Wednesday
19th October
Geology and Architecture in South Scotland
Professor
James Floyd
Heriot-Watt University
Despite the obvious dominance of
Lower Palaeozoic rocks on the geological map of south Scotland and indeed in many
of the older rural structures, there are many other interesting and attractive
rock types which have been utilised in the built environment.
Among the
more obvious are the red sandstones of the Permian basins at Dumfries and Lochmaben,
the granites of Galloway, and the pale sandstones and minor igneous rocks of the
Border counties, all of which are of relatively restricted occurrence. This commonly
results in the local geology being so intimately reflected in the vernacular architecture
that a geologist can almost locate him/herself within the region merely by studying
the building stones which have been used, particularly in the older structures.
The various building stones available and quarried in South Scotland will
be described and their architectural use illustrated using examples from within
the region and beyond.
Wednesday 2nd November
Coral Aragonite:
Rosetta Stone of Past Climates or Another Useless Rock?
Dr Adrian Finch
St
Andrews University
Studies of modern corals show that the chemistry of
the aragonite skeleton deposited at any time encodes local environment. Thus,
as sea surface temperature and/or ocean water chemistry change, these become expressed
as variations in the isotopic ratios or element compositions in the skeleton.
The flip side is that, in principal, we can use the chemistry of fossil coral
skeletons to reconstruct past marine environments, long before instrumental records
of climate were kept. Such studies are crucial in our attempts to understand how
sea conditions fluctuated into the historical, prehistorical and geological past.
Furthermore as analytical instrumentation has developed, we have been able to
measure progressively smaller and smaller amounts of skeleton (and therefore to
arrive at high-resolution (monthly-weekly) climate information) and perform types
of experiment unimagined even thirty years ago. But instead of elucidating climate
change, such studies have made us aware of the extraordinary complexity of corals.
Corals skeletons are intergrowths of nm-sized mineral and organic components that
can be compared with modern synthetic ‘nanocomposite’ materials. They
have a complex skeletal architecture with micron-scale compositional and isotopic
heterogeneity, and a mineralogy which breaks the laws of thermodynamics. Far from
being passive encoders of past climates, corals are fascinating organisms that
challenge our understanding of what biominerals are and how they form.
Mineral
inclusions in diamonds track the evolution of a subducted slab beneath Gondwanaland
in the Mesozoic era
Professor Ben Harte
Most natural diamonds come
from depths of 150 to 200 kms, but a small group have mineral inclusions formed
at depths of ca 250 to 800 kms. The diamonds containing these inclusions often
have carbon isotope ratios indicating formation from material derived from the
Earth's crust.
A model will be presented to suggest the inclusions are formed
from subducted oceanic lithosphere, and that their depths of formation are largely
constrained by the depths of zones of dehydration in the subducting slab. For
the inclusions from Juina, Brazil, the inclusions appear to be derived from a
slab of the Prot-Pacific Ocean, subducted beneath Gondwanaland during the Mesozoic
era.
Continental collision and how the crust deforms:
early
ideas from the Scottish Highlands to active deformation in the Himalayas
Rob
Butler, University of Aberdeen
More than a century ago the NW Highlands
of Scotland provided the inspiration for ideas of how rocks become deformed during
mountain building – especially through the repetition of rock units by lateral
displacement. In this way the crust is both thickened vertically and shortened
horizontally. These ideas of thrust tectonics were far more fully developed in
the 1970s and 80s, where they were used to interpret mountain building around
the world. But are we seeing enough of the whole story? Are these concepts enough
on their own to provide even a large-scale description of how continents deform
during plate collision processes?
The issue comes down to recognising and
understanding how deformation localises in rocks – a fundamental task for
structural geologists. As a community we are fixated (the speaker included!) by
localised deformation, especially faults and their ductile equivalent in the deeper
crust – shear zones. But there is also much more widely distributed deformation.
This may be much less strongly developed in any one place but because it is widely
distributed, can accommodate more deformation in total. And it has generally been
underreported. This is now changing. With geodetic surveys and GPS campaigns that
measure active deformation, allied to novel geophysical approaches, it is clear
that the continents on a large scale deform in more complex ways. And these may
cause us to look again at the NW Highlands, as elsewhere, to see what we’ve
been missing!
Finding gold - from the Solomon
Islands to Scotland
Gawen Jenkin (University of Leicester)
Gold
is mostly useless in practical terms – 90% or so being used for jewellery
or bullion. In addition it is a very rare metal, but despite (or because of) this
it is sought after and highly valued by the human race and now forms a key component
in the world economy, generating vast amounts of wealth. Here I show how we are
carrying out research to help locate new gold deposits in “frontier”
areas with little or no previously known mineralisation.
The Solomon Islands
fall within the SW Pacific arcs famed for a number of giant gold deposits, but
the highly vegetated terrain is challenging for exploration. The active geothermal
system on Savo volcano allows us to examine the topmost part of a potentially
mineralising system, and shows that travertine deposits formed at hot springs
could present a new marker for gold mineralising systems in the region.
Cononish
mine at Tyndrum is now under development – Scotland’s first gold mine
in 500 years. This is set to have a huge positive impact on the economic prosperity
of the area, and here we are working with Scotgold to see if we can help locate
the next gold mine and so sustain the economic benefits beyond the lifetime of
Cononish. We are working to understand the hydrothermal system that formed Cononish
and other gold occurrences. This in turn will help develop an exploration model
that can be applied to help discriminate the more promising prospects and make
exploration more efficient. Whilst the gold veins almost certainly relate to an
intrusion at depth driving fluid flow, we are increasingly finding that the source
of the sulphur is from the Dalradian metasediments. This begs the question as
to where the gold is coming from and therefore what part of the hydrothermal system
it might be concentrated in.
Mercury - new views
of the Sun's innermost planet
David Rothery (Open University)
Mercury
is the smallest terrestrial planet and the one closest to the Sun. It has a high
density and a self-generated magnetic dipole field, both symptomatic of a large
iron core. Thrust faults evidenced by lobate scarps attest to an episode of global
contraction.
From the views glimpsed during MESSENGER’s 2008 and 2009
flybys it was apparent that vast tracts of the planet are covered by lava flows.
Now MESSENGER is in orbit we can see details of volcanic vents and lava channels
and begin to determine the surface composition. For me the most intriguing aspects
are that Mercury is richer in sulphur and potassium than it has any right to be,
so close to the Sun, and the curious hollowed terrain where steep-sided, flat
bottomed pits a few tens of metres deep and up to a few kilometres across show
that parts of the surface have wasted away, and presumably by being turned to
vapour. Sulfur would be the obvious candidate, except that the colour associated
with most of these pits is blue rather than yellow. MESSENGER probably wont be
capable of measuring the composition of features this small, so this is something
for the European and Japanese Space Agencies’ BepiColombo mission to get
its teeth into, when it arrives in 2021.
Maybe Mercury formed much further
away from the Sun than its current orbit (nearly three times closer to the Sun
than the Earth) and migrated inwards later. On the other hand, Mercury has a very
large iron-rich core, so maybe there was something about the catastrophic giant
collision responsible for stripping away most of Mercury’s original rocky
mantle that was able to scavenge sulfur and potassium from the core and concentrate
it upwards as the new crust formed.
