Paleomagnetism of Late Mesozoic granitic intrusions in Hong Kong: implications for Upper Cretaceous reference pole of South China

Abstract

Two Late Jurassic-early Cretaceous granite plutons in Hong Kong were sampled at 16 sites for paleomagnetic determination. The two granites show differences in magnetic properties and mineralogy but similar natural remanent magnetization (NRM) directions. Multiple magnetizations and dual polarity have been detected in the samples. Isothermal remanent magnetism, magnetic susceptibility, and coercivity measurements reveal multidomain titanomagnetite as the principal magnetic carrier. The pole position from 12 sample sites is 171.9°E, 78.2°N, A95=10.6°. The dual polarity and cooling ages of the granites suggest a Late Cretaceous acquisition of the remanent magnetism. Based on four different studies, the Upper Cretaceous reference pole of South China is located at 194.3° longitude, 73.5°N latitude, A95=10.4°. Paleomagnetic results from North China, South China, and Eurasia show no large-scale Cenozoic relative movements among the three blocks, but the small separation between the paleomagnetic poles of South China and Eurasia probably implies a minor relative movement since the Late Cretaceous. -from Author