泰山地区古元古代末期基性岩墙形成时代厘定——斜锆石U-Pb精确定年

Emplacement age of the gabbro-diabase dike in the Hongmen scenic region of Mount Tai,Shandong Province,North China:Baddeleyite U-Pb precise dating

华北克拉通经过吕梁运动在～1.85Ga完成克拉通化,之后从1.80Ga至1.32Ga发育大量标志哥伦比亚超级大陆裂解的地质记录。本文利用高精度热电离质谱法(ID-TIMS)和离子探针质谱法(SIMS),对发育于泰山红门景区的辉长辉绿岩墙进行了斜锆石U-Pb同位素年龄测定,获得了在误差范围内一致的辉长辉绿岩侵位年龄1621.1±8.8Ma(ID-TIMS)和1632.4±4.2Ma(SIMS)。该研究成果修正了前人对泰山红门景区辉长辉绿岩侵位年龄的模糊认识,证明了红门景区辉长辉绿岩是与华北克拉通南缘龙王碱性花岗岩、华北克拉通北缘大红峪期碱性火山岩和岩床同期的岩浆事件的产物,是哥伦比亚超级大陆初始裂解作用在华北克拉通的岩浆作用响应。

A series of 1.80~1.32Ga geological events marking the break-up of the Columbia Supercontinent took place in the North China Craton after cratonization by ca.1.85Ga through the Lüliang Orogeny.Among them mafic dike swarms are one type of representative geological records formed during the initial rifting period of the Columbia Supercontinent.The gabbro-diabase dike occurred in the Hongmen Scenic Region of Mount Tai,western Shandong Province,was probably formed during the initial rifting period of Columbia,but with very poor age constraints.By means of two modern dating methods of ID-TIMS and SIMS,the authors of this paper analyzed baddeleyite U-Pb isotopic ages of the gabbro-diabase dike;two consistent ages with error were obtained,1621.1±8.8Ma（ID-TIMS） and 1632.4±4.2Ma（SIMS）.This achievement leads to amendment of the previous imprecise emplacement timing of the Hongmen gabbro-diabase dike.It is demonstrated that the Hongmen gabbro-diabase dike is coeval with the Longwangzhuang alkaline granite in the southern margin of the North China Craton and the Dahongyu Stage alkaline volcanics and sill in the northern margin of the North China Craton;confirmed to be the product during the initial rifting period of the Columbia Supercontinent.