3D mineralogical mapping of the Kovdor phoscorite-carbonatite complex (Russia)
3D mineralogical mapping of the Kovdor phoscorite-carbonatite complex (Russia)
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DOI：
10.1007/s00126-015-0594-z
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发表时间：
2016-01-01
影响因子：
4.8
通讯作者：
Ivanyuk, Gregory Yu.
中科院分区：
文献类型：
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作者：
Mikhailova, Julia A.;Kalashnikov, Andrey O.;Ivanyuk, Gregory Yu.
Kovdor磷铁矿-碳酸盐岩管中的Kovdor斜锆石-磷灰石-磁铁矿存款位于带状碱-超基性岩Kovdor侵入体的西部（Fennoscandinavian地盾的西北部;俄罗斯摩尔曼斯克地区）。我们描述了主要的侵入岩和交代岩管及其周围地区使用一个新的分类磷铁矿碳酸岩系列岩石，与IUGS的建议。管道的逐渐分带对应于矿物结晶的顺序（镁橄榄石-羟基磷灰石-磁铁矿-方解石）。晶体形态，粒度，特征包裹体，和组成的岩石和副矿物显示相同的空间分带模式，因为这样的三种矿物的经济利益，即磁铁矿，羟基磷灰石，斜锆石。羟基磷灰石中Sr、稀土元素（REEs）和Ba的含量从早期磷灰石-镁橄榄石磷块岩（管道边缘）通过无碳酸盐、富磁铁矿的磷块岩到富碳酸盐的磷块岩和磷块岩相关的碳酸盐岩（内部）逐渐增加，而Si、Fe和Mg的含量逐渐减少。磁铁矿从边缘向中心呈V、Ca增加，Ti、Mn、Si、Cr、Sc、Zn减少的趋势，粒度从围岩向内部先增大后向中心减小;磁铁矿中的特征包裹体是磷铁矿-碳酸岩管边缘带内的硅镁矾，中间带内的尖晶石，和钛铁矿在内区。这种分带模式似乎是由于富含流体的岩浆柱的冷却和快速脱气（压力下降）以及随后的气成作用和热液作用而形成的。
The Kovdor baddeleyite-apatite-magnetite deposit in the Kovdor phoscorite-carbonatite pipe is situated in the western part of the zoned alkali-ultrabasic Kovdor intrusion (NW part of the Fennoscandinavian shield; Murmansk Region, Russia). We describe major intrusive and metasomatic rocks of the pipe and its surroundings using a new classification of phoscorite-carbonatite series rocks, consistent with the IUGS recommendation. The gradual zonation of the pipe corresponds to the sequence of mineral crystallization (forsterite-hydroxylapatite-magnetite-calcite). Crystal morphology, grain size, characteristic inclusions, and composition of the rock-forming and accessory minerals display the same spatial zonation pattern, as do the three minerals of economic interest, i.e. magnetite, hydroxylapatite, and baddeleyite. The content of Sr, rare earth elements (REEs), and Ba in hydroxylapatite tends to increase gradually at the expense of Si, Fe, and Mg from early apatite-forsterite phoscorite (margins of the pipe) through carbonate-free, magnetite-rich phoscorite to carbonate-rich phoscorite and phoscorite-related carbonatite (inner part). Magnetite displays a trend of increasing V and Ca and decreasing Ti, Mn, Si, Cr, Sc, and Zn from the margins to the central part of the pipe; its grain size initially increases from the wall rocks to the inner part and then decreases towards the central part; characteristic inclusions in magnetite are geikielite within the marginal zone of the phoscorite-carbonatite pipe, spinel within the intermediate zone, and ilmenite within the inner zone. The zoning pattern seems to have formed due to both cooling and rapid degassing (pressure drop) of a fluid-rich magmatic column and subsequent pneumatolytic and hydrothermal processes.