首页|Druse Calcite Crystals Formed by Mesoproterozoic Paleo-Earthquake Activity in the Northern Margin of the North China Craton
Druse Calcite Crystals Formed by Mesoproterozoic Paleo-Earthquake Activity in the Northern Margin of the North China Craton
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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 sedi-ment 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 crys-tals are inorganic in origin and formed in water at a temperature of 55℃,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 brec-cia 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.
North China Cratondruse calcite crystalspaleo-earthquake activitycollapse brecciaBayan Obo riftProterozoic
School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China
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,Beijing 100101,China
No.1 Institute of Geological and Mineral Resources Survey,Henan Bureau of Geo-Exploration&Mineral Development,Luoyang 471000,China
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