内蒙古四子王旗黑脑包岩体年代学与地球化学特征及其构造演化

GEOCHRONOLOGY AND GEOCHEMISTRY OF THE HEINAOBAO PLUTON IN SIZIWANGQI,INNER MONGOLIA AND ITS TECTONIC EVOLUTION

内蒙古四子王旗黑脑包岩体位于华北板块北缘早古生代增生造山带,主要由花岗闪长岩和花岗斑岩组成。对花岗闪长岩进行La-ICP-MS锆石U-Pb定年,获得四子王旗黑脑包侵入岩体的2个侵位年龄为407.4±4.7 Ma和268.0±2.7 Ma,分别代表洋陆俯冲事件以及陆陆碰撞事件年龄。岩石地球化学数据显示,四子王旗黑脑包岩体属钙碱性系列,逐步向低钾拉斑系列靠近,并且亏损高场强元素。同位素地质年龄及地球化学数据表明,样品具有同碰撞花岗岩特征。结合区域大地构造背景认为,四子王旗黑脑包地区主要构造背景为西伯利亚板块与华北板块之间俯冲、碰撞和对接过程,属古亚洲洋构造域,而后期的构造演化还有待进一步研究。

Heinaobao granitoid in the Siziwangqi area of Inner Mongolia tectonically belongs to Early Paleozoic hyperplasia plate in the northern margin of the North China plate.The granitiod is predominantly of composed of granodiorite and granote porphyry.The La-ICP-MS U-Pb zircon dating method and petrochemical analysis were used to study and understand its formation age and nature.As a result,zircons from granodiorite U-Pb ages of 407.4±4.7 Ma and 268.0±2.7 Ma,the first age represents the one event of ocean-continent subduction and the second age represents the one event of continent-continent collision.Petrochemistry date indicated that the Heinaobao rock in Siziwangqi belongs to the calc-alkaline series,and gradually near to the hypokalemic Tholeiitic series,depleted in high field strength elements.Geochrono logical and petrochemical data implied that the samples had syn-collisional characteristics.Combined with regional tectonic background,the tectonic background of Heinaobao Sizwangqi is the subduction,collision and docking of Siberian plate and North China Plate,it belongs to Paleo-Asian Ocean tectonic domain,while the late tectonic evolution remains to be further research.