南秦岭龙草坪结晶杂岩锆石U-Pb同位素地质年代学研究

ZIRCON U-Pb ISOTOPIC GEOCHRONOLOGY OF THE LONGCAOPING CRYSTAL COMPLEX IN SOUTHERN QINLING

佛坪地区龙草坪结晶杂岩是南秦岭重要的基底岩块 ,用空气磨蚀法对锆石颗粒处理后 ,再应用单颗粒锆石U Pb法对结晶杂岩年龄进行系统测定 ;取得一系列年龄值 ,结合地质特征综合分析认为 2 50 3± 4 0Ma～ 2 50 6± 2 4Ma年龄代表了其成岩年龄。早元古代克拉通化、加里东期俯冲及裂谷作用、海西期隆滑构造以及印支期碰撞造山作用在结晶片麻岩中都有同位素记录。

The Longcaoping crystal complex in the Fuping area is one of the most important basement complexes in the Qinling orogenic belt. U Pb methods using single grains of zircon were employed in geochronological study of the Longcaoping gneiss after the same samples were handled by the air abrasion techniques. By taking the geological background of the region into consideration, the crystallization age of the Longcaoping gneiss would be 2 506±24Ma to 2 503±40Ma. The Longcaoping crystal complex was cratonized during the Lower Proterozoic, rifted, uplifted and detached from the Caledonian orogeny to the Variscan orogeny, and collided during the Indosinian orogeny. Those geologic events were documented in zircons from the Longcaoping crystal complex.