帕米尔高原Rushan-Pshart古特提斯洋或中特提斯洋争论的岩石地球化学证据     

徐天德  王世锋  汤文坤  姚鑫 《地质科学》2020,(1):218-233

帕米尔高原上广泛分布的加里东期火山岩,印支期火山岩与燕山期火山岩被认为是块体依次向北俯冲拼贴到欧亚板块上的产物。特别是燕山期火山岩被认为是Rushan-Pshart中特提斯洋闭合的产物。但近年来地层古生物、火山岩证据不断表明Rushan-Pshart洋闭合时间在晚三叠一早侏罗世,由此限定Rushan-Pshart古特提斯洋性质,而帕米尔高原上广泛分布的燕山期火山岩是更南部的Shyok中特提斯洋闭合的产物。目前,中国境内Rushan-Pshart缝合带属性的研究工作展开较晚,研究程度较低。我们对塔什库尔干明铁盖沟一线燕山期火山岩带展开的工作发现零星分布的印支期花岗岩。印支期花岗岩错石U・Pb年龄显示岩体侵位时间在201 Ma左右。全岩主量元素特征表明岩石为I型高钾钙碱性闪长花岗岩;稀土元素在球粒陨石标准化图解中呈轻稀土元素相对富集,重稀土元素相对亏损的右倾海鸥型。明铁盖岩体的微量元素显示大离子亲石元素明显富集,而高场强元素明显亏损。稀土微量元素特征倾向花岗岩属性为岛弧型花岗岩,Sr-Nd-Hf同位素比值特征显示岩体形成于下地壳部分熔融环境。岩体的地化特征表明岩体形成的构造环境为板块汇聚的洋壳俯冲阶段,结合区域地质特征,我们将花岗岩体归为Rushan-Pshart古特提斯洋壳俯冲消减的产物。Rushan-Pshart缝合带传统上认为是中特提斯带,近年的研究进展认为其为古特提斯缝合带,本文的工作支持这种观点。Rushan-Pshart古特提斯缝合带的确立对帕米尔高原与青藏高原主体的块体对比提供了可信的对比方案,并对青藏高原新生代陆内变形方式的争论提供了可靠的证据。  相似文献   

Paleogene evolution and demise of the proto‐Paratethys Sea in Central Asia (Tarim and Tajik basins): Role of intensified tectonic activity at ca. 41 Ma     

Mustafa Y. Kaya  Guillaume Dupont‐Nivet  Jean‐Noël Proust  Pierrick Roperch  Laurie Bougeois  Niels Meijer  Joost Frieling  Chiara Fioroni  Sevin zkan Alt&#x;ner  Ezgi Vardar  Natasha Barbolini  Marius Stoica  Jovid Aminov  Mehmut Mamtimin  Guo Zhaojie 《Basin Research》2019,31(3):461-486

The proto‐Paratethys Sea covered a vast area extending from the Mediterranean Tethys to the Tarim Basin in western China during Cretaceous and early Paleogene. Climate modelling and proxy studies suggest that Asian aridification has been governed by westerly moisture modulated by fluctuations of the proto‐Paratethys Sea. Transgressive and regressive episodes of the proto‐Paratethys Sea have been previously recognized but their timing, extent and depositional environments remain poorly constrained. This hampers understanding of their driving mechanisms (tectonic and/or eustatic) and their contribution to Asian aridification. Here, we present a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy as well as a detailed palaeoenvironmental analysis for the Paleogene proto‐Paratethys Sea incursions in the Tajik and Tarim basins. This enables us to identify the major drivers of marine fluctuations and their potential consequences on Asian aridification. A major regional restriction event, marked by the exceptionally thick (≤ 400 m) shelf evaporites is assigned a Danian‐Selandian age (ca. 63–59 Ma) in the Aertashi Formation. This is followed by the largest recorded proto‐Paratethys Sea incursion with a transgression estimated as early Thanetian (ca. 59–57 Ma) and a regression within the Ypresian (ca. 53–52 Ma), both within the Qimugen Formation. The transgression of the next incursion in the Kalatar and Wulagen formations is now constrained as early Lutetian (ca. 47–46 Ma), whereas its regression in the Bashibulake Formation is constrained as late Lutetian (ca. 41 Ma) and is associated with a drastic increase in both tectonic subsidence and basin infilling. The age of the final and least pronounced sea incursion restricted to the westernmost margin of the Tarim Basin is assigned as Bartonian–Priabonian (ca. 39.7–36.7 Ma). We interpret the long‐term westward retreat of the proto‐Paratethys Sea starting at ca. 41 Ma to be associated with far‐field tectonic effects of the Indo‐Asia collision and Pamir/Tibetan plateau uplift. Short‐term eustatic sea level transgressions are superimposed on this long‐term regression and seem coeval with the transgression events in the other northern Peri‐Tethyan sedimentary provinces for the 1st and 2nd sea incursions. However, the 3rd sea incursion is interpreted as related to tectonism. The transgressive and regressive intervals of the proto‐Paratethys Sea correlate well with the reported humid and arid phases, respectively in the Qaidam and Xining basins, thus demonstrating the role of the proto‐Paratethys Sea as an important moisture source for the Asian interior and its regression as a contributor to Asian aridification.  相似文献   

Early Cretaceous deformation in the southern Tashkorgan region: Implications for the tectonic evolution of the northeastern Pamir     

《China Geology》2021,4(1):67-76

The Pamir Plateau comprises a series of crustal fragments that successively accreted to the Eurasian margin preceded the India-Asia collision, is an ideal place to study the Mesozoic tectonics. The authors investigate the southern Tashkorgan area, northeastern Pamir Plateau, where Mesozoic metamorphic and igneous rocks are exposed. New structural and biotite ⁴⁰Ar-³⁹Ar age data are presented. Two stages of intense deformation in the metamorphic rocks are identified, which are unconformably covered by the Early Cretaceous sediment. Two high-grade metamorphic rocks yielding 128.4 ± 0.8 Ma and 144.5 ± 0.9 Ma ⁴⁰Ar-³⁹Ar ages indicate that the samples experienced an Early Cretaceous cooling event. Combined with previous studies, it is proposed that the Early Cretaceous tectonic records in the southern Tashkorgan region are associated with Andean-style orogenesis. They are the results of the flat/low-angle subduction of the Neotethyan oceanic lithosphere.©2021 China Geology Editorial Office.  相似文献   

辽河盆地东部凸起区二叠系层速度-砂地比定量解释          下载免费PDF全文

严恒  代宗仰  王丽君 《江苏地质》2011,35(4):366-368

辽河盆地东部凸起勘探程度较低,钻井资料较缺乏,但地震资料相对较丰富。为了能在有限的资料中发掘更多能反映二叠系砂岩分布情况的信息,借助于地震处理中的速度分析资料,利用层速度-砂地比定量解释模型得到二叠系砂地比分布图,并在此基础上对二叠系的有利勘探区带进行了预测。  相似文献   

中亚天山—帕米尔地区成矿地质背景   总被引：1，自引：0，他引：1  

李宝强  孟广路  曹新  曹积飞  范堡程  王斌 《地质通报》2015,34(4):686-695

中亚天山—帕米尔地区地处亚欧大陆腹地,跨古亚洲、特提斯两大全球性构造域,是哈萨克斯坦—准噶尔、卡拉库姆—塔里木、中伊朗—冈底斯、印度四大古板块的结合部位,地质构造复杂,矿产资源丰富。自中新太古代(或古元古代)以来分为5大演化阶段:1太古宙—古元古代演化阶段,本区古陆可能是组成Pangea-Ⅳ泛大陆的一部分;2长城纪—青白口纪泛大陆裂解事件导致了西昆仑地区第一次大规模的成矿作用,新元古代超大陆汇聚形成阶段,中天山地区广泛沉积了一套文德系含炭质岩系,形成金的矿源层,为后期大规模金的成矿作用提供了物质基础;3新元古代超大陆裂解及古亚洲洋—原特提斯洋演化阶段,岩浆活动强烈深部壳幔物质交换频繁,尤其是晚泥盆世—早中二叠世碰撞后伸展期,是区内最重要的成矿期;4研究区工作程度低(部分地区为空白区),特提斯洋演化阶段矿床发现较少,但找矿潜力巨大;5欧亚大陆形成后的后造山阶段,伴随着造山带强烈的挤压、褶皱、抬升、走滑、推覆等构造活动,岩浆作用十分发育,形成了一系列与韧性剪切构造有关的金矿化,以及与中酸性岩浆热液活动有关的铁、铜、多金属、锂铍(铌钽)、钨、锡、钼等矿产。  相似文献   

帕米尔高原东北缘活动构造对塔什库尔干盆地地热控制作用   总被引：1，自引：0，他引：1       下载免费PDF全文

刘健  史杰  姚鑫  李钦  常志勇 《中国地质》2018,45(4):681-692

帕米尔东北缘位于青藏高原西北部,是新构造运动最强烈的地区之一。受控于公格尔拉张断裂作用的塔什库尔干盆地,活动构造强烈,高的大地热流值和丰富的地下水,使其具备地热资源形成的地质构造和水文条件。基于塔什库尔干盆地北部的曲曼地区地质构造、湖相地层年代学调查研究,该地区发育晚更新世的NNE向f_1和f_2正断层以及第四纪沉积物之下存在隐伏的近EW向的断层f_3。这3条断层是塔什库尔干断裂在不同构造演化时期形成的次级断层。结合EH-4电磁成像和钻孔及抽水试验等资料表明NNE向f_1和f_2正断层是地热系统的导水通道,而近EW向f_3断层为导热通道。该地区地热模式是大地热流为热源-地下水深循环逐渐加热-构造控水和控热。  相似文献   

A Preliminary Study on the Soft–Sediment Deformation Structures in the Late Quaternary Lacustrine Sediments at Tashkorgan, Northeastern Pamir, China     

LIANG Lianji  DAI Fuchu  JIANG Hanchao  ZHONG Ning 《《地质学报》英文版》2018,92(4):1574-1591

This study identified soft–sediment deformation structures(SSDS) of seismic origin from lacustrine sediments in the late Quaternary paleo–dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS 14 C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yr BP and 22710±80 yr BP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.  相似文献   

Structural analysis of the Lombard thrust sheet and adjacent areas in the Helena salient,southwest Montana,USA     

《Journal of Structural Geology》2014

The Helena salient is a prominent craton–convex curve in the Cordillera thrust belt of Montana, USA. The Lombard thrust sheet is the primary sheet in the salient. Structural analysis of fold trends, cleavage attitudes, and movement on minor faults is used to better understand both the geometry of the Lombard thrust and the kinematic development of the salient.Early W–E to WNW–ENE shortening directions in the Lombard sheet are indicated by fold trends in the center of the thrust sheet. The same narrow range of shortening directions is inferred from kinematic analysis of movement on minor faults and the orientations of unrotated cleavage planes along the southern lateral ramp boundary of the salient. As the salient developed, the amount and direction of shortening were locally modified as listric detachment faults rotated some tight folds to the NW, and as right-lateral simple shear, caused by lock-up and folding of the Jefferson Canyon fault above the lateral ramp, rotated other folds northeastward. Where the lateral ramp and frontal-oblique ramp intersect, folds were rotated back to the NW. Our interpretation of dominant W–E to WNW–ESE shortening in the Lombard sheet, later altered by local rotations, supports a model of salient formation by primary parallel transport modified by interactions with a lateral ramp.  相似文献   

Cenozoic paleo-environmental evolution of the Pamir–Tien Shan convergence zone     

《Journal of Asian Earth Sciences》2014

The retreat of the Tethys Sea and the uplift of the Tibetan Plateau play the critical roles in driving Asian climatic changes during the Cenozoic. In the Pamir–Tien Shan convergence zone, over 3000 m of Cenozoic successions, consisting of marine deposits in the lower, continental clay and fine sand in the middle, and molasse in the upper part, record the evolution of the Tethys Sea, the Asian aridification, and the deformation of the Pamir. In this work, the existing biostratigraphic subdivisions and new electronic spinning resonance dating results were used to assign ages to formations within the Ulugqat section. Sedimentary facies analysis and multi-proxy indices were used to reconstruct the paleo-environmental evolution. The results show: (1) the Pamir–Tien Shan convergence zone has undergone progressive environmental changes from shallow marine before ∼34 Ma to arid land at ∼23 Ma and finally to inter-mountain basin by ∼5.3 Ma; (2) the overall increase in mean size of grains, decrease in redness, in magnetic susceptibility, and in proportion of the ultrafine component of the sediments studied revealed a long-term strengthening in potential energy to transporting medium, cooling, and enhanced continental aridity, respectively; (3) the easternmost edge of the Tethys Sea prevailed in the western Tarim Basin from late Cretaceous to early Cenozoic, and finally retreated from this region around the Eocene–Oligocene transition, which in turn strengthened the Asian aridification; (4) accumulation of molasse with an upper age of ∼1 Ma suggests that the deformation front of the Pamir migrated to this area at or before that time.  相似文献   

Remarkable Species Diversity on Adjacent Salt Lakes in South Australia   总被引：1，自引：0，他引：1  

Peter HUDSON 《《地质学报》英文版》2014,88(Z1):73-73

正Lakes Acraman,Gairdner,Harris and Everard are a cluster of large episodic salt lakes on Eyre Peninsula,South Australia.These lakes have a characteristic terrestrial invertebrate fauna including various spiders,  相似文献