Jenkins Laura E, King Ashley J, Lee Martin R, Daly Luke, Thompson Stephen P, Day Sarah J, Saunders Lucy, Martin Pierre-Etienne, Bintang Fahkri
School of Geographical and Earth Sciences, The University of Glasgow, Glasgow, G12 8RZ Scotland, UK.
Planetary Materials Group, Natural History Museum, London, SW7 5BD England, UK.
Earth Planets Space. 2024;76(1):172. doi: 10.1186/s40623-024-02116-2. Epub 2024 Dec 26.
The effects of post-hydration heating over a broad range of temperatures are evident in many Mighei-like carbonaceous (CM) chondrites as a variety of mineral transitions. To better understand these processes and how a CM chondrite's starting composition may have affected them, we experimentally heated two meteorites with different degrees of aqueous alteration, Allan Hills 83100 and Murchison, at 25 °C temperature steps from 200 °C to 950 °C and 300 °C to 750 °C, respectively. During heating, synchrotron in situ X-ray diffraction patterns were collected. With the exception of calcite decomposition and its products, most mineral transitions were unaffected by starting composition. Key observations include: (1) partial decomposition of tochilinite at 200 °C, which indicates that tochilinite breakdown might be a two-stage process due to its intergrown layers of brucite/amakinite and mackinawite; (2) the breakdown of serpentine occurring at 300 °C with transitional phases appearing at 525 °C and 575-600 °C, while secondary olivine formed at 600 °C; (3) cronstedtite decomposing faster than lizardite, (4) the formation of secondary enstatite at 750 °C, and (5) calcite decomposition temperature differing significantly between meteorites, occurring at 725 °C and 575 °C in ALH 83100 and Murchison, respectively. The results for calcite are likely controlled by differences in its microstructure and chemical composition, related to the meteorite's impact history and degree of aqueous alteration. The difference in calcite decomposition temperature also explains the contrasts in the observed breakdown products, with clinopyroxene occurring in both meteorites, and oldhamite only in ALH 83100. Mineral transitions due to post-hydration heating have been characterized with a high resolution XRD method, enabling a better understanding of processes occurring on the parent asteroids of CM chondrites.
The online version contains supplementary material available at 10.1186/s40623-024-02116-2.
在许多米盖伊型碳质（CM）球粒陨石中，水合后在很宽温度范围内加热的影响表现为各种矿物转变。为了更好地理解这些过程以及CM球粒陨石的初始成分可能如何影响它们，我们分别以25℃的温度步长，将两块具有不同程度水蚀变的陨石——阿伦丘陵83100和默奇森陨石，从200℃加热到950℃以及从300℃加热到750℃。在加热过程中，收集了同步辐射原位X射线衍射图谱。除方解石分解及其产物外，大多数矿物转变不受初始成分影响。主要观察结果包括：（1）200℃时纤蛇纹石的部分分解，这表明由于其水镁石/阿马金铁矿和马基诺矿的共生层，纤蛇纹石分解可能是一个两阶段过程；（2）蛇纹石在300℃时分解，在525℃和575 - 600℃出现过渡相，而次生橄榄石在600℃形成；（3）陨绿泥石比重蛇纹石分解得更快；（4）750℃时形成次生顽火辉石；（5）方解石分解温度在陨石之间有显著差异，在阿伦丘陵83100和默奇森陨石中分别为725℃和575℃。方解石的结果可能受其微观结构和化学成分差异的控制，这与陨石的撞击历史和水蚀变程度有关。方解石分解温度的差异也解释了观察到的分解产物的差异，两种陨石中均出现单斜辉石，而奥长石仅在阿伦丘陵83100中出现。水合后加热引起的矿物转变已通过高分辨率XRD方法进行了表征，从而能够更好地理解CM球粒陨石母体小行星上发生的过程。
在线版本包含可在10.1186/s40623 - 024 - 02116 - 2获取的补充材料。
