In comparison to sandstone reservoirs, carbonate exploration is commonly more challenging because of intrinsic heterogeneities, occurring at all scales of observation and measurement. Heterogeneity in carbonates can be attributed to variable lithology, chemistry/mineralogy, pore types, pore connectivity, and sedimentary facies. These intrinsic complexities can be related to geological processes controlling carbonate production and deposition, and to changes during their subsequent diagenesis. The term 'heterogeneity' is rarely defined and almost never numerically quantified in petrophysical analysis although it is widely stated that carbonate heterogeneities are poorly understood. This work has investigated how heterogeneity can be defined and how we can quantify this term by describing a range of statistical heterogeneity measures (e.g. Lorenz and Dykstra-Parsons coefficients). These measures can be used to interpret variation in wireline log data, allowing for comparison of their heterogeneities within individual and multiple reservoir units. Through this investigation, the Heterogeneity Log has been developed by applying these techniques to wireline log data, over set intervals of 10, 5, 2 and 1m, through a carbonate reservoir. Application to petrophysical rock characterisation shows a strong relationship to underlying geological heterogeneities in carbonate facies, mud content and porosity. Zones of heterogeneity identified through the successions show strong correlation to fluid flow zones. By applying the same statistical measures of heterogeneity to established flow zones it is possible to rank these units in terms of their internal heterogeneity. Both increased and decreased heterogeneity is documented with high reservoir quality in different wireline measurements, this can be related to underlying geological heterogeneities. Heterogeneity Logs can be used as a visual indicator of where to focus sampling strategies to ensure intrinsic variabilities are captured.

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North Pakistan represents a highly favourable area for a variety of mineral deposit types, including arc-related porphyry Cu, Au and Mo and arc and backarc epithermal precious metal deposits (Sweatman et al., 1995; PMDC, 2001). However, few deposits have been discovered in the area, mainly due to its remote nature and inaccessibility, and because of a lack of exploration tools for high altitude terrains. From stream sediment sampling campaigns by local and international organizations, including a large dataset provided by the Pakistan Mineral Development Corporation (PMDC), a significant amount of geochemical data now exists for the region. This data has been incorporated into an Arc-GIS 9.2 database, along with stream catchment and geological information, and detail of all known areas of mineralisation. From this, spatial catchment maps together with multi-element geochemical associations have been studied to delineate areas showing anomalous values for Au and base metals. The two most prospective areas were found to be the Shyok Suture Zone and northern Kohistan, with the dominant control on mineralisation being structural rather than lithological. These areas were targeted for detailed stream sediment sampling and mineralogical and geochemical analysis. From studies of Au and Au pathfinder elements in different size fractions of the stream sediments and heavy mineral concentrates (HMC), the catchments of Teru, Asheriat and Pakora (in order of decreasing rank) were identified as most prospective. Morphological and geochemical analyses of native Au grains from panned concentrates has given an indication of proximity to bedrock source (<10 km) and the possible styles of mineralisation in these catchments; porphyry Cu-type in Asheriat and Pb-Sb quartz veins in Teru and Pakora. Automated mineralogical analysis of the stream sediments (<180 µm fraction) and HMC (<180 µm), using a QEMSCANÒ system, confirmed this interpretation. The effectiveness of the developed methodologies for exploration in remote and high altitude terrains of North Pakistan is discussed, and recommendations made for future exploration.

The Lower Eocene lavas of northern and central Skye cover an area of 600 sq miles (1500 km2) and lie in a shallow, faulted oval basin with its long axis running northwest-southeast. The lavas contain an abundant population of secondary minerals including zeolites, clays, calcite and quartz. The amygdale minerals were studied at over 400 localities, the most abundant species, in order of frequency, are thomsonite, analcime, mesolite, chabazite, stilbite, calcite, laumontite, gyrolite, levyne and natrolite. Several zonal assemblages were recognised and mapped, each is named after an index mineral which it contains. With increasing depth in the lava pile the zones are : thomsonite-chabazite; analcime; mesolite; and laumontite. The original thickness of the lava pile has been reconstructed from the distribution and thickness of the amygdale mineral zones. The minerals occur in zones that are flat-lying and nearly parallel with the stratification of the lavas. Zeolitisation of a flow takes place a considerable period after eruption and not until at least a 1000 ft (300 m) of lavas has accumulated. Broadly the intensity of zeolitisation increases with depth, concomitant with increasing temperature. The secondary minerals are shown to have originated from the action of meteoric waters percolating through the basalt, dissolving some of its constituents and redepositing them in vesicles and joint planes. Bulk analyses from various flows show that there is a progressive change outwards from the interior of the flow of the Fe2O3:FeO ratio and the A12O3, CaO, Na2O, SiO2, MgO and H2O contents. These features are thought to reflect a post-consolidational redistribution of material. The overall chemistry moreover suggests that the introduction and removal of components is subordinate to a local redistribution of material. Evidence is presented to show that rock compositions (amounts of CaO, Na2O and SiO2 particularly) and the activity levels of components (aSiO2, aCaO:aNa2O) in solution exerts a strong control over the nature and composition of the secondary minerals. The lavas within the vicinity of the Cuillin intrusive complex show the effects of thermal metamorphism. Three amygdale mineral zones were recognised laumontite, prehnite, and epidote (each named after an index mineral) and appear to constitute an aureole about the complex extending outwards for an average of 4 miles (6.5 km). These concentrically arranged zones cut steeply across the lava stratigraphy and across the regional zeolite zones; and correspond to the area of O18 depletion about the central complex. The aureole probably developed at temperatures above 200 C.

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Approximately 99% of Mo is obtained from porphyry deposits (e.g. Sillitoe, 2010), representing the strongest association of any metal with a single deposit type. Despite this, the controls on the formation of Mo-rich porphyries and the spatial-temporal decoupling of Mo from Cu in these systems remain poorly understood. By combining fieldwork, Re-Os molybdenite dating and a fluid inclusion study at one of the world's largest Cu-Mo porphyries (El Teniente, Chile), this project assesses the magmatic-hydrothermal evolution of the system to help constrain the processes controlling Mo enrichment. Results indicate that deposit-wide Mo grades of < 0.06 wt.% are principally controlled by the abundance of main mineralisation-type quartz-molybdenite veins, that develop outwards and upwards into Cu-rich vein types. Parental ore fluids had low salinities (~6.5 wt.% NaCleq) and were exsolved at depth following the emplacement of multiple intrusions that acted as short-lived (< 100,000 years) conduits for mineralising fluids between 6.3 and 4.6 Ma. The decoupled deposition of Mo and Cu surrounding each temporally separate intrusion is attributed to the sequential deposition of Mo then Cu in response to decreasing temperature followed by intermittent fluid boiling and increasing fluid pH in response to sericitic alteration of the mafic host-rocks. Mo grades > 0.06 wt.% correspond to the presence of late mineralisation-type veins and breccias produced by the exsolution of Mo-rich brines ±aqueous fluids from a highly fractionated magma source. Mineralisation in this stage was short-lived and occurred in all parts of the deposit at ~4.6 Ma. The relatively Cu-poor nature of this stage is attributed to the prior preferential extraction of Cu from the underlying magma chamber in earlier mineralising events. In accordance with data from other Mo-rich porphyry systems, results indicate that Mo-Cu decoupling is controlled by both changes in magma chemistry as well as by the evolving P-T-X properties of hydrothermal fluids.

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Non-condensed structures in vitrinites and sporinites, prepared from high- to medium-volatile bituminous coals, have been studied both by extraction and degradation. Additionally, seven concentrates of alginites, resinites and cutinite were studied. Analyses of extractable vitrinite and sporinite alkanes showed that their yields increased markedly between 83.3% and 83.9% C vitrinite (d.a.f.), and reached maximum values at 85.4% Cvitrinite (d.a.f.)n-Alkane distributions showed increasingly lower average molecular weights with increasing rank, and the CPI's (n-C23 to n-C33) decreased to almost unity at 83.9% Cvitrinite (d.a.f.). This occurred while individual homologues progressively increased in concentration. Pyrolytic and oxidative degradation of the extracted and saponified maceral residues showed that n-alkyl chains with more than 20 carbon atoms, attached peripherally to the "kerogens", generally had even-dominated distributions. Thus, during natural diagenesis of these materials. the generation of long-chain n-alkanes showing an even-carbon-number preference may be the cause of the observed decreasing CPI values. The branched/cyclic alkanes of vitrinites and sporinites also s~owed progressive distributional changes with increasing rank, manifested by relative decreases in the yields of polycycloalkanes and increases in the yields of lower molecular weight constituents, particularly the Cl4 to C20 acyclic isoprenoid alkanes. Hopane-type triterpanes with 27. 29. 30 and 31 carbon atoms have been identified among the higher molecular weight constituents, and gc retention data suggest a remarkable constancy in the distributions of these compounds between the two macerals. Pyrolysis showed that further quantities of these compounds could be produced after extraction of the macerals. The extractable alkanes of alginites and cutinite were also composed of complex mixtures of normal and branched/cyclic alkanes, and iso- and anteiso-alkanes were identified in one alginite fraction. Resinite alkanes were unique in type, showing restricted gc distributions confined generally to the sesqui- and diterpane regions. Small yields of carboxylic acids were obtained by saponification of both extracts and residues. Fatty acids from all the macerals except resinite contained palmitic and stearic acids as prominent constituents, and, in general, the distributions of fatty acids could not be related to those of the alkanes obtained by extraction or pyrolysis. Carboxylic acids from resinites were again unique in type, and analysis of these compounds from one of the resinites has shown that they consist of diterpenoid acids, including agathic acid, pimaric acid and isomers, and dehydroabietic acid. Straight-chain, saturated ∝, w-dicarboxylic acids, with up to 28 carbon atoms, were found only in alginite and cutinite. These macerals were deposited in more fresh-water environments than vitrinite and sporinite, and the presence of dicarboxylic acids in fossil lipid mixtures may be indicative of an early phase of aerobic decomposition during diagenesis. Oxidative degradation of extracted and saponified sporinite, alginite and cutinite residues showed that polymethylene chains in the "kerogens" generally contained up to 15 carbon atoms j although chains with up to 24 carbon atoms were detected. In sporinites, the amounts decreased with increasing rank, and were scarcely detectable above ca. 85% Cvitrinite (d.a.f.). Loss of these linear structures at higher ranks may be associated with the approaching coalification break of sporinites in medium- to low-volatile bituminous coals.