Appendix 2: Plans for 2015  

FLAGSHIP PROGRAMS 2014-2017

1. TARDIS II: DEEP-EARTH FLUIDS IN SUBDUCTION ZONES, OPHIOLITES AND CRATONIC ROOTS

This program investigates targeted novel aspects of deep subduction during continental collision, ophiolite fragments that get caught up in the subduction environment, and the role of fluids in deep mantle lithosphere.  Recently recognised super-reducing, ultra-high-pressure (SuR-UHP: 400-600 km) mineral assemblages in selected ophiolites carry implications for the evolution of fluid compositions, reactions and redox states in subduction environments from the surface to the Transition Zone, and suggest a new geodynamic collision process that may improve mineral exploration concepts for paleosubduction regimes.  We aim to determine the extent of isotopic fractionation in a range of elements caused by redox reactions that produce many oxygen-free phases at UHP conditions.  A goal is an experimentally testable model for the generation and preservation of highly reducing conditions, and to quantify constraints on the geochemical and tectonic processes that have produced SuR-UHP assemblages and brought them to the surface in ophiolites, and to produce a geodynamic model for these processes.

UHP rocks and lithospheric diamonds will be used to refine the geochemical signatures of deep fluids and microstructural histories to provide additional insights into deep-mantle fluid types and processes.  The isotopic variability of carbon, oxygen, nitrogen and sulfur in diamond-forming fluids will be studied to ascertain whether these are primary signatures, or are produced by isotopic fractionation during diamond growth.

Workplan for 2015

Eight separate but inter-related approaches will be embarked on and progressively integrated.  [1] Fluids in diamonds in the ophiolitic material appear, from their nitrogen aggregation states, to have only a relatively short history at low temperatures.  Further FTIR will be supported by nitrogen and carbon isotope analyses to test this conclusion.  [2] Stable isotope measurements in situ of relevant elements in their oxidised and reduced form will test for differences in isotope fractionation.  This will require considerable method development across the CCFS instruments.  [3] Oxidation-state variations of elements such as Fe, V, Cr and Ti in the SuR-UHP assemblages will be measured with Mössbauer spectroscopy and XANES mapping at the Australian Synchrotron.  [4] Characterisation of new, rare high-pressure minerals in the Tibetan chromitites will be carried out, including their microstructures by EBSD.  [5] Minor sulfide phases in the chromitites will be analysed for the isotopes of Cu, S, Fe and Pb.  [6] Noble gases (He, Ne, Xe) of the SuR-UHP assemblages will be used to ascertain the degree of input from the deep Earth relative to that from the subducted material.  [7] Dynamic modelling has already implicated rollback of deeply penetrating slabs.  These geodynamic mechanisms will be investigated in detail.  [8] Experimental studies at high pressures will enter the planning stages.  These will be designed to test the stability fields of new and rare minerals of the SuR-UHP assemblage, and to address other questions that crop up during the course of the program.

2. MULTI-SCALE FOUR-DIMENSIONAL GENESIS, TRANSFER AND FOCUS OF FLUIDS AND METALS

This program aims to address the critical link between metal source fertility and four-dimensional evolution of multi-scale fluid pathways that ensure efficient mass and fluid flux transfer between the mantle and the upper crust. 

The ability to discover new mineral resources has become very challenging partly due to the limited predictive capability of the traditional analogue deposit model approach.  Recently, new conceptual frameworks such as the mineral systems approach have been proposed, which provide more powerful predictive capability for mineral exploration.  This program tests the hypothesis that the genesis of sizeable mineral deposits is the end product of self-organised critical systems operating from the scale of the planet all the way to the very focused environment where ore deposits can form.  The mineral systems approach represents a step change in the way we investigate ore-forming processes, and considers the evolving relationship between the localised setting of anomalous metal resources and processes operating at the scale of the planet.  Prior to the advent of the mineral systems concept, single deposits were documented in detail as unique occurrences, but this approach failed to focus on the commonalities among various occurrences and, more importantly, ignored the larger scale architectural framework that hosts them.  The new rationale takes a more holistic approach, acknowledging that the genesis of mineral occurrences required the conjunction in time and space of three main independent parameters; fertility, lithosphere-scale architecture, and favourable transient geodynamics.  This conceptual framework forms a key pillar for the CCFS research goals.

Workplan for 2015

This frontier study is designed to contribute to the goal of creating a step-change in exploration targeting.  First it will be necessary to assemble and critically assess the great wealth of already available data.  At the same time, a series of pilot studies is starting (e.g. Tibet) and continuing (e.g. Southeast Greenland).  These will lay robust foundations for the work program for the following years, in which the researchers will focus on knowledge gaps identified in the pilot studies.  More importantly, the program represents the integration and continuation of a series of existing projects.

We will start utilising the new ARC-funded EBSD apparatus housed at Curtin, strengthening our knowledge of the key relationships between deformation at the micro-scale and the transfer of key fluids and metals.  This work will tie in nicely with the ongoing work of Sandra Piazolo in her Future Fellowship study.  We also endeavour to continue the ongoing work on lithium isotopes and labelled experiments.  However, to analyse experimental run products we would need in situ techniques that require further development.  Hence, we will push the development of in situ techniques and also analyse mineral concentrates, glasses, and whole-rock powders at the University of Maryland.  Finally, the role of water and other volatiles in the transport and concentration of metals focuses on arc magmas, experiments and Cu-porphyry systems, furthering and expanding the investigation of subduction systems in CCFS.

3. TWO-PHASE REACTIVE FLOW IN MULTI-COMPONENT DEFORMABLE MEDIA

The overarching goal of this program is the development and application of in-house state-of-the-art computational simulation tools to model complex geochemical-geodynamic processes involving two-phase reactive flow in multi-component deformable media.  Many aspects of Earth Science, from ore deposits to giant earthquakes, depend critically on the complex interaction of solids and fluids.  Numerically simulation of these processes and effective visualisations of the results is critical to understanding how these Earth system components work, but our ability to do this is currently very limited.  We are developing the next generation of numerical codes and refining thermodynamic parameters by high-pressure experiments to handle these complex problems.  This will lead to important improvements in the quantification and visualisation of Earth processes, and will be applied to a variety of geodynamic situations.

The new experimental group at Macquarie joins this initiative to provide input on physico-chemical parameters of minerals and fluids in the deep mantle, the composition of melts that infiltrate the lithosphere, and their effects on its geodynamics and stability.

Workplan for 2015

A main focus of work for the coming year is the further development of 3D models.  High-resolution runs will be performed at Intersect, and the coding of dehydration sequences and melting will be completed.

Development of the FEM methodologies will be continued, the techniques published, and the FEM developments (e.g.  chemical advection, multiscale FEM) will be integrated with 3D Aspect models.  Further developments will be made to the radial anisotropy code, imaging of the lithosphere, and applications.

The integration of experimental data will begin with collation of existing data, and then we will proceed to planning of further high-pressure experiments on the stability of mantle phases, with the first experiments conducted as the high-pressure equipment is set up.  Using a similar approach, high-pressure experimental results relevant to the composition of mantle melts and their interaction with peridotites with varying degrees of depletion in the mantle lithosphere will be assessed and an experimental program planned.

Interacting fluids and solid matrices are extremely important in subduction systems.  Recent work has highlighted fluid release during flat subduction, and the geological response to these events may significantly impinge on the over-riding lithosphere.  Two modern examples of this are the Farallon slab in western North America, and South China.  The western USA is a tectonically active region with extensive magmatism over the past 100 Ma, which is often hypothesised to be related to the flat subduction of the ancient oceanic Farallon Plate.  South China has one of the most complete records of hypothesised flat-slab subduction and subsequent slab foundering, causing major regional tectono-thermal events, magmatism, basin formation, large-scale continental vertical tectonic movements, and mineralisation.  These areas will be assessed with Ambient Noise Tomography (ANT) and Multiple Plane Wave Tomography (MPWT) in seismic imaging to construct 3D seismic models using data from the extensive broadband Transportable Array component of EarthScope/USArray, which are archived in IRIS/DMC and open for public download.  They will be integrated with application runs on the flat subduction scenarios, which will be well advanced in 2015.

4. A PLANETARY DRIVER OF ATMOSPHERIC, ENVIRONMENTAL AND BIOLOGICAL EVOLUTION THROUGH TIME

We investigate how the evolution of life and ore deposits were linked to the changing whole-Earth System, focusing on planetary driving forces that affected all of the different shells of the planet, to develop a 4-dimensional conceptual framework of Earth evolution.  Given the broadly comparable petrological evolution of Earth and Mars, we also aim to put forward new working hypotheses on how life and mineral systems may have formed and evolved on the red planet.

This program will test the hypothesis that the evolution of life and the genesis of sizeable mineral deposits are the end products of systems operating at the scale of the planet all the way down to the specific environments where life flourished and mineral deposits formed.  A component of the program will focus on Mars to investigate whether the evolution of life and the genesis of mineral systems on the red planet operated in a broadly similar fashion.  We evaluate the relative importance of (1) the threshold barriers that form in specific environments creating strong chemical and energy gradients in the crust, and the self-organised behaviour of mineral systems and life; (2) the evolving nature of “traps” at the lithosphere-hydrosphere boundary, where life and ore deposits developed through time; (3) the global scale cycle of key elements and heat transfer essential for the evolution of life and formation of ore deposits; and (4) the 4-D evolution of the pathways that connect different geochemical reservoirs through time, linked to the changing tectonic style of the planet, as a guide to understanding biological and ore deposit evolution through time.

Workplan for 2015

>Module 1:  Vital pathways investigates the role of mantle melts in providing heat and elements to the lithosphere on both Earth and Mars.  Multiple sulfur-isotope and trace-element data on a selected series of Martian meteorites will be compared with analogous Proterozoic ferropicrites from Pechenga, Russia.  Our aim is to determine if and how such Fe-rich magmas became capable of forming discrete mineralisation.  Parallel studies will investigate the changing composition of volcanic belts, ore deposit fluids and S-isotopic compositions through time, focusing on Archean-Proterozoic greenstone belts and a suite of VMS deposits in Western Australia that span the period of supposed onset of modern-style subduction in the Mesoarchean. 

>Module 2:  Critical interfaces will investigate changes to lithosphere/exosphere interaction in two exceptionally well-preserved Precambrian areas.  Large-scale hydrothermal alteration systems that harbour the earliest traces of life on Earth in the Paleoarchean rocks of the Pilbara Craton will be analysed in detail by CCFS members and international colleagues.  Changes in the composition of carbonaceous matter and the redistribution of metal ions in hydrothermal veins will be ascertained using oxygen isotopes.  We will also investigate carbonate minerals as a means to identify microbial processes and the composition of the exosphere on early Earth.  Low-grade metamorphic grade rocks of the Paleoproterozoic Turee Creek Group, Western Australia, will be analysed for trace element geochemistry, C and Mo and Sr isotopes, in order to track the changing biosphere as it adapted to rising oxygen levels and the change from a dominantly chemical to a dominantly mechanical weathering regime.  This work ties into the SIEF initiative in the Capricorn Orogen, where Proterozoic VMS systems can be compared and contrasted with their Archean equivalents. 

>Module 3:  >Global cycles of elements will continue to investigate changes in life-essential elements (C, S, Fe, N) through time, in order to better constrain global changes in the biosphere through time.  A major focus will be on both the Mesoarchean onset of modern-style subduction and the rise in atmospheric oxygen.  Iron-formation units will be analysed for their S and Fe isotopic compositions, and a set of three diamond-drill cores from the Paleoproterozoic Turee Creek Group of Western Australia will be analysed for their S, Fe, Mo and Sr isotopic compositions.  Organic geochemistry will evaluate the evolution of the biosphere across this interval, and S-MIF signatures will assess whether the atmospheric and biological signatures in sulfides can be decoupled, and perhaps distinguish the differing contributions and/or onset of sulfate-reducing bacteria from sulfur-disproportionating bacteria. 

>Module 4:  Planetary Driver will focus on combining all the information from modules 1-3, and from other studies, into a holistic, 4-dimensional model of Earth evolution throughout the Precambrian.  A critical aspect is the changes produced by the onset of modern-style subduction, as this gave rise to the modern Earth geodynamic system and fluid circulation systems.  Whole-Earth modelling of the effects of rapid and wholescale subduction during the prelude to supercontinent amalgamation events and their effects on mantle temperatures and tectonics will be conducted using a Lagrangian integration point finite element method (Ellipsis).  This model uses a Cartesian geometry with a periodic (wrap-around) side boundary condition, and free-slip isotemperature conditions at the top and bottom.

5. DETECTING EARTH’S RHYTHMS: AUSTRALIA’S PROTEROZOIC RECORD IN A GLOBAL CONTEXT

Earth’s history is considered to have been dominated by cycles of supercontinent formation and breakup.  This program will test this hypothesis and its relevance to Australia’s geological evolution and assess its positions during the supercontinent cycles by examining the palaeomagnetic, petrological and detrital provenance record of the Australian continent.  By studying primarily Australian rocks and comparing the results with global analogues, we aim to extend our knowledge about supercontinent cycles and the evolution of the Australian continent to the Paleoproterozoic and further back in time.  Such knowledge is fundamental for understanding the first-order fluid cycles that controlled the formation and redistribution of Earth resources, and the establishment of a 4D global geodynamic model.

We aim to examine the position of the Australian continent during supercontinent cycles and its record of plume events through a multidisciplinary study of Australian rocks.  We will focus on the following scientific questions: (1) Was Australia neighboured by East Asian continental blocks during the assembly of Gondwanaland? If yes, which ones, and what was their collision and breakup history? (2) Was there indeed a 40° rotation between northern and southern Australia during the Neoproterozoic that led to the formation of the Paterson-Peterman intraplate orogen? (3) When and how was the Australia Precambrian basement joined together? (4) What was Australia’s role in the configuration and evolution of Pre-Rodinia supercontinent(s)?

Workplan for 2015

Paleomagnetic analyses are being conducted on samples collected from the Mesoproterozoic Morawa Lavas (Western Australia), and a sampling trip to the Kimberley region targeting Paleoproterozoic and Neoproterozoic rocks is planned and will hopefully be carried out in 2015.  New PhD students will be recruited to sample and analyse southwest Yilgarn dykes  for their age, geochemistry and palaeomagnetism.  Sampling and analysis of Cambro-Ordovician clastic rocks from NW Australia and South China will also be carried out.

Our new geochronological and paleomagnetic data from the ~2.4 Ga Erayinia mafic dykes in the southwestern Yilgarn, will be completed and published, and we will continue our international collaborations on a number of offshore targets of Precambrian paleomagnetism and paleogeography.

We will participate in the Nordic Paleomagnetic Workshop in Norway with the aim of further developing the Global Paleomagnetic Database, and we will complete trace element and Nd isotope analyses of samples from the Bangemall Basin collected in 2013.

6. FLUID REGIMES AND THE COMPOSITION OF THE EARLY EARTH

Zircon crystals are currently the only material that records events in the first 500 million years of Earth’s history, since no rocks have survived from this period and no other minerals have been dated as Hadean in age.  There is growing evidence from the study of these zircon crystals that the Earth stabilised rapidly after accretion and that both solid rock and liquid water were present within 150 million years of its formation.  In this program, the geochemical signatures of zircon crystals from all known Hadean and early Archean localities will be utilised, together with geochemistry of the oldest known rocks and the application of geophysical and geochemical modelling, to establish how the first crust evolved, why it was destroyed and the role of fluids in this process.  Furthermore, it will evaluate the changes that took place throughout the Archean as crustal processes evolved.  In addition, work will continue on Martian meteorites and lunar samples in order to provide further constraints on the early history of the Solar System, especially the role played by fluids.

Workplan for 2015

We are investigating rocks and minerals from locations that have so far not been examined during the first three years of operation of the CCFS.  This includes analysis of newly acquired material from Labrador and the North China Craton.  In addition, work will continue on the Aker Peak samples from Antarctica. 

Further work is planned for both the Tarim and Bundelkhand cratons, the former in association with Nanjing University.  Preliminary work indicates that these cratons show a similar sequence of magmatic and metamorphic events to the North China Craton.  Ion imaging of zircons from Anshan, and those currently available from Acasta and Greenland, will be completed by the end of 2015, and work will commence on the new samples collected from Labrador during the 2014 field season.  Associated work utilising EBSD, TEM and the Synchrotron will be undertaken using both Australian and European connections.  The first geoscience-dedicated Cameca Atom Probe will be installed at Curtin in 2015 and, after set-up, extensive work will be undertaken on the ancient zircon inventory held by CCFS members. 

It is anticipated that work will commence with CI Craig O’Neill and staff appointed at Curtin to the Perth supercomputer consortium on new modelling studies that will evaluate the transition from a possible stagnant-lid state to a tectonically active early Earth.

With respect to extra-terrestrial investigations, work will continue to focus on Martian meteorites and the role that fluids have played in establishing the current mineralogy.  Pb and S isotopic data will be collected in order to evaluate the interaction of Martian mantle melts with the evolving crust.  Further work is also being undertaken on Apollo 14 Lunar samples, including development work to enable direct dating of basaltic rocks and to provide a unified model for the Pb isotope evolution of the Moon.

7. 3D ARCHITECTURE AND PRECAMBRIAN CRUSTAL EVOLUTION IN THE WESTERN YILGARN, AUSTRALIA

Iron, Gold and Nickel deposits are of global economic significance, and the Neoarchean Yilgarn Craton and the Proterozoic orogens around its margins constitute one of Earth’s greatest mineral treasure troves.  Whereas the Yilgarn is one of the best-studied Archean cratons, its enormous size and limited outcrop are detrimental to a deep understanding of what controls the distribution of resources and which geodynamic processes were involved in the tectonic assembly of the Australian continent.  The principal aim of this program is to combine geological, geochemical and geophysical techniques to propose a 3D structural model of the lithosphere of the Yilgarn Craton and its margins.

The Yilgarn Craton is a large and highly complex piece of Archean crust with a long history extending from 4.4-2.6 Ga.  Amalgamation of terranes is thought to have occurred around 2.65 Ga.  Recent work by GSWA in the northwestern part of the craton has identified a long-lived, autochthonous history of crustal development there, including episodes of volcanism, granitic magmatism, shearing and gold mineralisation that are similar in composition and temporal development to those further east in the Eastern Goldfields Superterrane, which has been interpreted as the accreted, younger part of the craton.  This implies that there are significant problems with current models of crustal development through arc-accretion tectonics.  

There is a growing realisation that understanding how mineralised crustal provinces form requires structural and chemical information on the entire lithosphere.  This is addressed in the multi-disciplinary SIEF project “The Distal Footprints of Giant Ore Systems: UNCOVER Australia”, which involves collaborative research between CSIRO, UWA, Curtin and GSWA, and targets the Capricorn Orogen at the northern boundary of the Yilgarn. 

It includes the Capricorn Orogen Passive Array (COPA), a passive source experiment that will study the deep crustal and shallow lithosphere structure using earthquake seismology.  The data from this experiment will be the main source for the local ambient noise inversion, the receiver function common convection point (CCP) stacking techniques, and possibly a body-wave tomography study.  Given the fact that the passive source site coverage in Western Australia is sparse and that the available permanent sites in the region provide nearly 10 years of data at isolated locations, several techniques that focus on crust and upper mantle structure beneath single stations will also be applied.  This approach has the potential to provide quick access to the crustal and lithospheric structure from these representative sites.

Workplan for 2015

The Capricorn Orogen Passive Array was deployed in collaboration with the GSWA and CET in 2014.  Two field teams worked in the field for three weeks deploying the first 36 sets of broadband instruments.  Data processing related to the ambient noise imaging and the receiver function CCP imaging can now proceed.  During the intervals between the Capricorn field preparation, test-deployment, field deployment, as well as station servicing, the following activities will be conducted simultaneously throughout the year: individual station structural imaging for the permanent sites, travel-time residual preparation for finite frequency body wave tomography, cross-correlation computation and dispersion measurements for ambient noise, receiver function common-conversion-point stacking, and data preparation for continental scale shear wave tomographic inversion.