The continental crust has an observed stratification from mafic lower crust to granitic shallow crust. How this stratification arises is one of the key unanswered questions in igneous petrology. For this thesis a general coupled model of heat and mass transport during buoyancy driven melt segregation has been developed and employed to simulate the intrusion and subsequent evolution of sills in regions termed deep crustal hot zones. A system of governing equations describing the conservation of heat, mass and momentum in a two phase media undergoing buoyancy driven melt segregation has been developed. Suitable numerical methods have been employed to solve the governing equations and a computer code developed for their solution. As sills are emplaced into the crust they cool and crystallise with the release of latent heat warming and then melting the surrounding country rock. It is shown that contributions from both the crust and intrusion are significant. Subsequent melt migration leads to the development of high melt fraction layers able to fluidise and form mobile magmas in geologically short time periods. The model can predict temperature and melt fraction of these mobile magmas and from this the composition can be inferred. Low temperature, evolved magmas are shown to develop which are able to leave the hot zone and ascend to the shallow crust, driving crustal stratification. The model is then extended to discuss the transport of major components during melt migration and applied to several geologically significant systems. Binary systems have been chosen due to their relative simplicity and the importance of several two component phase diagrams in igneous systems. Mixing in a heterogeneous crust is shown to lead to previously unobserved effects such as the formation of mobile magmas at the interface between compositionally distinct layers. Finally trace element transport during melt migration is investigated for both compatible and incompatible elements. Large deviations from the current paradigms of trace element fractionation are observed when the migration of species is modelled explicitly. This thesis shows that melt migration is an important process in geological systems and is a major influence during the formation of mobile magmas and their resultant temperature, composition and trace element concentration.

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Subduction zones represent a tectonic environment where the Earth's crust is subducted into the mantle, but several components are returned to the surface via arc magmatism. These include Cu and S, which form Porphyry Copper Deposits (PCD). It has been suggested these 'hot spots' of Cu represent local oxygen fugacity (fO2) anomalies resulting from strongly oxidized conditions in the magma at some stage on the journey from slab to near-surface. One obstacle to our understanding of this journey is the difficulty in controlling fO2 in high-pressure experiments representing the mid- to lower-crust. A major part of this thesis was spent wrestling with experimental problems related to 102 control in the high-pressure piston-cylinder apparatus. This led to a new capsule design, which was used subsequently to study the evolution and speciation of sulphur at mid- to deep-crustal magmatic conditions. Results confirm that oxidized conditions leading to suppression of sulphide phases is an important process in the formation of PCDs but this is important even in the deep crust. fO2 plays an important role in controlling the volatile species, but also S speciation and solubility in the melt, across the 'sulphide (S2-) to sulphate (S6+)' transition. Experiments show a strong shift of this transition to more oxidized conditions with the increasing depth, expanding sulphide stability. Sulphide saturation can still be avoided by deep S-degassing but requires exceptionally large amounts of COH-fluid, rare even for arc magmas. The transition also appears to involve a species that causes a solubility minimum as 'well as enhancing Au solubility. Samples from the high 102 , 1815 eruption of Tambora were found to have sulphide but these were found to be subject to desulphurisation, allowing to examine the release of Cu with the S, but also the role of sulphide in the subsequent global climate change in 1816.

Porphyry copper deposits (PCDs) are associated with shallow-level, subvolcanic intrusions. While PCDs have been studied extensively, the petrology of the host intrusions have received relatively little attention because hydrolytic alteration often destroys the primary petrologic features. However, these features are key to understanding the trans-crustal arc magmatic processes that result in PCDs. The Don Manuel porphyry copper system of the Miocene-Pliocene PCD belt of central Chile, contains significant alteration, but it is localized, allowing investigation of the primary petrology in relatively fresh portions. Fieldwork and examination of drill cores enabled characterization of the Don Manuel igneous complex (DMIC). The DMIC consists of six intrusive units ranging from 53-74 wt.% Si02. Highresolution CA-ID-TIMS U-Pb and whole-rock 40Ar/39Ar dating indicate that the intermediate to felsic units were emplaced in pulses between 4.0-3 .6 Ma, making it the youngest documented PCD system in the Andes. The episodic emplacement of this igneous complex occurred on a timescale similar to eruption and degassing events in arc volcanic systems. Petrographic, geochemical and isotopic data establish the origin and assembly of the diverse magmas that comprise the DMIC. The magmas have undergone polybaric differentiation from parents with varying initial water contents. Mineral chemistry, coupled ~ith thermobarometry, constrain the petrogenesis of the DMIC, indicating that wet magmas began differentiating in the lower to middle crust and continued to evolve in shallow crustal reservoirs. Intermediate porphyry dikes associated with copper mineralization contain diverse crystal cargos that represent mush entrained from different depths, crystals originating in different magmas, and crystals grown in-situ from hybridized magmas. The petrologic complexity and episodic timescale observed in the porphyry copperrelated magmas is analogous to the open system, trans-crustal processes indicated arid observed in arc volcanic systems. Examination of other PCDs through this framework could provide additional information about key ore ingredients such as volatiles, metals, and sulfur.

The Early-Middle Eocene deep-marine siliciclastic systems of the Ainsa and Jaca foreland basins, Spanish Pyrenees, have been used to develop and support generic models for deep-marine deposits, from process-based to system-based perspectives, and these ideas have been applied globally by academics and industry alike. Despite the considerable amount of research into many aspects of sedimentology of the Ainsa and Jaca basins, the widely-adopted stratigraphic correlation of sandstone systems in the Ainsa and Jaca basins is very poorly-constrained, although the stratigraphy and accurate correlation of sandstone bodies along the basin are paramount to any depositional models that arise from any studies in the Ainsa and Jaca basins. This study used petrography, geochronology, major and trace element geochemistry to better constrain and understand the evolution of the basinal sediments and fingerprint the sandstone bodies within the Ainsa-Jaca basin as a means of correlation. An additional pilot study was carried out on carbon and oxygen isotopic signatures of larger foraminifera from the outcrops. Three discrete sediment sources are recognised for the deep-marine Early to Mid-Eocene sandstone bodies in the Ainsa and Jaca basins. The arenite composition in the Ainsa and Jaca basins is interpreted to be mainly controlled by synsedimentary tectonic processes that led to changes in sediment sources during basin evolution. Comprehensive petrography data shows that each system of the Ainsa and Jaca basins has a characteristic petrofacies. Three main petrofacies are recognised and on the basis of these petrofacies, a revised correlation of the sandy systems is proposed between the more proximal Ainsa basin, and the more distal Jaca basin sediments, now separated by the Boltana anticline, across which it is impossible to actually trace out individual beds or sandstone packages between both basins. The new correlation scheme, along with the newly identified sediment provenances, changes the current (published) understanding of the Ainsa and Jaca basins evolution and palaeogeography.

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