Oxygen isotopic composition of the Luna 20 soil

The Luna 20 soil (< 125 μm fraction) has a relatively low δO¹⁸ (5.7%.), compared to other lunar soils (5.8 to 6.3%.). This implies either a low-O¹⁸ source material or an unusually small O¹⁸ enrichment in the processes of soil formation and maturation.     

Oxygen isotopic composition of minerals in the Kenna ureilite

The δ¹⁸O and δ¹⁷O values of olivine from Kenna are 7.6 and 3.0%, respectively, relative to SMOW. These values are typical of ureilites which form a unique group on a δ¹⁷O -δ¹⁸O graph. The ureilites are related to, but not directly derived from, the anhydrous phases of C2 and C3 meteorites. The ¹⁸O/¹⁶O fractionation between pyroxene and olivine is 0.60, indicating a temperature of last equilibration of 1000 ± 100°C.     

Oxygen and carbon isotopic systematics of aragonite speleothems and water in Furong Cave, Chongqing, China

To understand oxygen and carbon stable isotopic characteristics of aragonite stalagmites and evaluate their applicability to paleoclimate, the isotopic compositions of active and fossil aragonite speleothems and water samples from an in situ multi-year (October 2005-July 2010) monitoring program in Furong Cave located in Chongqing of China have been examined. The observations during October 2005-June 2007 show that the meteoric water is well mixed in the overlying 300-500-m bedrock aquifer, reflected by relatively constant δ¹⁸O, ±0.11-0.14‰ (1σ), of drip waters in the cave, which represents the annual status of rainfall water. Active cave aragonite speleothems are at oxygen isotopic equilibrium with drip water and their δ¹⁸O values capture the surface-water oxygen isotopic signal. Aragonite-to-calcite transformation since the last glaciation is not noticeable in Furong stalagmites. Our multi-year field experiment approves that aragonite stalagmite δ¹⁸O records in this cave are suitable for paleoclimate reconstruction. With high U, 0.5-7.2 ppm, and low Th, 20-1270 ppt, the Furong aragonite stalagmites provide very precise chronology (as good as ±20s yrs (2σ)) of the climatic variations since the last deglaciation. The synchroneity of Chinese stalagmite δ¹⁸O records at the transition into the Bølling-Allerød (t-BA) and the Younger Dryas from Furong, Hulu and Dongge Caves supports the fidelity of the reconstructed East Asian monsoon evolution. However, the Furong record shows that the cold Older Dryas (OD) occurred at 14.0 thousand years ago, agreeing with Greenland ice core δ¹⁸O records but ∼200 yrs younger than that in the Hulu record. The OD age discrepancy between Chinese caves can be attributable to different regionally climatic/environmental conditions or chronological uncertainty of stalagmite proxy records, which is limited by changes in growth rate and subsampling intervals in absolute dating. Seasonal dissolved inorganic carbon δ¹³C variations of 2-3‰ in the drip water and 5-7‰ in the pool and spring waters are likely attributed to variable degrees of CO₂ degassing in winter and summer. The variable δ¹³C values of active deposits from −11‰ to 0‰ could be caused by kinetically mediated CO₂ degassing processes. The complicated nature of pre-deposition kinetic isotopic fractionation processes for carbon isotopes in speleothems at Furong Cave require further study before they can be interpreted in a paleoclimatic or paleoenvironmental context.     

Oxygen isotopic signature of the skeletal microstructures in cultured corals: Identification of vital effects

In order to identify vital effect on oxygen isotopic ratio, we analyzed at micrometer size scale skeleton microstructures of a scleractinian coral Acropora, cultured under constant conditions. Measurements focused on the two crystalline units highlighted different isotopic signatures. Massive crystals (centers of calcification: COC) exhibit quasi-constant lowest values whereas fibers, the dominant units exhibit scattered distribution with amplitude of up to 5‰. Fiber oxygen isotopic ratios (δ¹⁸O) range from values similar to instantaneous deposition to equilibrium value. By comparing data obtained on the Acropora specimen and deep-sea corals grown under well constrained conditions, we infer that the scattered δ¹⁸O aragonite fibers indicate precipitation through kinetic precipitation. Thus, we argue for inherent biological feature typical to all coral genera. Modalities of COC formation remain ignored.The different isotopic signature of two mineral microstructures present in close proximity in coral skeleton can only be explained by compartment depositions related to different organic environments. Indeed, multiple secondary electron microscopy (SEM) observations favor interaction between mineral and organic matrix surface. Moreover, atomic forcing microscopy (AFM) investigations demonstrated thermodynamic changes induced by mineralization in presence of organic compounds. The combination of our results with previous published ones from biological studies, allows us proposing a consistent model of fiber skeleton formation. The prerequisite step of mineral growth unit precipitation would be initiated by organic matrix secretion, which defines spatial extension. Specific carriers supply ionic compounds of the crystals to ensure local supersaturation. However, possibly controlled by organic molecules, ionic amount would be limited, implying the supersaturation decline over the time. This could explain the progressive decrease of the coral growth rate. In this case, vital effect should not only bias isotopic fractionation through biological activity but the mechanism of skeleton deposition is imposed by specific chemical and/or physical conditions due to the presence of organic molecules. These conclusions derive from observations performed at high resolution.Therefore, isotopic ratio measured on millimeter scale for paleoclimatic purposes, result of the average of strongly heterogeneous values. It could explain vital effects shown by geochemical time series derived from tropical coral skeleton, including the high species and/or colony variability.     

Electron spin resonance dating of burned flint from Kebara Cave,Israel

Electron spin resonance (ESR) measurements of heated flint from Kebara cave show the presence of two radiation sensitive signals: E' and Al. Both are strongly interfered with by organic signals produced during heating of the flint. The signal subtraction method of Porat and Schwarcz (1991) was used to determine equivalent doses for flint samples from levels VII-XII, for which thermoluminescence (TL) ages on the same samples are known. Ages were determined using dose rates based on analyses of the flint and TLD measurements of external dose rates. The average E' age of 48.5 ± 5.1 ka is much less than the average TL age (62.2 ± 4.3 ka), whereas the average age of 64.6 ± 12 ka given by the Al signal is in good agreement with the TL age, but with much larger dispersion. © 1994 John Wiley & Sons, Inc.     

辽西下白垩统义县组烃类化合物氢同位素组成及古气候环境意义

以四合屯剖面下白垩统义县组三段湖相沉积为研究对象,对抽提物中正构烷烃和无环类异戊二烯烃的氢同位素组成进行了测定,以期为热河生物群繁盛时期的古气候和古环境变化提供氢同位素组成的证据。结果显示,正构烷烃的氢同位素组成介于-232.1‰~-93.6‰,在剖面上变化明显;主峰碳数正构烷烃氢同位素组成的相关性分析显示,n-C29与n-C31主要来自陆生高等植物,而n-C23则主要来自水生植物。中碳数正构烷烃与高碳数正构烷烃氢同位素组成差值(ΔδDmid-long)的剖面变化在-28.8‰~85.0‰,指示热河生物群繁盛时期的气候波动显著,呈现由干旱逐渐变为温湿,再回归干旱的阶段性循环特征。特别是姥鲛烷和植烷的氢同位素组成较正构烷烃明显偏轻,而姥鲛烷较植烷的氢同位素组成相对轻微偏重,结合它们的碳同位素组成证据,这一差异很可能是由于成岩演化过程中植醇形成姥鲛烷和植烷的途径不同而引起。     

Oxygen isotopic composition of quartz veins and host rocks at the Sukhoi Log deposit,Russia

The relationships between the δ¹⁸O of quartz veins and veinlets pertaining to the main stage of gold mineralization at the Sukhoi Log deposit and metasomatically altered host slates are estimated. The oxygen isotopic composition of veined quartz and host slates is not uniform. The δ¹⁸O of quartz veins from the Western, Central, and Sukhoi Log areas of the deposit vary from +16 to + 18 ‰. The δ¹⁸O range of metasomatically altered slates in the Western and Sukhoi Log areas attains 6 ‰. The δ¹⁸O of quartz veins are always higher than those of host slates by 3–7‰. The regular difference in the δ¹⁸O between quartz veins and host slates indicates that the oxygen isotopic composition of the ore-bearing fluid forming the system of quartz veins and veinlets at the Sukhoi Log deposit could have formed as a result of interaction with silicate rocks, for instance, terrigenous slates enriched in δ¹⁸O. Such interaction, however, took place at deeper levels of the Sukhoi Log deposit. It is suggested that the fluid phase participating in the formation of the vein and veinlet system had initially high δ¹⁸O(>+10‰) due to interaction with the rocks enriched in δ¹⁸O at a low fluid/rock ratio. The oxygen isotope data indicate that the fluid participating in the formation of gold mineralization at the Sukhoi Log deposit was not in equilibrium with igneous rocks at high temperatures.     

罗平生物群产出层位氧碳稳定同位素的初步研究

为了解云南罗平地区新近发现的罗平生物群的古环境信息,我们对其产出层位－－中三叠统关岭组二段大凹子剖面的碳酸盐岩进行了全岩氧碳稳定同位素测试。测试结果显示,中三叠世安尼期Pelsonian亚期大凹子剖面δ13C值分布范围在-4.543‰～1.069‰之间,平均为-3.0298‰,δ18O值分布在-5.202～-0.971‰之间,平均为-3.3645‰。 同位素数据的相关性分析显示大凹子剖面的同位素值受后期大气水参与的成岩作用影响较小。结合沉积学和古生物学的证据,我们提出了一个假说：δ13C值明显偏负的层位主要是由硫酸菌的还原作用所导致。这种活动所释放的H2S也部分解释了罗平生物群大规模死亡的原因。 在排除掉成岩作用的影响之后,本剖面δ13C分布在-2.976～1.069‰之间,平均值为-1.4556‰,δ18O分布在-3.455～-2.516‰之间,平均值为-2.9258‰。尽管如此,与同时期其它有关剖面相比,大凹子剖面δ13C值仍然偏低,对此我们进行了探讨和解释,并利用高水位时期的δ18O数据作为基本资料对罗平地区的古海水温度进行了恢复。结果显示其温度值分布在27℃～32℃之间,平均为29℃左右,说明罗平地区当时气候比较温暖。     

Oxygen and hydrogen isotopic composition of Alpine and pre-Alpine minerals of the Swiss Central Alps

The rocks of the Swiss Central Alps consist of pre-Mesozoic and Mesozoic rocks which were metamorphosed during the Alpine orogeny. Eightysix samples from this area have been analyzed for their isotopic composition (310 mineral phases for their ¹⁸O values and 99 mineral phases for their D values).The mineral phases of pre-Mesozoic and Mesozoic rocks differ significantly in their stable isotope composition. The minerals in pre-Mesozoic rocks display a rather uniform oxygen and hydrogen isotope composition indicative of large-scale homogenization with magmatic fluids. The mineral phases of Mesozoic rocks, on the other hand, show a large variation in their isotopic composition, their ¹⁸O values are heavier, and their D values are isotopically lighter than the pre-Mesozoic phases. These data indicate the lack of a large-scale water supply to the gneissic cores of the Penninic nappes during Alpine metamorphism.Equilibrium conditions, as indicated by concordant oxygen isotope temperatures, are attained in several samples; disequilibrium, however, is more frequently observed, mainly in the central part of the Lepontin area. The pre-Mesozoic rocks recrystallized during Alpine metamorphism. This process was accompanied by partial reequilibration of the oxygen isotopes, and took place in a closed system. In the pre-Mesozoic rocks, the oxygen isotope fractionations, therefore, reflect the temperatures at the time of this recrystallization which, in many cases, is not the maximum temperature of Alpine metamorphism. There is strong evidence that oxygen isotope ratios are frozen during the progressive phase of a metamorphic event.Oxygen isotope fractionations indicate temperatures of Alpine metamorphism ranging from 500 ° C near Andermatt to 700 ° C near the Bergell granite.     

利用哺乳动物化石牙齿氧同位素计算年平均温度初探

利用哺乳动物骨骼或牙齿釉质中的磷酸盐的氧稳定同位素来定量研究陆地古气候,作为一种新的方法,最近越来越得到重视。只要哺乳动物骨骼或牙齿化石的δ18Opo4能代表这些动物生活时期的原始数值,我们就可以利用现生哺乳动物的经验方程来计算地质历史时期的年平均温度。研究表明,骨骼的高孔隙度使化石受到成岩作用的严重影响,而牙齿釉质由于有机质含量少、密度高、晶体尺寸大等原因,能够有效地抵抗成岩作用而保存原始的氧同位素信号[1]。所以利用化石釉质磷酸盐测定氧同位素并进一步计算古年平均温度的方法是相当可靠的。Luz等证明了现代北美鹿类动物骨骼磷酸盐的氧同位素(δ18Opo4)与年平均温度之间呈正相关关     

Oxygen isotopic composition of chondritic interplanetary dust particles: A genetic link between carbonaceous chondrites and comets

Oxygen isotopes were measured in four chondritic hydrated interplanetary dust particles (IDPs) and five chondritic anhydrous IDPs including two GEMS-rich particles (Glass embedded with metal and sulfides) by a combination of high precision and high lateral resolution ion microprobe techniques.All IDPs have isotopic compositions tightly clustered around that of solar system planetary materials. Hydrated IDPs have mass-fractionated oxygen isotopic compositions similar to those of CI and CM carbonaceous chondrites, consistent with hydration of initially anhydrous protosolar dust. Anhydrous IDPs have small ¹⁶O excesses and depletions similar to those of carbonaceous chondrites, the largest ¹⁶O variations being hosted by the two GEMS-rich IDPs. Coarse-grained forsteritic olivine and enstatite in anhydrous IDPs are isotopically similar to their counterparts in comet Wild 2 and in chondrules suggesting a high temperature inner solar system origin. The small variations in the ¹⁶O content of GEMS-rich IDPs suggest that most GEMS either do not preserve a record of interstellar processes or the initial interstellar dust is not ¹⁶O-rich as expected by self-shielding models, although a larger dataset is required to verify these conclusions.Together with other chemical and mineralogical indicators, O isotopes show that the parent-bodies of carbonaceous chondrites, of chondritic IDPs, of most Antarctic micrometeorites, and comet Wild 2 belong to a single family of objects of carbonaceous chondrite chemical affinity as distinct from ordinary, enstatite, K- and R-chondrites. Comparison with astronomical observations thus suggests a chemical continuum of objects including main belt and outer solar system asteroids such as C-type, P-type and D-type asteroids, Trojans and Centaurs as well as short-period comets and other Kuiper Belt Objects.     

Stable isotopic investigations of early development in extant and fossil chambered cephalopods I. Oxygen isotopic composition of eggwater and carbon isotopic composition of siphuncle organic matter in Nautilus

Eggwaters from the chambered cephalopod Nautilus are depleted in both ¹⁸O and deuterium relative to ambient seawater. Eggwaters from six other species, including the related chambered cephalopod Sepia, do not show such depletion. These observations indicate that the previously observed step towards more positive $\text{δ}{}^{18}\text{O}$ values in calcium carbonate laid down after Nautilus hatches, relative to carbonate precipitated prior to hatching, can be explained by equilibration of the carbonate with water in the egg before hatching and with seawater after hatching. The presence of an oxygen isotope difference between eggwater and seawater for Nautilus and its absence for Sepia suggest that hatching will be recorded in the $\text{δ}{}^{18}\text{O}$ values of shell carbonates for some but not all extinct and extant chambered cephalopods.The $\text{δ}{}^{13}\text{C}$ values of the organic fraction of the siphuncle in Nautilus do not show any consistent pattern with regard to the time of formation before or after hatching. This observation suggests that the minimum in $\text{δ}{}^{13}\text{C}$ values previously observed for calcium carbonate precipitated after Nautilus hatches is not caused by a change in food sources once the animal becomes free-swimming, as has been suggested.     

Formation processes of cemented features in karstic cave sites revealed using stable oxygen and carbon isotopic analyses: A case study at middle paleolithic Amud Cave,Israel

Hearths are important archaeological features, serving to infer past practices related to hominin subsistence and social behaviors. The identification of hearths is not always straightforward due to post‐depositional processes. In karstic cave environments in particular it is not always easy to distinguish, in the field or in the laboratory, between geogenic and anthropogenic cemented features because both are composed of calcite. Here we present a novel study in which bulk oxygen and carbon isotopic analyses were used in order to unequivocally identify anthropogenic calcite derived from hearths in the Neanderthal site of Amud Cave (Israel). We demonstrate that the isotopic composition of wood ash is distinctively different from that of geogenic calcite. The linear relationship observed between carbon and oxygen isotopic compositions of the various sediment types in Amud Cave is interpreted as a mixing line between wood ash and geogenic calcite, thus enhancing our understanding of the origins of sedimentological variability at the site and showing that not all of the cemented sediments in Amud Cave should be regarded as hearths. Our study suggests that the relative abundance of validated hearths in the various areas of the cave may be associated with Neanderthal use of space in Amud Cave. © 2008 Wiley Periodicals, Inc.     

Boron isotopic composition of fumarolic condensates and sassolites from Satsuma Iwo-jima,Japan

¹¹B/¹⁰B ratios of the high temperature fumarolic gases (>465°C) of this island were found to be constant within the limits of experimental error (¹¹B/¹⁰B = 4.066). This value may represent the ¹¹B/¹⁰B ratio of boron in the andesite magma. ¹¹B/¹⁰B ratios of the low temperature fumarolic gases (<235°C) were found to vary from 4.053 to 4.077. ¹¹B/¹⁰B ratios of some sassolites were approximately equal to that of the fumarolic condensates and the other ones were slightly enriched in ¹⁰B compared to the fumarolic condensates.