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首页> 外文期刊>Russian Geology and Geophysics >Main minerals of abnormally high-grade ores of the Tomtor deposit (Arctic Siberia)
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Main minerals of abnormally high-grade ores of the Tomtor deposit (Arctic Siberia)

机译：Tomtor矿床（北极西伯利亚）的异常高档矿石的主要矿物

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The Tomtor massif of Paleozoic ultramafic alkaline rocks and carbonatites is located in the northern part of the Sakha Republic (Yakutia). The massif (its total area is similar to 250 km(2)) is similar to 20 km in diameter, with a rounded shape and a concentrically zoned structure. The core of the massif consists of carbonatites surrounded by a discontinuous ring of ultramafic rocks and foidolites. The outer part is composed of alkali and nepheline syenites. All rocks are weathered and covered with eluvium, which is the thickest after carbonatites enriched in phosphates and REE. The weathering profile consists of four layers, from the top: kaolinite-crandallite, siderite, goethite, and francolite. The highest-grade ores are observed in the bedded deposit which fills depressions in "sagging" eluvium. The ores are laminated and cryptogranular, with high Nb, Y, Sc, and REE contents (on average, 4.5% Nb2O5, 7-10% REE2O3, 0.75% Y2O3, and 0.06% Sc2O3). The highest-grade ores are natural Nb and REE concentrates. The total REE content in some layers is >10%. The morphologic features of the highest-grade phosphate ores from the northern part of the Burannyi site were studied. The ore-forming minerals belong to the pyrochlore group, crandallite group (goyazite), and monazite-Ce. The pyrochlore group minerals occur mainly as crystals that were completely replaced by barium-strontium pyrochlore and/or plumbopyrochlore but retained the original faces; also, they occur as numerous conchoidal fragments. The grains of the pyrochlore group minerals sometimes have a zonal structure, with an unaltered pyrochlore core and a reaction rim. Goyazite occurs predominantly as colloform grains. According to SEM and TEM data, monazite occurs in the ores as similar to 50 nm particles, which cover the outer part of halloysite tubes (800-3000 nm long and 300 nm in diameter) as a dense layer and make up peculiar biomorphic aggregates. The mineralogical data, the occurrence of biomorphic aggregates, and the close association of organic remains with ore minerals suggest that the high-grade ores of the Tomtor deposit, including the Burannyi site, resulted from a hydrothermal-sedimentary process with a presumably important role of bioaccumulation of REE phosphates. (C) 2015, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
机译：古生代超镁铁质碱性岩石和碳酸盐岩的Tomtor地块位于萨哈共和国（雅库特）的北部。地块（其总面积类似于250 km（2））的直径类似于20 km，具有圆形形状和同心分区的结构。地块的核心由碳酸盐岩组成，周围是不连续的超镁铁质岩石和泡沫岩环。外部由碱和霞石正长岩组成。所有岩石均经过风化处理，并覆盖有Eluvium，这是富含磷酸盐和REE的碳酸盐岩之后最厚的。从顶部开始，风化剖面由四层组成：高岭石-方钠石，菱铁矿，针铁矿和方沸石。在层状矿床中观察到了最高品位的矿石，该矿床填补了“下陷”斜坡中的凹陷。矿石是层状和隐粒状的，具有高Nb，Y，Sc和REE含量（平均为4.5％Nb2O5、7-10％REE2O3、0.75％Y2O3和0.06％Sc2O3）。最高品位的矿石是天然Nb和REE精矿。某些层中的总REE含量> 10％。研究了来自布兰尼地区北部最高品位的磷酸盐矿的形态特征。形成矿石的矿物属于烧绿石族，方铅石族（方铁石）和独居石-铈。烧绿石族矿物主要以晶体形式存在，被钡锶烧绿石和/或铅烧绿石完全替代，但保留了原始面。而且，它们以许多贝壳状碎片的形式出现。烧绿石族矿物的晶粒有时具有带状结构，烧绿石核心没有改变，反应边缘也没有变化。芒硝主要以胶状晶粒出现。根据SEM和TEM数据，独居石在矿石中以类似于50 nm颗粒的形式存在，它们以密集层覆盖埃洛石管的外部（长800-3000 nm，直径为300 nm），并构成奇特的生物形态聚集体。矿物学数据，生物形态聚集体的发生以及有机残余物与矿石矿物的紧密联系表明，Tomtor矿床（包括Burannyi矿床）的高品位矿石是由水热沉积过程产生的，推测该过程具有重要的作用。 REE磷酸盐的生物蓄积。 （C）2015，V.S. Sobolev IGM，RAS的西伯利亚分公司。由Elsevier B.V.发布。保留所有权利。

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