In situ U–Pb and Nd–Hf–(Sr) isotopic investigations of zirconolite and calzirtite
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Carbonatite
Zirconolite
Microprobe
Trace element
Carbonatite
Petrogenesis
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Carbonatites 是通常与象 REE， Cu，和 P 那样的经济地珍贵的物质的累积有关。在到联系硅酸盐岩石的 carbonatites 和他们的关系的起源上的争论是进行中的大约 45 年了。全球，岩石表示特性地比沉积碳酸盐岩石在 Ba， Sr 和 REE 显示更多的 geochemical 丰富。然而，因为第二等的矿物质效果， carbonatites geochemical 特征被争论。从在在中国的 Qinling， Panxi 区域，和 Bayan Obo 的 carbonatites 的形成岩石的碳酸盐显示出从 LREE 丰富到扁平的模式的 REE 分发模式。他们被超过 10 比第二等的碳酸盐的高预定的一个 Sr 内容描绘。从 Bayan Obo H8 白云石云石的纹理粗糙、有细密纹理的白云石也显示出类似的高 Sr 丰富，显示他们具有火的起源。在中国 carbonatites 的一些碳酸盐显示出 REE (特别 HREE ) 整个岩石的类似于那些的内容和分布模式。这些恼人的 carbonatites 显示相对 high-Si 降低在磅和红外之间的铂组元素和更强壮的分别挤出的 carbonatite。这显示很恼人的 carbonatites 可以是碳酸盐堆积。在 Panxi 区域的 Maoniuping 和 Daluxiang 是大 REE 沉积物。热水的荧石矿石静脉发生在 carbonatite 身体外面并且是在 wallrock 的 emplaced 正长岩。在 Maoniuping 的荧石有类似于 carbonatite 的 Sr 和 Nd 同位素。Daluxiang 荧石在 Maoniuping 显示出与那些不同的 Sr 和 REE 作文。差别被 carbonatites 和形成岩石的碳酸盐反映，显示那个 REE 矿化作用与 carbonatites 有关。碳酸盐矿物质的 cumulate 进程从 LREE 由于为在碳酸盐和 carbonatite 之间的 REE 的系数融化的低分区和增加在 volatiles 和 LREE 使 fractionated 液体富有到 HREE。导出 carbonatite 的液体与 wallrock 交往了形成 REE 矿石静脉。发生在 Bayan Obo orebodies 附近的 carbonatite 女同性恋的数量可以支持一样的矿化作用模型，即液体从 carbonatite 女同性恋演变，这与 H8 白云石大理石反
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The Mt Vulture carbonatites are the only carbonatite occurrence in the southern Apennines. We present new trace element data for these rocks in order to evaluate the factors influencing rare earth element (REE) and other trace element fractionations and their REE grade. This study focuses on massive hyalo-alvikites from two lava flows and one dike, which have different relative abundances of silicate and carbonate (i.e. Si/Ca). These differences are also evident from CaO/(CaO + MgO + FeO(T) + MnO) and Sr/Ba ratios. The REE grade of the Mt Vulture carbonatites is very similar to that of the global average for calcio-carbonatites. R-mode factor analysis shows that most of the trace element variance reflects the relative roles of carbonate and silicate minerals in influencing trace element distributions. Silicates largely control heavy rare earth element (HREE), transition metal, Zr, and Th abundances, whereas carbonate minerals control light rare earth element (LREE), Ba, and Pb abundances. In addition, apatite influences LREE concentrations. Increasing silica contents are accompanied by decreases in (La/Yb)N and (La/Sm)N ratios and less marked LREE enrichment. In contrast, higher carbonate contents are associated with increases in (La/Yb)N and (La/Sm)N. The Si/Ca ratio has little influence on Eu anomalies and middle rare earth element (MREE) to HREE fractionations. Apatite has a negligible effect on inter-REE fractionations amongst the carbonatites.
Carbonatite
Trace element
Rare-earth element
Silicate minerals
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There are four chronological groups of carbonatite complexes in Ontario and Quebec. These are about 125 m.y., 565 m.y., 1075 m.y., and 1700 m.y., with a possible fifth at 1560 m.y. The recently proposed St. Lawrence Rift System is not considered to be a very likely control of carbonatite emplacement unless it includes a widespread system of branch faults. The coincidence of carbonatite complexes with the "Kapuskasing High" is striking and probably puts a minimum age of 1750 m.y, on the feature. Niobium is found in carbonatites of each age group.
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Feature (linguistics)
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Carbonatite
Trace element
Fractional crystallization (geology)
Melt inclusions
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Carbonatite
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Carbonatites contain some of the highest concentrations of REE in the Earth's crust. Levels of hundreds of ppm REE are characteristic but concentrations can exceed 10 wt.%. Such rare-earth rich carbonatites are common minor components of carbonatite complexes. They are often ferrocarbonatites and, even if only minor components of a carbonatite complex, can still host the majority of the REE. When, more rarely, the rare–earth rich carbonatites occur in larger quantities they are of economic importance. Rare earth minerals form in the ...
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By analysis of publisked and authors data the conclusion was made that primary chemical composition of carbonatites was predo minautly alkali-carbonate similar to ones of carbonatites and tuffs of Oldoinyo Lengai volcano (with high content of Na2CO3, K2CO3, CaCO3 and subordinately MgCO3, FeCO3). Such carbonatite melts reacted on country rocks (more often granitoids) and caused a fenitization of them while residual components СаСО3, MgCO3 and FeCO3 crystallizel as well known types of carbonatites (calcitic, dolomitic, ankeritic). Intrusive carbonatite complexes consist of such ultrabasic and alkaline racks as olivinites (rarely dunites), jacupiragitespyroxenites, melilitites, ijolites-melteigites, nepheline and alkaline syenites, phoscorites and carbonatites wich can be present in different combination (completely alone or two types of mentioned rocks). Silicate alkaline melts (of melilitite, melanephelinite types) related to carbonatite magmas were normatively and modally unsaturated with SiO2 and feldsparless. Basalt melts are not able to generate carbonatites. Carbonatites different from visually similar calciphyres and marbles by geochemical peculiarities and ore potential.
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Ultramafic rock
Nepheline syenite
Nepheline
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