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Cenozoic Tectonic Control on the Abiogenic CO2 Gas Deposits, Huanghua Depression

DING Wei-wei1 2, DAI Jin-xin1 2 3, CHEN Han-lin2, YANG Chi-yin4   

  1. 1. University of Petroleum, Beijing 102200, China; 2. The Department of Earth Sciences, Zhejiang University, Hangzhou 310027, China; 3. Petroleum Exploration and Development Research Institute, CNPC, Beijing 100083, China; 4. Dagang Oil Field of CNPC, Tianjin 300280, China
  • Received:2004-12-20 Revised:2004-12-20 Online:2004-12-20 Published:2004-12-20

Abstract: Carbon dioxide is a nonhydrocarbon gas with high economic value and bright prospects in application.In the Huanghua Depression many high-content abiogenic C02 deposits were explored since 1960's. Through analysing the distribution characteristics of abiogenic C02 deposits and their relationshipwith Cenozoic tectonic activities, it is revealed that typical abiogenic C02 is distributed along the fault belt and fault intersection zones,and most of the deposits are distributed in the middle-northern Huanghua Depression.Areas with long term faulting,strong magmatism,and high geothermal gradients favor the generation and discharge of abiogenic gas. Deep faults,as pathways for mantle magma,may provide favorable pathways for the migration of mantle gas during extension.However,these NW-NWW trending faults,such as Haihe,Xuzhuangzi and Bogezhuang,are strike-slip faults in Cenozoic and the openness condition is bad.Only in the case when deep faults are intersected by NE or NEE trending extensional faults they could become favorable sites for discharge of abiogenic gases.For example,high-content abiogenic CO2 deposits were explored in the interseetions of the Xuzhuangzi and Gan faults.Further more,the intersections are also favorable locations for the ascent of deep heat flow.The heat of fault belts stems either from deep flow or dynamic metamorphism of carbonate rocks. Cenozoic magmatic activities not only released mantle origin CO2,but also provided heat source for metamorphism of carbonate rocks.Cenozoic magmatic rocks in this area were originated from the partialmelting of uppermantle.Faulting and regional spreading promoted the generation of magma and its intrusion into the crust.These magmatic rocks are distributed along NE-NEE trending faults.Magmatism ceased in the south of Huanghua Depression following the third stage of Shahejie Period,where only weak showings of abiogenic gas in the Cenozoic formation ale known.However,in the middle-northern Huanghua Depression basalts occurred from the Shahejie Period to the Neogene and favored the discharge of abiogenic gases. The Cenozoic migration of the faulting and magmatism in Huanghua depression has close relationship with the distribution characteristics of abiogenic CO2. Most of the aboigenic CO2 is distributed in the middle-northern part.The faulting and magmatism in the middle-northern part of Huanghua Depression weremost active between Shahejie and Dongying Period.The interval between the opening and closing of the faults is short,which is good for the reservation of CO2.