Early Diagenesis by Modern Acid Brines in Western Australia and Implications for the History of Sedimentary Modification on Mars
Early Diagenesis by Modern Acid Brines in Western Australia and Implications for the History of Sedimentary Modification on Mars
复制标题
西澳大利亚现代酸性卤水的早期成岩作用及其对火星沉积改造历史的影响
DOI：
10.2110/pec.12.102.0229
复制
发表时间：
2012
影响因子：
3.7
通讯作者：
S. Story
中科院分区：
文献类型：
--
作者：
B. Bowen;K. Benison;S. Story
Mineralogical and geochemical data collected from multiple sites on Mars suggest that acid saline surface waters and groundwater existed there in the past. The geologic context and sedimentology suggest that these acid saline waters were associated with groundwater-fed ephemeral lakes. Ephemeral acid saline lakes in southern Western Australia (WA) are some of the few known natural systems that have the same combination of extreme acid brine chemistry and lacustrine depositional setting as is observed on Mars. Thus, the WA acid saline environments provide a modern analog for understanding past depositional and diagenetic processes that may have occurred on Mars. Here, we examine surface sediments and sedimentary rocks that have been in contact with acid (pH down to ;1.5) and saline brines (total dissolved solids up to ;32%) in southern Western Australia. Through sedimentological, mineralogical, geochemical, and petrographic analyses, we identify the impacts of early diagenesis in and adjacent to eight acid saline lakes and evaluate the processes that have been important in creating these deposits. The combination of extreme chemistry, spatial variability, arid climate, and reworking by winds and floods contributes to make spatially complex depositional products that are a combination of siliciclastics and chemical sediments. Important syndepositional and very early diagenetic processes in these settings include the chemical precipitation of minerals from shallow groundwaters to form displacive crystals and cements, dissolution/partial dissolution of chemical sediments, replacement/partial replacement of some minerals, cracking due to repeated wetting and drying, and the formation of iron-oxide concretions. Minerals observed in these sediments include a variety of chlorides, sulfates, iron oxides, and phyllosilicates, many of which have textures and mineral associations that suggest authigenic formation. These observations are supported by the chemistry of the modern acid brines, which appear to be supersaturated with respect to these minerals. The range of early diagenetic products, compositions, and textures that are apparent in the WA acid saline lake sediments may provide insights into the processes that influenced the sediments on Mars and the timing of sedimentary formation processes on Mars.
