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对大兴安岭北段伊勒呼里山地区二长花岗岩进行了LA-ICP-MS锆石U-Pb年龄和岩石地球化学研究,确定其形成时代、岩石成因,揭露区域大地构造环境。测年数据显示,二长花岗岩于158.1±0.7Ma前形成,为晚侏罗世早期岩浆演化事件的产物。地球化学结果显示,二长花岗岩具有高Si、富Na、K、Al,低Fe、Mg的特点,A/CNK值为0.83~1.09,属高钾钙碱性花岗岩;富集大离子亲石元素K、Rb,贫高场强元素Hf、Th;稀土元素总量较高,稀土元素配分曲线右倾,具弱的负Eu异常,为Ⅰ型花岗岩。岩浆起源于下地壳玄武质成分的岩石部分熔融,为同碰撞期陆壳加厚过程的产物。研究区晚侏罗世早期二长花岗岩的形成与蒙古-鄂霍茨克缝合带闭合过程中的陆-陆碰撞环境有关,其形成时代限定了大兴安岭北段伊勒呼里山地区蒙古-鄂霍茨克洋的闭合时间应为晚侏罗世早期。 相似文献
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总结了南京河西长江漫滩地层的工程地质和水文地质特点,在调查了该地区已建地铁车站支护方案及实施效果的基础上,对适用于长江漫滩区地铁车站的基坑支护结构方案进行比较,对基坑工程中常见问题提出了针对性措施,对今后该地区地铁车站基坑工程设计和施工具有一定的指导意义. 相似文献
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The Hanjiang Formation of Langhian age(middle Miocene) in the Pearl River Mouth Basin (PRMB),South China Sea consists of deltaic siliciclastic and neritic shelf carbonate rhythmic alternations,which form one of the potential reservoirs of the basin.To improve stratigraphic resolutions for hydrocarbon prospecting and exploration in the basin,the present study undertakes spectral analysis of high-resolution natural gamma-ray(NCR) well-logging record to determine the dominant frequency components and test whether Milankovitch orbital signals are recorded in rhythmic successions.Analytical results indicate the orbital cycles of precession(～19 ka and～23 ka), obliquity(～41 ka),and eccentricity(～100 ka and～405 ka),which provide the strong evidence for astronomically driven climate changes in the rhythmic alternation successions.Within biochronological constraint,a high-resolution astronomical timescale was constructed through the astronomical tuning of the NGR record to recent astronomically calculated variation of Earth’s orbit. The astronomically tuned timescale can be applied to calculate astronomical ages for the geological events and bioevents recognized throughout the period.The first downhole occurrences of foraminifers Globorotalia peripheroronda and Globigerinoides sicanus are dated at 14.546 Ma and 14.919 Ma,respectively,which are slightly different from earlier estimates in the South China Sea. When compared with the global sea-level change chart,the astronomical estimate for the sequences recognized based on microfossil distributions have the same end time but the different initiation time. This is probably due to the local or regional tectonic activities superimposed on eustatic rise which postponed the effect of global sea-level rising.Astronomical timescale also resolves the depositional evolution history for the Langhian Stage(middle Miocene) with a variation that strongly resembles that of Earth’s orbital eccentricity predicted from 13.65 Ma to 15.97 Ma.We infer that the main factor controlling the variability of the sedimentation rate in the Hanjiang Formation is related to the～405-ka-period eccentricity. 相似文献
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伊勒呼里山中生代火山岩:锆石U-Pb年代学及其对岩浆事件的制约 总被引：3，自引：0，他引：3
伊勒呼里山地区中生代火山岩由安山岩、粗面英安岩、流纹岩、流纹质凝灰岩和流纹质玻屑凝灰岩等组成。中生代火山岩中的锆石多呈半自形-自形晶,振荡环带发育,Th/U值略高（0.30~2.56）,为岩浆成因。锆石U-Pb同位素年代学研究表明：塔木兰沟组安山岩年龄为（161.0±1.0）Ma（n=22）,形成于中侏罗世;满克头鄂博组流纹岩年龄为（157.8±2.3）Ma（n=24）,形成时代属于晚侏罗世;玛尼吐组火山岩2个样品的年龄分别为（154.0±2.0）Ma（n=23）和（151.7±1.4）Ma（n=25）,形成时代属于晚侏罗世;白音高老组火山岩2个样品的年龄分别为（124.1±1.1）Ma（n=25）和（125.1±0.7）Ma（n=23）,形成时代为早白垩世。捕获锆石的定年结果显示,本区存在前寒武纪岩浆事件（774 Ma）、加里东期岩浆事件（472 Ma）、印支期岩浆事件（214、210 Ma）,这与周边基底岩石中锆石U-Pb的定年结果相吻合。 相似文献
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休瓦促W-Mo矿床位于滇西北义敦-格咱岛弧中部,为一中大型斑岩岩浆热液矿床。由于自然环境恶劣,对该区晚白垩世构造岩浆活动的研究工作起步较晚,且主要集中于富碱岩浆成岩成矿年代学、岩石成因、动力学背景、流体特征和成矿物质来源研究等方面,但对岩浆成矿作用构造应力场和动力学机制的研究还比较薄弱。文中对休瓦促W-Mo矿床东、西矿区重点坑道和剖面开展构造岩相蚀变特征解析研究,并结合锆石U-Pb、Lu-Hf和O同位素特征,认为休瓦促花岗岩体为一个两期复式岩体,以近S-N向F4断层为界可分为东、西矿区。东矿区以晚三叠世(212~201 Ma)似斑状黑云母花岗岩为主;西矿区以晚白垩世(85.6~84.4 Ma)似斑状石英二长花岗岩和二长花岗斑岩为主。西矿区W-Mo矿床寄主石英二长花岗岩锆石原位U-Pb、Lu-Hf和O同位素显示其形成时代为(80.18±0.80) Ma (LA-ICP-MC U-Pb),εHf(t)和δ18O值分别为-4.49~-8.07和5.98‰~7.45‰,Hf同位素TDM2模式年龄分别为1 432~1 239 Ma,结合前人地球化学特征资料,推知晚白垩世石英二长花岗岩物质来源于加厚下地壳部分融熔作用。对矿区135个晚白垩世石英二长花岗岩岩脉和白钨矿辉钼矿石英脉产状数据进行区域构造解析研究,可判断义敦-格咱地区晚白垩世区域构造应力场特征为NE-SW向伸展。综上所述,义敦-格咱地区晚白垩世花岗岩可能形成于NW-SE向延伸的新特提斯洋盆俯冲作用致使先存古特提斯-中特提斯碰撞造山加厚下地壳减压部分熔融的动力学背景。 相似文献
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Kou Xiaohu Zhang Kexin Zhu Yunhai Chen Zhongqiang Lin Qixiang Chen Fenning Huang Jinyuan 《中国地质大学学报(英文版)》2009,20(2)
The well-preserved seamount buildups are documented from the northwestern Qinling (秦岭) orogenic belts, Northwest China. The study sections are located in the Ganjia (甘加) area of the Xiahe (夏河) County, Gansu (甘肃) Province. The dark basalt and overlying massive reef carbonate characterize the Xiahe seamount buildup. Basalts are dominated by the olivine type of rocks and bear distinct porphyritic textures, and fumarole and amygdaloidal structures. The basaits are dominated by SiO2(up to 48.49 wt.%-52.29 wt.%) followed by (Na2O+ K2O) (3.80 wt.%-4.96 wt.%) and TiO2 (2.04 wt.%-2.52 wt.%). They are featured by considerably high content of Ti. The tholeilteseries rocks dominate the basalts, while calc-alkali-series rocks are also present. The REE of the basalts shows the LREE-enrichment type with distinct positive Eu abnormal. The trace elements of the basalts are characterized by the lack of P and high content of Ti. These geochemical signals suggest that the Xiahe basalts were formed in an ocean-island setting. The LA ICP-MS zircon U-Pb age of the basalts is 267.6±5 Ma, which is reinforced by the presnce of the fusuHnid Neoschwagerina Zone of the Wordian (Middle Permian) in the limestone interbeds of the basalts. Integration of petrological and geochemical studies of seamount basaits and lateral correlation of seamount buildups reveals that the Qinling-qilian-Kunlun orogenic belts were probably the archipelagtc oceans during the Permian. 相似文献
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基于生态适宜性分析的湖泊保护与利用——以湖北斧头湖为例 总被引：1，自引：0，他引：1
为了湖泊生态系统健康及湖泊资源的可持续利用,需要根据湖泊的具体情况加强对湖泊生态系统的管理.建立在生态适宜性分析基础上的湖泊生态功能分区,可为科学合理地开发湖泊资源、协调湖泊生态系统结构与功能提供依据.以湖北省斧头湖为对象,在对斧头湖生态环境调查基础上,选取具有代表性的水质、生物及人为干扰因子;根据《地表水环境质量标准》(GB3838-2002)确定水质评价等级,采用专家论证法确定生物及人为干扰因子评价等级,建立起湖泊生态养殖适宜性评价等级体系;采用主成分分析法确定评价因子权重,并在GIS技术的支持下,采用因子叠加法,对斧头湖生态养殖适宜性进行综合评价.根据各区域生态养殖适宜性综合评价结果,同时考虑到湖泊生态环境和综合资源保护要求、斧头湖自然生态系统功能和生态渔业的可持续发展,可将斧头湖划分为极适宜区、高度适宜区、中度适宜区、轻度适宜区和较不适宜区;各适宜区面积分别占斧头湖总面积的12.04%、24.81%、49.65%、9.58%和3.92%.从湖泊生态系统保护及渔业的可持续利用角度看,极适宜区、高度适宜区适合开展生态养殖;中度适宜区和轻度适宜区要以生态恢复为主,可进行一定规模的放养养殖;较不适宜区应进行生态修复,不适宜进行各种开发活动. 相似文献
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