Carbonatites and carbothermalites: A revised classification
2022年11月15日 · Typically, carbothermalites are fine-to-very fine grained rocks with complex textures and mineralogy (Fig. 2) which commonly renders them unsuitable for optical petrographic study. Methods such as BSE-imagery coupled with qualitative and quantitative X-ray EDS or WDS spectrometry are essential in defining their mineralogy and allowing them to ...
High-Ti magnetite in some fine-grained carbonatites and the …
A fine-grained carbonatite from Zambia contains magnetites with an extraordinary array of compositions (from 18–1% TiO 2, 10–2% Al 2 O 3, and 16–4% MgO) outranging previously-reported examples. Zoning trends are from high TiO 2 to high Al 2 O 3 and MgO. No signs of exsolution are seen.
Thallium Isotopes Reveal Brine Activity During Carbonatite …
2021年1月27日 · Ankerite-barite carbonatite: The majority of the samples in this study are fine-to medium-grained ferromagnesian carbonatites consisting primarily of ankerite and barite (Figures 2d and 2f). They contain abundant fragments of sövite (RT-10K-12) and glimmerite (RT-11K-6).
Petrogenesis and rare earth element mineralization of the Elk …
2022年7月1日 · Vugs and cavities within the AD carbonatite are partially filled with fine-grained REE minerals including parisite, synchysite, bastnäsite, and monazite as well as quartz and iron oxide, with occasional fluorite and dolomite (Fig. 5 a and b). Examples of skeletal remains of apatite have also been observed.
Chemical compositions of carbonate minerals from Bayan Obo, …
2004年1月1日 · Carbonate rocks at the Bayan Obo giant rare earth element (REE)–Nb–Fe ore deposit, Inner Mongolia, China are divided into four categories: sedimentary limestone and dolostone (H8 s), deformed mineralized coarse-grained dolomite marble (H8 c) and fine-grained dolomite marble (H8 f), and carbonatite dikes (D), based on their texture, mineral ...
Carbonatites: related ore deposits, resources, footprint, and ...
2018年10月9日 · Carbonatites are defined by the International Union of Geological Sciences (IUGS) as igneous rocks containing more than 50% modal primary carbonates (Le Maitre 2002). Depending on the predominant carbonate mineral, a carbonatite is referred to as a ‘calcite carbonatite’, ‘dolomite carbonatite’ (
The origin and composition of carbonatite-derived carbonate …
2020年8月27日 · Ovoid magmatic fluorapatite grains (i) are fragmented and overgrown by epitactic carbonate-bearing fluorapatite (ii) which is enveloped in massive, fine-grained carbonate-bearing fluorapatite (iii). These rocks, when subsequently fragmented, show additional late euhedral (iv) and colloform (v) generations of apatite occurring along fractures ...
The Bayan Obo (China) giant REE accumulation ... - GeoScienceWorld
2019年10月15日 · In the Bayan Obo deposit, REE ores are hosted in dolomites (including coarse-grained and fine-grained varieties), and many carbonatite dikes (ferroan, magnesian, and calcic) have been identified. All of the dolomites and carbonatite dikes appear to be broadly coeval and possess similar geochemical characteristics.
Calcite and dolomite in intrusive carbonatites. I. Textural
2015年6月27日 · Dolomitization of calcite (Fig. 10a) is the best known process of that kind and can be recognized by the presence of relict calcite grains in a network of fine-grained dolomite veinlets, replacement of associated silicate and oxide minerals (e.g., olivine by serpentine; phlogopite by tetra-ferriphlogopite or chlorite; clinopyroxene by alkali ...
Rare earth element mobility in and around carbonatites controlled …
Natural burbankite is a rare and ephemeral mineral, often pseudomorphed by fine-grained assemblages of REE fluorcarbonates, monazite, baryte, strontianite, and rock-forming carbonates (6, 27, 29–35), and occasionally described in fluid inclusions (15, 22, 36). Our experiments also contain extensive REE hosted in the Na-carbonates bonshtedtite ...