林周盆地晚白垩世—早始新世关键地质事件对青藏高原南部构造演化的制约
发布时间：2018-10-05 15:20
【摘要】：晚白垩世-早始新世拉萨地块南部的构造演化包括三个关键的地质事件,分别是:晚白垩世海相沉积向陆相沉积的转换过程;K-T界线附近陆相沉积层强烈的褶皱变形及不整合事件;早始新世强烈的岩浆喷发所夹持的火山活动休眠期事件。这些关键地质事件记录了印度大陆与亚洲大陆碰撞前后青藏高原南部构造演化的丰富信息,通过对它们进行系统而精确的年代学研究,可为复原高原演化模型,限制碰撞时代奠定基础。位于拉萨地块东南缘的林周盆地,由于晚白垩世-第三纪地层保存完整,层间界面清晰,拥有上述的三个关键事件良好的地质记录,分别表现为塔克那组海相沉积向设兴组陆相沉积的转换,设兴组强烈褶皱变形以及林子宗群火山岩不整合覆盖,典中组火山岩与帕那组火山岩之间的年波组沉积。为系统构建拉萨地块南缘关键地质事件的年代学格架,还原晚白垩世-第三纪拉萨地块南缘的构造演化过程提供了良好的条件。本文选取林周盆地林周县南、北、洛巴堆、甲荣、典中村北、强噶乡北共6条剖面对塔克那组、设兴组以及林子宗群火山岩进行详细的地层学及岩石学研究,并在剖面关键位置挑选35件样品进行系统的锆石U-Pb年代学研究。结果表明:研究区出露的塔克那组为浅海相沉积,其顶部砂岩的沉积时代,与设兴组底部火山岩夹层年龄共同将海陆转换的时代限定为95~83Ma。设兴组为河流相沉积,可分为上下两段,下段的曲流河沉积于~78Ma转变为上段的辫状河沉积;未卷入变形的闪长玢岩切割了强烈褶皱的设兴组,结晶年龄~72Ma,早于上覆火山岩的最老时代(~69Ma),进一步限定林周盆地上白垩统强烈变形的时代为78~72Ma。林子宗群火山岩是一套火山-沉积岩相的地层,自下而上可分为典中组、年波组和帕那组,其中帕那组又可以分为帕那组一段和帕那组二段两个岩性段。林周盆地林子宗群火山岩的年龄范围为66~47Ma,与拉萨地块西部的林子宗群范围相似,但滞后于中部。其中典中组:66~59Ma;年波组:56~54Ma;帕那组一段:54~50Ma;帕那组二段:49~47Ma。典中组与年波组之间存在一个~3Ma平行不整合,而年波组和上覆的帕那组之间为连续过渡。研究区上白垩统为一套弧后前陆盆地沉积,其间冈底斯弧持续隆升并提供主要物源。由于新特提斯洋俯冲角度的增加,~66Ma时冈底斯弧后地区的应力背景由挤压挠曲转为拉张伸展,林周盆地的性质也由早期的弧后前陆盆地(95~66Ma)转为火山弧及山间盆地(66~47Ma)。
[Abstract]:The tectonic evolution of the southern Lhasa block from late Cretaceous to early Eocene includes three key geological events. They are: late Cretaceous marine sedimentary to continental sedimentary conversion process / strong fold deformation and unconformity event near K-T boundary; early Eocene strong magmatic eruption held by volcanic activity dormant event. These key geological events record abundant information on tectonic evolution of the southern Qinghai-Xizang Plateau before and after the collision between the Indian continent and the Asian continent. Through systematic and accurate chronological studies of them, they can be used as a model for the restoration of the plateau evolution. Limiting the collision era laid the foundation. The Linzhou Basin, located in the southeast margin of Lhasa block, has a good geological record of the three key events mentioned above, due to the integrity of the late Cretaceous to Tertiary strata and the clear interlayer interface. They are characterized by the transformation of marine facies deposits from Takana formation to the continental facies deposits of the Shenxing formation, the strong fold deformation of the Xingxing formation, the unconformity overburden of volcanic rocks in the Linzizong group, and the deposition of the annual wave formation between the volcanic rocks of the Dianzhong formation and the Pana formation. It provides a good condition for systematically constructing the chronological framework of the key geological events in the southern margin of the Lhasa block and reducing the tectonic evolution process of the southern margin of the Lhasa block from late Cretaceous to Tertiary. In this paper, six sections are selected from the south, north, Lobabadi, Jia Rong, Danzhong Village and Qianggaxiang North of Linzhou Basin to carry out detailed stratigraphic and petrological studies on volcanic rocks of Tana formation, Xingxing formation and Linzongzong Group. 35 samples were selected at the key position of the section for systematic zircon U-Pb chronological study. The results show that the Tucker formation exposed in the study area is shallow marine sedimentary, and the sedimentary age of the top sandstone, together with the age of volcanic rock intercalation at the bottom of the Shexing formation, limits the age of sea-land transition to 95 ~ 83 Ma. The formation is a fluvial deposit, which can be divided into upper and lower sections. The meandering stream deposit in the lower member was transformed into braided river deposit of the upper member at 78 Ma, and the diorite porphyrite, which was not involved in the deformation, was cut into the strong fold formation. The crystallization age of 72Mais earlier than the oldest age of overlying volcanic rocks (69Ma), and the age of strong deformation of Upper Cretaceous in Linzhou Basin was 7872Ma. The volcanic rock of the Linzizong group is a set of volcanic sedimentary facies, which can be divided into three groups from the bottom to the top: the Dianzhong formation, the Nimbo formation and the Pana formation, in which the Pana formation can be divided into two lithologic sections: the first member of the Pana formation and the second member of the Pana formation. The age range of the volcanic rocks of the Linzizong Group in Linzhou Basin is 660.47 Ma, which is similar to the range of Linzong Group in the west of Lhasa block, but lags behind the middle part. Among them, the second segment of the Pana group, is composed of: 66 / 59 Ma.; the second stage of the Pana group is 1: 4947 MaA; the second stage of the Pana group is: 56, 56, 54 Ma. There is a parallel unconformity of 3 Ma between the canonical group and the Nian wave group, and a continuous transition between the Nimbo formation and the overlying Pana formation. The Upper Cretaceous in the study area is a set of back-arc Foreland basins, during which the Gangdis arc continues to uplift and provide the main provenance. Due to the increase of the subduction angle of the Neo-Tethys Ocean, the stress background of the Gangdis back-arc area changed from compressional flexure to extensional extension at 66Ma, and the nature of the Linzhou basin changed from the early back-arc Foreland basin (95~66Ma) to the volcanic arc and intermountain basin (66~47Ma).
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P542
，
本文编号：2253884
[Abstract]:The tectonic evolution of the southern Lhasa block from late Cretaceous to early Eocene includes three key geological events. They are: late Cretaceous marine sedimentary to continental sedimentary conversion process / strong fold deformation and unconformity event near K-T boundary; early Eocene strong magmatic eruption held by volcanic activity dormant event. These key geological events record abundant information on tectonic evolution of the southern Qinghai-Xizang Plateau before and after the collision between the Indian continent and the Asian continent. Through systematic and accurate chronological studies of them, they can be used as a model for the restoration of the plateau evolution. Limiting the collision era laid the foundation. The Linzhou Basin, located in the southeast margin of Lhasa block, has a good geological record of the three key events mentioned above, due to the integrity of the late Cretaceous to Tertiary strata and the clear interlayer interface. They are characterized by the transformation of marine facies deposits from Takana formation to the continental facies deposits of the Shenxing formation, the strong fold deformation of the Xingxing formation, the unconformity overburden of volcanic rocks in the Linzizong group, and the deposition of the annual wave formation between the volcanic rocks of the Dianzhong formation and the Pana formation. It provides a good condition for systematically constructing the chronological framework of the key geological events in the southern margin of the Lhasa block and reducing the tectonic evolution process of the southern margin of the Lhasa block from late Cretaceous to Tertiary. In this paper, six sections are selected from the south, north, Lobabadi, Jia Rong, Danzhong Village and Qianggaxiang North of Linzhou Basin to carry out detailed stratigraphic and petrological studies on volcanic rocks of Tana formation, Xingxing formation and Linzongzong Group. 35 samples were selected at the key position of the section for systematic zircon U-Pb chronological study. The results show that the Tucker formation exposed in the study area is shallow marine sedimentary, and the sedimentary age of the top sandstone, together with the age of volcanic rock intercalation at the bottom of the Shexing formation, limits the age of sea-land transition to 95 ~ 83 Ma. The formation is a fluvial deposit, which can be divided into upper and lower sections. The meandering stream deposit in the lower member was transformed into braided river deposit of the upper member at 78 Ma, and the diorite porphyrite, which was not involved in the deformation, was cut into the strong fold formation. The crystallization age of 72Mais earlier than the oldest age of overlying volcanic rocks (69Ma), and the age of strong deformation of Upper Cretaceous in Linzhou Basin was 7872Ma. The volcanic rock of the Linzizong group is a set of volcanic sedimentary facies, which can be divided into three groups from the bottom to the top: the Dianzhong formation, the Nimbo formation and the Pana formation, in which the Pana formation can be divided into two lithologic sections: the first member of the Pana formation and the second member of the Pana formation. The age range of the volcanic rocks of the Linzizong Group in Linzhou Basin is 660.47 Ma, which is similar to the range of Linzong Group in the west of Lhasa block, but lags behind the middle part. Among them, the second segment of the Pana group, is composed of: 66 / 59 Ma.; the second stage of the Pana group is 1: 4947 MaA; the second stage of the Pana group is: 56, 56, 54 Ma. There is a parallel unconformity of 3 Ma between the canonical group and the Nian wave group, and a continuous transition between the Nimbo formation and the overlying Pana formation. The Upper Cretaceous in the study area is a set of back-arc Foreland basins, during which the Gangdis arc continues to uplift and provide the main provenance. Due to the increase of the subduction angle of the Neo-Tethys Ocean, the stress background of the Gangdis back-arc area changed from compressional flexure to extensional extension at 66Ma, and the nature of the Linzhou basin changed from the early back-arc Foreland basin (95~66Ma) to the volcanic arc and intermountain basin (66~47Ma).
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P542
，
本文编号：2253884
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