近50年河南降水变化对水资源的影响

利用河南32个代表站1951～2002年降水量资料，分析了20世纪50年代以来全省年降水资源和水资源的变化趋势以及对旱涝灾害的影响。结果表明，自20世纪80年代中期以来，河南已进入一个降水量偏少时期，干旱化程度加重，水资源短缺已成为影响工农业生产和国民经济发展的主要因素。     

大兴安岭成矿带北段区域地球化学背景与成矿带划分

大兴安岭成矿带是中国最重要的有色金属成矿带之一,资源潜力巨大,其北段是中国除新疆以外唯一存在地质空白的地区,矿产勘查与研究程度低。笔者通过对其区域地球化学场特征、大中型内生金属矿床分布规律、区域控矿地质条件的研究,初步认为本区优势内生金属矿产是钼矿、银铅锌矿,其次是金矿和铜矿,潜力矿种是铀矿;以德尔布干、鄂伦春-伊尔施两条深断裂为界,其两侧地球化学背景、成矿环境、矿种及成矿类型差异很大,并将大兴安岭成矿带北段划分为：德尔布干Ⅲ1、大兴安岭西坡Ⅲ2、嫩江Ⅲ3等3个Ⅲ级成矿亚带10个Ⅳ级成矿区。     

锡在高温气相里的迁移实验与南岭大厂 矿区100号矿体形成机制

我国著名大型锡矿大厂矿区的100号矿体是一个不规则的大脉状矿体,由质密锡铅锌矿石组成。该大脉矿体长度约1200多米。大厂矿区矿床形成过程有两个主要矿化阶段:早期锡石硫化物阶段和晚期的硫盐锡石多金属矿化阶段。矿物流体包体数据表明:早期形成于300~400℃(450℃)条件下,有高盐度流体包体与低盐度流体包体共存,流体处于从超临界流体进入近临界的气液两相不混溶区过渡阶段,有流体沸腾现象;晚期流体盐度变化小处于降温过程。而100号矿体形成于300~360℃,压力较低,仅为8.24MPa。本次研究设计一含锡溶液从超临界态进入亚临界态的气液不混溶区的实验,研究金属在气-液间再分配过程。实验模拟一个非平衡的气液分离反应动力学过程。重点研究含Sn-NaHCO3-HCl-H2O在近临界压(25~22MPa)和8~14MPa、380~300℃条件下,在亚临界态气-液两相不混溶区时相分离过程。气液分离实验是恒压降温过程。结果表明:近临界区NaHCO3-HCl-H2O的NaCl-H2O体系出现气-液(L-V)分离现象。降温远离临界点时,在V与L相里的Na、Cl浓度比:Na(V/L)、Cl(V/L)比值多数远小于1,Na、Cl主要分布在液相里。实验表明出现含Sn溶液的V-L两相分离过程,并且,Sn已在L-V间再分配,Sn(V/L)多数大于1。说明Sn多数情况下分布于气相里(贫NaCl富H2OCO2)。在380~250℃范围内NaCl-H2O-CO2体系包含的H2O-CO2体系也出现V-L两相不混溶区。实验发现H2O-CO2的L-V分离过程中,气相里HCO-3和CO2-3分布很少,CO2多。同时,锡在H2O-CO2的L-V间也存在再分配,锡分布在富CO2气体里。实验说明富CO2气体迁移锡。实验为地质解释提供依据,说明100号矿体形成于快速减压的大型裂隙条件下。在300~360℃下压力减低,使含金属流体迅速进入L-V两相不混溶区,气体快速迁移金属,快速沉积金属矿石。     

Factors Controlling Precipitation of Barite and Witherite and Genesis of the Ankang–Xunyang Barium Deposits, Shaanxi, China

The barium deposits in Ankang and Xunyang counties,Shaanxi Province,China,occur in the northernmost part of the world-class barium metallogenic belt in south Qinling.The deposits are hosted by the Lower Silurian carbonaceous siliceous rocks,with a unique combination of barite and witherite.The homogenization temperatures of fluid inclusions in the barite are mainly concentrated between 135 and 155 ℃,whereas those from the witherite have two peaks of 165-175 ℃,and 215-225℃,respectively.Laser Raman analysis of fluid inclusions indicates that the vapor phase of fluid inclusions in barite is dominated by H_2O,although some contains N_2,H_2S,and CH_4.The compositions of the vapor and liquid phases of fluid inclusions in witherite can be divided into two end-members,one dominated by H_2O without other volatiles,and the other containing CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6 in addition to H_2O.CO_2,H_2S,and some CH_4 are interpreted as products of chemical reactions during mineralization.Organic gases(CH_4,C_2H_6,C_3H_8,C_2H_4,and C_6H_6) in the fluids were critical in the formation of barium sulfate versus carbonate.The δ~(34)S values of barite range from 38.26‰ to54.23‰(CDT),the δ~(34)S values of sulfides coexisting with barium minerals vary from 22.44‰ to25.11‰(CDT),and those in the wall rock from 11.60‰ to 19.06‰(CDT).We propose that the SO_4~(2-)generally experienced bacterial sulfate reduction in seawater before mineralization,and some SO_4~(2-)also experienced thermochemical sulfate reduction in hydrothermal system during mineralization.The δ~(13)C values of witherite range from-27.30‰ to-11.80‰(PDB),suggesting that carbon was sourced from organic substances(like CH_4,C_2H_4,and C_2H_6).The formation of witherite was possibly associated with thermochemical sulfate reduction,which caused the consumption of the organic gases and SO_4~(2-) in the hydrothermal solutions,consequently inhibiting barite formation.The important conditions for forming witherite include high fluid temperatures,high Ba~(2+) concentrations,CO_2 in the fluids,low HS~- concentrations,and the subsequent rapid diffusion of H_2S during thermochemical sulfate reduction of the fluids.     

青藏高原羌塘盆地早侏罗世晚期海螂蛤页岩及其年代地层学意义

发现于德国南部的早侏罗世土亚辛期的海螂蛤页岩相沉积是中生代最早一次,也是唯一保存在大陆地层中的全球性大洋缺氧事件的典型代表。近年中国羌塘盆地已相继发现4处海螂蛤页岩相地层。北羌塘天然气水合物钻探试验井QK-5井钻遇含海螂蛤页岩相特有化石组合的地层,厚度逾150m,是迄今所知羌塘盆地纬度最高的海螂蛤页岩相产地,其他3处分布在羌塘盆地中间隆起带以南的双湖和色哇等地。海螂蛤页岩相的分布纵贯南、北羌塘,意味着羌塘盆地在早侏罗世并没有受到中间隆起带的制约而分成南、北2个独立的沉积凹陷。北羌塘西部白龙冰河、半岛湖一带与东部雀莫措、雁石坪一带的早侏罗世沉积相截然不同,形成早侏罗世西海东陆的沉积格局。海螂蛤页岩相在羌塘盆地的发现,有助于进一步认识中生代羌塘盆地沉积和古海洋演化历史。该区以海螂蛤黑色页岩为代表的富碳沉积无论是分布面积还是沉积厚度都十分可观,对盆地的天然气水合物、页岩气及常规油气勘探具有重要的意义。     

Geochemical Characteristics of Eolian Deposits in the Chengdu Plain of Sichuan Province and the Implications for Provenance

In this study Chengdu Red Earth （CRE） from the Chengdu Plain （CP）,Sichuan province,was analyzed for its elemental （major and trace elements） and isotopic （Sm-Nd） geochemistry and compared with Pleistocene loess and paleosol samples from the Chinese Loess Plateau （CLP） in Northern China.The geochemical composition of CRE is similar to north China loess,and also resembles the average UCC.This indicates that CRE,as loess deposits in Northern China,was derived from well-mixed sedimentary protoliths that have undergone numerous upper crustal recycling processes.However,obvious differences in the geochemical characteristics of CRE and the north China loess are also revealed in our results.For chemically stable elements,CRE has higher Ti,Zr,Hf and lower ΣREE,Ba contents in comparison with loess samples from the CLP.Further analysis shows that CRE has higher TiO2/Al2O3,SiO2/Al2O3,Ba/Rb and lower Ce/Yb,Eu/Yb,LaN/YbN and ΣLREE/ ΣHREE ratios.In Sm-Nd isotopic geochemistry,Sm and Nd content and the εNd（0） value in CRE are significantly higher than those in north China loess.The higher TiO2 content in CRE coincided with a high background concentration of Ti in the Sichuan Basin and the surrounding regions.The lower ΣREE and higher Sm,Nd,εNd（0） values are related to the wide distribution of basalt in the southwest Sichuan Basin.The elemental and isotopic geochemistry of CRE indicates that eolian materials in the CP predominantly come from the Sichuan Basin and the surrounding regions,which differs from loess deposits in the CLP.     

硬岩型铀矿化(点、带)地球物理特征

为了深入研究硬岩型铀矿化(点、带)的地球物理特征,在桃山、红山子地区开展了综合物探测量.结果表明,在△T磁异常平面等值线图中,铀矿床(点、带)一般位于强弱磁异常过渡地带偏弱磁异常一侧,电阻率断面图中多位于高低阻梯度变化带或中低阻区,电阻率平面图中多位于中低阻过渡带偏低阻一侧.该硬岩型铀矿化地球物理特征为寻找该类铀矿有利地段提供了重要信息.     

黄淮海流域旱涝时空分布及组合特性

以黄淮海流域及其周边地区204个气象站点1961-2010年逐日降水过程资料、国家1:25万DEM数据和1:20万土地利用数据为基础,在利用降水Z指数对黄淮海流域旱涝进行评价的基础上,采用下垫面数据对结果进行修正,并分析黄淮海流域旱涝面积的时间变化特征,对黄淮海地区的易旱区、易涝区进行了划分,进一步选取集对分析法划分了流域内季节间旱涝交替的易发区。结果表明:黄淮海流域内夏秋两季旱涝问题较为严重,且秋旱面积上升趋势较为明显;黄河和海河流域以干旱居多,淮河则是干旱和雨涝并存,季节间的旱涝交替多集中在淮河流域中上游地区。     

洪水管理经济评价研究进展

洪水管理经济评价是践行洪水管理治水方略必不可少的环节。从洪水管理经济评价理论、洪灾损失评估以及洪水管理成本效益评估等方面综述了洪水管理经济评价的主要研究进展,分析了目前研究存在的不足,指出现有的防洪经济理论与方法已难以满足洪水管理决策对经济评价的要求。强调建立完善的洪水管理经济评价理论体系,扩展评价内容和范围,深入开展非工程措施效益、生态环境影响和社会公平等评价方法的研究是中国今后洪水管理经济评价研究的重点。