敦密断裂带盆地群油页岩特征及成矿差异分析

古近纪敦密断裂带上分布一系列的含油页岩盆地群。根据盆地间构造-沉积充填、岩石组合和油页岩赋存特征,初步确认盆地群中油页岩沉积于湖盆鼎盛阶段,均形成于古近系始新统路特阶。盆地群间油页岩矿床特征存在明显的差别,由西南向东北,油页岩厚度逐渐变小,其沉积环境由深湖到半深湖,再到湖沼,而有机质来源则由湖泊生物为主,到湖泊生物和陆源有机质双向来源,过渡为以陆源高等植物为主。结合含油页岩层系形成于同一时期和相似的古气候背景下,盆地沉降和沉积充填作用是影响油页岩矿床差异的关键因素。长期处于欠补偿环境,可容纳空间大的湖盆利于巨厚油页岩的形成,随着可容纳空间的减少、陆源碎屑供给的增多,油页岩厚度减薄,分布也变得相对局限。深湖和湖沼成因油页岩品质较好,半深湖油页岩品质较差。     

西南印度洋中脊表层沉积物非碳酸盐组分的粒度特征及其地质意义

The carbonate-free fraction of 20 surface sediments collected from the ultraslow-spreading Southwest Indian Ridge(SWIR) was studied by grain size analysis and mineralogical analysis with X-ray powder diffraction(XRD),stereo microscopy and scanning electron microscopy(SEM). The characteristics of the carbonate-free fraction of the sediments were obtained, and related influential factors were discussed. The results show that the mean grain size of this fraction is in 1.96Φ–8.19Φ, with poorly sorting and unimodal, bimodal or irregular bimodal distribution patterns. Four grain size end members of the fraction are derived with the End Member Model method. The finest end member EM1 shows a significant contribution of terrigenous materials of the aeolian input and sediment carried by the bottom current. End member EM2 with medium size mainly reflects sediment of a siliceous bioclast origin. EM3 and EM4 are interpreted as representing the coarser volcanic materials related to bedrock weathering or volcanic activities. Multi-provenance is the dominant factor controlling the grain size pattern of the carbonate-free fraction of the sediments in that area. In addition, sediment transport processes such as the bottom current and wind are the minor factors that influence the grain size distribution of the carbonate-free fraction sediments.     

New Early Cretaceous paleomagnetic results from Qilian orogenic belt and its tectonic implications

Lower Cretaceous red sedimentary rocks from the depositional basin of East Qilian fold belt have been collected for a paleomagnetic study. Stepwise thermal demagnetization reveals two or three components of magnetization from dark red sandstones. Low-temperature magnetic component is consistent with the present Earth Field direction in geographic coordinates. High-temperature magnetic components are mainly carried by hematite. The mean pole of 19 sites for high-temperature magnetic components after tilt-correction is λ=62.2°N, φ=193.4°E, A95=3.2°, and it passes fold tests at 99% confidence level and reversal tests at 95% confidence level. The paleopole is insignificantly different from that of Halim et al. (1998) from the same sampling area at the 95% confidence level. Compared with paleomagnetic results for North China, South China, and Eurasia, our results suggest that no significant relative latitudinal displacement has taken place between Lanzhou region and these blocks since Cretaceous time. Remarkably, the pole of Lanzhou shows a 20° clockwise rotation with respect to those of North China, South China, and Eurasia. Geological information indicates that the crustal shortening in the western part of Qilian is greater than that in eastern part. In this case, the clockwise rotation of sampling area was related to India/Eurasia collision, and this collision resulted in a left-lateral strike-slip motion of the Altun fault in north Tibetan Plateau after the Cretaceous.     

轴对称稳恒磁场的一种解法

本文依据稳恒磁场中的高斯定理和安培环路定理，用迭代法推导出对称轴上的磁感应强度与空间任意一点磁感应强度的关系式，从而可得出轴对称稳恒磁场的无电流分布空间的解式。     

激光剥蚀-扇形磁场电感耦合等离子体质谱法同时测定锆石U-Pb年龄和微量元素含量

激光剥蚀-扇形磁场电感耦合等离子体质谱(LA-SF-ICP-MS)具有高灵敏度特征,被广泛应用于锆石等含U矿物原位微区U-Pb定年研究,但磁偏转式质量分析器的使用导致该质谱仪扫描速度相对较慢,可能影响U-Pb同位素与其他关键微量元素的同时采集。本文通过优化仪器信号稳定性和实验方法,对目前常用的7种锆石U-Pb标准样品进行U-Pb定年和Ti、REEs、Hf等关键元素同时定量分析,探讨了多元素同时分析方法的可行性及对于U-Pb定年结果的影响。实验结果表明,相对于LA-SF-ICP-MS仅检测U-Pb同位素方法,同时开展多元素含量检测可能会使U-Pb同位素信号强度稳定性下降,导致单点U-Pb年龄结果误差及离散程度增大。与仅测定U-Pb同位素年龄的测定结果相比较,根据不同锆石样品中U-Pb同位素含量高低,多元素同时检测获得分析点的²⁰⁶Pb/²³⁸U年龄和²⁰⁷Pb/²³⁵U年龄变化范围不同程度地增大,其中²⁰⁷Pb/²³⁵U年龄受影响明显,单点^207<...     

地电化学异常形成机理初探

一直以来,人们都倾向认为地电化学方法取得的异常是由其吸附的金属离子引起,文中通过多个矿区地电化学试验发现,电提取微量元素异常往往与Fe、Al等常量元素异常高度一致,而Fe、Al等常量元素是组成粘土矿物的主要成分. 进一步对地电化学泡塑样品开展扫描电镜观测,发现电提取后泡塑载体样品中存在大量的大小从数微米至数十微米的粘土矿物颗粒. 由此初步推断,当前所使用的地电化学方法取得的异常很大程度上是由土壤中存在的具有电活动性的极细粒粘土矿物颗粒引起,地电化学提取过程对这些粘土矿物颗粒具有选择性吸附.     

Guadalupian （Middle Permian） Conodont Faunas at Shangsi Section, Northeast Sichuan Province

This study recovered the Guadalupian conodont faunas from Shangsi (上寺) Section in Northeast Sichuan (四川). Four genera and nine species were identified, and three conodont zones were recognized and established; they include Jinogondolella nankingensis Zone, J. aserrata Zone, and J. postserrata Zone. The Roadian and Wordian boundary is set in the interval 5 m from the top of Bed 86 by the first appearance of the conodont J. aserrata. The Wordian and Capitanian boundary is set in the interval 2.3 m from the top of the Bed 95 by the first appearance of J. postserrata. Most of the specimens demonstrated low color alteration index (CAI) as 1.5-3, indicating that most part of the Maokou (茅口) Formation may have the suitable thermal conditions for the formation of oil source rocks.     

基于区域水准和跨断层资料分析云南地区地壳形变

为了获取云南地区现今地壳形变和断层活动特征,收集了云南地区1992—2016年的2期精密水准观测资料,采用基于GNSS连续站垂直形变资料约束的平差方法,对区域整体地壳垂直形变特征进行了分析,结果显示滇西北区域地壳整体表现为隆升,垂向速率为2—3mm/a,滇南区域显示地壳沉降速率为-1—-2mm/a,并在下关—永胜和思茅—景谷一带存在地壳形变高梯度带。收集了该地区30多年的跨断层场地观测资料,计算了所跨断层的三维活动量,得出了断层现今活动状态和异常特征,认为滇西北和滇中南地区的场地多数表现出异常活动的现象,其中楚雄、剑川和永胜的监测断层现今表现出与地质背景相反的走滑和拉张特征,峨山、建水和通海场地所处断层在张压性质上与地质背景相反。结合区域水准和跨断层观测分析结果,从“面”和“线”上得出滇西北和滇中南地区存在地壳形变和断层活动异常,构造应力积累较高的结果,加之缺震背景显著,认为应关注该区域中强地震的危险性。     

魁蚶(Scapharca broughtonii)半乳糖凝集素(SbGal)基因cDNA的克隆及表达分析

半乳糖凝集素(Galectin)作为动物凝集素家族的一员,是一种重要的免疫因子,在脊椎动物和无脊椎动物中都参与了重要的免疫防御反应。为明确魁蚶(Scapharca broughtonii)半乳糖凝集素基因的结构特征、组织分布及其对病原菌刺激的免疫反应规律,本研究从构建的魁蚶转录组文库中筛选得到半乳糖凝集素基因部分序列,通过c DNA末端快速扩增(rapid amplication of c DNA ends,RACE)技术获得该基因c DNA全长序列(命名为Sb Gal)。序列和结构分析表明,该c DNA全长3120bp,编码554个氨基酸,是一个含有4个糖识别结构域(CRD)的且在双壳贝类中较为独特的半乳糖凝集素;预测蛋白的分子量(Mw)为63.3158 k Da,理论等电点(p I)为4.99。同源性及系统分析表明,Sb Gal基因与美洲牡蛎、合浦珠母贝、海湾扇贝galectin的同源性分别为70%、65%、46%,Sb Gal基因四个CRD彼此的相似性为36%—41%。实时荧光定量PCR(q RT-PCR)结果表明:Sb Gal m RNA在魁蚶血细胞、斧足、闭壳肌、外套膜、鳃和肝胰腺中均有表达,血细胞中的表达量最高,在肝胰腺中的表达量最低;注射鳗弧菌后,相对于对照组,Sb Gal基因在所检测的每个组织中m RNA水平上的表达量都显著上调(P0.01),而且表达量具有显著的时间依赖性和瞬时表达趋势,呈现先升高后降低的趋势。