Lateral Reactive Infiltration in a Vertical Gabbroic Crystal Mush, Skaergaard Intrusion, East Greenland
Lateral Reactive Infiltration in a Vertical Gabbroic Crystal Mush, Skaergaard Intrusion, East Greenland
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DOI：
10.1093/petrology/egt003
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发表时间：
2012-12
影响因子：
3.9
通讯作者：
O. Namur;M. Humphreys;M. Holness
中科院分区：
文献类型：
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作者：
O. Namur;M. Humphreys;M. Holness
Skaergaard侵入体（东格陵兰）的边缘边界系列在岩浆房的垂直壁上就地结晶。它被细分为一个外部的无带区和一个内部的有带区。带状分区包含丰富的厘米至分米厚的带为主的细粒镁铁质矿物，从几乎平面的形态演变为深深的扇贝和指状与侵入边缘的距离增加。这些带的形态是让人想起的反应前所描述的沉积盆地渗透的反应流体。我们建议，在Skaergaard边缘边界系列的条带产生的化学不平衡，从主岩浆体的原始液体吸入到晶体糊状物，在凝固过程中的糊状物的收缩驱动。液体多孔流动导致部分溶解的泥中已演化的既存镁铁质矿物。这改变了糊状液体的成分，使其能够结晶镁铁质岩石，并含有非常少量的斜长石成分。这种液体的突然凝固，导致胶体带的形成，被解释为一些镁铁质矿物成分（如橄榄石，单斜辉石，铁钛氧化物）在渗透熔体的过饱和。我们认为，胶体带的形态演变是一个结果，增加晶体糊状物厚度进行分化。
The Marginal Border Series of the Skaergaard intrusion (East Greenland) crystallized in situ on the vertical walls of the magma chamber. It is subdivided into an outer Unbanded Division and an inner Banded Division. The Banded Division contains abundant centimetre- to decimetre-thick bands dominated by fine-grained mafic minerals, with a morphology evolving from almost planar to deeply scalloped and fingered with increasing distance from the intrusion margin. The morphology of these bands is reminiscent of the reaction fronts described in sedimentary basins infiltrated by reactive fluids. We propose that the banding in the Skaergaard Marginal Border Series is produced by chemical disequilibrium resulting from the suction of primitive liquid from the main magma body into the crystal mush, driven by shrinkage of the mush during solidification. Liquid porous flow results in partial dissolution of evolved pre-existing mafic minerals in the mush. This changes the mush liquid composition to one capable of crystallizing mafic rocks with a very minor plagioclase component. Abrupt solidification of this liquid, resulting in the formation of the colloform bands, is explained by supersaturation of some mafic mineral components (e.g. olivine, clinopyroxene, Fe–Ti oxides) in the infiltrating melt. We suggest that the morphological evolution of the colloform bands is a consequence of increasing crystal mush thickness with progressive differentiation.