河北大庙斜长岩杂岩体锆石U-Pb年龄及其地质意义

Single zircon U-Pb ages and their geological significance of the Damiao anorthosite complex, Hebei Province, China

河北承德大庙斜长岩杂岩体是我国唯一的岩体型斜长岩。为了确定杂岩体的形成时代,作者从杂岩体主要组成岩石——苏长岩、纹长二长岩中选取锆石作U-Pb年龄测定,所获得的结晶年龄分别是1693±7 Ma、1715±6 Ma。这些锆石U-Pb年龄数据说明,大庙斜长岩杂岩体的侵位至少持续了约20 Ma。大庙斜长岩杂岩体和密云奥长环斑花岗岩、长城系大红峪组钾质火山岩,以及广泛发育的基性岩墙群一起可能代表华北陆块1750～1650 Ma大陆裂解事件的岩浆作用产物。

The anorthosite complex in the Damian area, Hebei Province, is the only one massif-type anorthosite intrusion in China. To date crystallization age of this complex, zircons were separated from norite and mangerite, two major rock types of the complex. Ages obtained using the single zircon U-Pb method on the norite and mangerite are 1693 +/- 7 Ma and 1715 +/- 6 Ma, respectively. These age data suggest that the emplacement of the Damiao anorthosite complex lasted at least 20 Ma. The Damiao anorthosite complex, associated with the Miyun rapakivi, potassic volcanic rocks of the Dahongyu formation in the Changcheng Group and wide-spreading mafic dykes, is interpreted as representing magmatic products related to the break-up event of the North China craton during about 1750 Ma to 1650 Ma.