施主掺杂多晶(Sr,Ba)TiO_3微观结构和介电性能的研究

系统地研究了施主掺杂对多晶SrTiO_3,(Sr,Ba)TiO_3微观结构和介电性能的影响。SEM观察表明:掺杂不同施主,对多晶SrTiO_3晶粒生长起着不同的作用。施主掺杂量影响多晶SrTiO_3,(Sr,Ba)TiO_3晶凿的半导化程度及试样介电特性。     

浙西北中生代火山岩的基本特征及成岩机理研究

根据野外调查研究和145个样品的分析结果,讨论了浙西北中生代火山岩的基本特征,并在研究火山岩中微量元素组合、稀土元素分布和锶同位素组成的基础上得出如下结论:浙西北不同火山盆地和火山洼地中的酸性和中酸性火山岩的成岩机理基本相同,成岩物质主要来自硅铝壳,成岩温度为1020—1200℃。     

Early Pleistocene formation of the asymmetric east-west pattern of upper water structure in the equatorial Pacific Ocean

Surface-and subsurface-dwelling planktonic foraminifera from the upper 43 m of Hole A at the Ocean Drilling Program (ODP) Site 807,which was recovered from the western Pacific warm pool during ODP Leg 130,were analyzed for stable oxygen and carbon isotopes.By comparing these results with data from ODP Site 851 in the eastern equatorial Pacific,this study has reconstructed the paleoceanographic changes in upper ocean waters in the equatorial Pacific since 2.5 Ma.During the period from 1.6-1.4 Ma,the oxygen isotopes of surface and subsurface waters were found to markedly change in the western and eastern equatorial Pacific,further confirming the final formation of the well-defined asymmetric east-west (E-W) pattern at that time.This feature was similar to the zonal temperature gradient (sea surface temperature is higher in the west and lower in the east) and the asymmetric upper water structure (thermocline depth is deeper in the west and shallower in the east) in the modern equatorial Pacific.The zonal gradient change of subsurface water δ18O was greater than that of surface water δ18O,indicating that the formation of the asymmetric E-W pattern in the equatorial Pacific should be much more related to the shoaled thermocline and markedly decreased subsurface water temperature in the eastern equatorial Pacific.Moreover,since ～1.6 Ma,the carbon isotopic differences between surface and subsurface waters clearly decreased in the equatorial Pacific,and their long-term eccentricity periods changed from 400 ka to ～500 ka,reflecting the reorganization of the ocean carbon reservoir.This probably resulted from the deep water reorganization in the Southern Ocean at that time and its enhanced influence on the tropical Pacific (especially subsurface water).Our study demonstrates that the tropical ocean plays an important role in global climate change.     

Re-visiting barium isotope compositions of mid-ocean ridge basalts and the implications

Barium (Ba) isotopes can be used as potential tracers for crustal material recycling in the mantle. Determination of the Ba isotope composition of the depleted mantle is essential for such applications. However, Ba isotope data for mantle-derived basalts are still rare. In this study, we reported high-precision Ba isotope data of 30 oceanic basalts including 25 mid-ocean ridge basalts (MORBs) from geochemically and geologically diverse mid-ocean ridge segments and five back-arc basin basalts. The δ138/134Ba values of these samples varied from ?0.06‰ to +0.11‰, with no systematic cross-region variation. Together with published data, we constrained the average δ138/134Ba of global MORBs to +0.05‰±0.09‰ (2 standard deviation, n = 51). Based on depleted MORBs that have (La/Sm)_N < 0.8, low 87Sr/86Sr (< 0.70263), and low Ba/Th < 71.3, we estimated the average δ138/134Ba of the depleted MORB mantle (DMM) as + 0.05‰ ± 0.05‰ (2SD, n = 16) that is significantly lower than the DMM (≈ 0.14‰) reported previously. If a new estimation of the DMM is applied, it is unreasonable to infer that the Ba isotope signatures of the “enriched-type” MORBs (E-MORBs) could be attributed to pervasive sediment recycling in the upper mantle. We, therefore, conclude that the Ba isotope compositions of the E-MORBs could be sourced from the incorporation of subducted altered oceanic crust and/or sediments depending on the Ba isotope composition and other geochemical information of the local mantle.     

Constraining the Ediacaran oceanic dissolved organic carbon reservoir: Insights from carbon isotopic records from a drill core from South China

The evolution of the atmospheric oxygen content through Earth’s history is a key issue in paleoclimatic and paleoenvironmental research. There were at least two oxygenation events in the Precambrian that involved fundamental changes in both biotic innovation and the surface environment. However, a large dissolved organic carbon (DOC) pool maintained in deep oceans during the Neoproterozoic may have extended the time interval between the two oxygenation events. To test the DOC hypothesis, we conducted detailed micro-drilled analyses of carbonate carbon isotopes (δ13C_carb) of a long Ediacaran drill core (the Wangji drill core), for which whole-rock δ13C_carb and organic carbon isotope (δ13C_org) records were available. The micro-drilled δ13C_carb values obtained in this study are consistent with whole-rock δ13C_carb results, precluding the influence of severe authigenic carbonate incorporation. Importantly, the multiple negative δ13C_carb excursions in the Wangji drill core were likely linked with upwelling events, during which DOC was supplied to the surface water and oxidized. Using box models, we estimate that ~3.6 × 1019 mol and ~2.0 × 1019 mol DOC were converted to bicarbonate during two negative δ13C_carb excursions spanning millions of years. The estimations are approximately 1000 times the modern marine DOC reservoir. Our results support a relatively high oxidation capacity (elevated atmospheric pO₂ and/or oceanic [\begin{document}${\rm{SO}}_4^{2 - }$\end{document}]) of the Earth’s surface during the early Ediacaran Period.     

川东南二三叠系气藏硫化氢成因探讨

通过天然气组分、碳氢同位素组成与薄片、包裹体等资料分析,研究了川东南二-三叠系的长兴组、飞仙关组与茅口组气藏H₂S成因。结果表明,天然气组分以烷烃气为主,非烃含量平均24.68%。其中,烷烃气均偏干,部分样乙烷低于检测下限,可测样乙烷含量0.03%~0.39%,均值0.15%;δ¹³C₁值均偏重,为–28.3‰~–35.2‰,平均–31.1‰,部分样出现δ¹³C₁ > δ¹³C₂倒转。非烃以CO₂和H₂S为主,H₂S含量1.0%~21.7%,平均5.3%。储层中代表原油充注与古油藏裂解的各类沥青较少见,方解石脉中烃类包裹体以含气态烃包裹体为主,含油包裹体少见。结合前人研究成果认为,川东南茅口组几乎不含H₂S的岩溶缝洞型气藏（分布于涪陵北部与綦江地区）未见遭TSR改造迹象;飞仙关组气藏（分布于涪陵北部）、长兴组气藏（主要分布于涪陵北部与中部）与茅口组热液白云岩气藏（分布于涪陵中南部）的H₂S均为TSR成因,部分遭受TSR改造气藏现今H₂S含量较低或为后期被消耗所致;其中,飞仙关组参与TSR反应的烃类以液态烃为主,而其他层位气藏以气态烃（甲烷）为主,这可能与TSR发生时储层中是否存在一定量液态烃有关。TSR反应于各层内独立发生,并非飞仙关组发生后向下“倒灌”。长兴组TSR反应所需硫源或来自飞仙关沉积期卤水的侧向排泄,茅口组硫源或来自相邻层位富含SO₄^2-流体。     

石墨炉原子吸收法测定饱和盐水中锶

利用石墨炉原水吸收法直接测定了饱和盐水的微量锶，选择了各种试验条件，建立了一种准确快速测定微量锶的方法，测定一次盐水，二次盐水的变异系数分别为3．1％、2．5％，二次盐水的加标回收率在90．3-100．9％之间．     

上扬子石炭纪锶碳同位素和微量元素铝与海平面变化的关系

研究表明海相碳酸盐锶、碳同位素与海平面变化有一定的相关关系,其中碳同位素反应灵敏。此外,微量元素Al的变化也是海侵海退旋回的良好标志。