摘要
对来自祁连与秦岭造山带交接部位秦安地区葫芦河流域的“葫芦河群”浅变质砂岩中大量碎屑锆石的LA-ICP—MS U—Pb测年结果发现，其中含有年龄为2302～2578Ma的锆石颗粒。这些锆石年龄均十分谐和，且阴极发光图象上显示具有典型岩浆型振荡环带结构和岩浆成因锆石的w（Th）／w（U）为0．11～1．42，表明这些锆石为新太古代末期构造岩浆作用的产物。这些锆石是该区域迄今发现的最古老的锆石，表明祁连与秦岭造山带交接部位可能存在比陇山岩群和泰岭岩群更古老的陆斋．
Through LA-ICP-MS U-Pb dating of a large number of detrital zircon grains from metamorphic sandstones of Huluhe Group in the Huluhe River of the Qin＇an area, the conjoint area between Qilian and Qinling orogenic belts, 2 302～2 578 Ma zircon grains were identified. Their ^207Pb/^208Pb and ^206Pb/^238U ages coincide well, and CL images exhibit well-developed oscillatory zoning and the Th/U ratios are within 0. 11 ～ 1.42, implying that they are tectonomagmatic zircons which formed during late Newarchaeozoic. These zircons are the oldest ones discovered in the conjoint area between Qilian and Qinling orogenic belts up to now, which suggests the presence of crust older than high-grade metamorphic Longshan and Qinling groups in the conjoint area between Qilian and Qinling orogenic belts.
出处
《地球科学与环境学报》
CAS
2007年第2期111-116,共6页
Journal of Earth Sciences and Environment
基金
国家自然科学基金项目(40572121
40234041)
教育部科技重点项目(104175)
中国地质调查局地质调查项目(200013000154)
