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1.
冈底斯弧前区域地层沉积记录,对新特提斯洋消亡和印度-亚洲碰撞过程的研究具有十分重要的意义。位于西藏南部札达地区的达机翁组,北邻冈底斯岩浆弧,南靠雅鲁藏布江缝合带。岩石组成主要包括砾岩、岩屑砂岩、泥页岩和灰岩等。沉积环境分析认为达机翁组形成于扇三角洲相环境。火山灰锆石U-Pb定年、碎屑锆石最年轻年龄以及底栖有孔虫化石组合共同约束达机翁组的形成时代为晚白垩世-始新世早期(即ca.73～49Ma)。物源区分析结果表明达机翁组物源类似于区域上分布的日喀则弧前盆地沉积,直接以北侧冈底斯岩浆弧为主要物质源区。通过与区域弧前沉积对比,为冈底斯弧前盆地海相地层时代提供制约,结果显示新特提斯洋在亚洲大陆南缘的弧前海退存在东西方向上的穿时性,即海水自东向西逐渐退出,并最终在～49Ma退出冈底斯-拉达克弧前区域。 相似文献
2.
针对泽当西郊贡巴日北坡剖面罗布莎群砾岩下部厚约15m的火山岩夹层进行锆石定年,测试结果表明,该火山岩LAICP-MS锆石U-Pb年龄为18.7±0.2Ma,罗布莎群下伏花岗岩LA-ICP-MS锆石U-Pb年龄为29.9±0.4Ma。据此认为,罗布莎群砾岩初始沉积时代约为20Ma前。火山岩的出现表明,中新世布尔迪加尔期罗布莎群发育一期火山活动,结合前人研究认为,沿雅鲁藏布江结合带的狭长范围内自西向东发育一期火山活动,代表雅鲁藏布江缝合带的一次活化,其时空分布特征与冈底斯带中新世钾质—超钾质火山活动具有显著的相似性。 相似文献
3.
针对泽当西郊贡巴日北坡剖面罗布莎群砾岩下部厚约15m的火山岩夹层进行锆石定年,测试结果表明,该火山岩LA-ICP-MS 锆石U-Pb年龄为18.7±0.2Ma,罗布莎群下伏花岗岩LA-ICP-MS锆石 U-Pb年龄为29.9±0.4Ma。据此认为,罗布莎群砾岩初始沉积时代约为20Ma前。火山岩的出现表明,中新世布尔迪加尔期罗布莎群发育一期火山活动,结合前人研究认为,沿雅鲁藏布江结合带的狭长范围内自西向东发育一期火山活动,代表雅鲁藏布江缝合带的一次活化,其时空分布特征与冈底斯带中新世钾质—超钾质火山活动具有显著的相似性。 相似文献
4.
黑龙江省饶河县石场一带分布的跃进山杂岩为一套富含晚三叠世化石的海陆交互相沉积地层.砾岩样品中的LA-ICP-MS锆石U-Pb测年结果显示,样品中的碎屑锆石年龄谱具有4组年龄,分别为800 Ma以上、500 Ma、251~284 Ma和219~222 Ma.前三者与佳木斯地块中的热事件年龄完全一致,表明其沉积物源主要来自佳木斯地块;后者为砾岩最小年龄组,大致可将这组最小年龄视为这套砾岩的沉积时代下限,与西侧松辽地块东缘的张广才岭地区广泛分布的210~228 Ma的晚三叠世早期花岗岩基本一致,说明具有最小年龄组的碎屑锆石可能来自松辽地块东部.碎屑锆石年龄及其源区特征表明,在晚三叠世之前,跃进山增生杂岩已经就位在佳木斯地块东缘,并成为佳木斯地块东部大陆边缘的一部分. 相似文献
5.
黑龙江省饶河县石场一带分布的跃进山杂岩为一套富含晚三叠世化石的海陆交互相沉积地层.砾岩样品中的LA-ICP-MS锆石U-Pb测年结果显示，样品中的碎屑锆石年龄谱具有4组年龄，分别为800 Ma以上、500 Ma、251~284 Ma和219~222 Ma.前三者与佳木斯地块中的热事件年龄完全一致，表明其沉积物源主要来自佳木斯地块；后者为砾岩最小年龄组，大致可将这组最小年龄视为这套砾岩的沉积时代下限，与西侧松辽地块东缘的张广才岭地区广泛分布的210~228 Ma的晚三叠世早期花岗岩基本一致，说明具有最小年龄组的碎屑锆石可能来自松辽地块东部.碎屑锆石年龄及其源区特征表明，在晚三叠世之前，跃进山增生杂岩已经就位在佳木斯地块东缘，并成为佳木斯地块东部大陆边缘的一部分. 相似文献
6.
冈底斯中部广泛发育的松多岩组因缺少化石依据,其沉积时代一直存在争议,严重制约了对冈底斯古生代构造演化的认识.在详细野外地质调查基础上,利用LA-ICP-MS锆石U-Pb同位素定年对松多岩组中变质砂岩进行了锆石U-Pb同位素测定,获得变质砂岩中最小碎屑锆石年龄值为316 Ma,时代为晚石炭世,代表了松多岩组形成时代的下限.通过碎屑锆石年龄示踪和区域对比研究,松多岩组物源很可能来自拉萨地块内部(南拉萨地块和北拉萨地块),可能是松多古特提斯洋初始洋盆的沉积记录.研究区松多岩组沉积时代下限的厘定,进一步完善了该区晚古生代地层系统,对冈瓦纳大陆北缘晚石炭世－早二叠世岩相古地理研究具有重要意义. 相似文献
7.
雅鲁藏布江缝合带是新特提斯洋俯冲消亡的残余,记录了新特提斯洋打开—闭合的全过程。本文以雅鲁藏布江缝合带西段仲巴地区南侧的纳久混杂岩为研究对象,进行了详细的放射虫年代学,砂岩碎屑锆石U-Pb同位素年代学以及碎屑组分统计研究。我们的数据表明,纳久混杂岩中硅质岩含有大量保存较好的放射虫化石,包含Pseudodictyomitra carpatica带典型分子,根据放射虫时代组合确定其时代为早Barremian阶;混杂岩中砂岩岩块主要为岩屑砂岩,不同样品碎屑锆石得出的最大沉积年龄介于95～73 Ma之间。碎屑锆石U-Pb年龄源区分析表明,碎屑物质来自北侧的冈底斯岩浆弧和拉萨地体。纳久混杂岩南侧的砂岩沉积时代为早白垩世,碎屑锆石U-Pb年龄源区表明具有典型的特提斯喜马拉雅特征。我们的数据表明,纳久混杂岩基质时代为早白垩世,砂岩岩块时代为晚白垩世,与北侧的早白垩世蛇绿岩共同组成了白垩纪的增生楔,随着印度与欧亚大陆的碰撞仰冲到特提斯喜马拉雅之上。 相似文献
8.
喜马拉雅造山带北缘的大反转逆冲断层(GCT)位于印度-亚洲的碰撞边界,平行雅鲁藏布江缝合带展布,向北逆冲使特提斯喜马拉雅地体向北叠覆在冈底斯地体之上。大反转逆冲断裂制约了中新世Kailas式系列磨拉石盆地(Kailas、秋乌、大竹曲、罗布莎以及朗县)的发育,自西向东磨拉石盆地中砾石变形逐渐增强。本文通过GCT东段"罗布莎-郎县砾岩"的研究,获得罗布莎-朗县变形砾岩中的碎屑锆石的沉积上限年龄为早渐新世(28.7~29.1Ma)。罗布莎-郎县砾岩具有基质糜棱岩化、发育地震化石假熔岩和向北剪切指向的特征,表明其经历了受GCT断裂控制的砾岩盆地在浅部形成、插入10~15km深部并受地震影响形成假熔岩,然后折返到地表的过程。 相似文献
9.
唐王陵昭陵组砾岩碎屑锆石U-Pb年代学分析 总被引：5，自引：0，他引：5
唐王陵砾岩的时代归属及其沉积物源环境一直是鄂尔多斯盆地南缘新元古界-下古生界沉积地层学研究和油气地质勘探备受关注且长期存有争议的问题。采用LA-ICP-MS锆石U-Pb年代学方法,定量分析探讨了唐王陵昭陵组砾岩的时代归属和物质来源。结果表明:昭陵组砾岩的碎屑锆石U-Pb测年数据主要分布在744~943 Ma(n=6)、1 005~1 412 Ma (n=15)、1 449~2 209 Ma(n=255)和2 274~2 696 Ma (n=49)四个年龄区间,相应的峰值年龄集中在815 Ma、1 182 Ma、1 811 Ma、2 454 Ma,最年轻的单颗粒锆石年龄为744 Ma。它与盆地西缘贺兰山地区震旦纪正目观组的碎屑锆石U-Pb年龄谱非常相似,但明显有别于盆地南缘晚奥陶世平凉组,尤其是缺少平凉组碎屑锆石主要集中在454 Ma的峰值年龄,由此限定昭陵组砾岩的沉积时代主要发生在晚前寒武纪或震旦纪。锆石U-Pb年龄谱的区域对比揭示,昭陵组砾岩的沉积物源主要来自于华北(鄂尔多斯)地块的古元古代变质基底岩系和其南缘北秦岭构造带的晚前寒武纪岩浆岩-变质杂岩,呈现稳定地块与活动带双向混合物源特征。 相似文献
10.
鄂尔多斯盆地西南缘崆峒山组砾岩中的碎屑锆石LA-ICP-MS U-Pb定年及其构造意义 总被引：2，自引：0，他引：2
甘肃省平凉崆峒山地区是崆峒山组地层命名所在地,该套地层主要由大套红色砾岩层组成,通常称为崆峒山组砾岩。长期以来,对崆峒山组砾岩的成因、形成时代和物源存在争议。本文选取崆峒山组砾岩层中的3块砾石为研究对象,运用LA-ICP-MS方法对砾石样品中的碎屑锆石进行了年代学研究。结果表明,崆峒山组砾岩碎屑锆石年龄谱可分为380~479Ma、561~1198Ma、1285~1982Ma、2319~2612Ma和2714~2764Ma共5个年龄区间。依据崆峒山组砾岩碎屑锆石年龄谱分布特征,以及前人研究成果,认为崆峒山组砾岩的主要物源来源于秦祁造山带,少量来源于阿拉善地块和鄂尔多斯地块。崆峒山组砾岩的沉积时代为中三叠世至晚三叠世,崆峒山组砾岩是秦祁造山带造山过程的沉积响应,而非板内造山带的产物。 相似文献
11.
达金海相碎屑岩出露于西藏冈仁波齐峰山脚下,长期以来,该套岩石与冈底斯砾岩一起被视为印度-亚洲板块碰撞形成的陆相磨拉石.该套岩石组合是由凝灰质粉砂岩、杂砂岩、含砾杂砂岩和砾岩组成的一套深海-浅海相沉积组合.杂砂岩、砾岩碎屑组成与地球化学组成研究表明,该套岩石组合的形成与岛弧的发展密切相关,源区大地构造背景以岛弧为主,但也存在被动大陆边缘和碰撞构造带（蛇绿混杂带）两个不同构造背景的源区.区域上,在该套岩石组合的北侧存在着冈底斯岛弧带,南侧为雅鲁藏布蛇绿混杂带.这些特征共同表明,达金海相碎屑岩是西藏雅鲁藏布缝合带与冈底斯岛弧带之间的日喀则弧前盆地的一部分. 相似文献
12.
伊朗Kashan地区古近系库姆组层序地层及盆地演化特征 总被引：3，自引：1，他引：3
库姆组沉积时期伊朗Kashan地区为中伊朗盆地库姆盆地东南方向的弧后边缘海盆地,以浅海相的碳酸盐岩和碎屑岩沉积为主.受构造运动与全球海平面旋回变化控制,大部分地区的库姆组形成了5个三级层序S1～S5,上覆上红组底部蒸发岩层,在这5个三级层序之下,盆地沉降中心位置还可见S0a和S0b层序.对格架中层序地层特征的动态演化分析后认为,Kashan地区在库姆组及其上、下地层沉积时期经历了7次重要的地层演化阶段:低水位充填期、初次海侵期、沉降充填期、孤立泻湖期、再次海侵期、构造抬升期、完全孤立期. 相似文献
13.
Cenozoic conglomerates are exposed discontinuously along the length of the Yarlung Tsangpo suture zone on the southern margin of the Gangdese arc. These conglomerates (the “Gangdese Conglomerates” herein) record a crucial stage in the uplift and erosion histories of the southern Tibet after the initial India–Asia collision. In the Mt. Kailas area, the Gangdese Conglomerates strata consist of multiple sedimentary cycles and each cycle is a fining-upward sequence that was deposited by alluvial fan, braided-river and delta systems. Whereas in the Xigaze area, the Gangdese Conglomerates strata comprise a coarsening-upward sequence that was deposited by delta, braided-river and alluvial fan systems. Based on the detrital and igneous zircon U–Pb ages, the depositional ages of the Gangdese Conglomerates are late Oligocene to early Pliocene (ca. 26–5 Ma) in the Mt. Kailas area, late Oligocene to middle Miocene (ca. 26–15 Ma) in the Xigaze area, and late Oligocene to early Miocene (ca. 26–19 Ma) in the Zedong area. Paleocurrent measurements and provenance data (i.e., conglomerate clast composition, sandstone petrology and detrital zircon age) indicate that the initial detritus of the Gangdese Conglomerates were entirely derived from the north (mainly from the Gangdese arc). Sediment resulting from denudation to the south (the Xigaze forearc basin, the Yarlung Tsangpo suture zone and the northern margin of the Indian plate) first appeared by the early Miocene (ca. 19 Ma) and subsequently increased in abundance gradually. Our new results, together with previous data from the Xigaze area, reveal 3 major stages in the evolution of the Yarlung Tsangpo River system: (1) the southward-flowing stage (ca. 26–19 Ma) featured southward-draining transverse rivers that transported materials from the Gangdese arc southward. Southward paleocurrents in the Gangdese Conglomerates indicate a northern source. (2) The westward-flowing stage (ca. 19–15 Ma) developed due to the uplift of the suture zone and Tethys Himalaya to the south. Northward-draining rivers began to develop, and lakes resembling a string of beads formed and finally connected together, initiating the westward-flowing paleo-Yarlung Tsangpo River. Westward paleoflows were recorded in the Gangdese Conglomerates. (3) The eastward-flowing stage (ca. 15 Ma–present) resulted from differential uplift and denudation of the southern Tibet, which reversed the direction of the young Yarlung Tsangpo River by ca. 15 Ma. The deposition of the Gangdese Conglomerates was controlled by eastward paleoflows. At this point, the modern eastward-flowing Yarlung Tsangpo River system was established. 相似文献
14.
Late Cretaceous to early Miocene deposits of the Carpathian foreland basin in southern Moravia 总被引：1，自引：1，他引：0
The Late Cretaceous to Early Miocene strata of the Carpathian foreland basin in southern Moravia (Czech Republic) are represented
by a variety of facies which reflects the evolution of the foreland depositional system. However, because of the intensive
deformation and tectonic displacement and the lack of diagnostic fossils the stratigraphic correlation and paleogeographic
interpretation of these strata are difficult and often controversial. In order to better correlate and to integrate them into
a broader Alpine–Carpathian foreland depositional system, these discontinuous and fragmentary strata have been related to
four major tectonic and depositional events: (a) formation of the Carpathian foreland basin in Late Cretaceous which followed
the subduction of Tethys and subsequent deformation of the Inner Alps-Carpathians; (b) Middle to Late Eocene transgression
over the European foreland and the Carpathian fold belt accompanied by deepening of the foreland basin and deposition of organic-rich
Menilitic Formation; (c) Late Oligocene to Early Miocene (Egerian) uplifting and deformation of inner zones of the Carpathian
flysch belt and deposition of Krosno-type flysch in the foreland basin; and (d) Early Miocene (Eggenburgian) marine transgression
and formation of late orogenic and postorogenic molasse-type foreland basin in the foreland. These four principal events and
corresponding depositional sequences are recognized throughout the region and can be used as a framework for regional correlation
within the Alpine–Carpathian foreland basin.
Received: 18 August 1998 / Accepted: 9 June 1999 相似文献
15.
伦坡拉盆地西部丁青湖组新发现凝灰岩锆石U- Pb年龄及其地层学意义 总被引：1，自引：0，他引：1
伦坡拉盆地丁青湖组沉积时代的确定对于研究青藏高原中部的古高度和古气候具有重要的地质意义,但由于没有精确的年龄数据,其顶部是否跨入了新近系,一直以来都存在争论。作者在伦坡拉盆地西部鄂加卒地区开展野外调查过程中,在该剖面中部和上部新发现两套凝灰岩夹层,对凝灰岩进行了LA-ICP-MS锆石U-Pb定年,获得了两件凝灰岩样品的形成年龄分别为24.05±0.24Ma(MSWD=1.07,n=24)和22.64±0.33Ma(MSWD=0.45,n=17),时代分别为晚渐新世和早中新世。根据凝灰岩锆石U-Pb年龄和前人研究成果,将鄂加卒剖面的细碎屑岩地层重新厘定为丁青湖组,并将丁青湖组的沉积时代定为渐新世-中中新世。根据丁青湖组地层厚度及沉积速率估算,该组沉积持续时间在21～23Ma之间,其顶部地层的年龄在11～13Ma左右。由此可见,伦坡拉盆地接受连续沉积一直持续到了中中新世,这比过去普遍认识的晚始新世-渐新世时期青藏高原中部的古高度和古气候变化时间更晚。前人在该地区发现的近无角犀化石、攀鲈鱼化石、棕榈科叶片化石以及孢粉化石等研究结果共同证实,青藏高原中部渐新世晚期的古海拔高度低于～2500～3000 m。因此,该区晚渐新世-早中新世温暖潮湿的气候特征很可能是受到了印度洋气流穿透的影响,而且该影响可能一直持续到了中中新世,从而造就了该时期青藏高原生物的多样性。 相似文献
16.
《Journal of Asian Earth Sciences》2009,34(5-6):323-336
Geologic mapping and U–Pb detrital zircon geochronologic studies of (meta)sedimentary rocks in the Damxung area (∼90 km north of Lhasa) of the southern Lhasa terrane in Tibet provide new insights into the history of deformation and clastic sedimentation prior to late Cenozoic extension. Cretaceous nonmarine clastic rocks ∼10 km southeast of Damxung are exposed as structural windows in the footwall of a thrust fault (the Damxung thrust) that carries Paleozoic strata in the hanging wall. To the north of Damxung in the southern part of the northern Nyainqentanglha Range (NNQTL), metaclastic rocks of previously inferred Paleozoic age are shown to range in depositional age from Late Cretaceous to Eocene. The metaclastic rocks regionally dip southward and are interpreted to have been structurally buried in the footwall of the Damxung thrust prior to being tectonized during late Cenozoic transtension. Along the northern flank of the NNQTL, Lower Eocene syncontractional redbeds were deposited in a triangle zone structural setting. All detrital zircon samples of Cretaceous–Eocene strata in the Damxung area include Early Cretaceous grains that were likely sourced from the Gangdese arc to the south. We suggest that the that newly recognized Late Cretaceous to Early Eocene (meta)clastic deposits and thrust faults represent the frontal and youngest part of a northward directed and propagating Gangdese retroarc thrust belt and foreland basin system that led to significant crustal thickening and elevation gain in southern Tibet prior to India-Asian collision. 相似文献
17.
西宁和贵德盆地新生代沉积物重矿物变化对构造活动的响应 总被引：1，自引：0，他引：1
位于青藏高原东北缘的西宁、贵德盆地的新生代沉积序列较完整的记录了盆地周围物源区构造变形过程。重矿物是碎屑物质的重要组成部分,是最直观、有效揭示源区母岩、构造-沉积过程的重要手段。通过重矿物的系统分析,结合沉积-构造变形,揭示出始新世-上新世末西宁-贵得盆地及其源区经历了几个构造活动阶段:古新世-始新世早期的隆升阶段、始新世中期-渐新世晚期的构造稳定阶段、渐新世末-中新世初的构造隆升阶段、中中新世构造稳定阶段和晚中新世以来的强烈隆升阶段。并结合特征矿物（绿泥石）及古水流分析,推断古近纪西宁-贵德盆地是东昆仑山前一个统一盆地。中新世早期青藏高原的扩张导致了拉脊山开始隆起,使原型盆地解体;约8.5 Ma以来拉脊山强烈隆升,两侧盆地逐渐转变为山间盆地。这为正确理解青藏高原东北缘盆山格局的形成和演化提供了重要依据。 相似文献
18.
G. Neef 《Tectonophysics》1982,87(1-4)
Eight lithofacies representing a westward trending, deep sea fan, dominantly deposited from mass flow mechanisms, are recognised in geologic sections in the lower part of the Sarava Formation, of Late Oligocene/Early Miocene age, on Maewo Island, Vanuatu, New Hebrides. Also present representing the floor on which the deep sea fan prograded are non-calcareous, red siltstone and minor green siltstone which indicate deposition beyond the calcareous compensation depth, i.e. a depth greater than 4.25 km, and rare thin airfall ash.Previous workers proposed that rifting occurred in the area now occupied by Maewo during the Mid Miocene. However, the great depth at which the Late Oligocene/Early Miocene strata were deposited suggests that rifting occurred prior to the Late Oligocene. Rifting may have occurred even earlier because Pentecost Island, which lies south of Maewo, has a dismembered ophiolite suite which ranges in age from 35-28 Ma (Oligocene). The ophiolite suite may have formed in an interarc environment.The writer's reconstruction of the Oligocene arc system of the New Hebrides is an analogue of the present day Mariana Arc System. Interarc rifting ceased by the Early Miocene and during the Mid-Late Miocene the subduction of zone may have migrated westwards to lie along the Maewo-Pentecost axis. 相似文献