| 广西钦州_防城地区次生氧化锰矿床矿物学和地球化学研究及矿床成因意义 |
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| 引用本文：.2007.Mineralogy and geochemistry of supergene manganese ore deposits in Qinzhou_Fangcheng area, southern Guangxi, with implications for ore genesis [J].Mineral Deposits,26(5):527~540 |
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| 基金项目:国家自然科学基金（40202010）和霍英东教育基金会高等学校青年教师基金（No. 101017） |
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| 中文摘要:钦州_防城锰矿带是中国次生氧化锰矿的重要产地之一，其含锰岩系为上泥盆统榴江组含锰硅质岩。锰矿床主要赋存在以腐岩带为主的风化壳中，矿石的主要矿物为软锰矿、锰钡矿、隐钾锰矿、锂硬锰矿、钙锰矿等，与之伴生的其他表生矿物有赤铁矿、针铁矿、石英、高岭石和其他粘土矿物。矿石多呈葡萄状、块状、网脉状构造。与原生含锰硅质岩相比，次生氧化锰矿矿石的品位明显提高，Mn含量平均达到42.6 %。矿石化学分析和单矿物电子探针成分分析表明，氧化锰矿石中还普遍出现Co、Ni、Cu、Zn等元素的富集，其平均含量分别为0.05 %（最高0.40 %）、0.09 %（最高0.53 %）、0.08%（最高0.53%）和1 %（最高2.2%）；它们主要以类质同象和吸附的形式赋存在锂硬锰矿及隐钾锰矿中。氧化锰矿石和锰氧化物的Mn/Fe比值均较高，一般大于6～10，说明该区化学风化强烈，铁、锰分离显著，有利于形成高品位的优质锰矿。有害杂质元素P主要存在于针铁矿等铁的氧化物中。氧化锰矿的形成和空间分布受气候、构造、含锰岩系及地形地貌等多种因素的影响和控制。 |
| 中文关键词:地质学 氧化锰矿床 次生富集 风化壳 钦州_防城 广西 |
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| Mineralogy and geochemistry of supergene manganese ore deposits in Qinzhou_Fangcheng area, southern Guangxi, with implications for ore genesis |
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| Abstract:The Qinzhou_Fangcheng (Qin_Fang) manganese belt in southern Guangxi is an important Mn_producing area in China. Supergene Mn enrichment is related to the weathering of the Mn_bearing chert beds in the Upper Devonian Liujiang Formation, and Mn_oxide ores are hosted mainly in the saprolite zone of weathering profiles. The common Mn_oxide minerals include pyrolusite, hollandite, cryptomelane, lithiophorite and todorokite, intergrown variably with other supergene minerals such as hematite, goethite, quartz and clay minerals. Mn_oxide ores are characterized by botryoidal, banded or massive structures, indica_ting that their formation is attributed mainly to the direct precipitation of tetravalent manganese from weathering solutions. Compared with the protore beds, the supergene Mn_oxide ores have much higher grade, with an average of 426 % Mn, and contain significantly elevated contents of Co, Ni, Cu and Zn, up to 0.40 %, 0.53 %, 0.53 % and 0.22 %, respectively. The enrichment of these metals is mainly related to lithiophorite and partly to cryptomelane, occurring as ionic replacements in the mineral structures or adsorption by the host minerals. Chemical analyses of bulk ores and electron microprobe analyses of monomineralic grains reveal high Mn/Fe ratio (generally >6～10), indicating intensive weathering and efficient chemical separation between these elements, a condition favorable for the formation of high_grade and high_quality manganese ores. In comparison with Mn_oxide minerals, the iron oxides such as goethite and hematite have much higher P contents. Such a preferential host of P provides a useful guide for the separation of manganese ores. The present data, combined with a geological analysis, suggest that the formation and distribution of supergene manganese deposits in the Qin_Fang area are controlled by a combination of lithological, climatic, tectonic, and geomorphological factors. |
| keywords:geology, supergene manganese enrichment, Mn_oxides, Qinzhou_Fangcheng, Guangxi |
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