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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Microbial alteration of 0-30-Ma seafloor and sub-seafloor basaltic glasses from the Australian Antarctic Discordance
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Microbial alteration of 0-30-Ma seafloor and sub-seafloor basaltic glasses from the Australian Antarctic Discordance

机译：来自澳大利亚南极不一致性的0-30 Ma海底和海底玄武岩微生物的变化

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摘要

Scanning electron microscopic observations of alteration rims in basaltic glasses dredged from 0-2.5-Ma seafloor and drilled from 18-28-Ma ocean crust (Ocean Drilling Program (ODP) Leg 187) in the Australian Antarctic Discordance (AAD) document the presence of endolithic microbes in altered basalt glass. In very young AAD lavas, ～10-μm-thick alteration rims are developed along intersecting fractures and cracks, and the altered glass contains numerous spherical,, rod- and star-shaped, partially fossilised microbial cells, similar to those from the Arctic ridges [1,2]. In 2.5-Ma basalt glasses, altered rims are up to 250 μm thick, and zeolite (phillipsite) is present within many fractures. Spherical cells occur in porous outer zones of alteration rims and on zeolite crystal surfaces within fractures, indicating that microbial activity persists in the region for at least 2.5 Ma. Mn-rich microbial cell-encrustations associated with zeolite suggest that Mn is used in an energy yielding metabolic process. Combined with recent results from the Arctic ridges the results from this study demonstrate that endolithic microbial growth is a persistent feature of mid-ocean spreading ridges. In glasses from ODP cores, ～1-mm-thick alteration rims are developed along the widest fractures lined with Mn(Fe)-oxyhydroxides and/or clay and filled by zeolite and calcite. Most common, however, are <10-200-μm-thick rims developed along zeolite-filled, more narrow fractures and cracks. Zeolite-filled fractures with only minor to no alteration indicate several episodes of fracturing followed by relatively fast sealing. There is no age progression in alteration thickness along fractures or other characteristics, suggesting that alteration is essentially completed between 2.5 and 18 Ma. A comparison of alteration in the 2.5-Ma glass with that in the ODP samples indicates that a significant proportion of the glass alteration in the drilled samples developed prior to burial, although one type of diffuse, highly irregular front that is only observed in the ODP samples most likely developed after burial. These diffuse alteration fronts are caused by dissolution and alteration of the glass into minute globules, 0.05-0.2 μm in diameter, with no associatedd microbial morphologies. Fossilised, Mn-rich cells do occur within zeolitefilled fractures, possibly indicating that microbial activity continued in the fractures for as long as circulation continued. The apparent non-biological origin of diffuse, irregular alteration fronts in buried AAD glasses indicates that these textural features are not reliable as diagnostic criteria for the existence of a deep biosphere in the volcanic ocean crust.
机译：在澳大利亚南极不一致性（AAD）中从0-2.5-Ma的海底挖出并从18-28-Ma的海底钻出的玄武岩玻璃的变缘的扫描电子显微镜观察（海洋钻探计划（ODP）腿187）。改变的玄武岩玻璃中的内含石块微生物。在非常年轻的AAD熔岩中，沿相交的裂缝和裂缝形成了约10μm厚的蚀变边缘，蚀变的玻璃含有大量球形，杆状和星形的部分化石微生物细胞，类似于北极山脊中的微生物细胞。 [1,2]。在2.5 Ma的玄武岩玻璃中，改变后的镜框厚度可达250μm，并且在许多裂缝中都存在沸石（磷灰石）。球形细胞出现在蚀变边缘的多孔外部区域和裂缝内的沸石晶体表面上，表明微生物活性在该区域持续至少2.5 Ma。与沸石相关的富含锰的微生物细胞结壳表明，锰可用于产生能量的代谢过程。结合北极山脊的最新结果，这项研究的结果表明，石器内生微生物的生长是中海扩张脊的持续特征。在ODP芯的玻璃中，沿最宽的裂缝（内衬Mn（Fe）-羟基氧化物和/或粘土，并填充有沸石和方解石）形成了〜1毫米厚的蚀变边缘。然而，最常见的是沿填充沸石的更窄的裂缝和裂纹形成的厚度小于10-200μm的轮辋。沸石填充的裂缝只有很小的变化甚至没有变化，表明发生了几次破裂，随后密封相对较快。沿裂缝或其他特征的蚀变厚度没有年龄变化，表明蚀变基本上在2.5至18 Ma之间完成。将2.5 Ma玻璃的变化与ODP样品的变化进行比较表明，虽然在ODP中仅观察到一种弥散的高度不规则的正面，但在埋藏之前已钻出的样品中有很大比例的玻璃变化。埋葬后极有可能出现样品。这些扩散的变化前沿是由玻璃溶解和变化成直径为0.05-0.2μm的微小小球而引起的，没有相关的微生物形态。沸石充填的裂缝中确实存在化石化的富锰细胞，这可能表明微生物的活性在裂缝中持续了很长时间。埋藏的AAD玻璃中弥散的，不规则的变化锋面的明显非生物起源表明，这些结构特征不能可靠地作为火山海地壳深生物圈存在的诊断标准。

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