High δD Research Articles

Comparison of an isotopic atmospheric general circulation model with new quasi-global satellite measurements of water vapor isotopologues

We performed an intensive comparison of an isotope-incorporated atmospheric general circulation model with vapor isotopologue ratio observation data by two quasi-global satellite sensors in preparation for data assimilation of water isotope ratios. A global Isotope-incorporated Global Spectral Model simulation nudged toward the reanalysis wind field, atmospheric total column data from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) on Envisat, and midtropospheric (800 to 500 hPa) data from Tropospheric Emission Spectrometer (TES) on Aura were used. For the mean climatological δD of both the total atmospheric column and the midtroposphere layer, the model reproduced their geographical variabilities quite well. There is, however, some degree of underestimation of the latitudinal gradient (higher δD in the tropics and lower δD in midlatitudes) compared to the SCIAMACHY data, whereas there is generally less disagreement except lower δD over the Maritime Continent compared to the TES data. It was also found that the two satellite products have different relationships between water vapor amount and isotopic composition. Particularly, atmospheric column mean δD, which is dominated by lower-tropospheric vapor, closely follows the fractionation pattern of a typical Rayleigh-type “rain out” process, whereas in the midtroposphere the relationship between isotopic composition and vapor amount is affected by a “mixing” process. This feature is not reproduced by the model, where the relationships between δD and the vapor are similar to each other for the atmospheric column and midtroposphere. Comparing on a shorter time scale, it becomes clear that the data situation for future data assimilation for total column δD is most favorable for tropical and subtropical desert areas (i.e., Sahel, southern Africa, mideastern Asia, Gobi, Australia, and the southwest United States), whereas the available midtropospheric δD observations cover wider regions, particularly over tropical to subtropical oceans.

The influence of microhabitat, moisture and diet on stable-hydrogen isotope variation in a Neotropical avian food web

Abstract:The application of stable-hydrogen isotope (δD) measurements to the study of animal movement, resource use and physiology depends on understanding factors driving variation in δD in animal tissues. The source of micro-scale variation in δD is poorly known, yet understanding micro-scale patterns of δD could shed light on important ecological processes and improve our abilities to track animal movements. Using linear and additive models, we explored the influence of micro-scale habitat use, moisture and diet on tissue δD values of Nicaraguan cloud-forest birds. Using mist nets, we captured 211 individuals of 22 resident Neotropical species at 500–1390 m asl and collected feather and claw samples. Based on three years of data from year-round sampling, our results suggest that microhabitat, seasonal shifts in moisture δD, and diet all influence bird tissue δD values. Our model results reveal a previously undescribed microgeographical effect on δD, where foraging level (understorey versus overstorey) and foraging location (forest interior versus adjacent coffee plantation) were significant predictors of δD values in bird claws and feathers. Mean claw and feather δD values among species varied from −83‰ to −19‰. Top models for claws and feathers explained 57% and 52% of variation in δD respectively. Direct comparisons of understorey (mean ± SD of −30‰ ± 15‰) versus overstorey (−50‰ ± 15‰) claw values suggest that δD may be useful in tracking vertical, micro-scale movement. Higher δD values in forest understorey birds reveal a heavy reliance upon recycled, fog moisture. Fragmentation and climate change may result in increasingly desiccated cloud forest that may exert a more negative influence on the food webs of understorey species that seem to be supported by recycled sources of moisture in the dry season.

Chlorine isotope evidence for multicomponent mantle metasomatism in the Ivrea Zone

Metasomatism of the Finero peridotite (Ivrea Zone, Italy) has previously been ascribed to mantle melts generated in a rift or plume setting, and/or to subduction fluids. We combine Cl, H, and O stable isotope geochemistry with petrologic and major and trace element data to further constrain sources and setting of the metasomatic agents and to assess fluid infiltration mechanisms. Relatively unmetasomatized samples from the Balmuccia peridotite serve as our control population (δ 37Cl = − 0.7 to + 0.4‰; n = 13). We analyzed 47 samples from four Finero rock types: (1) spinel harzburgite with minor amphibole ± phlogopite, (2) harzburgite with several percent phlogopite ± amphibole, (3) amphibole-rich segregations, and (4) phlogopite segregations. δ 37Cl values range from − 2.0 to + 2.1‰ and cannot be reconciled with metasomatism by a single homogeneous fluid. Three components describe most of the sample variability: (A) endmember spinel peridotite, as represented by the Balmuccia samples; (B) a “hydrated clinopyroxenite” component with low δ 37Cl and high Si, Al, Ca and δD responsible for formation of Type 3 amphibole segregations; and (C) a component with high δ 37Cl, δD, Cl, Cr, LILE, and HFSE that formed Type 4 phlogopite segregations. Type 1 and 2 peridotite compositions are consistent with different degrees of mixing between these three components. Centimeter-scale isotopic gradients indicate that much of the fluid infiltration was channelized rather than pervasive. The data support metasomatism in a forearc wedge, with fluids sourced from at least two subducted components with distinct chemical and isotopic compositions (e.g., δ 37Cl < − 2‰ and >+2‰). Overall, our results show that relatively shallow and heterogeneous fluid release events from the downgoing slab can profoundly modify the mantle wedge.

Variation in n-alkane δD values from terrestrial plants at high latitude: Implications for paleoclimate reconstruction

The molecular hydrogen isotope composition ( δD) of leaf waxes from terrestrial plants is increasingly used to infer hydrological characteristics of ancient high latitude climates. Analysis of the hydrogen isotope composition of n-alkanes ( δD n -alkane) from a global dataset of individual plants growing at low and middle latitudes indicates that plant ecological life form is an important factor in determining the hydrogen isotope fractionation. However, environmental and biological controls of high latitudinal leaf wax δD values are poorly understood because of a lack of δD records from modern flora in these regions. We previously noticed smaller apparent hydrogen isotope fractionations between n-alkanes and environmental water ( ε alk - water ) in deciduous trees growing at high latitudes (>59°N; Liu, W.-G., Yang, H., 2008. Multiple controls for the variability of hydrogen isotopic compositions in higher plant n-alkanes from modern ecosystems. Global Change Biology 14, 2166–2177.) To further examine these issues, we measured δD n -alkane from a variety of plants that inhabit high latitude environments and added critically needed leaf wax δD data from grass and herbs to the existing global δD n -alkane database. Inclusion of these new data with the existing global dataset ( n = 408) confirms plant ecological life form as an important control for leaf wax δD variation for terrestrial plants living at high latitudes. Our results suggest that, while precipitation δD is captured in these high latitude plants, physiological characters such as leaf area, venation pattern and hydraulic system, that enhance transpiration rate during summer growth, may impart δD n -alkane differences among plants with different ecological life forms.

Understanding the migration ecology of European red admirals Vanessa atalanta using stable hydrogen isotopes

Tracking migratory movement of small animals with variable migration patterns is difficult with standard mark–recapture methods or genetic analysis. We used stable hydrogen isotope (δD) measurements of wings from European red admirals Vanessa atalanta to study several aspects of this species’ migration. In the central part of southern Europe we found large differences in δD values between red admirals sampled in autumn and spring supporting the hypothesis that reproduction takes place in the Mediterranean region during winter. There was also an apparent influx to southern Europe in the spring of individuals with a more southerly origin, since many samples had higher δD values and similar to those expected from coastal areas of North Africa. We found a clear seasonal difference in the δD values of red admirals sampled in northern Europe. Spring migrants arriving in northern Europe generally had high δD values that indicated a southerly origin. In autumn, δD values suggested that red admirals were mostly from regions close to the sampling sites, but throughout the sampling period there were always individuals with δD values suggesting non‐local origins. The migration pattern of this species is supposedly highly variable and plastic. δD differences between individuals in the western part of Europe were generally small making migratory patterns difficult to interpret. However, butterflies from western Europe were apparently isolated from those from north‐eastern Europe, since δD values in the western region rarely corresponded to those of autumn migrants from the north‐east. Use of δD data for inferring butterfly migration in Europe is complex, but our study showed that this technique can be used to help uncover previously unknown aspects of red admiral migration.

Paleodietary analysis of the prehistoric population of the Canary Islands inferred from stable isotopes (carbon, nitrogen and hydrogen) in bone collagen

Nitrogen and carbon isotope compositions were measured in the bone collagen from a total of 86 prehispanic samples of the Canary Islands, and hydrogen in 70, all of them with enough amount of bone collagen, and adequate N and C content. These samples belong to prehistoric population of El Hierro ( n = 27), Tenerife ( n = 18), and Gran Canaria ( n = 41). Isotope compositions were also obtained for prehistoric and modern food resources that were likely consumed by these people. Marked differences were observed among the three islands regarding the three isotopes analyzed: the δ 15N values were highest among the population of Gran Canaria (10.8‰ ± 0.9‰), who also showed the highest δD values (7 ± 8‰). The population of El Hierro showed the highest δ 13C values (−18.6‰ ± 0.7‰). These data suggest a high consumption of marine products by the population from El Hierro, and also an important consumption of terrestrial meat or marine, piscivore fish, by the population from Gran Canaria, together with domesticated C 3 plants (barley and/or wheat), fruits of Ficus carica and other wild species, and goat products. Additionally, marked differences were observed between men and women, which suggest that women consumed a more vegetal-based diet, a finding which is in agreement with the higher proportion of teeth with carious lesions among women. In our study, a high δD is associated with a high δ 15N, suggesting a relation with animal protein (either marine or terrestrial) consumption.

Stable and noble gas isotopic study of thermal and groundwaters in northwestern Hokkaido, Japan and the occurrence of geopressured fluids

Copyright © 2010 by The Geochemical Society of Japan. owing to interaction with the surrounding rocks. In several areas, fossil sea water was found to have δ18O values of +5 to +8‰ due to the oxygen isotopic shift caused by the interaction, but to retain almost the same Cl concentration as fresh sea water (e.g., Sakai and Matsubaya, 1974; Mizukami et al., 1977; Shibata et al., 2005). At depths below ca. 2 km in sedimentary regions associated with oil and/or natural gas, formation waters tend to be geopressured fluid with pressures between hydrostatic and lithostatic values (e.g., Myers, 1968; Jones, 1970; Oki et al., 1999; Xu et al., 2006). The δD and δ18O data show that most geopressured fluid can be explained as a mixture of fossil sea water and local meteoric water, with an oxygen isotope shift due to rock-water interaction. Recently, fluids that have oilfield-like characteristic, with unusually high δD (–20‰) and low Cl concentrations (ca. 6,000 mg/L) have been observed along faults in the Horonobe area (Ishii et al., 2006). These fluids might have originated as a mixture between sea water and Stable and noble gas isotopic study of thermal and groundwaters in northwestern Hokkaido, Japan and the occurrence of geopressured fluids

Hydrogen isotopic ratios of plant wax n-alkanes in a peat bog deposited in northeast China during the last 16 kyr

Based on paleoclimatic reconstructions using various proxies, the Holocene Climate Optimum (10.5–6ka) has been characterized as a warmer and wetter period in most of East Asia. The summer monsoons associated with the East Asian Monsoon evidently intensified and extended further inland from the Pacific Ocean, a source region of moisture. A notable exception to this general pattern exists in northeast China, where less wet conditions are recorded. We determined molecular compositions of individual plant wax hydrocarbons and their hydrogen isotope compositions (δD values) in a radiocarbon-dated peat core recovered from the Hani marsh in Jilin Province (China) and confirmed that the temperature-dependent effective precipitation in northeast China decreased during the Holocene Climate Optimum. A combination of Paq, an indicator of the relative contribution of aquatic to terrestrial plants, and the difference in δD between low (C23, C25 and C27) and high molecular weight (C31) n-alkanes in the Hani peat bog indicates a dramatic change in vegetation from the deglaciation to the Holocene. No significant differences were observed between the δD values of low and high molecular weight n-alkanes with relatively high δD values and low Paq during the early Holocene, indicating that all n-alkanes were produced by evapotranspiration-sensitive terrestrial plants during that time. However, lower δD values of mid-chain n-alkanes (C23, C25 and C27) relative to the long chain n-alkane (C31), together with higher Paq values during the deglaciation (14–11ka), suggest an increase in the contribution of aquatic plants and a higher water level during the period. The study demonstrates that northeast China was under a markedly wetter climate condition during the late deglaciation. For the 16kyr record in the Hani peat sequence, we infer that moisture delivery by the East Asian Monsoon was relatively invariable in northeast China, but increased evaporation during the warmer Holocene Climate Optimum reduced the effective precipitation, defined by the balance between precipitation and evaporation.

Hydrogen isotopes in Mariana arc melt inclusions: Implications for subduction dehydration and the deep-Earth water cycle

Water is carried into Earth's mantle at subduction zones via hydrous mineral phases in subducting lithospheric plates. A certain fraction of this water is released during subduction and leads to the generation of arc volcanism. The extent of lithosphere dehydration and associated hydrogen isotope fractionation are critical to understanding the global water cycle. To further understand the origin of subduction-related fluids and how water is exchanged between Earth's reservoirs, we have analyzed volatiles and δD of magmatic melt inclusions from the Mariana arc. We find high δD values, ranging from − 55‰ to − 12‰, indicating release of D-enriched fluids from the subducting plate into the mantle wedge. A consequence of this process is the formation of complementary hydrous mantle components that are D-enriched (mantle wedge) and D-depleted (slab). This implies that ocean island basalts (OIB) with recycled slab components should be characterized by low δD, while high δD signatures are expected from OIB containing recycled mantle wedge peridotite. These results have important implications for the hydrogen isotope evolution of terrestrial H 2O reservoirs. Based on the magnitude of subduction-related fractionations, we show that terrestrial δD variations are inconsistent with steady-state exchange of water between the mantle and surface reservoirs. We suggest that the subduction process is responsible for the present-day δD difference observed between Earth's major water reservoirs.

The LaPaz Icefield 04840 meteorite: Mineralogy, metamorphism, and origin of an amphibole- and biotite-bearing R chondrite

The R chondrite meteorite LaPaz Icefield (LAP) 04840 is unique among metamorphosed, non-carbonaceous chondrites in containing abundant OH-bearing silicate minerals: ∼13% ferri-magnesiohornblende and ∼0.4% phlogopite by volume. Other minerals include olivine (Fo 62), orthopyroxene (En 69Fs 30Wo 1), albite (An 8Ab 90Or 2), magnetite, pyrrhotite, pentlandite, and apatite. Ferromagnesian minerals are rich in Fe 3+, as determined by Mössbauer spectrometry and electron microprobe chemical analyses. Fe 3+/Fe tot values are olivine ⩽5%, amphibole 80%, phlogopite 65%, and magnetite 42%. Mineral compositions are nearly constant across grains and the section, except for a small variability in amphibole compositions reflecting the edenite exchange couple ( ANa + IVAl ↔ A□ + Si). These mineral compositions, the absence of Fe–Ni metal, and the oxygen isotope data support its classification as an R (Rumuruti) chondrite. LAP 04840 is classified as petrologic grade 5, based on the chemical homogeneity of its minerals, and the presence of distinctly marked chondrules and chondrule fragments in a fine-grained crystalline matrix. The mineral assemblage of LAP 04840 allows calculation of physical and chemical conditions at the peak of its metamorphism: T = 670 ± 60 °C from a amphibole–plagioclase thermometer; P H 2 O between 250 and 500 bars as constrained by the assemblage phlogopite + orthopyroxene + olivine + feldspar and the absence of diopside; P CO 2 unconstrained; f O 2 at QFM + 0.5 log units; log ( f HF / f H 2 O ) ≈ - 5.8 ; log ( f HCl / f H 2 O ) ≈ - 3.3 ; and log ( f HCl / f HF ) ≈ - 2.6 . The hydrogen in LAP 04840 is very heavy, an average δD value of +3660 ± 75‰ in the magnesiohornblende. Only a few known sources of hydrogen have such high δD and are suitable sources for LAP 04840: ordinary chondrite phyllosilicates (as in the Semarkona chondrite), and insoluble organic matter (IOM) in ordinary chondrites and CR chondrites. Hydrogen from the IOM could have been released by oxidation, and then reacted with an anhydrous R chondrite (at high temperature), but it is not clear whether this scenario is correct.

Paleohydrological changes during the last deglaciation in Northern Brazil

We here report a reconstruction of hydrological balance variations in Northern Brazil for the last 20 ka deduced from the δD values of aquatic and land plant molecules extracted from the sediment infill of Lake Caçó. Our reconstructed precipitation, lake water isotope ratio and evaporation–evapotranspiration isotope effect allows us to obtain an estimate of moisture balance, and, to a lesser extent, precipitation amount and seasonality changes. During the end of the Last Glacial Maximum (LGM, between ca 20 and 17.3 ka), high δD values and smaller fractionation of leaf waxes indicate an arid to semi-arid climate with a long lasting dry season. An abrupt change towards much wetter conditions occurred within ca 500 years from 17.3 to 16.8 ka, as shown by a 50‰ decrease in D/H ratios and a marked increase in H isotopic fractionation of leaf waxes. This abrupt isotopic change coincides with a major transformation from savanna-dominated vegetation to humid rain forest around the lake, based on pollen data. Comparisons with other paleo-precipitation records from South American sites indicate that Lateglacial humid conditions were controlled by intensification of the ITCZ and/or a southward shift of its mean position across our study site. Our isotope data show only a small rise in aridity during Younger Dryas event (13–11.5 ka). Although the Holocene was not screened in details, D/H ratios of terrestrial and aquatic compounds show near constant offsets, suggesting stable and relatively humid climate conditions during this period.

English

A deuterium tagged rainfall event with a δD of +213 was applied to the top surface of an experimental covered waste rock pile in May of 2003. The tracer experiment was designed to resolve the spatial variability of infiltrating water and to estimate the magnitude and rate of flow within covered waste rock. The five meter high pile was deconstructed one year later and waste rock was sampled along vertical profiles at 10cm increments. Pore waters were extracted from the waste rock using the centrifugal method. The measured δD values range from -90 to background levels of approximately -130 with a few zones of locally high δD values deeper than three meters in the pile. Variability between individual vertical δD profiles are observed within the 8x8 meter area. The combination of the spatial variability and the deep δD values yield strong evidence for intermediate scale (~15 cm) preferential flow.

Hydrogen Concentration and Stable Isotopic Composition of Methane in Bubble Gas Observed in a Natural Wetland

Bubble gas samples were collected at three different vegetation sites and two different depths (surface and 40 cm) in a natural wetland, Mizorogaike in Kyoto city, to investigate hydrogen concentration and δD and δ13C values of CH4. Hydrogen concentration in bubble gas varied from 1 to 205 ppm, and that collected during summer was higher than that during winter. Bubble samples collected at 40 cm at sphagnum site usually showed the lowest H2 concentration among the samples collected at the three sites and two depths on the same day. The lowest H2 concentration observed at 40 cm at sphagnum site was similar to that expected for environmental water in which H2 producer and consumer need to assemble for free energy requirement. Low δ13C and high δD (relatively small hydrogen fractionation; \(\Delta\delta\hbox{D}_{{\rm water}-{\rm CH}_4}\cong 220\)‰) were observed in CH4 collected at a deeper (40 cm) layer of sphagnum site during winter, when H2 concentration was low (typically 2–4 ppm). On the other hand, CH4 in the bubble samples collected during summer showed high δ13C and low δD (relatively large hydrogen fractionation; \(\Delta\delta\hbox{D}_{{\rm water}-{\rm CH}_4}\cong300\)‰), when H2 concentration was high. Carbon and hydrogen isotope fractionation during CH4 production were variable, possibly depending on the H2 concentration and the production rate. Difference in enzymatic reaction and magnitude of hydrogen isotope exchange among water, CH4, and H2 may cause the variation in isotope fractionation during CH4 production.

Functional imaging of breast tissue and clinical application

A novel approach to image hemoglobin concentration(ΔD hb) and oxygen saturation (ΔD oxy) of breast tissue is presented. The scenograph of dual-wavelength (760 and 850 nm) near infrared lights through breast tissue is acquired by high sensitive charge coupled device (CCD) camera. The evaluation criterion of the difference of ΔD hb and ΔD oxy between detected and referenced breast tissue can be obtained by a calculation formula without complicate caculation. This approach is applied to clinic detection in breast tissue. The ongoing clinical experiments indicate that malignant tumor usually exhibits characterize of “higher ΔD hb and lower ΔD oxy”, while benign lesion often shows “lower ΔD hb and higher ΔD oxy” or other characters. So it is useful to assist the diagnosis of breast disease.

Kaolin Deposits from the Northern Sector of the Cunene Anorthosite Complex (Southern Angola)

AbstractThe Mevaiela kaolin deposits are located in the northern part of the anorthositic-gabbro massif within the Cunene complex (southern Angola) and were formed by the alteration of basic anorthosites and gabbros. The Mevaiela area is part of an elevated region which is located between two extensive NNW-SSE fracture systems. Several kaolinite samples were collected from a quarry (main excavation) and from drill-holes as well as from surficial occurrences in the Cunene complex. Chemical analyses, X-ray diffraction, differential thermal analysis, scanning electron microscopy and isotope analyses were performed in order to model the kaolinite occurrences. The alteration of the anorthosite to kaolin approaching the main excavation is characterized by significant decrease in alkaline-earth and transition metals (Ca, Mg, Fe, Co, Ni and Mn) between the average anorthosite and the kaolin. The crystallinity indices suggest that the kaolin contains kaolinite with a reasonably well ordered structure and near the transition between T (triclinic) and pM (pseudo monoclinic).Mineral exploration tools have been evaluated during this study to assist in future kaolin exploration in the Cunene anorthosite complex.Isotopic analysis of O and D indicates that Ca-feldspar alteration is essentially due to meteoric fluids, over a different range of temperatures. Furthermore, the presence of quartz-feldspar veinlets in the kaolinite bodies could be the result of hydrothermal activity linked to post-anorthosite granite intrusions of the so-called ‘red granite’. Kaolinite from Cunene plots on or close to the kaolinite line into the ‘warm temperature in tropical region’ area (surficial samples). Samples from drill-holes plot on the left and show the largest displacement from the KS line; these samples also have a relatively reduced δD range of values (−65 to −98%). However, if supergene processes take place in the presence of waters of meteoric origin at temperatures similar to typical surface temperatures, the clays thus formed should plot either in the vicinity of the KS line or be displaced towards lower δO18 and higher δD, depending on both the temperature and relative proportion of clay to water.

Hydrogen Isotopic Compositions of Pyroxenes in Nushan Peridotite Xenoliths, SE China

Abstract Hydrogen isotopic compositions of pyroxenes in peridotite xenoliths from the Nushan volcano, Anhui Province, SE China have been obtained using an ion probe (Cameca 1270). D/H ratios are constant within a single grain and among the different grains from the same sample. The lack of correlation between the D/H ratios and the hydrogen contents indicates that the hydrogen isotopic compositions are inherited from their mantle source. Combining with the δD values of coexisting amphiboles, it is inferred that the Nushan mantle experienced at least a two-stage metasomatic event. One was responsible for formation of amphiboles with extremely variable δD values, and the other was probably responsible for the high δD values (up to −20‰) of some clinopyroxenes from peridotites, clinopyroxene and mica megacrysts. High δD values point to a subduction-related fluid being involved in one metasomatic event. The primary δD values (−90‰ to −140‰) of the Nushan pyroxenes, together with data gleaned from the literature, suggest that the D/H ratios of the nominally anhydrous mineral reservoir might have differed from that of the other mantle hydrogen in being relatively depleted in D.

Compound specific D/ H ratios and molecular distributions of higher plant leaf waxes as novel paleoenvironmental indicators in the Chinese Loess Plateau

We measured D/ H ratios of individual long chain leaf wax n-alkanes isolated from a loess profile spanning the last 130 ka from Xifeng, China. The δD values show large variation (−140 to −200‰) for the past 130 ka and are highly correlated with changes in magnetic susceptibility (MS), an accepted proxy for past monsoon circulation in the Chinese Loess Plateau. Peaks in high δD values (−140 to −160‰) coincide with low MS values for loess sections formed under relatively dry conditions (marine isotope stages, MISs, 2 and 4), whereas peaks in low δD values (−190 to −200‰) coincide with high MS values for paleosol sections formed under relatively wet conditions (MISs 1, 3 and 5). We attribute the isotopic variations to the combined effects of varying aridity, which controls the soil and leaf water evaporation, and temperature and monsoon intensity, which alter the D/ H ratios of precipitation. We also discovered a strong negative correlation between the molecular distributions (ratios of C 31/C 29 and C 31/C 27 n-alkanes) and the δD values of n-alkanes, based on studies of modern plants and the Xifeng loess sequence. The complex relationship between MS and monsoon circulation has been difficult to understand mechanistically. However, the climatic controls on the D/ H ratios of individual long chain n-alkanes and C 31/C 29 n-alkane ratios can be readily demonstrated and calibrated from modern plants and surface soils. Therefore, these new molecular and isotopic proxies have potential as quantitative proxies for paleoenvironmental reconstruction in the Chinese Loess Plateau.

Low-latitude meteoric fluid flow along the Cloncurry Fault, Cloncurry district, NW Queensland, Australia: geodynamic and metallogenic implications

Hydrothermal alteration within the Mount Isa Block (MIB) is typically largely to have ceased at the end of the Isan Orogeny (ca. 1.50 Ga). However, late, large brittle quartz-rich vein systems, including those of the Cloncurry Fault, cut Mesoproterozoic tectonic fabrics, intrusions and products of regional Na–Ca hydrothermal alteration. Associated features display affinities to iron oxide–Cu–Au ore deposits, including specular hematite-bearing veins and Cu–(Au–U–LREE–Ba) mineralization. Stable isotope data suggest late veins in the vicinity of the Cloncurry Fault, Eastern Fold Belt (EFB), formed from fluids with δ 18O H 2O and δD H 2O (250 °C) of −4‰ to +3‰ and −22‰ to −4‰, respectively. The high δD H 2O , moderate δ 18O H 2O and CaCl 2–NaCl-rich character of the saline fluids indicates they were mixtures of low-latitude meteoric fluids and evaporite-derived basinal brines, which, with time, became progressively dominated by meteoric water, deposited barite and cooled. The low-latitude meteoric signature demonstrates that the fault-fracture systems were active when in equatorial regions. Paleomagnetic data for the MIB, and the Australian protocontinent, together with structural and thermal considerations, and geochronological arguments suggest the veins probably formed sometime after 1.10 Ga, and potentially as late as during the Alice Springs Orogeny (ca. 0.34 Ga). The late quartz veining was unrelated to two phases of regional Na–Ca alteration and economically significant Fe oxide–Cu–Au mineralization at 1.60–1.58 and 1.53–1.50 Ga.

Theoretical investigations of the microscopic spin Hamiltonianparameters including the spin–spin and spin–other-orbit interactions forNi2+(3d8) ions in trigonal crystal fields

The microscopic origin of the spin Hamiltonian (SH) parameters forNi2+(3d8) ions in a trigonaltype I symmetry (C3v,D3d,D3) crystal field (CF) is studied. In addition to the spin–orbit (SO) interaction,we consider also the spin–spin (SS) and spin–other-orbit (SOO) interactions.The relative importance of the four (SO, SS, SOO, and combined SO–SS–SOO)contributions to the SH parameters is investigated using the CFA/MSH package andthe complete diagonalization method (CDM). The SO mechanism is dominantfor all CF parameter (CFP) ranges studied, except where the contributionsDSO to the zero-field splitting(ZFS) parameter D change sign. For the trigonal CFP, due to the other three mechanisms exceedsDSO. Although|DSOO| is quite small,the combined |DSO−SOO| is appreciable. The SO-based perturbation theory (PT) works generally well for theg-factors: and , while it fails for D in the vicinity of vc and for large and v>0. The high percentagediscrepancy ratio δD = 2020% forvc indicates unreliabilityof DSO (in PT). Applicationsto Ni2+ ions at trigonalsymmetry sites in LiNbO3, α-LiIO3, andAl2O3, areprovided. The theoretical SH parameters are in good agreement with the experimental data. The low symmetry(C3) effects inducedby the angle φ are tentatively studied, but appear to be quite small.

Origin and history of waters associated with coalbed methane: 129I, 36Cl, and stable isotope results from the Fruitland Formation, CO and NM

The Fruitland Formation of the San Juan Basin was deposited during the late Cretaceous and is associated with significant reservoirs of coalbed methane (CBM). The purpose of this study is to determine the origin and history of waters associated with the formation, using long-lived cosmogenic and stable isotope systems. Ratios of 129I/I and stable isotope values (δD and δ 18O) were determined in waters from close to 100 wells, 36Cl/Cl ratios for a subset of these samples. A significant group of samples has 129I/I ratios between 100 × 10 −15 and 200 × 10 −15, indicating minimum iodine ages close to 60 Ma. If these ages are corrected for the addition of fissiogenic 129I, they are compatible with the depositional age of the Fruitland Formation (Late Cretaceous). Several sets of waters are clearly present within the data. A group dominated by infiltration of recent surface waters is restricted to the uplifted basin margins, with a lateral extent of less than 5 km from outcrop, and is characterized by 129I/I ratios in excess of 1500 × 10 −15 and meteoric δD, δ 18O, and 36Cl/Cl signatures. The rest of the basin is characterized by several subsets of formation waters which have undergone variable degrees of iodine enrichment through diagenesis as well as variable degrees of dilution. The first subgroup is found in coals of relatively low vitrinite reflectance and moderate enrichment of iodine. This subgroup predominantly consists of entrapped pore fluids, although it may also contain waters which infiltrated the coals at the time of the Laramide uplift, between 25 and 30 Ma. A second subgroup consists of formation waters associated with coals of high vitrinite reflectance. Despite subsequent uplift, the high iodine concentrations and low 129I/I ratios of this subgroup, as well as a moderate depletion of deuterium relative to 18O, suggest that these waters were not significantly altered since the time when diagenetic reactions occurred in the deepest portion of the basin. A third subgroup, with higher δD and δ 18O values as well as higher 129I/I ratios, extends roughly west to east at the New Mexico–Colorado state line and corresponds to a region of extensive fracturing of the coalbeds. In this case, the higher 129I/I ratios are probably due to contributions of fissiogenic 129I through fracture flow, perhaps from deeper formation waters. Our results do not support models of subsequent basin-wide groundwater migration in the Fruitland Formation. The combined use of 129I and 36Cl with stable isotope studies provides valuable information as to the hydrologic history of coalbed methane deposits, as well as their potential for commercial exploitation.