Graptolite fossils provide a means for separating Late Ordovician autochthonous Martinsburg foreland basin strata (Appalachians, Pennsylvania, USA) from tectonically emplaced allochthonous Hamburg succession rocks. The youngest allochthonous rocks (Dauphin Formation) are Middle Ordovician, late Darriwilian 3 to 4a age, approximately two graptolite zones older than the foreland strata. Nineteen taxa described from the Dauphin Formation include Archiclimacograptus cf. A. riddellenis (Harris), Cryptographs schaeferi Lapworth, Normalograptus antiquus (Ge), Pterograptus elegans Holm, Hustedograptus teretiusculus (Hisinger)?, Pseudophyllograptus augustifolius s.l. (J. Hall), Haddingograptus oliveri (Boucek), Bergstroemograptus crawfordi (Harris), Tetragraptus cf. T. erectus Mu, Geh & Yin, and Kalpinograptus spp. (nov?). Newly described taxa are Pseudotrigonograptus ? ricardo sp. nov., and two (possibly more) reteograptids. The initial allochthonous incursion (Unit H-1; = Cocalico Formation ?) into the foreland carried a synorogenic piggyback basin of mid-to-late Nemagraptus gracilis Zone turbidites (Unit M-1). Emplacement was upon the Hershey/Myerstown Formation deposited during earliest regional foreland subsidence. Emplacement of allochthonous Unit H-2 followed which was covered by foreland Unit M-2 (late Climacograptus bicornis Zone), containing allochthonous fragments. The foreland basin then spread laterally over the Jacksonburg Formation and equivalent "basal limestones" as Unit M-3 (Martinsburg Formation. s.s.) during Dicranograptus clingani time. The Hamburg succession (= Dauphin Formation) contains basin sediments deposited within the Octoraro Sea adjacent to the northern fringe of the microcontinent "Baltimoria". Late Cambrian through Early Ordovician age rocks are composed of quartzfeldspathic, micaceous strata overlain by phosphorites, and covered by a black shale and quartzose-ribbon limestone package; lower to middle Arenig rocks are mostly starved clastic hemipelagites. After a biostratigraphic gap of 3-4 graptolite zones those rocks were incorporated into a Middle Ordovician, trench-origin olistostrome, formed as the Octoraro Sea closed, and co-occur with turbidites, distal pelagites and extrusive/intrusive volcanics.

This PhD project documents processes controlling the generation, evolution and preservation of intracontinental transpressional basins, one of the least understood major basin types. Field data were collected in three actively deforming transpressional basins along the eastern margin of the Mongolian Altai. The Mongolian Altai is an active intracontinental mountain range comprising discrete ranges, uplifted by outward-directed thrust and oblique-slip faults linked to regionally extensive, dextral strike-slip faults. Between ranges numerous transpressional basins exist in various stages of their evolution. Thus the Mongolian Altai is an excellent natural laboratory for studying the origin and development of intraplate transpressional basins. Analysis of Landsat TM imagery allows the identification of five interlinked sediment accumulation sites which control modern sediment transport, deposition and storage within the Altai region. At present, small sediment volumes exit the Mongolian Altai and the most significant sediment sinks are range flanking transpressional basins such as the Dzereg, Dariv and Shargyn basins. In these basins, strata are uplifted, deformed and exposed by active faulting and folding in internal zones and along internal zones and long basin margins. Mesozoic strata are confined to an elongate trough coincident with Cenozoic basins, suggesting Cenozoic basins are reactivated older depocentres. The upward fining and asymmetric thickness distribution of Mesozoic strata, and the presence of interpreted Mesozoic normal faults, suggest that the basins formed during Mesozoic extension or transtension. Transpressional reactivation of the Altai began in the Oligocene, presumably in response to the distant Indo-Eurasian collision. Cenozoic strata coarsen upward and are dominated by alluvial sediment shed from adjacent ranges. Compartmentalised uplift and erosion of basin sediments and synchronous downslope sedimentation characterise the transpressional phase of basin evolution. Transpressional basins have variable bounding fault geometries and a low preservation potential.

Understanding the metal enrichment process and rate in porphyry Cu systems (PCS) is critical to underpin the genetic model of PCS and refine the template for exploration, of which robust temporal constrain is the key. In addition, fluid evolution paths constrained by bulk analysis potentially suffer problems of contamination. Based on detailed field geology and petrographic study, this PhD thesis addresses the timescales and fluid evolution process of the world class Qulong porphyry Cu-Mo deposit, Tibet, China, by applying high precision geochronology and high spatial resolution isotope analysis. A fluid inclusion study indicates that the bulk mineralization at Qulong was deposited between 425 and 280 oC under hydrostatic pressure conditions. The depth of formation of the Qulong porphyry Cu-Mo system is estimated at ~2.7 km, which implies ~2.3 km of erosion has occurred since its formation. Zircon CA-ID-TIMS U-Pb geochronology constrains the emplacement ages of the Rongmucuola pluton, the P porphyry and quartz aplite to 17.142 ± 0.014/0.014/0.023 (analytical/plus tracer/plus decay constant uncertainty), 16.009 ± 0.016/0.017/0.024 and 15.166 ± 0.010/0.011/0.020 Ma, respectively. Molybdenite ID-NTIMS Re-Os geochronology suggests that the bulk mineralization at Qulong was deposited through multiple shorted lived pulses (~ tens of kyrs) between 16.126 ± 0.008/0.060/0.077 and 15.860 ± 0.010/0.058/0.075 Ma, with a duration of 266 ± 13 kyrs. Quartz SIMS oxygen isotope analysis indicates a periodic interplay between meteoric and magmatic fluids and continuing increase of meteoric water from ~10 to ~25 % volume percent during the ore-forming process. As a result meteoric water is invoked as the main trigger for metal deposition at Qulong. The major conclusions of this study from Qulong are supported by numerical modelling, titanium diffusion and high precision studies, and have implications for understanding porphyry systems worldwide, for example, multiple and cyclic magmatic-hydrothermal fluid pulses cooled by meteoric water are fundamental for ore formation.

The aim of this thesis has been to model small rockfalls in order to better understand where, when and why they occur. High-resolution monitoring of rock slopes has revealed clustering of rockfalls through space and time, suggesting interactions, whereby one detachment from a rock slope influences the nature of those that follow. This observation contrasts with the more conventional idea of rockfalls as time-independent, discrete events that occur in response to an identifiable trigger. As the processes that give rise to observations of rockfall clustering are not well established, this thesis takes the opportunity to bring together current understanding of the controls on rockfalls with ideas around the progressive development of failure in brittle rock in an attempt to explain these patterns. The representation of these processes at scales comparable to high resolution field monitoring has not previously been attempted. Therefore this thesis has developed an approach using numerical modelling to simulate rockfalls as spatially and temporally-dependent sequences of events, to better explain the underlying mechanisms. This study begins with the analysis of a high-resolution inventory of rockfalls, concentrating on identifying patterns in rockfall occurrence. Analyses of this data reveals patterns of rockfalls that cannot be explained by environmental conditions or local geology alone. Evidence has been collected that demonstrates that rockfalls cluster in space and time, and that through time rockfall scars grow upward and outward in a consistent manner. The results of this analysis are used to inform numerical modelling that explores the mechanics driving small rockfalls, focussing upon the impact of a detachment on the location and timing of future rockfalls. Numerical modelling of idealised rock slope sections was conducted using Slope Model and demonstrated that the timing and location of failure in a rock slope could be considered as a function of accumulated damage, represented by fracture. The results suggest that time-dependent failure and associated mechanisms of stress redistribution and damage generation are one possible explanation for the propagating sequences of contiguous failures observed. Finally, this thesis has taken an exploratory approach to modelling rockfalls through the development of a new deterministic, numerical model that simulates rockfall evolution using cellular automata. This rockfall model allows the patterns and associated underlying mechanics of small rockfalls to be explored in detail using a reduced complexity approach. Critically rockfalls are modelled in a 2.5D slope face perspective to allow both rockfalls and their effects to interact across the rock slope through time. The model operates at a relatively high spatial and temporal resolution to consider the full range of rockfall characteristics that have been observed. The outputs of the model are compared with the two-year monitoring data to address key questions regarding the competing roles of endo- and exogenic forcing on rockfall occurrence. The results of the rockfall modelling shows that a consideration of stress redistribution from small scale rockfalls and time-dependent weakening provides a possible explanation for the size distribution of rockfalls, their location and timing, and the resulting changes to slope profile form as observed in the field. This has implications for how rock slopes are monitored and modelled to determine the potential for future rockfalls to occur.

Hydrocarbon exploration in frontier regions has resulted in a series of discoveries within intra- and sub-volcanic basins along the NE Atlantic margin. The majority of these basins are blanketed by varying thicknesses of subaerial lavas and volcaniclastic sequences that form the Paleogene-aged North Atlantic Igneous Province. During Exploratory drilling in 2004, the 213/27-1Z well encountered two oil and gas accumulation with a total pay thickness of 52 metres, within the Late Palaeocene-Early Eocene aged Colsay Member sandstones within the Rosebank Field. These hydrocarbon-bearing reservoir intervals comprise numerous fluvial clastic sequences that are inter-layered between sub-aerially erupted basaltic lavas and volcaniclastic sediments. This discovery gave rise to a new hydrocarbon play concept. In this study, the sealing potential of the volcanic and volcaniclastic sequences is investigated using multi-scale subsurface datasets (with a particular emphasis on the value of high resolution borehole image logs; FMI) and field analogues from the Faroe Islands. Through the combined use of wireline logs (Bivariate cross-plots) and high resolution FMI images, the volcanic and volcaniclastic rocks in the Rosebank Volcanic Formations (RVFs) were characterised, and a detailed volcanic stratigraphic section of the RVFs was constructed, to understand how these lithologies vary vertically and laterally between wells. Bivariate cross-plots (photoelectric factor versus bulk density) indicates that there are two distinct compositions of lava flows: (a) Lava Type I is characteristic of the Rosebank Lower Volcanics, and has a higher Iron/Magnesium variety, suggesting that it was emplaced during the initial phase of volcanism; and, (b) Lava Type II is characteristic in the Upper and Lower Rosebank Middle Volcanics (RMV_U and RMV_L) and the Rosebank Upper Volcanics, and is depleted in Iron and Magnesium. The FMI images revealed that the RVFs comprise a diverse and complex suite of volcanic and volcaniclastic rocks (e.g. pillow lavas, hyaloclastite, sub-aerial lavas and inter-basaltic rocks), some of which exhibit complex diagenetic overprints produced during post-volcanic process. Detailed interpretation of FMI images and integration with wireline logs showed that the ratio of volcanic, volcaniclastic and siliciclastic rocks varied between studied wells, for example the southernmost wells in Rosebank Main (205/1-1, 213/26-1, 213/26-1z and 213/27-1Z) comprise 57-62% sub-aerially erupted pahoehoe lava, ~25% volcaniclastic rocks, and ~15% siliciclastic rocks, while the wells in northern Rosebank Main (213/27-4 and 213/27-2) comprise ~35% sub-aerially erupted lava, ~50% volcaniclastic rocks, and ~20% siliciclastic rocks. These ratios indicate that the sub-aerially erupted lavas are thinning to the North of the field. Fractures interpreted in the volcanic rocks in the RVFs mainly occur in the more brittle units, for example, in the massive cores of sub-aerially erupted lava flows. Fractures distribution in the RVFs is strongly controlled by the type of lithology (e.g. simple lava flow, pillow lava, hyaloclastite etc.), their thickness and the degree of secondary degradation and alteration they have undergone. In comparison to the Colsay reservoir intervals, the RVFs are more brittle and highly fractured and thus much more prone to fracturing during drilling. Their sealing potential decreases from southern Rosebank Main to northern Rosebank Main, predominantly because the RVFs are much thinner to the North, and contain large, connected fractures. The inter-layering between volcanic and volcaniclastic rocks in southern Rosebank Main acts as an efficient vertical seal because the volcaniclastics tend to be clay-rich and do not fracture as easily. In terms of sealing potential, all the RVFs except RMV_U are low risk seals, suggesting that in some parts of the field, particularly in the northern most part of Rosebank Main, the Colsay 1 and 2 reservoir intervals may be connected. Evidence of faulting in the RVFs is infrequent in the FMI images, although where inferred, they tend to occur at contacts between lava and volcaniclastic rocks, usually at the transitional interface between the Colsay reservoir intervals and the RVFs. Similarly, faults were interpreted in the Ocean Bottom Node (OBN) seismic data, although they are generally small and discontinuous. It is therefore predicted that if faults are present in Rosebank, they are likely to be low-strain with minimal displacement. Integration of field analogues from the Faroe Islands with the subsurface datasets (FMI and recovered core) suggests that the majority of the fractures interpreted from the FMI images, and any possible faults within the RVFs, are likely to be sealing. Vein infill at the studied outcrops indicate that cementation rates were low, and therefore many fractures were still potential conduits. In Rosebank, however, due to high cementation rates, most of the fractures are completely healed. This also provides a significant clue on hydrocarbon migration within the Colsay reservoirs. It is evident that none of the fractures or the volcanic rocks recovered either through full core recovery, or side-wall cores, have any hydrocarbon shows, and therefore, the fractures present in the RVFs are likely to have been completely filled, during hydrocarbon migration into the Colsay reservoirs. It is therefore suggested that, hydrocarbons laterally migrated into the Colsay sands from the sands in the Flett Basin, and because the fractures in the RVFs did not act as conduits for fluid flow, the hydrocarbons were successfully trapped within their respective reservoirs.

No description available.

Open magmatic processes, including magma mingling, fractionation and assimilation, are responsible for the diversity of magma and crystal compositions common in subduction zone settings. This thesis focuses on investigating pre-eruptive open-system processes using crystal-specific studies. Particularly, we develop calcic amphibole as a robust recorder of magmatic processes. Amphibole is a common mineral phase in water-bearing arc magmas. Its stability is a complex function of temperature, pressure, oxygen fugacity, and melt and volatile compositions. We have developed a new multiple regression analysis of published trace element partitioning data between calcic amphibole and melt. We are able to retrieve statistically significant relationships for REE, Y, Sr, Pb, Ti, Zr and Nb. We also present new pressure-independent and temperature-independent empirical chemometric equations to predict melt major element chemistry from amphibole crystal compositions. This enables us to reconstruct melt chemistry from in situ analyses of amphibole in magmas and plutonic xenoliths. Linking these inverted melt compositions to the observed crystal textures allows us to make robust interpretations of magmatic processes throughout the magma plumbing system. We take the 1951 eruption products of Mt. Lamington volcano as a primary case study. Mt. Lamington is a composite volcano sitting on the Papuan Ultramafic Belt (PUB) ophiolite. The 1951 eruption produced andesitic dome lavas with numerous basaltic-andesitic enclaves and a few PUB ultramafic xenoliths. The mineralogy of the enclaves is dominated by amph+plag, similar to the andesitic lava hosts. The textures of the enclaves vary from fine-grained diktytaxitic to coarser-grained plutonic textured. We interpret this variation to result from variable cooling rates in the enclave-forming magma body when it invades the overlying andesite. The diktytaxitic enclaves contain variable proportions of host-derived amph+plag antecrysts and xenocrysts of ol+sp±cpx±amph with disequilibrium textures, indicating interaction with host lava and assimilation of foreign materials, respectively. A previous study argued that the olivine xenocrysts with chromian spinel inclusions are derived from the PUB, and thus that the PUB contaminated the Mt. Lamington magmas. We demonstrate that this is highly unlikely on the basis of morphological and compositional discrepancies between PUB ol+sp and the xenocrysts. The olivines are considered to represent crystal mush fractionated from precursor(s) of andesitic and/or pre-1951 shoshonitic lavas. Their presence in enclaves represents recycling of earlier-fractionated components through magma recharge. We also revisit and bring new insights on magmatic processes shaping the Ongatiti eruption of Mangakino volcano, amphibole-bearing plutonic nodules exposed in the lavas in Grenada, and the 1991 eruption of Mt. Pinatubo. We demonstrate that reconstructed melt compositions inferred from the rims of amphiboles in pumice clasts of the Ongatiti ignimbrite are in good agreement with the matrix glass compositions. This suggests that equilibrium between the amphibole rims and melts of matrix glass compositions is achieved. The cores of amphiboles from the Ongatiti ignimbrite show large compositional variation as well as disequilibrium textures (e.g. patchy zoning, resorption/dissolution texture), and the predicted melt compositions also display large variations. We interpret that these variations may be due to different degrees of equilibration of the amphiboles derived from crystal mushes with evolved melts over a range of timescales. This interpretation is an alternative to the model provided by an earlier study which instead suggests that source heterogeneity is a major contribution to the crystal chemical diversity in the Ongatiti ignimbrite. For amphiboles in plutonic nodules in Grenada lavas, we are able to predict the melts compositional variations from amphiboles in clinopyroxenite, hornblendite and hornblende gabbro xenoliths, in consistency with melt inclusions hosted in those cumulates. We interpret that the variations may be a result of in situ melt evolution due to extensive crystallization of the cumulate mineral phases, or equilibration of cumulate fragments with later evolved melts. Bimodal amphibole populations and hence inferred melt compositions in Mt. Pinatubo indicate magma mingling process, in consistency with conclusions of earlier studies. The inferred melt trace element compositions from bimodal groups also record co-crystallization of plagioclase, ilmenite, zircon and apatite together with amphiboles to varying extent, and the interpretation can be generally supported by petrography evidences.

The continuity of the Kalahari Copperbelt (KCB) beneath the Cenozoic cover of the Kalahari Group in central eastern Namibia has long been assumed, but was only confirmed by exploration drilling in 2010 when Eiseb Prospecting and Mining (EPM) uncovered Ag-bearing Cu sulfide mineralisation comparable to that found elsewhere in the belt. The geology of this region has not been described in any detail in the literature to date. Zircon geochronology suggests that sedimentation of the Eiseb started at ~1170 Ma. An uplifted basement horst of deformed acid volcanics marks the western edge of the Eiseb. There is no eastern border to the Eiseb, which extends into the Ghanzi-Chobe Belt of Botswana. Deformation and folding of the belt occurred during the Pan African Damara Orogen which peaked at ~530 Ma. Cu-Ag mineralisation is disseminated across a range of rock types, from the volcanic basement horst, to sandstones and argillites. Mineralisation also occurs in veins, often discordant to stratigraphic boundaries, and within the coarse laminae of interbedded siltstones. The preservation of delicate sulfide replacement textures of evaporite minerals in micro-folded rocks suggests that the mineralisation is largely epigenetic, favouring pressure shadows and foliation on a local scale, and fold-closures, faults and thrusts on a regional scale. Magnetite is commonly associated with with Cu-Ag mineralisation both textually and spatially, across a range of rock types. Paleomagnetic methods were unable to constrain the timing of magnetite growth. The trace element contents of magnetite, as deduced by laser ablation inductive coupled plasma mass spectrometry (ICP-MS), is able to distinguish between barren and Cu-Ag mineralised host-rocks using element ratios. The V vs. Ni binary plot is effective for the acid volcanic rocks, and the V vs. Co plot distinguishes between mineralised and un-mineralised sedimentary rocks. Magnetite trace element concentrations show that it formed from hot (150-250˚C) metalliferous fluids with an IOCG (iron-oxide-copper-gold) affinity. The most likely mechanism for magnetite formation is by replacement of pyrite, with textures suggesting this occurred during deformation, i.e. during the Damara Orogeny. The syn-deformation, epigenetic Cu-Ag mineralisation recognised in the Eiseb has been reported from numerous other deposits traditionally classified as ‘sediment-hosted stratiform copper’ (SSC). In these deposits mineralisation has been shown to be coeval with regional plate movements and orogenesis, which is fundamentally different to the SSC model where mineralisation is related to diagenetic processes. An alternative mineralisation model is thus proposed, orogenic-sediment-hosted-copper (O-SSC).

The island of Malaita in the Solomons Islands represents a unique opportunity to study the deeper portions of the largest oceanic plateau discovered to date - the Ontong Java Plateau (OJP). Malaita exposes several kilometres of Cretaceous OJP lavas, stratigraphically named the Malaita Volcanic Group (MVG), within en-echelon inliers. Most of the lavas have suffered low-grade (brownstone facies) metamorphism. The MVG basalts are low-K tholeiites, displaying a limited range of major and trace element concentrations, consistent with the lavas being well mixed prior to eruption, probably in shallow level magma chambers. However, two distinct groups, Type A and Type C-G, can be identified from their rare earth elements (REEs), platinum group elements, Sr and Nd radiogenic isotopes, indicating that mixing has not effectively wiped out all source-related and melting signatures. The MVG basalts were formed by extensive melting, mostly within the spinel Iherzolite field as indicated by their chrondritic REE patterns, suggesting a ridge-centred eruption. However, melting in the MVG's source started within the garnet Iherzolite field, consistent with a thermal anomaly such as a decompressing mantle plume. Paradoxically for a ridge centred plume, the MVG erupted in a deep submarine environment, when the elevation caused by a surfacing plume would surely imply a subaerial eruption environment, such as seen in Iceland. In addition, the MVG's overlying sedimentary sequence implies a history of uplift, rather than that of subsidence which would be expected as the plume wanes or crust is transported away. The OJP plume was probably heterogeneous, consisting of enriched (HIMU) streaks in a depleted matrix. This depleted component is thought not to be entrained upper MORB material, but a depleted component intrinsic to the plume itself, possibly entrained as the plume ascended through the lower mantle.

That there are a number of distinct ophiolitic belts separating some of the major tectonic zones of Greece and the eastern Mediterranean is generally well known. These have previously been interpreted as the remnants of back-arc basins, Mesozoic rifts, and supra-subduction zone type ophiolites. However mafic and ultramafic rocks present in the region of the Serbo-Macedonian Massif, northern Greece, do not appear to fit this model, and have generally been neglected in tectonic interpretations. The aim of this study is to determine how these bodies arrived at their current position, what is their true nature, and how do the answers to these questions help in the interpretation of the way that this section of continental crust was assembled. A multidisciplinary approach was taken to this problem. Structural and tectonic measurements and observations led to the conclusion that the main mafic and ultramafic bodies were accreted into the continental crust via a process of subduction accretion. Further to this, the continental crustal material between the main complexes is composed of tectonic melange material and not microcontinental fragments derived from the northern margin of Gondwana. A geochemical investigation of the Vavdos and Volvi Complexes demonstrates that the origin of these generally depleted lithologies was from a plume source, Volvi being thought to be a seamount, and the Vavdos Complex and associated along strike units, thought to be the disrupted remnants of an oceanic plateau. These conclusions have required the re-interpretation of current tectonic models for the region, and a new model is presented at the end of the thesis.