投稿时间：2015-07-13
修订日期：2016-08-15
网络发布日期：2016-10-29
中文摘要:河南舞阳地区赵案庄铁矿床是产于超基性岩中的隐伏矿床。超基性岩侵位于新太古界太华群赵案庄组透辉斜长角闪片麻岩中。矿体呈似层状，具有多层。矿石成分较复杂，主要矿物为磁铁矿、蛇纹石、氟磷灰石等。矿床规模为中等，其成因是与超基性岩有关的岩浆晚期磷灰石-磁铁矿矿床。在磷灰蛇纹磁铁矿石中选出的锆石样品为变质锆石，利用激光烧蚀多接收器电感耦合等离子体质谱仪（LA-MC-ICPMS）进行微区原位U-Pb同位素测年，获得不一致线的上交点年龄为（1943±5）Ma（MSWD=2.3）。同时对锆石阴极发光（CL）图像研究，表明该年龄代表锆石遭受强烈变质作用的年龄，可以限定矿体形成时代的上限，即矿体形成时代不晚于1943 Ma。超基性岩浆演化晚期，岩浆充填构造裂隙呈透辉石岩脉产出。透辉石脉与矿体同期并且穿切铁山庙组BIF型铁山铁矿。铁山庙组形成时代在2300~2500 Ma之间。透辉石岩脉形成时代不早于该组年龄，可作为赵案庄铁矿床形成时代的下限。赵案庄铁矿床的形成时代为1943~2300 Ma，为古元古代，这是中国目前发现的最古老的岩浆型铁矿床。该成矿地质时代反映了在华北陆块东南缘曾发生过一次地壳扩张和裂陷活动及华北克拉通裂解事件。
Abstract:The Zhaoanzhuang iron ore deposit in Wuyang area is a concealed deposit that occurs in ultrabasic rocks. The ultrabasic rock intruded into the diopside plagioclase hornblende gneiss of the Zhaoanzhuang Formation of Neoarchean Taihua Group. The orebody is stratoid, with multi-layers. The mineral components of the ore are complex and the main minerals are magnetite, serpentine, apatite and some others. This medium-sized deposit is genetically a late magmatic apatite-magnetite deposit related to ultrabasic rocks. The zircons separated from the apatite-serpentine magnetite ore yielded a discordant line upper intercept age of (1943±5) Ma (MSWD=2.3) by means of LA-MC-ICPMS. Combined with the CL image study, it should represent the metamorphic age when the rock suffered a strong metamorphism. The metamorphic age is the upper limit of the ore deposit formation. In other words, the metallogenic epoch should be earlier than 1943 Ma. At the late stage of ultra-mafic magmatic evolution, the magma filled structural fissures as diopside rock vein cutting the BIF iron deposit of Tieshanmiao Formation. The age of Tieshanmiao Formation is 2300~2500 Ma. Therefore the age of the diopside vein is not earlier than that of the Tieshanmiao Formation, and is the lower limit of the metallogenic epoch of the Zhaoanzhuang iron ore deposit. Hence the metallogenic epoch of the Zhaoanzhuang iron ore deposit should be 1943~2300 Ma, in Paleoproterozoic. It is the oldest magmatic iron ore deposit discovered in China so far. The metallogenic epoch implies that there existed an expansion and rifting event on the southeast margin of the North China block.
keywords:geochemistry magmatic type iron ore deposit zircon LA-MC-ICPMS U-Pb dating geological significance Zhaoanzhuang iron ore deposit Wuyang area in Henan
文章编号：
中图分类号：P618.31
文献标志码：
基金项目:本文得到中国地质调查局中国区域成矿规律研究与总结项目（编号：12120114039701）资助
引用文本：
张阔,沈保丰,孙丰月,周红英,李怀坤.2016.河南舞阳地区赵案庄铁矿床成矿时代及地质意义——中国最古老的岩浆型铁矿床[J].矿床地质,35(5):889~901ZHANG Kuo,SHEN BaoFeng,SUN FengYue,ZHOU HongYing,LI HuaiKun.2016.Metallogenic epoch of Zhaoanzhuang iron ore deposit in Wuyang, Henan Province: Oldest magmatic type iron ore deposit in China[J].Mineral Deposits35(5):889~901
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