The nature of the groundmass of surficial suevite from the Ries impact structure, Germany, and constraints on its origin
The nature of the groundmass of surficial suevite from the Ries impact structure, Germany, and constraints on its origin
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德国里斯冲击结构地表铁钙石基质的性质及其起源的限制
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发表时间：
2004
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通讯作者：
J. Spray
中科院分区：
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作者：
G. Osinski;R. Grieve;J. Spray
利用光学和分析扫描电子显微镜对Ries撞击结构的表面结构进行了野外研究。这些岩石的基质包括方解石、粘土矿物、冲击熔融玻璃、微晶(斜长石、石榴石和辉石)、方沸石和含钡磷灰石。后一种沸石是第二相。观察到了丰富的结构：各种基质相之间错综复杂的流动结构，其他相中每一相的球状结构，方解石中的磁黄铁矿球体，粘土球体进入硅酸盐玻璃和/或方解石中，磷灰石碎屑上的方沸石真面体过度生长，以及基质中的淬火结构微晶。成团方解石的FeO、MnO和SiO_2含量高于石灰石靶材。闪锌矿“粘土矿物”的组成变化很大，并不总是与蒙脱石一致。在基质中区分出三种类型的玻璃。第一类玻璃富含二氧化硅，明显来自沉积盖层中的砂岩，而其他两种类型的玻璃的原岩尚不清楚。
Abstract— Surficial suevites from the Ries impact structure have been investigated in the field and using optical and analytical scanning electron microscopy. The groundmass of these suevites comprises calcite, clay minerals, impact melt glass, crystallites (plagioclase, garnet, and pyroxene), francolite, and Ba‐phillipsite. The latter zeolite is a secondary phase. Abundant textures have been observed: intricate flow textures between the various groundmass phases, globules of each phase in the other phases, spheroids of pyrrhotite in calcite, the “budding‐off” of clay globules into silicate glass and/or calcite, euhedral overgrowths of francolite on apatite clasts, and quench‐textured crystallites in the groundmass. Groundmass‐forming calcite displays higher FeO, MnO, and SiO2 contents than limestone target material. The composition of suevite “clay minerals” is highly variable and not always consistent with montmorillonite. Three types of glasses are distinguished in the groundmass. Type 1 glasses are SiO2‐rich and are clearly derived from sandstones in the sedimentary cover, while the protoliths of the other two glass types remains unclear.