华北克拉通甘陶河群南寺组碎屑岩锆石U-Pb年龄、Hf同位素组成及构造意义

Zircons U-Pb Dating and Hf Isotopic Composition of Clastic Sedimentary Rock in the Nansi Formation,Gantaohe Group,North China Craton and Its Tectonic Significance

甘陶河群是华北克拉通前寒武纪典型地层之一,主要出露在河北省西北部.本文报道了甘陶河群南寺组碎屑岩地球化学、锆石U-Pb年龄和Hf同位素特征,主要认识如下：样品均属长石砂岩或石英砂屑岩,具有Nb、Ta、Zr、Hf亏损特征和负Sr异常;碎屑锆石U-Pb年龄主要分为三组：1800 ～ 2400Ma、2400～ 2600Ma和2600～3100Ma;甘陶河群南寺组最年轻的碎屑锆石年龄为1861Ma,结合甘陶河群上覆地层东焦群形成于约1.83Ga之后的地质事实,制约甘陶河群南寺组沉积上限范围1861 ～ 1830Ma.所有样品均具有约2.5Ga年龄峰值,记录了华北克拉通前寒武纪基底强烈构造岩浆热事件的时代,证明了华北克拉通前寒武纪基底主要由约2.5Ga岩石组成;中部带大陆地壳增生主要发生在约2.5Ga.

The Gantaohe Group is one of the typical Precambrian strata located in North China Craton, mainly exposed in the northwestern Hebei Province. The paper reports the whole-rock characteristics of geochemistry, zircon U-Pb ages and Hf isotopic composition on clastic sedimentary rocks in the Nansi Formation, the Gantaohe Group. All samples have obvious negative Sr anomalies and depleted Nb, Ta, Zr and Hr. U-Pb dates of detrital zircons yield three age populations of 1800 - 2400 Ma, 2400 - 2600 Ma and 2400 - 3100 Ma, respectively. The youngest detrital zircon age of the Nansi Formation of the Gantaohe Group is 1861 Ma. Combinning with the geological fact that overlying the Dongjiao Group formed after 1830 Ma, we can limit deposition timing of the Nansi Formation, the Gantaohe Group between 1861 Ma and 1830 Ma. All samples have about 2.5 Ga peak age, which is the intense tectonic magmatic thermal event recorded in the North China Craton＇ s Preeambrian basement and proved that the North China Craton Precambrian basement is mainly composed of about 2. 5 Ga rocks. The continental crust growth of the Trans-North China Orogen related to the tectono-magmatic event of the North China crust mainly occurred in about 2.5 Ga, which is strongly Craton during this period.