The Nanling area is famous for its widely distributed granites. There are also many volcanic rocks there, but cretaceous volcanic rocks are rare. In this paper, based on field survey, we investigate the rock formation time of Tianxin andesitic-porphyrite by Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICPMS) zircon U-Pb dating, and determine its age to be (102. 3 ±0. 5) Ma. This result indicates that the stratum relation considered before should be adjusted, the Tianxin andesitic-porphyrite must have erupted in the late Cretaceous but not the late Jurassic period, the included sandstone breccia belongs to the early cretaceous Ganzhou group and the stratum covering on the andesitic-porphyrite belongs to the Nanxiong group, not the Ganzhou group. However, this result also indicates that, in this area, the magma activity from early to late was a reverse evolution from acid to neutral to mafic-ultra mafic during the Yanshanian period, and this might be related to the magma activity of the deep mantle, and possibly a production of tectonic event in the South China continental crust from thickening to thinning.%南岭地区是国内外著名的花岗岩和火山岩分布区,但白垩纪的火山岩相对少见.文章在野外调研的基础上,利用激光剥蚀-多接收器电感耦合等离子体质谱法(LA-MC-ICPMS)技术对位于赣南兴国幅境内的田新安山玢岩的成岩时代进行研究,确定其形成年龄为(102.3±0.5)Ma.这一结果一方面表明原先的地层关系需要调整,即安山玢岩喷发于白垩纪晚期而不是侏罗纪晚期,其中裹挟的砂岩角砾为下白垩统赣州组,而覆盖于安山玢岩之上的不是赣州组而是南雄组；同时,这一结果也表明该地区燕山期岩浆活动从早到晚由酸性到中性再到基性超基性的逆向演化,可能与地幔深部的岩浆活动有关,而且很可能代表了华南大陆内部地壳由增厚到减薄的大地构造事件的产物.
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