投稿时间：2016-10-03
修订日期：2017-07-11
网络发布日期：2017-11-06
中文摘要:龙桥铁矿床是长江中下游成矿带内的大型铁矿床，主矿体呈似层状赋存于三叠系东马鞍山组泥灰岩、角砾状灰岩和泥质粉砂岩中，单个矿体铁矿石资源量大于1亿吨，具有鲜明的成矿特色。前人研究认为，矿区内正长岩类侵入岩与成矿关系密切，龙桥矿床是成矿带内唯一与正长岩有关的大型铁矿床。随着生产勘探，在矿床中部井下巷道中发现辉长闪长岩侵入体，为矿床成因以及成矿模式提供了新的线索。文章在详细的野外地质工作基础上，开展了辉长闪长岩的岩石学、地球化学和年代学研究。辉长闪长岩岩体呈岩株状产出，被正长岩体穿切破坏，靠近矿体部位发育透辉石矽卡岩化蚀变。辉长闪长岩主要由拉长石（60%）、钾长石（10%）、普通辉石（10%）和角闪石（5%）组成；与正长岩相比，辉长闪长岩明显具有低硅、低钾、高镁铁特征。锆石LA ICP-MS定年结果表明其成岩时代为（133.5±0.8）Ma。在前人对龙桥矿床研究的基础上，笔者认为龙桥铁矿床辉长闪长岩与铁成矿作用关系更为密切，成岩成矿作用几乎同时发生，而正长岩为成矿期后破矿岩体。通过与庐枞矿集区和长江中下游成矿带内铁矿床对比表明，庐枞矿集区内大型铁矿床与正长岩无成因联系，而闪长质侵入岩则是庐枞矿集区内重要的成矿母岩。龙桥铁矿床与长江中下游成矿带庐枞、宁芜矿集区内玢岩型铁矿床以及鄂东南矿集区内矽卡岩型铁矿床在成岩成矿时代方面相近，属长江中下游第二期成岩成矿作用的产物。闪长质侵入岩是成矿带内矽卡岩型及玢岩型铁矿成矿的必要条件，而正长岩类侵入岩的形成大多晚于闪长岩，与铁成矿作用无直接关系。
Abstract:The Longqiao iron deposit is a large iron deposit in the middle and lower reaches of the Yangtze River metallogenic belt. The main orebody is located in marlite, brecciated limestone and argillaceous siltstone of Triassic Dongmaanshan Formation, the single iron orebody resources have reached more than 100 million tons, with distinct metallogenic characteristics, but its genesis remains a problem of much controversy. Previous researchers thought that syenite intrusion in the mining area is closely related to mineralization. During the exploration of the Longqiao iron deposit, the authors found gabbro diorite in the depth of the central part of the deposit, thus providing new clues to the genesis of the Longqiao deposit. In this paper, the authors carried out petrologic, geochemical and chronological study of gabbro diorite on the basis of detailed geological field work. Gabbro diorite rock occurs as a stock, and is cut by syenite. Some near-ore parts develop diopside skarn alteration. Gabbro diorite is composed mainly of feldspar (60%), potassium feldspar (10%), augite (10%), and hornblende (5%). Compared with syenite, gabbro diorite obviously has characteristics of low silicon, low potassium and high iron content. Zircon LA ICP-MS dating results show that the gabbro diorite age is (133.5±0.8) Ma. Based on previous researches on the Longqiao deposits, the authors hold that gabbro diorite is closely related to mineralization of the Longqiao deposit, diagenetic and metallogenic processes took place almost at the same time, and syenite as a later intrusion cut across the orebody. Through a comparison with Lu-Zong volcanic basin and other iron ore deposits, the authors consider that the syenite had nothing to do with mineralization, and diorite intrusive rock was the mother rock of mineralization in Lu-Zong volcanic basin. The Longqiao iron ore deposit is close to Lu-Zong basin, Ningwu porphyrite type iron ore deposit and southeast Hubei skarn type iron ore deposit in diagenetic and metallogenic epoch, belonging to the second period product of the mineralization and diagenetic activities in the middle and lower reaches of the Yangtze River metallogenic belt. Diorite intrusive rock was a necessary condition for the skarn and porphyrite iron ore mineralization in the metallogenic belt. Syenite intrusive rocks were later than the second stage of magmatism and mineralization, and hence had nothing to do with the iron mineralization.
keywords:geochemistry Longqiao iron deposit diorite diagenetic and metallogenic epoch skarn deposit Lu-Zong Basin
文章编号：
中图分类号：P618.31
文献标志码：
基金项目:本文得到国家重点研发计划（批准号：2016YFC0600206）、国家自然科学基金项目（批准号：41672081、41320104003、41172084）和安徽省国土资源科技项目（批准号：2015-K-2、2015-K-3）的资助
引用文本：
刘一男,范裕,周涛发,洪浩澜,张维,欧邦国.2017.安徽龙桥铁矿床辉长闪长岩的发现及其岩石学和年代学研究[J].矿床地质,36(5):1127~1142LIU YiNan,FAN Yu,ZHOU TaoFa,HONG HaoLan,ZHANG Wei,OU BangGuo.2017.Discovery of gabbro diorite in Longqiao deposit of Lu-Zong volcanic Basin, eastern China, and its petrology and chronology[J].Mineral Deposits36(5):1127~1142
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