新疆库木库里盆地渐新-上新统孢粉组合特征与古气候演变

通过新疆东昆仑库木库里盆地古近-新近系孢粉分析，将浙新-上新统孢粉划分为7个组合带。根据孢粉组合特征，探讨了造山带上叠库木库里盆地渐新-上新世由稀树草原-森林-森林草原-荒漠草原-森林草原的古植被的演替与暖→冷→暖→冷的古气候演变特征，得出至上新世末期昆仑山海拔已达到3000m左右的高度，这对研究青藏高原的隆升提供了重要依据。     

Oxygen isotopic compositions of chondrules: Implications for evolution of oxygen isotopic reservoirs in the inner solar nebula

We review the oxygen isotopic compositions of minerals in chondrules and compound objects composed of a chondrule and a refractory inclusion, and bulk oxygen isotopic compositions of chondrules in unequilibrated ordinary, carbonaceous, enstatite, and Kakangari-like chondrites, focusing on data acquired using secondary ion mass-spectrometry and laser fluorination coupled with mass-spectrometry over the last decade. Most ferromagnesian chondrules from primitive (unmetamorphosed) chondrites are isotopically uniform (within 3–4‰ in Δ¹⁷O) and depleted in ¹⁶O (Δ¹⁷O>−7‰) relative to amoeboid olivine aggregates (AOAs) and most calcium–aluminum-rich inclusions (CAIs) (Δ¹⁷O<−20‰), suggesting that these classes of objects formed in isotopically distinct gaseous reservoirs, ¹⁶O-poor and ¹⁶O-rich, respectively. Chondrules uniformly enriched in ¹⁶O (Δ¹⁷O<−15‰) are exceptionally rare and have been reported only in CH chondrites. Oxygen isotopic heterogeneity in chondrules is mainly due to the presence of relict grains. These appear to consist of chondrules of earlier generations and rare refractory inclusions; with rare exceptions, the relict grains are ¹⁶O-enriched relative to chondrule phenocrysts and mesostasis. Within a chondrite group, the magnesium-rich (Type I) chondrules tend to be ¹⁶O-enriched relative to the ferrous (Type II) chondrules. Aluminum-rich chondrules in ordinary, enstatite, CR, and CV chondrites are generally ¹⁶O-enriched relative to ferromagnesian chondrules. No systematic differences in oxygen isotopic compositions have been found among these chondrule types in CB chondrites. Aluminum-rich chondrules in carbonaceous chondrites often contain relict refractory inclusions. Aluminum-rich chondrules with relict CAIs have heterogeneous oxygen isotopic compositions (Δ¹⁷O ranges from −20‰ to 0‰). Aluminum-rich chondrules without relict CAIs are isotopically uniform and have oxygen isotopic compositions similar to, or approaching, those of ferromagnesian chondrules. Phenocrysts and mesostases of the CAI-bearing chondrules show no clear evidence for ¹⁶O-enrichment compared to the CAI-free chondrules. Spinel, hibonite, and forsterite of the relict refractory inclusions largely retained their original oxygen isotopic compositions. In contrast, plagioclase and melilite of the relict CAIs experienced melting and ¹⁶O-depletion to various degrees, probably due to isotopic exchange with an ¹⁶O-poor nebular gas. Several igneous CAIs experienced isotopic exchange with an ¹⁶O-poor nebular gas during late-stage remelting in the chondrule-forming region. On a three-isotope diagram, bulk oxygen isotopic compositions of most chondrules in ordinary, enstatite, and carbonaceous chondrites plot above, along, and below the terrestrial fractionation line, respectively. Bulk oxygen isotopic compositions of chondrules in altered and/or metamorphosed chondrites show evidence for mass-dependent fractionation, reflecting either interaction with a gaseous/fluid reservoir on parent asteroids or open-system thermal metamorphism. Bulk oxygen isotopic compositions of chondrules and oxygen isotopic compositions of individual minerals in chondrules and refractory inclusions from primitive chondrites plot along a common line of slope of 1, suggesting that only two major reservoirs (gas and solids) are needed to explain the observed variations. However, there is no requirement that each had a permanently fixed isotopic composition. The absolute (²⁰⁷Pb–²⁰⁶Pb) and relative (²⁷Al–²⁶Mg) chronologies of CAIs and chondrules and the differences in oxygen isotopic compositions of most chondrules (¹⁶O-poor) and most refractory inclusions (¹⁶O-rich) can be interpreted in terms of isotopic self-shielding during UV photolysis of CO in the initially ¹⁶O-rich (Δ¹⁷O−25‰) parent molecular cloud or protoplanetary disk. According to these models, the UV photolysis preferentially dissociates C¹⁷O and C¹⁸O in the parent molecular cloud and in the peripheral zones of the protoplanetary disk. If this process occurs in the stability field of water ice, the released atomic ¹⁷O and ¹⁸O are incorporated into water ice, while the residual CO gas becomes enriched in ¹⁶O. During the earliest stages of evolution of the protoplanetary disk, the inner solar nebula had a solar H₂O/CO ratio and was ¹⁶O-rich. During this time, AOAs and the ¹⁶O-rich CAIs and chondrules formed. Subsequently, the inner solar nebula became H₂O- and ¹⁶O-depleted, because ice-rich dust particles, which were depleted in ¹⁶O, agglomerated outside the snowline (5 AU), drifted rapidly towards the Sun and evaporated. During this time, which may have lasted for 3 Myr, most chondrules and the ¹⁶O-depleted igneous CAIs formed. We infer that most chondrules formed from isotopically heterogeneous, but ¹⁶O-depleted precursors, and experienced isotopic exchange with an ¹⁶O-poor nebular gas during melting. Although the relative roles of the chondrule precursor materials and gas–melt isotopic exchange in establishing oxygen isotopic compositions of chondrules have not been quantified yet, mineralogical, chemical, and isotopic evidence indicate that Type I chondrules may have formed in chemical and isotopic equilibrium with nebular gas of variable isotopic composition. Whether these variations were spatial or temporal are not known yet.     

青海柴达木盆地南八仙油气田油源与成藏机理

柴达木盆地南八仙油气田不同油气藏间原油性质特征变化明显,油层在纵向井段上分布范围逾3000余m。通过地球化学实验并结合构造等地质条件分析,认为该区各种深、浅层油气藏中的原油具有煤成烃的基本地球化学特征,并且为同一来源,油源为临近地区较深部位中侏罗统煤系地层;该区深、浅层原油物性间的差异也反映在地球化学指标上,其成因或成藏机理是：深部早期油藏在断裂等地质作用下发生了明显的蒸发分馏作用,其分馏出的产物在浅部再次聚集成藏。     

油气藏全空间磁学、地球化学与矿物学结构及意义--检验"烟筒效应"的形成机理

位于松辽盆地南部某油气田边缘一个油气显示井的磁性测量结果表明,岩石具有明显的磁性变异结构特征.以磁化率(κ)为例,在低缓的背景磁性上主要呈现高强度与中等强度的2类异常:大于400×10-5为强磁性,100×10-5～150×10-5为中等强度磁性.结合录井资料与地球化学分析解释可知,强磁性异常主要位于取样间隔的底部干层区,少数样品位于浅部油气显示层;中等强度异常主要位于2 700 m附近的油气显示层.岩石磁性与地球化学成分对应分析表明,油气显示层岩石的C1和C2成分与磁化率 (κ)、饱和磁化强度 (Js) 和饱和等温剩余磁化强度(SIRM)之间呈明显的正相关,与内禀矫顽力(Hc)为逆相关,而干层岩石相关性不明显.矿物成分分析显示,岩石中主要含铁矿物为磁铁矿、磁赤铁矿、赤铁矿、黄铁矿和菱铁矿.其中磁赤铁矿主要分布在具有中等磁性强度的油气显示层,而高含量(最高含量达12.5%)的磁铁矿主要位于底部干层.磁赤铁矿与赤铁矿、黄铁矿及菱铁矿含量之间相关特征初步表明,自生磁赤铁矿可能主要来源于原地赤铁矿与黄铁矿.推测油气显示层岩石中磁性偏软的磁赤铁矿属于烃蚀变的产物,为烃微渗漏效应(或烟筒效应)的全空间形成机理提供了新证据.     

黑河流域水资源承载力的生态经济研究

西北干旱内陆河流域水资源是联系生态系统和经济系统的纽带,从生态经济的角度,给出了水资源承载力的概念. 在总结水资源承载力的特点和研究方法的基础上,将水资源承载力的研究纳入了生态经济系统的背景下进行综合集成研究. 以黑河流域中游为例,提出了研究水资源承载力的多目标模型和纳入生态价值模块的途径和方法,从价值量的角度对流域生态系统和经济系统进行了初步的耦合研究,并根据模型的优化分析结果分析了未来20 a黑河流域张掖地区的水资源承载力.     

干法灰化和微波消解-电感耦合等离子体发射光谱法测定植物样品中22个主次量元素

采用干法灰化和微波消解两种样品分解方法处理植物试样,用电感耦合等离子体发射光谱法测定样品中铝、钡、钙、铜、钾、镁、钠、铁等22个主、次量元素的含量,用两种前处理方法对国家一级标准物质进行测定,比对测定值与标准值,验证两种方法的准确度和精密度。结果表明,不同的样品分解方法对各元素的测定结果会产生不同程度的影响。选择适宜的分解方法可以大大提高植物样品中铝、铁、硫等元素测定结果的准确度。干法灰化和微波消解两种前处理方法的精密度(RSD,n=11)均小于5%。     

西昆仑早古生代岩浆弧大同岩体中埃达克质岩石的成因及地质意义

大同岩体位于西昆仑柯冈-库地-其曼于特和麻扎-康西瓦两条蛇绿混杂岩带之间。为进一步了解西昆仑早古生代岩浆弧中某些具体岩石类型、岩浆产生机理、地质意义及成因联系,本文从岩相学、主微量元素地球化学、锆石U-Pb年龄和Hf同位素等方面,对大同岩体中和外围新发现的埃达克质岩石进行了研究。埃达克质岩石由石英二长花岗岩和黑云母二长花岗岩两种岩性组成,呈独立的岩体和大同主岩体中的脉体两种产状,高硅(w(SiO₂)≥60.34%)、高铝(w(Al₂O₃)≥14.73%)、富碱(w(K₂O+Na₂O)≥6.40%)、低镁(w(MgO)≤2.35%),以及高锶(w(Sr)≥504×10^-6)、低钇(w(Y)≤17.20×10^-6)和高Sr/Y(平均为70.88),富集轻稀土元素和大离子亲石元素,亏损重稀土元素和高场强元素,不同程度负Eu异常及Ta、Nb、P和Ti亏损。锆石U-Pb测年显示,埃达克质岩石年龄为(443.6±1.4)~(462.0±1.0)Ma,与大同主岩体的形成年龄相当。锆石ε_Hf(t)为-7.28~4.56(平均-0.84),我们认为埃达克质岩石是由原特提斯洋洋壳及部分洋壳之上的陆源沉积物向南俯冲过程中,发生部分熔融形成的熔体上升过程中与地幔楔橄榄岩反应,最后定位于地壳浅层的结果。通过与大同岩体主岩体对比,对早古生代岩浆弧的形成和演化有了更深入的了解。     

基于均方差-模糊综合评判复合模型的地下水水质评价

首次运用均方差-模糊综合评判复合模型,选取地下水水质的主要影响因子,通过评价因子的选取及评价集的建立、隶属函数及单因子隶属度的确定、评价指标权重的确定和综合隶属度的确定四个步骤,对天津蓟县官庄地区深层地下水水质行了综合评价.评价结果表明,研究区采样点水质总体级别为I级,说明该区地下水水质较好,而局部点位硝酸盐超标是导致水质污染的主要原因,这一结论与该区其它研究成果评价结果相一致.     

鄂尔多斯盆地镇泾油田致密砂岩长8储层特征及沉积相研究

利用扫描电镜、铸体薄片等多种方法,对鄂尔多斯盆地镇泾油田长8油层组低孔低渗的致密砂岩储层的储层特征和沉积相进行综合分析研究,发现该地区砂岩类型主要有细粒岩屑长石砂岩和长石岩屑砂岩,孔隙度和渗透率分别为3.9%%~11%和(0.04~0.55)×10-3μm2。研究区主要成岩作用包括压实作用、压溶作用、胶结作用、溶蚀作用、交代作用。通过对镇泾区块沉积储层形成的沉积相的研究,查明该区广泛发育三角洲相,进一步可划分为水下分流河道、水下天然堤、水下决口扇、水下分流间湾、河口坝等5种微相。上述研究为镇径油田长8段储层的研究和预测提供了理论依据。     

Analytical layer-element solution to axisymmetric consolidation of multilayered soils

After the application of a Laplace–Hankel transform, the governing equations of Biot’s consolidation are solved analytically by using the eigenvalue approach. Then the analytical layer-element of a single soil layer can be obtained in the transformed domain by synthesizing the generalized displacements and stresses, which are both expressed by six arbitrary constants. The elements of the analytical layer-element only contain negative exponential functions, which leads to a considerable improvement in computation efficiency and stability. The global stiffness matrix equation of multilayered soils is further obtained by assembling the interrelated layer-elements, and the actual solution is achieved by numerical inversion of the Laplace–Hankel transform after the solution in the transformed domain is obtained. Numerical examples are given to demonstrate the accuracy of this method and to study the influence of the layered soil properties and time history on the consolidation behavior.