贵州省梵净山区新元古代岩浆活动的年代学格架及其大地构造意义   总被引：1，自引：0，他引：1       下载免费PDF全文

王敏  戴传固  陈建书  王雪华  马会珍 《中国地质》2016,(3):843-856

江南造山带位于华夏与扬子地块之间,发育大量新元古代火成岩,是研究地球早期壳幔相互作用、板块构造演化的理想对象。江南造山带东段新元古代板块演化研究已初具雏形,但对其西南段构造演化还争议不断,主要问题在于没有构建与区域地质特点吻合的岩浆活动年代学格架。本文以江南造山带西南段梵净山为研究区,基于详细的区域地质填图结果,针对侵入于梵净山群(沉积时代850~830 Ma)中的基性-超基性岩样品开展原位锆石年代学研究。新的年代学数据表明,侵入于梵净山群的3个辉长岩体结晶年龄分别为813 Ma、804 Ma、748 Ma。结合前人发表数据,提出梵净山地区岩浆活动可划分为两个阶段:晋宁Ⅰ期(850~825 Ma)、晋宁Ⅱ期(820~750 Ma),分别对应于梵净山期、下江期盆地演化。该岩浆岩年代学格架与区域地层年代格架吻合,形成了完整的新元古代沉积-岩浆活动记录。这套沉积-岩浆组合的大地构造背景尚不明确,需要通过大地构造相分析予以确定。  相似文献   

长白山天池火山气象站期晚期碱流质熔岩的岩石学研究   总被引：3，自引：0，他引：3  

刘永顺  聂保锋  孙善平  穆大卫  史延升 《现代地质》2007,21(2):296-306

通过野外火山堆积物的相分析、岩石显微鉴定和造岩矿物化学分析,可以确认气象站期晚期碱流质熔岩是典型的溢流熔浆冷却固结形成的,不是碎成熔岩。熔岩流的顶部和底部是黑曜质碱流岩的表壳相,中部是致密厚层与薄层相间产出的、具有塑性变形的碱流岩的内部相。组成熔岩流的岩石具有斑状和聚斑结构,从表壳相向内部相基质依次发育玻璃质结构、（微）球粒结构和霏细结构。斑晶矿物钠透长石、钙铁辉石、铁橄榄石和少量石英出现在熔岩流的所有岩相中,而钠铁闪石、铁钠透闪石和钛铁矿则作为内部相基质中的显微斑晶出现。气象站期晚期碱流质熔岩是过铝质、过碱性的钠闪碱流质熔岩,属于碱性系列,与意大利潘泰莱里亚岛碱流岩相比,富Si、Al、K、Mg、Ca和P而贫Fe、Na、Mn和Ti。  相似文献   

苏南及沿江地区柏山组,下蜀组的时代及成因   总被引：10，自引：3，他引：7  

邵家骥 《江苏地质》1999,23(1):10-16

柏山组与下蜀组是江苏西南部丘陵山区的两个岩石地层单位,也是第四纪特定气候环境下形成的两类土状堆积。经与平原区第四纪地层对比,柏山组的层位与平原区的海门组上段至启东组下段相当,沉积时代为早更新世晚期到中更新世早期;下蜀组与平原区的启东组至湖组相当。沉积时代为中更新世晚期至晚更新世。柏山组网纹红土是早期干凉气候环境下堆积的黄土,经后期强烈湿热、氧化及流水冲刷后的产物,成因以洪冲积为主;下蜀组黄土是干凉气候环境下的产物,是风尘物质经流水改造后的产物,具多成因特点。  相似文献   

浙江煤山长兴阶有机碳δ^13C层序分布特征及古气候意义   总被引：12，自引：1，他引：11  

王万春  李玉成 《地质论评》1999,45(4):368-374

本文通过对浙江长兴煤山Ｄ剖面长兴阶５６个样品的沉积有机碳碳同位素（δ＾１３Ｃｏｒｇ）分析,讨论了和只有机碳δ＾１３Ｃｏｒｇ在地层层序分布上的特征,及其与海水进退和碳酸盐岩δ＾１３Ｃｃａｒｂ及δ＾１８Ｏｃａｒｂ之间的关系。浙江煤山Ｄ剖面长兴阶δ＾１３Ｃｏｒｇ在地层层序上的分布总体呈现自下而上由重变轻的趋势,同时,δ＾１３Ｃｏｒｇ层序分布与生物演化及δ＾１３Ｃｃａｒｂ和δ＾１８Ｏｃａｒｂ层序分布之间具  相似文献   

酒泉盆地群热演化史恢复及其对比研究   总被引：18，自引：1，他引：17  

任战利  刘池阳  张小会  吴汉宁  陈刚  李进步  马团校 《地球物理学报》2000,43(5):635-645

酒泉盆地群是由两期不同性质、不同世代盆地叠加而成的 .晚侏罗纪-早白垩世为拉张断陷盆地 ,第三纪以来为挤压坳陷盆地 .酒泉盆地群现今地温梯度及大地热流值都较低 ,地温梯度主要在 2 51- 3 0 0℃ /1 0 0m之间 ,大地热流值在 50- 57mW /m2 之间 .酒泉盆地群中生代晚期为拉张断陷 ,古地温梯度高 ,可达 3 75- 4 50℃ /1 0 0m ,新生代以来地温梯度逐渐降低 ,而花海盆地、酒西盆地石北凹陷沉降幅度小 ,古地温高于今地温 .下白垩统烃源岩热演化程度受古地温控制 .主生烃期仅有一次 ,为早白垩世晚期 .酒西盆地青西凹陷、酒东盆地营尔凹陷在新生代以来大幅度沉降 ,下白垩统烃源岩热演化程度受现今地温控制 .主生烃期有两次 ,一次为早白垩世晚期 ,另一次为晚第三纪以来 ,且以晚第三纪以来为主 .不同盆地及同一盆地不同构造单元由于构造热演化史的不同 ,主生烃期及油气勘探前景明显不同 .  相似文献   

湖南龙潭煤系形成时的大地构造环境   总被引：4，自引：1，他引：3  

彭正奇 《煤田地质与勘探》1996,24(4):5-8

湖南龙潭煤系属于早二叠世末-晚二叠世初期的沉积,沉积类型复杂。江南隆起东南面,以双牌-长寿断裂为界,东西两侧分属不同的物源区。通过对龙潭煤系分布、沉积环境演化、岩相展布、岩浆活动、构造特征、砂岩矿物成分及化学成分的研究认为,早二叠世末-晚二叠世初,区内大地构造环境属于较活动的被动大陆边缘。   相似文献   

南水北调西线一期工程区地壳活动有关问题   总被引：1，自引：0，他引：1  

陈智梁  刘宇平  孙志明  赵济湘  唐文清  张清志  潘忠习 《山地学报》2005,23(6):641-650

南水北调西线一期工程位于川青地块及其南缘鲜水河断裂带,地质条件复杂。GPS监测表明,川青地块及其邻区的地壳运动水平速度,具有自西向东递变下降的顺时针涡旋转动的总趋势;鲜水河断裂带有较高的移动速率;工程区东、西两侧的测站之间有一定的水平速度矢量差。工程区为高地应力区,并可产生局部高应变能带。鲜水河断裂带为我国西部的强震带;川青地块内部已发生5级以上地震25次。与中强震有关的断裂带通过工程区,并表现出工程区地壳活动性。地壳活动性将对南水北调西线一期工程建设产生重大影响。  相似文献   

松辽盆地白垩系青山口阶界线层型剖面研究   总被引：3，自引：0，他引：3  

韩刚  张文婧  黄清华  万晓樵  贺怀宇 《地层学杂志》2012,(3):569-578

茂206井是中国白垩纪大陆科学钻探工程井,全井获取了青山口阶497.02m的岩芯资料。茂206井青山口阶为典型的湖相沉积,它具有相对高的有机碳、无机碳稳定同位素,表示当时古湖泊具有较高的生产力;同时在青山口阶下部具有高的规则甾烷/藿烷比值和伽马蜡烷/C30藿烷比值以及低的重排甾烷/常规甾烷比值,表示当时的古湖泊曾发生过藻类勃发事件、水体分层事件和缺氧事件,由此导致了青山口阶优质烃源岩的形成。青山口阶底部出现的一些具重要时代意义的被子植物花粉Cranwellia,Lythraites,Complexiopollis,Borealipollis等,显示青山口阶具有晚白垩世土仑期以后的被子植物花粉色彩,以及湖相沉积岩夹层中的火山灰(斑脱岩)锆石U-Pb年龄也证实了青山口阶底界已属土仑期,其顶界已进入康尼亚克期。  相似文献   

Spathian to Aegean (upper Lower Triassic to lower Middle Triassic) carbon isotope stratigraphy constrained by the conodont biostratigraphy of carbonates on top of a mid-oceanic seamount formed in the Panthalassic Ocean     

Thuy Thi Nhu Ha  Takumi Maekawa  Hideko Takayanagi  Yasufumi Iryu 《Island Arc》2021,30(1):e12391

The Taho Formation in western Shikoku Island, Japan, consists of Triassic carbonates that formed on a seamount in the Panthalassic Ocean. In order to investigate the stratigraphy and paleoceanography of this carbonate succession, we analyzed the biostratigraphy and chemostratigraphy of a 17.6 m-thick section of the upper Taho Formation at the stratotype area in Tahokamigumi, Seiyo City. This section comprises bioclastic limestone containing Triassic bivalves, ammonoids, and conodonts. We recognized six conodont zones (in ascending order): the Novispathodus pingdingshanensis, Novispathodus brevissimus, Triassospathodus symmetricus, Triassospathodus homeri, Chiosella timorensis, and Magnigondolella cf. alexanderi zones. Thus, the studied carbonate succession is latest Smithian to Aegean in age. A δ¹³C profile of this section shows elevated values during the lowest Spathian followed by a gradual negative excursion, a subsequent positive excursion near the Spathian–Aegean boundary, and relatively constant values during the Aegean. The characteristic series of negative and positive excursions correlates with other δ¹³C records for this period, including the peak of the upper Smithian–lowest Spathian positive excursion (P3), lower to middle Spathian negative excursion (N4), and middle Spathian–lowest Aegean positive excursion (P4). This represents a new high-resolution Spathian–Aegean δ¹³C record of the Panthalassic Ocean, for which ages are constrained by conodont biostratigraphy. The Taho δ¹³C profile exhibits a consistent positive offset of ~2 ‰ as compared with those from other regions (i.e., mostly in the Tethyan Ocean). This can be explained by preferential removal of ¹²C from seawater during photosynthesis and calcification by marine organisms over the platform, and/or the relatively high δ¹³C values of dissolved inorganic carbon in the Panthalassic Ocean due to less influence of ¹²C-enriched terrestrial waters and high marine organic production/burial as compared with the more restricted Tethyan Ocean.  相似文献   

Comparison of radar and gauge precipitation data in watershed models across varying spatial and temporal scales          下载免费PDF全文

Katie Price  S. Thomas Purucker  Stephen R. Kraemer  Justin E. Babendreier  Chris D. Knightes 《水文研究》2014,28(9):3505-3520

Precipitation is a key control on watershed hydrologic modelling output, with errors in rainfall propagating through subsequent stages of water quantity and quality analysis. Most watershed models incorporate precipitation data from rain gauges; higher‐resolution data sources are available, but they are associated with greater computational requirements and expertise. Here, we investigate whether the Multisensor Precipitation Estimator (MPE or Stage IV Next‐Generation Radar) data improve the accuracy of streamflow simulations using the Soil and Water Assessment Tool (SWAT), compared with rain gauge data. Simulated flows from 2002 to 2010 at five timesteps were compared with observed flows for four nested subwatersheds of the Neuse River basin in North Carolina (21‐, 203‐, 2979‐, and 10 100‐km² watershed area), using a multi‐objective function, informal likelihood‐weighted calibration approach. Across watersheds and timesteps, total gauge precipitation was greater than radar precipitation, but radar data showed a conditional bias of higher rainfall estimates during large events (>25–50 mm/day). Model parameterization differed between calibrations with the two datasets, despite the fact that all watershed characteristics were the same across simulation scenarios. This underscores the importance of linking calibration parameters to realistic processes. SWAT simulations with both datasets underestimated median and low flows, whereas radar‐based simulations were more accurate than gauge‐based simulations for high flows. At coarser timesteps, differences were less pronounced. Our results suggest that modelling efforts in watersheds with poor rain gauge coverage can be improved with MPE radar data, especially at short timesteps. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.  相似文献