Stable Isotope Geochemistry

Silicon isotope fractionation during silicification is poorly understood and impedes our ability to decipher paleoenvironmental conditions from Si isotopes in ancient cherts. To investigate isotope fractionation during silica-for‑carbonate replacement we analyzed the microscale Si and O isotope composition in different silica phases in a silicified zebra dolostone as well as their bulk δ18O and Δ’17O compositions. The subsequent replacement of carbonate layers is mimicked by decreasing δ18O and δ30Si. The textural relationship and magnitude of Si and O isotope fractionation is best explained by near-quantitative silica precipitation in an open system with finite Si. A Rayleigh model for silicification suggests positive Ɛ30/28Si during silicification, conforming with predictions for isotope distribution at chemical equilibrium from ab-initio models. Application of the modelled Ɛ30Si-T relationship yields silicification temperatures of approx. 50 °C. To reconcile the δ18Ochert composition with these temperatures, the δ18O of the fluid must have been between −2.5 and − 4 ‰, compositions for which the quartz phases fall close to the oxygen equilibrium fractionation line in three-isotope space. Diagenetic silica replacement appears to occur in O and Si isotopic equilibrium allowing reconstructions of temperatures of silicification from Si isotopes and derive the δ18O composition of the fluid – a highly desired value needed for accurate reconstructions of the temperature- and δ18O histories of the oceans.

The lower Frasnian (transitans Zone with Ancyrodella priamosica = MN 4 Zone) rhythmic basin succession of marly limestones and shales (upper Szyd³ówek Beds) at Kostom³oty, western Holy Cross Mts., Central Poland, contains a record of the transgressive-hypoxic Timan Event in this drowned part of southern Laurussian shelf. The unique facies consists of organic-rich marly shales and a distinctive pyritic, goniatite level, 1.6 m thick. The faunal assemblage is dominated by pyritized shells of diminutive mollusks with cephalopods (including goniatites Epitornoceras and Acanthoclymenia), buchioline bivalves (Glyptohallicardia) and styliolinids. This interval is marked by moderately low Th/U ratios and pyrite framboid size distributions suggestive of dysoxic rather than permanent euxinic conditions. The scarcity of infauna and bioturbation resulted in finely laminated sedimentary fabrics, as well as the low diversity of the presumed pioneer benthos (mostly brachiopods). In the topmost part of the Szyd³ówek Beds, distinguished by the Styliolina coquina interbedded between limestone-biodetrital layers, the above geochemical proxies and C-isotope positive shift indicate a tendency to somewhat increased bottom oxygen deficiency and higher carbon burial rate linked with a bloom of pelagic biota during high-productivity pulse. The geochemical and community changes are a complex regional record of the initial phase of a major perturbation in the earth-ocean system during a phase of intermittently rising sea level in the early to middle Frasnian, and associated with the highest positive C-isotope ratios of the Devonian.

Previous studies on Athabasca basin unconformity-related uranium deposits have focused on major deposits and have not investigated sites with barren alteration systems that could clarify some of the critical factors controlling mineralization processes. A paragenetic study of the Wheeler River area reveals the presence of minerals that formed during the diagenetic, the main hydrothermal, which is subdivided into early, mid-, and late hydrothermal substages, and the late alteration stages. The diagenetic stage consists of early quartz overgrowths, siderite, rutile, hematite, and abundant dickite in the pore spaces of the Manitou Falls Formation. The early hydrothermal alteration substage is characterized by pervasive 1Mc muscovite alteration and minor goyazite clusters, which formed from oxidizing basinal fluids at temperatures around 240°C prior to 1550 Ma, based on Ar-Ar dates. The mid-hydrothermal alteration substage comprises dravite and sudoite in the basal 200 m of the Manitou Falls Formation, which are interpreted to have formed at temperatures around 175°C from fluids chemically distinct but isotopically similar to the basinal fluids involved during the early hydrothermal alteration substage. The late hydrothermal substage was observed only at zone K of the Wheeler River area and is characterized by the precipitation of clinochlore, copper sulfides, and florencite from reducing basement fluids emerging into the Manitou Falls Formation at temperatures around 230°C, creating a ~250-m-high bỹ 250-m-wide reducing halo. Oxidized uranium-bearing basinal fluids interacted with the Manitou Falls Formation during the early hydrothermal substage prior to the arrival of the reducing fluids during the mid-and late hydrothermal substages and this precluded uranium precipitation. The post-hydrothermal alteration stage is characterized by formation of kaolinite after late hydrothermal clinochlore near fractures by meteoric waters. A minimal amount of leachable radiogenic Pb, with a Pb-Pb model age of 1907 Ma that is older age than both the Athabasca basin and the main mineralization event of 1590 Ma, was encountered at zone K, indicating low probability of this area to host uranium mineralization. However, areas of possible unconformity-related uranium deposits were identified outside zone K wherein significant amounts leachable radiogenic Pb were observed.

https://eageannual.org/geosecrets/

What secrets lie beneath the waves off Norway’s coast, where the earth split apart millions of years ago? What very rare mineral treasures lie beneath Norway’s rugged landscape? Why is Norway a prime location for understanding the Earth’s climate past and future?

“Geosecrets of Norway” will lead you to find the answers. Victor Aarre Madsen, treasurer of Local Chapter Stavanger, will open the session by challenging you with curiosities and fascinating facts from Norway.

Tin ingots have been the focus of multi-method studies involving Sn and Pb isotopes, as well as trace element patterns, in an effort to determine provenance. Although they are non-alloyed artifacts, it has been demonstrated recently that the Pb in most tin ingots was acquired from multiple sources. Herein, we reexamine the corpus of analytical chemical and isotopic studies of European tin ingots from prehistory to investigate the nature and extent of metal mixing in these objects. Multi-variable mixing trends were identified in 20% of Uluburun ingots and 50% of Israeli ingots. A general Pb-associated mixing trend observed throughout the full assemblage of oxhide ingots in the Uluburun cargo suggests that the extent of mixing is considerably higher. The absence of mixing patterns in Sn and Pb isotopes and small size of the ingots from SW England suggests simple one-pour casts of small ingots. In contrast, the extensive mixing in large Mediterranean ingots demonstrates that amalgamation and recasting of tin metal was commonplace within this region of extensive long-distance exchange. Mixing trends were also identified for trace elements including Mn, Co, Ni, Cu, Zn, As, Se, Nb, Cd, In, Sb, Te, Ta, Au, and Bi. The complex mixing patterns associated with Mediterranean tin ingots provide new information regarding the habitus of workers engaged in the chaîne opératoire of tin production, including ore purification, contamination during smelting and/or casting, and the recasting of tin to facilitate transport and exchange in the large-scale, standardized markets of the eastern Mediterranean. Given the apparent extent of mixing evident in tin ingots, mixed metal sources must be considered when interpreting the isotopic and trace element compositions of tin artifacts to infer the metal's provenance.

Based on geo-anthropological and geochemical studies, catastrophes similar to the unprecedented gas explosions in the mid-1980s from the Cameroonian killer lakes Nyos and Monoun, might occur in any of the 37 other lakes located along the Cameroon Volcanic Line (CVL). Because people could suffer loss and desolation from predictable catastrophes in the future, monitoring/surveillance policies must be established. Due to their location, crater lakes integrate the geochemical processes that develop in the Earth's crust due to magmatic activities. Therefore, monitoring the surface manifestations of those deep seated and/or hydrothermal processes might reveal increases/decreases in magmatic activities. The anomalous changes in a volcanic lake induced by mixing with exogenous fluids that have a specific δ 18 O and δD compositional fingerprint (magmatic, metamorphic, etc.) could be utilized to predict volcanic hazards. If the steady state of a lake environment and the external and intrinsic parameters that control its hydrodynamics are clearly identified and reasonably understood, the anomalous evolutionary processes that compromise its stability can be identified. This study attempts to collect the δ 18 O and δD data from 17 Cameroonian lakes to help establish a volcano-related monitoring/surveillance network. This work identifies the processes that control the isotopic composition of the lakes and assesses the intra-/inter-and spatial δ 18 O/δD variations. Almost all of the lakes contain meteoric water. These lakes are mostly isotopically stratified; epilimnia is generally more positive than the hypolimnia. However, although the rainfall is gradually depleted in heavy isotopes when moving from the South to the North due to the latitude effect, the lakes become more enriched (0.6‰/100 km) due to evaporation. The evaluated impact of several parameters on the isotopic variation suggests that the hydrological setting may play an important, albeit not preeminent, role relative to the other factors. Consequently, the interplay between climatology, phytogeography, hydrology and morphometry might help shape the isotopic composition of the lakes.

To investigate dietary habits in the Neolithic (6800 to 6100 cal. BC) population of Tepecik-Çiftlik in the Cappadocia region of Anatolia, the bulk bone collagen of 19 adult individuals and seven animals (domesticated caprids and cattle as well as wild horse and cat) were subjected to stable carbon and nitrogen isotope ratio analysis. The mean values of the sampled human adults are − 19.5 ‰ ± 0.2 ‰ for δ 13 C (range 0.8 ‰ from − 19.8 ‰ to − 19.0 ‰), and 11.3 ‰ ± 1.1 ‰ for δ 15 N (range of 3.4 ‰ from 9.4 ‰ to 12.8 ‰). The stable isotope values of the Neolithic population of Tepecik-Çiftlik are very homogeneous, which suggests the consumption of very similar C 3 plants and animals consuming C 3 plants from a narrow environmental and ecological range. There is a slight but statistically significant difference in the δ 15 N values between males and females, with the indication being that males probably had a slightly greater input of protein in their diet. One interesting observation from this study is that despite the extensive connections and exchange networks that the settlement was involved in, as demonstrated through the distribution of locally sourced obsidian, the dietary habits and subsistence practices of the Neolithic Tepecik-Çiftlik population have a very local and micro-regional flavour. This was likely emphasised and enhanced by the immediate local geographical and environmental conditions with the site being located in a narrow valley surrounded by high mountains.

It has become a widespread practice to convert δ18Op values measured in human and animal dental enamel to a corresponding value of δ18Ow and compare these data with mapped δ18Ow groundwater or meteoric water values to locate the region where the owner of the tooth lived during the formation of the enamel. Because this is a regression procedure, the errors associated with the predicted δ18Ow values will depend critically on the correlation between the comparative data used to perform the regression. By comparing four widely used regression equations we demonstrate that the smallest 95% error is likely to be greater than ±1% in δ18Ow, and could be as large as ±3.5%. These values are significantly higher than those quoted in some of the recent literature, and measurements with errors at the higher end of this range would render many of the published geographical attributions statistically unsupportable. We suggest that the simplest solution to this situation is to make geographical att...

The morphology and geochemistry of pedogenic carbonate found in vertic claystone palaeosols in the Devonian Catskill Formation in central Pennsylvania preserve a record of the physical and chemical environment of carbonate precipitation. The carbonate is characterized by three distinct petrographic generations. Pedogenic rhizoliths and nodules are the earliest precipitated generation, and typically consist of dull red-brown luminescent micrite. Clear, equant calcite spar cement fills voids in the centres of rhizoliths, as well as circumgranular cracks and septarian voids in nodules. Early spar cements are nonluminescent to dull luminescent, whereas later spar cements exhibit bright yellow-orange luminescence. Late stage pedogenic fractures are always occluded with very bright yellow-orange luminescent spar cements. The incorporation of progressively higher concentrations of Mn (up to 34 000 ppm) into successively younger calcite spar cements, without concomitant increases in Fe, suggests carbonate precipitation from an evolving meteoric water in which Mn2+ became increasingly mobile over time. The increased mobility is possibly due to decreasing Eh, resulting from oxidation of organic matter after rapid soil burial on the floodplain. The amount of Fe2+ available for incorporation into calcite was limited because most iron was immobile, having been earlier oxidized and bound to the palaeosol clay matrix as a poorly crystallized ferric oxide or oxyhydroxide mineral. Carbon isotope compositions of pedogenic carbonate correlate with the inferred depth of carbonate precipitation. Rhizoliths preserved below the lowest stratigraphic occurrences of pedogenic slickensides are consistently depleted in 3C relative to nodules, which formed stratigraphically higher, within the zone of active soil shrink and swell processes. Nodular carbonate, precipitated in proximity to deep cracks in the soil, is enriched due to increased gas exchange with isotopically heavy atmospheric C 0 2. Accordingly, rhizolith compositions will most accurately estimate palaeoatmospheric levels of C 0 2 ; the use of nodule compositions may result in overestimation of Pco, by as much as 30%.

Ancient Native American ancestors (Clovis) have been interpreted as either specialized megafauna hunters or generalist foragers. Supporting data are typically indirect (toolkits, associated fauna) or speculative (models, actualistic experiments). Here, we present stable isotope analyses of the only known Clovis individual, the 18-month-old Anzick child, to directly infer maternal protein diet. Using comparative fauna from this region and period, we find that mammoth was the largest contributor to Clovis diet, followed by elk and bison/camel, while the contribution of small mammals was negligible, broadly consistent with the Clovis zooarchaeological record. When compared with second-order consumers, the Anzick-1 maternal diet is closest to that of scimitar cat, a mammoth specialist. Our findings are consistent with the Clovis megafaunal specialist model, using sophisticated technology and high residential mobility to subsist on the highest ranked prey, an adaptation allowing them to rapidly expand across the Americas south of the Pleistocene ice sheets.

When groundwater quality is good, it may be a substantial water supply for
various applications. However, no systematic research on
hydrogeochemistry and water quality features for drinking and irrigation has
been undertaken in the present study area. As a result, the current study
looked at hydrogeochemical variables and groundwater quality for drinking
and irrigation in Tercha district, Dawuro Zone, Southern Ethiopia. Fortyseven groundwater samples were collected and tested to satisfy the required
target for various physicochemical properties. The hydrogeochemical
features of the groundwater in the study region were assessed using in-situ
testing and laboratory analysis of physicochemical parameters. Groundwater
samples from the research region were slightly acidic to slightly basic, with
the principal cations and anions decreasing in sequence: Na+
> Ca2+ > Mg2+
> K+
and HCO3
-> Cl-> SO4
2-. The hadrochemical facies of the studied region
evolved from mildly mineralized dominant highland Ca-HCO3 water types
to moderately mineralized mixed Ca-Na-HCO3 water types to highly
mineralized deep rift floor Na-HCO3 water types. Additionally, the World
Health Organization and the Ethiopian Standard Agency were utilized to
compare the drinking water quality. Except for NO3
-
(4.25 %), Fe (8.51 %),
and F- (2.12%), all groundwater samples from the research region were
determined to be within permitted limits and appropriate for drinking.
According to the Water Quality Index, about 80.86% of groundwater
samples are excellent, and 19.14% are good drinking water. Sodium
absorption ratio (SAR), sodium (Na) percentage, residual sodium carbonate
RSC, permeability index (PI), and magnesium hazard were among the
irrigation water quality indicators calculated (MH). The great majority of
groundwater samples are suitable for agricultural use.

The Qing court produced an extensive history of the Ming empire in the Manchu language, which has survived in manuscript form in the Palace Museum under the title Ming gurun i suduri (History of the Ming State). Based on a close reading of this manuscript and scrutiny of related archival documents, this article elaborates on three observations. First, the Ming gurun i suduri resulted from the earliest stage (1645–1669) of the Qing compilation of the Ming history. With a primary focus on producing a chronicle in Manchu, it exemplifies the mid-seventeenth-century development of Inner Asian historiography. Second, it recounts Ming history by juxtaposing and connecting translated extracts from the Ming shilu 明實錄 (Ming Veritable Records) whenever it exists. This approach that combines compiling and translating, in effect, offers a reassessment of key political events and figures. Third, in light of the Ming gurun i suduri thus contextualized, the 1739 Ming shi 明史 (Ming History) is best seen as a product of a century-long history of negotiation (1645–1739) during which the ideological agenda and intellectual achievements of the early Qing court gradually sank into oblivion.

Тезисы доклада о последней трансгрессии оз. Иссык-Куль.
Мой и Максима Меньшикова вклад в доклад был в археологической составляющей.

Abstracts of the report on the latest transgression of the lake. Issyk-Kul.
My and Maxim Menshikov's contribution to the report was in the archaeological component

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A limited number of mini-basins provinces have been described, especially with fluvial dominated infill. The mini-basin development is dependent on local factors such as salt tectonics which influence the rate and style of mini-basin subsidence and the surface topographic expressions. It is further dependent on the modification of regional factors, such as climate, tectonic regime and rates of sediment input. The Sivas basin is an elongated Oligo-Miocene basin showing numerous minibasins separated by evaporites structures such as welds and diapirs of various shapes, with spectacular outcropping conditions. This study focuses on ten of well-exposed mini-basins, which present a 1km to 2.5km sedimentary pile of continental sediment unconformably capped by a shallow marine deposit. The infill of these mini-basins began during the late Oligocene over an older basal evaporite layer, with (1) a playa-lake system deposited under arid climatic conditions (sheet-flood and evaporites), followed by (2) a braided fluvial system occurring during a humid period, (3) then a lacustrine system that is finally capped by (4) shallow marine deposits during the Early Miocene. This fluvial system with a lack of distinct river channels incision and related drainage patterns in arid to semi-arid climatic regimes looks like a distributary fluvial systems. The abrupt facies changes bounding stratigraphic units are related to base level changes in relation with regional climatic events, but modified locally by salt tectonics. Climatic as well as tectonic-driven variations at a regional scale modify the rate and style of sediment supply and the regional subsidence, which are recorded in a coeval manner by the fluvial system and shallow marine system in each mini-basin. In contrast, the salt tectonic modify locally sedimentary record and associated stratal pattern within each mini-basin, for a given stratigraphic unit. 3.11.5 (o) The Central High Atlas in Morocco : a snapshot of a Jurassic diapiric rifted basin

We report new geochronologic and paleoenvironmental data for Mnaraeka 01, a prehistoric site located in the Kilwa district of coastal Tanzania. The oldest trace of human activity at the site comes from a context dated to 71 ± 6 thousand years ago (ka) where flaked stones but techno-typologically non-diagnostic were uncovered. Stratigraphic units dated to 43.9 ± 2.4 ka and 41.8 ± 2.1 ka have revealed stone artifacts broadly characteristic of the Middle Stone Age (MSA) while a context dated to 10.0 ± 0.6 ka has produced artifacts referrable to the Later Stone Age (LSA). Eight soil samples from the site subject to stable carbon and nitrogen isotope analyses reflect grassy-woodland habitat during the settlement episodes with δ13C values ranging from −19.3‰ to −27.8‰ (vs. VPDB). The results demonstrate the persistence of coastal woodland vegetation and human foraging populations in coastal East Africa during the onset of the cold Marine Isotope Stage (MIS) 4, between the cold spells of Heinrich Events 4 and 5, and during the Holocene Climatic Optimum. Our study shows that the Stone Age archaeology of coastal Tanzania has the potential to shed light on the role of coastal ecozones as potential refugia for human populations during variable climate conditions of the late Quaternary. Furthermore, the emergent datasets from Mnaraeka 01 open a window into the deep human history preserved in the Kilwa basin.

The Stirling volcanogenic massive sulphide (VMS) deposit (historical production 1.2 Mt of 6.4% Zn, 1.5% Pb, 0.74% Cu, 2.2 oz.It Ag, 0.03 oz.It Au) is hosted by intennediate pyroclastics and finely laminated volcaniclastics of the Late Hadrynian (680 Ma) Stirling Group, SE Cape Breton Island. The volcanic strata are intruded by a quartzfeldspar porphyry (Stirling rhyolite) of elongate shape, which is subparallel to and underlies the ore zone along its 1500 m of

Shell ring archaeological sites are one of the most visible site types along the lower South Atlantic Coast of the United States. These cultural sites are large, circular to arcuate piles of mollusk shells with some reaching over three meters in elevation and over 100 m in diameter. They are comprised largely of mollusk shells (e.g., Eastern oyster, Crassostrea virginica), but also contain early pottery, nonhuman faunal remains, and other artifacts. Our work establishes that they represent the earliest widespread Native American villages occupied year-round in the Eastern Woodlands of North America. Significantly, our results from sea-level modelling and isotope geochemistry on mollusks establish that the inhabitants of these earliest villages (ca. 5000–3800 yrs. BP) lived within a fluctuating coastal environment, harvested certain resources year-round, and targeted diverse habitats across the estuaries. Both the growth and decline of these earliest villages are associated with a concomitant rise and lowering of sea level that impacted the productivity of the oyster reef fishery along the South Atlantic Coast. Despite these large-scale environmental changes, this research indicates that Native American fishing villages persisted along the coast for over 1000 years

High-altitude conditions on the Tibetan Plateau are often depicted as an inhospitable environment for conventional farming, yet evidence shows that communities in western Tibet grew ecologically hardy crops such as-row barley (Hordeum vulgare) by at least the st millennium BCE, at locations above , meters above sea level (masl). However, little is known about the specific cultivation strategies and culinary traditions that these agropastoral communities developed. Stable carbon and nitrogen isotope compositions of grains inform growing conditions and provide much needed insight into the cultivation strategies in such a unique environment. We use δ C and δ N values of archaeologically recovered barley remains to investigate past watering and soil-management strategies. Our results infer high labor investment in manuring and watering in barley farming. This suggests an intensive cultivation system in Western Tibet, , BCE − , CE, despite the high-altitude pastoral landscape.

Elemental and isotope chemostratigraphies are used as tracers for glacial events, buildup of volcanic gases during glaciations (e.g., CO2), role of volcanism in mass extinction, salinity variation, redox state of the ocean and atmosphere, and provenance, among other applications. The use of isotope systems (C, O, S, N, Sr, Nd, Os), nontraditional stable isotope systems (e.g., Ca, Mg, B, Mo, Fe, Cr, Li), and elemental composition or elemental ratio (e.g., V, Ir, Mo, P, Ni, Cu, Hg, Rb/K, V/Cr, Zr/Ti, Li/Ca, B/Ca, Mg/Ca, I/Ca, Sr/Ca, Mn/Sr, Mo/Al, U/Mo, Th/U) in chemostratigraphy, especially across major chronological boundaries, are reviewed in this chapter. Furthermore, it is discussed what validates chemostratigraphy as a formal stratigraphic method. 1 1 NEG–LABISE, Department of Geology, Federal University of Pernambuco, Recife, PE, Brazil 2 Instituto de Ciencias Geológicas, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay 3 Deparment of Geology, Periyar Unive...

The Jucurutu Formation in the Serid o Belt, northeastern Brazil, encompasses fine-to coarse-grained amphibolite-facies marbles, locally with cross-bedding and stromatolites. Banded iron formations (BIF) at three localities in this belt comprise itabirites (actinolite-or cummingtonite-itabirite and quartzhematite itabirite) and iron ores, which are overlain by marbles of the Jucurutu Formation. Diamictites of uncertain stratigraphic position in the Serid o Belt exhibit gneiss and quartzite clasts up to 0.6 m long and a fine-grained metapelitic matrix. The C-isotope stratigraphic pathways for the Jucurutu Formation show negative d 13 C values at the base of the formation followed upsection by positive values. At the Ferro do Bonito iron Mine, values as low as À12‰ in carbonates just above the contact with underlying BIF are followed by values of ca. À5‰ and by positive values up section (þ4 to þ10‰). d 13 C values for carbonates of the Jucurutu Formation deposited on top of BIFs at the Riacho Fundo, São João do Sabugi, and Serra da Formiga sections are all positive, the contact surfaces between carbonates and BIFs being covered by weathered material. The 87 Sr/ 86 Sr values for carbonate rocks of the Jucurutu Formation are mostly in the 0.7074e0.7075 interval, a ratio commonly observed in the late Cryogenian to the early Ediacaran. The studied BIFs exhibit Cr concentrations one magnitude higher than usual and largely unfractionated Cr isotope composition, similar to average magmatic values. They are characterized by d 53 Cr values between À0.42 and À0.12‰, by Ce anomalies (Ce/Ce*) ranging from À0.4 to 0.7, by positive Eu anomalies, and by super-chondritic Y/Ho ratios (>20). The combination of geochemical parameters and association with mafic rocks resemble Algoma-type BIFs. These BIFs possibly formed proximally to hydrothermal vents, in anoxic and acidic deep waters, whereby Fe and Cr were leached from mafic or ultramafic rocks. High concentrations of Cr in the BIF with a magmatic inventory isotope composition, together with pronounced positive Eu anomalies, fit a rift depositional scenario, characterized by narrow basins and strong hydrothermal input, in which anoxic (ferruginous) conditions prevailed. This is substantiated by the occurrence of positive Ce anomalies. Their deposition was followed by carbonates which show "normal" Cr concentrations with slightly positively fractionated d 53 Cr values. These carbonates may represent post-glacial cap carbonate sequences deposited in an anoxic to slightly oxic shallow marine environment, as suggested by Ce/Ce* versus Pr/Pr* and Ce/Ce* versus Nd cross-relationships.

Processes affecting the concentration and isotopiccomposition of dissolved inorganic carbon (DIC) wereinvestigated in pore waters of two freshwaterintertidal areas of the Scheldt Estuary, Belgium. Porewater d13CDIC values from marshes andmudflats varied from -27 to +13.4‰, these very largevariations reflect the contribution of differentcarbon sources to the DIC pool.

We present the temporal variability of the oxygen (δ 18 O) and hydrogen (δ 2 H) isotope signatures in precipitation at Pasoh Forest Reserve (FR), a tropical rainforest in Peninsular Malaysia. We investigated the daily and seasonal variability of stable isotope signatures in precipitation, particularly in relation to the effects of monsoon seasons, rainfall characteristics and larger scale trends compared with those at nearby Global Network of Isotopes in Precipitation (GNIP) monitoring stations. The isotope signatures did not differ between monsoon seasons but were correlated with amount of rainfall, its intensity and duration. The effect of amount of rainfall on isotope composition was clearly detected and comparable with long-term mean monthly statistics of nearby GNIP stations. Unfortunately the effect was obscured at the daily timescale and, for monthly rainfall, not averaged over the long-term. No large deuterium excess was detected at the daily timescale for small-scale rainfall events. The δ 18 O in precipitation water was more closely correlated with the 60-day antecedent rainfall index than with the amount of rainfall each day. These findings suggested that the isotopic composition in the study area was the result of a rainout on a larger scale in addition to the local scale and specific rain events.

Long-term secular variation in the isotopic composition of seawater fixed nitrogen (N) is poorly known. Here, we document variation in the N-isotopic composition of marine sediments (δ 15 N sed) since 660 Ma (million years ago) in order to understand major changes in the marine N cycle through time and their relationship to first-order climate variation. During the Phanerozoic, greenhouse climate modes were characterized by low δ 15 N sed (∼ −2 to +2 ‰) and icehouse climate modes by high δ 15 N sed (∼ +4 to +8 ‰). Shifts toward higher δ 15 N sed occurred rapidly during the early stages of icehouse modes, prior to the development of major continental glaciation, suggesting a potentially important role for the marine N cycle in long-term climate change. Reservoir box modeling of the marine N cycle demonstrates that secular variation in δ 15 N sed was likely due to changes in the dominant locus of denitrification, with a shift in favor of sedimentary denitrification during greenhouse modes owing to higher eustatic (global sea-level) elevations and greater on-shelf burial of organic matter, and a shift in favor of water-column denitrification during icehouse modes owing to lower eustatic elevations, enhanced organic carbon sinking fluxes, and expanded oceanic oxygen-minimum zones. The results of this study provide new insights into operation of the marine N cycle, its relationship to the global carbon cycle, and its potential role in modulating climate change at multimillion-year timescales.

A flow-through cell experiment was conducted to evaluate Zn isotope fractionation during ZnS precipitation under microbially-mediated sulfate-reducing conditions. Synthetic groundwater containing 0.90 mM Zn was pumped through a cell containing creek sediment that was biostimulated to promote sulfate reducing conditions. Real-time, in situ X-ray absorption spectroscopy (XAS) was applied at the Zn K-edge to collect spectra via a Kapton window in the front of the cell over the course of the experiment. Aqueous effluent samples were collected and analysed to determine concentrations of anions and cations, and Zn isotope ratios. The flow rate was increased step-wise during the experiment to modify the residence time and produce changes in the extent of sulfate reduction, which in turn controlled the extent of ZnS precipitation. Greater enrichment in the heavier isotope in the aqueous phase relative to the input solution was associated with more extensive Zn removal. A Rayleigh curve was fit to the isotope data, where ε = − 0.27 ± 0.06 ‰ (2). Evaluation of Zn isotope fractionation under controlled flow conditions is critical to improve the efficacy of this powerful analytical technique when applied to natural systems or remediation projects in the field.

Introduction: The newly identified IIG group of magmatic iron meteorites is defined by 5 members which have the lowest Ni contents (4.1-4.6‰) of any iron meteorites [1]. On several compositional diagrams they plot near an extrapolation of trends in the magmatic IIAB irons. The IIG irons have very high P and very low S contents, and Wasson and Choe [1] proposed that liquid immiscibility had occurred in the IIAB core and that the IIG irons formed in the P-rich lower layer. The Ge isotopic composition of the (high-Au, low-Ir) IIB irons are well constrained (δ 74 Ge NIST3120a =+0.94±0.14‰, 2σ); curiously, those for IIA irons are appreciably higher (δ 74 Ge NIST3120a = +1.40±0.18‰, 2σ) [2,3]. We therefore selected a set of IIB and IIG irons to test the isotopic relationships between these two groups. We also investigated additional questions regarding the extent of Ge isotopic fractionation between metal and phosphide phase (schreibersite (FeNi) 3 P), which occur as irregular coarse inclusions in these irons. Samples and methods: Selected iron meteorites with large troilite and/or schreibersite inclusions, such as Santa Luzia (IIB), Twannberg (IIG) and Tombigbee River (IIG) have been studied for their Ge contents and Ge isotopic compositions. Metal was cut into mm-size pieces using a diamond-coated wire saw, and schreibersite was extracted using a Micromill device. These fractions were chemically processed, and Ge contents and isotopic compositions measured using the NeptunePlus MC-ICPMS (CRPG-Nancy) relative to NIST3120a Ge standard, and with a 2σ SD better than 0.26‰ [2,3]. Results-Discussion: These new Ge isotopic data show δ 74 Ge values in IIG metal (δ 74 Ge = +0.93±0.15‰) that are essentially the same as those in IIB metal (δ 74 Ge = +0.97±0.16‰). These support the view that the IIG irons were formed in the IIAB parent core. Schreibersite has very low Ge contents and strongly δ 74 Ge negative values, from 0.6-0.9 ppm Ge and δ 74 Ge values of-1.59,-2.47‰ in Santa Luzia, to 1.3 ppm Ge and δ 74 Ge =-3.4‰ in Tombigbee River. We can calculate a partition coefficient D Ge metal-schreibersite ranging from 52 to 137, and a Ge fractionation factor (Δ 74 Ge) metal-schreibersite from 2.62 to 4.28, i.e., a very low degree of Ge partitioning in the phosphide phase, with a preferential partitioning of light Ge in the schreibersite phase. These results strongly support the proposal that the IIG irons formed as the final products of the IIAB core. We found further evidence that IIA and IIB irons have distinct isotopic compositions. The reason is not clear; it seems possible that some parts of the core intermediate between IIA and IIB have not been sampled by the Earth.

The Tibetan Plateau has experienced a gradual weakening of the summer monsoon systems during the Holocene. Although lake sediment records from the Tibetan Plateau are considered to be particularly sensitive to climate variations, a holistic picture of the spatial and temporal monsoon evolution is still missing due to the interplay of different moisture-transporting wind systems (Indian summer monsoon, East Asian summer monsoon, Westerlies). Especially the late Holocene is poorly understood and well-dated highly resolved records are lacking. Closing this data gap is important since the Tibetan Plateau is a key area for understanding the climate evolution and its impact on the availability of current and future water resources in Central Asia. Hence, well-dated and highresolution records are essential to improve the understanding of the spatial and temporal monsoonal evolution. To investigate the hydrological cycle indicating past monsoon variability and its spatial and temporal heterogeneities on the southern-central Tibetan Plateau, records of several lakes were studied along a WE -transect including Nam Co, Tangra Yumco, Taro Co, and a small lake named TT Lake in the Tangra Yumco basin. In this study, a high-resolution sediment record from TT Lake (31.10° N, 86.57° E; 4,745 m asl) is presented to reveal climate dynamics since AD 440. The terminal and 9 m deep TT Lake covers ~14,500 m 2 and has a catchment of 4.6 km 2. The lake is fed by a small stream (observed in June 2012) entering the lake in the west. This stream is surrounded by wetlands extending as a flat plain at the western shore. Vegetation around TT Lake is mainly limited to these wetlands and sparse in other parts of the catchment. Three sediment short cores with 60 mm in diameter and lengths of 49.2 cm (TTL 11/1), 64 cm (TTL11/2), and 88.4 cm (TTL 12/3) were obtained in 2011 and 2012 from water depths of 8.2-8.8 m using a modified ETH-gravity coring device. By now data are available for lithology,a sedimentological core description, magnetic susceptibility (κ), XRF core scanning, statistical cluster analysis, CNS analyses, and grain size distribution. Additionally, seven radiocarbon dates were determined from bulk sediment material. Further, diatom and palynological analyses as well as 137 Cs measurements are in progress. Cores TTL 11/1, TTL 11/2, and TTL 12/3 were correlated based on lithological units and Ti patterns. Since core TTL 12/3 is the longest record retrieved from TT Lake it is considered as master core and serves as standard for all other cores. Possible event layers determined by macroscopic appearance, grain size, and XRF-data are omitted from further interpretation. The macroscopic sedimentological description of the 88.4 cm long core TTL 12/3 revealed predominantly stratified, grayish-brown to black sandy mud. Four major sediment types were determined: 1) stratified, fine silty to fine sandy, light brown to dark olive gray sediments with laminae of mm-scale; 2) dark gray almost black, massive, fine silty to fine sandy sediments; 3) sediments with a noticeable internal grading from fine sand to very fine silt; 4) one light gray coarse silty to fine sandy layer at 86-85 cm. Layers with internal grading are distinguishable at 72.8-72.2 cm, 60.0-56.2 cm, 53.2-51.5 cm, 50.4-49.6 cm, 23.5-6.0 cm, and 1.8-0 cm, whereas the thickest one from 23.6-6.0 cm contains plant remains in the coarser section and occurs in all three obtained cores. Several age determinations from core TTL 12/3 show an offset to TTL 11/2 complicating the establishment of the age-depth model. However, age determinations at 55.2 cm, 33.6 cm (both TTL 11/2), and 86.4 cm (TTL 12/3) are considered as reliable and used to generate the age model for a event-layer-cleared record TTL 12/3. Linear interpolation of the mentioned calibrated age determinations revealed a basal age of AD 440 and an age of AD 1630 at the top of the record which is also cut off by a event-layer, i.e., the record covers a time span of 1,200 years with a subdecadal resolution. The concentration of the elements K,

Detailed groundwater monitoring was carried out over a period of two years in an anoxic, river recharged aquifer of the Oderbruch polder, northeastern Germany. Isotope data from wells located in a 5 km transect along the flow direction was used to determine sources and sinks of SO 22 4 in the aquifer. The SO 22 4 originates from river water infiltration and from oxidative dissolution of FeS 2 within the alluvial loam covering the aquifer sands. A change of confined hydraulic conditions near the river to unconfined conditions in the central polder effects the hydrochemistry of the aquifer. The confined areas are dominated by sulfate reduction. Increasing d 34 S 2SO 4 values suggest continuous but slow (t 1=2 ¼ 50 years) sulfate reduction from the beginning of inflow onwards with d 34 S 2SO 4 values ranging from þ 1.8 to þ44.7‰ versus CDT and an enrichment factor of 233‰. A zone with a strong sulfate depletion (d 34 S 2SO 4 of up to þ85.7‰) exists in a shallow microenvironment rich in solid-phase organic carbon between river and levee. In the unconfined areas of the central polder, a SO 22 4 plume with concentrations exceeding the original river water content indicates FeS 2 oxidation by O 2 and/or NO 2 3 within the alluvial loam. The lowered d 34 S 2SO 4 value reflects the input of the isotopically lighter SO 22 4 from the sulfide.

Carbon and sulfur isotopic data are helpful in understanding environmental conditions under which soils are formed. Soils from 18 sampling sites along a climotoposequence from higher Laleh Zar Mountains (4,351 m above sea level with xeric-mesic soil moisturetemperature regimes) to Shahdad depression (250 m above sea level with aridhyperthermic soil moisture-temperature regimes) in Kerman Province, central Iran, were studied. δ 13 C values of the soil organic carbon varied between-20.6 ‰ and-26.9 ‰ PDB. δ 13 C values of pedogenic carbonates varied between-2.2 ‰ and +2.2 ‰ PDB and a decreasing trend was observed downward in the climotoposequence. A positive correlation (r= 0.6) was found between δ 13 C and δ 18 O values in the lower arid landscape, but a different relationship (r= 0.37) in the upper Mediterranean climatic positions was observed. It seems that the presence of more C3 plants under stress and more decomposition of organic matter in lower positions of the landscape has taken place. δ 13 C values of soil organic carbon and pedogenic carbonates and their trend along the gradient showed that higher proportion of C3 plants at lower elevations and presence of more C4 plants in the past history of upper landscape positions may have been experienced. Mean δ 34 S value of 11.3‰ showed that lower Cretaceous sea sulfate may have been the source of sulfur in the area. Mean δ D and δ 18 O values of-51.2‰ and +6.0‰ in gypsum crystallization water showed that direct deposition from a solution saturated with gypsum is the only probable mechanism of gypsum formation in the area.

The Ansil Cu-Zn volcanic-hosted massive sulfide deposit is located approximately 14 km north-northwest of Rouyn-Noranda, Quebec, within the Blake River Group of the Archcan southern Abitibi greenstone belt. The deposit is the second lowest within the Central Mine sequence, a series of bimodal rhyolite-andesite formations that fill in the Noranda cauldron, host to 17 volcanic-hosted massive sulfide deposits. The deposit consists of a single massive sulfide lens situated at the contact between rhyolite of the Northwest formation and overlying andesRe of the Rusty Ridge formation. The rhyolite flow forms a ridge up to 500 m high which was inundated by the andesitc flows. The orebody is hosted within a unit of quartz porphyritic, finely layered, felsic volcaniclastite (Cranston tuff) that fills in an east-west-trending graben formed on the upper surface of the rhyolite flow. At the east end of the graben the Cranston tuff is interlayered with a thin unit of dacite flows. The deposit lies within an extensive discordant alteration zone characterized by feldspar destruction and Na depletion. The zone extends from 400 m below the deposit at the contact of the synvolcanic Flavrian Intrusive Complex to over 400 m above the deposit. This alteration zone is controlled by a fault system that served as a focus for hydrothermal fluid upfiow from the beginning of cauldron formation until the end of the first cauldron cycle. Within the Na depletion zone there are three distinct alteration facies associated with the orebody. Early hydrothermal activity is defined by hydrothermal explosion breccias that formed along the base of the east-west trending graben walls. They were filled with finely banded quartz-albitesphalerite-pyrite, and the wall rock altered to sericite-quartz, with finely disseminated sphalerite and pyritepyrrhotite. The graben was then filled with the Cranston tuff, which was selectively altered and mineralized by the Zn-rich fluid. Subsequent development of northerly trending faults was accompanied by the upfiow of Cu-rich fluid that selectively chloritized the footwall rhyolite below the graben floor and formed a morphologically complex pyrrhotite-chalcopyrite-rich vein stockwork. The Cu-rich mineral assemblage progressively replaced the Cranston tuff in the center of the graben, overprinting previously deposited sphalerite-mineralized tuff. The Cu-rich fluids also selectively altered overlying andesitic flow breccia and hyaloclastite, replacing parts of the unit with massive pyrrhotite-chalcopyrite. The replaced Cranston tuff forms the layered eastern half of the orebody, whereas the steep-sided dome at the west end is a product of andesitc flow replacement. This hydrothermal stage was also responsible for the continued replacement of interflow hyaloclastite for up to 400 m above the orebody. The third stage of hydrothermal activity resulted in the formation of calc-silicate alteration assemblages, and then a footwall magnetite vein stockwork and replacement of sections of the massive sulfide orebody by massive magnetite. The Ansil deposit is the product of shallow, subsea-floor replacement, with the primary permeability of the host rocks controlling the morphology of the orebody and associated vein stockworks. It began to form in shallow water (200-300 m) on the graben floor and continued to evolve during infilling of the graben by felsic mass flows, and burial of the footwall rhyolite by andesitic flows. Late-stage development of the orebody took place under a 500-m thickness of volcanic flows at an unknown water depth. Three compositionally distinct fluid phases were responsible for the development of the Ansil system: an Si-Zn-K-rich fluid responsible for the hydrothermal brecciation of the graben floor and sphalerite precipitation within the quartz porphyritic mass flow; a higher temperature Fe-Cu-Au-Ag-rich fluid which formed extensive footwall and hanging wall, chlorite-rich, alteration zones, as well as the pyrrhotite-chalcopyrite-rich vein stockwork and massive sulfide lens; and finally, a CaFe -CO2-rich fluid which formed calc-silicate alteration assemblages, and then partially replaced the massive sulfide lens with massive magnetite.

Ferromanganese nodule fields and hardgrounds have recently been discovered in the Cadiz Contourite Channel in the Gulf of Cadiz (850-1000 m). This channel is part of a large contourite depositional system generated by the Mediterranean Outflow Water. Ferromanganese deposits linked to contourites are interesting tools for palaeoenviromental studies and show an increasing economic interest as potential mineral resources for base and strategic metals. We present a complete characterisation of these deposits based on submarine photographs and geophysical, petrographic, mineralogical and geochemical data. The genesis and growth of ferromanganese deposits, strongly enriched in Fe vs. Mn (av. 39% vs. 6%) in this contourite depositional system result from the combination of hydrogenetic and diagenetic processes. The interaction of the Mediterranean Outflow Water with the continental margin has led to the formation of Late Pleistocene-Holocene ferromanganese mineral deposits, in parallel to the evolution of the contourite depositional system triggered by climatic and tectonic events. The diagenetic growth was fuelled by the anaerobic oxidation of thermogenic hydrocarbons (6 13 C PDB =-20 to-37%0) and organic matter within the channel floor sediments, promoting the formation ofFe-Mn carbonate nodules. High 87Sr¡86Sr isotopic values (up to 0.70993 ± 0.00025) observed in the inner parts of nodules are related to the influence of radiogenic fluids fuelled by deep-seated fluid venting across the fault systems in the diapirs below the Cadiz Contourite Channel. Erosive action of the Mediterranean Outflow Water undercurrent could have exhumed the Fe-Mn carbonate nodules, especially in the glacial periods, when the lower core of the undercurrent was more active in the study area. The growth rate determined by 23Drhexcess¡232Th was 113 ± 11 mm¡Ma, supporting the hypothesis that the growth of the nodules records palaeoenvironmental changes during the last 70 ka. Ca-rich layers in the nodules could point to the interaction between the Mediterranean Outflow Water and the North Atlantic Deep Water during the Heinrich events. Siderite-rhodochrosite nodules exposed to the oxidising seabottom waters were replaced by Fe-Mn oxyhydroxides. Slow hydrogenetic growth of goethite from the seawaters is observed in the outermost parts of the exhumed nodules and hardgrounds, which show imprints of the Mediterranean Outflow Water with low 87Sr¡86Sr isotopic values (down to 0.70693 ± 0.00081). We propose a new genetic and evolutionary model for ferromanganese oxide nodules derived from ferromanganese carbonate nodules formed on continental margins aboye the carbonate compensation depth and dominated by hydrocarbon seepage structures and strong erosive action of bottom currents. We also compare and discuss the generation of ferromanganese deposits in the Cadiz Contourite Channel with that in other locations and suggest that our model can be applied to ferromanganiferous deposits in other contouritic systems affected by fluid venting.