中国东北全新世干湿状况的演变

通过综合分析植物花粉,沙土埋藏土壤,泥炭形成与发展,沙丘活动历史,黄土状土堆积和黑土发育等多种资料表明,我国东北地区的湿润程度或土壤水分含量在５ｋａ ＢＰ以前的早中全新世较低,中晚全新世不能增加,早中全新世最干燥时段出现的＾１４Ｃ年代９－８ｋａ ＢＰ,中晚全新世湿润时期可能是最近的２ｋａ,近现代气候比过去１０ｋａ平均状况湿润。     

洞穴石笋沉积旋回主要特征的古气候环境研究

通过对我国南方大型石笋组分、结构构造的观测和董哥洞10号(D10)石笋210件碳、氧同位素组成、20个U系测年数据,以及部分微(痕)量元素的分析对比,概述了石笋沉积旋回性特征、旋回界面类型和相关的气候、环境、地质意义.以组成D10石笋的碳酸盐含碳质、黏土矿物,呈黑灰、灰黄、灰白、灰等色泽匹配、纹层厚及组合、层面呈拱形或平直分别组合或转变、构造类型、碳氧同位素组成及其组合,呈协调平行、不协调同向、不协调反向变化三类型若干亚类等,旋回性特征,确定了19个沉积旋回.根据δ13C平均值为-3.91 ‰PDB、δ18O为-6.97 ‰PDB分别为冷暖气候演变的临界(阀)值,δ13C或δ18O＞临界值者的偏重是冷,＜临界值的偏轻是热.以δ13C、δ18O组成(表1)和组合变化类型和上述旋回性特征,结合层面构造呈渐变过渡或突变,以及20个同位素年龄数据,初步认定荔波地区352 930～99 410年间沉积的19旋回,是一个较完整的冰期气候演化过程,属我国第四纪冰期系列的第五冰期,10旋回顶180 695年(推算)～15旋回顶129 890年,约5万多年是连续严寒的盛冰期,①、16分别可能是冰期早、晚时段相对温暖的间冰期.期间冷暖变化有5万年级的、10万年级的气候旋回.论证了荔波地区35～10万年间是冰期气候环境,前期17万年寒冷的气候环境,期间35万年、25万年前后更严寒,但生态基本保持正常演变的面貌,中期5万多年为极寒冷的气候环境,生态向适应冷气候环境演化,晚期3万多年为冷暖频繁突(跃)变的恶劣气候,期间生态面貌复杂,正常演替与残存、突变演替并存.     

弹性波正演模拟中PML吸收边界条件的改进

在弹性波有限差分正演模拟中, 完全匹配层(PML) 吸收边界条件是使用广泛、吸收效果最好的吸收边界条件.在目前的两种PML实现方法中, 分裂形式的完全匹配层(SPML) 方法计算存储量大、编程实现复杂; 非分裂形式的完全匹配层(NPML) 方法计算效率低、计算过程复杂.针对传统PML吸收边界条件在实现过程中存在的问题, 推导出了一种简洁有效的非卷积实现的NPML吸收边界条件, 既不需要对场分量进行分裂, 也不需要做复杂的卷积运算.分析结果表明, 本文实现的NPML吸收边界条件不仅具有良好的吸收衰减性能, 而且计算方程简单, 编程实现容易, 占有内存更小.      

Field characterization and data integration to define the hydraulic heterogeneity of a shallow granular aquifer at a sub-watershed scale

Providing a sound basis for aquifer management or remediation requires that hydrogeological investigations carried out to understand groundwater flow and contaminant transport be based on representative data that capture the heterogeneous spatial distribution of aquifer hydraulic properties. This paper describes a general workflow allowing the characterization of the heterogeneity of the hydraulic properties of granular aquifers at an intermediate scale of a few km². The workflow involves characterization and data integration steps that were applied on a 12-km² study area encompassing a decommissioned landfill emitting a leachate plume and its main surface water receptors. The sediments composing the aquifer were deposited in a littoral–sublittoral environment and show evidence of small-scale transitional heterogeneities. Cone penetrometer tests (CPT) combined with soil moisture and electrical resistivity (SMR) measurements were thus used to identify and characterize spatial heterogeneities in hydraulic properties over the study area. Site-specific statistical relationships were needed to infer hydrofacies units and to estimate hydraulic properties from high-resolution CPT/SMR soundings distributed all over the study area. A learning machine approach was used due to the complex statistical relationships between colocated hydraulic and CPT/SMR data covering the full range of aquifer materials. Application of this workflow allowed the identification of hydrofacies units and the estimation of horizontal hydraulic conductivity, vertical hydraulic conductivity and porosity over the study area. The paper describes and discusses data acquisition and integration methodologies that can be adapted to different field situations, while making the aquifer characterization process more time-efficient and less labor-intensive.     

胶东新城金矿床控矿构造变形环境：显微构造和EBSD组构约束

新城金矿床是典型的"焦家式"破碎带蚀变岩型金矿,矿体形态和规模都严格受到断裂破碎带控制,是探讨复杂构造-流体耦合成矿系统控矿构造变形环境研究的理想选区。断裂破碎带中构造岩既是构造变形行为的载体,也是相应变形环境的受体。论文在新城金矿详细露头构造解析的基础上,系统采集该矿床控矿断裂破碎带定向构造岩样品,进行显微构造和EBSD组构分析。研究区构造岩显微构造特征主要表现为韧性变形和脆性变形。韧性变形有波状消光、带状消光、亚晶粒、动态重结晶、核幔构造、丝带构造、碎(残)斑系、扭折带、变形纹、机械双晶、蠕英结构、云母鱼等;脆性变形有书斜构造和显微裂隙等。长石(残)斑系、扭折带、变形纹、蠕英结构和石英颗粒边界迁移动态重结晶、丝带构造等矿物变形特征表明断裂带成矿前以高温韧性变形为主;石英波状消光、亚晶粒、亚颗粒旋转和膨凸动态重结晶、方解石机械双晶、长石显微裂隙充填物等矿物变形反映成矿期兼有中低温韧性变形和脆性变形;压剪性穿晶裂隙则反映出成矿后主要是低温脆性变形。根据差应力、应变测量和EBSD组构分析,将新城金矿床控矿构造变形环境可以分为3个构造期:成矿前在NW-SE向挤压作用下发生韧-脆性左行剪切变形,600~700℃,差应力61.37~111.09MPa,应变测量轴比a/c为2.295~3.978,动态重结晶石英颗粒边界分维值为1.466~1.599,反映矿区为高温中高压高应变带变形环境,应变速率较大;成矿期为NW-SE向逐渐NEE-SWW向转变的挤压作用,发生压剪性脆性变形,200~500℃,差应力65.91~135.68MPa,应变测量轴比a/c为1.403~2.204,动态重结晶石英颗粒边界分维值为1.321~1.378,反映矿区成矿期为中低温中高压低应变带变形环境,反应速率较小;成矿后在NWW-SEE向挤压作用下发生压剪变形,150~300℃,反映低温低压脆性变形环境。     

汶川地震引发高速远程滑坡运动机理数值模拟研究——以谢家店子滑坡为例

针对汶川地震引发的谢家店子滑坡,在现场调查分析的基础上,建立了二维离散元数值模拟模型,采用2D-Block软件对其进行了全过程的数值模拟研究,并通过对跟踪块体的深入分析,研究了相应地质体在不同阶段下的运动特征。模拟结果表明,谢家店子滑坡经历了剧动启程抛掷阶段、快速撞击飞行阶段、铲刮减速碎屑流阶段及堆积掩埋阶段。为了揭示地震引发高速滑坡的发生规律,分别研究了地震震级、斜坡地形和斜坡上岩块的尺寸对高速滑坡启动和运动过程的影响规律。地震震级对边坡的启动、变形、破坏和运动有很大的影响,地震震级越大,滑体启动的加速度和速度也就越大,从而易形成高速远程滑坡。斜坡体本身的地形地貌对滑体运动也有较大影响。在震级和岩石力学参数一定的条件下,斜坡上岩块的大小对其启动、变形和运动过程有一定影响,随着岩块的增大,滑体运动的每个阶段历时都在减小,但当岩体十分破碎时,滑体虽然能够运动,但是很难发生抛掷。将地震滑坡的启动机理概括为积累变形效应、振荡启程效应和振荡加速效应。     

基于片上可编程系统的可控震源扫描信号研究与设计

在可控震源地震勘探中,不同的地质条件需要设置不同的激发参数,如何选择合适的激发参数并实现相应的扫描信号是必须关注的问题.在分析可控震源的线性扫描的起止频率、扫描长度、扫描斜坡函数和长度参数及伪随机扫描的阶次与载波频率对扫描信号质量的影响后,通过片上可编程系统设计了VSG硬件IP核与信号发生器系统,依据分析的信号选择原则实现了对应扫描信号的产生,达到扫描信号的技术指标.     

吉东火山岩型金矿地质特征及流体包裹体研究

通过对主要金矿床的流体包裹体 ,S、C、H和O同位素特征研究分析 ,认为金成矿的物化环境 :温度为 15 6～ 2 84℃、压力小于 6 6 0× 10 5Pa (深度不超过 2km) ;成矿流体具有富含H2 O、SO2 - 4、Cl- 和高K+的特点 ,是岩浆热液和大气降水的混合流体 ;成矿物质主要来源于火山 次火山岩     

赣东北铁砂街变质混杂岩块的同位素年代

赣东北南部的中浅变质岩一直被作为晚元古代地层,并称之为“铁砂街群”。本文根据同位素定年工作、结合野外地质调查和区域构造分析,认为“铁砂街群”不是地层单位,而是晚元古代形成的混杂岩。     

Mineralization time and tectonic setting of the Zhengguang Au deposit in the Duobaoshan ore field,Heilongjiang Province,NE China

The Zhengguang deposit, a representative large gold deposit in the Duobaoshan ore field in NE China, is located in the northeast of the Central Asian Orogenic Belt (CAOB). Ore body emplacement was structurally controlled and occurs mainly at the contact zone between the strata of Duobaoshan Formation and an Ordovician diorite stock. The diorite rocks have a close genetic relationship with Au mineralization. Re–Os isotope dating of Au-bearing pyrite yields an isochron age of 506 ± 44 Ma (MSWD = 15). Based on present and previous dating results, it can be concluded that the Zhengguang deposit formed at ~480 Ma. The mineralization time of the Zhengguang deposit is nearly identical to those of the Duobaoshan and Tongshan deposits, indicating they are all derived from the same metallogenic system. The Duobaoshan-style porphyry Cu–Mo mineralization may exist at deeper levels at Zhengguang. The geochemical characteristics of the Zhengguang dioritic rocks presented in this paper are similar to those of bajaitic high-Mg andesite, and the magmas originated from a mantle wedge metasomatized by melts from a subducting oceanic slab at an active continental margin setting. The Ordovician magmatic–metallogenic events in the Duobaoshan ore field were caused by the westward subduction of an oceanic slab located between the Xing’an and Songliao blocks. It is worth pointing out that the Zhengguang deposit is the oldest known Phanerozoic Au deposit in NE China. Further studies of this deposit will improve understanding of the regularity of ore formation and aid mineralization forecast across the Duobaoshan region.