There are two late Mesozoic volcanic rock belts with EW striking in Jiangxi Provinc and Northern Guangdong Provinc, called Xiajiang-Guangfeng volcanic rocks belt in the North and Sannan (Quannan, Dingnan and Longnan)- Xunwu volcanic rocks belt in the South, respectively. There are a little of the trachyte on Shixi Basin in Xiajiang- Guangfeng volcanic rocks belt and Sanbaishan Basin,Dachangsha Basin in Sannan-Xunwu volcanic rocks belt. The zircons of the trachyte have clear ring and high Th/U ratio which belong to the typical magmatic zircons. The Zircon SHRIMP U-Pb age of the Trachyte is 137.0 ±0. 94 Ma in Shixi Basin, 142 ± 1 Ma in Sanbaishan Basin, 135.4 ± 1.5 Ma in Dachangsha Basin, which represent the diagenetic ages of volcanic rocks. On the latest International Stratigraphic Chart. the boundary of Jurassic and Cretaceous is 145.4±4.0 Ma,the geological ages of the Trachytes in the Xiajiang-Guangfeng and Sannan-Xunwu Volcanic Belts are early Early Cretaceous. The large-scale high-K calc-alkaline felsic volcanic activity and volcanic-granite uranium deposit related to alkali metasomstism uranium mineralization occurred in the early Early Cretacous inthe XiajiangGuangfeng and Sannan-Xunwu Volcanic Belts. The determination of the Early Cretacous trachytes show that high-K calc-alkaline felsic volcanic activity have connection with mantle magmatic activity and Alkali metasomstism. Uranium mineralization haveconsistent with the Alkali magmatic activity.%江西及广东北缘呈近EW向展布的峡江-广丰火山岩带和三南(全南、定南、龙南)-寻乌火山岩带,是我国东南部中生代以高钾钙碱性长英质火山岩为主体的火山岩带的组成部分.峡江-广丰火山岩带的石溪盆地、三南-寻乌火山岩带的三百山盆地和大长沙盆地出露少量粗面岩,粗面岩所含锆石具有明显的振荡环带,Th/U比值高,属典型的岩浆成因锆石.SHRIMP锆石U-Pb年龄测定结果表明,石溪、三百山和大长沙粗面岩的形成年龄分别为137.0±0.94Ma、141.6±0.96Ma和135.4±1.50 Ma,根据国际地层表,属早白垩世早期.中国东南部中生代大规模高钾钙碱性长英质火山活动发生在早白孚世早期,江西及广东北缘绢英岩型铀矿也形成于早白垩世早期(120～140Ma),石溪、三百山和大长沙早白垩早期粗面岩地质时代的厘定,说明高钾钙碱性长英质火山活动与幔源岩浆活动有关、绢英岩型铀矿化与碱性岩浆活动合拍.粗面岩的地质时代与钙碱性长英质火山岩和碱交代型铀矿化的地质时代一致,为钙碱性长英质火山岩的成因与幔源岩浆活动有关提供了岩石学证据,也为绢英岩型铀矿化的成因可能与幔源流体活动有关提供了旁证.
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