摘要
云龙成矿带位于西南"三江"中段,是该区重要的锡(钨)矿集区。本文利用LA-ICP-MS锆石U-Pb定年方法,对带内与成矿相关的二云母花岗岩进行了年龄测试,获得成岩年龄为72.2±0.8Ma(MSWD=1.9),属晚白垩世。这是在保山地块首次发现确凿的晚白垩世岩浆岩,表明保山地块经受了该时期构造-岩浆活动的影响。通过锆石微量元素和主微量地球化学特征分析,认为其应属S型花岗岩。结合区域地质背景,认为云龙成矿带该期花岗岩可能与腾冲地块晚白垩世S型花岗岩形成于一致的动力学背景,为新特提斯东向俯冲过程中内陆增厚地壳熔融的产物。本次报道的晚白垩世S型花岗岩与成矿带内一期重要成矿期次时代一致。结合前人研究资料认为,云龙成矿带内三期主要的成矿事件均有同期构造-岩浆事件对应,其中早、晚白垩世成矿活动与同期花岗岩体侵入紧密相关,而新生代成矿活动则与崇山剪切带走滑活动关系密切。这表明本区锡(钨)矿床经历了多期成矿过程,岩浆侵入活动和构造相关混合岩化对矿床形成均有贡献,单一的成因机制(花岗岩相关或混合岩化)可能无法合理解释本区矿床的成因。
Located in the middle segment of the Three River region, the Yunlong metallogenic belt is considered to be connected with the Southeast Asian giant tin belt. The authors performed LA-ICP-MS zircon U-Pb analysis of two-mica granite closely related to tin mineralization, and got a Late Cretaceous emplacement age of 72.2±0.8 Ma （MSWD=1.9）. This is the first discovery of convincible Late Cretaceous magmatism in Baoshan terrane. The two-mica granitiod in Yunlong tin metallogenic belt was emplaced in a tectonic setting identical with the setting of the Tengchong terrane, and could represent the melting products of thickened crust in the hinterland in response to the eastward subduction of the Neo-Tethys. The emplacement age of the two-mica granite reported here is synchronous with an important tin metallogenic period in the Yunlong tin metallogenic belt. These data, combined with previous reports, suggest that the three important metallogenic periods in the belt corresponded respectively to contemporaneous tectonomagmatic events. That is, the Early and Late Cretaceous ones were closely related to granitoid emplacement, whereas the Cenozoic one was related to the strike-slip shearing of the Chongshan shear zone. The genesis of tin deposits in the Yunlong tin metallogenic belt can hardly be explained by one single model （granite-related magmatic-hydrothermal or migmatitic-hydrothermal model）. Granitic magmatism and tectonic-related migmatism had both contributed to the formation of tin deposits, but they played different roles in different metallogenic periods.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2013年第4期450-462,共13页
Acta Petrologica et Mineralogica
基金
国家自然科学基金(41202048
41202067)
中国地质调查局综合研究资助项目(12120113049100
1212011220412)
