桂东北贺州英安岩锆石年代学、Hf同位素研究及其地质意义

研究区位于南岭成矿带西段湘—桂交界处,该区中生代岩浆活动频繁,成岩成矿作用显著,尤以燕山期最为强烈.为厘定桂东北贺州开山镇孔子庙英安岩的成岩时代和探讨其岩浆源区,文章对其进行了LA-ICP-MS锆石U-Pb定年和锆石Lu-Hf同位素研究.锆石U-Pb定年结果限定了英安岩的侵位年龄为157.1±0.9 Ma.锆石Lu-H...

LA-ICP-MS Zircon U-Pb Dating and Hf Isotopic Composition of Dacite in Hezhou,Northeastern Guangxi

The study area is located at the junction of Hunan and Guangxi in the western part of Nanling metallogenic belt, where Mesozoic magmatic activity is frequent and the diagenesis and mineralization are remarkable, especially during Yanshanian. In order to determine the formation age of kongzimiao dacite in Kaishan Town, Hezhou, northeastern Guangxi, and to discuss its source property, LA-ICP-MS zircon U-Pb dating and Lu-Hf isotope are obtained. zircon U-Pb age of 157.1±0.9 Ma displayed the formation age of the dacite. Zircons grains have a wide range of isotopic composition (εHf(t) values rang from -5.68 to -0.97), with corresponding two-stage Hf isotope model age (TDM2) varying from 1.26~1.54 Ga, suggesting that the protolith was predominantly derived from the crystalline basement crust in Mesoproterozoic, and may be accompanied by a small amount of mantle-derived materials. Combined with the previous studies on the Yanshanian diagenesis and mineralization in South China, it is considered that the dacite in the study area and the early Yanshanian rocks and deposits in Northeast Guangxi are the products of the first large-scale magmatic activity in the Yanshanian in South China, and the formation of dacite may be related to the intraplate extension thinning of the Yanshanian lithosphere in South China.