Subglacial hydrothermal alteration minerals in Jökulhlaup deposits of Southern Iceland, with implications for detecting past or present habitable environments on Mars.
Subglacial hydrothermal alteration minerals in Jökulhlaup deposits of Southern Iceland, with implications for detecting past or present habitable environments on Mars.
复制标题
冰岛南部杰古拉普沉积物中的冰下热液蚀变矿物对探测火星过去或现在的宜居环境具有重要意义。
作者：
N. Warner;J. Farmer
Jökulhlaups是陆地灾难性的洪水，通常由冰下火山爆发引发。类似的火山-冰相互作用可能在火星上很重要，岩浆/熔岩可能与火星的冰冻圈相互作用，产生灾难性的洪水。作为火星洪水期间沉积的沉积物的潜在类似物，冰岛的全新世砂岩主要是来自冰下环境的玄武岩碎屑，并在jökulhlaups期间沉积。矿床内的斜长凝灰岩和角砾岩代表主要蚀变岩性。斜长石在砂岩上的表面丰度为1- 20%。斜长角砾岩的X射线衍射（XRD）分析证实了沸石，蒙皂石，低石英，高岭石的矿物组合。斜长角砾岩碎屑和涂层的定向粉末X射线衍射图（< 2微米级）显示了随机有序的蒙皂石、蒙皂石/伊利石混合层、沸石和石英。同一斜长岩样品的可见光-近红外（VNIR）和短波红外（SWIR）光谱数据显示了与粘土和沸石有关的H2O/OH（-）吸收。利用先进星载热发射和反射辐射计（ASTER）图像，得到了白刺的短波红外光谱，揭示了Al-OH（-）和Si-OH（-）的吸收特征。已确定的蚀变矿物组合与冰下环境中玄武岩材料的低温（100-140摄氏度）热液蚀变一致。这些结果表明，潜在的火星类似网站，包含一套类似的水合矿物可能是过去的热液活动和位置，过去的可居住环境的微生物生命可能会被发现的指示。
Jökulhlaups are terrestrial catastrophic outfloods, often triggered by subglacial volcanic eruptions. Similar volcano-ice interactions were likely important on Mars where magma/lava may have interacted with the planet's cryosphere to produce catastrophic floods. As a potential analogue to sediments deposited during martian floods, the Holocene sandurs of Iceland are dominated by basaltic clasts derived from the subglacial environment and deposited during jökulhlaups. Palagonite tuffs and breccias, present within the deposits, represent the primary alteration lithology. The surface abundance of palagonite on the sandurs is 1-20%. X-ray diffraction (XRD) analysis of palagonite breccias confirms a mineral assemblage of zeolites, smectites, low-quartz, and kaolinite. Oriented powder X-ray diffractograms (< 2 microm fraction) for palagonite breccia clasts and coatings reveal randomly ordered smectite, mixed layer smectite/illite, zeolites, and quartz. Visible light-near infrared (VNIR) and shortwave infrared (SWIR) lab spectroscopic data of the same palagonite samples show H2O/OH(-) absorptions associated with clays and zeolites. SWIR spectra derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images of the sandurs reveal Al-OH(-) and Si-OH(-) absorption features. The identified alteration mineral assemblage is consistent with low temperature (100-140 degrees C) hydrothermal alteration of basaltic material within the subglacial environment. These results suggest that potential martian analog sites that contain a similar suite of hydrated minerals may be indicative of past hydrothermal activity and locations where past habitable environments for microbial life may be found.