从中生代花岗岩的形成机制探讨水系的成因──珠江下游为例

珠江下游较大河道总是绕开中生代晚期花岗岩的现象无论用岩性、断裂或现代地形都难以解释,而运用花岗岩原地重熔说的观点却迎刃而解,这些河道实际上是遗传河,其形成于中生代晚期花岗岩背斜（或穹窿）之间的相对低洼地带,渐新世才开始贯通,形成外流型河流,此格局没有发生大的改变而保留至今．

RESEARCHES ON THE GENESIS OF DRAINAGE SYSTEM BASED ON THE FORMING MECHANISM OF MESOZOIC GRANITE --A Case Study of the Lower Pearl River System

enesis of drainage and forming mechanism of granite seem to be absolutely different problems, however, it is discovered that the larger rivers always avoid the late Mesozoic granite bodies, while most of the smaller ones often run through the bodies in the lower Pearl River System. It is very difficult to explain the phenomenon by the opinions of either lithologic differences, fault controls or modem topography, while "sinS the theory of remelting of granite formation, the problems Can be readily solved. According to the theory, with the rise of the ancient geothermal gradient in late Mesozoic Caused by the intense collision between Eurasian Plate and Pacific Plate, partial remelting in layer, thining as well as folding under the lateral strong compression occurred in the upper crust,as a result,the granitic magma should be Squeezed upward to the relative low pressure area in the top POrtion of anticlines, meaning that the large number of the granite theies in the same Period are only the doming portions of the same remelting layer. So the ancient rivers of that time in the lower Pearl River System certainly run in low areas avoiding the relative higher dome mountains (became granite bodies after stripped), and this regimen has been inherited until nowadayS though many of them had not been connected and had not beCome eXternal rivers (they just ran into the nearby basins) until Oligocene, which is real cause of the phenomenon. The relationship betWeen the large rivers and fate Mesozoic granite theies are not only found in the researched area, but abc in other areas that contain late Mesozoic (or early Tertiary) granite both in China and abroad, suggesting that the aSes of the rivers in those areas may be older than late Tertiary and that remelting mechanism has been the most important forming way of granite since Mesozoic.