The magnetite ore bodies of the Paleozoic Glubochenskoe iron deposit (315.7 Mt at ~ 30.15% Fe) are located in the northern part of the Valerianovka arc zone (“Turgai belt”) within the Transuralian Megazone, Russia. They occur in calcareous-volcaniclastic rocks, exhibit layered textures, and contain primary seafloor hematite ores. The sequence of mineral formation reflects the diagenetic to metamorphic evolution of the iron ores: (i) finely dispersed hematite-1; (ii) tabular hematite-2 crystals; (iii) pseudomorphic magnetite-1 after hematite-2; (iv) zoned magnetite-2 crystals with relict hematite-2 (or magnetite-1); (v) thin oscillatory zoned magnetite-3 crystals; and (vi) magnetite-4 porphyroblasts. A gangue assemblage of Fe-rich and Fe–Mg chlorite, illite, quartz, albite, carbonates, rutile, and apatite with rare monazite, xenotime, and zircon occurs in ore and calcareous-volcaniclastic layers. The gangue clasts (volcanic glass, Ca–Mg and Ti minerals, and altered volcanic rocks) are replaced by hematite and further by magnetite. Low siderite δ 13 C values from layered magnetite ores (− 8.0 to − 19.5‰ PDB) indicate the presence of primary organic matter in calcareous-volcaniclastic rocks. Siderite δ 18 O values (6.5 to 17.4‰ SMOW) are evidence of isotopic exchange between minerals and fluids during metamorphism. Negative δ 34 S values for pyrite (down to − 4.5‰) likely indicate derivation of sulfur from organic matter in clastic sedimentary rocks. LA-ICP-MS analysis of zoned magnetite demonstrates highly variable Si, Al, Mg, Na, K, Ca, Ti, Mn, Rb, Y, Zr, Sr, U, and P contents, related to inclusions of gangue minerals. Elevated homogenous V and Ga contents and low contents of Sc, Co, Ni, Ge, As, Mo, Sn, and W (average < 5 ppm) indicate their incorporation into the structure of magnetite. All element contents (except V and Ga) are significantly higher in the inner zone of magnetite (magnetite-1) compared to the outer zone of magnetite (magnetite-2). The calcareous-volcaniclastic material, which was altered during submarine weathering and leaching, is proposed to be a major source of iron to form oxides. Altogether, the paragenetic sequence, and the mineralogical and geochemical data suggest the Glubochenskoe deposit can be characterized as a volcanic-sedimentary type of banded iron formation.

中文翻译：

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俄罗斯图尔盖铁矿带 Glubochenskoe 矿床磁铁矿的形成：新的构造、矿物学、地球化学和同位素约束

古生代 Glubochenskoe 铁矿床的磁铁矿体（315.7 Mt at ~ 30.15% Fe）位于俄罗斯特兰乌利亚大带内 Valerianovka 弧带（“Turgai 带”）的北部。它们存在于钙质火山碎屑岩中，呈现层状结构，并含有原生海底赤铁矿。矿物形成的顺序反映了铁矿石的成岩到变质演化：(i) 细分散的赤铁矿-1；(ii) 片状赤铁矿-2 晶体；(iii) 赤铁矿-2 之后的假晶磁铁矿-1；(iv) 用残余赤铁矿 2（或磁铁矿 1）分区的磁铁矿 2 晶体；(v) 薄的振荡分区磁铁矿-3 晶体；(vi) 磁铁矿-4 卟啉细胞。富铁和铁镁绿泥石、伊利石、石英、钠长石、碳酸盐、金红石和磷灰石的脉石组合，以及稀有的独居石、磷钇矿、锆石存在于矿石层和钙质-火山碎屑层中。脉石碎屑（火山玻璃、Ca-Mg 和 Ti 矿物以及蚀变火山岩）被赤铁矿和磁铁矿取代。层状磁铁矿的低菱铁矿 δ 13 C 值（- 8.0 至 - 19.5‰ PDB）表明钙质火山碎屑岩中存在原生有机质。菱铁矿 δ 18 O 值（6.5 至 17.4‰ SMOW）是变质过程中矿物和流体之间同位素交换的证据。黄铁矿的负 δ 34 S 值（低至 - 4.5‰）可能表明硫来自碎屑沉积岩中的有机质。LA-ICP-MS 对分区磁铁矿的分析表明，与脉石矿物包裹体相关的 Si、Al、Mg、Na、K、Ca、Ti、Mn、Rb、Y、Zr、Sr、U 和 P 含量变化很大。均质的 V 和 Ga 含量升高，而 Sc、Co、Ni、Ge、As、Mo、Sn 和 W 含量较低（平均 < 5 ppm）表明它们已掺入到磁铁矿的结构中。与磁铁矿的外部区域 (magnetite-2) 相比，磁铁矿内部区域 (magnetite-1) 中的所有元素含量（V 和 Ga 除外）都显着更高。在海底风化和浸出过程中改变的钙质火山碎屑材料被认为是形成氧化物的铁的主要来源。总之，共生序列以及矿物学和地球化学数据表明 Glubochenskoe 矿床可以表征为火山沉积类型的带状铁地层。与磁铁矿的外部区域 (magnetite-2) 相比，磁铁矿内部区域 (magnetite-1) 中的所有元素含量（V 和 Ga 除外）都显着更高。在海底风化和浸出过程中改变的钙质火山碎屑材料被认为是形成氧化物的铁的主要来源。总之，共生序列以及矿物学和地球化学数据表明 Glubochenskoe 矿床可以表征为火山沉积类型的带状铁地层。与磁铁矿的外部区域 (magnetite-2) 相比，磁铁矿内部区域 (magnetite-1) 中的所有元素含量（V 和 Ga 除外）都显着更高。在海底风化和浸出过程中改变的钙质火山碎屑材料被认为是形成氧化物的铁的主要来源。总之，共生序列以及矿物学和地球化学数据表明 Glubochenskoe 矿床可以表征为火山沉积类型的带状铁地层。