Reconciling extrusion tectonics, rifting, and lithosphere-asthenosphere coupling models for the Central Highlands diffuse igneous province, Vietnam

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The paradigm of plate tectonics represents the most fundamental planetary process on Earth and is central to understanding geoscience, but key questions remain about how motion of and stresses in tectonic plates are accommodated in many regions. Relationships between tectonic plates and the underlying mantle layer also remain debated, and those relationships are necessary to fully understand what actually drives plate motion on Earth. Locations like Indochina are particularly complex, influenced by a number of competing tectonic and mantle driving forces, and are thus important laboratories for better understanding how our planet functions as a dynamic, tectonic system. This study investigates the origins of recent volcanic activity and faulting in the Central Highlands of Vietnam. The goal of this research is to better understand the geologic setting of Indochina, particularly what tectonic and mantle processes drive faulting and volcanic activity. This work benefits society because it directly promotes scientific progress by investigating fundamental scientific questions about the planet and processes that shape it. The study contributes to broadening participation of underrepresented groups in science, technology, engineering and mathematics (STEM) by providing support for two early career women scientists. The project supports STEM education and training of graduate and undergraduate students, thus contributing to the development of a diverse, globally competitive workforce. The project will contribute to increased public literacy and public engagement with STEM supporting outreach events with the University of Nebraska State Museum to disseminate scientific research and educate the local community, and through a written report detailing any new findings regarding potential hazards associated with recent volcanic eruption timing and newly discovered faults. The project facilitates collaboration between several U.S. universities, as well as international collaboration between U.S. and Vietnamese scientists. In detail, this project aims to test, develop, and refine a robust, comprehensive regional model that explains the dynamic origins of faulting and volcanism in Indochina, thereby increasing understanding of tectonics and mantle dynamics in complex regimes through the combined approaches of structural geology and igneous geochemistry. The project rationale is the advancement of scientific understanding of plate boundary and microplate dynamics and lithosphere-asthenosphere coupling effects. The central hypothesis for this project states that tectonic extrusion and coupled asthenospheric flow and upwelling have driven rotation of the Southern Indochina microplate, including propagation of strike-slip and normal faulting, and produced voluminous crustal magmatism without mantle plume involvement. The specific research goals for the proposed study are: 1) to evaluate age relationships between fault movement and volcanic activity in the Central Highlands of Vietnam, 2) to gather data to define the stress field of the Central Highlands and assess whether it is consistent with an extrusion- or extension-dominated tectonic regime, and 3) to assess the evidence for mantle upwelling in the same region by identifying mantle source origins (lithosphere vs. asthenosphere) for lavas erupted over time and with geographic distribution. These objectives will be achieved through field mapping of fault orientations and kinematics; isotope dating of volcanic eruptions; and comparative major element, trace element, and radiogenic isotope measurements in basalts and mantle xenoliths. The research is expected to trigger a thorough assessment of relationships between volcanism and faulting, the origin of the tectonic stress driving faulting, and identification of local magma sources over time, leading to a reconciled tectonic model for Indochina.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.