the Earth’s crustal structure in the Đà River
hydroelectric ladder region by using gravity and magnetic analysis results
Phan Thanh Quang, Cao Đ́nh Trọng, Phạm Nam Hưng, Bùi Văn Nam
This paper presents about the earth’s crustal structure of the Đà River ladder of hydroelectric plants on the basis of Bouguer gravity and magnetic analysis. The results have shown that: The fault of the 1st order have a crust penetration depth and structure zoning including: Lai Châu - Điện Biên, Phong Thổ, Sem La, Mường La - Bắc Yên. The fault system was developed in the northwest - southeast, sub latitude, and northeast - southwest directions. The depth of the crystallize basement varies quite complicatedly from outcrop on the surface to 5.5 km deep. The difference between the density of the above sediment (2.62- 2.66 g/cm3) and the below granite layer (2.70-2.76 g/cm3) was approximately 0.08 g/cm3; Conrad surface- depth changed from 7.98 km to 18.49 km.
The difference between the density of the above granite layer (2.70-2.76 g/cm3) and the below basalt layer (2.90-2.94 g/cm3) was approximately 0.19 g/cm3; Moho surface- depths change from 21.3 km to 35.4 km, they tend to be raised in the southeast and sank slowly in the west. The disparity between the basalt layer density (2.90-2.94 g/cm3) and the upper mantle layer was approximately 0.4 g/cm3.
Người biên tập: GS. TS Bùi Công Quế.