滇西腾冲地块东南缘早白垩世火山岩锆石U-Pb定年及地质意义

LA-LCP-MS zircon U-Pb dating and geological implications for the Early Cretaceous volcanic rocks on the southeastern margin of the Tengchong block, western Yunnan

摘要: 滇西腾冲地块东侧高黎贡变质岩带,发育一套浅变质的沉积岩地层,其时代不明。本次1:5万区域地质调查在潞西市轩岗乡团坡地层剖面中,确定了该套地层含有酸性火山岩夹层,获得火山岩的锆石U-Pb年龄为121.4±1.4Ma。这一结果表明该套地层的时代为早白垩世;同时也揭示研究区存在早白垩世火山活动,其成因可能与怒江洋盆的闭合有关。

Abstract: A succession of undated epimetamorphic sedimentary strata occurs in the Gaoligong metamorphic rock zone east of the Tengchong block, western Yunnan. The acidic volcanic rocks in these strata were identified during the 1:50 000 regional geological survey in the stratigraphic sequences of the Tuanpo section, Xuangang, Luxi, and give a zircon U-Pb age of 121.4±1.4 Ma. This age has revealed that the stratigraphic sequences cited above should be dated back to the Early Cretaceous during which the volcanic activities once took place in the study area. The Early Cretaceous felsic volcanic rocks in the study area may owe their origin to the closure of the Nujiang oceanic basin.