水对Wadsleyite和Ringwoodite电导率的影响及地球动力学意义

在Kawai-1000型多顶砧压机上，利用橄榄石相变人工合成地幔转换带矿物wadsleyite和ringwoodite，其含水量从0．03wt％到2．0wt％变化不等。在压力14～16GPa，温度873K-1273K，通过Mo：MoO2固体反应控制氧逸度的条件下，利用阻抗谱分析方法，测量获得了这些样品的电导率。实验结果显示：wadsleyite的电导率与GH^0.66呈正比，ringwoodite的电导率与GH^0.69呈正比，水极大地增强了样品的电导率；在我们的实验条件下，含水wadsleyite和ringwoodite样品的主要电荷栽体是自由质子。另外，结合大地电磁反演获得的电导率结果和我们的实验数据，我们推断中国东北地区地幔转换带中的水含量约为0．1～0．3wt％，远远高于上地幔中的水含量，这或许表明在410km处可能发生了部分熔融。     

新疆西天山哈勒尕提铁铜矿床流体包裹体和氢氧同位素特征及其成矿意义

哈勒尕提铁铜矿床位于新疆西天山博罗科努多金属成矿带,矿体呈似层状、透镜状产于晚泥盆世中酸性侵入体与上奥陶统碳酸盐岩接触带上,是一个典型的矽卡岩矿床。本文从流体包裹体和氢氧同位素研究入手,讨论了成矿流体的特征、来源和演化及其与成矿的关系。岩相学观察表明,本矿床热液矿物中流体包裹体存在5种类型:富液相气液两相盐水包裹体(Ⅰ类)、含子矿物多相包裹体(Ⅱ类)、富气相气液两相盐水包裹体(Ⅲ类)、纯液相水包裹体(Ⅳ类)和纯气相水包裹体(Ⅴ类)。其中,Ⅰ类包裹体数量最多,各阶段热液矿物中均有发育;Ⅱ类包裹体数量较少,只见于进化交代蚀变阶段的石榴石和早退化阶段的绿帘石中;Ⅲ、Ⅳ和Ⅴ类包裹体数量最少,主要发育于晚退化阶段的石英和方解石中。流体包裹体显微测温表明,从进化交代蚀变阶段→早退化阶段→晚退化阶段,成矿流体经历了从高温(404~562℃)、中-高盐度(11.1%~51.6%NaC leqv)、中-低密度(0.47~0.80g/cm~3)到中-高温(207~465℃)、中-低盐度(2.9%~44.1%NaC leqv)、中-低密度(0.64~0.89g/cm~3)再到中-低温(117~337℃)、低盐度(1.6%~4.5%NaC leqv)、中-高密度(0.90~0.97g/cm~3)的演化过程。氢氧同位素研究表明,进化交代蚀变阶段和早退化阶段的成矿流体主要源于岩浆水,晚退化阶段则有大气降水的加入。根据流体包裹体岩相学特征,结合矿床宏观地质特征,认为流体不混溶(沸腾)是导致本矿区金属沉淀成矿的主要机制。     

TSR成因H2S的硫同位素分馏特征与机制

热化学硫酸盐还原反应(TSR)是深层碳酸盐岩油气藏中硫化氢的主要成因机制,目前已在全球发现了50多个TSR成因的大中型含硫化氢天然气田。通过对中国四川盆地含硫化氢气田硫化物的采集与同位素分析,结合全球含硫化氢天然气田硫同位素分析数据,研究了TSR过程中硫同位素的地球化学行为和分馏特征。研究发现,TSR成因的高含硫化氢天然气中,硫化氢与硫酸盐的硫同位素分馏值小于15‰,主要分布范围为2.5‰~13.82‰,平均在10‰。四川盆地海相层系膏岩的硫同位素值分布较宽,并呈现阶梯状变化,而硫化氢的硫同位素则呈现出相似的分布规律,表明各主要含硫化氢气田硫化氢中的硫来自于本层系的硫酸盐,TSR主要发生在各自的储集层中。四川盆地各气田TSR发生的温度条件相似,硫同位素分馏比较接近。TSR过程中硫同位素的分馏过程与硫酸盐本身硫同位素值的高低无关,而与TSR反应程度有关。TSR反应程度越高,硫化氢的硫同位素值与地层硫酸盐的硫同位素越相近。通过系统分析整理全球含硫化氢气田的硫化物硫同位素数据,并结合四川盆地地质条件和油气演化过程,揭示了TSR过程中硫同位素的分馏特征,并绘制出四川盆地和全球各时代硫化氢和石膏的硫同位素分布曲线图,为研究含油气盆地蒸发岩沉积演化和硫化氢成因提供了参考。     

四川鲜水河-安宁河断裂带温泉氢氧稳定同位素特征

温泉地下水同位素特征对确定断裂带地下水来源、循环过程和断裂带活动性至关重要。为了确定青藏高原东缘温泉的地下水同位素特征和流体来源,本研究采集了鲜水河-安宁河断裂带上温泉水、冷泉水、河流和积雪融水等样品,进行了氢氧稳定同位素和水化学组分测定,并进行了同位素特征的对比研究。分析结果表明,温泉水体δ¹⁸O变化范围为-19.04‰~-12.71‰,平均值为-16.42‰;δ²H变化范围为-144.07‰~-88.63‰,平均值为-122.37‰。河水的δ¹⁸O变化范围为-15.90‰~-10.85‰,平均值为-13.86‰;δ²H变化范围为-118.21‰~-71.12‰,平均值为-98.99‰。康定冷泉δ¹⁸O和δ²H分别为-13.66‰和-106.74‰。道孚积雪融水的δ¹⁸O和δ²H分别为-10.27‰和-65.41‰。不同类型水体样品氢氧稳定同位素组成主要分布在全球和区域大气降水线上,表明了大气降水成因,缺少明显的氧同位素漂移特征。不同类型水体同位素值差异较大,显示出温泉与河水、积雪融水之间补给来源的不一致性。温泉同位素值具有明显的同位素高程效应,鲜水河-安宁河断裂带上氧同位素高程效应为-0.23‰/100m,氢同位素高程效应为-1.95‰/100m。温泉氧同位素漂移与相关离子比值、Na-K-Mg三角图、Li和Sr元素等指标表明研究区域大部分温泉的水岩作用强度弱。氢氧稳定同位素特征、水岩作用特征和循环深度揭示出温泉的成因为远距离大气降水运移补给地下水,地下水在地下热储层加热后通过断裂上升到地表形成温泉,这为认识青藏高原东缘地热水循环、断裂带活动性与演化特征提供了依据。

     

Overview of In-Situ Biodegradation and Enhancement

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｍｅｄｉａｔｉｏｎｂｙｎａｔｕｒａｌａｔｔｅｎｕａｔｉｏｎ (ＲＮＡ)ｉｓｔｈｅｐｒｅｆｅｒｒｅｄｍｅｔｈｏｄｆｏｒｒｅｍｅｄｉａｔｉｎｇｇｒｏｕｎｄｗａｔｅｒｃｏｎｔａｍｉ ｎａｔｅｄｂｙｔｈｅａｒｏｍａｔｉｃｆｕｅｌｈｙｄｒｏｃａｒｂｏｎｓ ,ｂｅｎｚｅｎｅ ,ｔｏｌｕｅｎｅ ,ｅｔｈｙｌｂｅｎｚｅｎｅ ,ａｎｄｘｙｌｅｎｅ (ＢＴＥＸ)ｅｔｃ .(Ｊｅｆ ｆｒｅｙ ,2 0 0 1) .ＢｕｔｔｈｅｒｅａｒｅｃｅｒｔａｉｎｃｏｎｄｉｔｉｏｎｓｕｎｄｅｒｗｈｉｃｈＲＮＡｉｓｉｎａｄｅｑｕａｔｅ…     

Possibilities for the detection of hydrogen peroxide-water-based life on Mars by the Phoenix Lander

The Phoenix Lander landed on Mars on 25 May 2008. It has instruments on board to explore the geology and climate of subpolar Mars and to explore if life ever arose on Mars. Although the Phoenix mission is not a life detection mission per se, it will look for the presence of organic compounds and other evidence to support or discredit the notion of past or present life.The possibility of extant life on Mars has been raised by a reinterpretation of the Viking biology experiments [Houtkooper, J. M., Schulze-Makuch, D., 2007. A possible biogenic origin for hydrogen peroxide on Mars: the Viking results reinterpreted. International Journal of Astrobiology 6, 147-152]. The results of these experiments are in accordance with life based on a mixture of water and hydrogen peroxide instead of water. The near-surface conditions on Mars would give an evolutionary advantage to organisms employing a mixture of H₂O₂ and H₂O in their intracellular fluid: the mixture has a low freezing point, is hygroscopic and provides a source of oxygen. The H₂O₂-H₂O hypothesis also explains the Viking results in a logically consistent way. With regard to its compatibility with cellular contents, H₂O₂ is used for a variety of purposes in terran biochemistry. The ability of the anticipated organisms to withstand low temperatures and the relatively high water vapor content of the atmosphere in the Martian arctic, means that Phoenix will land in an area not inimical to H₂O₂-H₂O-based life. Phoenix has a suite of instruments which may be able to detect the signatures of such putative organisms.     

Dinosterol δD values in stratified tropical lakes (Cameroon) are affected by eutrophication

In freshwater settings, dinosterol (4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol) is produced primarily by dinoflagellates, which encompass various species including autotrophs, mixotrophs and heterotrophs. Due to its source specificity and occurrence in lake and marine sediments, its presence and hydrogen isotopic composition (δD) should be valuable proxies for paleohydrological reconstruction. However, because the purity required for hydrogen isotope measurements is difficult to achieve using standard wet chemical purification methods, their potential as a paleohydrological proxy is rarely exploited. In this study, we tested δD values of dinosterol in both particulate organic matter (POM) and sediments of stratified tropical freshwater lakes (from Cameroon) as a paleohydrological proxy, the lakes being characterized by variable degrees of eutrophication. In POM and sediment samples, the δD values of dinosterol correlated with lake water δD values, confirming a first order influence of source water δD values. However, we observed that sedimentary dinosterol was D enriched from ca. 19 to 54‰ compared with POM dinosterol. The enrichment correlated with lake water column conditions, mainly the redox potential at the oxic–anoxic interface (E_h OAI). The observations suggest that paleohydrologic reconstruction from δD values of dinosterol in the sediments of stratified tropical lakes ought to be sensitive to the depositional environment, in addition to lake water δD values, with more positive dinosterol δD values potentially reflecting increasing lake eutrophication. Furthermore, in lake sediments, the concentration of partially reduced vs. non-reduced C₃₄ botryococcenes, stanols vs. stenols, and bacterial (diploptene, diplopterol and ββ-bishomohopanol) vs. planktonic/terrestrial lipids (cholesterol, campesterol and dinosterol) correlated with E_h OAI. We suggest using such molecular proxies for lake redox conditions in combination with dinosterol δD values to evaluate the effect of lake trophic status on sedimentary dinosterol δD values, as a basis for accurately reconstructing tropical lake water δD values.     

常见硫化物表面的XPS研究

采用XPS分析方法,研究了黄铁矿、磁黄铁矿、方铅矿、黄铜矿、闪锌矿和毒砂等常见硫化物矿物表面的化学成分及其化学态,从而探讨硫化物表面的氧化和次生变化。研究发现：（1）硫化物矿物表面在氧逸度较高的情况下很容易发生变化,其氧化产物很复杂,主要是其金属元素的高价态氧化物、氢氧化物和硫酸盐等;（2）就一般常见硫化物而言,相对比较稳定的是黄铁矿;（3）常见硫化物经氧化后,其表面的原子比率常常显示硫富余;（4）在含铁的各种常见硫化物中,除黄铁矿表面的铁相对稳定外,毒砂表面的铁也相对较稳定,而闪锌矿表面的类质同像铁却容易被氧化而发生变化。