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Integrated Sr isotope variations and global environmental changes through the Late Permian to early Late Triassic

Integrated Sr isotope variations and global environmental changes through the Late Permian to early Late Triassic

Song, H, Wignall, PB, Tong, J et al. (10 more authors) (2015) Integrated Sr isotope variations and global environmental changes through the Late Permian to early Late Triassic. Earth and Planetary Science Letters, 424. 140 - 147. ISSN 0012-821X https://doi.org/10.1016/j.epsl.2015.05.035

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Trace element geochemistry and Nd-Sr isotope systematics of Scheelite from the Thunder Creek and 144 Gap deposits, Timmins, Ontario: implications for timing and genesis of gold

Trace element geochemistry and Nd-Sr isotope systematics of Scheelite from the Thunder Creek and 144 Gap deposits, Timmins, Ontario: implications for timing and genesis of gold

Figure 3-5 Cut-core and grab-samples from the Thunder Creek Deposit……………………….71 Figure 3-6 Select core and grab samples from the Thunder Creek deposit………………..…....74 Figure 3-7 Back-scattered electron (BSE) image of a corroded Pyrite (Py) (the matrix in this image) grain containing ankerite (Ank), galena (Gn) and scheelite (Sch)...…………………….76 Figure 3-8 Sr WDS map and Mg and Fe EDS maps of TC-10 scheelite……………………….77 Figure 3-9 Sr WDS and W, Au and Mg EDS maps of TC-24……………………...…………..78 Figure 3-10 Chondrite normalized REE graph of scheelite grains from Thunder Creek and 144 Gap deposits (chondrite values from Sun and McDonough 1989)………….…………………...81 Figure 3-11 Trace element and REE concentrations across TC-08……………………………..81 Figure 3-12 147 Sm- 143 Nd isochron of all measured scheelite values. TC-10 and its duplicate, TC- 2 subsamples are marked separately. The isochron age for all whole-grain scheelite and sub- sampled values is 2587 ± 49 Ma. The isochron age for the TC-2 subsamples of one individual scheelite is 2516 ± 88 Ma………………………………………………………………………..84 Figure 3-13 εNdi vs. εSri for all scheelite measurements, including whole-grain scheelite, sub- samples of TC-2 and HWY-1 and TC-10 and its duplicate……………...………………………86 Figure 3-14 143 Nd/ 144 Nd vs. 1/Nd (ppm) for all scheelites, subsamples and two whole-rock syenite samples………………………………………………………………………………..…86 Figure 3-15 LA-ICPMS results of scheelite from the Thunder Creek and 144 Gap deposits compared to LA-ICPMS results of an Andradite Garnet from the Timmins West Mine………..90 Figure 3-16 Gold mines and their suspected ages based on 40Ar-39Ar dating of hydrothermal micas (Masliwec et al. 1985, Hanes et al. 1992), 147Sm-143Nd of scheelite (Bell et al. 1989, Anglin et al. 1996, this study), U-Pb of rutile (Jemielita et al. 1990, Wong et al. 1991) and U-Pb zircon (Claoué-Long et al. 1990, Kerrich and King 1993)……………………………………... 94 Figure 3-17 Scheelite grains from Thunder Creek and 144 Gap that demonstrate primary

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The strontium isotope distribution in water and fish within major South African catchments

The strontium isotope distribution in water and fish within major South African catchments

Strontium isotope ratios have successfully been used to link elephant bone and ivory to the environment in which these animals lived (Van der Merwe et al., 1990; Vogel et al., 1990). A similar study linked Sr ratio distribution in modern rodents to geology (Hoppe et al., 1999), while Beard and Clark (2000) showed that the Sr isotope composition of skeletal material can indicate the birthplace and geographic mobility of humans and animals. Lakes are very special habitats as fish migration and move- ments are limited by dam walls and usually very shallow waters at the inlets. Adult fish are therefore expected to spend their entire lives within a relatively limited area. Penne and Pierce (2006), in a telemetry study of carp in Clear Lake, Iowa, USA, found that carp congregated in a relatively small area in winter, then moved to specific spawning areas in spring and spread out somewhat during the summer and autumn months. Otis and Weber (1982) showed similar results in a carp telemetry study of the Lake Winnebago system, USA, and indicated that carp in a river system occupy restricted home ranges.

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Strontium isotope stratigraphy: LOWESS version 3: best fit to the marine Sr-isotope curve for 0-509 Ma and accompanying look-up table for deriving numerical age

Strontium isotope stratigraphy: LOWESS version 3: best fit to the marine Sr-isotope curve for 0-509 Ma and accompanying look-up table for deriving numerical age

and the eruptions of major (mostly) continental flood basalts (CFBs) at 17, 65, 92, 110?, 125, 184?, 200?, 250, and 258 Ma (Courtillot et al. 1996, 1999; fig. 9), although some inflections in the curve do not coincide with eruptions of CFBs (e.g., at 40, 45, 53, 100?, 160, and 177 Ma) and several episodes of such volcanism (30, 60, and 132 Ma) do not coin- cide with inflections in the curve. In view of the uncertainty of putting numerical ages on both Sr isotope data and flood basalt eruption (to say noth- ing of estimating the duration of eruptive flow), such conclusions are necessarily tentative. When better numerical ages can be established for some parts of the Sr isotope curve and for some episodes of flood basalt emplacement, events that fail to co- incide may do so (and events that coincide now may no longer do so). Two such age revisions de- serve mention: if the Triassic-Jurassic boundary, placed at 205.7 Ma in the time scale we use (Grad- stein et al. 1995), is reduced to about 200 Ma, as seems warranted by new age constraints on the boundary (Pa´lfy et al. 1998), then the inflection at

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Sr, Nd, and Pb isotope evidence for a mantle origin of alkali chlorides and carbonates in the Udachnaya kimberlite, Siberia

Sr, Nd, and Pb isotope evidence for a mantle origin of alkali chlorides and carbonates in the Udachnaya kimberlite, Siberia

dilution, (iii) Pb isotope composition, and (iv) Sm-Nd and Rb-Sr isotopes. The water leachates (L1) were analysed for trace elements and Rb-Sr isotopes; U-Pb and Sm-Nd isotope data were obtained on a separate water leach for sample YBK-0 (“L1*”) after trace element data for L1 indicated Pb-Nd levels sufficient for isotopic work. The ca. 12 x 5 mm salt segregation found in YBK-3 (Fig.2) was dissolved in cold water and, following determination of approximate trace element contents on a small test aliquot, was split for separate determination of (i) U-Pb isotope dilution, (ii) Pb isotopic composition, (iii) Rb-Sr isotope dilution, and (iv) Sr isotopic composition. Chemical and isotopic analyses: Major and trace element compositions of three groundmass samples, including YBK-0 and YBK-3, and trace elements in L1, L2 and res fractions, were determined at the University of Tasmania, by fused disc XRF and solution-mode ICP-MS, respectively (Yu et al., 2001). Major cation and anion contents in water leachates were measured by Analytical Services Tasmania, using ICP-AES for cations, and ion chromatography with electronic suppression and conductivity detection (Dionex DX100) for anions. Carbon was determined using a Carlo Erba CHNS-O elemental analyzer at the University of Tasmania. Selected trace and major element data were plotted on a standard multi-element diagram after normalization to primitive mantle values of Sun and McDonough, 1989.

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Quantifying episodic erosion and transient storage on the western margin of the Tibetan Plateau, upper Indus River

Quantifying episodic erosion and transient storage on the western margin of the Tibetan Plateau, upper Indus River

forces in determining erosion patterns and rates, and in turn orogenic architecture, is unresolved. The monsoon-dominated frontal Himalaya is a classic example of how surface processes may drive focused denudation and potentially control structural evolution. We investigate whether there is a clear relationship between climate and erosion in the drier Himalayan rain shadow of northwest India where a coupled climate-erosion relationship is less clear. We present a new integrated dataset combining bulk petrography, geomorphometric analysis, detrital U-Pb zircon geochronology, and bulk Nd and Sr isotope geochemistry from modern river sediments that provides constraints on spatial patterns of sediment production and transport in the Zanskar River. Zanskar River sands are dominated by Greater Himalayan detritus sourced from the glaciated Stod River catchment that represents only 13% of the total basin area. Prevalent zircon peaks from the Cambro-Ordovician (440–500 Ma) and Mississippian-Permian (245–380 Ma) indicate more abundant pre-Himalayan granitoids in the northwest Himalaya than in the central and eastern Himalaya. Erosion from the widely-exposed Tethyan Himalaya, however, appears modest. Spatial patterns of erosion do not correlate with highest channel steepness. Our data demonstrate that Zanskar differs from the monsoon-soaked frontal Himalaya and the arid, extremely slow-eroding orogenic interior in that focused erosion and sediment production are driven by glaciers. Subsequent remobilization of glacially-derived sediments is likely controlled by monsoonal rainfall and we suggest sediment reworking plays an important role. These data support strong climatic control on modern orogenic erosion on the periphery of the Himalayan rain shadow.

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South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea

South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea

The Sr isotope composition of detrital sediments is predominantly controlled by grain-size sorting during transport, changes in the source region, and the intensity of chemical weathering on land [Meyer et al., 2011; T€ utken et al., 2002]. We have separated the clay-size fraction (<2 mm) to minimize the effect of sedi- ment sorting during transport, acknowledging that some sorting of the fine fraction has most likely already occurred in the catchment of the river and during riverine transport. The Nd and Pb isotope compositions indicate essentially constant source areas over the past 60 kyr suggesting little influence of source region changes on the studied sediment composition during this period. Therefore, the Sr isotope compositions of the carbonate and organic matter free clay fraction indicate changes of the incongruent weathering of the silicate rocks in the source region [Taylor and Blum, 1995]. Colin et al. [2006] demonstrated the variation of Sr isotope compositions in Andaman Sea sediments is independent of the source of the sediments, the dis- tance from the source river mouth, and grain-size sorting effects. These authors further suggested that an increase in 87 Sr/ 86 Sr ratios corresponded to the intensification of physical erosion in the Irrawaddy River catchment caused by enhanced release of unaltered minerals such as mica with high 87 Sr/ 86 Sr ratios. The Sr isotopic composition of the clay-size fraction from Site 17 is lower than that of the bulk sediments in the Andaman Sea [Colin et al., 2006]. This deviation is most likely simply caused by minor contributions from less radiogenic sources (e.g., Barren Island, Table 1). The trend displayed by the Sr isotope composition of clays and the bulk sediments is similar between the Holocene and glacial periods with glacial sediments characterized by higher 87 Sr/ 86 Sr ratios than Holocene sediments.

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Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O

Crystal structures of Sr(ClO4)2·3H2O, Sr(ClO4)2·4H2O and Sr(ClO4)2·9H2O

The structure of the nonahydrate contains one Sr 2+ cation coordinated by seven water molecules and by two O atoms of two perchlorate tetrahedra (point group symmetry ..m), forming a tricapped trigonal prism (point group symmetry m2m). The structure contains additional non-coordinating water molecules, which are located on twofold rotation axes. O—H O hydrogen bonds between the water molecules as donor and ClO 4 tetrahedra and water molecules as acceptor groups

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The influence of oxygen isotope exchange between CO2 and H2O in natural CO2-rich spring waters : implications for geothermometry

The influence of oxygen isotope exchange between CO2 and H2O in natural CO2-rich spring waters : implications for geothermometry

2 -rich waters from around the world. Here we review the effects of oxygen isotope exchange with CO 2 , high temperature equilibration with bedrock minerals and mineral dissolution and precipitation reactions on the CO 2 -rich water isotopic composition. We present two case studies from Daylesford (Australia) and Pah Tempe (Utah, USA) mineral springs, where we use a numerical geochemical modelling approach to resolve the influence of low temperature water-rock interactions and CO 2 equilibration to the oxygen isotope ranges observed in the mineral waters. In both cases, we fi nd that mineral dissolution e precipitation reactions are unlikely to have a significant effect on the groundwater isotopic compositions, and that the observed d 18 O values in natural CO 2 springs can be simply explained by equilibrium fractionation between water and free phase CO 2 . Traditionally, the interaction of CO 2 and water in a natural CO 2 -rich groundwater setting has only been associated with water 18 O depletion and this is the first study to consider 18 O enrichment. We establish that in a natural setting, CO 2 and water equilibration can result in water 18 O depletion or enrichment, and that the change in the oxygen isotope composition ultimately depends on the initial CO 2 and water d 18 O values. Our new conceptual model therefore provides a mechanism to explain water 18 O enrichment at ambient temperatures. This finding is critical for the use of d 18 O in groundwater geothermometry and for the interpretation of natural water circulation depths: we argue that in some cases, natural waters previously interpreted as geothermal based on their oxygen isotope composition may actually have acquired their isotopic signature through interaction with CO 2 at ambient temperatures.

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A global transition to ferruginous conditions in the early Neoproterozoic oceans

A global transition to ferruginous conditions in the early Neoproterozoic oceans

5. Yang, D.-B. et al. U–Pb ages and Hf isotope data from detrital zircons in the Neoproterozoic sandstones of northern Jiangsu and southern Liaoning Provinces, China: Implications for the Late Precambrian evolution of the southeastern North China Craton. Precambrian Research 216–219, 162–176 (2012).

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A method for stable carbon isotope ratio and concentration measurements of ambient aromatic hydrocarbons

A method for stable carbon isotope ratio and concentration measurements of ambient aromatic hydrocarbons

Bias in the GC-IRMS analysis can be caused by contami- nation or losses during adsorption or desorption of VOCs in the TSPS, problems in the chromatographic separation such as peak tailing or baseline drift and incomplete oxidation in the combustion interface. A significant impact from contam- ination or artifacts can be ruled out since this would result in a decrease of bias for high sample masses, which is not found (Fig. 3). Although in principle none of the other explanations can be ruled out, there is no direct evidence which would support them. The good reproducibility of the measured n- alkane carbon isotope ratios would require that any loss in the TSPS would be highly reproducible, which is unlikely, and the tests of the TSPS showed no indication for significant loss of n-alkanes in the TSPS. Except for n-pentane there also is no indication of problems due to chromatographic separa- tion, peak shape or baseline drift for n-alkanes. Due to the higher chemical stability of n-alkanes, incomplete oxidation in the combustion interface could result in isotope fractiona- tion for n-alkanes without influencing the results for aromatic VOCs, although this would require inverse isotope effects for the catalytic oxidation of n-alkanes in order to explain the bias towards higher carbon isotope ratios.

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Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes

Precipitation of dolomite from seawater on a Carnian coastal plain (Dolomites, northern Italy): evidence from carbonate petrography and Sr isotopes

In contrast, penecontemporaneous dolomite formation seems to have prevailed in the Tethyan realm during the Tri- assic (Meister et al., 2013, and references therein; Li et al., 2018), in an “aragonite sea”, while elsewhere dolomite was not particularly abundant (see Given and Wilkinson, 1987). In Norian shallow water dolomites of the Dolomia Princi- pale, Iannace and Frisia (1994) measured oxygen isotope val- ues as positive as +3.5 ‰, suggesting formation at Earth sur- face temperatures, whereas dolomites from overlying Lower Jurassic units typically show oxygen isotope signatures of diagenetic overprint at burial temperature. Frisia (1994) in- terpreted these dolomites to be an early diagenetic replace- ment of precursor carbonate. In a recent study, Preto et al. (2015) suggested that the dolomites of the Carnian Trave- nanzes Formation (Fm.) in the Venetian Alps are primary precipitates; i.e. they precipitated directly from solution in the sedimentary environment and not by the replacement of a precursor phase during burial. This interpretation is based on high-resolution transmission electron microscope (HR-TEM) analysis, which revealed that single micron-scale dolomite crystals consist of grains with incoherent crystal- lographic orientation at a scale of a few nanometres (see Meister and Frisia, 2019). The nanocrystal structures were not replaced by any of the dolomite phases described by Frisia and Wenk (1993) in Late Triassic dolomites of the southern Alps; instead they are similar to dislocation-ridden Mg-rich phases observed in dolomite from modern sabkhas and are interpreted as primary in origin (Frisia and Wenk, 1993). This finding is intriguing, not only because it is con- sistent with primary dolomite formation proposed by Van Tuyl (1916) and observed in many modern environments (e.g. Sabkha of Abu Dhabi: Illing et al., 1965; Wenk et al., 1993; unlithified dolomite is also mentioned in Bontognali et al., 2010; and Court et al., 2017; Deep Springs Lake, Califor- nia: Jones, 1965; Clayton et al., 1968; Meister et al., 2011; Coorong lakes: Von der Borch, 1976; Rosen et al., 1989; Warren, 1990; Brejo do Espinho, Brazil; Sánchez-Román et al., 2009; Lake Acıgöl, Turkey: Balci et al., 2016; Neusiedler See, Austria: Neuhuber et al., 2015; Lake Van: McCormack et al., 2018), but also because it provides a window into an- cient primary dolomite formation pathways. This finding is also consistent with recent experiments by Rodriguez-Blanco et al. (2015), demonstrating a nanocrystalline pathway of dolomite nucleation and growth. Critically, nanometre-size nuclei show a different surface energy landscape compared

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SUPER-RESOLUTION BASED IMAGE IN PAINTING

SUPER-RESOLUTION BASED IMAGE IN PAINTING

be filled is large and another critical aspect is the high computational time in general required. These two problems are here addressed by considering a hierarchical approach in which a lower resolution of the input image is first computed and inpainted using a K-NN (K Nearest Neighbours) examplar-based method. Correspondences between the K-NN low- resolution and high-resolution patches are first learnt from the input image and stored in a dictionary. These correspondences are then used to find the missing pixels at the higher resolution following some principles used in single-image super-resolution methods. Super-Resolution (SR) refers to the process of creating one enhanced resolution image from one or multiple input low resolution images. The two corresponding problems are then referred to as single or multiple images SR, respectively. In both cases, the problem is of estimating high frequency details which are missing in the input image(s).

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Knockdown expression and hepatic deficiency reveal an atheroprotective role for SR BI in liver and peripheral tissues

Knockdown expression and hepatic deficiency reveal an atheroprotective role for SR BI in liver and peripheral tissues

Earlier studies in PDZ domain  containing 1–deficient (PDZK1- deficient)  mice  have  provided  insight into the impact of tissue- specific  ablation  of  the  SR-BI   isoform in the hepatocyte (95%)  and  small  intestine  (50%)  on  cholesterol  homeostasis  (28).  In order to evaluate the relative  contributions of hepatic versus  extrahepatic SR-BI expression to  cholesterol homeostasis and ath- erogenesis, we developed an SR-BI   conditional  knockout  mouse  model by Cre/loxP technology.  However, loxP targeting  of the  SR-BI gene resulted in reduced  SR-BI expression in all tissues,  generating a hypomorphic SR-BI  mouse line in which SR-BI can be  specifically deleted by Cre/loxP  recombination. Our data reveal  that  while  atherosclerosis  was  enhanced in mice with reduced  expression of SR-BI (hypomSR-BI   mice),  aortic  lesion  formation  was dramatically accelerated in  mice with Cre-mediated deletion  of hepatic SR-BI (hypomSR-BI–

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II. SR RESEARCH ISSUES

II. SR RESEARCH ISSUES

Some of the research activities in this field deal with formal methods in secure system engineering. Formal description of security protocols [4] and presenting a semi-formal method for validation of SR [16] are among these activities. Yet, improving in this field requires a lot of research efforts .On the other hand, these kinds of methods can be implemented only by security experts because security policies are usually determined by special security models that are not yet integrated into software engineering models [3]. Apart from these problems, from software engineering point of view, ideal software omits manual intervention and involves only formal methods in each phase of software development (including security analysis and modeling). Hence, integrating security within software development, especially in requirement analysis as the basis of software

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A SURVEY ON QUALITY FACE EXTRACTION FROM VIDEO

A SURVEY ON QUALITY FACE EXTRACTION FROM VIDEO

need human operators to identify suspected people. Therefore, having an automated system working with LR and low-quality face images is desirable. However, low-quality images do not have enough high-resolution (HR) details for facial analysis systems and using them directly in these systems is not reliable. Thus, there is a need for a mechanism for bridging this gap between LR images and facial analysis systems. Super-resolution (SR) is one of such mechanisms for obtaining an HR image from one or more LR input images. SR algorithms are broadly classified into two classes: reconstruction- based SR (RBSR) and learning-based SR (LBSR).

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Influence of Sr and Mn Additions on Intermetallic Compound Morphologies in Al Si Cu Fe Cast Alloys

Influence of Sr and Mn Additions on Intermetallic Compound Morphologies in Al Si Cu Fe Cast Alloys

Other factors which possibly influence the nucleation behavior are the nucleation sites and the undercooling for the formation of the and eutectic phases during solidification. Crosley and Mondolfo 5) found that in Al-Si alloys aluminum phosphide (AlP), which forms due to the presence of P in the melt as an impurity, acts as an effective nucleation site for the Si phase and presence of AlP coarsens the eutectic Si. AlP is also reported to have an important role in the nucleation of the undesirable iron-bearing phases in the 413 aluminum alloy by Sigworth. 6) Crosley and Mondolfo also found that the modifier element (Na or Sr) suppresses the formation of AlP, resulting in the decreased number of the nucleation sites

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Sr-Nd Isotope Constraints of Hezar Igneous Complex (south of ‎Kerman- Iran) - as a Part of Urumieh-Dokhtar Magmatic Arc

Sr-Nd Isotope Constraints of Hezar Igneous Complex (south of ‎Kerman- Iran) - as a Part of Urumieh-Dokhtar Magmatic Arc

The Hezar Igneous Complex (HIC) in the south-eastern part of Urumieh-Dokhtar magmatic arc, is the most prominent magmatic feature in the Kerman Porphyry Copper Belt, near Rayen, south of Kerman. It is indicated that the possible place of the vent is in Jalas Mountain which has been split later by the Sabzevaran fault into Minor and Major Jalas. The sub-alkaline rocks of this complex are mainly composed of different pyroclastic and lava flow rocks, acidic to basic in composition. Positive Epsilon Nd values and low Sr in HIC, besides TDM 0.6-0.7 Ga indicates formation from partial melting of lithospheric mantle sources which is modified with previous subduction components. Positive epsilon Nd indicates that these rocks have been originated from evolved magmas without assimilation of crustal materials. All of the samples except two cases are far from mantle array which indicates that they are located in mantle wedge over the subduction zone and subjected to some increasing in 87 Sr/ 86 Sr ratios. The depicted isochron for three related samples indicates an age of 47±5 Ma with MSWD=0.44 which is an

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Coupled measurements of δ18O and δD of hydration water and salinity of fluid inclusions in gypsum from the Messinian Yesares Member, Sorbas Basin (SE Spain)

Coupled measurements of δ18O and δD of hydration water and salinity of fluid inclusions in gypsum from the Messinian Yesares Member, Sorbas Basin (SE Spain)

Gypsum samples were ground and dried in a 30 ◦ C oven for 24 h to remove absorbed water and fluid inclusions. Hydration wa- ter was extracted using a semi-automated extraction system – the WASP (Water Analyser Sample Preparation) Device developed at the University of Cambridge (Gázquez et al., accepted) (see SI for details). Water oxygen and hydrogen isotopes were measured si- multaneously by cavity ringdown laser spectroscopy (CRDS) using a Picarro L1102-i water isotope analyzer and A0211 high-precision vaporizer at the University of Cambridge. Each sample was injected nine times into the vaporizer. Memory effects from previous sam- ples were avoided by rejecting the first three analyses. Values for the final six injections were averaged with in-run precision of less than ± 0 . 1 for δ 18 O and ± 0 . 6 for δ D ( 1 σ ) . Calibration of results to V-SMOW was achieved by analyzing internal standards (JRW, ENR, BOTTY, SPIT) before and after each set of 7 or 8 samples. In- ternal standards were calibrated against V-SMOW, GISP, and SLAP. All results are reported in parts per thousand ( h ) relative to V- SMOW. External error, less than ± 0 . 1 h and ± 0 . 8 h for δ 18 O and δ D, respectively, was estimated by repeated analysis of an internal gypsum standard, New-Gyp (n = 5).

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Geochemistry of fine-grained sediments in the Yangtze River and the implications for provenance and chemical weathering in East Asia

Geochemistry of fine-grained sediments in the Yangtze River and the implications for provenance and chemical weathering in East Asia

et al. 2009), the isotope geochemistry data shows that the rocks exposed in the western Yangtze Craton, especially the Emeishan Basalts, are not the main sources of <63 μm sediment to the modern river. Not surprisingly, the river sediments have lower ɛNd values than the magmatic rocks from the Cathaysia Block, which mostly lies to the South within the Pearl River drainage and is not an important source. Moderate exposures of primitive magmatic rocks within the Yangtze Craton do not influence the bulk com- position of the river to a significant degree. Our sediment samples have a relatively restricted range of ɛNd values but a wide range in 87 Sr/ 86 Sr values, which we consider to reflect the influence of chemical weathering in changing the original bedrock composition. We particularly note that the Ganjiang and Yuanjiang have very high 87 Sr/ 86 Sr values and are located in the middle-lower reaches of the river where chemical weathering might be strong as a re- sult of slow erosion and transport rates in relatively flat topography and because of the warm and wet monsoonal climate, as indicated by their high CIA values.

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