Earth Science Seminars - Department of Earth & Environmental ...

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Earth Science Seminars

Schedule

201
1
-
201
2




6 October 2011 at 13:00

Dr Warren Pratt
(Specialized Geological Mapping)

Epithermal vein gold deposits in South America


Warren Pratt (BSc Geology Hull, 1986; PhD Structural Geology, University of Wa
les,
1990) has a strong mapping background and a decade of British Geological Survey
field experience and training. In the first half of the 1990s he worked mainly on
volcanic rocks in Wales, on engineering geology projects, and in the roofing slate
indust
ry. In 1994 he won the President's Award of the Geological Society of London for
detailed thematic mapping. Apart from the UK, he has extensive world
-
wide field
experience in a great variety of geological terrains. Dr Pratt has a track record of
generating

Au/Cu targets in under
-
explored areas, for example, the Cañicapa high
sulfidation Au project, discovered during a World Bank minerals program in Ecuador.
Over the last few years, presentations have been made at metals
-

and petroleum
-
related international
conferences in France, Perú and Finland.


6 October 2011 at 17:00

Dr Warren Pratt
(Specialized Geological Mapping)

Adventures in Gold Exploration


Warren (details above) delivered a second lecture aimed at our undergraduate
students in order to discuss th
e ups and downs of being a field geologist.


20 October 2011 at 16:15

Professor Rudy Slingerland

(Penn State)
part of

World Seminar Series

River deltas as self
-
organised morphodynamic systems


Rudy Slingerland ran a two day workshop co
-
sponsored by MASTS
and SAGES on
mathematical modelling aimed at postgraduates who are funded by, or affiliated to,
these two pooling communities. Rudy has vast experience in modelling both
"terrestrial" and marine Earth systems, particularly in fluid flow and sediment
transp
ort over short and geological timescales, as well as a large range of spatial
scales. He is a member of the Community Surface Dynamics Modeling System (based at
University of Colorado, Boulder) which provides a framework to enhance and support


modelling of

Earth systems.


Rudy presented a public seminar on his work after the workshop.


Tuesday, 1 November 2011 at 14:00

Iain Stewart

(geologist and TV presenter)

Seismic Faults and Sacred Sanctuaries


Iain
gave a
talk to the RSGS in Aberdeen and Dundee

a week
after coming here to give
his impromptu lecture
.
I
ain is co
-
leader of a project investigating earthquake
archaeology in the Aegean region (IGCP 567 project) and this will be the focus of his
talk.


Iain was recently presenter on
Men of Rock
,
Making Scotlan
d's Landscape
,
How Earth
Made Us
, and the
Power of the Planet
. The BBC have just approved a new TV series that
Iain will be presenting in the next year called "The Story of the Continents".


Thursday, 3 November 2011


Christopher Spencer

(University of St
Andrews

PhD student
)

Depositional Provenance of the Himalayan Metamorphic Core of Garhwal Region, India:
Constrained by U
-
Pb and Hf isotopes in zircons


Chris is a PhD student here in the Department, and he

gave us
an overview of the
research he pursued fo
r his Master's degree.


Thursday, 24 November 2011

Mariël Reitsma

(Université de Genève)

Late Palaeozoic
-
Early Mesozoic back
-
arc basins on the western Gondwana margin:
Distinguishing periods of crustal growth and recycling in south
-
east Peru


Mariël is a
student just completing her PhD in Switzerland. She works on the Late
Palaeozoic
-

Early Mesozoic granitoids and associated sediments of the Eastern
Cordillera of southern Peru. One of her outstanding challenges is to relate growth and
recycling of the con
tinental crust to the geodynamic setting under which sedimentary
basins and granitoids formed. A back
-
arc setting that varied between compressional
and extensional seems to best fit whole rock geochemistry and laser ablation ICP
-
MS
U
-
Pb dating of magmatic
and detrital zircons. Hf
-
isotopes on magmatic zircons indicate
mostly recycling of the crust with only a few pulses of juvenile addition. Additionally,
the interpretation of the Eastern Cordilleran granitoids as emplaced in a back
-
arc
setting implies that
the contemporaneous arcs have been removed by subduction


erosion.


Monday, 6 February 2012

An overview of Move software and the academic software initiative (ASI)
.
This
was followed by a practical demo in the afternoon.


What structural modelling and val
idation is about
-

the software Move is really
just a
tool we use to help us.


This talk gave a
quick introduction to digital field mapping

and included a p
ractical
exercise to demonstrate project set
-
up and digitisation tools in FieldMove using an
exa
mpl
e data set from loch Eriboll. There was also a
demonstration to show tools
available for section construction and model building in Move
;
students
were
encouraged to use
"construct horizon from template" to help visualise structure from
dips p
rojected onto

a section plane.


Advanced, flexible structural modelling software: The Move application provides a
seamless integrated environment for 2d and 3d geological model building, editing and
structural analysis. A diverse range of data formats can be imported
and exported as
well as digital elevation models (DEMs), GIS data and coordinate systems. Move has
been designed by geologists for geologists
-

for importing and analysing your data
before interogating it. The linked views function allows simultaneous edit
ing on one
model while looking at it in map, section and 3d view while the extensive model
building tools provide a unique, flexible and logical working environment.


Thursday, 1 March 2012

Dr John A Stevenson
(University of Edinburgh)


Despite its moderat
e size, the April 2010 explosive eruption of Eyjafjallajökull
highlighted how Icelandic volcanism can affect the UK. Ash from previous eruptions in
Iceland, some of which were many times larger, is preserved in soils across Scotland as
microtephra layers.
My project seeks to understand the eruptive and transportation
processes by which microtephra layers form and to evaluate the hazard to the UK
presented by the eruptions that produce them (e.g. airport closures, potential fluorine
poisoning of livestock).


Tephra from both the Eyjafjallajökull 2010 and Grímsvötn 2011 eruptions fell in the
UK. It was found in rainwater, on sticky
-
tape samples and detected by air quality
monitoring equipment. Results from the Grímsvötn eruption show good agreement
with predic
tions from the NAME dispersion model. A long season of fieldwork in 2012


will collect the data required to reconstruct the characteristics of the large, prehistoric
Hekla 4 eruption, which will in turn allow prediction of likely outcomes should there
be a
similar eruption in the future.



Thursday, 8 March 2012

Richard Taylor

(PhD student, University of St Andrews)

Potential new applications for fluorescence spectroscopy in Mineralogy


rt48c microcline'Fluorescence and or luminescence can be
seen from rott
ing wood, certain insects, mushrooms, fish,
microorganisms, sea algae and many examples from the
mineral kingdom and has been known since ancient times. This
interesting and initially mysterious phenomenon attracted the
attention of many scientist for the
last four centuries' (Vij,
1998).


A discussion of how the latest technologies and techniques
may be applied to extend the potential uses of fluorescence spectroscopy in
mineralogy. (Image shows a two photon FLIM image of a microcline feldspar).


Vij, D.R.
, 1998. Luminescence of solids in: Vij, D.R. (Ed.). New York ; London : Plenum
Press, c1998., New York ; London.


Friday, 9 March 2012

Andrew Mackenzie

(BHP Billiton)

Life in Geosciences


Alumnus Dr
Andrew Mackenzie BSc (Geology), PhD (Chemistry), joined B
HP Billiton in
November 2008 in his current position as Chief Executive Non
-
Ferrous. His prior
career included time with Rio Tinto, where he was Chief Executive of Diamonds and
Minerals, and with BP, where he held a number of senior roles, including Group
Vice
President for Technology and Engineering, and Group Vice President for Chemicals. He
is a non
-
executive Director of Centrica plc.


Friday, 9 March 2012

Andrew Mackenzie

(BHP Billiton)

Mineral deposits and their global strategic supply


Andrew's second

talk of the afternoon w
as followed by a reception
, hosted by GeolSoc,


the student
-
led geological association.


Friday, 16 March 2012

FRESH (FRontline Earth Science researcH)

@ St Andrews

The Pulse of Earth Processes


This half
-
day symposium cover
ed

a ran
ge of topics related to
The Pulse of the Earth
Processes
, including metamorphism, magmatism and earthquakes. Our keynote
presenter
was

Professor Ethan Baxter of the University of Boston and Mineralogical
Society of America Distinguished Lecturer 2011
-
2012
(
Evidence for Brief Pulses of
Metamorphism
). Other invited speakers include
d

Randall Parrish (NIGL and
Mineralogical Society UK Distinguished Lecturer 2011
-
2012), Dan Condon (NIGL), Tim
Dempster (Glasgow), Simon Harley (Edinburgh), Kathryn Goodenough (BGS)
, Fin
Stuart (SUERC) and Ruth Robinson and Tim Raub of St Andrews.


Armed with a PhD from the University of California at Berkeley, Prof Ethan Baxter is
currently Associate Professor of Earth Sciences at the University of Boston. His
research involves appl
ications of isotope geochemistry, geochronology, and petrology
to understand and quantify the geological processes affecting the evolution of the
Earth's crust as well as its interactions with the mantle and surface. Ethan's interests
include the rate and
duration of metamorphic and tectonic processes, H2O and CO2
fluxes within the evolving crust, and the refinement of geochronologic methods (e.g.
Sm/Nd, Rb/Sr, Ar/Ar) to better understand the history of the Earth. With his students,
Prof. Baxter's research
includes lab work in the BU TIMS Facility and field work (e.g.
New England, Austria, Greece). He is a member of the University of Boston's Climate
and Earth History research group, Geochemistry research group and the Solid Earth
and Tectonics research grou
p.



This w
as
Ethan
’s only presentation to a UK institution on his whirlwind tour.




FRESH (FRontline Earth Science researcH) @ St Andrews

The Pulse of Earth Processes

13:00
-
17:30, Friday 16 March 2012

Irvine Lecture Theatre, Irvine Building









Schedu
le:



12.00
-
13.00

Arrival in St Andrews: informal lunch in Forbes (refreshments not provided)

13.00
-
13.05

Irvine Lecture Theatre: Welcome to the event

13.05
-
13.25

D Condon

The Times They Are a
-
Changin‘: an update on high
-
accuracy (U
-
Pb)
geochronology

13
.25
-
13.45

K Goodenough

Post
-
collisional granitoids: recording the final pulses of movement in the Pan
-
African and Caledonian orogenic belts

13.45
-
14.05

F Stuart

Low temperature thermochronology: current state and future prospects

14.05
-
14.25

R Parrish

Ju
st how fast can rocks get exhumed by erosion? The example of Namche
Barwa, eastern Himalaya and its record from zircon and rutile thermochronology

14.25
-
14.45

R Robinson

The detrital mineral record of Cenozoic deposits of the Central Myanmar Basin,
Burma
: implications for the evolution of the eastern Himalayan syntaxis

14.45
-
15.05

T Raub

Interrogating

rocks at annual to decadal timescales in the Precambrian: novel
algorithms and exceptional samples

15.10
-
15.40

Refreshment break in Forbes (and poster ses
sion)

15.40
-
16.00

S Harley

Zircon behaviour in hot Orogens

16.00
-
16.20

T Dempster

Zircon: the leaky bucket of Earth history and its use in palaeohydrology

16.20
-
17.20

E Baxter

Making a Long Story Short: Evidence for Brief Pulses of Metamorphism

17.20
-
1
7.30

Closing remarks from the Head of Department, Prof Peter Cawood

Reception in Forbes (and poster session)




FRESH abstracts

(in alphabetical order of presenter):

Making a long story short: evidence for brief pulses of metamorphism

Ethan F. Baxter (Bo
ston University, USA)

Email:
efb@bu.edu








The Times They Are a
-
Changin‘: a
n update on high
-
accuracy (U
-
Pb) geochronology

Daniel J. Condon (
NERC Isotope Geosciences Laboratory, BGS, UK)

Email:
dcondon@bgs.ac.uk


In the hundred years since Frederick Soddy discovered isotopes and Arthur Holmes published the first U
-
Pb
mineral ages, methods for the precise and accurate determination of mineral and rock ages have continually
evolve
d. We are now at a point where radio
-
isotopic dating of minerals underpins our understanding of the
evolution of the Earth System, from evolution of the continents and the biosphere to more recent phenomenon
such as sea
-
level and climate change. Increasi
ngly, very high
-
precision (<0.05%) dating is employed to elucidate
rates of change, and the exact temporal relationship of records of geological records of related events (e.g.,
changes in fossil diversity vs. eruption/emplacement of large igneous province
s). However improvements in
analytical precision have largely outpaced accuracy to the point where the uncertainty in the former typically
exceeds the latter, such that resolving power is often greatly reduced when integrating data sets. This talk with
f
ocus on the accuracy of U
-
daughter geochronology (U
-
Pb and U
-
Th) and recent efforts that have been made to
target key sources of uncertainty. This is exemplified by recent work questioning (and answering) long held
assumptions about the invariant nature o
f the isotopic composition of uranium.


Key reference
: Hiess, J., Condon, D. J., McLean, N., and Noble, S. R., accepted, for publication,
238
U/
235
U systematics
in terrestrial U
-
bearing minerals: Science


Zircon: the leaky bucket of Earth history and
its use in palaeohydrology

Tim Dempster (University of Glasgow, UK)

Email:
Tim.Dempster@glasgow.ac.uk


Radiation
-
damaged zircon is highly reactive and prone to alteration and dissolution during diagenesis a
nd low
-
grade metamorphism. Such processes are controlled by the age and U
-
content of the zircon but also on the
availability of crustal fluids. This metamorphic response also promotes new growth either in the form of
recrystallised areas in old detrital gr
ains, overgrowths on their outer surface or new microzircon growth in the
matrix.


Zircon in greenschist facies schists from the Late Proterozoic Dalradian metasedimentary rocks of southwestern
Scotland is characterized by two types: a) large detrital grai
ns and b) small (<9 μm
2
) euhedral metamorphic
grains. Mapping of >1800 individual zircon grains within part of a polished thin section reveals that detrital
zircon is strongly concentrated in the psammite beds and shows ubiquitous evidence of dissolution a
nd reaction
with metamorphic fluids. Virtually no “unaltered” detrital zircon is present. The metamorphic microzircon,
which also form as overgrowths around detrital grains, form 65% of individual zircon grains and >17 vol% of all
the zircon in the pelites
. The mapped distribution of the microzircon within a single fold hinge reveals that they
are clustered within parts of the pelite beds and form in aligned arrays that cut across the trend of the beds. The
combination of textural characteristics with the s
patial distribution show the growth of microzircon occurred in
a complex crack network that developed after folding reflecting precipitation from metamorphic fluids. Ponding
Mineralogical Society of America Distinguished Lecturer 2011
-
2012



of these fluids occurs within the psammites in an antiform structure and is respon
sible for an enhanced
metamorphic response in the zircons in the fold hinge with a 42% increase in the amount of microzircon in
comparison to the limbs. The study shows that a) zircon can be successfully used to map detailed fluid pathways
in metamorphic r
ocks; b) metamorphic and altered zircon dominates such rocks. The common alteration of
zircon at low temperatures casts doubt on its ability of zircon to reliably record ancient events in Earth history.
However this drawback is more than countered by the p
otential to map fluid pathways through rocks.


Key reference:

Dempster, T. J., Hay, D. C., and Bluck, B. J., 2004, Zircon growth in slate: Geology, v. 32, no. 3, p. 221
-
224.


Post
-
collisional granitoids: recording the final pulses of movement in the Pan
-
Af
rican and Caledonian
orogenic belts

Kathryn M. Goodenough (BGS Edinburgh, UK)

Email:
kmgo@bgs.ac.uk


Many of the world’s major orogenic belts are ‘stitched’ by granitoid plutons that were emplaced during or after
the m
ain collisional event, but before tectonic movement had ceased. Dating of these plutons can provide an
important key to the timing and rates of tectonic processes in these belts. In the Caledonian belt of Northwest
Scotland, we have mapped syn
-

to post
-
tec
tonic plutons in great detail and identified the relationship between
movement on thrusts and pluton emplacement in a small field area. High precision ID
-
TIMS dating of zircons
from these plutons has allowed us to accurately constrain the timing of Caledon
ian collision in this region. By
contrast, in the Pan
-
African orogenic belts such plutons cover much larger areas and mapping has been much
less detailed; dating programmes have been of a more reconnaissance
-
type and so have used less precise
techniques. H
owever, extensive dating work carried out by the BGS and collaborators across Africa in the last
decade has allowed us to understand the timing and rates of collisional processes on an orogen
-
wide scale. This
talk will provide examples of the two approache
s.


Key reference
: Goodenough, K. M., Millar, I., Strachan, R. A., Krabbendam, M., and Evans, J. A., 2011, Timing of
regional deformation and development of the Moine Thrust Zone in the Scottish Caledonides: constraints from
the U
-
Pb geochronology of alk
aline intrusions: Journal of the Geological Society, v. 168, no. 1, p. 99
-
113.


Zircon behaviour in hot Orogens

Simon Harley (University of Edinburgh, UK)

Email:
Simon.Harley@ed.ac.uk


Recent thermomechanical m
odelling of large hot orogens indicates that the deep crust trapped beneath an
orogenic plateau has the potential to record very long
-
lived high
-
temperature metamorphism and deformation,
including UHT metamorphism, on timescales of 30 Ma to even 100 Ma. Ev
idence for such long
-
lived deep crust
residency at > 900C is elusive, however, because most thermochronometers close at lower temperatures. As a
consequence the definition of HT/UHT event histories in the deep interiors of hot orogens requires the use of
m
ineral chronometers that are responsive to reactions occurring in the rocks and which have very high
diffusional closure temperatures.

Zircon is the most important of a small number of accessory minerals that generally meet these criteria,
especially as
it may also provide information on the temperatures of its formation (Ti in zircon thermometry)
and the context of its formation or modification in relation to major mineral phases such as garnet (REE
partitioning signatures, O
-
isotope equilibrium). In ord
er to use such information and interpret zircon age data it
is critical to understand the processes that govern zircon behaviour in HT/UHT environments. These include:
ostwald ripening in melt
-
bearing domains; crystallisation from partial melts locally and

transiently saturated in
Zr; coupled dissolution
-
precipitation in the presence of both melts and fluids, often driven by mineral and
mineral
-
melt
-
fluid reactions (e.g. garnet corona formation; fluid expulsion from late
-
stage melts), and; zircon
precipitat
ion that is decoupled from in
-
situ dissolution (e.g. Zr exsolution from high
-
T rutile). Two examples of
the insights provided by this integrated ‘zirconology’ are presented here.



The first example concerns the age and duration of UHT (
1050
-
1120

C; 7
-
11 kb
ar)
in the Archaean
Napier
Complex, Antarctica. In
-
situ U
-
Pb, REE and Ti microanalysis of anatectic zircons from UHT leucosomes
demonstrates prolonged UHT conditions: from 2586±8 Ma at T > 914±28°C (Ti: 47±10 ppm) in one leucosome,
through 2557±5 Ma for zi
rcon overgrowths in a second leucosome at T> 945±20°C (Ti: 59±9 ppm), and to 2510
-
2480 Ma in other leucosomes crystallised at >850°C. Irregularly zoned metamorphic zircon, formed through
coupled dissolution
-
reprecipitation accompanying garnet formation in
reaction textures in pelites, records post
-
UHT cooling through 860
-
790°C at 2510
-
2430 Ma. These zircon data indicate that 2590 Ma UHT metamorphism
in the Napier Complex was long lived, with temperatures remaining >950°C for at least 30 Ma, and followed by
slow cooling over a time interval of 70
-
100 Ma at 2°C/Ma. Coupled with published Sm
-
Nd (2380
-
2360 Ma) and
Lu
-
Hf (2408±48 Ma) mineral isochrons, the results indicate prolonged deep
-
crustal residence for at least 200 Ma
after initial UHT in this, the ultimat
e UHT metamorphic belt.

The second example concerns the duration and scales of melting under HT/UHT conditions (860
-
940°C) in the
Trivandrum Block of the ca. 550
-
520 Ma Kerala Khondalite Belt, India. In
-
situ U
-
Pb and REE microanalysis of
zircons, complemen
ted by garnet and monazite chemistry, demonstrates initial crystallisation of skeletal
-
planar
zoned zircons, with hollow tubular core regions in which micro
-

and nano
-
granite former melt inclusions are
now preserved, under initially open
-
system conditions
from ca. 575 Ma. Further precipitation of zircon to
partially or completely infill the tubes occurred in equilibrium with melt, garnet and monazite only by 535 Ma


suggesting some 40 Ma of melt migration and residence at near
-
UHT conditions in this hot or
ogen.

Key references
: Baldwin, J. A., Brown, M., and Schmitz, M. D., 2007, First application of titanium
-
in
-
zircon
thermometry to ultrahigh
-
temperature metamorphism: Geology, v. 35 no. 4, p. 295
-
298.


Harley, S. L., Kelly, N., and Möller, A., 2007, Zircon
Behaviour and the Thermal Histories of Mountain Chains:
Elements, v. 3, no. 1, p. 25
-
30.


Interrogating

rocks at annual to decadal timescales in the Precambrian: novel algorithms and
exceptional samples

Tim Raub (University of St Andrews, UK)

Email:
timraub@st
-
andrews.ac.uk


Spectral analysis of geological time series generally use variations of Fourier or wavelet transform signal
processing methods

to discern periodic system responses

in context of an inheren
tly noisy background.


Although mathematically rigorous, both sinusoid (Fourier) and

wavelet
-
based decompositions

tend to produce
spectral artifacts (bleeding, aliasing, detrending and normalizing

loss
-
of
-
information, interpolation for requisite
normal dat
a spacing).


In worst
-
case scenarios, these methods can fail to identify periodicities that really do exist,
and they

are capable of inferring

power to artificial modes.


These problems

occur most often when the data
series in question is truly the result
of a

regular process that naturally varies

in period; and when system
responses

are nonlinear, leading to variable signal amplitude between successive events.


These sorts of
nonlinear, quasi
-
periodic processes dominate the real world and the geologic reco
rd.



A new, adaptive algorithm for decomposing

data series into "intrinsic mode functions" has been proposed and
gained widespread use in engineering, signal processing,

atmospheric science, and seismology.


It is equally well
-
suited for sedimentary and b
iological data series.


This algorithm, "Ensemble Empirical Mode Decomposition"
(EEMD) (
Huang et al., 1998; Huang and Wu, 2008
) is not mathematically rigourous, and its utility depends in
part upon prior assumption; and in part on whether or not

it produce
s interpretively useful and predictively
testable outcomes.


However the intrinsic mode functions that it produces will mathematically reconstruct to
produce the exact, original data series; and they are in turn suitable for a modified Hilbert
-
Transform an
alysis
which can reveal the extent to which they are real versus artifactual.




This talk will sketch the method for this algorithm and present EEMD results for two exceptional Precambrian
rocks.


The older unit, Firstbrook Member rhythmites from ~2.2
Ga Gowganda Formation of Superior Craton's
Huronian Basin, is commonly interpreted as recording a long series of annual, proglacial varves.


Whereas


Fourier analysis picks out only a ~decadal oscillation, EEMD reveals a multi
-
annual oscillation to be equal
ly
powerful to the decadal oscillation, and it quantifies the natural variability in both mode periods.


EEMD also
hints at longer
-
period oscillations that may reflect long solar cycles influencing Palaeoproterozoic deglacial
climate, and it quantifies at
least a quarter of the data series as stochastic noise.


A younger, ~1.1 Ga oscillatory
stromatolite from Tieling Formation, North China Block yields impersistent ~14
-
band cyclicity to conventional
Fourier analysis.


EEMD reveals multiple modes which are a
t apparent odds with conventional interpretation of
the stromatolite

oscillating its orientation as a heliotropic biological response.


Key references
: Hughes, G. B., Giegengack, R., and Kritikos, H. N., 2003, Modern spectral climate patterns in
rhythmical
ly deposited argillites of the Gowganda Formation (Early Proterozoic), southern Ontario, Canada:
Earth and Planetary Science Letters, v. 207, no. 1
-
4, p. 13
-
22.


Huang, N. E., Shen, Z., Long, S. R., Wu, M. L. C., Shih, H. H., Zheng, Q. N., Yen, N. C., Tung
, C. C., and Liu, H. H., 1998,
The empirical mode decomposition and the Hilbert spectrum for nonlinear and non
-
stationary time series
analysis: Proceedings of the Royal Society of London Series a
-
Mathematical Physical and Engineering Sciences, v.
454, no.
1971, p. 903
-
995


Huang, N. E., and Wu, Z. H., 2008, A review on Hilbert
-
Huang transform: method and its applications to
geophysical studies: Reviews of Geophysics, v. 46, no. 2.


The detrital mineral record of Cenozoic deposits of the Central Myanmar Bas
in, Burma: implications for
the evolution of the eastern Himalayan syntaxis

Cynthia Brezina
and

Ruth Robinson (University of St Andrews, UK)

Email:
cab49@st
-
andrews.ac.uk
,
rajr@st
-
andrews.ac.uk


The eastern syntaxis region of the Himalayas is a complex geological collision zone where exhumation,
deformation and river capture have all influenced landscape evolution during the Cenozoic.
Detrital minerals in
the Eocene,
Oligocene, and Miocene sandstones of the Central Myanmar Basin (Burma) provide a record of the
evolution of the syntaxis, as well as an opportunity to explore how surface processes couple to exhumation and
deformation over the past ~55 Ma. We have analysed

detrital zircons (U/Pb and
ε
Hf, and fission track),
muscovites (
40
Ar
-
39
Ar), and garnets (EPMA) in order to build a database of provenance and exhumation rates,
and have combined this with published datasets on bedrock crystallization and cooling ages in the region.

The U/Pb ages an
d
ε
Hf values of detrital zircons demonstrate that as far back as 43 Ma, the Central Myanmar
Basin sediments contain zircons that originated from the Gangdese batholith in Tibet. The detrital garnet
geochemistry also shows a significant contribution from a
granitic source, similar to garnets in the modern
Tsangpo River sediments. We interpret these data as evidence that the Tsangpo was originally connected to the
proto
-
Irrawaddy River through the eastern syntaxis region during the Eocene. Based on changes i
n the detrital
zircon Hf values, the minimum age of Gangdese
-
derived detrital zircons, and the garnet geochemistry of the
Miocene deposits, we constrain the timing of Tsangpo
-
Irrawaddy disconnection to about 18 Ma. In the “post
-
disconnection” Miocene depos
its in Burma, the detrital garnets lose the granitic source and the
ε
Hf values of
detrital zircons suggest that batholiths in the eastern syntaxis (Bomi
-
Chayu) and Burma (Danxi
-
Burma) were the
main provenance areas. The syntaxis batholiths are situated on
the Jiali Fault and between the Bangong
-
Nujiang
and Yarlung
-
Tsangpo suture zones. Based on present
-
day topography, the Jiali Fault is the most obvious position
for the former Tsangpo
-
Irrawaddy river.


We hypothesise that increased exhumation and focused d
eformation in the syntaxis contributed to the
disconnection of the Tsangpo
-
Irrawaddy river, and the birth of the Tsangpo
-
Brahmaputra system. New
40
Ar
-
39
Ar
detrital mica and ZFT data allow us to test this, and refine the age of disconnection. One significa
nt aspect of the
Tsangpo
-
Irrawaddy disconnection is that deformation appears to have been focused towards the interior of the
syntaxis in the early Miocene, and the coupling of tectonics and erosion breaks down for this palaeo
-
river. In
contrast, steep spa
tial gradients in rates of exhumation and deformation between the Jiali Fault and the


Bangong
-
Nujiang and Jinacha sutures appear to influence the Salween and Mekong rivers’ ability to keep pace
with exhumation over the duration of the Himalayan collision.


Just how fast can rocks get exhumed by erosion? The example of Namche Barwa, eastern Himalaya and
its record from zircon and rutile thermochronology.

Randall R. Parrish (
NERC Isotope Geosciences Laboratory, BGS, UK)

Email:
rrp@nigl.nerc.ac.uk




New data demonstrates that rutile eroded from the Eastern syntaxis of the Himalaya is mainly <2 Ma old, having
cooled more than 500°C in the last ~1 Ma. This implies erosion rates of 4
-
10 km/Ma and that accelerated upli
ft
in this region is Pleistocene in age.


Key reference
:
Seward, D., and Burg, J. P., 2008, Growth of the Namche Barwa Syntaxis and associated evolution
of the Tsangpo Gorge: Constraints from structural and thermochronological data: Tectonophysics, v. 451
, no. 1
-
4,
p. 282
-
289.


Low temperature thermochronology: current state and future prospects

Fin M. Stuart (Scottish Universities Environmental Research Centre, UK)

Email:
Fin.Stuart@glasgow.ac.uk


Key refer
ences
: Karagaranbafghi, F., Foeken, J. P. T., Guest, B., and Stuart, F. M., 2012, Cooling history of the
Chapedony metamorphic core complex, Central Iran: Implications for the Eurasia

Arabia collision:
Tectonophysics v. 524

525, p. 100

107.


Persano, C., B
arfod, D. N., Stuart, F. M., and Bishop, P., 2007, Constraints on early Cenozoic underplating
-
driven
uplift and denudation of western Scotland from low temperature thermochronometry: Earth and Planetary
Science Letters, v. 263 p. 404

419.



Friday, 13 Apri
l 2012

Jess Barnes (PhD Student, Open University)

A wet Moon? An investigation using hydrogen isotopes





UK Mineralogi
cal Society Distinguished Lecturer 2011
-
2012



The Apollo program took place during 1960
-
70s, with six successful landing
-
and
-
return missions brought back an astonishing 382 kg of rock and soil

samples from the
lunar surface. During the following years those samples were vigorously studied
optically and analytically. The main conclusions arising from that work were that: the
Moon was dominated by two terrains: the Highlands and the Mare; the lik
ely existence
of a lunar magma ocean; that lunar magmatism dates from ~4.5 to ~1Ga; the heavy
the
heavy bombardment is recorded on the lunar surface, and

the Moon is essentially a
'bone
-
dry planetary body' [
1
,
2
]
.


Recently a re
-
investigation of Apollo ro
ck samples has up
-
ended this long standing
consensus that the Moon is an anhydrous planetary body. This has been spurred by the
findings of 'water' in apatite grains from a range of Apollo rock samples, glass beads
and melt inclusions [3
-
7]. The maximum am
ount of water measured thus far has been
from Apollo 12 mare basalt sample 12039 [7]. These authors also measured the
hydrogen isotope ratios of lunar apatites, with δD values up to +1010 ‰ from mare
basalts and up to +340 ‰ from highlands samples. The imp
lications of even small
amounts of water in the Moon are widespread from: the evolution of the proto
-
lunar
disc, to the presence of a lunar magma ocean and to later mantle diversification. More
significant perhaps is the origin of this water: terrestrial,
indigenous to the Moon or
perhaps of cometary origin?


1.

Joliff, B.L., et al., New views of the Moon. 2006: Mineralogical Society of America,
Geochemical Society.


2.

Papike, J.J., Planetary materials. 1998: Mineralogical Society of America.


3.

Saal, A.E., et
al., Volatile content of lunar volcanic glasses and the presence of
water in the Moon's interior. Nature, 2008. 454(7201): p. 192
-
195.


4.

Hauri, E.H., et al., High Pre
-
Eruptive Water Contents Preserved in Lunar Melt
Inclusions. Science, 2011. 333(6039): p.
213.


5.

McCubbin, F.M., et al.
Inhomogenous distribution of magmatic volatiles in the
lunar interior: Clues from the mineral apatite. in 40th Lunar and Planetary
Science Conference. 2009.


6.

Boyce, J.W., et al., Lunar apatite with terrestrial volatile abunda
nces. Nature,
2010. 466(7305): p. 466
-
469. 7.

Greenwood, J.P., et al., Hydrogen isotope ratios
in lunar rocks indicate delivery of cometary water to the Moon. Nature
Geoscience, 2011. 4.




Thursday, 19 April 2012

Dorian Abbot (University of Chicago)

Underst
anding Snowball Earth Events


The Neoproterozoic glaciations (~630 and ~710 Ma), during which ice sheets flowed
into the ocean at the equator, represent the most extreme climatic event on Earth in at
least the past 2 Gyr. These glaciations tie together th
e diverse fields of geology,
geochemistry, climate dynamics, paleontology and astrobiology. Nevertheless, crucial
aspects of Neoproterozoic glaciations remain poorly understood. In particular there
are outstanding questions about the cause of the glaciatio
ns, the conditions during the
events, the way life survived them, and their termination. I will describe my recent
work on these questions, including a theory for the effect of dust on deglaciation and a
newly proposed climate state that is nearly, but not

completely, ice
-
covered, which
could allow consistency with geological data and the survival of life through the
glaciations.


Wednesday, 6 June 2012

Dr Callum J. Hetherington (Texas Tech University)

Refining the magmatic history of a metamorphic core co
mplex by chemical abrasion and
in situ geochronology of accessory minerals


In Lamoille Canyon, Ruby Mountain
-
East Humboldt Range, Nevada, >2 km of vertical
exposure through a metamorphic core complex provides an ideal natural laboratory
for studying many
aspects of crustal extension and associated magmatism. The
infrastructure of the complex exposes metamorphic rocks with calculated pressures
between 200 and 900 MPa, and represents a near continuous cross section through the
middle crust.


Through field o
bservations at least four generations of peraluminous magma were
identified, but more intriguingly, preliminary geochronology suggested that these
magmas were emplaced over a period of 120 million years, w
ith a period of near
-
continuous magmatism between 90 and 50 Ma.


This provides two interesting questions: 1) conventional wisdom suggests a crustal
column may only be melted once, what tectonic or petrologic processes have occurred
to enable four periods
of partial melting? 2) was there a 50 m.y. period of partial
melting and magmatism and how would such a thermal anomaly be sustained? By
integrating detailed out
-
crop scale mapping with detailed textural and compositional
analyses of accessory minerals, it

is possible to demonstrate that Ruby Mountain core


complex development may have been proceeded by as many as three cycles of crustal
thickening and thermal relaxation. Furthermore, through time the mechanism and
heat
-
source that drove the partial melting
reactions changed, which when coupled
with tectonic shuffling, led to different source rocks being melted to produce the
different generations of magma
.