claybearingassemblages
Nicholas ToscaNASA Mars Fundamental Research Program, Clay-Bearing Assemblages from Alteration of Synthetic Martian Basalt: An Experimental Study Despite their utility as tracers of global scale climate on Earth, our understanding of Martian clays, and of the martian clay cycle, is in its relative infancy. To provide a foundation for interpreting results from the upcoming Mars Science Laboratory (MSL) mission, and to support current and future remote sensing observations, an improved understanding of the martian clay cycle is needed. Here, we focus on an understanding of the first step of the Martian clay cycle: What is the nature of clay-bearing mineral assemblages that arise from the alteration of Martian basalt? To fully address this issue, we will focus on three specific questions:
1. What clay minerals are produced from the alteration of Martian basalt under low and high temperature aqueous conditions? We will address this question with the synthesis of martian basalt of known composition and mineralogy. Once synthesis is complete, we will conduct a suite of closed-system alteration experiments probing the conditions that yield clay minerals in the laboratory at low temperature (e.g., <25-50oC). Also, we will conduct a suite of closed-system alteration experiments at high temperature (e.g., 100-300oC) using identical synthetic basalt utilized in low temperature experiments.
2. What other minerals occur with clays under low and high temperature alteration and can these minerals be used to help constrain alteration conditions? Low and high temperature basalt alteration experiments will focus on the presence and absence of specific non-clay minerals (e.g., carbonates, zeolites, etc.) in an effort to track the character of the entire mineral assemblage during clay formation.
3. How does the entire mineral assemblage change as a function of temperature and environmental parameters (including initial pH, redox, water-rock ratio and pCO2)? Over the course of the experimental program, we will systematically link alteration mineralogy to aqueous chemistry, focusing on environmental parameters that may have had the greatest influence on habitability of the Martian surface. We will also characterize the differences and similarities, where they occur, between low temperature and hydrothermal clay-bearing alteration assemblages.
The results of this study will contribute to a chemical database describing the formation of clay-bearing mineral assemblages from synthetic Martian basalt. These data will lay the groundwork for the study of more complex post-formational processes such as diagenesis, metamorphism and sedimentary mixing. In due course, these data will help place constraints on martian paleo-climates as well as the nature of water and habitability on early Mars through time.
1. What clay minerals are produced from the alteration of Martian basalt under low and high temperature aqueous conditions? We will address this question with the synthesis of martian basalt of known composition and mineralogy. Once synthesis is complete, we will conduct a suite of closed-system alteration experiments probing the conditions that yield clay minerals in the laboratory at low temperature (e.g., <25-50oC). Also, we will conduct a suite of closed-system alteration experiments at high temperature (e.g., 100-300oC) using identical synthetic basalt utilized in low temperature experiments.
2. What other minerals occur with clays under low and high temperature alteration and can these minerals be used to help constrain alteration conditions? Low and high temperature basalt alteration experiments will focus on the presence and absence of specific non-clay minerals (e.g., carbonates, zeolites, etc.) in an effort to track the character of the entire mineral assemblage during clay formation.
3. How does the entire mineral assemblage change as a function of temperature and environmental parameters (including initial pH, redox, water-rock ratio and pCO2)? Over the course of the experimental program, we will systematically link alteration mineralogy to aqueous chemistry, focusing on environmental parameters that may have had the greatest influence on habitability of the Martian surface. We will also characterize the differences and similarities, where they occur, between low temperature and hydrothermal clay-bearing alteration assemblages.
The results of this study will contribute to a chemical database describing the formation of clay-bearing mineral assemblages from synthetic Martian basalt. These data will lay the groundwork for the study of more complex post-formational processes such as diagenesis, metamorphism and sedimentary mixing. In due course, these data will help place constraints on martian paleo-climates as well as the nature of water and habitability on early Mars through time.
