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松潘-甘孜地块位于青藏高原东北部、由近东西向构造向近南北向构造转折的部位,若尔盖盆地位于该地块核心.利用近期在该区域完成的深地震测深结果,建立了若尔盖盆地及周缘褶皱造山带地壳结构模型,对若尔盖盆地基底结构、性质,若尔盖高原盆地与周缘褶皱造山带构造关系,青藏高原东北缘地壳形变增厚、壳内解耦松弛进行了研究.结果表明:若尔盖盆地近地表三叠纪岩层为高致密(2.65~2.75g·cm?3)和高速度(约5.6km·s?1)介质岩性,形成了特殊的“中生代基底”构造;松潘-甘孜地块在青藏高原隆升、物质东流以及周缘稳定地块的阻挡过程中被改造为相对稳定的若尔盖高原盆地和盆地周缘更为活动的褶皱造山两类不同地壳结构性质的构造单元;青藏高原东北部的地壳增厚、壳内解耦主要发生中下地壳,这种壳内以低速为主、多反射界面结构特征在若尔盖盆地周缘褶皱带造山带更为明显,突出了褶皱造山构造区域中下地壳内部经历了更为强烈的构造形变;若尔盖盆地及南北两侧褶皱造山带地壳厚度约50km,未发现“山根”构造,推测在褶皱造山后期,青藏高原地壳东流物质在周边刚性地块阻挡下围绕东构造结、沿着相对松弛的南侧方向顺时针转向流出,其结果使若尔盖盆地周缘褶皱造山带经历了强烈的伸展构造作用.
The Songpan-Garzê block is located in the northeastern Qinghai-Tibet Plateau and consists of a structural transition from near east-west to nearly north-south direction, and the Ruoergai Basin is located at the core of the block. Using the recent deep seismic sounding results completed in this area, And the crustal structure model of the peripheral fold orogenic belt.Studies on the basement structure and properties of the Zoige basin, the structural relationship between the Zoige Plateau and the peripheral fold orogenic belt, the crustal thickening in the northeastern margin of the Qinghai-Xizang Plateau, and the decoupling and relaxation in the crust are carried out.The results show that: The Triassic strata near the surface of the basin are characterized by high densities (2.65 ~ 2.75 g · cm -3) and high velocity (~ 5.6 km · s -1) lithologies, forming a special Mesozoic basement structure. Songpan- During the uplift of Qinghai-Tibet Plateau, eastward flow of material and blockage of the peripheral stable block, the Garze block has been transformed into relatively stable structural units of the two types of fold crustal orogen that are more active in the Zoigê Plateau Basin and the basin margin. Qinghai-Tibet Plateau In the northeastern plateau, the crust is thickened, and the decoupling in the crust mainly occurs in the middle and lower crust. This crust is dominated by low velocities. The multi-reflecting interface is characterized by the pleat With orogenic belt more obvious, highlighting the fold orogeny structure of the middle and lower crust experienced a more intense structural deformation; the Ruoergai basin and the crust orogeny on both sides of the crust and the thickness of about 50km, did not find the “mountain root” structure, speculated In the late folding orogeny, the crustal eastward mass of the Qinghai-Tibet Plateau circled the eastern tectonic knot under the block of peripheral rigid blocks and turned clockwise outward along the relatively slanting south side. As a result, the peripheral fold belt in the Zoigê Basin experienced a strong extension Constructive effect.