塔里木克拉通太古宙大陆起源:进展与问题

Origin of Archean Continental Crust in the Tarim Craton:Progresses and Issues

塔里木克拉通是中国三大古老陆块之一,但由于大面积沉积覆盖,其古老基底的形成演化研究程度较低。然而,近年来在塔里木盆地周缘的库鲁克塔格、敦煌、北阿尔金、铁克里克等地,以及塔里木盆地基底钻井岩心中,均发现了太古宙岩石,表明其可能普遍存在太古宙基底。笔者对塔里木克拉通太古宙岩石的研究历史和最新进展进行了简要总结,对太古宙大陆地壳的形成时间、机制和动力学背景进行了讨论,并指出了未来研究的方向。结果表明,塔里木克拉通的太古宙大陆地壳形成似乎具有区域差异性,北部的库鲁克塔格、敦煌和北阿尔金地区广泛发育新太古代岩浆作用,峰期为~2.5 Ga和~2.7 Ga,北阿尔金地区~3.7 Ga岩石的发现为塔里木克拉通始太古代陆核的存在提供了可靠证据,而西南部的铁克里克地区和盆地基底以中太古代(3.2~2.8 Ga)地壳生长和再造为特征,目前尚未发现新太古代岩石。地球化学、热力学模拟和锆石氧逸度–湿度计研究表明,太古宙大陆地壳可能是不同源岩在不同深度(压力)通过水致熔融产生的,形成于俯冲相关构造背景,而早期板块构造自始太古代以来就已运行。太古宙大陆地壳物质组成的确定、变质–变形的识别、岩浆形成物理化学条件的厘定等方向仍是未来塔里木克拉通太古宙地质研究的重点。

The Tarim Craton is one of the three ancient continental blocks in China,but the formation and evolution of its ancient basement have been poorly studied due to extensive sedimentary cover.However,in recent years,Archean rocks have been found in the Kuruktag,Dunhuang,North Altyn Tagh,Tiekelike areas on the periphery of the Tarim Basin,as well as in the drill core from its basement,indicating that there may be a widespread Archean basement.In this paper,the study history and recent progress of Archean rocks in the Tarim Craton are summarized,the formation time,mechanism and geodynamics of Archean continental crust are discussed,and the future research direction is pointed out.The results show that the formation of the Archean continental crust in the Tarim Craton appears to have regional differences.Neoarchean magmatism was widely developed in the Kuruktag,Dunhuang and North Altyn areas,with peaks of~2.5 Ga and~2.7 Ga.The discovery of~3.7 Ga rocks in the North Altyn Tagh area provides reliable evidence for the existence of an Eoarchean continental nucleus in the Tarim Craton.The Tiekelike area and basin basement in the southwest Tarim are characterized by Mesoarchean(3.2~2.8 Ga)crustal growth and reworking,and no Neoarchean rocks have been found.Geochemistry,thermodynamic modelling and zircon oxybarometer-hygrometer indicate that the Archean continental crust might have been produced by water-induced melting of different source rocks at different depths(pressures)and formed in subduction-related tectonic settings,indicating that early plate tectonics have been in operation since the Eoarchean.The elucidation of the components of the Archean continental crust,the identification of metamorphism and deformation,and the determination of the physical and chemical conditions of magma formation are still the focus of future studies of the Archean geology in the Tarim Craton.