Contribution of early impact events to metal‐silicate separation, thermal annealing, and volatile redistribution: Evidence in the Pułtusk H chondrite
Contribution of early impact events to metal‐silicate separation, thermal annealing, and volatile redistribution: Evidence in the Pułtusk H chondrite
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早期撞击事件对金属硅酸盐分离、热退火和挥发物重新分布的贡献：Pułtusk H 球粒陨石中的证据
DOI：
10.1111/maps.12933
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发表时间：
2017
影响因子：
2.2
通讯作者：
A. Krzesińska
中科院分区：
文献类型：
--
作者：
A. Krzesińska
三维X射线断层重建和岩石学研究揭示了Puertusk H球粒陨石中大量的金属积累。在这些堆积物的接触处，铁玄岩富含陨硫铁。岩石含有富含斜长石的条带，其纹理表明是熔融结晶。异常大的磷酸盐与斜长石有关，由镁橄榄石、氟磷灰石和氯磷灰石的组合组成。金属堆积物是由撞击熔化、金属硫化物熔体的快速分离以及这种熔体与破裂的火山口基底的结合形成的。撞击最有可能发生在H球粒陨石母体的早期演化过程中，当时撞击后的热量与放射成因热量重叠。这使得金属熔体能够缓慢冷却并分离成富含金属和富含硫化物的部分。这导致了与金属聚集体接触的玄武质岩石的重结晶和冲击熔体的结晶。由于缓慢冷却时的氧化条件，磷从金属中释放出来，并被硅酸盐冲击熔体所包含。熔体也是挥发物的宿主。在进一步冷却后，磷与硅酸盐反应，导致镁橄榄石的形成，而挥发物分配到残留的富含卤素的干燥流体中。在后期阶段，流体将merrilite改变为片状Cl/F‐磷灰石。上述蚀变序列表明，在早期演化过程中的影响，南极母体可能有助于局部金属偏析和硅酸盐熔融。此外，震后条件支持的次级过程：成分/纹理平衡，挥发物的重新分配，和流体的改变。
Three‐dimensional X‐ray tomographic reconstructions and petrologic studies reveal voluminous accumulations of metal in Pułtusk H chondrite. At the contact of these accumulations, the chondritic rock is enriched in troilite. The rock contains plagioclase‐rich bands, with textures suggesting crystallization from melt. Unusually large phosphates are associated with the plagioclase and consist of assemblages of merrillite, and fluorapatite and chlorapatite. The metal accumulations were formed by impact melting, rapid segregation of metal‐sulfide melt and the incorporation of this melt into the fractured crater basement. The impact most likely occurred in the early evolution of the H chondrite parent body, when post‐impact heat overlapped with radiogenic heat. This enabled slow cooling and separation of the metallic melt into metal‐rich and sulfide‐rich fractions. This led to recrystallization of chondritic rock in contact with the metal accumulations and the crystallization of shock melts. Phosphorus was liberated from the metal and subsumed by the silicate shock melt, owing to oxidative conditions upon slow cooling. The melt was also a host for volatiles. Upon further cooling, phosphorus reacted with silicates leading to the formation of merrillite, while volatiles partitioned into the residual halogen‐rich, dry fluid. In the late stages, the fluid altered merrillite to patchy Cl/F‐apatite. The above sequence of alterations demonstrates that impact during the early evolution of chondritic parent bodies might have contributed to local metal segregation and silicate melting. In addition, postshock conditions supported secondary processes: compositional/textural equilibration, redistribution of volatiles, and fluid alterations.
影响因子：
2.2
作者：
Ciesla, Fred J.;Davison, Thomas M.;O'Brien, David P.
通讯作者：
O'Brien, David P.