Evidence for impact induced pressure gradients on the Allende CV3 parent body: Consequences for fluid and volatile transport
Evidence for impact induced pressure gradients on the Allende CV3 parent body: Consequences for fluid and volatile transport
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阿连德 CV3 母体上撞击引起的压力梯度的证据：液体和挥发物运输的后果
DOI：
10.1016/j.epsl.2016.09.015
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发表时间：
2016
影响因子：
5.3
通讯作者：
J. Simon
中科院分区：
文献类型：
--
作者：
A. Tait;K. Fisher;P. Srinivasan;J. Simon
与Vigarano（CV）母体有关的碳质方解石，表现出多种氧化/还原蚀变矿物学（McSween，1977）。虽然流体经常被引用为发生这种情况的介质（Rubin，2012），但解释这种流体如何迁移的机制，以及为什么来自同一行星体的某些陨石亚型比其他陨石亚型氧化程度更高仍然难以捉摸。在我们的研究中，我们检查了一块著名的阿连德（CV 3 OxA）陨石。使用多种岩石学技术（例如，Fry和Flinn）和计算机断层扫描（CT）的结果表明，该岩石具有较强的穿透性平面组构，这是由其主要组分之间的应变分配引起的：富钙铝包裹体（CAIs）（64.5%CT）>基质（21.5%Fry）>球粒（17.6%CT）。除了平面织物，我们发现了一个强大的线理所定义的排列的最大伸长率的扁平颗粒解释为已开发的影响事件。线理的存在可能是非共轴变形，或者是机械异质靶材料的结果。在后一种情况下，它可能是由于通过先前的冲击压实（MacPherson和Krot，2014年）形成的不连续的地下冰和/或织物块而形成的，这将促进冲击后立即在目标材料内优先流动，压实孔隙空间。我们认为，结构控制运动的蚀变流体在小行星母体沿着压力梯度的次生矿物的形成，这可能最终导致不同的氧化亚型。
Carbonaceous chondrites, such as those associated with the Vigarano (CV) parent body, exhibit a diverse range of oxidative/reduced alteration mineralogy (McSween, 1977). Although fluids are often cited as the medium by which this occurs (Rubin, 2012), a mechanism to explain how this fluid migrates, and why some meteorite subtypes from the same planetary body are more oxidized than others remains elusive. In our study we examined a slab of the well-known Allende (CV3OxA) meteorite. Using several petrological techniques (e.g., Fry's and Flinn) and Computerized Tomography (CT) we discover it exhibits a strong penetrative planar fabric, resulting from strain partitioning among its major components: Calcium–Aluminum-rich Inclusions (CAIs) (64.5%CT) > matrix (21.5%Fry) > chondrules (17.6%CT). In addition to the planar fabric, we found a strong lineation defined by the alignment of the maximum elongation of flattened particles interpreted to have developed by an impact event. The existence of a lineation could either be non-coaxial deformation, or the result of a mechanically heterogeneous target material. In the later case it could have formed due to discontinuous patches of sub-surface ice and/or fabrics developed through prior impact compaction (MacPherson and Krot, 2014), which would have encouraged preferential flow within the target material immediately following the impact, compacting pore spaces. We suggest that structurally controlled movement of alteration fluids in the asteroid parent body along pressure gradients contributed to the formation of secondary minerals, which may have ultimately lead to the different oxidized subtypes.