Plate tectonics is the most important discovery in Earth Science and is a unique characteristic of our planet. It involves formation of new tectonic plates by seafloor spreading and their recycling back into the deep Earth at subduction zones. This process continuously repaves two-thirds of the Earth's surface. The formation of new oceanic crust represents the largest magmatic system on Earth, and involves the cooling and solidification of magma (supplied from below by partial melting of the Earth's mantle) along the 70,000 km global network of seafloor spreading axes. Understanding the details of how ocean crust forms is therefore critical to understanding the exchange of heat and mass from the solid Earth to the oceans and atmosphere. Since the rocks of the deep oceans are largely inaccessible, scientists trying to understand how magma builds new crust at spreading axes employ geophysical (seismic) experiments to investigate the sub-seafloor. Results are then compared to and combined with observations made on oceanic rocks in ophiolites (fragments of oceanic crust and upper mantle that have been pushed onto the continents and exposed above sea-level) to develop scientific models of seafloor spreading. In the search for magma chambers along the East Pacific Rise (EPR), the most magmatically active spreading axis on Earth, geophysicists have discovered thin (10's m thick) lens-shaped magma chambers (known as 'axial melt lenses') at the top of the lower crust that extend along the EPR. These are thought to sit on top of mushes made up of crystals surrounded by small amounts of magma, that feed melt upwards into the overlying melt lens. More detailed experiments have shown that the physical properties of these melt lenses change along the EPR axis, suggesting that the proportion of melt to mush along the EPR varies on a range of length-scales. Upwards expulsion of magma from the melt lens happens periodically via forceful intrusion of sheets of magma (forming so-called "sheeted dyke complexes"), leading to eruption of lava on to the seafloor. This geophysical picture of the magmatic plumbing system of seafloor spreading axes (based mostly on decades-old inferences from seismic experiments) is incomplete, however, and lacks any constraints on the pathways followed by magma migrating into and out of axial melt lens systems. Lateral variations in seafloor morphology and erupted lava compositions suggest that there must be significant along-axis (3D) transport and evolution of melt, but how extensively this occurs, at what level(s) within the crust, and by what mechanisms remain unknown. These questions have broad implications for the overall process of melt generation and delivery from the mantle and formation of ocean crust, and can only be answered by quantifying melt transport trajectories along a spreading axis in detail and by combining this with determinations of magma geochemistry. This project addresses these questions by directly determining the migration pathways followed by magma as it enters and exits from an axial melt lens system that has been mapped out along a 100 km complete spreading segment preserved in the Oman ophiolite. This provides the world's only on-land analog for fast-spreading axes like the EPR. We will use a technique called 'anisotropy of magnetic susceptibility' or 'AMS' to measure the 3D preferred alignments of crystals resulting from the flow of magma during the formation of crustal rocks. We will then combine these observations with geochemical analyses of rock compositions to establish whether and how 3D spatial variations in magma flow regimes along a fast-spreading axis control the geochemical evolution of magmas during crustal construction. This novel approach will allow us to develop a comprehensive model for the anatomy of the magma systems responsible for forming two-thirds of the Earth's surface, testing and challenging the predictions of remotely-sensed seismic investigations.

Group 6 transition metal hydrazides, (L)M=NNH2, occupy a pivotal position on the pathway for the biological and industrial conversion of N2 to NH3. In nature and in several important model systems this proceeds through a series of electron transfer and protonation steps. Considerable international effort has also been spent on trying to use mid-transition metal hydrazide complexes as reagents for the synthesis of value-added organo-nitrogen products. This holy grail concept of directly using atmospheric N2 as a commercial feedstock would by-pass the high-energy Haber-Bosch (NH3 synthesis) process. However, mid-metal M=NNR2 functional group reactivity is minimal. It is characterised only by transformations involving the NR2 (protonation or insertion/condensation involving N-H groups). No M=N bond reactivity is seen and N-N bond cleavage occurs only under highly forcing conditions using external reductants.Structural data and computational studies explain this: for mid-later metals NNR2 is best viewed as a neutral isodiazene :N=NR2. The more dative nature of the M--NNR2 bond and multiple bond character of N=N reduces the intrinsic reactivity at these two sites. In contrast, our X-ray and DFT results for Group 4 NNR2 systems find them to be reduced hydrazides, [NNR2]2-. Specifically, the N-N bonds are lengthened and weakened as the N-N pi* MOs are occupied; the M=N multiple bond is unsaturated and very reactive, further destabilised by the beta-NR2 lone pair. While sharing a simple formula NNR2 , mid-metal isodiazene and early metal hydrazide ligands are as fundamentally different as Fischer carbenes and Schrock alkylidenes. Just as early metal M=CR2 groups are intrinsically more reactive than later metal M=CR2, so it is for M=NNR2.We have recently developed three methods for making these hitherto undeveloped early transition metal hydrazides with Ti=NNR2 functional groups in very different environments. Preliminary results with a range of organic substrates (terminal and internal alkynes, nitriles, isonitriles, phospha-alkynes, CO2, isocyanates) indicate a wealth of cycloaddition chemistry. Remarkably certain alkynes and nitriles insertion into the N-N bond via a unique single N atom transfer step. We have also found this can be made catalytic so that a 1,2-diaminoalkene is formed catalytically at room temperature from a hydrazine and an alkyne: N-N addition across a C-C triple bond. If the diamination reaction can be extended it could ultimately provide a means of adding any general N-X (X = N, O, P) across any unsaturated C-element bond. This has the potential for a paradigm shift in the synthesis of 1,2-diamine and related compounds.In this project we will therefore develop the virtually unexplored area of early transition metal hydrazide chemistry, capable of delivering high-energy, highly reduced N-NR2 and related functional groups to a range of substrates in a 100% efficient, atom by atom manner. Our very recent synthetic methodology breakthroughs and preliminary reactivity studies provide a perfect and timely platform from which rapid progress can be launched. Working with a leading DFT computational Project Partner, we will deliver a fundamental toolbox for understanding and exploiting this unique reactivity in terms of scope, mechanism and applications in C-N, C-C and general C-heteroelement bond formation.

Ocean circulation patterns especially within the deep ocean are a major player in global heat exchange and therefore force and stabilize climate patterns. In the North Atlantic, deep water masses are influenced by two main factors changing deep water strength and composition over time, the potential of water exchange with the Arctic Ocean and the development of the Northern hemisphere glaciation. The overflow across the Greenland-Iceland-Scotland Ridge, one of only two areas, where Arctic Ocean waters are exchanged with the world's oceans, can be shut off by the periodically strong pulsation of the Iceland mantle plume or in more recent times by glaciation of the Northern Seas and its surrounding land masses. In such an event, deep water circulation within the North Atlantic slows significantly, leading among other effects to a colder and more unstable climate in Western Europe.In this project, we propose to reconstruct the past behavior of deep water currents within the North Atlantic, by analyzing downhole logging data collected during IODP Expedition 395 "Reykjanes Ridge Mantle Convection and Climate". The drill sites are located in a transect along 60N, which represent a millennial scale archive of deep ocean sedimentation and current behavior ranging up to 12 Ma in the past to the Miocene. Downhole logging data will be collected after coring and has the advantages of being an in-situ continuous measurement through the strata, bridging potential gaps in core recovery. Recent experiments to measure current strength within the Atlantic has revealed, a decline in current strength in the recent past making the current circulation the weakest in the last millennia. Years of especially weak Atlantic currents correlate with an increase in weather events such as storms and floods within the British Isles and the rest of Western Europe. Understanding the past behavior of deep ocean circulation will therefore allow us to inform climate models used to predict severe weather events and use these predictions to minimize their impacts.

We have known for the last 50 years that Europe and America have been moving apart at about 2cm/yr by processes of seafloor spreading that generate new oceanic crust at the submarine mid-Atlantic Ridge. This is one of the fundamental processes of Plate Tectonics, and has shaped the planet that we live on. Yet because we cannot use standard remote sensing techniques using electromagnetic radiation to study the seafloor, in many ways we know more about the surface of Mars than we do about the floor of the Atlantic! Over the last 12 years improved sonar surveys of the mid Atlantic Ridge have revealed a new mode of seafloor spreading where a significant part of the plate divergence is taken up by slip on long-lived, convex upward detachment faults, rather than mainly by magmatic intrusion. Up to half of the Atlantic seafloor may have formed in this way. These detachment faults are associated with large hydrothermal systems producing black smokers venting 400 C fluids on the seafloor. On fast (10-15 cm/yr) spreading ridges such as the East Pacific Rise, black smoker systems are small, short-lived, and located in zones of active volcanism, and are supplied with heat by shallow (1-2 km) magma chambers that are there more or less all the time. These systems have been modelled extensively, and a key element is the existence of a thin conductive boundary layer between molten magma and the hydrothermal fluid. On the mid-Atlantic ridge, black smoker systems are more widely spaced, larger, and longer lived, and often are located a few km away from the zone of active volcanism. These systems may in some cases be controlled by fluid flow up detachment faults, with heat supplied by episodic magma chambers as deep as 7km below seafloor, and much less numerical modelling work has been done on them. We have identified a fossil thermal boundary layer in a detachment fault sampled by drilling. In this proposal we plan to investigate this boundary layer more thoroughly, as well as the complex interrelationships between faulting, magmatism and hydrothermal circulation at slow spreading ridges. We will address this problem by building thermal and hydrothermal numerical models to predict both the asymmetric thermal structure produced by detachment faulting and the hydrothermal circulation patterns associated with permeable fault zones and localised magmatism. The hydrothermal models have to be very sophisticated because of the complicated properties of water, which changes density and viscosity very rapidly in the temperature range of black smoker systems. Hence we will work with experienced modellers in Paris to achieve our aims. We will test these models using data on cooling rates of rocks from IODP core in the footwall of an exposed detachment fault in the Atlantic - these cooling rates are calculated by comparing the compositions of natural minerals with experimental data on diffusion rates of trace elements. The aim of our models is not to replicate nature precisely (there are too many unknowns to do that) - but to test the range of parameter values that generate acceptable results. For example, the model must generate vents with the temperature measured on the seafloor and the heat output estimated from geochemical data - what are the minimum values of fault zone thickness and permeability that allow this to happen? These values can then be compared with physical models of permeability based on fracture densities and seismicity distributions. Because it is hard to observe subsurface geology or fluid flow directly, modelling is often the only way of determining whether hypotheses are realistic. At the end of this project we will have a better understanding of one of the most important but least accessible parts of the Earth System - the formation of new lithosphere at ridge crests, and the complex interactions between the ocean and the crust that occur as a result of this process.

The process of speciation involves the progressive evolution of reproductive isolation between divergent populations. When this process happens in the face of gene flow, differentiation is expected to be variable across the genome reflecting the direct operation of natural selection and the barrier created for regions surrounding selected loci. Population genomics and QTL mapping approaches have recently contributed significantly to detecting regions under selection and associated islands of differentiation but further progress is difficult in many systems. We argue that a candidate gene approach can significantly advance this field. We propose to study sequence and expression divergence for the entire known repertoire of chemosensory genes in host races of the pea aphid. This study system is unique in having multiple races at different levels of divergence, excellent background information and a sequenced genome. This allows us to apply the latest approaches (Nimblegen capture arrays, 454 sequencing and Illumina Digitial Gene Expression) to this major problem in evolutionary genetics.