Analyses of Dike-induced Deformation and Martian Graben Systems, 20-R9797

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Principal Investigators
Danielle Y. Wyrick
Nancy K. Adams
Alan P. Morris
David A. Ferrill

Inclusive Dates:  03/27/08 – 07/27/08

Background - Mars is characterized by large volcanic and tectonic centers with distinct sets of graben systems that extend radially for distances of hundreds to thousands of kilometers. Fault systems on Mars bear a striking resemblance to fault systems on Earth, including geometric features such as horsts, grabens, relay ramps and breached relay ramps, and en echelon arrangement of faults and grabens. In addition, extensional faults on Mars exhibit scaling characteristics similar to those on Earth. Formation of these grabens has been attributed to extensional fractures, dilational faulting, and volcanic dike propagation. The dike-induced graben hypothesis has been widely used to interpret underlying dikes and dike swarms and to help constrain the volcanic history of Mars.

To date, there has been little detailed field-based analysis of dike-induced structural deformation. Because of the significance to the volcanic and tectonic history of Mars and the implications for potential astrobiological research sites, a better understanding of the dynamic interaction between volcanic activity and the structural response of adjacent and cogenetic faults and fractures is required. Research to date on Martian dike propagation has almost exclusively relied on boundary element models to predict surface deformation and estimate dike characteristics such as depth to dike tip, and none has provided observational evidence from Earth analog sites. In this project, we examined the extent to which igneous activity can create and/or reactivate faults and fractures based on data collected at an Earth analog location where subsurface dike emplacement has occurred. This investigation focused on using remote sensing data of the field study area to establish natural, real-world benchmarks for use in follow-on research proposals to investigate volcanic-tectonic interactions on Mars. This project built upon our current expertise in Martian tectonics while expanding into a new technical area — the interaction between igneous and structural deformation processes.

Approach - Project tasks focused on performing remote sensing and field site characterization of structural deformation features associated with terrestrial volcanic activity in Big Bend Ranch State Park and Big Bend National Park in west Texas. The goals of this work were to identify deformation characteristics of active dike injection using field analysis, including field mapping of fault and fracture patterns relative to subsurface dike emplacement, both in known and inferred locations. These analyses were compared with remote sensing data to determine key characteristics of subsurface igneous activity. This analysis provided "ground-truthing" examples of dike-induced deformation. Specific tasks included analysis of remote sensing data for the field site to determine the best exposures and field sites, reconnaissance field investigations of potential dike intrusion sites, and re-evaluation of remote sensing data in light of "ground-truthing" activities.

Accomplishments - SwRI researchers identified candidate field sites for follow-on characterization of dike-induced structural deformation. This established natural, real-world benchmarks for investigation of volcanic-tectonic interactions on Mars. Researchers were able to confirm (and in some cases disprove) remote sensing data based on ground-truthing. Results of this work have provided a proof-of-concept of our approach toward understanding the extent to which igneous activity can create and/or reactive faults and fractures and interpreting these processes in remote sensing data. Future modeling efforts, including numerical modeling, will benefit from the incorporation of the complex real-world dike geometries exhibited in our field sites. Findings from this project suggested that a re-evaluation of Martian data sets in light of ground-truthing field activities to determine whether key signatures can be found on Mars. Project results contributed to reconsideration and funding of a NASA proposal, a submitted journal manuscript, and an invited presentation at a conference.

Grabens on the surface of Mars exhibit many of the same characteristics as faults on Earth. While current hypotheses favor the interpretation that these extensional features are caused by underlying volcanic dikes, there is a lack of Earch analogs to confirm that this volcanic process can product significant surface deformation.

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