【作者】 谢国刚；

【导师】 李德威； 黄水保；

【作者基本信息】 中国地质大学 ， 地质工程， 2004， 硕士

【摘要】 西藏冈底斯—拉萨陆块夹持于雅鲁藏布江结合带和班公湖—怒江结合带之间,向西与克什米尔拉达克弧地体相接,向东延至滇西腾冲陆块。该陆块内次级构造单元划分和大地构造属性认识存在较多争议。笔者根据其中部地区 1∶25 万邦多区、措麦区幅区调新发现阿索构造混杂岩带、文部和尼雄—许如错晚侏罗世—早白垩世岩浆弧及南北向地堑等成果,自北向南划分以下构造单元: (1)岷千日白垩纪残余海盆地:是在阿索小洋盆(边缘海盆地)消亡后形成的残余海盆地,以一套稳定含海相化石的碳酸盐沉积为标志。(2)阿索构造混杂岩带:呈北西西向展布于研究区中北部阿索一线,最宽约 14Km。构造混杂岩由被肢解的蛇绿岩块与复理石、深海硅质岩、泥质岩、火山岩、碳酸盐岩、浅海碎屑岩及二叠纪裂解块体等不同性质、不同时代的岩石混杂在一起组成。(3)它日错—文部燕山期岩浆弧:岩浆弧是在早期裂离型晚古生代地层块体基础上发展起来的成熟型岛弧,发育晚侏罗世—早白垩世钙碱性火山岩及同期花岗岩深成岩体。北部与牛堡组断陷盆地和它日错弧内断陷盆地为界,南部岩体与晚古生代地层呈侵入接触关系。其形成演化与班公湖-怒江洋及其弧后小洋盆向南俯冲消减作用密切相关,形成多期次火山作用和深成岩浆侵入作用叠加的岩浆弧。(4)措勤—邦多晚中生代复合弧后盆地:呈东西向展布研究区中部,北界以札拉断裂与它日错-当雄燕山期岩浆弧为界,南界为弧背断隆带北界即隆格尔-纳木错～仲沙断裂一线。盆地沉积由则弄群、捷嘎组、竞柱山组及林子宗群组成。(5)尼雄—格尔耿断隆带:位于研究区中部尼雄、格尔耿、措麦一带,呈北西西向延展,断隆带主体由石炭—二叠纪地层及晚侏罗世许如错超单元、早白垩世尼雄超单元等构成。在两者接触带上新发现了铁、铜多金属矿床。断隆带形成与南、北两条区域性边界大断裂带的多期活动密切相关。(6)冈底斯—查孜喜马拉雅期岩浆弧带:属冈底斯陆缘火山—岩浆弧的主体部分,它是晚白垩世—始新世雅鲁藏布江洋向北俯冲消减形成的陆缘火山—岩浆弧,主体由古新世—始新世林子宗群钙碱性系列火山岩及同期花岗岩组成。(7)当穹错—许如错新近纪—第四纪地堑:分布于研究区东侧当穹错,当惹雍错一带,区内宽 5~22km,南北向长 70km,由一组南北向正断层阶梯状断陷及其中间的湖泊盆地构成。地堑中间充填物为新近纪鱼鳞山组(Ny)、第四纪湖积、冲湖积物。 在上述合理划分研究区构造单元的基础上,对各构造单元的构造变形和边界断裂特点进行了系统归纳分析;并根据同位素年龄测试成果,结合前人资料,将冈底斯—拉萨陆块中部地区的地史演化划分六个阶段:(1)古特提斯阶段:本区处于冈瓦纳大陆北部的陆表海环境,以滨海-浅海陆棚相碎屑岩-碳酸盐沉积为主。(2)中特提斯洋扩张阶段( T—J1):早-中三叠世,冈底斯陆块之主体部分为隆起区,本区进入剥蚀阶段。三叠纪晚世,特提斯洋已拉开接受沉积。(3)班公湖—怒江洋向南俯冲阶段(J2-3):中侏罗世,特提斯洋(班—怒洋)洋壳向冈底斯—拉萨陆块俯冲,冈底斯陆块开始裂开并发展为岛弧构造带。(4)<WP=8>多岛弧—盆系洋陆转化阶段(J3—K1 ):在雅鲁藏布江洋向北和班公湖—怒江洋向南俯冲作 1用下,本区为多岛弧盆系构造环境,沉积建造类型复杂,火山岩浆活动频繁,构造变质变形强烈,是研究区地质发展史上的重要时期。早白垩世末的弧—陆碰撞造山运动后,基本上奠定了研究区大地构造格架的基础。(5)残余海盆沉积及陆—陆碰撞造山阶段(K1 —E2): 2陆块北部进入了陆内造山阶段,南部受雅鲁藏布江洋洋壳向冈底斯大陆边缘俯冲消减的影响,演化为陆缘火山岩浆弧。(6)陆内汇聚—高原隆升阶段(E3—Q):渐新世起,全区进入了陆内汇聚高原隆升阶段,形成推、滑覆构造,北东、北西向走滑断裂和南北向地堑。冈底斯—拉萨陆块中部构造单元和演化阶段的合理划分,可确定与锑、铅锌、银多金属有关的阿索—文部构造—岩浆成矿带和与铁、铜多金属矿有关的尼雄—格尔耿构造—岩浆成矿带的大地构造环境,也为研究晚中生代以来冈底斯—拉萨陆块中部及班公湖—怒江结合带的时空演化提供了基础性地质资料。更多还原

【Abstract】 The Gandise— Lasha landmass in Tibet, westward joining Keshimier arc massif andeastward extending to Tengchong landmass in West Yunnan, is located between theYarlungzangbojiang suture and the Ban-gong-Co-Nujiang suture. In geology circle, there aremany different opinions on the division of sub-units of tectonics in the landmass and itsgeotectonic attributes. On the bases of the new discoveries of the Asou tectonic mélange zoneand the late Jurassic Epoch--early Cretaceous Epoch magma arc in Wenbu and in Nixiong–Xurucuo and the N-S garben during the surveying of regional geology of the 1:250000 BangduoDistrict sheet and Cuomei District sheet in the middle of the landmass, the tectonic units intowhich can be divided from north to south in the middle of the landmass are as follows: ⑴ the Mianqianri Cretaceous relic sea basin: It is a relic sea basin formed after theconsumption of the small Asou ocean basin (margin sea basin) and characterized for a set ofstable carbonate sediments containing marine fossils. ⑵ the Asou tectonic mélange zone: Thezone, stretching in NNW strike along the Asou line in the middle-north study area, has thegreatest width of about 14km. The tectonic mélange consists of such rocks with differentproperties and various ages as ophiolite rock mass disconnected, flysch, deep sea siliceous rock,muddy rock, volcanic rock, carbonate rock, shallow sea clastic rock and split Permianmass .These rocks are mixed up with each other. ⑶ the Taricuo— Wenbu Yanshanian magmaarc: The magma arc, a mature type of island arc which was developed on the base of a early splitmass of late Palaeozoic strata, abounds with late Jurassic Epoch--early Cretaceous Epochcalc-alkaline volcanic rock and contemporary granitic plutons. Its northern border is the Niubaoformation faulted basin and the Taricuo faulted basin within arc,but its southern plutons had anintrusive contact with late Paleozoic strata. Its formation and evolution were in a close correlationwith the Ban-gong-Co-Nujiang ocean and its back arc small ocean basin subducting northward,forming the magma arc with superposition of poly-terms subvolcanism and plutonic magmatism.(4) the Cuoqin— Bangduo late Mesozoic compound back-arc basin: Stretching in E-W strike inthe middle study area, the basin has a northern border of the Zhala rupture and theTaricuo— Dangxiong Yanshanian magma arc and a southern border, namely theLonggeer— Namucuo-Chongsha rupture in the back arc faulted upwarping zone. The basinsediments consist of Luoshize group , Jiega formation ,Jingzhushan formation and LinzizongGroup.(5)the Nixiong— Geergeng faulted upwarping zone: Stretching in NWW strike alongNixiong— Geergeng--Cuomei in the middle study area, the faulted upwarping zone has a mainpart composed of Carboniferous Period— Permian Period strata and the Xurucuo ultra-unit of lateJurassic Epoch and the Nixiong ultra-unit of early Cretaceous Epoch, etc. Iron and copperPolymetallic deposits have been lately found in their contact. The formation of the faultedupwarping zone is closely relative to poly- activities of both of regional boundary great rupturezones, one in the south and the other in the north. (6)the Gandise –Chazi Himalayan magma arczone: As the main part of the Gandise marginal volcano— magma arc, the Gandise –Chazi<WP=10>Himalayan magma arc zone is a continental margin volcano— magma arc developed fromYarlungzangbojiang ocean subducting north during late Cretaceous Epoch--Eocene Epoch. Itsmain part is composed of the calc-alkaline series volcanic rock of Linzizong Group ofPalaeocene Epoch--Eocene Epoch and the contemporary granite. ⑺ theDanqiongcuo— Xurucuo Quaternary— Neogene graben: Distributed alongDanqiongcuo— Xurucuo in the eastern study area, the graben has a width of 5— 22kw and aS— N length of 70km and consists of a group of S— N ladder normal faulted subsides and lakebasins among them. The filling in更多还原