扬子克拉通早太古代地壳物质的锆石同位素证据

Zircon Isotope Evidence for ≥3.5 Ga Continental Crust in the Yangtze Craton

是否存在早太古代地壳是比较不同陆块早期演化历史的重要基础。自3．8Ga的碎屑锆石在华北板块被发现后，关于扬子板块是否也存在早太古代的地壳物质成为众人争论的热点之一。长期以来，通常认为华北克拉通广泛出露太古代岩石，而扬子克拉通的基底主要形成于元古代，只在局部地区记录了少量太古代信息。然而，对崆岭混合岩的锆石U-Pb定年和Hf同位素分析结果，表明扬子克拉通曾经存在大于等于3500Ma的地壳物质。

The presence or absence of Early Archean crust in different continents provides an important basis for the comparison of their growth histories. Since the discovery of ca. 3.8 Ga detrital zircon in the North China craton by means of SHRIMP U-Pb dating, the question has cropped up whether the Yangtze craton, one of the two major blocks constituting the basement of China continent, also contains Early Archean crustal relicts. It is generally accepted that the basement of the Yangtze craton was mainly formed in Paleoproterozoic, with only minor Archean rocks aged 2.5-3.3 Ca. A combined study of zircon U-Pb dating and Hf isotope analyses of Kongling migmatite from this craton reveals the existence of ≥3.5 Ca rocks. This provides the first evidence for the existence of Early Archean （≥3.5 Ca） rocks in the Yangtze craton. Thus the early evolutionary history of the Yangtze craton may resemble that of the North China craton that has crustal relicts with the minimum age of 3.5 Ca. These Early Archean rocks had resided in the crust of the Yangtze craton for at least hundreds of million years before remelting, probably leaving some clues to be traced and verified.