塔里木陆块新元古代冰期事件研究进展与展望  

Progress and prospect of Neoproterozoic glaciations related researches on the Tarim Craton

作　　者：钟焱 田辉[1,2,3] 张健[1,2,3] 张阔 李怀坤[1,2,3] 相振群[1,2,3] ZHONG Yan;TIAN Hui;ZHANG Jian;ZHANG Kuo;LI Huai-kun;XIANG Zhen-qun(Tianjin Center,China Geological Survey,Tianjin 300170,China;Precambrian Research Centre,China Geological Survey,Tianjin 300170,China;North China Center for Geoscience Innovation,China Geological Survey,Tianjin 300170,China)

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]中国地质调查局前寒武纪地质研究中心,天津300170 [3]中国地质调查局华北地质科技创新中心,天津300170

出　　处：《地质调查与研究》2020年第2期177-185,共9页Geological Survey and Research

基　　金：国家自然科学基金项目“塔里木陆块西南缘新元古代冰碛岩的年代学与地球化学研究(41902197)”;中国地质调查局项目“全国地质遗迹立典调查与评价(中国地质调查局天津地质调查中心)(DD20190075)”;“中国大地构造演化和国际亚洲大地构造图的编制(中国地质调查局天津地质调查中心)(DD20190359)”。

摘　　要：新元古代地球各圈层的耦合过程具有明显的阶段性特征,自老而新分别以广泛的岩浆作用、全球性的冰期事件和早期生命的迅速分化并繁盛为标志,地质年代表据此将这三个地史阶段分别命名为拉伸纪、成冰纪和埃迪卡拉纪。其中,成冰纪Sturtian冰期的启动时代和Marinoan冰期的消融时代,是标定新元古代3个“纪”级单元的直接依据。因而,成冰纪冰期事件的期次、规模、时代和成因问题,始终是地球科学领域近30年来的基础和热点课题。现有资料显示,成冰纪的两次剧烈冰室气候结束之后,地球迅速进入了极度温室环境,这种剧烈的摆动即“极端气候事件”。目前已有数种模型描述了大气CO2含量的变化对“新元古代极端气候事件”的控制作用;另外,对于杂砾岩、冰碛岩和块状冰碛岩各自蕴含的地质意义,也有学者开始重视并加以区分。地处我国西北地区的塔里木陆块,在东北缘的库鲁克塔格、西北缘的阿克苏-乌什-柯坪、西南缘的叶城一带,均出露了南华-震旦纪的杂砾岩记录。前期研究显示,塔里木陆块不同地区的新元古代冰川作用记录,存在岩性组合(如盖帽碳酸盐岩的发育与否)、沉积相、期次和时代等方面的巨大差异。与其他地区相比,出露于叶城一带的恰克马克力克群波龙组和雨塘组冰碛岩,目前缺少有效的年代学约束,也缺乏系统的块状冰碛岩化学成分研究。本文认为,以波龙组、雨塘组的块状冰碛岩为实例,开展全球同期块状冰碛岩的对比研究和综合分析,可以恢复相应时期地壳表层物质的基本组成特征,为理解新元古代极端气候事件的触发机制,提供直接证据。Coupling process among the Neoproterozoic lithosphere,biosphere,atmosphere and hydrosphere is characterized by three distinct stages which are typical of the extensively magmatic activities,global glaciations and proliferation of early marine lives.According to these representative symbols,the International Union of Geological Sciences approved the subdivision and nomenclature of the Neoproterozoic as the Tonian,Cryogenian and Ediacaran periods.It is worthy to note that the subdividing anchors of the three Neoproterozoic periods are directly linked with the two global glaciations during the Cryogenian Period,i.e.the initiation age of the Sturtian and deglaciation age of the Marinoan,respectively.In the last three decades,issues on the frequency,scale,timing and origin of the Cryogenian glaciations have always been a fundamental and debated topic in earth science.The available data of the Cryogenian glaciations indicate that the extremely severe icehouses had probably been followed by the extremely effective greenhouses,which is widely known as the Neoproterozoic Climatic Paradox(NCP).To date,a number of models invoke the fluctuations of atmospheric content of CO2 to depict its controls on the NCP.Recently,there are increasing cautions about discriminating the geologic significance of massive tillites from those of general diamictites and tillites.The Nanhuaan-Sinian diamictites outcropped in the Kuruktag,Aksu-Wushi-Keping and Yecheng areas within the Tarim Block,northwest China.The studies on these diamictites proposed that the Neoproterozoic glaciations had been differentially preserved with regard to the lithologic associations,facies,frequencies and ages.In contrast to the northeastern and northwestern parts of the Tarim Block,the effective geochronologic constraints on the tillites in the Bolong and Yutang formations of the Qiakemakelike Group in the Yecheng area are still ongoing.Moreover,the systematic geochemical researches on the massive tillites in these two formations are urgent to be carried out.This c

关 键 词：塔里木陆块 新元古代 雪球地球 杂砾岩 块状冰碛岩 

分 类 号：P534.3[天文地球—古生物学与地层学]