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Composition and origin of the volatile components released from the Pesyanoe aubrite by stepwise crushing and heating
Geochemistry ( IF 2.6 ) Pub Date : 2020-10-02 , DOI: 10.1016/j.chemer.2020.125686
C.A. Lorenz , A.I. Buikin , A.A. Shiryaev , O.V. Kuznetsova

Aubrites are achondritic meteorites (enstatite pyroxenites) that were formed in highly reduced magmatic environments on a differentiated parent body sharing a common oxygen isotope reservoir with enstatite chondrites (EC), Earth and Moon, and could be considered as a geochemical model of the early proto-Earth. Some pyroxenes of the Pesyanoe aubrite have high abundance of gaseous inclusions, captured during the crystallization of the rocks. Investigation of the inclusions by IR spectroscopy reveals presence of OH groups and C–H bonds. The former are assigned to protonated point defects in enstatite lattice and the latter to compounds occupying void walls. Molecular water and CO2 were not observed. Volatile components released from the samples of the Pesyanoe enstatite by stepwise crushing and heating are composed of CO2, H2O and a non-condensable phase. Hydrogen isotopic composition of volatiles extracted in form of molecular water in Px-separates varies in the range δD = −61 – −84‰ with mean value of δD = −73 ± 16‰ VSMOW and is within the ranges of ECs and Earth’s mantle. The total abundance of H2 in the pyroxene of Pesyanoe were estimated as at least 0.047 ppm that is too low in comparison with that of enstatite chondrites (≥30 ppm H2) and could indicate nearly complete degassing of the Pesyanoe primitive precursor material during the Pesyanoe parent body accretion or a mantle degassing in igneous differentiation process. In a last case a primitive precursor could have D/H ratio different from that of enstatite chondrites.



中文翻译:

Pesyanoe aubrite通过逐步粉碎和加热释放的挥发性成分的组成和来源

赤铁矿是软骨质陨石(顽辉辉石辉石),是在高度还原的岩浆环境中形成的,在一个分化的母体上,与母体共享一个常见的氧同位素储集层,与顽辉石球粒陨石(EC),地球和月球一起被认为是早期原型的地球化学模型。 -地球。Pesyanoe aubrite的一些辉石具有高含量的气态夹杂物,这些夹杂物是在岩石结晶过程中捕获的。通过IR光谱的夹杂物的调查显示OH的存在-基团和C-H键。前者被归为顽辉石晶格中的质子点缺陷,后者被归为占据空隙壁的化合物。分子水和CO 2没有观察到。通过逐步破碎和加热从Pesyanoe顽辉石样品中释放的挥发性成分由CO 2,H 2 O和不可凝相组成。Px分离物中以分子水形式提取的挥发物的氢同位素组成在δD= -61 – -84‰范围内变化,平均值δD= -73±16‰VSMOW,且在ECs和地幔范围内。Pesyanoe的辉石中H 2的总丰度估计至少为0.047 ppm,与顽辉陨石(≥30 ppm H 2)相比太低了),这可能表明在Pesyanoe母体增生过程中Pesyanoe原始前体物质几乎完全脱气,或者在火成岩分化过程中发生了地幔脱气。在最后一种情况下,原始的前驱体的D / H比可能不同于顽辉长方晶石的D / H比。

更新日期:2020-10-02
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