【摘要】 中国北方燕辽裂陷槽位于中朝板块北部,是巨厚中、新元古界的沉积区。中、新元古界包括长城系(1800～1600Ma)、蓟县系(1400～1000Ma)和青白口系(1000～800Ma)。上述划分是中国地质学家长期研究的共识,由全国地层委员会发布,中国地质调查局在全国地质调查填图中施行[1]。青白口系自下而上包括下马岭组、龙山组、景儿峪组,由于在下马岭组的斑脱岩中获得了锆石SHRIMPU-Pb年龄1368Ma±12Ma,从而对1000Ma作为青白口系底界的年龄乃至中国中、新元古界地质年表提出了挑战。中国地质学家必须面对新的下马岭组年龄值,拼弃传统思维,重新排定北方中、新元古界年代地层柱中各系、组的界线年龄。本文建议:长城系为1800～1600Ma;蓟县系为1600～1400Ma;新建西山系为1400～1200Ma;1200～1000Ma是一个待命名的系;新的青白口系为1000～800Ma,包括龙山组及景儿峪组。由于下马岭组中的斑脱岩反映了岛弧构造环境,从而可重塑中朝板块北部下马岭组及整个中元古界(指1800～1200Ma)为沟-弧-盆板块体系的弧后扩张盆地,即传统概念中的燕辽裂陷槽是弧后扩张的产物。沟-弧-盆板块体系可以系统地解释燕辽裂陷槽的动力学成因、各种地震灾变事件、火山活动、层控矿床等形成的地质背景。更多还原

【Abstract】 Located in the northern Sino-Korean plate,the Yanliao aulacogen is a region of very thick Meso-Neoproterozoic sediments.The Meso-Neoproterozoic consists of the Changchengian(1800-1600 Ma),Jixianian(1400-1200 Ma)and Qingbaikouan(1000-800 Ma)systems.The above-mentioned stratigraphic division is the consensus reached by Chinese geologists through their long-term study.In 2000,the National Commission on Stratigraphy of China issued a proposal document about it and the Chinese Geological Survey implemented it in geological survey and mapping in China.The Qingbaikouan System consists in ascending order of the Xiamaling,Longshan and Jing’eryu formations.Because a SHRIMP U-Pb zircon age of 1368±12 Ma was gained from bentonite in the Xiamaling Formation,the 1000 Ma age for the lower boundary of the Qingbaikouan System and even the Meso-and Neoproterozoic chronostratigraphic time scale in China are challenged.Chinese geologists must face the new age of the Xiamaling Formation,abandon the traditional idea of the division and redefine the boundary ages of various systems and formations in the Meso-and Neoproterozoic chronostratigraphic time scale of northern China.In the paper the authors propose the following new time scale:the age range of 1800-1600 Ma for the Changchengian System,1600-1400 Ma for the Jixianian System,1400-1200 Ma for the newly established Xishan System,1200-1000 Ma for a system to be named and 1000-800 Ma for the new Qingbaikouan System,including the Longshan and Jing’eryuformations.Because bentonite in the Xiamaling Formation reflects an arc tectonic environment,the Xiamaling Formation and the whole of the Mesoproterozoic Erathem in the northern Sino-Korean plate may be reconstructed as a backarc basin in the trench-arc-basin system,i.e.the traditional Yanliao aulacogen is the product of backarc spreading.The trench-arc-basin system can systematically explain the dynamic genesis of the Yanliao aulacogen,various earthquake events,volcanic activities and geological setting of stratabound ore deposits.The new dating data of the Xiamaling Formation reflects a depositional break of 300 or 200 Ma between the Xiamaling and Longshan formations.The break impels petroleum geologists to reconsider petroleum prospects in anoxic sediments(black shale and black siliceous rocks)in the Xiamaling Formation.更多还原