Mobilization and enrichment of high-field strength elements during late- and post-magmatic processes in the Shuiquangou syenitic complex, Northern China
Mobilization and enrichment of high-field strength elements during late- and post-magmatic processes in the Shuiquangou syenitic complex, Northern China
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DOI：
10.1016/s0009-2541(03)00162-1
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发表时间：
2003-10
期刊：
影响因子：
3.9
通讯作者：
Neng Jiang;Shihua Sun;X. Chu;T. Mizuta;D. Ishiyama
中科院分区：
文献类型：
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作者：
Neng Jiang;Shihua Sun;X. Chu;T. Mizuta;D. Ishiyama
水泉沟正长杂岩由黑正长岩和浅色正长岩组成。在东北部，有一个小的地区，白色正长岩受到蚀变的影响。与新鲜的浅色正长岩相比，蚀变的浅色正长岩含有更高浓度的高场强元素（HFSE），特别是Nb，Zr，REE和Y。蚀变浅色正长岩的稀土元素配分模式显示出中等程度的负Eu异常，而新鲜正长岩的稀土元素配分模式则显示出轻微的正Eu至无Eu异常。蚀变白正长岩中热液矿物组合中的褐帘石也比未蚀变白正长岩中自形岩浆褐帘石含有更高浓度的REE和Ti。根据矿物化学和全岩数据，将蚀变白长岩中HFSE的富集解释为热液流体所致。在新鲜的淡色正长岩，褐帘石出现在两个习惯，自形的，表明一个主要的岩浆起源和anhedral的建议晚岩浆起源。后者的REE和Ti含量高于前者。据推测，自形褐帘石的形成与自形褐帘石的蚀变是同时代的，是由正长岩浆直接产生的残余岩浆流体作用的结果。岩浆自形褐帘石的蚀变及稀土元素和钛元素在岩浆晚期自形褐帘石中的富集表明，这些元素被残余岩浆流体活化。残留的岩浆和热液流体具有高碱性和F含量的推断组成的特点，这表明F可能是最配位体络合高价阳离子。
The Shuiquangou syenitic complex consists of melasyenite and leucosyenite. In the northeastern part, there is a small area where the leucosyenite was affected by alteration. The altered leucosyenite contains much higher concentrations of high-field strength elements (HFSE), especially Nb, Zr, REE and Y compared to fresh leucosyenite. REE patterns of the altered leucosyenite show moderate negative Eu anomaly, in contrast to the slightly positive to non-anomalous Eu signature of the fresh syenitic rocks. Allanite from the hydrothermal mineral assemblage in the altered leucosyenite also contains much higher concentrations of REE and Ti than the euhedral magmatic allanites in unaltered leucosyenite. The enrichment of HFSE in altered leucosyenite was interpreted to be caused by the hydrothermal fluids based on mineral chemistry and whole-rock data. Within the fresh leucosyenite, allanite occurs in two habits, euhedral ones indicating a primary magmatic origin and anhedral ones suggesting a late-magmatic origin. The latter has higher concentrations of REE and Ti than the former. The anhedral allanite was presumed to be formed coeval with the alteration of the euhedral allanite as a result of residual magmatic fluid derived directly from the syenitic magma. The alteration of magmatic euhedral allanite and the enrichment of REE and Ti in the anhedral late-magmatic allanite suggest that these elements were mobilized by the residual magmatic fluid. Both residual late-magmatic and hydrothermal fluids have an inferred composition characterized by high alkalic and F contents, suggesting that F may be the most ligand that complexed the high-valence cations.