承德哈叭沁铁矿中硫化物特征及成因  

Characteristics and genesis of sulfides associated with magnetite in Habaqin iron deposit,Chengde

作　　者：刘文美 郑建平[1] LIU Wen-mei;ZHENG Jian-ping(School of Earth Sciences,China University of Geosciences,State Key Laboratory of Geological Processes and Mineral Resources,Wuhan 430074,China)

机构地区：[1]中国地质大学地球科学学院,地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《岩石矿物学杂志》2025年第2期361-373,共13页Acta Petrologica et Mineralogica

基　　金：国家重点研发计划(2023YFF0804404);国家自然科学基金项目(42320104001)。

摘　　要：由于成因上的差异,岩浆型硫化物和氧化物矿床很少相伴出现,因此研究两者的共存机制对于了解幔源岩浆的成矿作用有重要意义。河北承德是我国重要的岩浆型矿产资源富集区,哈叭沁铁矿中出现了磁铁矿-硫化物共存的现象,前人对磁铁矿开展了较深入的研究,但对硫化物的研究很少。为此本文在对其寄主角闪石岩开展岩相学工作的基础上,进行了硫化物主、微量和S同位素以及角闪石和磷灰石的Sr同位素等测试,以揭示硫化物的成因。角闪石岩具堆晶结构,主要由角闪石(80%~85%,体积分数)、磁铁矿(10%~15%)、磷灰石(3%~5%)和少量硫化物(<5%)组成。磁铁矿呈堆积粒状、硫化物呈稀疏浸染状(<5%)。硫化物主要为黄铁矿,其内部可见磁铁矿和磷灰石包裹体,指示硫化物结晶较晚。黄铁矿的S和Fe质量分数分别为52.0%~53.0%和45.4%~46.5%,有较高的Co(达1.68%)含量,指示其岩浆熔离作用并伴有热液影响的特征。角闪石和磷灰石的初始87Sr/86Sr值分别为0.70582~0.70830和0.70616~0.70809,黄铁矿的δ34S值变化范围为-2.8‰~+1.3‰,指示角闪石岩及其中的硫物质主要来源于富集岩石圈地幔;硫饱和主要受控于母岩浆的分离结晶及相关的岩浆系统变化。磁铁矿的结晶作用导致硫化物饱和度延迟,特别是在缺乏地壳物质加入的情况下,硫化物结晶明显少于氧化物。Magmatic sulfide and oxide deposits rarely commonly appear due to their different genetic mechanism,and the studies about their co-existence mechanism are important for understanding the mineralization of mantle-derived magmas.Chengde,Hebei Province is an important magmatic mineral resource rich area in China.Sulfides coexisting with magnetite appear in Habaqin iron deposit,and the magnetite has been studied,but few studies on sulfide are involved.We carried out the major and trace elements,and in situ S isotopes of sulfides as well as in situ Sr isotopes of amphibole and apatite on the basis of petrography of host hornblendite,to reveal the genesis of sulfides.The hornblendite shows cumulate texture and consists of amphibole(80%~85%by volume),magnetite(10%~15%),apatite(3%~5%),and minor sulfides(<5%).The magnetite appears as granular aggregates and sulfides as sparse disseminations(<5%).The sulfides are mainly pyrite with inclusions of magnetite and apatite,suggesting that sulfides crystallized at late stage.The contents of S and Fe in pyrites range from 52.0%to 53.0%and 45.4%to 46.5%,respectively,with higher concentration of Co(up to 1.68%),suggesting its formation is controlled by magmatic segregation,accompanied by slight magmatic hydrothermal process.The initial^(87)Sr/^(86)Sr ratios of amphibole and apatite range from 0.70582 to 0.70830 and 0.70616~0.70809,respectively,and theδ^(34)S values of pyrites range from-2.8‰to+1.3‰,suggesting that the hornblendite and its sulfur mainly originate from an enriched lithospheric mantle;sulfur saturation is primarily controlled by the fractional crystallization of the parental magma.The crystallization of magnetite leads to delayed sulfide saturation,and weak assimilation and contamination of crustal material results in weak sulfides separation compared to oxides.

关 键 词：硫化物 角闪石岩 磁铁矿 硫同位素 SR同位素 华北 

分 类 号：P578.2[天文地球—矿物学] P579[天文地球—地质学]