Mineralogical and geochemical analyses of Antarctic lake sediments: a study of reflectance and Mössbauer spectroscopy and C, N, and S isotopes with applications for remote sensing on Mars
Mineralogical and geochemical analyses of Antarctic lake sediments: a study of reflectance and Mössbauer spectroscopy and C, N, and S isotopes with applications for remote sensing on Mars
复制标题
DOI：
10.1016/s0016-7037(01)00651-2
复制
发表时间：
2001-09
影响因子：
5
通讯作者：
J. Bishop;A. Lougear;J. Newton;P. Doran;H. Froeschl;A. Trautwein;W. Körner;C. Koeberl
中科院分区：
文献类型：
--
作者：
J. Bishop;A. Lougear;J. Newton;P. Doran;H. Froeschl;A. Trautwein;W. Körner;C. Koeberl
我们分析了南极洲干谷地区的湖底沉积物，以研究水化学对这些沉积物的矿物学和地球化学的影响，并评估火星上潜在生物标志矿物的远程光谱识别技术。人们对南极洲干谷地区的湖泊进行了研究，认为它们可能与早期火星上灭绝的湖泊环境类似。本研究中的沉积物岩芯是从泰勒谷常年冰雪覆盖的霍尔湖中收集的。这些沉积物取自湖泊含氧区的一个岩心和缺氧区的另一个岩心。观察到两个岩心在沉积物颜色、Fe(II)/Fe(III) 比、黄铁矿的存在、Fe、S 和一些微量元素的丰度以及 C、N 和 S 同位素分馏模式方面存在差异。结合可见红外反射光谱（0.3–25 μm）、穆斯堡尔光谱（77 和 4 K）以及 X 射线衍射的结果来确定这些样品的矿物学和成分。沉积物主要为斜长石、钾长石、石英和辉石。湖底生长着藻丛，在湖心各处都发现了有机物质。方解石在浅层含氧区域沉积物核心的某些层中丰富，而黄铁矿在霍尔湖深层缺氧区域核心的上部沉积层中丰富。对有机物和碳酸盐的光谱特征进行了有机碳和碳酸盐含量丰度的分析，以便选择最佳光谱带来远程识别行星风化层中的这些成分。在碳酸盐丰度低至 0.1 wt% CO2 时，检测到 4 和 6.8 μm（∼2500 和 1500 cm−1）附近的碳酸盐带。在 3.38、3.42 和 3.51 μm（2960、2925 和 2850 cm−1）处检测到有机碳丰度低至 0.06 wt% C 的有机特征。δ13C 和 δ15N 趋势显示缺氧区沉积物的有机历史比好氧区沉积物更复杂。在缺氧区核心中发现的生物黄铁矿与耗尽的 δ34S 值和高有机 C 水平有关，可用作火星古湖泊的潜在生物标志矿物。
We analyzed lake-bottom sediments from the Dry Valleys region of Antarctica to study the influence of water chemistry on the mineralogy and geochemistry of these sediments, as well as to evaluate techniques for remote spectral identification of potential biomarker minerals on Mars. Lakes from the Dry Valleys region of Antarctica have been investigated as possible analogs for extinct lake environments on early Mars. Sediment cores were collected in the present study from perennially ice-covered Lake Hoare in the Taylor Valley. These sediments were taken from a core in an oxic region of the lake and another core in an anoxic zone. Differences between the two cores were observed in the sediment color, Fe(II)/Fe(III) ratio, the presence of pyrite, the abundance of Fe, S, and some trace elements, and the C, N, and S isotope fractionation patterns. The results of visible-infrared reflectance spectroscopy (0.3–25 μm), Mössbauer spectroscopy (77 and 4 K), and X-ray diffraction are combined to determine the mineralogy and composition of these samples. The sediments are dominated by plagioclase, K-feldspar, quartz, and pyroxene. Algal mats grow on the bottom of the lake and organic material has been found throughout the cores. Calcite is abundant in some layers of the sediment core from the shallow, oxic region, and pyrite is abundant in the upper sediment layers of the core from the deep, anoxic region of Lake Hoare. Analysis of the spectroscopic features due to organics and carbonates with respect to the abundance of organic C and carbonate contents was performed in order to select optimal spectral bands for remote identification of these components in planetary regoliths. Carbonate bands near 4 and 6.8 μm (∼2500 and 1500 cm−1) were detected for carbonate abundances as low as 0.1 wt% CO2. Organic features at 3.38, 3.42, and 3.51 μm (2960, 2925, and 2850 cm−1) were detected for organic C abundances as low as 0.06 wt% C. The δ13C and δ15N trends show a more complex organic history for the anoxic region sediments than for the oxic region sediments. The biogenic pyrite found in the core from the anoxic zone is associated with depleted δ34S values and high organic C levels and could be used as a potential biomarker mineral for paleolakes on Mars.