Friday, 1 September 2017

My first field season: rocks, bubbles and low-cost technologies... by Jo Miles

Hi, my name is Jo and I began my PhD at the British Geological Survey and School of Earth Sciences, University of Bristol in September 2016. My research aims to further our understanding of preservation potential of mineralising systems located in the shallow submarine environment (<100 m). In this blog, I will share with you an aspect of my field season on the Greek island of Milos from this summer.

Dynamic submarine processes can help or hinder preservation, potentially resulting in either a bonanza or a failed ore deposit. Therefore, it is important to understand the dynamic processes and the preservation potential, to determine whether the shallow submarine environment is prospective for future mineral exploration and exploitation. The island of Milos, located in the Cyclades, Greece, provides an ideal on-land laboratory having emerged 1.4 million years ago. The island’s topography reflects the paleo-seafloor, and allows us to directly study and sample mineralised and hydrothermally altered paleosurfaces that formed in the shallow submarine environment.

I have recently returned from my field season where we drove approx. 2000 km (a similar distance from Nottingham to Rome) around winding roads of a 13 by 23 km island over a period of five weeks. The first challenge of the trip included learning to adapt to a Jimny Jeep that was not happy to be in first gear or reverse.

I was joined in the field by my main supervisor, Jon Naden, for a handful of days prior to the rest of the party. This was a great opportunity to visit mineralised and altered outcrops, which I had only read about in literature. This was vital in helping my understanding of hydrothermal systems and begin to visualise how my PhD project will pan out. More students from the University of Bristol and Ottawa shortly joined us for a week, alongside researchers from the University of Athens - the island was certainly busy.  

One aspect I am keen to research involves how mineralisation differs from the western ancient hydrothermal system in comparison to the active system located in the east. In order to observe the active submarine environment and witness the potential ore-forming environment, we collaborated with PhD students Jonathan Teague and Dean Connor from the School of Physics, University of Bristol, whom have experience building and deploying low-cost remotely operated underwater vehicles (ROVs) and unmanned aerial vehicles (i.e. drones; UAVs). With knowledge from the University of Athens, we deployed a BlueROV2, equipped with a GoPro Hero 5 off the southern coastline of Milos Island. This was entirely controlled via a laptop and Xbox 360 controller onshore, which allowed the ROV to move a maximum distance of 100 m offshore.

1. Setting up the office for venting exploration.


2. The ROV in action.

The aim of this pilot study allowed us to decipher the location of active venting fields – were they randomly dispersed or was there a structural or permeability control? Knowing the NW-SE horst-graben structural control on the island, we inferred this lineament out to the southern coastline. Alongside rotten-egg smelling fumaroles located in the cliff faces, we were able to decipher two likely venting locations to deploy the ROV. The rotten-egg odour is indicative of sulfur in the form of H2S: a gas coming directly from an underlying magma chamber.

Three days were spent identifying and undertaking reconnaissance mapping within an area of 1 km2 where we successfully found venting sites. The team from the School of Physics, University of Bristol undertook a Structure-from-Motion (SfM) photogrammetry program, to produce high-resolution 3D topographic reconstructions of the seafloor. Thousands of images taken with the GoPro Hero 5 contribute to a handful of bathometry models. Despite the huge volume of data, this is a much cheaper option.

3. Locating bubbles with the ROV via laptop control.



Since the vents are relatively shallow (<7 m), we returned to the area during the evening to snorkel which was the perfect treat to end an incredibly hot day hiking to outcrops. Luckily, the sun was still shining, which meant the visibility conditions underwater were perfect. Often, you could use your sense of smell to locate the venting fields. Patches where bubbles were rising often resembled the temperature of a hot bath (approx. 60oC). We avoided swimming directly over these areas due to the corrosive nature of the escaping gases.

Unlike the ROV, we had to be patient with the weather in order to fly the drone. Rain and strong winds often set us behind schedule. For safety purposes, a team of four was needed: two would secure the location to prevent the public from being close to the flight area, whilst the pilot and computer-operator would liaise to ensure the drone was following the pre-planned flight lines. We chose terrain-challenging locations to create photogrammetry models, which would enable remote fieldwork with a 10 cm resolution.  When discussing my research and its implications back home, it will now be much easier for the audience to follow my thinking if I display the landscape and rocks to them, as if they were on fieldwork with me.

4. UAV Pilot undertaking a test survey.
This was a great opportunity to be part of a student-led research project with a diverse range of skillsets, with the full backing of our supervisors. We are currently writing our first paper and eager to develop the project further and revisit the venting site next spring.

My supervisory team consists of Jon Naden (BGS), Frances Cooper and Brian Tattitch (University of Bristol), Stephen Grebby (University of Nottingham), Dan Smith (University of Leicester) and Graham Ferrier (University of Hull).

Jo can be found on Twitter using the handle @geologyjomiles

Photography credit:  Jonathan Teague, jt16874@bristol.ac.uk



No comments: