A hydrothermal system associated with the Siljan impact structure, Sweden--implications for the search for fossil life on Mars.
A hydrothermal system associated with the Siljan impact structure, Sweden--implications for the search for fossil life on Mars.
复制标题
与瑞典 Siljan 撞击结构相关的热液系统——对在火星上寻找化石生命的启示。
作者：
T. Hode;Ilka von Dalwigk;C. Broman
西尔扬环形结构（368 +/- 1.1 Ma）是欧洲已知的最大的撞击结构。它伊萨个65公里宽，侵蚀，复杂的影响结构，显示了几个结构单元，包括一个中央隆起区周围的环形凹陷。与撞击坑相关的是撞击后热液系统的痕迹，由沉淀和蚀变的热液矿物组合表明。结晶热液矿物包括中央隆起外缘与花岗质岩石伴生的石英脉和角砾岩充填物，以及中央隆起外围与古生代碳酸盐岩伴生的方解石、萤石、方铅矿和闪锌矿脉。方解石和萤石中水/气和油/气两相包裹体显示均一化温度在75 ℃ ~ 137 ℃之间。据估计，侵蚀卸载约为1公里，地层温度可能不会超过10-15摄氏度。流体包裹体的冰融温度表明盐含量非常低，降低了加里东造山运动期间沉淀成矿的可能性。我们的研究结果表明，大的影响诱导低温热液系统，可能是嗜热生物的栖息地。因此，火星上的大型撞击结构可能是寻找嗜热生物化石的合适目标。
The Siljan ring structure (368 +/- 1.1 Ma) is the largest known impact structure in Europe. It isa 65-km-wide, eroded, complex impact structure, displaying several structural units, including a central uplifted region surrounded by a ring-shaped depression. Associated with the impact crater are traces of a post-impact hydrothermal system indicated by precipitated and altered hydrothermal mineral assemblages. Precipitated hydrothermal minerals include quartz veins and breccia fillings associated with granitic rocks at the outer margin of the central uplift, and calcite, fluorite, galena, and sphalerite veins associated with Paleozoic carbonate rocks located outside the central uplift. Two-phase water/gas and oil/gas inclusions in calcite and fluorite display homogenization temperatures between 75 degrees C and 137 degrees C. With an estimated erosional unloading of approximately 1 km, the formation temperatures were probably not more than 10-15 degrees C higher. Fluid inclusion ice-melting temperatures indicate a very low salt content, reducing the probability that the mineralization was precipitated during the Caledonian Orogeny. Our findings suggest that large impacts induce low-temperature hydrothermal systems that may be habitats for thermophilic organisms. Large impact structures on Mars may therefore be suitable targets in the search for fossil thermophilic organisms.