江西寻乌破火山口火山-侵入杂岩SHIRMP锆石U-Pb年龄及其地质意义

The SHRIMP Zircon U-Pb Dating and Its Geologicai Significance on the Volcanic-intrusive Rocks in Broken Crater of Xunwu,Jiangxi Province

位于武夷隆起带和南岭构造带过渡部位、受NE向会昌—寻乌断裂带和EW向三南—寻乌断裂带控制的寻乌破火山口发育一套由碎斑熔岩和花岗斑岩组成的火山-侵入杂岩。SHIRMP锆石U-Pb定年结果显示,寻乌破火山口碎斑熔岩的年龄为(96.7±1.1)Ma,花岗斑岩的年龄为(97.3±0.9)Ma,根据国际地质年代表,早白垩世与晚白垩世之间的界限定为(99.6±0.9)Ma,寻乌破火山口火山-侵入杂岩的地质时代属晚白垩世早期。火山-侵入杂岩地质时代的厘定,为将其归入优胜组提供了年代学依据。

Xunwu broken crater located in the transition zone of Wuyi rise belt and Nanling tectonic belt, controlled by the NE direction Huichang-Xunwu fault belt and the EW direction Sannan-Xunwu fault belt, and developed a volcanic-intrusive rocks that made up of porphyroclastic lava and granite-porphyry. The zircon U-Pb dating with a higher accuracy yields the following results： the age of pyroclastic rocks in the volcanic-intrusive rocks in broken crater is （96.7 ± 1.1 ） Ma and the age of granite-porphyry is （97.3 ± 0.9 ） Ma. According to the geological chronology, the boundary between the Early Cretaceous and the Late Cretaceous is （99.6 ± 0.9） Ma, the geological age of the volcanic-intrusive rocks of Xunwu broken crater is early Late Cretaceous. Age determinations of the volcanic-intrusive rocks provide the age evidence for Xunwu broken crater which belong to Yousheng formation.