赣北修水观音阁砾岩特征及其构造意义

有关赣北地区双桥山群内角度不整合和地壳运动存在与否问题,一直争论不休。论文以较丰富的详细野外调查资料为基础,并结合前人研究成果和室内各类样品测试结果,围绕这个赣北地区重要的基础地质问题进行了讨论。作者认为“修水运动”不能成立,并提出了砾岩的沉积模式。     

土石混合体分形几何特征与强度演化特征

针对土石混合体的结构性特点,以含石量为20%、30%、40%、50%、60%的土石混合体为研究对象,基于多重分形原理研究多重分形特征,研究分形维数与强度之间的关系。研究表明,土石混合体具有双重分形特征,不同尺度条件下具有不同分形指标,包括块石粒度、土体粒度以及平均粒度等分形维数,与含石量相关。单轴压缩试验表明,抗压强度随含石量增加呈现先增大后减小的趋势,根据单维分形特征,确定最优含石量约为40%。建立了含石量、不同分形维数指标与抗压强度之间的关系,分析了双重因素综合影响下抗压强度的变化特征,确定了含石量与分形维数之间存在最优区域。     

天山地区SAR数据雪盖制图研究

在分析合成孔径雷达（ＳＡＲ）成像机理及雪盖参数散射特性的基础上，利用航天飞机搭载的成像雷达（ＳＩＲ－Ｃ）获取的天山Ｃ波段、多极化ＳＡＲ数据，进行提取雪盖信息的实验。数据通过预处理、散射系数图像的计算、去噪、入射角改正等处理后，利用ＢＡＹＥＳ监督分类方法产生该地区的雪盖分类图。实验结果表明，利用多波段、多极化ＳＡＲ进行雪盖制图是可行的。     

青藏高原东南缘次林错岩体晚白垩世—早新生代快速剥蚀

青藏高原东南缘是研究构造、地貌演化和气候变化相互作用的理想场所,前人研究主要揭示了晚始新世—早中新世和晚中新世以来的快速剥蚀事件,缺乏晚白垩世—早新生代时期地貌演化过程的研究。次林错花岗岩已有的低温热年代学数据覆盖了整个新生代时期,为探索该区域新生代早期的剥露演化历史提供了重要资料。该岩体新生代早期冷却事件是岩浆冷却单一作用的结果,还是受快速剥蚀作用的影响,目前仍然存疑,需要定量研究。因此,本文结合已有的岩石地化和年代学数据,对次林错花岗岩开展了锆石饱和温度和一维岩浆冷却模拟研究。锆石饱和温度计算结果表明次林错花岗岩的岩浆结晶温度介于647～705℃之间,属低温花岗岩。一维岩浆冷却模拟结果显示岩体侵位时的最小围岩温度为160～120℃,对应深度约为3.7～5.0 km。结合锆石和磷灰石(U-Th)/He年代学数据,本文认为该岩体在晚白垩世—早新生代时期(67～40 Ma)经历了一期剥蚀量至少为2 km的快速剥蚀事件。已发表成果的综合分析表明,此次快速剥露事件可能是整个青藏高原地区广泛存在的构造剥蚀事件,新特提斯洋的俯冲闭合与印亚板块的初始碰撞可能是触发此次大规模区域剥蚀的主要原因。     

Investigation of manganese tolerance and accumulation of two Mn hyperaccumulators Phytolacca americana L. and Polygonum hydropiper L. in the real Mn-contaminated soils near a manganese mine

Up to date, very few studies have examined the phytoextraction ability of hyperaccumulators in the real soils contaminated with heavy metals following the identification of the hyperaccumulators using hydroponics tests. In the present study, amended with a chemical-mobilizing agent of ethylene diamine triacetic acid (EDTA), the manganese accumulation, tolerance and the hyperaccumulating ability of two hyperaccumulators Phytolacca americana L. (Phytolaccaceae) and Polygonum hydropiper L. (Polygonaceae) proved by previous hydroponics tests were examined using pot experiments with paddy soils contaminated with Mn (1,047 ± 53 mg kg^?1) collected from one site in the vicinity of one manganese mine in Xiushan county of Chongqing, China. Results showed that the root and shoot biomass of P. americana and the chlorophyll production of P. hydropiper were significantly inhibited by EDTA treatments while the chlorophyll production of P. americana was oppositely obviously promoted by EDTA. It is noteworthy that, with or without EDTA treatment, the shoot Mn concentrations of both plant species were significantly below the hyperaccumulator threshold, indicating these two plants concealed their hyperaccumulating ability in the studied soils. Thus, further detailed studies need to be conducted to promote the metal hyperaccumulating capacity of these two plant species under comparably low Mn-contaminated soil conditions as shown in this study before the successful application of these Mn hyperaccumulators identified in laboratories to the phytoextraction of lightly or moderately Mn-contaminated agricultural soils.     

Spatial distribution of surface soil water content under different vegetation types in northwest Guangxi, China

Geostatistical and statistical analyses were combined to examine the spatial distribution of soil water content under four vegetation types during the dry season, in the peak-cluster depression in the karst region in northwest Guangxi, southwest China. The soil water content significantly increased from farmland to plantation, secondary forest, and primary forest; whereas the variation coefficients, the sill (C ₀+C), and total spatial variance increased, although the range decreased. The spatial distribution of soil water content in the different vegetation types had a high spatial autocorrelation. Different models produced a best fit for the semivariograms of the four vegetation types. Elevation and slope position were the primary factors influencing the spatial distribution of soil water content, with other key factors differing between the four vegetation types. Moreover, even though different specific factors influenced soil water content in the four vegetation types, the correlations and degrees of associations between the soil water content and these various factors differed. Therefore, the corresponding strategies for rational usage and management of water resources should be different for the four vegetation types in this region.     

Analysis of boundary friction effect on the homogenization process of compacted bentonite/claystone mixture with technological voids upon hydration

Pre-compacted MX80 bentonite/Callovo-Oxfordian (COx) claystone mixture has been proposed to backfill and seal the underground galleries for radioactive waste disposal in France. While emplacing these pre-compacted blocks, technological voids are created between the blocks and the host rock and among the blocks themselves. It is expected that homogenization process will take place over time for the structure constructed with pre-compacted blocks upon hydration. This study investigated the boundary friction effect on such a process. Results showed that after the filling of technological voids, the soil far from the technological voids would swell further, while those near the voids would be compressed under the welling pressure generated by the soil behind, resulting in an increase in homogeneity in terms of dry density distribution. However, this homogenization process would stop after a certain time. Further examination showed that the homogenization process ended when the maximum boundary friction force became equal to or higher than the vector sum of swelling forces in the radial direction. Based on the force equilibrium and the mass conservation, the final dry density distribution was estimated. Comparison between the estimation and the measurement showed a good agreement, indicating the relevance of the identified mechanism related to boundary friction.

     

卡尼期湿润幕：气候- 环境变化与海洋生态效应研究新进展

晚三叠世卡尼期湿润幕（Carnian Pluvial Episode, CPE）是近年来最受瞩目的地质事件之一。此次事件以卡尼中期全球不同纬度环境湿度显著上升为主要标志。CPE的发生不仅对全球各地沉积格局产生重大改变，也对三叠纪生物演化产生了深远影响。海洋生物群在跨越CPE期间发生了不同程度的灭绝与演替，大部分海洋无脊椎动物和部分脊椎动物的多样性在CPE之后出现明显的降低，著名的关岭生物群也受到了CPE的明显影响，并开始显现出危机。CPE之后，恐龙类群开始逐步占据陆地生态的主导地位，早中生代和现代生物的先祖开始在这一时期纷纷出现。CPE的发生揭开了现生生物演化史新的一页，并最终开创了早中生代和现生生物黎明。有关CPE的触发机制主要包括以下2个方面：① 晚三叠世巨型季风环流在卡尼期达到鼎盛并区域上影响了大气降水量；② 板块活动造成大规模火山喷发引发全球气候扰动。由于上述2种解释还未能与我国其他地质记录较好匹配，因而CPE在特提斯东缘的发生次序和发展过程并不清晰。这其中，对CPE触发机制的探讨，需要将全球板块变化与古气候模拟纳入其研究范畴。不同于晚二叠世生物大灭绝后生物类群缓慢重启和生态逐步复苏，CPE期间的生物演化与革新在短时间内促成了现代生物类群的形成。在我国，上三叠统卡尼阶分布广泛、发育齐全，且保存有各门类丰富的动植物化石，是开展卡尼期气候- 环境变化与生态效应研究的重要场所。然而目前国内有关CPE研究还十分有限，一些基础的地质工作仍然有待开展。位于特提斯东缘的我国地质记录有助于深刻理解CPE过程和环境- 生物协同演化关系，尤其在现代生物多样性起源和当代生态系统结构成型的研究过程中需要提供更多中国的对比方案。     

开发尺度的曲流河储层内部结构地震沉积学解释方法

曲流河地层内部结构复杂,岩性界面具有穿时性,传统的地震相分析法不能满足油藏开发地质研究中对储层内部结构精细解释的需要,急需探索有效的地震解释方法。采用基于探地雷达的露头探测、点坝复合体三维正演模拟和实际地震资料相结合的方法,分析了地震资料频率和地层厚度对曲流河内部结构地震反射特征的影响,研究了利用地层切片解释曲流河沉积结构的原理和方法,建立了开发尺度的曲流河内部结构地震沉积学解释技术。研究发现:(1)高频地震资料中地震反射能够反映曲流河侧积复合体边界,而低频地震资料中反射同相轴与岩性界面一致;(2)不同厚度的点坝侧积单元地震反射特征存在差异,造成反射剖面的多解性。同时指出曲流河内部结构地震沉积学解释的技术关键:(1)发挥地震资料平面与剖面信息的相互约束和补充;(2)将地质体作为三维空间发育的成因体,利用其平面与剖面特征的成因联系指导解释;(3)级次化解释方法,在不同级次上采用针对性的解释方法。将该方法应用于墨西哥湾新近系地震沉积学解释,实现了曲流河点坝复合体内部结构的三维刻画。     

中国东北地区的构造格局与演化:从500Ma到180Ma

中国东北变质基底为由含矽线石榴片麻岩、角闪斜长片麻岩、石墨大理岩和各种长英质片麻岩组成的孔兹岩系。采自额尔古纳、兴安、佳木斯和兴凯地块的矽线石榴片麻岩样品的锆石U-Pb测年均指示高级变质发生在500Ma左右。来自松辽地块古生代沉积物碎屑锆石的证据也表明约500Ma构造岩浆事件的存在。跨越整个中国东北不同地块的泛非期高级变质岩形成了超过1 300km北西向展布的晚泛非期"中国东北孔兹岩带",以顺时针p/T轨迹的孔兹岩带与同期岩浆杂岩共同构成了一巨型的约500Ma前后的造山带,笔者这里命名为"中国东北早古生代造山带"。这证明了中国东北各地块在500Ma之前已经拼合,并与西伯利亚克拉通具有构造亲缘性,曾是晚泛非期(500 Ma)西伯利亚南缘Sayang-Baikal造山带的组成部分。450Ma之后,已经拼合的中国东北地块群从西伯利亚裂解,向南朝现今的中国东北漂移;230Ma前后,东北地块群沿索伦—西拉沐伦—长春缝合带与华北板块碰撞;210～180 Ma,由于太平洋板块的俯冲导致佳木斯地块与西部松辽地块最终拼贴,沿佳木斯—兴凯地块西缘和南缘形成一弧形高压带(包括佳木斯—兴凯地块西缘黑龙江蓝片岩带和佳木斯—兴凯地块南缘长春—延吉带),这里简称"吉林—黑龙江高压变质带",之后东北地区进入了环太平洋构造域演化阶段并持续至今。