云南景谷半坡铂钯多金属矿床辉长岩锆石U-Pb同位素定年及其意义  

Zircon LA-ICP-MS U-Pb dating of gabbro of the Banpo Pt-Pd-polymetallic deposit in Jinggu, Yunnan Province, and its geological significance

作　　者：张海[1] 金灿海[1] 范文玉[1] 沈战武[1] 张玙[1] 高建华[1] 

机构地区：[1]成都地质矿产研究所,四川成都610081

出　　处：《中国地质》2013年第5期1433-1442,共10页Geology in China

基　　金：中国地质调查局地质调查项目(12120113037000;1212011120608)资助

摘　　要：景谷半坡铂钯多金属矿床位于澜沧江南段兰坪—思茅陆块,成矿主要与半坡杂岩体有关。半坡杂岩体由橄榄岩、辉石岩、辉长岩、辉长闪长岩和闪长岩等镁铁-超镁铁质岩组成。通过LA-ICP-MS锆石U-Pb同位素年代学方法获得半坡杂岩体中辉长岩结晶年龄为(302.6±2.0)Ma,说明半坡杂岩体形成时代为晚石炭世。岩体中辉长岩属高铝质基性岩类,轻稀土元素相对于重稀土元素弱富集,富集大离子亲石元素(Rb、Sr、K、Ba)、亏损高场强元素(Nb、Ta、Zr、Hf),具有岛弧岩浆岩性质,表明半坡杂岩体形成与板块俯冲有关的岛弧环境,南澜沧江构造带在晚石炭世至早二叠世为大洋岛弧俯冲带。The Banpo Pt-Pd Complex Deposit of Jinggu is located in Lanping-Simao landmass along the southern part of the Lancang River. Its mineralization is related to Banpo complex. This complex mainly consists of mafic-nltramafic rocks such as peridotite, pyroxenite, gabbro, gabbro diorite and diorite. U-Pb age of zircons from the gabbro determined by LA-ICP-MS is 302.6＋2. 0 Ma, indicating that Banpo Complex was formed in Late Carboniferous. The gabbro belongs to high aluminum basite. The rock samples are all characterized by slight enrichment of light rare earth elements relative to heavy rare earth elements, the enrichment of ion lithophile elements （tkb, Sr, K, Ba） and the depletion of high field strength elements （N-b, Ta, Zr and Hf）. These characteristics are typical of island arc magmas and indicate that Banpo complex was formed in an island-arc environment related to plate subduction. Therefore, southern Lancang River is considered to have been an oceanic island arc subduction belt between the late period of Late Carboniferous and the early period of Early Pemaian.

关 键 词：辉长岩 锆石 LA-ICP-MS U-PB定年 景谷半坡 

分 类 号：P618.53[天文地球—矿床学] P597.3[天文地球—地质学]