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1.
华山岩体中,新生代抬长的裂变径迹证据   总被引:23,自引:3,他引:20       下载免费PDF全文
万景林  李齐 《地震地质》2000,22(1):53-58
对采自华山岩体不同高度的磷灰石样品进行裂变径迹分析,所得结果结合相关地质资料认为:(1)华山岩体抬升至少始新世;(2)华山主峰及北峰间可能发育一条对应于华山山前断裂的次级正断层,断距约340m;(3)据华山北峰样品研究,其各时段的平均抬升速率依次为29.26~25.05Ma,V=0.183mm/a;25.05~23.2 7Ma,V=0.152mm/a;23.27~20.59Ma,V=0.019mm/  相似文献   

2.
宽谷及宽谷阶地的形成与流域内的构造抬升活动密切相关。文中在考察阿尔金北缘断裂东段雁丹图与长草沟宽谷的基础上 ,结合古气候资料 ,探讨了晚更新世晚期以来两地河流阶地所反映的构造抬升。雁丹图自约 16 1kaBP以来发育了 3级堆积阶地 (T1,T2 与T3) ,并出露埋藏主要宽谷。 3级阶地面年龄分别约为 16 1ka ,12 8ka ,6 2ka ,反映了 3次构造抬升的存在 ,代表了 3次构造抬升发生的时间。雁丹图自约 16 1kaBP以来的构造抬升速率约为 4 8~ 4 5mm/a ;12 8~ 6 2kaBP间的抬升速率约 6 4mm/a ;6 2kaBP以来为 3 1mm/a。长草沟在 7kaBP以来有 4级阶地发育 (T3,T2 ,T′1与T1) ,均为堆积阶地 ,并出露埋藏宽谷。其中T3与T2 出露埋藏主要宽谷 ,T′1与T1出露埋藏次要宽谷。T3,T2与T′13级阶地的阶地面年龄分别约为 7ka ,3ka,2 5ka。 4级阶地反映 2次构造抬升 ,一次在约 7kaBP ,一次在 3kaBP左右。自 7 0kaBP以来长草沟的抬升速率约为 5 9mm/a ,在 7~ 3  相似文献   

3.
天山造山带晚古生代以来的隆升剥露过程与带内矿床形成后的保存潜力密切相关.本文报道了新的角闪石/斜长石Ar-Ar年龄和锆石/磷灰石(U-Th)/He年龄,为重建南天山中段地区欧西达坂岩体完整的构造-热演化历史提供年代学基础,结合前人研究成果分析了冷却速率及剥蚀速率变化特征,对南天山中段晚古生代以来的热演化历史及隆升剥蚀历史进行了探讨.同位素定年结果显示,角闪石Ar-Ar坪年龄为(382.6±3.6)Ma,斜长石Ar-Ar加权平均年龄为(265.8±4.9)Ma,锆石与磷灰石(U-Th)/He年龄分别为(185.8±4.3)和(31.1±2.9)Ma.热演化历史及模拟结果表明,南天山中段地区晚古生代至今的构造-热演化历史可以大致分为5个阶段:(1)志留纪末至晚泥盆世岩体平均冷却速率约7.84℃/Myr;(2)晚泥盆世至中二叠世末期,岩体的平均冷却速率约2.07℃/Myr;(3)中二叠世末到始新世中期岩体平均冷却速率降至0.68℃/Myr,此期间总体地质运动较为平缓;(4)新生代始新世期间(约46~35Ma)南天山中段地区发生了一期快速隆升剥蚀事件,岩体冷却速率突升至5.00℃/Myr,剥蚀量达到1.83km,平均剥蚀速率0.17mm/a;(5)始新世中期(约35Ma)至今,平均冷却速率约为1.14℃/Myr,隆升速度仍然较快,剥蚀量约为1.33km,平均剥蚀速率约0.04mm/a.新生代以来天山的剧烈隆起抬升受控于印亚碰撞的远程效应,远程作用在天山的响应具有一定的滞后效应.  相似文献   

4.
运用LA-ICP MS锆石U-Pb定年、角闪石和黑云母40Ar-39Ar定年、锆石和磷灰石裂变径迹(FT)分析等构造热年代学研究方法,探讨分析了鄂尔多斯盆地东缘紫金山侵入岩的热演化历史及其抬升冷却过程.紫金山侵入岩主要由次透辉二长岩和正长岩组成,锆石U-Pb测年给出的岩浆侵位-结晶年龄为136.7 Ma,角闪石和黑云母40Ar-39Ar测年获得的岩浆结晶-固结年龄集中在133.1~130.4 Ma,表明紫金山侵入岩主要形成于早白垩世的136.7~130.4 Ma.侵入岩T-t轨迹与磷灰石FT模拟热史路径综合揭示了鄂尔多斯盆地东缘紫金山侵入岩抬升冷却的三个构造热演化阶段:1) 136~120 Ma侵位岩浆结晶-固结阶段,岩体平均冷却速率高达52 ℃/Ma;2) 120~30 Ma岩体相对缓慢抬升冷却阶段,平均抬升冷却速率为2.5 ℃/Ma;3) 30 Ma以来岩体快速抬升冷却阶段,平均抬升冷却速率3.6 ℃/Ma,尤以近10 Ma以来的快速抬升冷却最为显著,抬升冷却速率接近7 ℃/Ma.结合区域构造动力学环境分析认为,鄂尔多斯盆地东缘的紫金山岩浆活动与华北克拉通早白垩世构造体制转换过程的大规模岩浆活动属于相同时期、统一构造作用的产物,早白垩世末期以来由慢到快的差异抬升过程主要受控于华北克拉通东部(古)太平洋体系与其西南部特提斯体系之间相互联合、彼此消长的构造作用.  相似文献   

5.
川滇地区现代地壳运动速度场和活动块体模型研究   总被引:35,自引:9,他引:35       下载免费PDF全文
吕江宁  沈正康  王敏 《地震地质》2003,25(4):543-554
通过分析中国地壳运动观测网络的GPS数据得到川滇地区地壳水平运动速度场 ,由此划分活动块体并分析其运动特征。结果表明 :相对欧亚板块 ,滇中、雅江和中甸次级块体的顺时针转动速率分别为 0 37°± 0 16°/Ma ,0 84°± 0 39°/Ma和 0 90°± 0 39°/Ma ,造成块体间跨木里弧形断裂带约 3mm/a的SN向挤压、丽江 -大理断裂带约 4mm/a的EW向拉张和理塘断裂带约 6mm/a的近EW向拉张。鲜水河断裂带左旋走滑速率 8~ 10mm/a ,安宁河 -则木河 -小江断裂带左旋走滑 5~6mm/a。龙门山断裂带没有明显的地壳消减 ,而断裂带西北约 15 0km处有一形变速度阶跃带 ,右旋走滑速率 4~ 5mm/a。阶跃带两侧的岷山块体和阿坝地区逆时针转动速率分别为 0 13°± 0 0 8°/Ma和0 5 3°± 0 19°/Ma。鲜水河 -小江断裂带以南、以西地区 ,青藏高原物质的E向挤出和重力滑塌造成川滇块体东移 ,在东部相对稳定的华南地块的阻挡下 ,川滇块体沿鲜水河 -小江断裂带由东转向南运动 ,从而引起川滇块体内部各次级块体的顺时针转动  相似文献   

6.
滇西临沧花岗岩基新生代剥蚀冷却的裂变径迹证据   总被引:13,自引:0,他引:13       下载免费PDF全文
为揭示临沧花岗岩基的剥蚀冷却历史,探讨印藏碰撞对滇西的影响,对6块临沧花岗岩基样品进行锆石和磷灰石裂变径迹测定,并利用模拟退火法对其中5块样品的磷灰石裂变径迹数据进行非线性热史反演,估算了不同时期的剥蚀量和抬升量. 结果表明,岩基自印藏陆陆碰撞以来经历了两期冷却事件,早期冷却速率仅5~10 ℃/Ma,晚期冷却速率明显增高,特别是近3 Ma以来的冷却速率达到16~20 ℃/Ma;两期总剥蚀厚度可达3300~3500 m. 分析表明冷却事件与印藏碰撞关系密切,早期冷却是在印藏碰撞影响下,临沧岩基卷入逆冲推覆运动而遭遇抬升、剥蚀的结果;晚期冷却则是上新世以来,特别是3Ma以来岩基经受整体的强烈抬升、剥蚀的结果,该期构造抬升量约为672~1263 m;裂变径迹资料还揭示印藏碰撞先影响南部岩体,随后才波及到岩基中北段.  相似文献   

7.
通过卫、航片解释、野外活断层调查实测与年龄测试分析发现 :斜切中国西南“川滇菱块”的横向构造———丽江 -小金河断裂为一断面高角度倾向NW的逆左旋走滑型活动断裂。通过盆地复位和同沉积盆地的位错分析 ,确定了该断裂第四纪以来的水平位错量为 7 4~ 7 6km。断裂两侧差异隆升及相应堆积物的分析表明 ,中更新世以来 ,断裂垂直位错量达 5 0 0~ 70 0m以上。由此计算得到丽江 -小金河断裂第四纪和中更新世以来的水平与垂直位错速率分别为 3 7~ 3 8mm/a和 1 0~1 5mm/a。水平位错及相关年龄测试资料表明 ,该断裂晚更新世以来的平均位错速率在 2 6~4 0mm/a之间 ,中值为 3 3mm/a ;全新世以来的平均位错速率在 2 5~ 5 0mm/a之间 ,中值为3 5mm/a。第四纪各时段以来滑动速率的较好相似性表明 ,长期以来 ,该断裂的活动具相对稳定性和活动地块边界的持久性  相似文献   

8.
阳新岩体是个由三期侵位形成的复式岩体, 其中作为主体的第二期占了整个岩体出露面积的90%以上, 其锆石U-Pb SHRIMP年龄为134±2 Ma, 为典型的燕山晚期侵入体, 而不是早先认为的属燕山早期. 该岩体内主要暗色矿物角闪石和黑云母都以富镁为特征, 表明其母岩浆来源深, 与地幔具有近缘性. 地球化学上该岩体以高铝(Al2O3=15.92%~16.38%)、偏碱(Na2O+K2O为6.95%~7.37%)、富钠(Na2O/K2O为1.47~1.94)、高Sr(816~897 μg/g)、富集强不相容元素Rb, U, Th, K及轻稀土元素, 而亏损重稀土元素和Y为特征, 轻、重稀土元素的分馏程度强((La/Yb) N = 17.83 ~20.86), 地球化学的总体特征虽与典型的埃达克岩有所差别, 但非常类似. 推测岩浆的形成可能与大别山造山带山根拆沉后底侵玄武岩的部分熔融有关. 该岩体自固结至今大约抬升了5 km, 抬升速率仅约0.04 mm/a, 远低于造山带内晚中生代的剥蚀程度, 只是到了新生代, 两地的抬升剥蚀速率才可能相近.  相似文献   

9.
通过分析阿尔金断裂带西段车尔臣河出山口以西 85°~ 86°E的高精度SPOT卫星影像 ,结合野外考察和年代学研究 ,对阿尔金断裂带西段 3个典型走滑断层的断错地貌进行了研究。在库拉木拉克 ,阿尔金断裂带西段自 (6 0 2± 0 4 7)kaBP以来的左旋滑动速率为 (11 6± 2 6 )mm/a ,自 (15 6 7± 1 19)kaBP以来的左旋滑动速率为 (9 6± 2 6 )mm/a ;阿羌牧场附近 ,自 (2 0 6± 0 16 )kaBP以来的左旋滑动速率为 (12 1± 1 9)mm/a ;达拉库岸萨依附近 ,自 (4 91± 0 39)kaBP以来的左旋滑动速率为(12 2± 3 0 )mm/a。由此得到阿尔金断裂带全新世以来的平均滑动速率约为 (11 4± 2 5 )mm/a。以阿尔金断裂带走向N75°E计算 ,阿尔金断裂带西段左旋走滑所吸收的青藏高原SN向缩短速率为 (3 0±0 6 )mm/a  相似文献   

10.
新疆南天山亚肯背斜晚更新世以来的隆起和缩短   总被引:5,自引:7,他引:5       下载免费PDF全文
野外考察见到亚肯背斜区发育 3级主要地貌面 ,在第 2级和第 1级地貌面 (冲洪积扇 )之下采集了堆积物的热释光样品 ,测年结果分别为距今 3 96~ 4 36万年和 0 78万年 ,区域地貌对比研究认为 ,第 2级地貌面被废弃的时代为距今 4万年至 1 2~ 1 3万年 ,第 1级地貌面被废弃的时代为距今 0 78万年之后。横跨背斜不同部位地貌面的地形剖面表明 ,第 2级地貌面形成以来褶皱隆起高度达 6 0m ,第 1级地貌面褶皱隆起高度为 2 0m。地震反射剖面显示 ,亚肯背斜区滑脱面深度约7km ,由平衡地质剖面法得到第 2和第 1级地貌面形成以来褶皱的缩短量分别为 4 7m和 17 9m。第 2级地貌面形成以来褶皱的隆起和缩短速率分别为 1 5~ 5mm/a和 1 2~ 3 9mm/a,第 1级地貌面形成以来褶皱隆起和缩短速率分别为 2 5 6mm/a和 2 2 9mm/a  相似文献   

11.
依据钻孔系统稳态测温、静井温度资料与实测热导率数据分析了柴达木盆地地温场分布特征,建立了柴达木盆地热导率柱,新增了17个大地热流数据.柴达木盆地现今地温梯度介于17.1~38.6℃·km-1,平均为28.6±4.6℃·km-1,大地热流介于32.9~70.4mW·m-2,平均55.1±7.9mW·m-2.盆地不同构造单元地温场存在差异,昆北逆冲带、一里坪坳陷属于"高温区",祁南逆冲带属于"中温区",三湖坳陷、德令哈坳陷及欧龙布鲁克隆起属于"低温区",盆地现今地温场分布特征受控于地壳深部结构、盆地构造等因素.以现今地温场为基础,采用磷灰石、锆石裂变径迹年龄分布特征定性分析与径迹长度分布数据定量模拟相结合,研究了柴达木盆地晚古生代以来的沉积埋藏、抬升剥蚀和热演化史,并结合区域构造背景,对柴达木盆地构造演化过程进行了探讨,研究表明柴达木盆地晚古生代以来经历了六期(254.0—199 Ma,177—148.6 Ma,87—62 Ma,41.1—33.6 Ma,9.6—7.1 Ma,2.9—1.8 Ma)构造运动,六期构造事件与研究区构造演化的动力学背景相吻合.其中白垩纪末期(87—62 Ma)的构造事件导致了柴达木盆地东部隆升并遭受剥蚀,欧龙布鲁克隆起形成雏形,柴达木盆地北缘在弱挤压环境下形成坳陷盆地;中新世末的两期构造事件(9.6—7.1 Ma和2.9—1.8 Ma)使柴达木盆地遭受强烈挤压,盆地快速隆升,构造变形强烈,基本形成现今的构造面貌.  相似文献   

12.
Wanming  Yuan  Jun  Deng  Qiugen  Zheng  Jinquan  Dong  Zengkuan  Bao  Paul R.  Eizenhoefer  Xiaotong  Xu  Zhixin  Huang 《Island Arc》2009,18(3):488-495
Apatite fission track dating of five samples from Cenozoic volcanic strata in the Nimu District in the southern Gangdese Terrane exhibits single population grain ages with a single mean age and associated central ages ranging from 6.8 ± 0.6 Ma to 9.7 ± 1.2 Ma. Mean track lengths are between 12.9 ± 1.7 µm and 14.2 ± 2.3 µm with a single peak characteristic of a single thermal event. The newly documented ages coincide well with the age of high sedimentation rates in the North Tibet Basin that resulted from a 9–5 Ma compressional event. Track length modeling allows three stages to be identified in the sample cooling. The first stage (12–8 Ma) records a period of relative stability with little, if any, cooling at temperatures of 120–110°C suggesting this region had low relief. The second stage (8–2 Ma) reflects rapid cooling with temperatures decreasing from ∼110°C to surface temperatures of ∼15°C. This stage can be related to far-field effects of the Himalayan collision, which probably generated the surface uplift and relief that defines the present-day Gangdese Mountains. The mean uplift rate of this period is estimated to be 1.41–0.95 mm/y with total uplift reaching ∼5900 m. The final stage is related to surface evolution since the Pliocene.  相似文献   

13.
The Xigaze fore-arc basin is adjacent to the Indian plate and Eurasia collision zone. Understanding the erosion history of the Xigaze fore-arc basin is significant for realizing the impact of the orogenic belt due to the collision between the Indian plate and the Eurasian plate. The different uplift patterns of the plateau will form different denudation characteristics. If all part of Tibet Plateau uplifted at the same time, the erosion rate of exterior Tibet Plateau will be much larger than the interior plateau due to the active tectonic action, relief, and outflow system at the edge. If the plateau grows from the inside to the outside or from the north to south sides, the strong erosion zone will gradually change along the tectonic active zone that expands to the outward, north, or south sides. Therefore, the different uplift patterns are likely to retain corresponding evidence on the erosion information. The Xigaze fore-arc basin is adjacent to the Yarlung Zangbo suture zone. Its burial, deformation and erosion history during or after the collision between the Indian plate and Eurasia are very important to understand the influence of plateau uplift on erosion. In this study, we use the apatite fission track(AFT)ages and zircon and apatite(U-Th)/He(ZHe and AHe)ages, combined with the published low-temperature thermochronological age to explore the thermal evolution process of the Xigaze fore-arc basin. The samples' elevation is in the range of 3 860~4 070m. All zircon and apatite samples were dated by the external detector method, using low~U mica sheets as external detectors for fission track ages. A Zeiss Axioskop microscope(1 250×, dry)and FT Stage 4.04 system at the Fission Track Laboratory of the University of Waikato in New Zealand were used to carry out fission track counting. We crushed our samples finely, and then used standard heavy liquid and magnetic separation with additional handpicking methods to select zircon and apatite grains. The new results show that the ZHe age of the sample M7-01 is(27.06±2.55)Ma(Table 2), and the corresponding AHe age is(9.25±0.76)Ma. The ZHe and AHe ages are significantly smaller than the stratigraphic age, indicating suffering from annealing reset(Table 3). The fission apatite fission track ages are between(74.1±7.8)Ma and(18.7±2.9)Ma, which are less than the corresponding stratigraphic age. The maximum AFT age is(74.1±7.8)Ma, and the minimum AFT age is(18.7±2.9)Ma. There is a significant north~south difference in the apatite fission track ages of the Xigaze fore-arc basin. The apatite fission track ages of the south part are 74~44Ma, the corresponding exhumation rate is 0.03~0.1km/Ma, and the denudation is less than 2km; the apatite fission track ages of the north part range from 27 to 15Ma and the ablation rate is 0.09~0.29km/Ma, but it lacks the exhumation information of the early Cenozoic. The apatite(U-Th)/He age indicates that the north~south Xigaze fore-arc basin has a consistent exhumation history after 15Ma. The results of low temperature thermochronology show that exhumation histories are different between the northern and southern Xigaze fore-arc basin. From 70 to 60Ma, the southern Xigaze fore-arc basin has been maintained in the depth of 0~6km in the near surface, and has not been eroded or buried beyond this depth. The denudation is less than the north. The low-temperature thermochronological data of the northern part only record the exhumation history after 30Ma because of the young low-temperature thermochronological data. During early Early Miocene, the rapid erosion in the northern part of Xigaze fore-arc basin may be related to the river incision of the paleo-Yarlungzangbo River. The impact of Great Count Thrust on regional erosion is limited. The AHe data shows that the exhumation history of the north-south Xigaze fore-arc basin are consistent after 15Ma. In addition, the low-temperature thermochronological data of the northern Xigaze fore-arc basin constrains geographic range of the Kailas conglomerate during the late Oligocene~Miocene along the Yarlung Zangbo suture zone. The Kailas Basin only develops in the narrow, elongated zone between the fore-arc basin and the Gangdese orogenic belt. The southern part of the Xigaze fore-arc basin has been uplifted from the sea level to the plateau at an altitude of 4.2km, despite the collision of the Indian plate with the Eurasian continent and the late fault activity, but the plateau has been slowly denuded since the early Cenozoic. The rise did not directly contribute to the accelerated erosion in the area, which is inconsistent with the assumption that rapid erosion means that the orogenic belt begins to rise.  相似文献   

14.
鲜水河断裂是青藏高原东南缘的一条北西向大型左旋走滑断裂,其南东段逐渐向南偏转,并与近南北向的安宁河断裂相接,在两个断裂相接处西侧耸立着海拔7556 m高的贡嘎山.磷灰石裂变径迹(AFT)测试可知,贡嘎山及其邻区12个样品的年龄分布在0.2±0.1 Ma~2.7±0.7 Ma之间,平均径迹长度在13.64~15.19 μm之间,表明贡嘎山及其邻区第四纪时期一直处于快速剥蚀状态.结合前人在此地区的低温热年代研究成果,揭示出两个现象:(1)贡嘎山岩体及鲜水河断裂与龙门山断裂所夹的三角区域为快速隆升区域,而其西侧、北侧的高原腹地的隆升速率远低于这两个区域;(2)贡嘎山岩体从北向南隆升速率逐渐变大,其最南端1 Ma以来的隆升速率超过3.3±0.8 mm/a.这些现象表明青藏高原在整体横向挤出、缓慢隆升的基础上,还存在着一些特殊的局部快速隆升区域.通过对川滇地块水平运动的矢量分解,我们认为贡嘎山花岗岩体是鲜水河断裂至安宁河断裂间挤压弯曲段吸收、转换川滇地块南东向水平运动导致局部快速隆升的产物,在这一过程中,由于垂直于断裂的挤压分量从北到南逐渐增大,导致了岩体从北往南的隆升速率逐渐增大.  相似文献   

15.
Abstract Apatite and zircon fission track ages from Ryoke Belt basement in northeast Kyushu show late Cretaceous, middle to late Eocene, middle Miocene and Quaternary groupings. The basement cooled through 240 ± 25°C, the closure temperature for fission tracks in zircon, mainly during the interval 74-90 Ma as a result of uplift and denudation, the pattern being uniform across northeast Kyushu. In combination with published K-Ar ages and the Turonian-Santonian age of sedimentation in the Onogawa Basin, active suturing along the Median Tectonic Line from 100-80 Ma, at least, is inferred. Ryoke Belt rocks along the northern margin of Hohi volcanic zone (HVZ) cooled rapidly through ∼100°C to less than 50°C during the middle Eocene to Oligocene, associated with 2.5-3.5 km of denudation. The timing of this cooling follows peak heating in the Eocene-Oligocene part (Murotohanto subbelt) of the Shimanto Belt in Muroto Peninsula (Shikoku) inferred previously, and coincides with the 43 Ma change in convergence direction of the Pacific-Eurasian plate and the demise of the Kula-Pacific spreading centre. Ryoke Belt rocks along the southern margin of HVZ have weighted mean apatite fission track ages of 15.3 ± 3.1 Ma. These reset ages are attributed to an increase in geothermal gradient in the middle Miocene combined with rapid denudation and uplift of at least 1.4 km. These ages indicate that heating of the overriding plate associated with the middle Miocene start of subduction of hot Shikoku Basin lithosphere extended into the Ryoke Belt in northeast Kyushu. Pleistocene apatite fission track ages from Ryoke Belt granites at depth in the centre of HVZ are due to modern annealing in a geothermal environment.  相似文献   

16.
Five samples from a biotite-hornblende granodiorite phase of the 42.5 Ma Quxu pluton, Gangdese batholith, southern Tibet, have been collected at 250 m vertical intervals. Biotite from these rocks yields monotonically decreasing40Ar/39Ar isochron ages with decreasing elevation of 26.8 ± 0.2, 23.3 ± 0.5, 19.7 ± 0.3, 18.4 ± 0.4,and17.8 ± 0.1Ma (Tc = 335°C). Coexisting K-feldspars have virtually identical minimum apparent40Ar/39Ar ages of 17.0 ± 0.4Ma (Tc = 285°C). These data indicate parts of southern Tibet experienced a pulse of uplift in the early Miocene with the rate of uplift rising from 0.07 to 4.4 mm/year in the interval 20 to 17 Ma. An apatite fission track age of 9.9 ± 0.9Ma from this locality constrains the average uplift rate at this site to about 0.81 mm/year between 17 and 9.9 Ma and 0.30 mm/year from 9.9 Ma to present. K-feldspar from the Dagze granite, 30 km to the east, near Lhasa, yields a minimum apparent40Ar/39Ar age of 35.9 ± 0.9Ma (Tc = 227°C) which indicates an average uplift rate there of 0.21 mm/year since then. The marked pulse of uplift of the Quxu granodiorite and the difference in uplift history between the Dagze and Quxu plutons suggests southern Tibet has experienced discrete pulses of uplift variable in both space and time. These data are not consistent with models which require a large proportion of uplift of the Tibetan plateau to have occurred in the last 2 Ma. The data support the suggestion that convergence between India and Asia was largely accommodated by tectonic escape during the opening of the South China Sea 32 to 17 Ma ago and permit distributed shortening as a mechanism for crustal thickening and uplift of this part of the Tibetan plateau subsequent to 20 Ma.  相似文献   

17.
本文通过背斜褶皱变形与低温热年代学年龄(磷灰石和锆石(U-Th)/He、磷灰石裂变径迹)端元模型研究,约束低起伏度、低斜率地貌特征的四川盆地南部地区新生代隆升剥露过程.四川盆地南部沐川和桑木场背斜地区新生代渐新世-中新世发生了相似的快速隆升剥露过程(速率为~0.1 mm/a、现今地表剥蚀厚度1.0~2.0 km),反映出盆地克拉通基底对区域均一性快速抬升冷却过程的控制作用.川南沐川地区磷灰石(U-Th)/He年龄值为~10-28.6 Ma, 样品年龄与古深度具有明显的线性关系,揭示新生代~10-30 Ma以速率为0.12±0.02 mm/a的稳态隆升剥露过程.桑木场背斜地区磷灰石裂变径迹年龄为~36-52 Ma,古深度空间上样品AFT年龄变化不明显(~50 Ma)、且具有相似的径迹长度(~12.0 μm).磷灰石裂变径迹热演化史模拟表明桑木场地区经历三个阶段热演化过程:埋深增温阶段(~80 Ma以前)、缓慢抬升冷却阶段(80-20 Ma)和快速隆升剥露阶段(~20 Ma-现今),新生代隆升剥露速率大致分别为~0.025 mm/a和~0.1 mm/a.新生代青藏高原大规模地壳物质东向运动与四川盆地克拉通基底挤压,受板缘边界主断裂带差异性构造特征控制造就了青藏高原东缘不同的边界地貌特征.  相似文献   

18.
Fission track analysis of apatites from basement rocks of the Wright Valley in southern Victoria Land provides information about the timing, the amount and hence the rate of uplift of the Transantarctic Mountains in this area. Apatite ages increase systematically with elevation, and a pronounced break in the age versus elevation profile has been recognised at about 800 m on Mt. Doorly near the mouth of Wright Valley. The apatite age of about 50 Ma at this point approximates the time at which uplift of the mountain range began. Samples lying above the break in slope lay within the apatite fission track annealing zone prior to uplift, during a Cretaceous to Early Cenozoic period of relative thermal and tectonic stability. At the lower elevations samples had a zero apatite fission track age before the onset of rapid uplift and have track length distributions indicating rapid cooling. Some 4.8–5.3 km of uplift are estimated to have occurred at an average rate of about 100 ± 5m/Ma since uplift began. From the total stratigraphic thickness known above the uplifted apatite annealing zone it can be estimated that the Late Cretaceous/Early Cenozoic thermal gradient in the area was about 25–30°C/km.The occurrence and pattern of differential uplift across the Transantarctic Mountains can be estimated from the vertical offsets of different apatite fission track age profiles sampled across the range. These show the structure of the mountain range to be that of a large tilt block, dipping gently to the west under the polar ice-cap and bounded by a major fault zone on its eastern side. Offset dolerite sills at Mt. Doorly show the mountain front to be step-faulted by 1000 m or more down to the McMurdo Sound coast from an axis of maximum uplift just inland from Mt. Doorly.  相似文献   

19.
合肥盆地构造热演化的裂变径迹证据   总被引:12,自引:0,他引:12       下载免费PDF全文
运用裂变径迹分析方法,探讨分析了合肥盆地中新生代的构造热演化特征. 上白垩统和古近系下段样品的磷灰石裂变径迹(AFT)数据主体表现为靠近部分退火带顶部温度(±65℃)有轻度退火,由此估算晚白垩世至古近纪早期合肥盆地断陷阶段的古地温梯度接近38℃/km,高于盆地现今地温梯度(275℃/km).下白垩统、侏罗系及二叠系样品的AFT年龄(975~25Ma)和锆石裂变径迹(ZFT)年龄(118~104Ma)均明显小于其相应的地层年龄,AFT年龄-深度分布呈现冷却型曲线形态,且由古部分退火带、冷却带或前完全退火带及其深部的今部分退火带组成,指示早白垩世的一次构造热事件和其随后的抬升冷却过程. 基于AFT曲线的温度分带模式和流体包裹体测温数据的综合约束,推算合肥盆地早白垩世走滑压陷阶段的古地温梯度接近67℃/km. 径迹年龄分布、AFT曲线拐点年龄和区域抬升剥蚀时间的对比分析结果表明,合肥盆地在早白垩世构造热事件之后的104Ma以来总体处于抬升冷却过程,后期快速抬升冷却事件主要发生在±55Ma.  相似文献   

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