| 怀安杂岩中含BIF岩石组合的形成时代及产出构造背景 |
| |
| 引用本文： | 田辉,张家辉,王惠初,任云伟,王权.怀安杂岩中含BIF岩石组合的形成时代及产出构造背景[J].地球科学,2019,44(1):37-51. |
| |
| 作者姓名： | 田辉 张家辉 王惠初 任云伟 王权 |
| |
| 作者单位： | 1.中国地质调查局天津地质调查中心, 天津 300170 |
| |
| 基金项目： | 中国地质调查局二级项目DD20160042 |
| |
| 摘 要： | 华北克拉通北部的怀安杂岩中分布着一些呈团块状、透镜状或似层状产出的含BIF岩石组合.相对于华北克拉通绿岩带，研究区内的含BIF岩石组合具有规模小、岩性复杂多样以及后期叠加强烈的变质-变形改造等特点，其研究程度较低.在野外地质填图的基础上，通过岩石学、同位素年代学、地球化学研究表明:（1）天镇-怀安地区的含BIF岩石组合主要由条带状（含辉石/角闪）磁铁石英岩、变质基性火山岩（二辉麻粒岩/含辉石斜长角闪岩/高压麻粒岩）、石榴黑云斜长片麻岩和少量石榴石英岩条带或团块组成，这些岩石彼此呈夹层或互层状伴生产出；天镇-怀安地区BIF矿体规模小、与变质火山岩密切共生等特征表明其属于Algoma型.（2）条带状（含辉石/角闪）磁铁石英岩中残留的中-基性火成岩锆石年龄（2 489±19 Ma）可代表含BIF岩石组合的形成时代，并经历了1 800~1 850 Ma变质作用叠加改造.（3）含BIF岩石组合中火山岩地球化学特征显示Rb、Ba、U、Pb等元素富集和Nb、Ta等元素亏损，结合微量元素蛛网图和稀土配分模式对比认为其产出构造背景为弧后盆地，铁矿石PAAS标准化稀土配分图解具有明显Eu正异常，表明与海底热液活动密切相关.
|
| 关 键 词： | 天镇-怀安地区 含BIF岩石组合 U-Pb定年 地球化学 岩石学 |
| 收稿时间： | 2018-06-25 |
Formation Age and Tectonic Setting of Iron-Bearing Formation in Huai'an Complex,North China Craton |
| |
| Abstract: | Iron-bearing formations (BIFs) in lumpy, lenticular or stratified forms frequently occur in the Huai'an Complex, North China Craton. Compared with BIFs in greenstone belts on North China Craton, the iron-bearing formation with characteristics of small scale, complicated lithology, and high-grade metamorphism-deformation in the study area has rarely been studied. Petrology, geochronology and geochemical studies on the basis of field survey have been conducted, and it is concluded:(1) The iron-bearing formations in Tianzhen-Huai'an area are comprised of banded (perilla/amphibole) magnetic quartzite, metamorphic basic volcanic rock (two-pyroxene granulite/plagioclase amphibolites/high-pressure granulite), garnet-biotite-plagiogneiss, and a few garnet-quartzite strips or lumps, and these rocks are intercalated or symbiotic with each other. Characteristics of being small in scale, closely symbiotic with metamorphic volcanic rocks suggesting BIF ore in Tianzhen-Huai'an area belongs to Algoma type. (2) The age (2 489±19 Ma) of residual intermediate-basic igneous zircons in banded (perilla/amphibole) magnetic quartzite may represent the formation age of the BIFs in Tianzhen-Huai'an area, which afterwards underwent the 1 800-1 850 Ma metamorphism. (3) The geochemical characteristics of metamorphic volcanic rocks of iron-bearing formations show enrichment in elements Rb, Ba, U, Pb, and depletion in elements Nb and Ta. It is concluded the iron-bearing formations are closely related to seabed hydrothermal activity formed in back-arc basin according to the patterns of trace elements and rare earth distribution of metamorphic volcanic rocks and positive anomality of Eu in PAAS normalized rare earth elements distribution pattern of iron ore. |
| |
| Keywords: | |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《地球科学》浏览原始摘要信息 |
|
点击此处可从《地球科学》下载全文 |
|
