志留—泥盆纪华北高地的猜想:从甘肃的研究说起  

GUESS ON THE SILURIAN-DEVONIAN NORTH CHINA HIGHLAND:EVIDENCE FROM THE INFORMATION OF GANSU

作　　者：张旗[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029

出　　处：《甘肃地质》2011年第2期1-10,共10页Gansu Geology

基　　金：中国科学院地质与地球物理研究所岩石圈演化国家重点实验室项目;国家自然科学基金重大研究计划(91014001;90714007和90714011)项目资助的研究

摘　　要：为华北克拉通缺失晚奥陶世—早石炭世地层的记录,岩相古地理解释为一个古陆,我们研究认为它可能是一个高地。寒武—奥陶纪时华北克拉通为广泛的浅海相碳酸盐岩沉积,指示为海台地势,地壳厚度<30km。志留—泥盆纪时为一高地,地壳厚约>40km。晚石炭世发育海相、海陆交互相沉积,地壳厚度也在30km左右。高地的形成与构造挤压有关,根据区域地质资料和有限的花岗岩资料推测,在志留纪时,水平的挤压力可能来自西部,西部有埃达克型和喜马拉雅型花岗岩出露,指示南祁连与华北发生了碰撞。晚期泥盆纪时的挤压力源于北方,北方有零星埃达克岩出露,推测与古亚洲洋地体之间的弧陆碰撞有关。志留—泥盆纪的华北高地属于冷高地,没有伴随花岗岩的大量活动,因此,高地的垮塌与拆沉无关,可能与晚石炭世时的地壳伸展减薄有关,地壳厚度减薄了大约10km。志留—泥盆纪的华北高地比中国东部高原面积还大,也许是中国地质历史上最大的一个高地,研究这个冷高地形成和破坏的机制及其对全球构造、气候、环境的影响等具有重要的意义。North China Craton（NCC） missing the Late Ordovician-Early Carboniferous strata,was interpreted as an ancient landmass by the Petrographic palaeogeographical work,but our study suggests that it may be a highland.The NCC has a wide range of shallow marine carbonate sediments in Cambrian-Ordovician,indicating a sea-platform topography with crustal thickness less than 30 km.During the Silurian-Devonian,it was a highland with crust thickness 〉40 km.In the Late Carboniferous,the NCC has widely distributed marine and paralic deposition indicating of crustal thickness with 30 km.The formation of the highland may be related to tectonic compression from the west in the Silurian and north in Devonian,respectively,based on regional geological data and limited geochemical data of granite.Minor Silurian Himalayan-and Adakite-type granites in western NCC may relate to the collision between the South Qilian block and the NCC,hence the horizontal compression pressure may came from the west during that time.Similarly,minor Devonian adakites cropping out at the northern part of the NCC may related to the arc-continental collision during the accretionary orogenesis of the Central Asian Orogenic belt.The Silurian-Devonian North China Highland should be a cold-highland,because no large number of granite activities in that time.The collapse of the highland has no relation with the delamination,but related to crustal thinning in the Late Carboniferous,ca.10 km of the crust having lost.The area of the Silurian-Devonian North China Highland is bigger than that of the Late Jurassic-Early Cretaceous East China Plateau.The Silurian-Devonian North China Highland may be the largest highland in geological history of China.The mechanism of formation and destruction of the cold highland has significance for global tectonics,climate,and environment issues.

关 键 词：华北克拉通 志留—泥盆纪的华北高地 冷高原 热高原 高地形成机制 

分 类 号：P56[天文地球—构造地质学]