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This thesis presents the results of a multidisciplinary investigation into the Cenozoic tectono-stratigraphic evolution and mineralization of the Biga Peninsula, northwestern Turkey. This has involved the mapping and analysis of extensional and strike-slip fault systems and of the associated magmatic and volcanic events with a particular focus on the structural controls on the porphyry Cu-Au deposits and epithermal gold mineralization of the region. Detailed field mapping, structural analyses, core-logging of exploration drill holes together with Ar/Ar geochronology, remote sensing analyses and aeromagnetic interpretations were undertaken and integrated to develop new tectono- stratigraphic and magmatic models for the Cenozoic structural evolution and mineralization of the Biga Peninsula. The Biga Peninsula is characterised by the NE-trending Kazdag Massif formed by late Hercinian high grade gneiss and amphibolite metamorphic basement. During the latest Oligocene, re-crystallization and granitoids plutonism (26 - 25 Ma) was followed by metamorphic core complex detachment fault systems. The pre-Cenozoic hanging wall of the Kazdag Massif is composed by Permo- Trassic metasediments (Karakaya Complex) and by Late Cretaceous ophiolites (Cetrni Melange). These are flanked by Oligo-Miocene extensional volcano- sedimentary basins internally deformed by domino-style -NE trending hanging wall extensional faults. Porphyry style Cu-Au mineralization is associated with the granitoid intrusions in the footwall of the detachment fault system. High sulfidation style epithermal Au deposits are found in the hanging wall basins above the core complex detachment fault system. Gold in these major strata- bound silicified lithocaps is controlled by the steep hanging wall extensional faults and associated fracture architectures. The Biga peninsula sits within a system of back-arc extensional basins caused by slab roll-back during the Eocene, Oligocene and Miocene. Regional extension followed the closure of the Vardar-Izmir-Ankara Ocean as the Pontides and Anatolides terranes collided in the Late Cretaceous. This research has identified five stages of back-arc extension with magmatism and volcanic activity associated with magmatic-hydrothermal ore systems. The Middle Eocene and Latest Oligocene magmatic arcs of the Biga Peninsula produced porphyry type and epithermal style mineralization as part of a major NW-SE to E-W arc-shaped magmatic-metallogenic zone running from the Dinarides and the Rhodopes to the Pontides of northwestern Turkey. Since the Early Pliocene, the westward propagation of the North Anatolian Fault generated dextral transtension and new strike-slip fault systems together with increased extension on pre-existing extensional fault systems.

This thesis investigates processes controlling melting beneath ocean islands. Specifically, the physical nature and resulting melting behaviour of the mantle source is addressed by novel approaches. This thesis ranges in scope from broad global perspectives (Chapter 2) to specific investigation of single volcanic edifices (Chapter 4, 5). In particular, I use the moderately incompatible major element titanium (chapter 2) and U-series isotopes (chapter 3, 4, 5) to address mantle melting. Examination of global OIB Ti concentrations, reveals that the source region of most OIB require addition of ~ 1 0% or less recycled mafic oceanic crust. Analytical methods for U-series measurement have been refined (Chapter 3). Detailed examination of one OIB locality (Pico, Azores, Chapter 4) reveals that recycled crust cannot directly contribute to the lavas. Instead, recycled crust must be 'distilled' through the overlying mantle by interaction of eclogitic melts with the surrounding peridotite. At the eventual onset of peridotitic melting, the source carries an enriched signature reflecting mafic crustal addition, but no record of its disparate melting behaviour. Finally, investigation of Sao Miguel, Azores enforces the notion that recycled lithologies do not exert major control on source melting behaviour. This is illustrated by the lack of correlation between the wide range of long-lived isotopic compositions and U-series isotopes. Indeed, the greatest range of suggested primary U-series signatures on Sao Miguel occurs in lavas with the same long-lived isotopic composition.

Subduction, as part of the mantle convective system, is a key process in the Earth's dynamic and chemical evolution. However, many unknowns remain about the mantle's response to subducting slabs, which depends on the degree of slab-mantle coupling. Seismic anisotropy (the directional dependence of seismic wave speed) may provide insights into the dynamic nature of subduction systems, as it can result from the texturing of minerals by flow-induced deformation. Here, I investigate the anisotropic structure of the Indonesian region with shear wave splitting measurements. With several active and relict subduction zones in close proximity to one another, the region lends itself as an ideal natural laboratory to study subduction processes. I measure shear wave splilling in three phases: SKS (delay times, 01: 0.6-2.7 s), local S (01 : (U- I .I s), and source-side S (01: 0. 3- 1.7 ). Combining these phases prov ides improved vertical resolution of anisotropic fabrics, which allows me to distinguish various regions of mantle now within one subduction system. At both the Sangihe and the Banda subduction zone, 1 infer dip-parallel to dip-oblique shear layers above the slab (that possibly ex tend into the mantle transition zone) as well as trench-parallel sub-slab mantle fl ow. At the North Sulawesi subduction zone, toroidal flow is inferred around the slab edge. Additionally, evidence of fossil anisotropy in the overriding plate complements findings from other geophysical techniques (e.g. , Borneo's hi story of block rotation as detected by paleomagnetism). To test the veracity of inferring mantle flow direction from shear wave splilling fast polarisation, I simulate strain -hi story-dependent texture development and estimate the resulting shear wave splilling. In order to test the significance of a rear barrier to achieve trench-parallel sub-slab mantle flow, I compare a one-sided subduction model to one that approximates the doubles sided Molucca Sea subduction system and the shear wave splilling observations of that region. 1 show that, although such a rear barrier significantly amplifies trench-parallel sub-s lab ani sotropy due to mantle flow, it is not necessary to produce trench-parallel fa st directions per se. Such fabrics are achievable in a simple model of one-sided subduction due to a combination of simple and pure shear deformation in the sub-slab mantle. Evidence from shear wave splilling measurements and strain -hi story-dependent texture modelling suggests that the tectonic selling is a precondition for the resulting mantle flow, and that the slab and the surrounding mantle are at least partially coupled. I conclude that, given the right source-receiver geometry, careful observations of shear wave splilling using multiple shear phases are a reliable means of inferring the local mantle flow field , as well as large-scale deformational features in the lithosphere, even in tectonically complex regions such as Indonesia.

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