甘肃侏罗纪植物化石Ginkgo huttonii角质层地球化学特征

对甘肃民和盆地侏罗纪植物化石Ginkgo huttonii(Sternb．)Heer的角质层与现生银杏Ginkgo biloba的角质层进行了地球化学特征对比分析,结果表明植物化石角质层有机物特征符合石油形成中沥青的演化特点。通过有机物组分含量分析,它们相当于中国中、新生代油源岩有机质类型中的腐泥型一腐殖腐泥型。对烃组分三角图进行投点,落入Ⅱ型干酪根范围内。通过有机质中的一些指标分析,发现Ginkgo huttonii的角质层处于低成熟阶段,与煤中显微组分角质体的成烃模式基本一致。另外,角质层的可溶有机质分布特征表明,植物化石角质层对陆相高蜡原油的形成有一定的作用,证明高等植物对蜡质有贡献。当前研究及古植物学资料表明,银杏是一种有利于煤成油的植物。     

Integrated method of RS and GPR for monitoring the changes in the soil moisture and groundwater environment due to underground coal mining

Mining affects the environment in different ways depending on the physical context in which the mining occurs. In mining areas with an arid environment, mining affects plants’ growth by changing the amount of available water. This paper discusses the effects of mining on two important determinants of plant growth—soil moisture and groundwater table (GWT)—which were investigated using an integrated approach involving a field sampling investigation with remote sensing (RS) and ground-penetrating radar (GPR). To calculate and map the distribution of soil moisture for a target area, we initially analyzed four models for regression analysis between soil moisture and apparent thermal inertia and finally selected a linear model for modeling the soil moisture at a depth 10 cm; the relative error of the modeled soil moisture was about 6.3% and correlation coefficient 0.7794. A comparison of mined and unmined areas based on the results of limited field sampling tests or RS monitoring of Landsat 5-thermatic mapping (TM) data indicated that soil moisture did not undergo remarkable changes following mining. This result indicates that mining does not have an effect on soil moisture in the Shendong coal mining area. The coverage of vegetation in 2005 was compared with that in 1995 by means of the normalized difference vegetation index (NDVI) deduced from TM data, and the results showed that the coverage of vegetation in Shendong coal mining area has improved greatly since 1995 because of policy input RMB￥0.4 per ton coal production by Shendong Coal Mining Company. The factor most affected by coal mining was GWT, which dropped from a depth of 35.41 m before mining to a depth of 43.38 m after mining at the Bulianta Coal Mine based on water well measurements. Ground-penetrating radar at frequencies of 25 and 50 MHz revealed that the deepest GWT was at about 43.4 m. There was a weak water linkage between the unsaturated zone and groundwater, and the decline of water table primarily resulted from the well pumping for mining safety rather than the movement of cracking strata. This result is in agreement with the measurements of the water wells. The roots of nine typical plants in the study area were investigated. Populus was found to have the deepest root system with a depth of about 26 m. Based on an assessment of plant growth demands and the effect of mining on environmental factors, we concluded that mining will have less of an effect on plant growth at those sites where the primary GWT depth before mining was deep enough to be unavailable to plants. If the primary GWT was available for plant growth before mining, especially to those plants with deeper roots, mining will have a significant effect on the growth of plants and the mechanism of this effect will include the loss of water to roots and damage to the root system.     

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日本MW 9.0级大地震前后华北和东北地区现今构造应力作用调整过程与研究意义探讨

为了探讨日本M_W 9.0级大地震前后华北和东北地区现今构造应力作用调整过程与研究意义,对华北和东北地区进行原位现今地应力绝对测量与实时监测、GPS测量,结果表明：日本大地震在山东半岛、华北北部地区和东北地区所诱发同震位移引起的张性效应调整周期分别约为6个月(即调整结束时间大约在2011年9月)、15个月(即调整结束时间大约在2012年6月)和26个月(即调整结束时间大约在2013年5月),张性效应调整周期与同震位移大小成正比。在这种调整过程中,往往表现出区域现今构造应力作用方式和构造应力场转换,并可能伴随重大地质事件(如地震等)的发生。2012年5月28日和29日、6月18日、8月26日及2013年1月11日在唐山及其周围地区分别发生的4.8级、3.2级、4.0级、3.3级和3.0级地震与华北北部地区构造应力作用方式和构造应力场转换有关,而2013年10月31日以来在吉林省松原市发生的地震群应与东北地区构造应力作用方式和构造应力场转换有关,而非一个大地震前的小震群。     

东昆仑东段香加南山花岗岩基中加鲁河中基性岩体形成时代、成因及其地质意义

东昆仑东段香加南山花岗岩基中加鲁河中基性岩体主要岩石类型包括角闪辉长岩和石英闪长岩。LA-ICP-MS锆石U-Pb同位素定年结果显示加鲁河中基性岩体的结晶年龄为220 Ma。岩体SiO_2含量较低,为47.91%~58.92%,Al_2O_3含量为15.54%~18.35%,Na2O为1.70%~3.34%,K_2O为0.58%~1.92%,Na_2O/K_2O比值为1.34~2.93,平均1.92,MgO含量为3.69%~8.24%,Mg~#为46~61,铝饱和指数A/CNK介于0.70~0.90之间,主体属于准铝质中钾钙碱性系列。岩体富集轻稀土元素,亏损重稀土元素,具明显的Eu负异常(δEu=0.40~0.59);微量元素富集Rb、Th、Ba等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE)。岩石学和地球化学研究显示岩体在地壳深部和浅部经历了两次岩浆混合作用。在深部,幔源岩浆底侵作用使下地壳部分熔融形成长英质岩浆,两种岩浆不同比例混合,经过化学扩散均一化,从而具有相似的同位素特征和岩石地球化学特征。在地壳浅部,经深部混合的岩浆注入花岗质岩浆,岩浆边部同花岗岩完全混合形成加鲁河岩体中石英闪长岩,不完全混合则形成暗色微粒包体。对加鲁河中基性岩体研究表明,东昆仑东段在晚三叠世处于古特提斯演化的后碰撞阶段,在这一时期存在岩浆底侵事件。     

天然次生林考虑伐后环境损失的多目标决策评价

山地森林采伐应注重经济、生态和社会效益的有机结合已成为共识.通过选取纯收益、土壤持水价值变化量、凋落物持水价值变化量、土壤养分价值变化量、凋落物养分价值变化量、固碳价值变化量和制氧价值变化量等7个效益指标,运用多目标决策分析方法,定量分析天然次生林5种不同强度(弱度13.0%、中度29.1%、强度45.8%、极强度67.1%和皆伐)采伐作业10 a后的经济和生态效益评价值以及它们的综合效益评价值.结果表明:随着采伐强度的增大,经济效益评价值增大,而生态效益评价值则下降,皆伐的经济效益评价值最大,为0.300,而其生态效益评价值最小,为0.070;弱度择伐的经济效益评价值最小,为0.030,而生态效益最大,为0.670;中度择伐的综合效益评价值最大,为0.713,皆伐的综合效益评价值最小,为0.370.因此,类似试验条件的林区应推行低强度(弱度或中度)择伐经营方式,以实现天然次生林可持续经营.     

东昆仑东段纳赤台岩群变火山岩锆石U-Pb年龄、地球化学特征及其构造意义

纳赤台岩群主要为一套变质火山沉积岩系,是东昆仑东段早古生代构造演化的重要物质记录。变火山岩的锆石U Pb年代学研究结果显示,年龄具有较宽的年龄谱（459～2 729 Ma）,可划分为2 559 Ma、1 341～1 472 Ma、918～1 142 Ma、557～595 Ma、459～497 Ma 5个年龄段,前4组为继承锆石年龄,反映研究区早期构造岩浆事件,459～497 Ma年龄谱段的锆石具有较好的生长韵律环带,为典型的岩浆成因锆石,206Pb/238U加权平均年龄为（474±7.9） Ma （MSWD=0.59,n=11）,代表纳赤台岩群变火山岩形成时代,即形成于奥陶纪。地球化学研究表明,纳赤台岩群变火山岩原岩均为玄武岩,可以划分为两个岩石系列,斜长角闪片岩和角闪片岩为亚碱性拉斑玄武岩。Mg#介于43.09～46.44,反映岩浆经历了一定程度的结晶分异演化;绿帘绿泥钠长片岩属于碱性玄武岩;Mg#介于57.20～76.00,相对接近原始岩浆成分。微量元素特征显示前者具有岛弧火山岩特征,而后者具有E MORB和OIB特征,其岩浆源区更富集。锆石U Pb年代学和地球化学研究表明,纳赤台岩群火山岩形成于早古生代弧后盆地,是原特提斯洋洋壳向北俯冲导致东昆仑地区拉张成弧后小洋盆的物质记录。     

The Impact of Climatic and Environmental Factors on n-Alkanes Indices in Southwestern Tibetan Plateau

n-Alkanes are widely used in paleoenvironmental reconstructions.However,our understanding of changes in the distribution of n-alkanes with climatic and environmental factors remains unclear in arid/semi-arid regions.We sampled 26 surface sediments from three climatic zones across the southwestern Tibetan Plateau to evaluate the sensitivity of chain length distributions of n-alkanes to climatic and environmental parameters.Our observations demonstrate that average chain length (ACL), proportion of aquatic macrophyte (Paq),carbon preference index (CPI) and ratio of the contents of nC27 and nC31 (nC27/nC31) are all sensitive to hydroclimatic conditions.In contrast to commonly-adopted assumptions,the correlations between these indices and hydrological parameters are not always good,which indicates that the interpretation of n-alkane indices is special on the southwestern Tibetan Plateau.These might be related to the vegetation characteristics and seasonality of biological activity,and need to be considered in paleoclimatic reconstruction.The impact of seasonal precipitation on n-alkanes indices was also evaluated.