西藏普兰石英岩中发现41亿年碎屑锆石   总被引：8，自引：0，他引：8  

温春齐  多吉  范小平  郭建慈  倪志耀  李小文  石玉若  温泉 《地质学报》2006,80(9):1249-1251

在西藏普兰县石英岩中,利用SHRIMPU-Pb法测年发现4.1Ga碎屑锆石。该年龄为目前中国最老单颗粒碎屑年龄。>4.0Ga锆石两测点的Th/U值介于0.76~0.86之间,属岩浆锆石。这一发现,为研究青藏高原的地质演化提供了重要的年龄数据。  相似文献   

Do paleoclimate proxies agree? A test comparing 19 late Holocene climate and sea‐ice reconstructions from Icelandic marine and lake sediments     

Yarrow Axford  Camilla S. Andresen  John T. Andrews  Simon T. Belt  Áslaug Geirsdóttir  Guillaume Massé  Gifford H. Miller  Sædís Ólafsdóttir  Lindsay L. Vare 《第四纪科学杂志》2011,26(6):645-656

Geochemical, mineralogical and biological indicators preserved in sediments are widely used to reconstruct past climate change, but proxies differ in the degree to which their utility as climate indicators has been validated via laboratory experiments, modern spatial calibrations, or down‐core comparisons with instrumental climate data. Multi‐proxy studies provide another means of evaluating interpretations of proxies. This paper presents a multi‐proxy assessment comparing 19 sub‐centennially resolved late Holocene proxy records, covering the period 300–1900 AD, from seven Icelandic marine and lacustrine core sites. We employ simple statistical comparisons between proxy reconstructions to evaluate their correlations over time and, ultimately, their utility as proxies for regional climate. Proxies examined include oxygen isotopic composition of benthic and planktonic foraminifera, abundance of the sea‐ice biomarker IP₂₅, allochthonous quartz in marine sediments (a proxy for drift ice around Iceland), marine carbonate abundance, total organic carbon concentration, chironomid assemblages, lacustrine biogenic silica and carbon/nitrogen ratios in lake sediments. Most of the examined proxy records, including temperature and sea‐ice proxies, correlate strongly with each other over multi‐centennial timescales, and thus do appear to record changes in regional climate. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

锦州25—1区块探井钻井实践与认识     

魏刚  ;刘小刚  ;陶林  ;张春琳 《海洋地质译丛》2009,(3):71-74

锦州25—1油田是渤海湾近年钻探发现的大型油田。锦州25—1区块先后钻了十多口探井，在钻井作业中遇到上部井眼扩大严重、井径不规则、井垮、起下钻遏阻卡、电测作业遏阻、电测井底沉砂较多、井漏等复杂情况。通过对锦州25—1区块前面几口探井钻井中出现的问题进行认真分析，研究了锦州25—1区块的地层压力剖面分布。经过不断的总结与措施改进后，在后面的探井钻井作业中做到了起下钻顺利，上部井径扩大率较小，未出现井垮情况，电测一次到底，钻井作业生产时间大幅度提高，为锦州25—1油田的生产井钻井积累了宝贵的经验。  相似文献   

珠江口盆地白云凹陷陆坡区10.5 Ma以来的沉积体系   总被引：1，自引：0，他引：1  

武强  解习农  邱燕  刘明玲 《海洋地质与第四纪地质》2008,28(2):1-6

通过对珠江口盆地白云凹陷陆坡区10.5Ma以来的地震相分析,共识别出席状平行亚平行地震相、透镜状前积地震相、深切河谷地震相、帚状地震相和杂乱地震相,不同的地震相分别代表不同的沉积体系类型。综合所识别的地震相类型,分析了陆架边缘下切谷、浊积扇和陆架边缘三角洲3种主要的沉积体系及其配置关系。物源供给是影响陆坡区沉积体系发育的最重要因素,是沉积体系发育的物质基础,海平面变化和构造运动为沉积体系发育提供了可容纳空间,3种影响因素共同影响了陆坡区沉积体系的发育。  相似文献   

渤中25-1油田沙河街组低孔低渗储层特征及分类评价   总被引：3，自引：0，他引：3  

杨玉卿  潘福熙  田洪  徐晋  陈力群 《现代地质》2010,24(4)

渤中25-1油田位于渤海南部海域,其主力油层为古近系沙河街组,总体上属于低孔低渗储层。通过薄片、扫描电镜、X衍射分析和测井解释等手段,对沙河街组砂岩储层的岩石学特征、沉积特征、物性和孔隙结构特征进行了分析研究。沙河街组沙三段为较深水湖泊环境下的浊积扇沉积,沙二段为扇三角洲沉积;岩性主要为岩屑长石砂岩,储层孔隙类型为混合孔隙、次生孔隙和原生孔隙,由于沙三段溶蚀孔隙发育较沙二段少,沙三段物性较沙二段差。结合储层试油结果,提出了低孔低渗储层宏观成因、微观孔隙结构和综合评价3种分类方案,总体上把储层分为好、中和差3类,对应产能分别为大于80 m3/d、介于10~100 m3/d之间、小于10 m3/d和微量或无产能。经过该油田沙河街组5口井、15个储层段的测试验证,储层宏观成因分类评价结果与实际试油结果符合率达到86.67%,微观孔隙结构分类和综合分类评价结果与实际试油结果基本吻合。  相似文献   

Tracing the 850-Ma continental flood basalts from a piece of subducted continental crust in the North Qaidam UHPM belt,NW China   总被引：10，自引：0，他引：10  

Shuguang Song  Li Su  Xian-hua Li  Guibing Zhang  Yaoling Niu  Lifei Zhang 《Precambrian Research》2010

A Paleozoic ultrahigh-pressure metamorphic (UHPM) belt extends along the northern margin of the Qaidam Basin, North Tibetan Plateau. Eclogites in the Yuka eclogite terrane, northwest part of this UHPM belt, occur as blocks or layers of varying size intercalated with granitic and pelitic gneisses. These eclogites have protoliths geochemically similar to enriched-type mid-ocean ridge basalts (E-MORB) and oceanic island basalts (OIB). On the basis of Ti/Y ratios, they can be divided into low-Ti and high-Ti groups. The low-Ti group (LTG) eclogites exhibit relatively low TiO₂ (most <2.5 wt%) and Ti/Y (<500) but comparatively high Mg# (48–55), whereas the high-Ti group (HTG) eclogites have high TiO₂ (most >2.5 wt%) and Ti/Y (>500) but lower Mg# (46–52). Zircons from two eclogite samples gave a magmatic crystallization (protolith) age of ∼850 Ma and a UHPM age of ∼433 Ma. The occurrence, geochemical features and age data of the Yuka eclogites suggest that their protoliths are segments of continental flood basalts (CFBs) with a mantle plume origin, similar to most typical CFBs. Our observation, together with the tectonic history and regional geologic context, lend support for the large scale onset of mantle plume within the Rodinia supercontinent at ∼850 Ma. The Qaidam block is probably one of the fragments of the Rodinia supercontinent with a volcanic-rifted passive margin. The latter may have been dragged to mantle depths by its subducting leading edge of the oceanic lithosphere in the Early Paleozoic.  相似文献   

辐射井疏干技术在露天矿地下水疏干中的应用研究     

唐钊  朱国荣  王维勤  洪振川  王丛林 《江苏地质》2014,38(4):638-643

现有的井群疏干、地下巷道集中排水、地表地下联合疏干方法都已比较成熟有效,但当矿区的地下水系统由非均质各向异性、低渗透性含水介质组成时,井群疏干受到低渗透性含水层和高倾角裂隙的制约,无法达到良好的疏干效果。地下巷道集中排水方法一次性工程投入很大,含水层富水性极度不均时易造成许多不必要的浪费;地表地下联合疏干方法的地面部分对矿坑边坡安全和采场作业都会造成一定的影响。结合马钢集团南山矿业公司高村露天铁矿的地下水疏干技术研究专项,调查分析了矿区地质和水文地质条件,含水介质特点及含水层富水特征,借助GMS软件建立了高村矿区地下水水流模型,提出了辐射井疏干技术的设想,并依据前人提出的＂渗流-管流耦合模型＂模拟辐射井,完成了此类矿山的地下水辐射井疏干方法的初步研究。  相似文献   

秦岭山阳-柞水矿集区150~140Ma斑岩-矽卡岩型CuMoFe(Au)矿床成矿作用研究   总被引：4，自引：3，他引：1  

陈雷  王宗起  闫臻  吴发富  任涛  郭延辉 《岩石学报》2014,30(2):415-436

秦岭造山带内的山阳-柞水古生代弧前盆地中出露有池沟、小河口、冷水沟、园子街、下官坊及双元沟等CuMo、CuFe(Au)矿床,与这些矿床具有成因联系的岩体为形成于150~140Ma的高钾钙碱性和钾玄岩系列花岗岩,为华北和扬子大陆碰撞后伸展阶段壳、幔混合岩浆的产物。矿化主要发生在岩体与泥盆、石炭纪地层中碳酸盐岩的接触带附近,主要类型为矽卡岩型,少量为斑岩型,部分矿床具有统一的矽卡岩-斑岩型成矿系统,矿化组合主要为CuMo、CuFe(Au)和Cu矿化。外接触带主要发育有矽卡岩和角岩化蚀变,内接触带主要为岩体内部的硅化、钾化、绢云母化、绿泥石化及粘土化,内矽卡岩不发育。矽卡岩矿物主要有石榴石、透辉石、绿帘石、透闪石,阳起石等,其中石榴子石主要为钙铁榴石和钙铝榴石,透辉石是辉石的主体,早期形成的石榴石和透辉石等无水矿物组合常被后期的绿帘石、透闪石和阳起石等含水矿物及石英、方解石等所交代。金属矿物比较简单,最主要的含铜矿物为黄铜矿和斑铜矿,铁矿化主要为磁铁矿和镜铁矿。尽管这些矿床以矽卡岩型矿化为主,但部分矿床中已发现有斑岩型矿化和蚀变特征,这可能暗示了该区可能具有统一的矽卡岩-斑岩型成矿系统,进而表明山阳-柞水矿集区深部具有寻找斑岩型矿床的巨大潜力。  相似文献   

Age of younger tonalitic magmatism and granulitic metamorphism in the South Indian transition zone (Krishnagiri area); comparison with older Peninsular gneisses from the Gorur–Hassan area     

J. J. PEUCAT  B. MAHABALESWAR  M. JAYANANDA 《Journal of Metamorphic Geology》1993,11(6):879-888

Abstract A major episode of continental crust formation, associated with granulite facies metamorphism, occurred at 2.55–2.51 Ga and was related to accretional processes of juvenile crust. Dating of tonalitic–trondhjemitic, granitic gneisses and charnockites from the Krishnagiri area of South India indicates that magmatic protoliths are 2550–2530 ± 5 Ma, as shown by both U–Pb and ²⁰⁷Pb/²⁰⁶Pb single zircon methods. Monazite ages indicate high temperatures of cooling corresponding to conditions close to granulite facies metamorphism at 2510 ± 10 Ma. These data provide precise time constraints and Sr–Nd isotopes confirm the existence of late tonalitic–granodioritic juvenile gneisses at 2550 Ma. Pb single zircon ages from the older Peninsular gneisses (Gorur–Hassan area) are in agreement with some previous Sr ages and range between 3200 ± 20 and 3328 ± 10 Ma. These gneisses were derived from a 3.3–3.5-Ga mantle source as indicated from Nd isotopes. They did not participate significantly in the genesis of the 2.55-Ga juvenile magmas. All these data, together with previous work, suggest that the 2.51-Ga granulite facies metamorphism occurred near the contact of the ancient Peninsular gneisses and the 2.55–2.52-Ga ‘juvenile’tonalitic–trondhjemitic terranes during synaccretional processes (subduction, mantle plume?). Rb–Sr biotite ages between 2060 and 2340 Ma indicate late cooling probably related to the dextral major east–west shearing which displaced the 2.5-Ga juvenile terranes toward the west.  相似文献   

济阳拗陷特殊生物降解油的初步研究   总被引：1，自引：1，他引：0  

卢鸿  彭平安  徐兴友  张林晔 《沉积学报》2004,22(4):694-699

济阳拗陷草古100平19井奥陶系储层原油,饱和烃馏分均已损失殆尽,仅残余藿烷系列化合物;同时,芳烃馏分化合物也已损失殆尽,仅残余三芳甾烷系列化合物。上述芳烃化合物俱已损失殆尽的蚀变特征,在相关文献中的报道较为少见。原油中不受水洗作用影响的正构烷烃和不受生物降解作用影响的有机硫化合物(苯并噻吩和二苯并噻吩)均已损失殆尽,显然暗示了原油蚀变是遭受水洗作用和生物降解作用共同作用的结果。原油芳烃馏分的“UCM”鼓包幅度明显大于饱和烃馏分的“UCM”鼓包,暗示了芳烃化合物的降解速率平行甚至超过饱和烃的降解速率。原油中低分子量芳烃化合物的快速降解,暗示了油藏可能是在氧化条件下而非在还原条件下发生蚀变的。  相似文献