摘要
中祁连拉脊山、化隆地区的变质核杂岩是由韧性变形的太古宙、元古宙化隆群变质岩系组成核 ;由脆 -韧性变形和经受了低压变质的中、上寒武统和岩体组成中间层 ;由脆性变形和未变质的下白垩统组成盖层 .变质核杂岩的组成与结构显示了对称伸展和隆升的特征 .2 3～ 32Ma是快速隆升的时期 .主剥离断层剪切位移量约 2 5～ 2 7km ,并根据矿物对计算 ,变质核杂岩的伸展变质温度约 6 2 5～ 6 30℃ ,变质深度约 2 0km ,变质压力约为 0 .6 3GPa ,属偏低压型区域热流变质作用 .从青藏高原热壳、热幔、厚壳的演化历史及构造隆升活动来看 ,认为拉脊山、化隆变质核杂岩是地幔热隆引起地壳伸展的典型实例 ,是研究青藏高原岩石圈结构和高原隆升的重要窗口 .
This paper studies the metamorphic core complex in Lajishan-Hualong area, middle Qilian. Its core consists of Archeozoic and Proterozoic Hualong Group metamorphic complexes undergoing ductile deformation, with its median layers, Middle-Upper Cambrian and mass of magmatic rocks undergoing plastic deformation of low-pressure metamorphism, and overlayers, Lower Cretaceous experiencing minor brittle deformation without metamorphism. The composition and texture of the metamorphic core complex show features of symmetrical extension and uplifting and a rapid uplifting period within 23 to 32 Ma and displacement quantity of normal denudational faults about 25-27 kilometres. The mineral pair calculation measures its extensional metamorphic temperature about 625-630 ℃, the metamorphic depth about 20 km and the metamorphic pressure about 0.63 GPa, which shows that it should belong to a regional thermal current metamorphism of low-pressure type. In the light of long run thermal crustal, thermal mantle, thick crustal evolution and tectonics upwelling of the Qinghai-Tibet plateau, the Lajishan-Hualong metamorphic core complex can be considered as a typical example of crust extension caused by thermal upwelling of mantle. The Lajishan-Hualong area can, therefore, become a window to look into the structure and tectonic upwelling of the Qinghai-Tibet plateau lithosphere.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2003年第4期407-413,共7页
Earth Science-Journal of China University of Geosciences
基金
中国地质调查局"民和县幅 1:2 5万数字地质填图项目"(No .2 0 0 2 13 0 0 0 0 16) .
关键词
变质核杂岩
热隆
伸展构造
拉脊山
metamorphic core complex
thermal upwelling
extensional tectonic
Lajishan.
