【作者】 蓝翔华；

【导师】 杨晓勇； 杨忠堂；

【作者基本信息】 中国科学技术大学 ， 地球化学， 2011， 硕士

【摘要】 位于南秦岭磷-锰成矿带中东段的后沟-大坪山一带,近年来在下寒武统塔南坡组地层中发现三条锰磷矿化带,具有重要的锰矿成矿远景。锰矿体均赋存于下寒武统塔南坡组含碳泥质岩-碳酸盐岩建造内,属海相沉积变质改造类型锰矿床。本文在对后沟—大坪山锰矿地质特征总结分析基础上,系统采集了样品,开展室内显微镜观察,X-射线粉晶分析和常量与微量元素和稀土元素地球化学系统测试及区域化探数据处理,以此探讨锰矿成因及区内优质锰矿的成矿条件和成矿控制作用,提出区域优质锰矿的找矿标志。主要认识如下:（1）通过大量区内样品的MnO/TiO₂比值、Al/（Al+Fe+Mn）比值、U/Th比值,以及Na（Wt%）对Mg（Wt%）判别图、Si（Wt%）对Al（Wt%）判别图、Al-Fe-Mn判别图、F2-F1判别函数图、lgw（U）-lgw（Th）关系图等综合分析,我们认为勉略成矿带后沟-大坪山锰矿床富集锰、磷的物源具有远洋热液沉积的特征,其围岩主要形成于边缘海沉积环境,沉积物质以陆源为主。（2）样品的微量元素蛛网图表明,含锰矿石样品Rb、K、Pb等元素亏损。Ba、U、Sr和稀土元素等元素丰度较高,远大于陆壳值。围岩样品Rb、K、Pb等元素亏损。Ba、Th、U、Zr、Hf、Ti和稀土元素富集,远大于陆壳值。本文岩石样品ΣREE含量从24.260ppm～602.741ppm,平均为192.022ppm。轻稀土LREE富集,除了2个样品的LREE/HREE小于1之外,其余样品的LREE/HREE均大于1,从0.413～18.269,平均7.18。在北美页岩标准化的稀土元素配分模式曲线图中,含锰矿石、围岩都表现为基本平滑型。大多数样品表现出了强烈的Dy正异常。（3）本区样品V/（V+Ni）为0.45～0.99,平均0.73,说明本区样品于水体分层不强烈,水体深度有一定的变化,还原性时强时弱的厌氧环境下形成。本区样品的δU值为1.06².0,平均1.46,表现为缺氧沉积环境。推测含锰岩系形成于水体有一定分层的缺氧（还原）沉积环境。样品的δU值为1.06².0,平均1.46,也指示表现为缺氧沉积环境。可见,含锰岩系形成于水体有一定分层的缺氧（还原）沉积环境。（4）区内优质锰的成矿受磷锰分离沉积成矿和铁锰分异控制,具有下磷上锰分层成矿特点;含锰灰岩（白云质灰岩）和含黄铁炭质片岩为本区的锰矿找矿标志。更多还原

【Abstract】 The Hougou-Dapingshan three manganese (Mn) and phosphor (P) metallogenic belts, located in the middle east segment of the South Qinling Mn- P metallogenic zone, have been founded recently. The regional 3 high quality Mn orebodies are associated with carbonaceous argillaceous rock-carbonatite formation of Tananpo Formation ( Lower Cambrain), belonging to Mn deposit of sea facies sedimentary metamorphic/ reconstructed type.On survey of geology and ore deposits, the Hougou-Dapingshan manganese ore district, systematic sampling, microscopic observation, XRD and geochemical analyses have been conducted. Results were used to constrain formation of manganese deposits and the metallogenic forming condition. The controlling processing of high quality Mn ores are studied and presented, the prospecting indications for manganese deposits have been proposed and constrained. The conlcusions are as follow:1. The values of MnO/TiO2, Al/(Al+Fe+Mn), U/Th together with the discriminant diagrams of Na (Wt%) vs Mg(Wt%), Si(Wt%) vs Al(Wt%), Al-Fe-Mn, F2 vs F1 and lgw(U) vs lgw(Th) comprehensive analysis show that the Mn and P bearing ores were formed in the ocean hydrothermal sedimentary environment. Meanwhile the wall rocks were formed in a marginal marine sedimentary environment, sediments were maily derived from continent. The carbonaceous rocks had a close relationship with the Mn/P bearing ore formation.2. The trace element spider diagrams show that Mn bearing ores and wall rocks are depletion in Rb, K, Pb , and enrichments in Ba, U, Sr and the REE, these enrichments are more than average continental values. TheΣREE of samples varied from 24.26 ppm to 602.74 ppm with an average of 192.02 ppm. The LREE is much enrichments compared with thos of HREE. Apart from two samples, the value of LREE/HREE is greater than 1, varying from 0.41 to 18.27 with an average of 7.18. In the NASC Normalized REE patterns, both Mn bearing ores and wall rocks show nearly flat pattern distributions. Most samples show strong positive anomalies in Dy.3. The values of V/(V+Ni) vary from 0.45 to 0.99 with an average of 0.73, indicating that samples were formed in the anaerobic environment with features of ordinary stratified water bodies and a changed water depth and reduction. The values ofδU vary from 1.06 to 2.0 with an average of 1.46, indicating a anoxic sedimentary environment. It is inferred that Mn bearing rocks were formed in anoxic(reduction) sedimentary environment with stratified water bodies.4. The Mn metallogenic process has evident feature of basin-controlling, schistosity-controlling and single lithology. High quality Mn ores were controlled by Mn and P sediments and Mn metallogenic seam existing in the P metallogenic seam. Manganese limestone (including dolomite limestone) and pyritic charry schist are proposed as prospecting indications in this region.更多还原