Paleomagnetic study on orogenic belt:An example from Early Cretaceous volcanic rocks,Inner Mongolia,

• 作 者: Ren Shoumai ZHU Rixiang Huang
• 机 构: Institute of Geology and Geophysics,Strategic Research Center for Oil and Natural Gas
• 出 处: 中国科学D辑（英文版）
• 发表日期: 2004年期
• 关键词: orogenic belt paleomagnetism Suhongtu of Inner Mongolia Eurasia

We report paleomagnetic results for Early Cretaceous lava flows collected from the Suhongtu area of Inner Mongolia, the middle part of the Tianshan-Mongolia Fold Belt (TMFB).Rock-magnetic experiments for different lava flows indicate that the main magnetic mineral is pseudo-single-domain (PSD) magnetite. The characteristic high-temperature remanence component is isolated by thermal demagnetization temperature steps between 300℃ and 585℃,which yields a mean direction of D= 23.6°, /= 56.0° with α95 = 2.3°. We interpret this high-temperature remanence component as primary magnetization based mainly upon the petrographic analysis, which shows that the shape of magnetite crystal is relatively rounded square or polygon without internal reflection and deuterogenous phenomenon. The corresponding pole of the high-temperature remanence component is at 71.1°N, 200.5°E with A95 = 2.7°.This Early Cretaceous pole is in good agreement with those for Siberia, North China, and Inner Mongolia, suggesting that these continental blocks had already sutured together in the Early Cretaceous, which would further provide constraints on better understanding of the formation and evolution of the TMFB.