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This thesis details the analysis of experimental compaction and measurements upon natural samples to quantify the relative roles of mechanical and chemical processes during porosity loss in mudstones and shales, whilst understanding the concepts behind their behaviour at the pore-scale. The primary controls on the mechanical mechanisms observed are effective stress above the previous maximum, temperature and time. Mechanisms include grain packing/compression and rotation to produce minor fabric development and also thermal hardening. Effects of these mechanisms are quantified in Chapter 3, "Laboratory Simulation of Mudstone Compaction". This work program included extended duration triaxial experiments, testing the results of high effective stresses (max. 50MPa) with varied fluid chemistries and temperatures on compaction behaviour. Primary controls on chemical mechanisms are again stress, temperature and time with the addition of fluid chemistry. The mechanisms include the effects of chemical alteration such as potassium exchange and dehydration, but also the effects of full mineralogical transformation such as the ordering associated with illitization and the proposed link to higher degrees of alignment of phyllosilicates. This is covered in both Chapter 3 and Chapter 4, "Mudstone Compaction in Nature: Malay Basin Case Study", a study to characterise both the chemical/mineralogical and physical properties of fine-grained clastics from 'a region where chemical processes would be expected to be enhanced. Other processes in addition to lithology dependant degrees of packing and rotation associated with increased effective stress are not generally incorporated in porosity reduction calculations. Their inclusion may be necessary in more challenging regions such as the Malay Basin.

The eruptive rocks of the Nama Plateau are divided into : (i) kimberlites, (ii) carbonatitic dykes, (iii) monticellite peridotite and (iv) rocks belonging to the Brukkaros complex. The Gibeon kimberlite province contains at least 46 pipes and 16 major dykes of mainly basaltic kimberlite. The inclusions in kimberlite are divided into : (i) cognate nonomineralic nodules consisting of kelyphitized titanium-bearing pyrope, coated diopside, serpentinized olivine, coated ilmenite, and composite ilmenite-encased olivines; and (ii) accidental polymineralic nodules consisting of garnet peridotite, garnet pyroxenite, retrograde eclogite and granulite. The large phreatic volcano - Gross Brukkaros- is formedby a dome of Nama sediments. The centre of the dome contains depression, 1 1/2 miles in diameter, underlain by fine grained clastic rocks (microbreccias) derived from brecciat –tion of the Nama sediments. It is surrounded by 45 satellite vents and numerous radial dykes, both filled with coarse breccias 1n a carbonate-rich matrix. An outcrop of a monticellite peridotite occurs in a vent 3 miles south of Mt. Brukkaros. It is concluded that: (1) kimberlites are formed by zone refining of a magna derived from a very deep source in the mantle in places beneath very stable areas of the crust (cratons and platforms), and (ii) kimberlite may develop a volatile-rich carbonatitic top fraction, which under certain circumstances causes phreatic explosions (as happened in the case of Mt. Brukkaros). The top fraction, depleted of volatiles, is represented by a monticellite peridotite.

In practical circumstances the bulk of the rock material beneath a foundation, in the surrounding regions of an excavation, or inside mine pillars is in fact triaxially loaded over long time periods. It was felt that studying the creep phenomena of some evaporite rocks under a triaxial system of loading could add valuable information to the limited knowledge avail- able on rock behaviour in such conditions. Gypsum and anhydrite were initially chosen as suitable evaporite rocks for carrying out this work. An apparatus has been designed and constructed to enable experiments to be carried out on the chosen rocks. The axial strain of the deformed rock specimen was measured on the rock specimen inside the pressure cell. Triaxial compression creep tests were carried out at 10,20 and '30 N/mm2 confining pressure. Bending and uniaxial compression creep tests were also performe-: 1 on the chosen rocks. Instantaneous strengths of gypsum and an- hydrite under the given systems of loading were found and various percentages of the instantaneous strengths were applied in the creep tests. All short term and creep tests were carried out at room temperature. It was found that the creep behaviour of the tested rocks obeyed the following equations: Z=A+B logt and/or E= ctn, The effect of varying axial stress, confining pressure and differential stress on the creep behaviour of the tested rocks was observed and studied. A method for determining the safe creep stress, at any confining pressure, was suggested depending on the creep data available.

The study area is situated within the South-West Swedish Province (SWSP), which forms part of the Precambrian Baltic Shield. The SWSP is separated from the Svecofennian Province, in the east, by a major suture, the Protogene Zone, and a major belt of sialic igneous rocks, the Trans-Scandinavian Igneous Belt. The SWSP is generally considered to have had a different petrogenetic history from the neighbouring Svecofennian Province, at least for part of its Precambrian development. The SWSP is transected by a major zone of mylonitization which divides it into Northern and Southern Segments, which differ in petrology and geological development. The whole of the SWSP show overprinting by the effects of the younger Sveconorwegian Orogeny.Research was concentrated to the immediate north and south of the dividing Mylonite Zone, close to the town of Varberg. The southern rock unit is known locally as the Varberg Formation and the northern rock unit as the Bua Formation. Outcrop density along the coastal strip is good to fair.It was believed that examination and interpretation of the metabasic rocks of the region might prove valuable in establishing the petrogenetic development of the region. This research has discriminated three distinct groups of metabasic rocks; differeing in their field characteristics, petrologies, petrochemistries, mineral chemistries and petrogeneses. These are referred to as the metabasic rocks of Groups I, II and III respectively.The metabasic rocks of Group I have had their origin in basic igneous activity which occurred prior to, or during, the early orogenic activity which established the fundamental character of the Varberg Formation rocks; the Varberg Orogenic Event. The geochemical data suggest that these metabasic rocks are derived from a suite of basic igneous rocks, probably largely minor intrusions, which relate to a parent magma which was tholeiitic in type. Orogenic intrusion is indicated, perhaps in an island arc environment. These basic intrusive rocks appear, from their field relationships with their country rocks, to have undergone the same range of deformations and metamorphisms as their hosts.The metabasic rocks of Group II have had their origin in basic igneous activity which post-dates the Varberg Orogenic Event, during a period of anorogenic magmatism (the Varberg Thermal Event). The geochemical characters of these rocks indicate their development from a tholeiitic parent magma in a continental rift environment. Protometamorphic development of garnet amphibolites synchronous with emplacement of these intrusions is indicated by their mineralogies and petrographies. They were subsequently in part metamorphosed to garnet pyribolites, on reversion to orogenic conditions (Sveconorwegian Orogeny). The rocks of Group II are largely concentrated within the Varberg Formation, with impounding against the discontinuity separating the Sua and Varberg Formations. There was, however, some leakage into the Bua Formation. Acid plutonism also occurred with, and was genetically related to, the basic magma influx during the Varberg Thermal event. The granitic products were also largely impounded at the BuaNarberg interface, but with some transgression. Both the basic and the acid igneous units were involved in thrust reworking of the interface zone (the Mylonite Zone), with local retrogression to amphibolite facies.The metabasic rocks of Group III are unrelated to either the Group I or Group II magmatic episodes and occur only within the Bua Formation. They are divisible into two sub-groups; Group iliA, with chemical affinity with low-K tholeiites of the island arc environment, and Group IIIB, comparable with continental rift basalts. The Group iliA rocks include metapyroxenite; brecciated and intruded by scapolite gabbro. This juxtaposition of deep level accumulate characters and high level, gas-charged brecciation can probably be linked with major tectonic translation, perhaps related to the Hallandian Orogeny. The metamorphism of the basic rocks is linked with, and forms an integral part of, the petrogenetic history of the Bua Formation.The igneous and metamorphic histories revealed from this study of the metabasic rocks of the Varberg region provide useful strictures in any interpretation of the geological development of the South West Swedish Province. The separate development of the Southern and Northern Segments is confirmed. The early development of the Varberg Formation seems also distinct from its now neighbouringmSvecofennian Province. The following petrogenetic development model is proposed, which allows for the fresh information obtained from the region:1) Development of the crustal segment represented by the Varberg formation in an early orogeny affecting the Group I igneous rocks (The Varberg Orogeny).2) Separate development of the Sua Formation sequences.3) Conjunction of the Sua and Varberg Formations during orogenic activity (The Hallandian Orogeny; c. 1600 my), such that the Bua Formation metamorphic rocks form a cover sequence to the Varberg Formation. This was preceded by the docking of the deeply-eroded, Varberg Formation, continental block against the Svecofennian Province (c. 1750 my).4) A period of crustal extension, petrological underplating, magmatic intrusion, crustal heating, volatile migration and acid plutonism affecting the composite crustal segment(The Varberg Thermal Event; c. 1400 my).5) Renewed orogeny (The Sveconorwegian Orogeny; c. 1000-900 my).

The Circum-Superior Large Igneous Province (LIP) consists predominantly of ultramafic-mafic lavas and sills with minor felsic components distributed as various segments along the margins of the Superior Province craton. Ultramafic-mafic dykes and carbonatite complexes of the LIP also intrude the more central parts of the craton. Most of this magmatism occurred at ∼1880 Ma. New major and trace element and Sr-Nd-Pb-Hf-Os isotopic data reveal that the segments of the Circum-Superior LIP can be treated as a single entity formed in the same tectonomagmatic environment. In contrast to most previous studies, the Circum-Superior LIP is interpreted to have formed from a single mantle plume and this is consistent with the high MgO and Ni contents of magmas, oceanic-plateau-like incompatible trace element profiles, ocean-island-like positive Nb-Ta anomalies, Icelandic plume-like Nb/Y and Zr/Y ratios, oceanic-plateau-like Zr/Nb and Nb/Th ratios and Nd-Hf isotopic compositions which differ from that of the estimated depleted upper mantle at ∼1880 Ma. Further support for a mantle plume origin comes from calculated high degrees of partial melting, high mantle potential temperatures and the presence of a radiating dyke swarm. The location of most of the magmatic rocks along the Superior Province margins probably represents the deflection of plume material by the thick cratonic keel toward regions of thinner lithosphere at the craton margins. There is no obvious geochemical distinction between segments of the Circum-Superior LIP which host ore deposits and those which do not. The geochemistry of the Circum-Superior LIP differs markedly from that of other ∼1880 Ma igneous provinces on other cratons which questions the validity of the formation of a very large LIP and the occurrence of a superplume event at ∼1880 Ma.