Liannie C. Velázquez Santana
Research
Origin & Evolution of Arc Magmas
I am interested in exploring the origin and evolution of arc magmas from source to surface. Within this context, I combine petrology, geochemistry, and geochronology to understand the driving processes leading to the eruption and/or emplacement of magmas.
Tracing Volatile Cycling at Continental Arcs
At UT Austin, I am exploring the volatile budget of the continental crust and arc magmatic systems to understand at what stage in the evolution of these systems volatile elements are added to, or removed from, the surface inventory.
More info coming soon!
Amphibole Crystal Cargoes:
What is the role of amphibole in magmatic systems?
This project examines numerous amphibole populations within andesitic lavas and entrained rare hornblendite cumulates at the Pleistocene-aged Quillacas monogenetic volcanic center on the Eastern Altiplano, Bolivia. While amphibole is often referred to as a “cryptic” fractionating phase, I identify multiple amphibole populations within hornblendite cumulates and the host andesites using a multifaceted approach (textures, mineralogy, chemistry, and geothermometry). The amphibole crystal cargoes provide a comprehensive evaluation of the origin of amphibole, magma ascent pathways, and the crustal architecture at the Quillacas magmatic system. More importantly, this dataset advances our understanding of the role of amphibole in the evolution of arc magmatic systems.
Bolivian Hornblendite Cumulates:
How and where is water stored in a magmatic system?
This research sought to improve our understanding of water storage in magmatic systems using hornblendite, which consists mainly of the OH-bearing mineral hornblende. The hornblendites were erupted ~2 million years ago from the Quillacas volcano located in the Eastern Central Andes. Through mineralogical, textural, chemical, and isotopic analyses, I found that the hornblendites crystallized at a depth of 50-55 km (mid-lower crust) as a cumulate layer within the magmatic system. These findings confirmed that a rarely erupted cumulate reservoir of OH-bearing minerals exists at depth with the capability to trap and filter considerable amounts of dissolved water in the magmatic system (Velázquez Santana et al., Lithos, 2020). Moreover, as water vapor is an important volatile phase in magmas, the presence of a water reservoir at depth has implications for the explosivity of volcanic eruptions.
Bolivian Crustal Xenoliths:
How can we leverage the crustal components of a magmatic system to better understand how active tectonic margins evolve over time?
To advance our understanding of the timescales of crustal evolution, accretion, and tectonomagmatism associated with the establishment of the proto-Andean margin, I conducted a study of a suite of igneous and metamorphic crustal xenoliths. The crustal xenoliths originated from two back-arc monogenetic volcanic centers located on the Bolivian Altiplano. Therefore, these samples provide a rare vertical cross-section of the continental crust of this region. Through geochronological analyses of zircon (U-Pb-Hf) via LA-ICP-MS, I found significant age peaks in the Paleoproterozoic, Mesoproterozoic, and Ordovician- late Neoproterozoic periods consistent with the Andean zircon record. The zircon record from the crustal xenoliths also records evidence of more than 3 billion years of tectonomagmatic events within the Central Andean crust, including supercontinent events associated with Nuna, Rodinia, Gondwana. This work is currently under review in GSA Bulletin.
Sulfide Inclusions:
Where does sulfur originate in magmatic systems and how does it travel from source to surface?
Sulfur dioxide (SO2) is a major volatile component in magmas and one of the main drivers of volcanic eruptions. Currently, I am conducting a mineralogical, chemical, and isotopic investigation of sulfide mineral inclusions in the previously studied hornblendites. With this research, I hope to answer (1) how much S is initially available to the magma from a primary source (i.e., mantle) and (2) how is S subsequently mobilized and/or mineralized throughout the magmatic system? To address these questions, I have first conducted a mineralogical characterization of the sulfides using the SEM to semi-quantify the elemental distribution of the sulfides. I am now working on collecting electron microprobe and secondary ion mass spectrometry (SIMS) data to chemically fingerprint the sulfides’ primary origin source. This work will help constrain the primary magmatic S budget of active continental volcanic zones by analyzing the S isotopes of sulfide inclusions in hornblendites.
