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1.
古纬度演化可以为地质历史时期古气候变化以及构造变形过程等提供宏观的构造位置背景。加强青藏高原中北部可可西里盆地的古纬度研究,对于理解青藏高原中北部的构造抬升过程历史以及机制、阐明东亚季风起源和演化与高原隆升变形的耦合关系、探讨可可西里盆地晚始新世孢粉所指示的干旱气候的动力机制等具有重要的意义。笔者等选取青藏高原腹地研究相对薄弱的可可西里盆地的一个次级沱沱河盆地（TTHC剖面）作为研究对象开展了古地磁研究,重建其在新生代的古纬度演化历史。岩石磁学研究表明TTHC剖面的主要载磁矿物是磁铁矿和赤铁矿,但以赤铁矿为主。与同期（约35 Ma）欧亚极期望磁倾角以及研究区西边乌兰乌拉湖地区的火山岩磁倾角对比,TTHC剖面所记录的磁倾角存在明显的浅化现象,经E/I方法校正后,得到在约35 Ma的古地磁方向为Dec=358.5°,Inc=44.4°,a95=5.7°。综合已发表的贡觉盆地、改则盆地、尼玛盆地、囊谦盆地、下拉秀盆地和乌兰乌拉湖火山岩等古纬度数据以及本文的研究结果,得到沱沱河盆地新生代古纬度演化历史（以TTHC剖面坐标为参考点）,沱沱河盆地在约35 Ma古纬度为26.1°N,处于副热带高气压气候带内,可以解释孢粉和岩性所指示的暖干气候。在约24 Ma沱沱河盆地到达现在的纬度位置,盆地上地壳缩短在约24 Ma减小或者停止。 相似文献
2.
可可西里盆地新生代沉积演化历史重建 总被引：11，自引：1，他引：11
青藏高原北部可可西里盆地是高原腹地最大的第三纪沉积盆地,分布着厚度达5737.5m的新生代沉积.本文根据遍布整个盆地的野外实测剖面和地质观察点资料,采用典型剖面精确古地磁测年为基础的时间框架,开展沉积层序、岩性特征、沉积环境和古水流变化综合对比研究,将可可西里盆地新生代(约56Ma至约16Ma)划分为7个演化阶段,其中在30Ma至约23Ma期间盆地经历抬升变形,没有沉积作用发生.结果显示,前6个阶段(约56Ma至30Ma),盆地沉积中心逐渐向北、向东迁移,盆地南缘和西缘的构造逆冲作用逐步加强,而且在晚渐新世发生强烈南北向地壳缩短,反映青藏高原腹地早期隆升过程是依靠南北向地壳缩短和北东向逆冲扩展作用来实现的.在早中新世(约23Ma至约16Ma),盆地沉积物遭受低度变形,表明此期间高原以差异隆升为主. 相似文献
3.
青藏高原北部可可西里盆地是高原腹地最大的第三纪沉积盆地，分布着厚度达5737.5m的新生代沉积。本文根据遍布整个盆地的野外实测剖面和地质观察点资料，采有典型剖面精确古地磁测年为基础的时间框架，开展沉积层序、岩笥特征、沉环境和古水流变化综合对比研究，将可可西里盆地新生代（约56Ma至约16Ma）划分为7个演化阶段，其中在30Ma至约23Ma期间盆地经历抬升变形，没有沉积作用发生。结果显示，前6个阶段（约56Ma至30Ma），盆地沉积中心逐渐向北、向东迁移，盆地南缘和西缘的构造逆冲作用逐步加强，而且在晚渐新世发生强烈南北向地壳缩短，反映青藏高原腹地早期隆升过程中依靠南北向地壳缩短和北东向逆冲扩展作用来实现的。在早中新世（约23Ma至约16Ma），盆地沉积物遭受低度变形，表明此期间高原以差异隆升为主。 相似文献
4.
磁倾角是古纬度的记录者,对许多构造活动有着很好的揭示作用.但在青藏高原,沉积物的磁倾角往往要比火山岩或欧亚极预测的值要小,这很大程度上制约了对该地区构造演化历史的了解.本文应用E/I统计分析法对青藏高原东北部几个典型山间盆地的已有古地磁数据进行分析,发现该地区沉积物中普遍存在的10°～ 20°磁倾角浅化可以通过该法矫正,揭示出该地区的磁倾角浅化可能是由于沉积物在沉积过程中或沉积后的压实作用造成;同时也表明该地区在晚新生代以来南北向缩短量并不是十分显著,至少是在古地磁研究的误差范围以内. 相似文献
5.
青藏高原东北缘寺口子盆地新生代沉积演化及其构造意义 总被引：2，自引：0，他引：2
宁夏固原寺口子盆地发育巨厚的新生代地层,这些地层记录了青藏高原东北部的沉积演化特征和构造演变历史。根据剖面沉积物粒度特征、沉积结构和构造、沉积层序,识别出20种岩相、5种沉积相类型。结合前人对寺口子剖面的古地磁测年,分析研究盆地的沉积演化特征以及对构造的响应表明:20.1 Ma盆地以缓慢的坳陷沉降开始演化,直至1.2 Ma遭受破坏。在此期间青藏高原东北部经历了6.4 Ma、4.6 Ma和1.2 Ma这3次明显的构造挤压隆升运动,其中约6.4 Ma的构造运动是青藏高原向东北部扩展首次影响到海原—六盘山断裂以东地区。从盆地的形成和沉积演化过程来看,马东山山前断裂的逆冲推覆,导致了寺口子盆地的强烈变形和构造降升,并且最终成为青藏高原的最新组成部分。 相似文献
6.
青藏高原东北缘是高原由西南向东北方向扩展的前缘位置，其新生代构造变形对揭示青藏高原隆升、扩展的过程与动力学机制具有重要的意义。柴达木盆地是青藏高原东北缘最大的新生代沉积盆地，发育巨厚的新生代地层，这些地层所记录的古地磁极旋转信息是定量约束柴达木盆地新生代以来构造变形发生的时间、方式与幅度的载体。本文以柴达木盆地北缘新生代地层出露良好、具有精确地层年代控制的路乐河剖面为研究对象，开展了古地磁极旋转研究，统计分析路乐河剖面24. 6~5. 2 Ma之间1477个可靠古地磁样品的特征剩磁方向(ChRM)，发现柴达木盆地北缘路乐河地区在24. 6~16. 4 Ma发生小幅度(不显著)的逆时针旋转，旋转角度约为8. 4°±6. 1°；16. 4~13. 9 Ma路乐河地区发生显著的顺时针旋转，旋转角度可达36. 1°±6. 0°；13. 9~5. 2 Ma 该地区未发生明显的构造旋转；5. 2 Ma以后路乐河地区逆时针旋转了~6°。结合柴达木盆地北缘区域构造变形的分析，我们提出柴达木盆地北缘路乐河地区在16. 4~13. 9 Ma 之间发生强烈的顺时针旋转构造变形(~36°)可能代表了盆地北缘中中新世遭受强烈的地壳差异缩短变形，从而成为高原最新形成的部分。 相似文献
7.
系统分析青藏高原新生代中新世50余个沉积盆地的类型、构造背景、岩石地层序列,对青藏高原中新世构造岩相古地理演化特征进行分析和探讨。中新世,青藏高原海相沉积已经全面退出,全部转为陆相沉积,约23Ma时高原及周边不整合面广布,标志高原整体隆升。塔里木、柴达木及西宁-兰州、羌塘、可可西里等地区主体表现为大面积的构造压陷湖盆沉积。约17.2Ma左右,阿尔金山显著隆升,使柴达木盆地西叉沟一带再无生物礁灰岩出现,且在盆地西部出现了短暂的沉积间断。这一时期,柴达木盆地西部开始进入湖退期,而东南部则快速湖进;同时,大约17.7Ma索尔库里山间盆地初始凹陷形成。另外,高原腹地五道梁-沱沱河盆地受南部唐古拉山的挤压抬升,在16Ma左右结束了五道梁组的沉积,在可可西里—唢呐湖一带则再次凹陷接受唢呐湖组沉积,形成高原腹地的大型压陷湖盆。13～10Ma期间,藏南南北向断陷盆地的形成,是高原隆升到足够高度开始垮塌的标志;约8Ma以来,高原东北部几乎所有湖盆均进入湖退期,普遍出现冲积扇、辫状河和水下扇砂砾岩堆积。 相似文献
8.
柴达木盆地东北部新近纪构造旋转及其意义 总被引：4，自引：1，他引：3
青藏高原东北缘构造变形的研究是认识高原隆起过程、机制和印度—欧亚板块碰撞远程效应的重要途径。柴达木盆地是印度－欧亚板块碰撞后南北向挤压应力为动力背景的高原东北部内陆盆地,沉积物主要来自于周边山地,完整的保存了新生代以来高原隆升的详细记录。通过柴达木盆地东北部瑙格剖面精细古地磁及构造旋转研究发现,20.1～15.1Ma以及15.1～8.2Ma柴达木盆地分别发生了9.7°±7.4°和6.4°±4.4°的顺时针旋转,约8.2Ma后,柴达木盆地东北部瑙格地区发生了16°±7.5°的逆时针快速旋转。通过分析认为,前两次的顺时针构造旋转事件可能与阿尔金断裂的左旋走滑有关。而约82Ma以来的逆时针旋转事件属于柴达木盆地东北部瑙格地区的局部旋转,可能与温泉断裂的右旋走滑有关,说明青藏高原东北部在昆仑山、阿尔金山和祁连山三条巨型断裂系左旋相对运动的宏观控制下形成的NNW向温泉右旋走滑断裂开始走滑的年代为约8Ma。 相似文献
9.
10.
青海循化盆地新近纪磁性地层学 总被引：4，自引：4，他引：0
青藏高原东北部是研究高原隆升和东亚季风演化的重要地区.通过对青藏高原东北部循化盆地西沟剖面新近纪河湖相沉积的磁性地层学研究, 建立了西沟剖面约14.6~5.0 Ma沉积物的磁极性年代框架.沉积相的分析表明, 循化盆地在约14.6~5.0 Ma期间总体上处于充填萎缩阶段.西沟剖面巨厚层砾岩首次出现的时间约为7.3 Ma前, 应是青藏高原东北部快速隆升的沉积响应.这与青藏高原在约8.0 Ma前快速隆升的时间相近, 进一步说明约8.0 Ma前青藏高原的构造隆升具有准同时性. 相似文献
11.
Police, politics, and the right to the city 总被引：1，自引：0，他引：1
Mustafa Dikeç 《GeoJournal》2002,58(2-3):91-98
Space and spatiality have recently been at the core of debates concerning the political possibilities of the city. The arguments advanced in this paper might be seen as an attempt to contribute to these debates through a reflection on the spatiality of (in) justice, politics, and the right to the city. The case of French urban policy, with its focus on distressed urban areas, and the `suburban problem' in France are used as examples to make arguments more concrete. 相似文献
12.
E. M. Prasolov S. A. Sergeev B. V. Belyatsky E. S. Bogomolov K. A. Gruzdov I. N. Kapitonov R. Sh. Krymsky V. O. Khalenev 《Geochemistry International》2018,56(1):46-64
This paper reports the first results of a study of 11 isotope systems (3He/4He, 40Ar/36Ar, 34S/32S, 65Cu/63Cu, 62Ni/60Ni, 87Sr/86Sr, 143Nd/144Nd, 206–208Pb/204Pb, Hf–Nd, U–Pb, and Re–Os) in the rocks and ores of the Cu–Ni–PGE deposits of the Norilsk ore district. Almost all the results were obtained at the Center of Isotopic Research of the Karpinskii All-Russia Research Institute of Geology. The use of a number of independent genetic isotopic signatures and comprehensive isotopic knowledge provided a methodic basis for the interpretation of approximately 5000 isotopic analyses of various elements. The presence of materials from two sources, crust and mantle, was detected in the composition of the rocks and ores. The contribution of the crustal source is especially significant in the paleofluids (gas–liquid microinclusions) of the ore-forming medium. Crustal solutions were probably a transport medium during ore formation. Air argon is dominant in the ores, which indicates a connection between the paleofluids and the atmosphere. This suggests intense groundwater circulation during the crystallization of ore minerals. The age of the rocks and ores of the Norilsk deposits was determined. The stage of orebody formation is restricted to a narrow age interval of 250 ± 10 Ma. An isotopic criterion was proposed for the ore-bearing potential of mafic intrusions in the Norilsk–Taimyr region. It includes several interrelated isotopic ratios of various elements: He, Ar, S, and others. 相似文献
13.
Delivery of Trace Metals (Al,Fe, Mn,V, Co,Ni, Cu,Cd, Ag,Pb) from the Trinity River Watershed Towards the Ocean 总被引：2，自引：0，他引：2
The Trinity River (Texas, USA) contains in its watershed 23 different reservoir lakes, the largest one being Lake Livingston
situated in the lower Trinity River watershed and two potentially polluting metroplexes, Dallas and Houston. In order to determine
fluxes of nutrients and trace metals to Galveston Bay, a survey that included 24 discreet samples collected over a year and
at various stages of discharge was carried out during 2000–2001. Geochemical (i.e., sorption by Fe oxyhydroxides), biological
(i.e., seasonal uptake by sinking algae in Lake Livingston), and hydrological (i.e., dilution effects by increasing flow rates)
controls were found to be mainly responsible for variations in dissolved trace metal concentrations rather than pollution
sources. The Trinity River loads of suspended sediments and pollutant trace metals entering Galveston Bay at Anahuac were
<20% of those reaching Lake Livingston, and only a few percent of the total upstream trace metal load is entering the Gulf
of Mexico. Thus, during the transit through the 23 man-made lakes and an estuary, >96% of the pollutant trace metal load is
lost to sediments. 相似文献
14.
15.
V. Yu. Prokof’ev L. D. Zorina V. A. Kovalenker N. N. Akinfiev I. A. Baksheev A. N. Krasnov G. A. Yurgenson N. V. Trubkin 《Geology of Ore Deposits》2007,49(1):31-68
The mineral composition of the Talatui gold deposit has been studied with modern methods. Previously unknown minerals (ilmenite, siegenite, glaucodot, wittichenite, matildite, hessite, pilsenite, zircon, tremolite, cummingtonite, hercynite, and goethite) have been identified in the ore. A high Re content has been detected in molybdenite. The spatiotemporal separation of Au and Ag is caused by different mineral species of these elements and their diachronous precipitation during the ore-forming process. Gold crystallized along with early mineral assemblages, beginning from virtually pure gold (the fineness is 996). Silver precipitated largely at the end of the process as hessite (Ag2Te) and matildite (AgBiS2). The temperature of ore deposition varied from 610 to 145°C, the pressure was 3370–110 bar, and the salt concentration ranged from 56.3 to 0.4 wt % NaCl equiv. The heterogeneous state (boiling) of fluid at the early stages has been documented. The chemical and isotopic compositions of the fluid testify to its magmatic nature and the participation of meteoric water at late stages in the ore-forming process. Thermodynamic modeling reproduces the main specific features of ore formation, including separation of Au and Ag. A physicochemical model of the gold mineralization in the Darasun ore district has been proposed. On the basis of several attributes, the Talatui deposit has been referred to the prophyry gold-copper economic type. 相似文献
16.
I. M. Gorokhov M. A. Semikhatov M. M. Arakelyants E. A. Fallick N. N. Mel’nikov T. L. Turchenko T. A. Ivanovskaya T. S. Zaitseva E. P. Kutyavin 《Stratigraphy and Geological Correlation》2006,14(3):260-274
Clay subfractions (SFs) of <0.1, 0.1–0.2, 0.2–0.3, 0.3–0.6, 0.6–2 and 2–5 μm separated from Middle Riphean shales of the Debengda Formation are studied using the TEM, XRD, K-Ar and Rb-Sr isotopic methods. The oxygen and hydrogen isotope compositions in the SFs are studied as well. The low-temperature illite-smectite is dominant mineral in all the SFs except for the coarsest ones. The XRD, chemical and isotopic data imply that two generations of authigenic illite-smectite different in age are mixed in the SFs. The illite crystallinity index decreases in parallel with size diminishing of clay particles. As compared to coarser SFs, illite of fine-grained subfractions is enriched in Al relative to Fe and Mg, contains more K, and reveals higher K/Rb and Rb/Sr ratios. The Rb-Sr age calculated by means of the leachochron (“inner isochron”) method declines gradually from 1254-1272 Ma in the coarsest SFs to 1038-1044 Ma in finest ones, while the K-Ar age decreases simultaneously from 1225–1240 to 1080 Ma. The established positive correlation of δ18O and δD values with dimensions of clay particles in the SFs seems to be also consistent with the mixing systematics. The isotopic systematics along with data on mineral composition and morphology lead to the conclusion that mixedlayer illite-smectite was formed in the Debengda shales during two periods 1211–1272 and 1038–1080 Ma ago. The first period is likely close to the deposition time of sediments and corresponds to events of burial catagenesis, whereas the second one is correlative with the regional uplift and changes in hydrological regime during the pre-Khaipakh break in sedimentation. 相似文献
17.
Influences of the unsaturated,saturated, and riparian zones on the transport of nitrate near the Merced River,California, USA 总被引：1，自引：0，他引：1
Joseph L. Domagalski Steven P. Phillips E. Randall Bayless Celia Zamora Carol Kendall Richard A. WildmanJr Janet G. Hering 《Hydrogeology Journal》2008,16(4):675-690
Transport and transformation of nitrate was evaluated along a 1-km groundwater transect from an almond orchard to the Merced River, California, USA, within an irrigated agricultural setting. As indicated by measurements of pore-water nitrate and modeling using the root zone water quality model, about 63% of the applied nitrogen was transported through a 6.5-m unsaturated zone. Transport times from recharge locations to the edge of a riparian zone ranged from approximately 6 months to greater than 100 years. This allowed for partial denitrification in horizons having mildly reducing conditions, and essentially no denitrification in horizons with oxidizing conditions. Transport times across a 50–100-m-wide riparian zone of less than a year to over 6 years and more strongly reducing conditions resulted in greater rates of denitrification. Isotopic measurements and concentrations of excess N2 in water were indicative of denitrification with the highest rates below the Merced River. Discharge of water and nitrate into the river was dependent on gradients driven by irrigation or river stage. The results suggest that the assimilative capacity for nitrate of the groundwater system, and particularly the riverbed, is limiting the nitrate load to the Merced River in the study area. 相似文献
18.
扬子北缘马元铅锌矿床闪锌矿微量元素及S-Pb-He-Ar-C同位素地球化学研究 总被引：7，自引：3，他引：4
马元铅锌矿床是近年扬子陆块北缘铅锌找矿的新突破。矿体呈层状、似层状产于碑坝隆起翼部震旦系灯影组角砾状白云岩层间构造带中,围岩蚀变很弱。矿石中硫化物以闪锌矿、方铅矿为主,中粗粒晶质结构,充填于白云岩角砾间。闪锌矿富集Cd、Ge、Ag,贫In、Tl、Se,Ga/In为6~132,Ge/In多1000,成矿温度以中-低温为主。金属硫化物ε~(34)S值相对集中,为12.9‰~19.4‰,平均为17.4‰,来自于海相硫酸盐的还原。铅同位素组成稳定,~(206)Pb/~(204)Pb为17.858~17.918:~(207)Pb/~(204)Pb为15.603~15.694;~(208)Pb/~(204)Pb为37.756~38.046,具有造山带和上地壳铅的特征,震旦系可能提供了金属成矿物质。闪锌矿中流体包裹体的~3He/~4He为0.03Ra~1.05Ra,~(40)Ar/~(36)Ar为326.1~765.1,~(38)Ar/~(36)Ar为0.183~0.204,表明成矿流体主要为地壳流体和饱和大气水(大气降水或海水)的混合。闪锌矿内流体包裹体挥发分δ~(13)C_(CH_4)值为-36.01‰~-28.80‰,δ~(13)C_(C_2H_6)值为-27.72‰~-22.44‰,δ~(13)C_(CO_2)值为-23.24‰~-9.68‰,表明有机流体参与了成矿作用。石英、方解石的H-O同位素结果表明具有海水和有机水混合的特征。可见,成矿流体具有两种流体混合的特征,一为蒸发海水与围岩反应所形成的盆地卤水,二为有机流体。推测矿区可能存在一个古油气藏,由于TSR生成一高硫气藏,为区内还原性有机流体的主要来源。当富含Pb、Zn等成矿物质的成矿流体运移至富含CH_4和H_2S的还原性流体的矿区角砾岩带时,两种流体混合,Pb、Zn等遇到H_2S发生反应而沉淀成矿,并伴生热液白云石等,形成了马元铅锌矿床。综上所述,我们认为马元矿床属MVT型铅锌矿床。 相似文献
19.
Study of the cross-stratification and other sedimentary structures in the Lower Greensand of the Weald, England, and Bas-Boulonnais, France, indicates that the sediments were deposited by the lateral migration of sand waves in a neritic sea. Comparison of the Lower Greensand sea with the modern North Sea was attempted. If those sediments were deposited as a result of tidal current similar to the present-day North Sea then the Lower Greensand shoreline could be deduced as running northwest-southeast, indication that the western part of the London Platform was submerged. 相似文献
20.
山西五台山区滹沱群变质玄武岩岩石学、地球化学特征及其成因意义 总被引：10，自引：0，他引：10
在野外地质调查的基础上,选取滹沱群豆村亚群底部四集庄组玄武岩、顶部青石村组玄武岩和东冶亚群中下部河边村组玄武岩,进行岩石学和地球化学研究。分析结果表明：玄武岩主量元素高TiO2、TFeO,低MgO,具有演化的基性岩浆的特征。稀土元素含量相对较高,具有弱—中等程度的轻稀土元素富集,中等程度的轻重稀土元素分异,轻微的Eu异常;玄武岩中Cr、Ni含量变化较大,但与Mg#具有很好的正相关性。微量元素配分图解中具有明显的Sr负异常,部分样品具有Nb、Ta和Ti负异常,无Zr、Hf负异常,与岛弧火山岩不同;同时Nb、Ta无分异,Zr/Hf值较高,具有板内玄武岩浆的特征。综合分析认为,滹沱群玄武岩可能形成于板内裂谷环境。在岩浆上升过程中发生橄榄石与尖晶石的分离结晶作用,同时不同程度地受到地壳的混染。 相似文献