超大陆聚散的环境效应  

Environmental effects of assembly and breakup of supercontinents

作　　者：赵国春[1,2] 韩以贵 李建华 姚金龙[2] 刘潜 张东海 王潮 唐卿 张健 尹常青 张国伟 ZHAO Guochun;HAN Yigui;LI Jianhua;YAO Jinlong;LIU Qian;ZHANG Donghai;WANG Chao;TANG Qing;ZHANG Jian;YIN Changqing;ZHANG Guowei(Department of Earth Sciences,the University of Hong Kong,Hong Kong,China;State Key Laboratory of Continental Dynamics,Department of Geology,Northwest University,Xi'an,Shaanri 710029,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai,Guangdong 519080,China)

机构地区：[1]香港大学地球科学系,中国香港 [2]西北大学地质学系大陆动力学国家重点实验室,陕西西安710029 [3]中国地质科学院地质力学研究所,北京100081 [4]中山大学地球科学与工程学院,广东珠海519080

出　　处：《地质学报》2022年第9期3120-3127,共8页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41730213,41890831);香港RGC GRF项目(编号17307918);香港大学项目(编号102009906,102010100)联合资助的成果。

摘　　要：超大陆(Supercontinent)是在地球演化某一阶段所形成的几乎包含当时所有陆块的一个大陆。超大陆的聚合是通过全球性碰撞造山事件来完成的,而超大陆的裂解往往是超级地幔柱作用的结果。因此,超大陆的聚合与裂解事件势必对地球的水圈、大气圈和生物圈产生重要影响,进而影响地球的宜居环境。在超大陆聚合过程中,大陆深俯冲会导致大陆总体面积的减少和大洋面积的增加,从而导致全球海平面的下降;另一方面,在超大陆的聚合期间,地幔岩浆喷发至地表的机会明显减少,通过火山射气进入大气圈中的CO_(2)含量会急剧降低,从而形成极端寒冷干燥的冰室(Icehouse)气候,冰碛岩在低纬度地区广泛出现,不利于生物生存,或导致生物大量灭绝。相反,在超大陆裂解期间,大陆地壳会遭受拉伸减薄,大陆面积相对增加,大洋面积减少,海平面上升;另外,导致超大陆裂解的超级地幔柱所喷发的巨量玄武岩会导致洋壳加厚,也会导致海平面的上升;此外,超级地幔柱巨量玄武质岩浆的喷发会导致大气中CO_(2)浓度的增加,形成温暖潮湿性的气候(Greenhouse),有利于生命复苏或大爆发。然而,目前有关超大陆聚散的环境效应研究还处于初步阶段,而且主要局限于Pangea超大陆聚散对水圈、大气圈和生物圈的影响研究,一些研究结论的可靠性也有待于通过对Rodinia和Columbia/Nuna等更古老的超大陆聚散的研究结果加以证实。A supercontinent forms when all oceanic crust is consumed through plate subduction and nearly all continental blocks on Earth collide each other and coalesce into a single landmass. The assembly of a supercontinent was completed by global-scale continent-continent collision, whereas the breakup of a supercontinent was often caused by the rising of a super-mantle plume. Consequently, such global-scale events that led to the assembly and breakup of a supercontinentwill not only play important roles in the formation and evolution of Earth’s lithosphere, but will also have significant effects on its hydrosphere, atmosphere and biosphere, which will further affect Earth’s habitable environments. During the assembly of a supercontinent, the deep subduction of some continents beneath other continents would decrease the gross areas of continents and thus increase gross areas of oceans, which, as a consequence, causes the subsidence of global sea level. Meanwhile, mantle-derived magmas have less chances to erupt on the surface during the assembly of a supercontinent due to compressive environments, which would decrease CO_(2)degassed from volcanism and thus lower CO_(2)contents in the atmosphere, forming the cold-and-dry weather, so-called “Icehouse”, under which glacial tillites can develop in the low latitudinal areas. Such an extreme cold(icehouse) weather is hard for life to survive and may lead to mass-extinction. For example, some researchers regard the P/T boundary mass-extinction as a result of the extreme icehouse weather since it was coincident with the final assembly of Pangea. In contrast, during the breakup of a supercontinent, continental crust undergoes extension and thinning, which increases the gross areas of continents and thus decreases the gross areas of oceans, leading to the rising of global sea level. Moreover, the eruption of voluminous basalts from a super-mantle plume that causes the breakup of a supercontinent will increase COcontents in the atmosphere, forming the warm-and-wet weather,

关 键 词：超大陆 聚合 裂解 水圈 大气圈 生物圈 环境 地幔柱 

分 类 号：P542[天文地球—构造地质学]