辽东三家子地区晚侏罗世花岗岩SHRIMP U-Pb年龄、Hf同位素特征及地质意义     

杨凤超  宋运红  郝立波  柴鹏 《地质学报》2015,89(10):1773-1782

辽东岫岩三家子矿化集中区位于青城子矿化集中区以西三家子一带,属于青城子矿化带西延部分。矿区内发育以洼岭二长花岗岩为代表的晚侏罗世侵入岩,应与本地区矿化作用有密切的关系。岩体锆石SHRIMP U-Pb年龄加权平均值为162.4±1.9Ma,代表岩浆结晶年龄,应为燕山期岩浆活动产物,是华北东部侏罗世花岗岩的一部分。全岩岩石化学分析结果显示,洼岭二长花岗岩为高钾钙碱性岩浆系列,其中SiO2(72.28%~75.61%)≥56%,Al2O3(14.37%~15.06%)≥15%(极少数低于此值),MgO小于3%制,A/CNK值1.035~1.083,均大于1,具有铝过饱和型特征。微量元素数据显示亏损重稀土元素,(La/Yb)N为18.06~22.66,Eu无负异常。具有高Sr(497×10-6~574×10-6),低Y(4.56×10-6~5.61×10-6)和Yb(0.47×10-6~0.62×10-6)特征,表现为具有埃达克质亲和性的I型花岗岩。岩体εHf(0)为负值,εHf(t)为负值(-28.9~-17.5),说明洼岭岩体形成时壳源物质成分占主导地位,单阶段Hf模式年龄(TDM)平均为1714Ma,两阶段Hf模式年龄(TDMC)平均为3704Ma。综上,洼岭岩体可能形成于从中侏罗世(160Ma)开始的多板块向东亚汇聚的构造背景,可能为加厚下地壳熔融的产物,同时是埃达克岩与铜成矿有密切关系的又一佐证。  相似文献   

Evaluation of the petroleum composition and quality with increasing thermal maturity as simulated by hydrous pyrolysis: A case study using a Brazilian source rock with Type I kerogen     

《Organic Geochemistry》2015

Hydrous pyrolysis (HP) experiments were used to investigate the petroleum composition and quality of petroleum generated from a Brazilian lacustrine source rock containing Type I kerogen with increasing thermal maturity. The tested sample was of Aptian age from the Araripe Basin (NE-Brazil). The temperatures (280–360 °C) and times (12–132 h) employed in the experiments simulated petroleum generation and expulsion (i.e., oil window) prior to secondary gas generation from the cracking of oil. Results show that similar to other oil prone source rocks, kerogen initially decomposes in part to a polar rich bitumen, which decomposes in part to hydrocarbon rich oil. These two overall reactions overlap with one another and have been recognized in oil shale retorting and natural petroleum generation. During bitumen decomposition to oil, some of the bitumen is converted to pyrobitumen, which results in an increase in the apparent kerogen (i.e., insoluble carbon) content with increasing maturation.The petroleum composition and its quality (i.e., API gravity, gas/oil ratio, C₁₅₊ fractions, alkane distribution, and sulfur content) are affected by thermal maturation within the oil window. API gravity, C₁₅₊ fractions and gas/oil ratios generated by HP are similar to those of natural petroleum considered to be sourced from similar Brazilian lacustrine source rocks with Type I kerogen of Lower Cretaceous age. API gravity of the HP expelled oils shows a complex relationship with increasing thermal maturation that is most influenced by the expulsion of asphaltenes. C₁₅₊ fractions (i.e., saturates, aromatics, resins and asphaltenes) show that expelled oils and bitumen are compositionally separate organic phases with no overlap in composition. Gas/oil ratios (GOR) initially decrease from 508–131 m³/m³ during bitumen generation and remain essentially constant (81–84 m³/m³) to the end of oil generation. This constancy in GOR is different from the continuous increase through the oil window observed in anhydrous pyrolysis experiments. Alkane distributions of the HP expelled oils are similar to those of natural crude oils considered to be sourced from similar Brazilian lacustrine source rocks with Type I kerogen of Lower Cretaceous age. Isoprenoid and n-alkane ratios (i.e., pristane/n-C₁₇ and phytane/n-C₁₈) decrease with increasing thermal maturity as observed in natural crude oils. Pristane/phytane ratios remain constant with increasing thermal maturity through the oil window, with ratios being slightly higher in the expelled oils relative to those in the bitumen. Generated hydrocarbon gases are similar to natural gases associated with crude oils considered to be sourced from similar Brazilian lacustrine source rocks with Type I kerogen of Lower Cretaceous, with the exception of elevated ethane contents. The general overall agreement in composition of natural and hydrous pyrolysis petroleum of lacustrine source rocks observed in this study supports the utility of HP to better characterize petroleum systems and the effects of maturation and expulsion on petroleum composition and quality.  相似文献   

大兴安岭北段雅尔根楚I型花岗岩年代学、岩石地球化学及其地球动力学意义   总被引：3，自引：0，他引：3  

徐久磊  郑常青  施璐  李娟  崔芳华  高源  张行行  高峰 《地质学报》2013,87(9):1311-1323

对内蒙古大兴安岭北段雅尔根楚花岗岩岩体岩相学研究表明,该花岗岩岩体主要岩性组合为正长花岗岩和花岗质糜棱岩,应用锆石U-Pb LA-ICP-MS测年方法,测得的3组年龄为226.8±2.2Ma、230.2±1.3Ma和233.6±1.5Ma,表明其岩体侵位时代为晚三叠世.岩石主量元素(XRF)具有富硅、富钾的特征,A/CNK值为0.81～1.10,显示铝弱饱和,相对富集轻稀土元素、亏损重稀土元素,具有Eu负异常,微量元素相对富集大离子亲石元素,亏损高场强元素,显示岛弧性质的花岗岩特征,微量元素特征显示其为Ⅰ型花岗岩.经过综合研究认为该Ⅰ型花岗岩可能是在整个伸展环境下,岩石圈地幔压力降低导致地幔上涌,残余的洋壳熔融提供流体注入,从而该岩体发生侵位.  相似文献   

Entropy analysis for identifying significant parameters for seismic soil liquefaction     

Asita N. Dalvi  Snehal R. Pathak  Neela R. Rajhans 《Geomechanics and Geoengineering》2014,9(1):1-8

A novel application of multi-criteria decision making (MCDM) technique to seismic soil liquefaction, a complex problem in earthquake geotechnical engineering, is presented. Seismic soil liquefaction depends on a diversified set of physical parameters with highly non-linear interconnections. Factors governing liquefaction may broadly be grouped as seismic parameters, site conditions and primarily dynamic soil properties, as the stimulus itself is manifestly dynamic. Each of these factors incorporates a wide range of variety of parameters that characterize liquefaction, to a varying degree of significance, such as: the magnitude, effective overburden pressure, shear modulus, normalized standard penetration blow count [N₁]₆₀, etc. Estimating rapid, yet accurate and reliable liquefaction susceptibility requires identification of the most significant factors controlling liquefaction. Thus a new concept of extracting significant parameters and gauging their importance is carried out by assigning them weights by applying MCDM introduced herein, whose evaluation is accomplished by means of an ‘entropy method’. In line with this, a relative reliability risk index (R³I) is computed indicating the ranking that directly reflects the severity of risk for liquefaction. Although the entropy analysis is carried out separately for the three multivariate criteria, it is remarkable that the R³I evaluated for each of these gives consistent ranking.  相似文献   

北京市生态保护红线内地表覆盖变化聚集性研究     

张译  陈品祥  刘宇  余永欣  武润泽  许天豪  杨旭东  龚芸 《测绘通报》2022,(3):13-17+22

本文利用北京市2015、2017及2019年三期地理国情普查及监测数据,分析了北京市生态保护红线内地表覆盖空间变化特征,并在全局及局部Moran's I空间自相关分析的基础上,从空间上对生态保护红线内生态修复显著、生态破坏显著区域进行识别。研究结果表明,2015-2019年,生态保护红线内的生态用地整体处于流出状态,且各类变化斑块间存在明显的空间自相关效应,15个区域为人类活动密集区,其中雾灵山及周边山区、松山及玉渡山保护区、南海子公园、密云水库、怀沙怀九河、泃河平谷段(西南段)等6个地区为生态破坏显著区域,建议对其加大监管力度;生态修复显著区域为京密引水渠密云段,其他8个区域均为人为破坏及修复活动共存区域。本文为严守生态保护红线,加快建设美丽北京及生态文明建设提供决策依据,同时也适用于全国其他地区生态保护红线内地表覆盖变化的监测。  相似文献   

1980—2018年中国极端高温事件时空格局演变特征     

杨阳  赵娜  岳天祥 《地理科学》2022,42(3):536-547

基于全国2 419个气象站1980—2018年逐日气象观测资料,利用Mann-Kendall突变检验、滑动t检验、空间自相关及标准差椭圆等方法,选取4个典型的极端高温指数,分析了中国极端高温事件时空格局演变特征。结果表明：① 中国近40 a来夏天日数、热夜日数、暖夜日数和暖昼日数均呈显著的上升趋势,4个指数均在20世纪80、90年代偏少,2000年以后逐渐增加,4个极端高温指数均在2000年左右发生显著变化。② 4种极端高温指数的空间自相关主要是以高?高和低?低2种空间聚集形态为主,夏天日数和热夜日数的聚集性较强,近40 a来暖夜日数和暖昼日数的空间聚集性先增强后减弱,且空间聚集性分布格局由高?高包围低?低转变为低?低包围高?高。③ 4个指数变化率最大的站点均位于南方地区,其中夏天日数变化率最大的站点呈东西向分布格局,其余3个指数变化率最大的站点呈南北向分布格局,西南、西北地区交界地带夏天日数和暖昼日数在近40 a来变化率均显著高于全国其他地区,华东沿海地区暖夜日数的变化趋势方向性分布最明显,且变化趋势高于全国其他地区。  相似文献   

海拉尔地震台SSQ-2I水平摆与VP垂直摆观测数据对比分析     

申影  王怡  堵伟鹏 《地震地磁观测与研究》2021,43(1):133-140

基于SSQ-2I型数字石英水平摆与VP型垂直摆倾斜仪2种摆式倾斜仪不同的工作原理,对2018—2020年海拉尔地震台2套仪器的观测数据连续率与完整率、倾斜量年飘零与年变幅、数据观测精度、噪声水平、映震能力等进行对比分析,以对2套仪器的效能进行综合评价。结果表明,SSQ-2I水平摆仪器效能优于VP垂直摆。  相似文献   

Illite Crystallinity Mapping of Very Low Grade Metamorphism of Triassic Metapelites in the Zoigê Area, Western China     

TANG Yan  SANG Longkang  YUAN Yanming  YU Jishun  ZHANG Yunpeng  QI Xianmao  YANG Yunlong 《《地质学报》英文版》2012,86(1):96-105

X-ray diffraction methods for estimating the metamorphic grade of diagenetic, anchizone and epizone in metapelites are reviewed and applied to samples from a 7000?m+ borehole in western China and surface samples from the surrounding Zoigê area. Kübler’s illite crystallinity (IC) measurements provide more consistent results than calculated values of percentage of illite in the I/S mixed layers and percentage of I/S mixed layers. Down-borehole IC values display a typical burial metamorphic relationship between stratigraphic level and IC. A method for preparing very low grade metamorphic maps is described, and isograds plotted on a regional geological map at selected values of IC, delineating a high temperature diagenetic zone, an anchizone, and an epizone. The map shows that IC values are controlled by stratigraphic level in the north of the study area (i.e. burial metamorphism), and proximity to an igneous intrusive body in the south (i.e. contact metamorphism).  相似文献   

全国农村人均住房面积的空间自相关分析     

周玉科  高锡章  周成虎 《测绘与空间地理信息》2014,(11)

利用2006年全国各省农村居民人均住房面积统计数据,基于空间自相关方法从空间尺度分析其空间分布特征。首先建立空间邻近网络和邻接矩阵,通过Moran′I自相关指数分析空间关联性,为确定农村人均住房面积的分布存在空间相关性而非随机性,采用蒙特卡罗方法进行多次模拟证明,并利用2011年统计数据进行实际验证。实验分析,2006与2011年农村人均住房面积Moran′I指数分别为0．5566和0．5983,表明空间聚集特点明显,基本可以分为东部发达地区、中部和西部三种聚类,并且两年之间聚集现象有显著变化。  相似文献   

锦屏一级水电站左岸开挖高边坡变形监测分析   总被引：1，自引：0，他引：1  

黄志鹏  董燕军  廖年春  尹健民  周江平 《岩土力学》2012,33(Z2):235-242

锦屏一级水电站左岸开挖高边坡的开挖高度达到530 m,断层发育,岩体卸荷深度大,地质条件十分复杂,边坡在施工期和运行期的稳定性问题特别重要。对边坡的工程地质条件进行分析,介绍锦屏一级水电站工程左岸边坡的变形监测布置及监测结果。锦屏一级左坝肩边坡采用表面变形观测、浅表变形观测及深部变形观测,由表及里3个层次监测边坡岩体的变形。表面变形监测采用外观变形监测方法;浅部变形监测采用多点位移计,监测深度为0～90 m;深部变形监测采用平洞测距、水准沉降及石墨杆收敛计等监测方法,布置于勘探平洞内,穿越主要断层及深部拉裂缝,最大监测达到260 m。截止2011年5月,边坡浅表最大水平位移106.1 mm,最大垂直下沉位移58.6 mm,主要受边坡开挖及支护控制。深层最大水平变形量为47.48 mm,最大垂直沉降变形为7.2 mm,主要受深部拉裂缝及断层控制。目前位移趋于收敛,最大变形速率小于0.1 mm/d,满足安全控制标准,边坡已趋于稳定。  相似文献