Teagan Blaikie

Bio: Teagan Blaikie is an academic researcher from Commonwealth Scientific and Industrial Research Organisation. The author has contributed to research in topics: Volcano & Volcanic rock. The author has an hindex of 9, co-authored 23 publications receiving 261 citations. Previous affiliations of Teagan Blaikie include Monash University, Clayton campus & Monash University.

Interpreting subsurface volcanic structures using geologically constrained 3‐D gravity inversions: Examples of maar‐diatremes, Newer Volcanics Province, southeastern Australia

Abstract: We present results and a method to geophysically image the subsurface structures of maar volcanoes to better understand eruption mechanisms and risks associated with maar-forming eruptions. High-resolution ground gravity and magnetic data were acquired across several maar volcanoes within the Newer Volcanics Province of southeastern Australia, including the Ecklin maar, Red Rock Volcanic Complex, and Mount Leura Volcanic Complex. The depth and geometry of subsurface volcanic structures were determined by interpretation of gridded geophysical data and constrained 2.5-D forward and 3-D inverse modeling techniques. Bouguer gravity lows identified across the volcanic craters reflect lower density lake sediments and pyroclastic debris infilling the underlying maar-diatremes. These anomalies were reproduced during modeling by shallow coalesced diatremes. Short-wavelength positive gravity and magnetic anomalies identified within the center of the craters suggest complex internal structures. Modeling identified feeder vents, consisting of higher proportions of volcanic debris, intrusive dikes, and ponded magma. Because potential field models are nonunique, sensitivity analyses were undertaken to understand where uncertainty lies in the interpretations, and how the models may vary between the bounds of the constraints. Rather than producing a single “ideal” model, multiple models consistent with available geologic information are created using different inversion techniques. The modeling technique we present focuses on maar volcanoes, but there are wider implications for imaging the subsurface of other volcanic systems such as kimberlite pipes, scoria cones, tuff rings, and calderas.

Carbonate Replacement as the Principal Ore Formation Process in the Proterozoic McArthur River (HYC) Sediment-Hosted Zn-Pb Deposit, Australia

Abstract: The McArthur River (HYC) Zn-Pb-Ag deposit in the Carpentaria Zn belt, northern Australia, is one of the world’s largest and most studied sediment-hosted base metal deposits, owing to its lack of deformation and preservation of sedimentary and ore textures. However, the ore formation process (syngenetic vs. epigenetic) is still a subject of controversy. In this paper we focus on key characteristics of the HYC deposit that remain unexplained: preservation of sedimentary carbonate (dolomite) and its association with Zn, and the role of thallium (Tl) and manganese (Mn) distribution in the orebody. Our findings demonstrate a sequence of events during ore formation: Tl is hosted almost exclusively within euhedral pyritic overgrowths around early diagenetic pyrite; sphalerite mineralization occurred after Tl-bearing pyrite overgrowths, in association with acid dissolution (replacement) of laminated and nodular dolomite across the subbasin; and outer rims are enriched in Mn on preserved dolomite at the dissolution reaction front in contact with sphalerite. New thermodynamic fluid chemistry modeling demonstrates the metal distribution and paragenesis can be explained by acidic, oxidized ore fluids entering the pyrite-dolomite host lithology, allowing reduction and pH buffering by acid carbonate dissolution, resulting in stepwise metal deposition in an evolving fluid. We argue this represents strong evidence for epigenetic ore formation at HYC. Furthermore, the primary control on ore deposition is not synsedimentary faulting in the subbasin; rather, the chemical potential of sedimentary carbonate within reduced, sulfidic lithologies appears to be of critical importance to precipitation of sphalerite.

Monogenetic volcanism: personal views and discussion

Abstract: Monogenetic volcanism produces small-volume volcanoes with a wide range of eruptive styles, lithological features and geomorphic architectures They are classified as spatter cones, scoria (or cinder) cones, tuff rings, maars (maar–diatremes) and tuff cones based on the magma/water ratio, dominant eruption styles and their typical surface morphotypes The common interplay between internal, such as the physical–chemical characteristics of magma, and external parameters, such as groundwater flow, substrate characteristics or topography, plays an important role in creating small-volume volcanoes with diverse architectures, which can give the impression of complexity and of similarities to large-volume polygenetic volcanoes In spite of this volcanic facies complexity, we defend the term “monogenetic volcano” and highlight the term’s value, especially to express volcano morphotypes This study defines a monogenetic volcano, a volcanic edifice with a small cumulative volume (typically ≤1 km3) that has been built up by one continuous, or many discontinuous, small eruptions fed from one or multiple magma batches This definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism

Monogenetic Basaltic Volcanoes: Genetic Classification, Growth, Geomorphology and Degradation

Abstract: Plate motion and associated tectonics explain the location of magmatic systems along plate boundaries [1], however, they cannot give satisfactory explanations of the origin of intra‐ plate volcanism. Intraplate magmatism such as that which created the Hawaiian Islands (Figure 1, hereafter for the location of geographical places the reader is referred to Figure 1) far from plate boundaries is conventionally explained as a result of a large, deep-sourced, mantle-plume [2-4]. Less volumetric magmatic-systems also occur far from plate margins in typical intraplate settings with no evidence of a mantle-plume [5-7]. Intraplate volcanic sys‐ tems are characterized by small-volume volcanoes with dispersed magmatic plumbing sys‐ tems that erupt predominantly basaltic magmas [8-10] derived usually from the mantle with just sufficient residence time in the crust to allow minor fractional crystallization or wallrock assimilation to occur [e.g. 11]. However, there are some examples for monogenetic eruptions that have been fed by crustal contaminated or stalled magma from possible shal‐ lower depths [12-19]. The volumetric dimensions of such magmatic systems are often com‐ parable with other, potentially smaller, focused magmatic systems feeding polygenetic volcanoes [20-21]. These volcanic fields occur in every known tectonic setting [1, 10, 22-28] and also on other planetary bodies such as Mars [29-33]. Due to the abundance of monogen‐ etic volcanic fields in every tectonic environment, this form of volcanism represents a local‐ ized, unpredictable volcanic hazard to the increasing human populations of cities located close to these volcanic fields such as Auckland in New Zealand [34-35] or Mexico City in Mexico [36-37].

Rapid, semi-automatic fracture and contact mapping for point clouds, images and geophysical data

Abstract: . The advent of large digital datasets from unmanned aerial vehicle (UAV) and satellite platforms now challenges our ability to extract information across multiple scales in a timely manner, often meaning that the full value of the data is not realised. Here we adapt a least-cost-path solver and specially tailored cost functions to rapidly interpolate structural features between manually defined control points in point cloud and raster datasets. We implement the method in the geographic information system QGIS and the point cloud and mesh processing software CloudCompare. Using these implementations, the method can be applied to a variety of three-dimensional (3-D) and two-dimensional (2-D) datasets, including high-resolution aerial imagery, digital outcrop models, digital elevation models (DEMs) and geophysical grids. We demonstrate the algorithm with four diverse applications in which we extract (1) joint and contact patterns in high-resolution orthophotographs, (2) fracture patterns in a dense 3-D point cloud, (3) earthquake surface ruptures of the Greendale Fault associated with the Mw7.1 Darfield earthquake (New Zealand) from high-resolution light detection and ranging (lidar) data, and (4) oceanic fracture zones from bathymetric data of the North Atlantic. The approach improves the consistency of the interpretation process while retaining expert guidance and achieves significant improvements (35–65 %) in digitisation time compared to traditional methods. Furthermore, it opens up new possibilities for data synthesis and can quantify the agreement between datasets and an interpretation.