东南沿海晚白垩世火山岩浆活动特征及其构造背景

东南沿海晚白垩世火山岩浆活动微弱，研究程度不高，但构造意义重要。对浙闽沿海晚白垩世小雄组和石牛山组火山岩及其共生侵入岩类进行了较系统研究。测得小雄破火山中央侵入相正长斑岩和石牛山破火山中央侵入相正长花岗斑岩的锆石年龄分别为87.9±1.2Ma和93.8±1.3Ma；岩石学和地球化学特征表明，小雄组和石牛山组火山岩及其共生侵入岩类均属后造山A型花岗质岩类，它们是在东南沿海巨型白垩纪A型花岗岩带主体形成之后、岩石圈进一步强烈伸展的背景下形成的，是区域中生代最晚期的酸性火山岩浆活动产物，标志着燕山造山过程最终结束于约90Ma。

Characteristics and tectonic setting of Late Cretaceous volcanic magmatism in the coastal Southeast China

Late Cretaceous volcanic magmatisms in the coastal Southeast China are weak and lack enough studies, but have significant tectonic implications. This paper reports studies on Late Cretaceous Xiaoxiong Formation and Shiniushan Formation volcanic rocks and associated plutonic rocks in Zhejiang and Fujian provinces. Zircon ages of both central intrusion facies syenite-porphyry at Xiaoxiong caldera and syenogranite-porphyry at Shiniushan caldera are 87.9±1.2Ma and 93.8±1.3Ma respectively. Based on their petrological and geochemistric features, these rocks are proved to be post-orogenic A-type granitoids. They were generated during intenser extension of lithosphere after formation of the huge Cretaceous A-type granite belt in the coastal Southeast China, and belong to the latest felsic magmatism in Mesozoic. It is inferred that the Yanshanian orogeny ended at ca. 90Ma.