内蒙古大苏计和曹四夭大型钼矿床的发现及意义_聂凤军

Abstract
Located in Liang cheng uplif t of Inner M ongolian massif (Axis)w it hin t he Northern China craton , t he new ly discovered Dasuji and Caosiy ao deposits are large-size and superlarge M o deposi ts in central Inner Mong olian , respectively .During the Mesozoic Indosinian and Yanshanian orogenies, intensive tectonic and igneous activi ties resulted in large-scale granitoid magm atism in t he Dasuji and Caosiyao mineralized dist ricts .T he granitoid porphyry stocks and dyke sw arms w ere emplaced in the Achaean met amorphic rocks of the Jining Group . T here exist no dif ferences in o re-bearing intrusions in the Dasuji and Caosiyao mineralized dist ricts .T he orebearing grani toid int rusions consist of quart z porphy ry , syenog ranite porphy ry and grani te po rphyry .Rockforming minerals are mainly quartz , microcline , micropert hite and plagioclase associated w ith mino r biotite and sericite .Accessory minerals are m agneti te , apatite , zi rcon , sphene and allanite .T he porphy ry stocks are petrochemically characterized by relatively high SiO 2 , K2O , Rb , N b and U , obviously low CaO , Fe2O3 +FeO , M gO , Sr , Ba , T a and REE , belo nging to silicon-high , pot assium-rich rock of calc-alkaline series .Molybdenum mineralization occurs in bo th Achaean met amorphic rocks and g ranitoid po rphyry stocks as veins , veinlets and
(1 中国地质科学院矿产资源 研究所 国土资源部成矿作用与资源评价重点实验室 , 北京 100037; 2 石家庄经济学院 , 河 北 石家庄 050031)
摘 要 大苏计矿床和曹四夭矿床是近几年 在内蒙古 中部地 区找到 的 2 处 大型 -特大 型钼矿床 , 产 出规模 分 别达到 20 万吨和 200 万吨 。 钼矿化主要在太古宙变质岩及中生代石英斑岩 、正长斑岩和花岗斑岩体内呈浸染状 、网 脉状和脉状产出 , 并且构成筒状 、倒扣“碗状” 和囊状 矿体 。 两处 矿床无 论在产 出环境 和地质 特征上 , 还是 在矿物 种 属 、元素组合和热液蚀变方面 , 均与美国克莱麦克斯钼矿床和 黑龙江岔 路口钼矿床 较为相 似 , 是 中生代 构造-岩浆 活 动的产物 , 属古大陆碰撞造山后伸展环境 产出的斑岩型矿床 。 文章所提出的地壳 4 个演化阶段和 3 个成矿 期次的成 矿模式 对于提高大苏计和曹四夭钼矿床理论研 究水平 , 推动 低山丘 陵覆盖 区大型隐 伏钼矿 床的找 矿勘查 工作深 入 进行 , 均具有重要意义 。
本文是国家重点自然科学基金项目(41030421)和中国地质调查局地质调查项目(1212010911029)联合资助的成果 第一作者简介 聂凤军 , 男 , 1956 年生 , 研究员 , 博士生导师 , 从事金属矿床地球化学研究 。Email :nf jj @mx .cei .gov .cn 收稿日期 2012-05-12 ;改回日期 2012-06-10 。张绮玲编辑 。
2012 年 8 月 A ugust , 2012
文章编号 :0258-7106 (2012)04-0930-12
矿 床 地 质 M IN ERA L DEPOSIT S
Байду номын сангаас
第 31 卷 第 4 期 31 (4):930 ～ 940
内蒙古大苏计和曹四夭大型钼矿床的发现及意义
聂凤军1 , 刘翼飞1 , 赵宇安1 , 2 , 曹 毅1
关键词 地质学 ;斑岩钼矿床 ;地质意义 ;成矿 作用 ;大苏计 ;曹四夭 ;内蒙古中部 中图分类号 :618 .65 文献标志码 :A
Discovery of Dasuji and Caosiyao large-size Mo deposits in central Inner Mongolia and its geological significances
N IE FengJun1 , LI U YiFei1 , ZHAO YuA n1, 2and CAO Y i1
(1 M L R Key Laboratory of M etallogeny and M ineral Assessment , Institute of Mineral Resources, CAG S, Beijing 100037, China; 2 Shijiazhuang U niv ersity of Economics, Shijiazhuang 050031 , Hebei , China)
第 31 卷 第 4 期 聂凤军等 :内蒙古大苏计和曹四夭大型钼矿床的发现及意义 9 31
disseminated blocks .The molybdenum ore consists of py ri te , chalcopyrite , molybdenite , sphalerite , pyrrhot ite , scheelite, wolf ramite , K-feldspar , quartz , sericite , chlorite and epidote .As the most impo rtant economic molybdenum mineral , moly bdenite occurs in im pregnation , radiof lake , thin film , agg regated f lakes and veinlet forms in the veins .Re-Os iso topic data of f our molybdeni te separate samples f rom t he Dasuji deposit defined a correlation line corresponding t o an age of (222.5 ±3.2)Ma .Meanw hile , the moly bdenite samples f rom t he Caosiyao deposit has y ielded Re-Os model ages f rom 136 M a to 130 M a , wit h an average value of 134 M a .T he types of hy drothermal alterat ion observed bot h at Dasuji and Caosiy ao are mainly silicification , sericitization , Kfeldspathization , biotitization , fluoritization , chloritization , uralitization and carbo natizat ion .Of t hese alterations, silicification and K feldspathization are w ell developed , and have intimate relationship w ith moly bdenum mineralization .P reliminary st udies show that bot h the Dasuji and Caosiy ao deposit s w ere formed during t he M esozoic Indosinian and Yanshanian ex tensional tectonic movements that resulted in the intensive igneous activities .T he w ell-developed high K and SiO2 granitoid porphy ry stocks might have acted as the engines"of t he o re-f orming systems .Most of t he Mo w as derived from partial melting of the Precambrian co ntinental crust . T he ore-forming fluid w as dominated by magmatic water at the early met allogenic stage , and w as characterized by mixture w it h magmatic w ater as t he major source at the main met allogenic stage .The combined geochemical data , field geolog ical observations and pet rolog ical evidence indicate that both the Dasuji and Caosiy ao deposit s belong to the porphy ry ty pe medium-high temperature hy drothermal M o deposi t .T he Dasuji deposit is believed to be a product of t he Early Indosinian int raplate g ranitoid m agmatism w ithin t he Liangcheng uplift .Mo reover , the forming-processes of t he Caosiy ao deposit may be genetically related to the Yanshanian igneous activities in the same tecto nic unit .T he genetic model and mineral exploration criteria of t he Dasuji and Caosiy ao deposit s