基于GIS的滑坡、泥石流灾害危险性区划关键问题研究

随着GIS技术的引入,滑坡、泥石流灾害危险性区划的效率和准确性得以大大提高。依据工程地质类比原则,在灾害学理论指导下,结合专家打分、层次分析、人工神经网络、信息量、Logistic回归、统计量等模型方法,以MAPGIS软件为平台,利用C++语言开发了滑坡、泥石流灾害危险性区划评价分析系统;并重点探讨了GIS支持下的滑坡、泥石流灾害危险性区划过程中的因子分析、模型选取、模型复合、单元划分、系统集成、结果评价等关键问题,建立了一整套基于GIS的滑坡、泥石流灾害评价方法体系。应用该系统对长江三峡库区和辽宁省鞍山市分别开展了滑坡、泥石流灾害危险性区划研究,取得了较好的效果。     

辽北－吉南地区太古宙花岗岩－绿岩带地质地球化学

辽北－吉南地区是我国典型太古宙花岗岩－绿岩带出露区之一。根据其地质地球化学特征，本区绿岩带可划分为清原型和夹皮沟型，其形成的古构造环境分别为与现代岛弧的大陆边缘活动带和弧后盆地或大陆边缘裂谷相类似的裂谷型构造环境。与绿岩带有关的花岗质岩石可划分为三类：即片麻状花岗质杂岩体、花岗闪长岩和英云闪长岩底辟岩基以及钾质花岗岩。花岗岩－绿岩带的形成时代为２．５－２．９Ｇａ。     

Geology and Metallogenesis of the Sawayaerdun Gold Deposit in the Southwestern Tianshan Mountains, Xinjiang, China

The Sawayaerdun gold deposit, located in Wuqia County, Southwest Tianshan, China, occurs in Upper Silurian and Lower Devonian low‐grade metamorphic carbonaceous turbidites. The orebodies are controlled by a series of NE‐NNE‐trending, brittle–ductile shear zones. Twenty‐four gold mineralized zones have been recognized in the Sawayaerdun ore deposit. Among these, the up to 4‐km‐long and 200‐m wide No. IV mineralized zone is economically the most important. The average gold grade is 1–6 g/t. Gold reserves of the Sawayaerdun deposit have been identified at approximately 37 tonnes and an inferred resource of 123 tonnes. Hydrothermal alteration is characterized by silicification, pyritization, arsenopyritization, sericitization, carbonatization and chloritization. On the basis of field evidence and petrographic analysis, five stages of vein emplacement and hydrothermal mineralization can be distinguished: stage 1, early quartz stage, characterized by the occurrence of quartz veins; stage 2, arsenopyrite–pyrite–quartz stage, characterized by the formation of auriferous quartz veinlets and stockworks; stage 3, polymetallic sulfide quartz stage, characterized by the presence of auriferous polymetallic sulfide quartz veinlets and stockworks; stage 4, antimony–quartz stage, characterized by the formation of stibnite–jamesonite quartz veins; and stage 5, quartz–carbonate vein stage. Stages 2 and 3 represent the main gold mineralization, with stage 4 representing a major antimony mineralization episode in the Sawayaerdun deposit. Two types of fluid inclusion, namely H₂O–NaCl and H₂O–CO₂–NaCl types, have been recognized in quartz and calcite. Aqueous inclusions show a wide range of homogenization temperatures from 125 to 340°C, and can be correlated with the mineralization stage during which the inclusions formed. Similarly, salinities and densities of these fluids range for each stage of mineralization from 2.57 to 22 equivalent wt% NaCl and 0.76 to 1.05 g/cm³, respectively. The ore‐forming fluids thus are representative of a medium‐ to low‐temperature, low‐ to medium‐salinity H₂O–NaCl–CO₂–CH₄–N₂ system. The δ³⁴S_CDT values of sulfides associated with mineralization fall into a narrow range of ?3.0 to +2.6‰ with a mean of +0.1‰. The δ¹³C_PDB values of dolomite and siderite from the Sawayaerdun gold deposit range from ?5.4 to ?0.6‰, possibly reflecting derivation of the carbonate carbon from a mixed magmatic/sedimentary source. Changes in physico‐chemical conditions and composition of the hydrothermal fluids, water–rock exchange and immiscibility of hydrothermal fluids are inferred to have played important roles in the ore‐forming process of the Sawayaerdun gold–antimony deposit.     

Geochronology,geochemistry and Hf isotopes of andesites in the Sandaowanzi gold deposit (Great Xing'an Range,NE China): implications for petrogenesis,tectonic setting,and mineralization

Acta Geochimica - The Sandaowanzi gold deposit is an extremely Au-rich deposit in the Northern Great Hinggan Range in recent years. Zircon U–Pb geochronology, Hf isotope analysis, and the...     

基于扩展有限元分析的页岩水力压裂裂缝扩展规律探究

水力压裂是开采地下页岩气资源的有效技术手段,探究页岩水力压裂裂缝的扩展规律,可为页岩气的高效开采提供科学的指导依据。通过运用大型有限元软件ABAQUS中的扩展有限元模块,针对不同地应力差工况条件下均质页岩中初始裂缝的位置、方位角、数量和含层理页岩中层理的构造方向、内部倾角、岩性对水力裂缝扩展的影响进行探究。结果表明：对于垂向扩展的水力裂缝,水平主应力增大使裂缝更不易扩展,裂缝扩展长度减小、起裂压力增大;在注液体积流量相同时,向初始裂缝两端同时起裂所形成的水力裂缝长度大于仅向一侧起裂;当初始裂缝处于页岩中部且呈45°方向时,裂缝会向最大水平主应力方向偏转,且偏转程度随最大水平主应力的增大而增大;分时多簇压裂时,裂缝间的扩展会相互干扰,且会较大地影响裂缝扩展的形态和起裂压力,但对裂缝注液点裂缝宽度的影响较小;对于含水平和竖直构造层理的页岩,改变层理内部倾角,水力裂缝会出现不同程度偏转,且其偏转程度随着层理内部倾角的增大而减小;对于含45°方向构造层理的页岩,水力裂缝在层理分别为砂岩、煤岩和泥岩中的偏转程度依次增大,且裂缝偏移比随着最大水平主应力的增大而增大。     

祁连山多年冻土区甲烷通量与甲烷微生物群落组成的关系

全球变暖可能导致多年冻土中的有机碳分解,向大气释放甲烷(CH4),但多年冻土的甲烷释放通量与微生物群落结构以及功能基因的丰度相关性还不清楚.于2019年6月～2020年1月,选择青藏高原北部祁连山多年冻土区,利用静态箱-气相色谱法对不同海拔地区进行CH4释放通量测定,并分析土壤理化性质、CH4功能微生物群落、功能微生物...     

受污染湖泊沉积物中氮素转化对有机污染物降解的促进效应与机制

目前有关硝化反应动力学及其共代谢降解有机污染物的研究多为实验室微生物纯培养体系,来源于野外环境样品的很少.以受污染湖泊严家湖1号塘沉积物为研究对象,野外钻探采样,并选取不同深度沉积物进行室内外加氮源的硝化实验.结果表明:表层土和钻井一处50～100 cm沉积物发生明显的硝化反应,同时有机污染物中六氯苯含量降低最多,分别...     

Chronology and cooling history of the Tianmenshan pluton in South Jiangxi Province and their geological significance

Geochronological studies on the crust-derived Tianmenshan pluton were undertaken by SHRIMP zircon U-Pb dating and Ar-Ar dating of biotite, muscovite and K-feldspar, giving a petrogenetic age of 167 Ma. Owing to the closure systems in different minerals, the cooling history of the pluton can be determined with an age-temperature diagram. The late hydrothermal event has been recognized, which is related probably with mineralization. In terms of the comparative geochronological and petrologic records, it is concluded that there are some constrains on tectonic evolution and that the formation of the Tianmenshan pluton proceeded in a transition period from Indosinian post-orogeny extension to strong compressive tectonics. And the timing of the hydrothermal event matches the compressive climax of the Yanshanian orogeny. The temporal gap between granite emplacement and wolframite mineralization could last 10-20 Ma owing to the low cooling rate of the pluton.     

江苏固城湖流域1951-2000年农业非点源氮、磷输移的数值模拟研究

选择位于长江下游的固城湖流域作为研究区域,基于分布式流域水文模型SWAT,采用数值模拟的手段,反演了1951～2000年流域农业非点源氮、磷的输移规律。模拟结果与实测值的一致性反映了模型的良好模拟能力。比较两个时段的模拟结果发现,1981～2000年,流域农业非点源氮、磷年平均浓度和输移量分别为:总氮0.82mg/L和411.88×103kg/a,总磷0.084mg/L和43.04×103kg/a;远高于1951～1960年的氮、磷年平均浓度和输移量分别为:总氮0.22mg/L和49.55×103kg/a,总磷0.036mg/L和7.67×103kg/a。模拟主要反映了流域下垫面条件和农作物耕作模式对农业非点源氮、磷浓度及输移量的影响。