宁夏地表湿润状况及极端干湿事件演变规律

利用宁夏1961—2004年月平均气温、月降水量资料,计算了地表湿润指数,以此为基础对宁夏地表湿润状况及极端干湿事件的分布特征进行了较为深入的研究。结果表明:近40多年来,宁夏大致经历了冷湿期、冷干期、暖干期;自20世纪60年代以来,宁夏年极端干旱频率有增加的趋势,极端湿年高频区逐渐缩小; 80年代以来,宁夏极端干旱年事件高频区明显扩大;不同气候型态下,极端干湿事件频率具有明显差异,冷干期极端干旱事件最多,极端湿润事件最少,冷湿期极端干旱频率最小,极端湿润频率最大。     

内蒙古自治区东部荒漠化现状及危害

依据1994年《国际防治荒漠化公约》的荒漠化定义,对内蒙古自治区东部的荒漠化现状进行了调查与划分,对荒漠化的分布特征及危害类型进行了论述.内蒙古自治区东部存在沙质荒漠化、土壤盐渍化及水蚀荒漠化3种类型.现有荒漠化土地面积148521.65km²,占调查区总面积的54.76%.荒漠化的发展,造成内蒙古东部草原退化、诱发沙尘暴、地下水位下降等环境地质问题.     

赣北燕山期火山-次火山-斑岩金矿床成矿系列及地质特征

燕山期火山-次火山-浅成斑岩金矿成矿系列构成了赣北地区一个重要的金矿成矿系列.根据其金矿成矿物质来源、成矿作用及产出的围岩条件可划分为火山热液型、次火山-浅成斑岩热液型和隐爆角砾岩型金矿床.对上述3种主要金矿床地质特征、找矿标志进行了较为详细的描述,同时对赣北地区该金矿成矿系列进一步找矿方向进行了论述,旨在加强和推动赣北地区金矿地质勘查工作.     

黑龙江省达连河油页岩地球化学特征及成因探讨

论述了达连河含煤段油页岩及油页岩段油页岩的地球化学特征,探讨了两套油页岩成因。这两套油页岩地球化学性质有很多相似之处,主要表现为油页岩都属于中熔或难熔的硅质灰分,SiO₂、Al₂O₃及Fe₂O₃含量很高;无机元素 Mn/Ti小于0.1,Sr/Ba为0.1～0.5,V/Ni为2.6～7.0;有机质类型以腐泥腐殖型为主,正构烷烃OEP值为1.55～3.67,具奇碳数优势,主峰碳为nC₂₃和C₂₉,Pr/Ph比值平均高达2.30,具强烈的姥鲛烷优势,Pr/nC₁₇比值为1.18～3.20,说明这两套油页岩都形成于淡水、近岸及弱氧化-弱还原的湖沼相沉积环境。但含煤段油页岩沉积时期高温、湿润的古气候条件下的喜湿植物面貌,使油页岩母质类型具有较多的富氢组分,这是造成两套油页岩品质差异的主要原因。     

运用铀同位素研究砂岩型铀矿的几个问题

通过砂岩铀矿矿卷前锋铀同位素特征和512矿床含矿层铀同位素特征的研究,对砂岩型铀矿形成过程、铀同位素找矿标志进行了讨论。研究结果表明,砂岩铀矿的形成是一个多期次、滚动式、由氧化向还原环境推进的动态成矿过程,矿体主要定位于Ⅲ区段。根据铀同位素样品在不同氧化还原分带中的分布和矿体的滚动性特征,认为A区定名为地球化学矛盾区更为恰当。     

兰州南北两山绿化区植物与植被类型初查

通过对兰州南北两山环境绿化工程区进行植物、植被类型调查,结果表明：该项目区内植物资源相对丰富,有植物185种,分属于56科;区内植物生长状况良好,植物群落趋向多元化,且稳定性增加;按照植物群落学—生态学原则,并参考中国植被分类系统,将工程区内植被类型划分为９种类型,即 2种天然植被类型和7种人工植被类型。根据当前所造林分多为结构单一的纯林的现状,认为今后在南北两山进行植树造林应考虑营造混交林,以提高林分稳定性和抵御病虫害的能力,并积极采用人工措施促进森林更新。     

CCD‐Δa and BV R photometry of NGC 7296

The first CCD photometric investigation of the open cluster NGC 7296 up to now was performed within the narrow band Δa photometric system, which enables us to detect peculiar objects. A deeper investigation of that cluster followed, using the standard BV R ‐Bessel filter set. The age and E (B – V ) was determined independently to log t = 8.0 ± 0.1 and 0.15 ± 0.02, respectively by using Δa and broadband photometry. In total five Be/Ae objects and two metal‐weak stars showing significant negative Δa ‐values as well as one classical chemically peculiar star could be identified within that intermediate age open cluster. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

New brown dwarf companions to dM(e) stars

We present new astrometric and spectroscopic data to confirm two new M/L dwarf systems, G124‐62 and LHS5166, and discuss the nature of a third system (LP261‐75). Age and thus mass determinations of the L dwarf companions are discussed based on various activity‐age relationships of the M dwarf primaries. This publication will update the list of widely separated substellar companions to nearby stars. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of thermal maturity and organic matter type by principal components analysis of the distributions of polycyclic aromatic compounds

The thermal maturity and organofacies sensitivity of polycyclic aromatic compound (PAC) distributions was explored by examination of the aromatic fractions of solvent extracts from a diverse set of 53 shales, coals and kerogen macerals which have undergone either natural or artificial maturation and which represent all three principal sedimentary organic matter (OM) types. Systematic changes with maturation were observed in the following groups of isomers: tri- and tetramethylnaphthalenes, methyl- and dimethylphenanthrenes, methyl- and dimethyldibenzothiophenes, methylpyrenes, and methylchrysenes. The maturity differences were quantified by mathematical ratios of the relative concentrations of the more thermally stable isomers to the less stable, on the basis of theoretical considerations and empirical observations. The PAC maturity parameters, unlike those derived from saturated biomarker stereoisomers, are typically effective across the entire oil generation window. To compensate for the effects of OM type on the maturity parameters, they were combined using principal components analysis. The resulting first principal component was in good agreement with independent indicators of maturity. The relative distributions of C₀–C₃ alkylphenanthrenes, dibenzothiophene, methyldibenzothiophenes and methyldibenzofurans were evaluated by a separate principal components analysis. The results permitted an independent grouping of the samples by OM type and suggested additional, simple molecular ratios that allow graphical recognition of OM type, including the ratio of dibenzothiophenes to dibenzofurans and a ratio using C₂-alkylphenanthrene isomers.     

长江中下游地区硫铁矿成矿规律及前景探讨

长江中下游地区是我国重要的硫铁矿产地之一 ,已探明的 47个矿床主要集中分布在宁芜、庐枞、铜陵、宁镇等 7个成矿区内。主要矿床可划分为 4种成矿类型 ,即陆相火山型、夕卡岩型、斑岩型及热液型。通过对硫铁矿成矿地质条件分析认为 ,陆相火山型、夕卡岩型硫铁矿床成矿规模大、分布集中 ,为今后找矿的主攻类型。在铜陵、宁芜、庐枞 3个成矿区可分别圈定出找矿有利地段。