Where are the Shocked Grains in the Hadean Zircon Record? Insights on the Preservation of Shocked Zircon and Their U-Pb Systematics

Erickson, T M ; Cavosie, A J ; Timms, N E ; Reddy, S M ; Nemchin, A A ; Cox, M A ; Schmieder, M ; Kring, D A

关键词: CRATERS;    DEFORMATION;    GRAIN BOUNDARIES;    MICROSTRUCTURE;    MINERALS;    POLYCRYSTALS;    PRECAMBRIAN PERIOD;    SEDIMENTS;    ZIRCONIUM OXIDES;    AGGREGATES;    CRYSTALLINITY;    DEPOSITION;    EROSION;    GEOCHEMISTRY;    METAMORPHISM (GEOLOGY);    SILICON DIOXIDE;    TERRACES (LANDFORMS);   

RP-ID  :  JSC-E-DAA-TN60129

学科分类：空间科学

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

While the earliest history of many planetary bodies within the inner Solar System is dominated by intense bombardment, this record is missing from Earth due to active tectonics and erosion. Where-as rocks from the earliest history of Earth are absent, mineral relics, such as ancient detrital zircon concentrated in sediments within the Jack Hills, Narryer, Illara and Maynard Hills greenstone belts of the Yilgarn Craton in Western Australia preserve a record of this time.Shock in zircon: During shock deformation, resulting from hyper-velocity impact, zircon can be modified in crystallographically-controlled ways. This includes the development of planar and subplanar low-angle grain boundaries, the formation of mechanical twins, transformation to the high pressure polymorph reidite, development of polycrystalline microtexture, and dissociation to its dioxide constituents SiO2 and ZrO2.