Druse calcite crystals formed by Mesoproterozoic paleo-earthquake activity in the northern margin of the North China Craton

作     者：Yueshuang Du Zhiguang Zhou Guosheng Wang Chen Wu Wenchao Xu 

作者机构：School of Earth Sciences and Resources， China University of Geosciences (Beijing) Key Laboratory of Continental Collision and Plateau Uplift， Institute of Tibetan Plateau Research， and Center for Excellence in Tibetan Plateau Earth Sciences， Chinese Academy of Sciences No.1 Institute of Geological and Mineral Resources Survey， Henan Bureau of Geo-exploration & Mineral Development 

出 版 物：《Journal of Earth Science》 (地球科学学刊(英文版))

年 卷 期：2021年

核心收录：

学科分类：070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学] 

基　　金：supported by the National Natural Science Foundation of China (grants 41772227 and 41872232) supported by the Inner Mongolia Mapping Programs (project numbers 1212010811001, 1212011120700, DD20160045, and 1212010510506) 

摘      要：The Meso–Neoproterozoic Bayan Obo Rift is located along the northern margin of the North China Craton， and was associated with the break-up of the Columbia supercontinent. During rift evolution， syn-sedimentary deformation occurred due to tectonic activity and earthquakes. Seismic events are recorded in the Jianshan Formation of the Bayan Obo Group， Inner Mongolia， as soft sediment deformation structures in the central Bayan Obo Rift. Druse calcite crystals and collapse breccias in the Jianshan Formation may provide information on the rift evolution. The druse calcite crystals are idiomorphic–columnar in shape and associated with graphite， pyrite， and quartz. δ13C values of the graphite are –20‰， indicative of biogenic deoxygenation and formation in water. The druse calcite crystals are inorganic in origin and formed in water at a temperature of 55?C， based on calcite δ13C and δ18O data. The calcite grew in paleo-caves containing fault breccias， with heat derived from faulting. As such， the druse calcite crystals are important evidence for seismic events. The collapse breccias （i.e.， fault breccias） and other indicators of slip show that displacement occurred from NE to SW， which is different from the paleocurrent direction in the Jianshan Formation. The thickness of the collapse breccia is ～200 m， which represents the height of the fault scarp. The strike of the fault scarp was NE–SW， based on the distribution of the collapse breccia. The Bayan Obo and Yanliao rifts experienced rapid NW–SE extension， and developed similar deformation structures at ca. 1.6 Ga related to break-up of the Columbia supercontinent.