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干沙鄂博稀土多金属矿床位于北祁连加里东褶皱带东段,成矿与干沙鄂博碱性斑岩体有关。干沙鄂博斑岩体为一小型岩株,地表出露面积约0.29km2,岩性以霓辉正长斑岩为主,其次为霓辉碱长石英正长斑岩。岩体具全岩面型蚀变矿化特征,与稀土矿化关系密切的围岩蚀变主要为萤石化、碳酸盐化和硅化。矿化范围大,矿带长约800m,延深大于420m,5个主矿体长70~260m,平均厚度12~29m。矿石品位较低,稀土氧化物平均品位1.39%~1.65%,矿石中伴生金属元素有Cu、Pb、Mo。矿石矿物以氟碳钙铈矿为主,其他金属矿物有黄铜矿、方铅矿、斑铜矿及辉钼矿等。含矿斑岩体为一套准铝质和碱性岩石,总体具有高硅低钛、富钾低钠的特点。岩石富集K、Rb、Sr、Ba等不相容元素,亏损Ta、Nb、Zr、Ti等高场强元素;轻重稀土分馏强烈,显著富集轻稀土,具Eu负异常。以上地球化学特征表明干沙鄂博碱性斑岩体的成因可能与华力西晚期后造山伸展环境下富集地幔的部分熔融有关,并经历了显著的分离结晶作用。通过与国内外典型稀土矿床的对比分析认为,干沙鄂博稀土矿矿床成因类型为碱性斑岩岩浆期后热液型多金属稀土矿床,与冕宁牦牛坪和美国加里诺斯稀土矿的矿床成因类似。
The dry-Ebo rare-earth polymetallic deposit is located in the eastern part of the Caledonian fold belt in the North Qilian, and the metallogenesis is related to the alkaline porphyry of dry Ebo. The dry sandbottom porphyry body is a small type of rock with an exposed area of about 0.29km2. The lithology is dominated by Ni-Hui-Zhengchang porphyry, followed by the Ni-Ni feldspar quartz-bearing porphyry. The rock mass is characterized by alteration mineralization of the whole rock surface. The alteration of the rock mass closely related to the rare earth mineralization is mainly fluorite, carbonate and silicification. Mineralization range, ore belt length of about 800m, the extension of more than 420m, five main ore body length 70 ~ 260m, the average thickness of 12 ~ 29m. The grade of ore is low, the average grade of rare earth oxides is 1.39% ~ 1.65%, and the associated metal elements in the ore are Cu, Pb and Mo. Ore minerals are mainly bastnasite, other metal minerals are chalcopyrite, galena, bornite and molybdenite. The ore-bearing porphyry is a set of quasi-aluminum and alkaline rock, which has the characteristics of high silicon, low titanium and potassium-rich and low-sodium. The rocks are enriched in incompatible elements such as K, Rb, Sr and Ba, and depleted in high field strength elements such as Ta, Nb, Zr and Ti. The fractional light and heavy fractions are intensely fractionated and enriched in light rare earths with Eu negative anomalies. The above geochemical characteristics indicate that the genesis of the dry-Ebo alkaline porphyry may be related to the partial melting of the enrichment mantle under the post-orogeny extensional environment in the late Variscan and have undergone significant separation and crystallization. According to the comparison with the typical rare earth deposits at home and abroad, it is concluded that the genetic type of the dry sand Obo rare earth deposits is the alkaline porphyry magmatic post-hydrothermal polymetallic rare earth deposits, which are related to the Mianning Maoniuping rare earth deposit The reason is similar.