【摘要】 洪水河铁矿区位于东昆仑造山带中段北带。在野外地质工作的基础上,对狼牙山组近矿围岩千枚岩开展了岩相学、地球化学、LA-ICP-MS碎屑锆石U-Pb年代学及Hf同位素研究工作。主微量元素结果显示,狼牙山组千枚岩的原岩可能是一套来自壳源的成熟度高的砂岩,古气候古地理特征是温暖湿润环境,经历了中—高程度的化学风化作用,物源为碱性长石含量较低的长英质岩石,沉积构造环境可能处于被动大陆边缘。碎屑锆石年代学研究结果显示,本区狼牙山组千枚岩的沉积年龄可能为（788±9）^515.2±4.4Ma,说明其沉积时代并非前人认为的蓟县系。洪水河铁矿床应该是当时全球性含铁建造的实例之一,反映的是Sturtian冰期的结束。另外,这些碎屑锆石的εHf（t）值为-30.4⁸.3,说明Hf同位素来源组成具有极大的非均一性,两阶段模式年龄为3 596¹ 448 Ma,具有正和负的εHf（t）值,说明这类锆石的母岩中既有新生的地壳物质,又有再造的古老地壳,可能分别对应中元古代的新生地壳和太古宙地壳的再造。通过对锆石年龄分类讨论,并将碎屑锆石年龄与其邻区出露的老地层和岩体时代进行对比,推测太古宙基底物质、白沙河岩组、小庙群、万宝沟群及中元古代晚期在东昆仑地区形成的中酸性岩体为其物源。更多还原

【Abstract】 The Hongshuihe iron ore district is located in the north-middle part of the eastern Kunlun orogenic belt.On the basis of geological field work,the authors applied petrography,geochemistry,LA-ICP-MS detrital zircon U-Pb geochronology,and Hf isotope to the ore-hosting phyllite of the Langyashan Formation.The results of the main and trace elements showed that the original rocks of the phyllite of the Langyashan Formation were possibly composed of high-maturity sandstones from the crust source,showing the warm and humid paleo-climate and paleo-geographic features.The original rocks were experienced the medium-high degree chemical weathering,whose provenance was the felsic rocks with low content of alkaline feldspar.Their sedimentary tectonic environment might be on the edge of the passive continent.The detrital zircon geochronological results showed that the sedimentary age of the phyllite was between(788±9)Ma and(515.2±4.4)Ma,different from the age of Jixianian.The Hongshuihe iron deposit should be one of the examples of the global banded iron formations,which reflect the end of the Sturtian ice age.In addition,theεHf(t)values of these detrital zircons varies from-30.4 to 8.3,indicating that the composition of Hf isotope sources is highly heterogeneous,with a twostage model age of 3 596-1 448 Ma,which indicates that the source rocks of these zircons include both newborn crust material and reconstructed ancient crust material.The newborn crust might be from Mesoproterozoic,and the reconstructed crust might be from Archean.Through discussing on the classification of zircon ages and comparing the ages of some old sedimentary strata and intrusive rocks of the adjacent areas,it is inferred that the basement of Archean,Baishahe Formation,Xiaomiao Group,Wanbaogou Group and the intermediate-acid rocks formed in the eastern Kunlun in the late period of Mesoproterozoic are the possible provenances.更多还原