羌塘地区壳内低阻层特征及初步认识

Characteristics and Preliminary Knowledge of Inner-Crustal Low Resistivity Zone in Qiangtang Area.

在羌塘地区深达100km的大地电磁测深(MT)大剖面上,壳内低电阻层显示出不同面貌。南段以“Δ”块状体为特征;北段低阻层从-100km深处上升至近地表-10km处,呈巨大的蘑茹体。在平面等值线图上,北羌塘地区以大面积坳隆、东西分块为特征;南羌塘地区以条带状坳隆南北分带为主。研究结果认为,低电阻层与地形相关,这不仅旁证了有关低阻层解释的可靠性,同时说明北羌塘独特的块状高山区地貌是活跃的深部构造运动的表现。研究区地壳既非全是冷壳、也非全是热壳,应是冷壳、热壳呈楔块状相间,尤其是确旦错一带可能存在热柱。这对油气富集、形成、二次成因将有较大的影响。

The inner-crustal low resistivity zones over the profile of crustal magneto-electrotelluric survey beneath100km in Qiangtang area show district images which are characterized by massive body symbolided as'△'in southern segment and tremendous mushroom body in northern segment ranging from-100km up to-10km in depth.From the view of plane contour diagram,the northern Qiangtang area is characterized by large area of depression-uplift and bulk-ing in its east and west parts,while the southern Qiangtang area by strip depression-uplift and zoning in its south and north parts.The results show that the low resistivity zone is related closely to the landscapes,not only indicating relia-bility about the zone interpretation,but that the distinctive features like block high mountain range are expressions of active deep tectonic movements.The crustal bodies in studied area are neither cold nor thermal,but cold crust alter-nates with thermal crust in form of wedge,along the Quedancuo area may exist thermal plume,all of which has greater effect on its petroleum accumulation,generation and secondary origin.