| 内蒙古正蓝旗羊蹄子山-磨石山锐钛矿矿床地质与地球化学 |
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| 引用本文：ZHAO YiMing, LI DaXin, WU LiangShi, CHEN WenMing, FENG ChengYou, WANG PeiHua and GAO XueDong.2008.Geology and geochemistry of Yangtizishan-Moshishan anatase ore deposit in Zhenglanqi County, Inner Mongolia: A summary of exploration and investigation work[J].Mineral Deposits,27(4):425~448 |
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| 基金项目:国家自然科学基金(40773038)；内蒙古自治区地勘项目(05-1-TK01)；中央级公益性科研院所基本业务费资助项目(K0714_1, K0714_3) |
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| 中文摘要:锐钛矿及其同质异象金红石是钛矿资源中最具经济意义的，也是中国当前的紧缺矿种之一。前人把羊蹄子山矿床确定为铁矿床(点)，通过近几年的研究和勘查，笔者认为这是一个以锐钛矿为主的沉积变质型矿床，是钛矿床的一个新的类型。矿体产于中元古代〔 (1 751±8 )Ma〕片岩、变质石英(粉)砂岩和斜长角闪岩中，呈似层状、透镜状产出。富矿石具有细纹状构造，表现为以石英为主(含浸染状锐钛矿)和锐钛矿条纹互层。矿石矿物主要为锐钛矿，次有金红石和钛铁矿(±赤铁矿)，脉石矿物以石英为主，含一定量的直闪石和黑云母(±石榴子石)。锐钛矿、金红石和钛铁矿的粒度很细，粒径为0.01～0.1 mm。富矿TiO2含量为3.14%～15.46%，平均6.91%，而贫矿的TiO2含量为1.2%～2.97%，平均1.76%。矿石含较高的TFe和V。电子探针分析表明锐钛矿和金红石的Nb和Cr含量较低，说明矿物的源区来自变质基性岩。钛铁矿微量元素的特点是富锰贫镁，和岩浆型钒钛磁铁矿中钛铁矿的微量元素正好相反。围岩斜长角闪岩恢复其原岩大致相当于玄武岩、苦橄玄武岩等。岩石化学揭示其生成构造环境为岛弧或岛弧和洋脊的过渡带。硅同位素组成结果显示，不同锐钛矿矿石、石英岩和片岩等的δ30Si值为0.1‰～-0.9‰，与海底热液喷气沉积矿床的数据相似。所有上述矿床的地质和地球化学特征表明，锐钛矿矿石和斜长角闪岩都是海底基性火山活动的产物，矿石具有化学沉积特征，而后来遭到中级(偏低)区域变质作用(1 158 Ma)的影响，金红石主要形成于区域变质作用。该矿床在燕山晚期〔（118±3）Ma〕由于花岗岩的侵位又局部受到热液改造。 |
| 中文关键词:地质学 地球化学 锐钛矿矿床 羊蹄子山-磨石山 正蓝旗 内蒙古 |
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| Geology and geochemistry of Yangtizishan-Moshishan anatase ore deposit in Zhenglanqi County, Inner Mongolia: A summary of exploration and investigation work |
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| Abstract:Anatase and its isomeric mineral-rutile have the most prominent economic significance among titanium mineral resources, and constitute one of the badly needed mineral resources currently in China. The Yangtizishan-Moshishan anatase ore deposit was formerly referred to as an iron deposit. Based on the authors' investigation and exploration in recent years, it is held that it is actually a metamorphosed sedimentary anatase-predominated ore deposit belonging to a new genetic type. The ore bodies occur in the stratoid and lenticular forms in Middle Proterozoic (1 751±8 Ma) schist, metasandstone (metasiltstone), and amphibolite. The rich ores have perthitic structure comprising chiefly interbedded quartz perthite (with disseminated anatase, rutile) and anatase perthite. The ore minerals are mainly anatase, subordinately rutile and ilmenite (±hematite), while the nonmetallic minerals are chiefly quartz with a certain amount of anthophyllite and biotite (±garnet). The grain sizes of anatase, rutile and ilmenite are 0.01～0.1 mm. The rich ores contain 3.14%～15.46% TiO2, averaging 6.91%, while the low grade ores have TiO2 content about 1.2%～2.97%, averaging 1.76%. The ores have relatively high TFe and V contents. Trace elements in anatase and rutile such as Nb and Cr were measured by electron microprobe. According to their relatively low Nb and Cr contents, the provenance of anatase and rutile must have come from mafic rocks. Trace elements of the associated ilmenite show relatively high MnO and low MgO contents, just opposite to those of ilmenite in V_Ti_magnetite ores of magmatic origin. The recovering work reveals that the initial rocks of amphibolite wall rocks should be basalt, picrite-basalt etc. Petrochemical data suggest that the tectonic setting of these rocks belongs to island arc or the transitional belt between island arc and oceanic ridge. Investigation of silicon isotope compositions shows that δ30Si values of different anatase ores, quartzite and schist in this deposit are 0.1‰～-0.9‰, similar to those of marine hydrothermal exhalative sedimentary deposits. All these geological and geochemical characteristics of the ore deposit suggest that the anatase ores and amphibolite are products of oceanic basic volcanism. The ores had chemical precipitation features, but were later subjected to regional metamorphism (1 158 Ma) of the intermediate (or somewhat lower) degree. Rutile was formed mainly in the process of this metamorphism. The ore belt locally underwent hydrothermal reformation during the emplacement of Late Yanshanian granite (118±3 Ma). |
| keywords:geology, geochemistry, anatase ore deposit, Yangtizishan-Moshishan, Zhenglanqi County, Inner Mongolia |
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