Abstract This study is aimed at characterizing the distribution and speciation of the rare earth elements and yttrium (REE + Y) in ooidal ironstones from the Kamysh-Burun deposit (Kerch Peninsula), with implications for the depositional environments and contributions of different REE + Y carriers to the ore budget. The Lower Pliocene ooidal ironstone sequence of the so-called Kerch ores, up to 15 m thick, occupies an area of 28 km2. The ore sequence lies between Miocene – Lower Pliocene shell limestones and Upper Pliocene – Pleistocene sandy and clayey sediments and consists of horizontal ooidal ironstone beds composed mainly of goethite and X-ray amorphous Fe3+-(oxy)hydroxides intercalated with siderite and/or rhodochrosite beds. Iron is a main component in ooidal ironstones (50.03–66.19 wt% Fe2O3 and ≤1.61 wt% FeO), as well as in fresh carbonate ores (~34 wt% FeO and ≤14.70 wt% Fe2O3). The Kerch ores contain up to 4.59 wt% P2O5 and show significant positive correlation between P and Fe (r = 0.75). The bulk ore samples and their coarse (1–10 mm) fractions are goethite-dominated and have similar phase, major- and trace-element, and REE compositions. The fine ( La ≈ Nd ≈ Ca > Pr > Sm. The ΣREE content in fresh carbonate ores is below that in PAAS (Xav = 103 ppm), but approaches the latter in oxidized crusts (Xav = 178 ppm). The Kerch ironstones also contain REE-poor early-diagenetic Fe2+ phosphate vivianite (ΣREE Xav = 0.93 ppm) and Ca-Fe2+ phosphate anapaite (ΣREE Xav = 6.95 ppm) with typical seawater REE + Y distributions. The ooidal ironstones show MREE-enriched patterns with distinct negative Y* anomalies, which reveals Fe3+-(oxy)hydroxides as chief carriers of adsorbed REE (mainly MREE). The Kerch ironstones accumulated REE progressively due to hysteretic dissolution and precipitation of Fe3+-(oxy)hydroxides in oscillating redox conditions. The diagenetic source of REE stored in ooidal goethite ironstones was inferred from the PAAS-normalized values: CeN/CeN* vs Nd and CeN/CeN* vs YN/HoN discrimination diagrams. In general, the REE + Y budget of the Kerch ooidal ironstones mainly formed during early diagenesis and scavenging from pore water, with a minor contribution of siliciclastic inputs, in the absence of hydrothermalism.

中文翻译：

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高磷鲕粒铁矿石中稀土元素的地球化学和矿物学：以 Kamysh-Burun 矿床（亚速-黑海铁矿区）为例

摘要 本研究旨在表征 Kamysh-Burun 矿床（刻赤半岛）鲕粒铁矿中稀土元素和钇 (REE + Y) 的分布和形态，对不同 REE + Y 的沉积环境和贡献有影响。运营商的矿石预算。所谓的刻赤矿石的下上新世卵形铁岩层序，厚达 15 m，占地 28 平方公里。矿石层序位于中新世 – 下上新世壳灰岩和上新世 – 更新世砂质和粘土沉积物之间，由水平鲕粒铁岩层组成，主要由针铁矿和 X 射线无定形 Fe3+-（氧）氢氧化物组成，中间夹有菱铁矿和/或菱锰矿床. 铁是鲕形铁矿石的主要成分（50.03–66.19 wt% Fe2O3 和≤1.61 wt% FeO），以及新鲜碳酸盐矿石（~34 wt% FeO 和≤14.70 wt% Fe2O3）。Kerch 矿石含有高达 4.59 wt% 的 P2O5，并且 P 和 Fe 之间显示出显着的正相关（r = 0.75）。大块矿石样品及其粗（1-10 毫米）部分以针铁矿为主，具有相似的相、主要和微量元素以及 REE 组成。细粒 (La ≈ Nd ≈ Ca > Pr > Sm。新鲜碳酸盐矿石中的 ΣREE 含量低于 PAAS (Xav = 103 ppm)，但在氧化壳中接近后者 (Xav = 178 ppm)。刻赤铁矿也含有贫稀土的早成岩 Fe2+ 磷酸盐紫云母 (ΣREE Xav = 0.93 ppm) 和 Ca-Fe2+ 磷酸盐磷灰石 (ΣREE Xav = 6.95 ppm)，具有典型的海水 REE + Y 分布。卵形铁矿石显示出富含 MREE 的模式，具有明显的负 Y *异常，这表明 Fe3+-（氧）氢氧化物是吸附 REE（主要是 MREE）的主要载体。由于 Fe3+-（氧）氢氧化物在振荡氧化还原条件下的滞后溶解和沉淀，刻赤铁矿石逐渐积累了 REE。从 PAAS 归一化值推断出储存在卵形针铁矿中的 REE 的成岩来源：CeN/CeN* 与 Nd 和 CeN/CeN* 与 YN/HoN 鉴别图。总的来说，刻赤鲕粒铁岩的 REE + Y 收支主要形成于早期成岩作用和从孔隙水中清除，在没有热液作用的情况下，硅质碎屑输入的贡献很小。从 PAAS 归一化值推断出储存在卵形针铁矿中的 REE 的成岩来源：CeN/CeN* 与 Nd 和 CeN/CeN* 与 YN/HoN 鉴别图。总的来说，刻赤鲕粒铁岩的 REE + Y 收支主要形成于早期成岩作用和从孔隙水中清除，在没有热液作用的情况下，硅质碎屑输入的贡献很小。从 PAAS 归一化值推断出储存在卵形针铁矿中的 REE 的成岩来源：CeN/CeN* 与 Nd 和 CeN/CeN* 与 YN/HoN 鉴别图。总的来说，刻赤鲕粒铁岩的 REE + Y 收支主要形成于早期成岩作用和从孔隙水中清除，在没有热液作用的情况下，硅质碎屑输入的贡献很小。