from at least Early Devonian to Late Permian time.

A quantitative assessment of annual soil erosion by water in the northern part of Kirkuk Governorate, north of Iraq was investigated through integration of remote sensing, GIS and empirical RULSE soil erosion model. The five factors of RULSE model (rainfall erosivity R, soil erodibility K, slope length and steepness LS, crop management C, and practice factor P) were derived from different resources such as field survey, archival data, digital elevation model, and LANDSAT 8 multi-bands imagery. The annual soil erosion loss was estimated by multiplying the five factors in raster format using raster calculator of ArcGIS 10.2 software. The estimated annual soil losses rate for the study area ranges from 0 to 245 (t ha-1 yr-1) with an average of 2 (t ha-1 yr-1). The value ranges were classified into four categories: minimal, low, moderate, high soil erosion hazard zones using four classification schema: quantile, natural breaks, geometric, and standard deviation. Due to the similarity of results, the comparison was carried out between two schemas: natural breaks and geometric. The area covered by minimal-low soil hazard zones extends over an area of about 88% and 99% based on geometric and natural breaks schema, respectively. In turn, the moderate-high soil hazard zones cover only very small area (0.3%) based on natural breaks and relatively small area (12%) depending on geometric scheme. In general, both method results indicate that hazard of soil erosion is low in the study area. The spatial pattern of classified soil erosion rate indicates that the areas at moderate to high risk is located in the northeast and very small area in the east, while the minimal to low zones cover the other parts. The obtained results of could be useful to implement soil conservation practices in the study area.

approved: ___________________________________________ Shanaka L. de Silva Four multicyclic complex calderas and smaller ignimbrite shields located within the Altiplano Puna Volcanic Complex of the Central Andes (APVC) erupted 13000 km 3 of magma within the last 11 Ma. One of the largest and most complex of these is the Cerro Guacha Caldera. Ar-Ar age determinations and paleomagnetic directions suggest that the Cerro Guacha Caldera was formed by two major eruptions, caldera collapse, resurgence cycles and several smaller eruptions. Two major ignimbrites (> 600 km 3) are found with 40 Ar-39 Ar from biotites and sanidines of 5.65 ± 0.01Ma for the 1300 km 3 (magma volume) Guacha ignimbrite and 3.49 ± 0.01Ma for the 800 km 3 Tara Ignimbrite. The last major eruption occurred on the western flank producing the 1.72 ± 0.02 Ma Puripica Chico Ignimbrite with a volume of approximately 10 km 3. Characteristic remanent magnetization data (ChRM) for these ignimbrites show that the Guacha has reverse polarity, while the Tara is normally polarized and the magnetic fingerprints have allowed their current full extents to be identified. A conspicuous lineament of volcanic structures

This study is a part of the third axis of the « ETIAGE » project, a four year collaboration (2010-2014) between the Lyonnaise des Eaux, the Communauté Urbaine de Bordeaux (CUB), AEAG, and FEDER, Aquitaine region with the University of Bordeaux, CNRS and IRSTEA. The axis 3 objectives were to document the trace metal inputs from the CUB watershed into the waters of the Garonne section of the Gironde estuary. The Gironde Estuary is one of the largest macrotidal and highly turbid estuaries in Western Europe characterized by the presence of a strong maximum turbidity zone (MTZ) with high suspended particulate matter (SPM) concentrations (>1 g.L-1 in surface water) transporting estuarine particles and potentially hazardous trace elements. This study has focused on the trace metal inputs from the two main wastewater treatment plants (WWTP) of the CUB. The objective of this research was therefore to study in detail the daily concentrations, fluxes, and dynamics of 8 EU priority contaminants Cr, Cu, Cr, Hg, Ni, Pb Zn, As, and the emerging contaminant Ag from the WWTPs in the CUB. The calculated removal rates are significant, around 80 % for the majority of metals, mainly as a result of the decantation phase. Despite this high removal efficiency, during periods of heavy rainstorms and low river discharges, the urban metal inputs via the WWTPs may still significantly increase metal concentrations and fluxes in the fluvial Gironde Estuary impacting water quality. In addition, the WWTP fluxes and concentrations of Ag exceeded common background concentrations in the Gironde fluvial estuary, making it an interesting urban tracer. The treatment within the WWTPs concentrates the trace metals in the sludge, yet, metal concentrations remained below legal norms for agricultural use. However, the analysis of WWTP sludge revealed that trace element concentrations are 15 (Ag) and 30 (Cu) times higher than natural background concentrations with high enrichment of Hg, Ag, Cr, Cu and Zn with over 70 % of Cd, Ag, Pb, Cu, and Zn being potentially bioavailable. Therefore, with increasing urban pressure on environmental quality, these results support the need for the development of efficient water quality monitoring tools.
Keywords : Coastal pollution, estuary metal contamination, urban trace elements, fluxes, wastewater, Gironde Estuary

"I.J. Bos, Het ontstaan van de venen in het Vechtgebied

J.A.J. Vervloet, Het Utrechtse Vechtgebied in het verleden: occupatie en ontginning in eenhoofdzakelijk natte omgeving

T. van Bommel, Middeleeuwse ontginningen in de noordelijke Vechtstreek

Y. Kobalowitz, Een raadselachtige lijn door de Aetsveldsche Polder

S. Koopman en A.T.E. Cruysheer, Een Laat-Weichselien duin en archeologische vondsten in de Nieuwe Keverdijksche Polder

Y. Kobalowitz, De Vuursche: ontginningsrelicten in een grensgebied

L. Kootker, Archeologisch isotopenonderzoek: wat is het en wat kan je ermee?

H. Schaftenaar, Keveren, een voormalig middeleeuws gehucht bij de Naardermeer"

We review and evaluate human adaptations during the last glacial-interglacial climatic transition in southwest Asia. Stable isotope data imply that climatic change was synchronous across the region within the limits of dating uncertainty. Changes in vegetation, as indicated from pollen and charcoal, mirror step-wise shifts between cold-dry and warm-wet climatic conditions, but with lag effects for woody vegetation in some upland and interior areas. Palaeoenvironmental data can be set against regional archaeological evidence for human occupancy and economy from the later Epipalaeolithic to the aceramic Neolithic. Demographic change is evaluated from summed radiocarbon date probability distributions , which indicating contrasting and in some cases opposite-population trajectories in different regions. Abrupt warming transitions at ~14.5 and 11.7 ka BP may have acted as pacemakers for rapid cultural change in some areas, notably at the start of the Natufian and Pre-Pottery Neolithic cultures. However temporal synchroneity does not mean that climatic changes had the same environmental or societal consequences in different regions. During cold-dry time intervals, regions such as the Levant acted as refugia for plant and animal resources and human population. In areas where socio-ecological continuity was maintained through periods of adverse climate (e.g. Younger Dryas) human communities were able to respond rapidly to subsequent climatic improvement. By contrast, in areas where there was a break in settlement at these times (e.g. central Anatolia), populations were slower to react to the new opportunities provided by the interglacial world.

Climate variability is driven by a complex interplay of global-scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter-regional correlation, which in most cases cannot be btained with biostratigraphic methods alone. Chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high-resolution correlation over large distances, but complications arise from a multitude of possible influences from local differences in biological, diagenetic and physico-chemical factors on individual δ13C records that can mask the global signal. To better assess the global versus local contribution in a δ13C record it is necessary to compare numerous isotopic records on a global scale. As a contribution to this objective, this paper reviews bulk sediment δ13Ccarb records from the Late Cretaceous in order to identify differences and similarities in secular δ13C trends that help establish a global reference δ13C record for this period. The study presents a global-scale comparison of twenty δ13C records from sections representing various palaeo-latitudes in both hemispheres and different oceanic settings from the Boreal, Tethys, Western Interior, Indian Ocean and Pacific Ocean, and with various diagenetic overprinting. The isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute δ13C values and variation in amplitude between the sites. These differences reflect the varying local influences e.g. from depositional settings, bottom water age and diagenetic history, whereas the concordant patterns in δ13C shifts might represent δ13C fluctuations in the global seawater dissolved inorganic carbon. The latter is modulated by variations in organic matter burial relative to re-mineralization, in the global-scale formation of authigenic carbonate, and in partitioning of carbon between organic carbon and carbonate sinks. These variations are mainly controlled by changes in climate and eustasy. Additionally, some globally synchronous shifts in the bulk δ13Ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment. Formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and, thus, can be globally synchronized by fluctuations in eustasy, atmospheric and oceanic oxygen levels or in large-scale oceanic circulation. Because the influence of early diagenetic cements on the bulk δ13Ccarb signal can, but need not be synchronized, chemostratigraphy should not be used as a stand-alone method for trans-continental correlation, and especially minor isotopic shifts have to be interpreted with utmost care. Nevertheless, the observed consistency of the δ13C correlations confirms global scale applicability of bulk sediment δ13C chemostratigraphy for the Late Cretaceous, including sediments that underwent lithification and burial diagenesis such as the sediments from the Himalayan and Alpine sections. Limitations arise from increased uncertainties (1) in sediments with very low carbonate content, (2) from larger δ13C variability in sediments from very shallow marine environments, (3) from unrecognized hiatuses or strong changes in sedimentation rates, and (4) in sections with short stratigraphic coverage or with few biostratigraphic marker horizons.

The combination of chemostratigraphy with biostratigraphy and magnetostratigraphy substantially increases the precision and temporal resolution of inter-regional correlations and helps overcome problems that arise from differences in biostratigraphic schemes, facies or provincialism of key fossils. By using an iterative approach to stepwise increase precision of the correlations, isochroneity of first and last occurrences of marker species versus chemostratigraphy is tested, which helps to improve biostratigraphic zonations, to assess zonal boundary ages and to identify useful criteria for defining Late Cretaceous stage boundaries, many of which are still not formally defined. The presented correlations indicate a consistent position for most planktic foraminifer zonal boundaries relative to corresponding isotope shifts during the mid-Cretaceous sea-level high, whereas diachroneity appears to be more pronounced during the Late Campanian and Maastrichtian global sea-level fall. A similar pattern is observed for trans-continental consistency in the δ13C shifts. Graphic correlation of isotopic shifts, magnetostratigraphic and biostratigraphic events among the compared sections is used to detect hiatuses or relative changes sediment accumulation rates and visualizes consistency or offsets of individual biostratigraphic markers relative to chemo- and magnetostratigraphy. Finally, an attempt of a global average δ13C stack is presented for the Turonian through Maastrichtian.

Major and trace elements, noble gases, and stable (dD, d 18 O) and cosmogenic (3 H, 14 C) isotopes were measured from geothermal fluids in two adjacent geothermal areas in NW-Mexico, Las Tres Vírgenes (LTV) and Cerro Prieto (CP). The goal is to trace the origin of reservoir fluids and to place paleoclimate and structural-volcanic constraints in the region. Measured 3 He/ 4 He (R) ratios normalized to the atmospheric value (R a ¼ 1.386 Â 10 À6) vary between 2.73 and 4.77 and are compatible with mixing between a mantle component varying between 42 and 77% of mantle helium and a crustal, radiogenic He component with contributions varying between 23% and 58%. Apparent UeTh/ 4 He ages for CP fluids (0.7e7 Ma) suggest the presence of a sustained 4 He flux from a granitic basement or from mixing with connate brines, deposited during the Colorado River delta formation (1.5e3 Ma). Radiogenic in situ 4 He production age modeling at LTV, combined with the presence of radiogenic carbon (1.89 ± 0.11 pmC e 35.61 ± 0.28 pmC) and the absence of tritium strongly suggest the Quaternary infiltration of meteoric water into the LTV geothermal reservoir, ranging between 4 and 31 ka BP. The present geochemical heterogeneity of LTV fluids can be reconstructed by mixing Late Pleistocene e Early Holocene meteoric water (58e75%) with a fossil seawater component (25e42%), as evidenced by Br/Cl and stable isotope trends. CP geothermal water is composed of infiltrated Colorado River water with a minor impact by halite dissolution, whereas a vapor-dominated sample is composed of Colorado River water and vapor from deeper levels. dD values for the LTV meteoric end-member, which are 20‰e44‰ depleted with respect to present-day precipitation , as well as calculated annual paleotemperatures 6.9e13.6 C lower than present average temperatures in Baja California point to the presence of humid and cooler climatic conditions in the Baja California peninsula during the final stage of the Last Glacial Pluvial period. Quaternary recharge of the LTV geothermal reservoir is related to elevated precipitation rates during cooler-humid climate intervals in the Late Pleistocene and Early Holocene. The probable replacement of connate water or pore fluids by infiltrating surface water might have been triggered by enhanced fracture and fault permeability through contemporaneous tectonicevolcanic activity in the Las Tres Vírgenes region. Fast hydrothermal alteration processes caused a secondary, positive d 18 O-shift from 4‰ to 6‰ for LTV and from 2‰ to 4‰ for CP geothermal fluids since the Late Glacial infiltration.

The Neyriz ophiolite along the northeast flank of the Zagros fold-thrust belt in southern Iran is an excellent example of a Late Cretaceous supra-subduction zone (SSZ)-related ophiolite on the north side of the Neotethys. The ophiolite comprises a mantle sequence including lherzolite, harzburgite, diabasic dikes, and cumulate to mylonitic gabbro lenses, and a crustal sequence comprising a sheeted dike complex and pillow lavas associated with pelagic limestone and radiolarite. Mantle harzburgites contain less CaO and Al 2 O 3 , are depleted in rare earth elements, and contain spinels that are more Cr-rich than lherzolites. Mineral compositions of peridotites are similar to those of both abyssal and SSZ-peridotites. Neyriz gabbroic rocks show boninitic (SSZ-related) affinities, while crustal rocks are similar to early arc tholeiites. Mineral compositions of gabbroic rocks resemble those of SSZ-related cumulates such as high forsterite olivine, anorthite-rich plagioclase, and high-Mg# clinopyroxene. Initial εNd(t) values range from +7.9 to +9.3 for the Neyriz magmatic rocks. Samples with radiogenic Nd overlap with least radiogenic mid-ocean ridge basalts and with Semail and other Late Cretaceous Tethyan ophiolitic rocks. Initial 87 Sr/ 86 Sr ranges from 0.7033 to 0.7044, suggesting modification due to seafloor alteration. Most Neyriz magmatic rocks are characterized by less radiogenic 207 Pb/ 204 Pb (near the northern hemisphere reference line), suggesting less involvement of sediments in their mantle source. Our results for Neyriz ophiolite and the similarity to other Iranian Zagros ophiolites support a subduction initiation setting for its generation.

Assessment of redox state, pH, environmental isotope ratios (d18O, d2H) coupled with PHREEQC speciation modeling investigations were conducted to understand trace element geochemical controls in basement complex aquifer in Blantyre, Malawi. Groundwater in the area is typical Ca–Mg–Na–HCO3 type suggesting more of carbonate weathering and significance of carbon dioxide with dissolution of evaporites, silicate weathering and cation exchange being part of the processes contributing to groundwater mineralization. The significance of pH and redox status of groundwater was observed. The groundwater redox state was mostly O2-controlled with few exceptions where mixed (oxic–anoxic) O2–Mn(IV) and O2–Fe(III)/SO4 controlled redox states were modeled. More so, some of the main trace element species modeled with PHREEQC varied with respect to pH. For instance vanadium(III) and vanadium(IV) decreased with increase in field pH contrasting the trend observed for vanadium(V). The isotopic composition of the sampled groundwater varied between 5.89‰ and 3.32‰ for d18O and 36.98‰ and 20.42‰ for d2H. The d2H/d18O and d18O/Cl ratios revealed that groundwater is of meteoric origin through vertical recharge and mixing processes. The d-excess value approximated the y-intercept of GMWL of 10 (d-excess = 9.269, SD = 1.240) implying that influence of secondary evaporative processes on isotopic signature of the study area is minimal. Thus, there is evidence to suggest that groundwater chemistry in the studied aquifer is influenced by inherent processes with contribution from human activities and furthermore, the water originates from rainwater recharge. With such results, more studies are recommended to further constrain the processes involved in mineralization through isotopic fractionation investigations.

The paper deals with the major chemistry and stable isotopes (hydrogen, oxygen, carbon, sulfur, strontium) of waters and solutes from the Salar de Atacama basin (Rio Pedro, Honar Creek and Laguna Chaxa) and Andean Altiplano (Laguna Miñique and Laguna Miscanti). The water inflows of the Salar are chemically quite different, the Rio San Pedro being of Na-Cl type and the Honar Creek of Na-HCO3 type, in keeping with the sedimentary-evaporitic and volcanic nature of the catchment rocks respectively. The δ34S and δ18O values of sulfate and the 87Sr/86Sr ratio of strontium in the streams match those of drained rocks, whereas the δ13C values of dissolved carbonate are largely controlled by vegetation. The lagoons are evaporated meteoric water bodies, and the relative air humidity estimated from the slope of the isotopic evaporation line is in accordance with historical data on air humidity in the area. The Laguna Chaxa is Na-Cl rich, and its isotopic composition are consistent with a mixed sedimentary-volcanic provenance of sulfur and strontium solutes. The Laguna Miñique is Na-SO4 rich, and its sulfate δ34S is nearly identical to that of Laguna Chaxa. The δ13C(HCO3) values are quite different in the Laguna Chaxa and Laguna Miñique, with the former being notably enriched in 13C probably because of preferential uptake of 12C by the high biological productivity occurring in the lagoon. The limited set of new data is interpreted in the context of a much larger literature database. In particular, previous chemical data on inflows and brines in the Salar de Atacama were revisited, and compared with evaporation path models and mineral stability diagrams (boron, lithium and Mg-minerals) computed using updated software and thermodynamic databases. The modeling shows that the removal of boron and lithium from sulfate-rich brines possibly occurs, respectively, as ulexite and sulfate salts, and carnallite should be the final magnesium phase of the brine evolution.