岩庄陨石的冲击熔融和元素再分配

发布时间：2018-04-13 00:38

本文选题：岩庄陨石 + 冲击熔体　；参考：《地球化学》2017年04期

【摘要】：岩庄陨石是受强烈冲击的H群普通球粒陨石,含有厘米级宽度的熔脉和熔块。冲击熔体中微量元素的分布,对了解在高温低压下从熔体分离结晶物相的元素再分配具有重要价值。本文以岩庄陨石中的全岩熔体、硅酸盐熔体和FeNi+FeS共结团粒中的FeNi金属三种物相为研究对象,利用激光剥蚀等离子体质谱技术,分别对其进行微量元素分析。结果表明:(1)该陨石冲击熔融后,Fe、Co和Ni等亲铁元素主要富集在全岩熔体内的FeNi金属相中,而Cr、V、Ti和Mn等则主要进入从硅酸盐熔体中晶出的微晶辉石晶格内,以置换M1位上的Al~(3+)。(2)Cu、Ga和Pb等亲铜元素也大部分都富集在FeNi金属相中,而挥发性较强的Zn,在陨石熔融时虽有少量丢失,但主要进入硅酸盐熔体相内,赋存在微晶橄榄石和辉石晶格之中以置换Fe~(2+)。(3)Sc、Zr、Nb和Ta等亲石元素,基本上都赋存在硅酸盐熔体相中,但Nb和Ta的分异程度低,而FeNi金属相的Nb/Ta比值比硅酸盐熔体要偏低一倍多,说明高温高压下陨石熔融时,Nb比Ta更为活泼。(4)硅酸盐熔体和全岩熔体的稀土元素分布均具有明显的奇偶效应,总体呈现轻稀土富集,重稀土亏损的特点,而FeNi金属则呈现轻稀土相对亏损的特点,且其稀土总量比硅酸盐熔体低近三倍,说明稀土元素特别是轻稀土元素主要赋存在硅酸盐熔体中。铂族元素在陨石局部熔融后转移到共结团粒的FeNi金属之中。
[Abstract]:Yanzhuang meteorite is an ordinary chondrite of group H which is strongly impacted and contains a centimeter width of veins and melts.The distribution of trace elements in impact melts is of great value in understanding the redistribution of elements in the crystallization phase separated from the melt at high temperature and low pressure.In this paper, the phases of whole rock melt, silicate melt and FeNi metal in FeNi FeS co-agglomerates in Yanzhuang meteorite were studied. The trace elements were analyzed by laser denudation plasma mass spectrometry.The results show that the Fe _ (2 +) Fe _ (2) O _ (2) and Ni are mainly enriched in the FeNi phase in the whole rock melt after impact melting, while Cr ~ (2 +) V ~ (2 +) Ti and mn mainly enter the microcrystalline pyroxene lattice from the silicate melt.The copperophile elements, such as Al~(3 ~ (2 +), Cu ~ (2 +) Ga and Pb, which are substituted at M1 site, are also mostly enriched in the FeNi metallic phase. However, the highly volatile Al~(3, which is lost in a small amount during the melting of the meteorite, mainly enters the silicate melt phase.In the microcrystalline olivine and pyroxene lattices, the lipophilic elements such as Fe~(2 ~ (3) C ~ (3) C ~ (2 +) C ~ (2 +) Zr ~ (2 +) NB and Ta are mainly found in silicate melts, but the difference between NB and Ta is low, and the Nb/Ta ratio of FeNi metallic phase is more than twice as low as that of silicate melts.The results show that the distribution of rare earth elements in silicate melts and whole rock melts is more active than Ta at high temperature and high pressure. The distribution of rare earth elements in both melts and whole rock melts is characterized by enrichment of light rare earths and depletion of heavy rare earths.The FeNi metal is characterized by the relative depletion of light rare earth elements, and the total amount of rare earth elements is nearly three times lower than that of silicate melts, indicating that rare earth elements, especially light rare earth elements, mainly occur in silicate melts.Platinum group elements are transferred to the FeNi metal of conjunctive aggregates after partial melting of the meteorite.
【作者单位】：中国科学院矿物学与成矿学重点实验室广东省矿物物理与材料研究开发重点实验室中国科学院广州地球化学研究所;西北大学大陆动力学国家重点实验室;
【基金】：国家自然科学基金(41172046)
【分类号】：P185.83

【相似文献】