High-pressure phases in shock-induced melt veins of the Umbarger L6 chondrite: Constraints of shock pressure
Citation
Xie, Z., & Sharp, T. G. (2004). High‐pressure phases in shock‐induced melt veins of the Umbarger L6 chondrite: Constraints of shock pressure. Meteoritics & Planetary Science, 39(12), 2043-2054.Publisher
The Meteoritical SocietyJournal
Meteoritics & Planetary ScienceAdditional Links
https://meteoritical.org/Abstract
We report a previously undocumented set of high-pressure minerals in shock-induced melt veins of the Umbarger L6 chondrite. High-pressure minerals were identified with transmission electron microscopy (TEM) using selected area electron diffraction and energy-dispersive X-ray spectroscopy. Ringwoodite (Fa30), akimotoite (En11Fs89), and augite (En42Wo33Fs25) were found in the silicate matrix of the melt vein, representing the crystallization from a silicate melt during the shock pulse. Ringwoodite (Fa27) and hollandite-structured plagioclase were also found as polycrystalline aggregates in the melt vein, representing solid state transformation or melting with subsequent crystallization of entrained host rock fragments in the vein. In addition, Fe2SiO4-spinel (Fa66-Fa99) and stishovite crystallized from a FeO-SiO2-rich zone in the melt vein, which formed by shock melting of FeO-SiO2-rich material that had been altered and metasomatized before shock. Based on the pressure stabilities of the high-pressure minerals, ringwoodite, akimotoite, and Ca-clinopyroxene, the melt vein crystallized at approximately 18 GPa. The Fe2SiO4-spinel + stishovite assemblage in the FeO-SiO2- rich melts is consistent with crystallization of the melt vein matrix at the pressure up to 18 GPa. The crystallization pressure of ~18 GPa is much lower than the 4590 GPa pressure one would conclude from the S6 shock effects in melt veins (Stöffler et al. 1991) and somewhat less than the 25-30 GPa inferred from S5 shock effects (Schmitt 2000) found in the bulk rock.Type
Articletext
Language
enISSN
1945-5100ae974a485f413a2113503eed53cd6c53
10.1111/j.1945-5100.2004.tb00095.x