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The mineral ilmenite (FeTiO3) is an important component of heavy-mineral placer deposits and constitutes the largest volume of valuable mineral in such deposits. The minerals zircon (ZrSiO4) and rutile (TiO2), which occur in lower concentrations than ilmenite in the deposits, have a greater value per ton – c. 1100 and 900 $/ton respectively – compared to ilmenite that ranges from 100 to 200 $/ton depending on its composition. Other minerals such as staurolite, sillimanite, amphibole and garnet are generally also present in placer deposits, but are of minor or no commercial value and, e.g. amphibole needs to be separated from the valuable heavy minerals which adds to the production cost.

The mineral rutile (TiO2) is a major ore of titanium, which is used in products such as white pigment and titanium metal. The global consumption of titanium minerals in 2011 was c. 6.7 million tonnes of which 0.7 million tonnes were rutile and 6 million tonnes ilmenite (TiFeO3). Rutile is almost pure TiO2 and therefore more valuable than ilmenite (c. 1500 $/t and 300$/t, respectively). Compared with ilmenite, rutile can be processed with lower consumption of chemicals and yields less waste products. Rutile was mined in Cameroon between 1935 and 1955 when a total of 15 000 tonnes of rutile were extracted from alluvial deposits. The French Bureau de Recherches Géologiques et Minières conducted a drilling programme in Cameroon in the 1980s which identified c. 2.6 million tonnes of rutile in discontinuous occurrences with concentrations of c. 1%. Most of the occurrences are located in small- to medium-sized riverbeds with a thickness of 1.5–4.5 m. The main alluvial rutile area is located around the town of Akonolinga, 80 km east of Yaoundé, the capital of Cameroon (Fig. 1). The rutile in the alluvial deposits was derived from the bedrock by weathering, and at some sites major, residual rutile deposits are reported from Quaternary lateritic deposits. The Geological Survey of Denmark and Greenland conducted a project together with the Institut de Recherches Géologiques et Minières in Cameroon to gain a better understanding of how rutile formed in the bedrock before it was weathered out and try to tie the rutile in the alluvial deposits to its source rocks. This is done by studying the compositional variation of the rutile in the alluvial deposits and comparing it with possible bedrock sources. The compositional variation of ilmenite and monazite ((La,Ce)PO4)) and the age distribution of zircon (ZrSiO4) in alluvial sand and bedrock were also investigated. The chemical compositions of minerals in the sediments are used to infer the bedrock source of the minerals. This has particular application in many areas of Cameroon, such as the southern part of the country which is characterised by low relief and dense rain forest with bedrock outcrops that are sparse and difficult to find. Cameroon is a country in west central Africa (Fig. 1) and is called ‘Africa in miniature’ because of its cultural, geological and landscape diversity. The landscape includes beaches, deserts, mountains, rain forests and savanna. The highest point is the active volcano Mount Cameroon (4095 m), and the country is home for over 200 different linguistic groups with French and English as the official languages. Compared with other African countries, Cameroon is politically and socially stable. The country covers an area of 475 442 km2 with a population of c. 20 million of which 70% are Christians and 20% Muslims.

For the characterization of sediments, Computer Controlled Scanning Electron Microscopy (CCSEM) is a powerful method in obtaining chemical data on individual mineral grains and modal analysis of the heavy mineral fraction of sediment samples. Here we show how the CCSEM method can be used to evaluate ilmenite ore grade as well as a tool to investigate the source of heavy mineral deposits. The heavy mineral rich deposits in beach sands around the town of Chavara in SW India are characterized by ilmenite with elevated TiO2 contents, often exceeding 60 wt.%. In order to determine the origin of these high-TiO2 ilmenite deposits, we collected a series of beach sediment samples (22) from a c. 800 km long stretch of coastline from northern Kerala state to well within the Tamil Nadu state. A set (7) of river sediments was also taken, roughly covering the catchment area to the beach samples. The data show that the sediments in the Chavara high-Ti ilmenite deposit are distinguished by minor elements in ilmenite, garnet chemistry and heavy mineral assemblage: Chavara ilmenite has high MgO and low MnO contents; garnets have low grossular components and the heavy mineral assemblage is dominated by sillimanite–kyanite in addition to ilmenite. These features correlate with basement geology in the hinterland, and with sediments from rivers, draining the basement. Based on these observations we conclude that high-Ti ilmenite from Chavara beaches originates in the khondalite belt of high-grade metasediments. Our study demonstrates rapid mineral analyses in sediments by CCSEM to be efficient in the characterization of mineral compositions and assemblages in sediments, in the identification of possible source regions and thus ultimately in exploration for industrial mineral resources.

New techniques using Computer Controlled Scanning Electron Microscopy (CCSEM) and Laser Ablation – Inductively Coupled Plasma – Mass Spectroscopy (LA-ICP-MS) have recently been developed at the Geological Survey of Denmark and Greenland (GEUS) to determine source, compositional variation and sedimentary pathways of sandstones. These new time- and cost-efficient methods are highly applicable in petroleum and mineral exploration. This paper illustrates how the provenance and variability of Miocene titanium-rich sands in western and central Jylland have been investigated, but the methods are presently also used offshore the Faroe Islands and in East and West Greenland. CCSEM and LA-ICP-MS utilise simple sample preparation methods, are relatively rapid and less expensive than conventional methods and yield more information.

MISSISSIPPI Valley type (MVT) ore deposits in North America are generally thought to have formed from warm brines which migrated from sedimentary basins to sites of deposition in sedimentary strata of the neighbouring craton long after Unification of the sediments1–3. When and how these migrations occurred is not well understood, but recent geological evidence suggests that continental-scale brine migration can be triggered by tectonic collisions4–6. Indirect evidence7– 9has suggested an association of North American MVT mineralization with the Late Palaeozoic Alleghenian/Ouachita orogeny; recently, however, Nakai et al.10obtained a Rb-Sr age of 377±29Myr for sphalerites from the East Tennessee MVT district, which they linked to the Middle Palaeozoic Acadian orogeny. Here we report Rb-Sr dates for sphalerites from the MVT 'type section' - the Upper Mississippi Valley (UMV) zinc-lead district. Rb–Sr data from two distinct sphalerite bands from the West Hayden ore body yield two independent but indistinguishable isochrons of Permian age (269 ± 6 Myr and 270 ± 4 Myr), consistent with a brine migration episode initiated by the Alleghenian/Ouachita orogeny. In conjunction with the previous data indicating a link to the Acadian orogeny10,11, our results indicate that North American MVT deposits formed in at least two distinct tectonic episodes.

Luminescence microscopy is used to identify stages of cementation in petroleum reservoirs and classify the physical and chemical properties of oils and oil inclusions. The lifetime of fluorescence induced by a pulsed laser is related to the API gravity of oil and can be used to determine API gravity on microliter samples of oil or oil in inclusions. Luminescence microscopy data are combined with geological (burial history, stratigraphy, tectonics, environment of deposition) and geochemical (fluid inclusion P-T-X values, stable isotopes, trace elements, petroleum geochemistry) data to determine the timing of geological events and constrain models of diagenesis, oil migration, and reservoir prediction. This method is applied to studies of reservoir diagenesis and petroleum maturation, migration, and correlation for the Mishrif Formation, Dubai, the Kais Formation, Indonesia, the Ellenburger Dolomite, Texas, and the Great Oolite Limestone, England. In the Great Oolite Limestone, cathodoluminescence of cements shows that occurrence of zoned cements correlates with high reservoir porosity consistent with a model of porosity perservation resulting from diagenesis in a mixing zone between freshwater and marine phreatic environments. Photoluminescence of oil inclusions in cements of the Great Oolite shows that inclusions are more mature near the basin depocenter. In the Ellenburger Dolomite, Texas, several episodes of fracture development and sealing are shown by cathodoluminescence enabling a relative timing to be determined. Temperature and composition data from fluid inclusions are collected with respect to the cathodoluminescence and used toquantify the environment of cementation.

Fluid inclusions can be used to interpret thermal history and petroleum maturation and migration relative to burial history. Temperature, pressure and composition data collected from fluid inclusions are used to determine the environment of diagenesis and the timing of cementation and migration. Cements in petroleum reservoirs contain both oil and aqueous fluid inclusions. Fluorescence spectroscopy is used to identify oil inclusions and to determine the maturity of entrapped oil. The lifetime of fluorescence induced by a pulsed laser is related to the API gravity of entrapped oil. Interpretation of fluid inclusion data depends on knowing the origin of fluid inclusions and the probability that they survive in the burial environment. Those aspects of fluid inclusion study are investigated by synthesizing oil and aqueous inclusions in calcite crystals in laboratory experiments. Examples of how fluid inclusions are used to determine the physico-chemical environments of diagenesis in petroleum reservoirs and the timing of cementation and migration are given for the Wealden Basin, England, the Mishrif Formation, Dubai, the Smackover Formation, Gulf Coast, U.S.A. and Jurassic sandstones, offshore Norway. In the Wealden Basin, temperature data from fluid inclusions are used to determine that oil migration occurred in the Cretaceous and that the reservoir rocks have been uplifted to varying degrees at a time after migration. Distribution of oil inclusions indicates that generation and migration of oil was principally in the western part of the basin. The geochemistry of oil inclusions in calcite cements from the Mishrif Formation, Dubai, are used to determine the type and maturity of entrapped oil. Temperature data from oil and water inclusions are used to relate reservoir diagenesis to burial history and the migration of oil. In deep Smackover reservoirs oil contains H 2 S. The origin of the H 2 S is examined by study of fluid inclusions containing H 2 S. In Jurassic sandstones, offshore Norway, fluid inclusion studies show that silica cementation is related to burial depth whereas a later calcite cementation originated from invasion of a hot fluid.

Rudist reef associated limestones comprising the Cretaceous Mishrif Formation are the major reservoirs in Fateh field, a giant oil field in offshore Dubai. In this study, Mishrif cores from four wells on the western flank of the field were examined to gain insights into the depositional, diagenetic, thermal, and maturation histories of the Mishrif Formation in this area. The wells lowest on the west flank contain relatively deep-water, lower fore-reef facies bounded by two erosional unconformities. The upper unconformity marks the Laffan-Mishrif contact and extends over Fateh field throughout the region. In Fateh field, the lower intra-Mishrif unconformity has been identified only on the western flank, but is probably present in other locations low on the Fateh structure. The identification of the lower unconformity indicates two cycles of Mishrif sedimentation. The cycles are related to deep-seated salt movement and epeiric sea level changes. Fluid inclusion data, maturation calculations, and burial history modeling indicate that the timing of cementation by blocky calcite spar and oil migration were approximately synchronous and occurred during the Oligocene to Miocene.

Oil is produced from the Middle Jurassic Great Oolite Limestone in the western Wealden basin, England. Additional production was discovered (150 STBOPD, 42° API) in 1986 at the Conoco 1 Storrington well. The Storrington discovery is of note because the porosity in reservoir grainstones and packstones is largely primary and averages 19.4%, the highest value yet found for the Great Oolite. Secondary porosity is of little significance. For all wells studied, porosity in Great Oolite grainstones and packstones ranges between 3 and 20%, and there is no relation between porosity and lithology. Locally, porosity may be largely occluded by coarse calcite spar, which fluid inclusion studies show precipitated in the deep-burial environment. Exploration in the Great Oolite, the efore, must seek diagenetic fairways wherein primary porosity has been preserved. Limestones in the producing interval of the Great Oolite at 1 Storrington contain zoned syntaxial cements, are generally high in magnesium content, and have stable isotope compositions that indicate the involvement of marine waters (relatively heavy ^dgr18O). Our interpretation is that the limestones were stabilized early in a mixing zone between freshwater and marine phreatic environments. Coarse calcite spar in the Great Oolite contains aqueous and oil inclusions. The results of geothermometry studies show that the precipitation of calcite cements occurred at depth, near maximum burial, and, at certain locations, was synchronous with oil migration. Inversion of the basin was a later event. The construction of burial history diagrams that incorporate fluid inclusion and maturation data shows that oil migration was during the Late Cretaceous. A distribution pattern for oil inclusions in the Great Oolite indicates migration was mainly in the western part of the basin and initially into pre-Late Cretaceous traps.

In the following we describe the result of the Titan Project, an interactive web application (Titan) developed at the Geological Survey of Denmark and Greenland (GEUS) together with DuPont Titanium Technologies. The main aim of Titan is to make computer-controlled scanning electron microscopy (CCSEM) data, generated at GEUS, available via the internet. In brief, CCSEM is a method automatically to detect particles with a scanning electron microscope (SEM), and based on computer-controlled imagery to measure the chemistry and grain morphology of each particle in a given sample (Knudsen et al. 2005; Bernstein et al. 2008); Keulen et al. 2008. Titan makes data available on-line so that the user can interact with the data sets and analyse them using a web browser. In addition to CCSEM data, Titan contains a global database of titanium deposits and various reports. The web application is customised, such that the functionality and amount of data available for a given user depend on the privileges of that user.