摘要
金沙江–哀牢山构造带在晚古生代发育的是古特提斯支洋还是弧后盆地尚存在争论,笔者对哀牢山构造带南段下泥盆统硅质岩开展岩相学、岩石地球化学等分析,以期为该地区构造演化提供新的证据。硅质岩地球化学特征显示出其为生物成因,SiO_(2)与Al_(2)O_(3)、SiO_(2)与TiO_(2)具明显负相关性,说明硅质不是来自陆源物质,具Ce负异常,Ce/Ce*值为0.73~0.76,平均值为0.75,接近大洋盆地硅质岩特征;(La/Ce)_(N)值为1.31~1.49,平均为1.38,接近开阔洋盆硅质岩特征。综合分析认为,硅质岩形成于边缘海向开阔大洋转换的环境,暗示金沙江–哀牢山构造带在晚古生代发育的是古特提斯支洋,而非弧后盆地。
There is still a debate about whether the Jinshajiang Ailaoshan tectonic belt developed in the Late Paleozoic was a Paleo Tethyan Ocean or a backarc basin.This paper conducts petrographic and geochemical analyses of the Lower Devonian siliceous rocks in the southern section of the Ailaoshan tectonic belt in order to provide new evidence for the tectonic evolution of the area.The geochemical characteristics of siliceous rocks show that they are biogenic,with a significant negative correlation between SiO_(2) and Al_(2)O_(3),and SiO_(2) and TiO_(2),indicating that siliceous rocks do not come from terrestrial sources and have a negative Ce anomaly.The Ce/Ce*value is 0.73 to 0.76,with an average value of 0.75,which is close to the characteristics of siliceous rocks in ocean basins;The LaN/Ce_(N) value ranges from 1.31 to 1.49,with an average of 1.38,which is close to the charac-teristics of siliceous rocks in open ocean basins.Based on comprehensive analysis,it is believed that the siliceous rocks were formed in a transitional environment from marginal seas to open oceans,suggesting that the Jinshajiang Ailaoshan tectonic belt developed in the Late Paleozoic in the Paleo Tethyan Ocean rather than in a backarc basin.
作者
孙崇波
周洪兵
谢万洪
李敏同
杨洪伟
SUN Chongbo;ZHOU Hongbing;XIE Wanhong;LI Mintong;YANG Hongwei(Sichuan Institute of Metal Geology,Chengdu 611730,Sichuan,China;ZHOU Hongbing Youth Innovation Studio,Chengdu 611730,Sichuan,China)
出处
《西北地质》
北大核心
2025年第5期140-150,共11页
Northwestern Geology
基金
中国地质调查局项目“西南三江成矿带南段基础地质调查”(1212010880406、1212011120582)资助。
关键词
哀牢山构造带南段
放射虫硅质岩
形成环境
哀牢山支洋
southern Ailaoshan tectonic belt
radiolarian bedded chert
depositional environments
Ailaoshan branch
