胶东地区晚中生代岩浆活动及对大地构造的制约

应用近十几年来胶东地区及其周边岩浆岩体的同位素测年资料,结合几个岩体的新的SHRIMP测年数据(牙山岩体117.7Ma,院格庄岩体113.4Ma,正长斑岩脉115.7Ma),系统研究了该区晚中生代以来的岩浆活动规律,结果表明,该区可分为4个岩浆活动期;(1)晚侏罗世构造-岩浆热事件(150~160Ma),以玲珑-滦家河型岩体为代表,是在区域挤压构造应力作用下侵入的,属同构造或同造山时期的岩浆作用。(2)早白垩世早期构造-岩浆热事件(135~125Ma),以郭家岭岩体为典型,该时期的岩浆活动均具有双峰式岩浆作用特征,反映了伸展动力学背景。(3)早白垩世中晚期构造-岩浆热事件(125~105Ma),以崂山花岗岩为特征,该阶段对应于中国东部岩石圈大规模的减薄时期,是大陆裂谷作用的高峰期。(4)晚白垩世-古新世基性-超基性火山作用。本文还探讨了岩浆活动的地球动力学因素及其对大地构造的制约。

LATE MESOZOIC MAGMATIC ACTIVITIES AND THEIR CONSTRAINTS ON GEOTECTONICS OF JIAODONG REGION

Based on isotope dating data of igneous rocks by previous studies in the past decade and zircon SHRIMP U-Pb dating of Yashan granite(117.7Ma),Yuangezhuang granite(113.4Ma),synite porphyry veins(115.7Ma),the paper studied magma activities in the Jiaolai basin and adjacent regions since the late Mesozoic.The regional isotope dating data suggested four tectonic-thermal events(magma activities):(1)Late Jurassic(150~160Ma)LingLong-Luanjiahe granite period,belonging to the syn-tectonic period dominated by compressive stress;(2)earlier Early Cretaceous(135~125Ma)Guojialing granite period,controlled by the extension setting;(3)middle-late Early Cretaceous(125~105Ma)Laoshan granite period,corresponding to the large scale lithosphere thinning;and(4)Late Cretaceous-Paleocene basic-ultrabasic magma activities.Geodynamic factors for the magma activities and their constraints on regional tectonics are also discussed in this paper.