太古宙氧气绿洲:地球早期古地理重塑的重要线索

太古宙(4.03—2.42 Ga)是地壳形成与生物圈确立的主要阶段,以具有高度还原的大气圈为特征。但多年研究的结果表明,即使在缺氧的大气圈之下,分子氧也可能局部聚集在浅水环境中并形成"太古宙氧气绿洲(Archean oxygen oases)"。因此,对太古宙氧气绿洲的识别和研究,就成为深入理解大气圈氧气含量上升和生氧光合作用起源的重要线索,也成为近年来前寒武纪沉积学研究中的热点问题之一。尤其值得注意的是,对2.8 Ga太古宙海相灰岩、3.46 Ga的氧化海洋中形成的原生赤铁矿及3.43 Ga叠层石生物礁的探索与解释,已成为识别和研究太古宙氧气绿洲的成功实例。追踪这些开创性的研究,不仅有益于对前寒武纪地球表层环境复杂演变的深入了解和对早期地球的古地理重塑,而且对拓宽沉积学和古地理学的研究范畴具有重要意义。

Archean oxygen oases: An important clue of palaeogeographical reconstruction in the early Earth

Archean Eon (from 4.03 to 2.42Ga) is a major period of crust formation and biosphere establishment，characterized by a highly reducing atmosphere. Substantial amounts of molecular oxygen might have accumulated locally in protected shallow-water environments that favored cyanobacterial productivity and were sufficiently isolated;and this type of protected shallow-water environments results in an “Archean oxygen oases”even though under an anoxic atmosphere. Thus，identification and research of an Archean oxygen oasis become an important clue for the further understanding of the rise of atmospheric oxygen concentration and the origin of oxygenic photosynthesis，which is a hot point of the Precambrian sedimentology. Interestingly and fascinatingly，studies and interpretations on the Archean marine limestones (ca. 2.8Ga), the primary haematite formed in an oxygenated sea (ca. 3.46Ga) and the stromatolite reef (ca. 3.46Ga), become some typically successful examples for the research of the Archean oxygen oases. Tracing these fruitful and starting researches will be propitious to further understanding both the sophisticated evolutionary process of surface environment and its palaeogeographical reconstruction in the early Earth，and are meaningful to broaden the studying domain of sedimentology and palaeogeography.