松潘—甘孜和西秦岭造山带地球物理特征及基底构造研究

A Study on Geophysical Characteristic and Basement in the Songpan—Garze and Western Qinling Orogenic Belt

本文对松潘—甘孜和西秦岭造山带地球物理特征以及基底构造进行了研究。研究表明:松潘—甘孜地块与西秦岭造山带的基底性质相似,均具有扬子块体的构造属性。褶皱基底的分布范围为:西南部以二道沟—玉树—理塘为界;东至青川—都江堰,即龙门山断裂带;北部边界由西到东,沿昆仑南缘至花石峡,然后转向北东,沿兴海—夏河—西和展布。在深地震测深和高温、高压岩石密度研究结果的约束下对重力资料进行反演,得到该地区的基底起伏。反演结果表明:松潘—甘孜—西秦岭地区的基底深度为1．3～8．6 km(以海平面起算)。阿坝—甘孜—道孚以及夏河—泽库—兰州一带为基底隆起区;若尔盖—唐克—红原、花石峡—达日和达日东南一带为基底凹陷区,其中红原附近基底深度达8．6 km,为全区基底深度最大的地方。

Geophysical characteristics and basement in the Songpan Garze block and the Western Qinling orogenic belts are studied in this paper. The results show that the basements in the Songpan--Garze and the Western Qinling area belong to Yangtze block. The boundaries are Erdaogou--Yushu--Litang on the southwestern; Qingchuan--Dujiangyan, i.e. the Longmen Mts. fault belt, on the east; and the line of southern Kunlun to Xinghai Xiahe--Xihe on the north. Based on the restrictions of deep seismic sounding and rock physical characteristics under the condition of high temperature and pressure, undulation of the basement in this area is calculated. The depths of the basement are between 1. 3 km to 8. 6 km in the Songpan Garze and the Western Qinling area. The basements are uplift in the areas around Aba Garze--Daofu and Xiahe--Zeku Lanzhou. And the basements are depressed in the areas around Rouergai Tangke--Hongyuan and Huashixia Dari and to the south of Dari. The depth in the Hongyuan area is 8.6 km, which is the deepest place in the Songpan--Garze and the Western Qinling area.