地壳增长与壳—幔再循环

在会聚边缘的地壳增长目前是由地壳从地幔中的萃取作用所支配的,这是一个只能间接观察到的过程。在现代的会聚边缘,常见于地壳最上部的玄武岩和安山岩(及相应的侵入岩)并非直接源于地幔(如它们不是地幔的初始成分)。例如,在阿留申岛弧,橄榄拉斑玄武岩已被认作是初始岩浆,它与普通高铝玄武岩有关,而后者是由积聚在莫霍面深处的橄榄石和辉石的分离作用所形成的,并代表一个新生的上地幔,更常见的浅部富铝质火山岩及深成岩可以由高铝玄武岩的壳内组分分异、岛弧地壳低熔组分的同化、地壳熔融所形成,或者是诸过程结合的产物。每个岛弧真正的地壳剖面取决于岛弧     

Survival, growth, metallothionein and glycogen levels of Nucella lapillus (L.) exposed to subchronic cadmium stress: the influence of nutritional state and prey type

Dogwhelks Nucella lapillus feed mainly on mussels and barnacles, and may experience periods of starvation. We report effects of nutritional state and prey type on the survival, growth, cadmium (Cd) accumulation, metallothionein (MT) induction and glycogen stores in N. lapillus exposed to Cd in water. Adult dogwhelks, with similar shell length (30.0+/-1.5 mm), were either starved or fed to satiation with barnacles Semibalanus balanoides, mussels Mytilus edulis or Cd-dosed M. edulis, and kept in filtered natural seawater (< 0.01 microg Cd 1(-1)) or Cd-contaminated (400 microg Cd 1(-1)) seawater for 80 days. Mortality and individual growth rate were determined. Cd, MT and glycogen were measured in different tissues. Prolonged starvation and exposure to Cd significantly reduced the survivorship of N. lapillus, but feeding could help dogwhelks to combat Cd toxicity and minimise mortality. Extended starvation also caused tissue wastage, leading to higher concentrations of Cd and MT in tissues, whereas fed animals increased in weight and had lower Cd and MT concentrations because of the tissue dilution effect. Prey type significantly affected growth rate of dogwhelks and indirectly influenced Cd accumulation, MT induction and glycogen stores. Eating mussels promoted better growth and higher glycogen reserves than eating barnacles. Individual growth rate decreased with increasing Cd accumulation. Cd-exposed survivors grew faster and consumed more than control animals, implying that these survivors may have better fitness and greater tolerance to Cd toxicity. The use of growth, condition index, MT and glycogen as biomarkers of environmental pollution are discussed. These results indicate a need to incorporate biological data including growth (or at least condition index) and prey type into biomonitoring programmes to allow sound interpretation.     

青海木里三露天天然气水合物地球化学远景评价

对青海木里三露天天然气水合物矿藏进行了地球化 学精查,面积10 km²,采样密度为16个点/km²,分析了土壤酸解烃和顶空气。对精查地球化学异常进行了解释,着重于天然气水合物矿藏和天然气藏的区分,以及水合物靶区预测等问题。研 究表明,综合地球化学异常和冻土厚度能够有效区分水合物和浅层气,酸解烃和顶空气重烃比值能够圈定天然气水合物靶区。8个天然气水合物发现井(DK-1、DK-2、DK-3、DK-7、DK-9、 DK12-13 、DK11-14和DK10-17)位于靶区内,全部的水合物干井(DK-4、DK-10、DK10-16、DK10-18、DK7-20、DK-6、DK6-21、DK4-24）位于背景区。     

利用油气化探技术评价青藏高原羌塘盆地海相碳酸盐岩地区构造的含油气性

用浅表地球化学方法评价青藏高原碳酸盐岩区块的油气资源潜力是盆地勘查阶段的战略问题之一。研究了羌塘盆地托纳木区块的油气地球化学异常特征、异常成因和圈闭的油气属性。研究表明,托纳木背斜是羌塘盆地非常有远景的油气靶区,油气化探能够为区块油气资源评价提供重要的地球化学信息。     

Impacts of diverted freshwater on dissolved organic matter and microbial communities in Barataria Bay, Louisiana, U.S.A

Here we present results of an initial assessment of the impacts of a water diversion event on the concentrations and chemical composition of dissolved organic matter (DOM) and bacterioplankton community composition in Barataria Bay, Louisiana U.S.A, an important estuary within the Mississippi River Delta complex. Concentrations and spectral properties of DOM, as reflected by UV/visible absorbance and fluorescence, were strikingly similar at 26 sites sampled along transects near two western and two eastern areas of Barataria Bay in July and September 2010. In September 2010, dissolved organic carbon (DOC) was significantly higher (568.1-1043 μM C, x=755.6+/-117.7 μM C, n=14) than in July 2010 (249.1-577.1 μM C, x=383.7+/-98.31 μM C, n=14); conversely, Abs254 was consistently higher at every site in July (0.105-0.314) than in September (0.080-0.221), averaging 0.24±0.06 in July and 0.15±0.04 in September. Fluorescence data via the fluorescence index (FI450/500) revealed that only 30% (8 of 26) of the July samples had an FI450/500 above 1.36, compared to 96% (25 of 26) for the September samples. This indicates a more terrestrial origin for the July DOM. Bacterioplankton from eastern sites differed in composition from bacterioplankon in western sites in July. These differences appeared to result from reduced salinities caused by the freshwater diversion. Bacterioplankton communities in September differed from those in July, but no spatial structure was observed. Thus, the trends in bacterioplankton and DOM were likely due to changes in water masses (e.g., input of Mississippi River water in July and a return to estuarine waters in September). Discharge of water from the Davis Pond Freshwater Diversion (DPFD) through Barataria Bay may have partially mitigated some adverse effects of the oil spill, inasmuch as DOM is concerned.     

松辽盆地土壤溴的地球化学特征及其对油气的指示

Br和I是卤族元素的重要成员,I用于油气勘查取得了较好的找矿效果,但是,目前还未见到国外有关Br元素勘查油气的报道。应用松辽盆地中部8.15×104km2的多目标地球化学勘查数据,在研究土壤Br元素近地表影响因素的基础上,试验了表层土壤Br和深层土壤Br的区域地球化学异常对油气的指示意义。在松辽盆地中部发现了表层土壤Br的地球化学巨省和深层土壤Br的地球化学巨环,它们与油气富集区带、大中型油气田和火山岩油气藏相联系。土壤Br元素的表生地球化学作用和油气微渗漏是表层巨省和深层巨环形成的主要机制,因而,土壤Br元素也是战略性油气地球化学填图的一个新的辅助指标。