Rutile Deposits Research Articles

Rutile in Amphibolite Facies Metamorphic Rocks: A Rare Example from the East Qinling Orogen, China

Rutile is an important ore mineral to meet the increasing demand of critical metal Ti in various sectors. Here we report a rare example of rutile deposits hosted within the Baishugang–Wujianfang amphibolite-facies metamorphic rocks in the East Qinling Orogen, central China. The rutiles are mostly located within or along the margins of biotite and show 94.6 to 99 wt% TiO2. Rutiles occur as chains, thin layers along the foliation, and dense clusters. The grains are coexisted with magnetite. Based on Zr-in-rutile thermometer the estimated crystallisation temperature is at 630 °C at 7.0 kba. Based on Cr/Nb ratio, the source of the rutile is correlated with Ti-bearing silicate minerals such as biotite from aluminous sedimentary protoliths. The rutile deposit formed during lower amphibolite-facies metamorphism, and is distinct from the eclogite- and granulite-related types elsewhere in the orogen. The LA-ICP-MS U–Pb analyses of rutiles from the deposit yield lower intercept 238U/206Pb ages of 386 ± 16 Ma at the Baishugang–Wujianfang district. These ages correspond to a Devonian arc–continent collisional event between the South and North Qinling domains in the East Qinling Orogen.

Mineral distribution and provenance of heavy mineral sands (zircon, ilmenite, rutile) deposits from the NW Murray Basin, far western NSW, Australia

There is significant economic interest in the Murray Basin of southeastern Australia as it is proving to be a major heavy mineral sands (HMS) province that will be one of Australia’s major source for production of rutile, zircon and ilmenite. The distribution and provenance of HMS resources in the Murray Basin is poorly understood because of its huge size, limited exploration and the complex depositional, structural and weathering mechanisms in their development. In this paper, we focus on the Copi North and Magic deposits some 130–180 km south of Broken Hill, NSW. The heavy mineral assemblages of the Copi North and Magic deposits are very similar, with the main economic minerals being ilmenite, leucoxene, pseudorutile, rutile and zircon. Intensive fracturing and brecciation are identified in many samples and are inferred to have been initially caused by multi-stage deformational processes associated with metamorphism and then further developed through alluvial and eolian transportation. Both deposits are classified as ‘medium sands, symmetrical, mesokurtic and moderately well-sorted’. The majority of economic minerals are of low to medium sphericity and subrounded, along with abundant polished eolian quartz grains. The Copi North deposit has coarser and more poorly sorted sediments with higher HMS grades and magnetics content than the Magic deposit, reflecting a higher energy depositional environment. The main source for the HMS for the Copi North and Magic deposits is largely ascribed to the Broken Hill Block. Previous studies have shown that the Broken Hill orebody underwent substantial sub-aerial weathering over hundreds of millions of years. In addition, the complex metamorphic events experienced by the Broken Hill Block were capable of forming the broad series of minerals identified within the Copi North and Magic deposits. The HMS were believed to have been transported through paleovalleys near the Mulculca Fault in a southeast direction representing a feeder system into the NW Murray Basin. Both deposits feature a relatively linear geometry (roughly parallel to the strike of the paleoshoreline), with high HMS grades, modest tonnages, and coarser sediments when compared to WIM-style offshore deposits. Compared to other strandline HMS deposits of the Murray Basin, they are smaller in size although have similar high grades of 3.7–6.9% THM and similar proportions of the HMS assemblage of ilmenite, leucoxene, rutile and zircon. Deposits of similar size and grade are likely to occur throughout the northern part of the Murray Basin.KEY POINTSBoth the Copi North and Magic deposits contain similar mineral assemblages with the provenance of the heavy minerals ascribed to the Broken Hill Block.A relatively high energy inshore environment is inferred for the Copi North deposit while a lower energy environment associated with either a foreshore or backshore environment is inferred for the Magic deposit.Deposits of similar mineralogy, grades and size are likely to occur elsewhere throughout the northern Murray Basin.

The geodynamic setting of Dulan eclogite-type rutile deposits in the North Qaidam orogen, western China

Abundant eclogite-type rutile deposits have recently been discovered along the North Qaidam ultrahigh-pressure (UHP) metamorphic belt in China. The identified titanium reserves exceed 3 million tons and range in grade from 1.0% to 4.5%. The rutile deposits of economic interest are found within two types of eclogite. However, the origin and original geodynamic setting of the two types of rutile-bearing eclogites remain controversial. This study therefore investigates ore and mineralization bodies belonging to the two types by way of detailed field work and geochronological, geochemical and Sr–Nd–Hf isotopic compositional analysis, taking the Dulan eclogite-type rutile deposit as its case study. Type-1 rutile-bearing eclogites enclosed in granitic gneisses are found to have Neoproterozoic protolith ages of 845 ± 4 Ma and an eclogite-facies metamorphic age of ca. 433 Ma. Their high TiO2, TFe2O3, and P2O5 contents cannot have been produced by rutile-formation during UHP metamorphism but could have arisen through the accumulation of ilmenite and apatite in a high-Ti protolith. They have ocean-island basalt (OIB)-like trace element patterns, with enrichment in light rare-earth elements (LREEs) and high field strength elements (HFSEs) (Nb, Ta, Zr, and Hf). The Hf isotopic compositions of the residual magmatic zircon cores in Type-1 rutile-bearing eclogites (εHf (845) = +1.4 to +6.0, TDM = 1.2–1.5 Ga) indicate that their parental magmas were derived from the Proterozoic mantle. However, they show initial 87Sr/86Sr values of 0.71059–0.71326 and εNd (845) values of −1.5 to −2.5, suggesting significant crustal contamination. Thus, the Type-1 rutile-bearing eclogites may have originated through partial melting of an OIB-type mantle plume source during the Neoproterozoic rifting of the Rodinia supercontinent. In contrast, the Type-2 rutile-bearing eclogites, which are hosted in a mafic–ultramafic ophiolitic complex, have protolith ages of 449 ± 3 Ma and eclogite-facies metamorphic ages of ca. 435–433 Ma. Correlations between the whole-rock MgO and the major and trace element contents of Type-2 rutile-bearing eclogites suggest that they are derived from cumulates with alternating olivine and pyroxene-rich and ilmenite-rich layers. They have mid-ocean-ridge basalt (MORB) and OIB-like trace element patterns, indicating extensive fractional crystallization and the possibility that there were multiple injections of magma during the formation of the protolith. Meanwhile, the +0.6 to +4.3 εNd (449) values and −1.8 to +11.8 εHf (449) values of the Type-2 rutile-bearing eclogites indicate that the protoliths may have been generated by partial melting of a mantle wedge source metasomatized by slab-derived components. The short interval (ca. 14 my) between magma generation and eclogite-facies metamorphism, in combination with the type of rock assemblage within which they are found, indicates that the Type-2 rutile-bearing eclogites originated in a supra-subduction zone (SSZ) ophiolite. Type-1 and Type-2 rutile-bearing eclogites have similar eclogite-facies metamorphic ages of ca. 435–433 Ma, indicating that the Type-1 and SSZ-related Type-2 protoliths were incorporated into a subduction mélange that was dragged down the subduction channel and underwent eclogite-facies metamorphism via subduction of the Qaidam Block, eventually forming eclogite-type rutile deposits.

Age and sources of Precambrian zircon–rutile deposits in the Kokchetav sialic massif (northern Kazakhstan)

The U–Pb geochronological data on detrital zircons from placers confined to Neoproterozoic quartzite–schist sequences, which are widespread in the Kokchetav massif of northern Kazakhstan, are discussed. Detrital zircons (332 grains in total) originate from the ore occurrences in the central, northern, and western parts of the massif. The concordant ages of detrital zircons from all the examined occurrences largely correspond to intervals of 1017–1528, 1628–1946, and 2653–2739 Ma. The obtained data imply that material of quartzite–schist sequences of the Kokchetav massif was provided by Mesoproterozoic, Paleoproterozoic, and Neoarchean rock complexes. The lower age limit determined for these sequences is approximately 1.06 Ga. The dates obtained for detrital zircons are most consistent with events that took place in Laurentia. They correspond to the formation and breakup of the Columbia/Nuna supercontinent (approximately 1650–1580 and 1450–1380 Ma ago, respectively) and formation of the Rodinia supercontinent in the period of 1300–900 Ma ago.

Titanium minerals in Cameroon

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.

Ion Microprobe U-Pb Age and Zr-in-Rutile Thermometry of Rutiles from the Daixian Rutile Deposit in the Hengshan Mountains, Shanxi Province, China

The Daixian rutile deposit is located in the Hengshan Mountains in the Trans-North China Orogen; it is con sidered to be one of the largest rutile deposits in China, with 6 million metric tons (Mt) of contained titanium. Most of the rutile ores are hosted in garnet-free anthophyllite gneiss with minor Mg hornblende, feldspar, quartz, phlogopite, rutile, zircon, and titanite. Rutile grains are euhedral, 0.02 to 0.50 mm in size, contain 98.649 to 99.784 wt % TiO 2, and form chains, thin layers along the foliation, and dense aggregates. Rutiles are compositionally homogeneous and contain no detectable mineral inclusions except local ilmenite lamellae and zircon. Crystallization temperatures of the rutile are estimated at ~640°C at 0.7 GPa, and ~647°C without pres sure calibration according to the Zr-in-rutile thermometer, recording amphibolite facies metamorphism of an intermediate P/T ratio series. Variations in Nb versus Cr in rutiles indicate a connection of the ores to mafic protolith; not a pelitic rock derived from aluminous sedimentary rocks. SIMS U-Pb analyses of rutiles from the deposit yield a mean 207 Pb/ 207 Pb age of 1780.2 ± 9.6 Ma. Considering the closure temperature (up to ~650°C), grain sizes and recrystallization of the rutile, this age is more likely to represent closure and/or recrystallization time rather than peak metamorphism period, so the rutile deposit formed not younger than ~1780 Ma. This unique garnet-free rutile deposit was metamorphosed from mafic rocks in amphibolite facies during the Paleoproterozoic or Archean, being distinct from any other metamorphic rutile deposits, such as the known eclogite-related types.

Constraining ultrahigh-pressure (UHP) metamorphism and titanium ore formation from an infrared microthermometric study of fluid inclusions in rutile from Donghai UHP eclogites, eastern China

Eclogites in the Donghai area of the Sulu ultrahigh-pressure (UHP) metamorphic belt in eastern China contain both disseminated rutile and rutile deposits. The rutile occurs as small inclusions in garnet, omphacite, phengite, and quartz, as larger euhedral to subhedral grains in equilibrium with garnet, omphacite, phengite, and kyanite, and as discrete veinlets, aggregates, and megacrysts in cracks and along grain boundaries. To investigate the processes of rutile mineralization and its relationship to the evolution of the Sulu UHP metamorphic belt, we sampled the exposed Maobei deposit at Donghai and drill core between 100 and 2000 m in the nearby Chinese Continental Scientific Drilling Project (CCSD) main hole to carry out a detailed infrared microthermometric fluid inclusion study. Three types of fluid inclusions were identified: aqueous (Type I), CO 2 -H 2 O (Type II), and CH 4 (Type III). Type I and Type II inclusions are the most common. Primary and pseudosecondary Type I inclusions, which were trapped during recrystallization of the eclogite or early amphibolite facies retrograde metamorphism, have a narrow range of homogenization temperatures but a wide range of salinities. In contrast, secondary Type I inclusions, which formed entirely during retrograde amphibolite-facies metamorphism associated with exhumation of the UHP rocks, have higher and more varied homogenization temperatures but medium to low salinities. Type II inclusions formed contemporaneously with the Type I variety and are characterized by having small amounts of CO 2 and N 2 in addition to H 2 O. In addition, some of the rutile grains contain sparse inclusions composed of CH 4 (Type III). Our results combined with those of previous studies, suggest a great diversity of fluid composition in the peak metamorphic to early retrograde stages, implying very limited fluid-rock interaction during syn- to post-peak high-pressure (HP) and UHP metamorphism. This study shows that infrared microthermometric investigation of fluid inclusions can provide information not only on the composition of titanium ore-forming fluids but also on the relationship between mineralization and the evolution of UHP metamorphic belt.

UNCONVENTIONAL RUTILE DEPOSITS IN THE QUEBEC APPALACHIANS: PRODUCT OF HYPOGENE ENRICHMENT DURING LOW-GRADE METAMORPHISM

Unconventional rutile deposits occur in heavy mineral paleoplacers of the Pinnacle Formation in the Humber zone of the Quebec Appalachians. Detrital hemo-ilmenite represents 65 percent of the heavy mineral assemblage and is the main titanium mineral. Detrital rutile is also present in trace amounts. Postdepositional and metamorphic alteration processes increased the titanium content of the hemo-ilmenite grains by leaching elements, particularly Fe. New minerals created by these processes include pseudorutile, anatase (a TiO 2 polymorph), and neorutile. Early metamorphic magnetite enclosed detrital grains and preserved evidence of premetamorphic weathering or diagenetic processes by isolating the grains from metamorphic fluids, thus preventing further leaching. Detrital grains that were not protected by this magnetite were metamorphically leached to the purer TiO 2 mineral phase of anatase. Grains of anatase locally recrystallized to neorutile during a late orogenic back-thrusting event in the Silurian. This is supported by δ 18 O water in equilibrium with metamorphic magnetite and by the fact that neorutile is limited to the eastern part of a synformal keel near the back-thrust fault and is rarely observed farther west, where anatase is predominant. Rutile formed under greenschist metamorphic conditions from primary hemo-ilmenite detrital grains via intermediate pseudorutile and anatase phases. This is the first known report of titanium mineral enrichment occurring under low-pressure and low-temperature metamorphic conditions. Our results could have significant implications for titanium exploration because they demonstrate that paleoplacer source regions are not restricted to eclogite and granulite facies terrains.

The Xiaojiao high-grade eclogite-type rutile deposit in Jiangsu, China: Geology, geochemistry and metallogenesis

The Xiaojiao rutile deposit with stratiform, banded and lens-shaped rutile-bearing eclogite in the Sulu ultra-high pressure metamorphic zone represents the largest and richest primary rutile mineralization in the zone. Four kinds of rutile can be recognized. They are: (1) inclusions in garnet and omphacite; (2) intergranular infilling between garnet and omphacite; (3) altered remnant; and (4) hydrothermal infilling in veinlets. Electron microprobe data show that sodic metasomatism probably from metamorphic fluid could play an important role in rutile mineralization during high and ultra-high pressure meta-morphism. The present paper concludes that according to geochemical characteristics, the eclogite originated from mafic and ultramafic rocks in the upper mantle and crust-mantle boundary and the Xiaojiao eclogite-type rutile deposit is genetically closely related to ultra-high pressure metamorphism.

Metallogeny of the Grenville Province revisited

Four new petrogenetic and metallogenic models are proposed herein to explain the formation of important mineral deposits in the Grenville Province, providing a framework from which to reappraise Grenvillian mineral potential. Recognition of a high-pressure metamorphic belt within the Grenville Province suggests a potential for eclogite-hosted rutile deposits, an important and much-sought commodity. A recently developed Norwegian model proposes that anorthosite genesis occurred through lower crust underplating and coeval partial melting, rather than by plume magmatism. Applied to the Grenville Province, the new petrogenetic model may provide insight into the widespread occurrence of platinum group element (PGE) poor nickel showings and the distribution of chromite, Ti-rich, and low-Ti iron-oxide deposits within the Grenville and adjacent terranes. A new type of sedimentary–exhalative (SEDEX) mineralization formed by oxidized brines has been defined following the discovery of new deposits in Australia. Applied to the Grenville Province, it provides a possible explanation for two long-recognized features of marble-hosted zinc deposits: (i) the presence of meta-siderite beds occurring as distal haloes around SEDEX zinc deposits, and (ii) the mutually exclusive division of these SEDEX deposits into massive sulphide and nonsulphide groups. The discovery of the giant Olympic Dam iron-oxide copper–gold (IOCG) deposit in Australia renewed the interest in magmatic low-Ti iron-oxide deposits in the Grenville Province that have been known and mined since early colonial times. Subsequent exploration in the northeastern part of the Grenville Province revealed the presence of breccia-hosted Cu–Au–U – rare-earth element (REE)-bearing iron-oxide mineralization. This deposit and other low-Ti iron-oxide deposits in the southwestern Grenville Province have a previously undocumented close spatial and temporal association with Ti-rich iron-oxide deposits. These examples demonstrate how new petrogenetic, tectonic, and ore deposit models developed in unmetamorphosed rocks can be successfully adapted to high-grade terranes, where they stimulate mineral exploration in these challenging conditions. Furthermore, by tracking the formation of ore deposits in the lower crust, the existence of unsuspected metallogenic associations in the higher crust, such as the low-Ti and high-Ti iron-oxide association observed in the Grenville Province, may be revealed.

Elemental composition of rutile from south-western Nigeria using X-ray techniques

Combined techniques of X-ray diffraction (XRD) and energy dispersive X-ray fluorescence (ED-XRF) have been used respectively to identify and analyse rutile obtained from a recently discovered deposit in the Osun-state in the south-western region of Nigeria. While the XRD provides structural information about the natural ore, the ED-XRF gives detailed information about the major, minor and trace elements/impurities contained in the sample. Quantitative analyses of the ore using pellets made from properly homogenised samples showed that the concentration of titanium dioxide (TiO 2), which is the dominant phase in the mineral could be as high as 82.45 wt%, giving Ti concentration of 49.4 wt%. The level of TiO 2 in the ore compared favourably with those found in some countries with notable rutile qualities. Other major elements observed in the ore include Fe (3.1 wt%), V (1.01 wt%), Ca (0.19 wt%) and K (0.21 wt%). In addition, several other elements/impurities were detected in minor and trace quantities including; Cr, Mn, Co (with concentration between 300 and 1000 ppm) and Zr, Ni, Zn, Rb, W, Pb, Sr, Y, Mo, Nb, Br, As, Cu (with concentration between 10 and 300 ppm). It is suggested that when properly mapped and extracted, the rutile deposit could become a reliable source of good grade TiO 2 for various industrial applications.

Eclogites of the Dabie Region: Retrograde Metamorphism and Fluid Evolution

Abstract Based upon fluid effects, retrograde metamorphism of eclogites in the Dabie region can be divided into the fluid‐poor, fluid‐bearing and fluid‐rich stages. The fluid‐poor stage is marked by polymorphic inversion, recrystallization and exsolution of solid solutions, and is thought to represent eclogite‐facies retrograde environments. The fluid‐bearing stage is likely to have occurred at the late stage of ecologite‐facies diaphthorosis and is represented by kyanite porphyroblasts, rutile, and sodic pyroxene in association with high‐pressure hydrous minerals such as phengite and zoisite (clinozoisite) without significant amount of hydrous minerals such as amphibole, epidote and biotite. The fluid‐rich stage might have commenced concomitantly with lower amphibolite‐facies diaphthoresis and persisted all the way towards the near‐surface environment. The product of this stage is characterized by plentiful hydrous and volatile‐bearing phases.The dissemination‐type rutile mineralizations in eclogites might have formed by preferential shearing‐induced pressure solution of gangue minerals at the fluid‐bearing stage. The accompanying vein rutile was precipitated from fluids of this stage after local transport and concentration, and may hence represent proximal mobilization of titanium from the eclogite. Therefore, rutile veins can be used as an exploration indicator for dissemination‐type rutile deposits.

Concentration and characterization of titanium minerals and zircon from the western Black Sea Coast sands of Turkey

To date, no ilmenite, rutile and zircon deposits of commercial importance have been reported in Turkey. However, information from recent reconnaissance activities indicates the possibility of an economically viable heavy-mineral deposit in the vicinity of Ormanli, which is located northwest of Istanbul along Turkey’s Black Sea Coast. Consequently, beach and sand-dune samples were collected from that area for additional analysis. Laboratory methodologies that were designed to simulate standard industrial heavy-mineral plant practices were used to analyze and evaluate the samples. Based on these analyses and current market needs, none of the deposits in the Ormanli area qualify as a commercial heavy-mineral deposit.

Titanium, vanadium, and niobium mineralization and alkali metasomatism from the Magnet Cove Complex, Arkansas

The Christy Ti-V-Nb deposit is hosted by the Arkansas Novaculite, adjacent to the carbonatite-alkaline Magnet Cove Complex. Mineralized rock contains up to 8 wt percent Ti, 2.68 wt percent V, and 0.124 wt percent Nb. Minor amounts of Li and Mo are present, and there is evidence for the preferential concentration of the middle to heavy rare earth elements (REE) in altered clay-rich dikes. Mineralized rock consists of (1) thermally recrystallized novaculite that is partly replaced by actinolite, sodic amphibole, taeniolite (KLiMg 2 Si 4 O 10 F 2 ), pyrite,and siderite, (2) brookite-bearing amphibole- and taeniolite-rich rock that contains siderite and pyrite, (3) quartz-brookite aggregates, and (4) goethite-rich rocks that form the oxidized zone of the deposit. Unaltered rock is scarce at the Christy deposit. Comparison of mineralized lithologies from the Christy deposit with those from two other areas of mineralization associated with the Magnet Cove Complex, the Magnet Cove Titanium Corporation deposit (Rutile deposit) and the Hardy-Walsh prospect, provides mineralogical and chemical evidence for the source of the mineralizing fluids at the Christy deposit.Massive clay-rich (kaolinite + or - smectite) dikes are in contact with the mineralized zones of the Christy deposit. The presence of relict K feldspar and pyrite in the least altered dikes and certain characteristic trace elements (e.g., Ba, Rb) suggest that the Christy dikes are related to less pervasively altered rutile-mineralized, pyrite-bearing carbonate-feldspar dikes fromthe Rutile deposit. The feldspar-carbonate dikes from the Rutile deposit may be the products of intense alkali metasomatism of alkaline igneous silicate rocks that were emplaced prior to the intrusion of the Magnet Cove carbonatite.The Christy deposit formed through a series of complex processes. The initial phase of mineralization is directly related to the infiltration of novaculite by alkali-rich fluids that were probably derived from carbonatite magma. Introduction of the metasomatic fluids preceded emplacement of massive feldspar- and pyrite-bearing dikes that were subsequently altered to the clay-rich masses Titanium, V, Nb, and Li were introduced by the alkali-rich fluids at temperatures that were, as indicated by fluid inclusion data (Willis et al., 1991), as high as 600 degrees C. During the initial stage of mineralization, V was concentrated in aegirine and sodic amphibole, Li was concentrated in taeniolite, minor amounts of Ti were concentrated in aegirine, and pyrite formed. The replacement of novaculite by the aforementioned minerals yielded excess silica, which precipitated as quartz in veins and as clear overgrowths on recrystallized, inclusion-rich (partly replaced) quartz. Niobium- and V-bearing brookite precipitated with the quartz. Minerals formed during the first stage reacted with a second fluid at temperatures of 100 degrees to 300 degrees C, as indicated by fluid inclusion data (Willis et al., 1991), and V was then concentrated in smectite and goethite. The isotopic composition of siderite [delta 18 O SMOW = 23.8-25.0ppm, delta 13 C PDB = -7.1 to -8.9ppm suggests that the second fluid was a mixture of low-temperature metasomatic fluid and ground water. Vanadium was further concentrated in clay minerals (Breit et al., 1992), in goethite, and in vug minerals as low-temperature alteration proceeded. Brookite is not totally resistant to weathering and it is at least partly replaced by other oxides in the oxidized zone.

Rutile from ilmenite using coconut pith as a reductant

Rutile, the raw material needed for chloride route has to be prepared by removing iron from ilmenite, as rutile deposits are scarce in nature. In this study, the iron oxide present in ilmenite was reduced for different times and temperatures using coconut pith which is an agrowaste available in large quantities in Kerala. Pith has lowS, P and ash contents and has a moderate calorific value. The reduction process was studied using chemical analysis, SEM, X-ray and EPMA. Reduction of iron oxide in the ilmenite reaches a maximum at 3 to 4 h at 1040°C containing 84% of iron in the metallic state and the rest in the ferrous state. Treatment with 20% hydrochloric acid at 80°C for 1 h with stirring, leaches out most of the iron from the reduced ilmenite leaving behind only 2% iron. The SEM and X-ray data show the gradual reduction and structural changes taking place during reduction of ilmenite with coconut pith.

Titaniferous iron and rutile deposits in Sunnfjord, western Norway

"Titaniferous iron and rutile deposits in Sunnfjord, western Norway." Geologiska Föreningen i Stockholm Förhandlingar, 102(3), pp. 291–292

Genetic aspects of the monazite and columbium-bearing rutile deposits in northern Lemhi County, Idaho

Deposits of monazite and Nb-bearing rutile in a belt more than 10 mi. long in northern Lemhi County, Idaho, are distinguished by their notable concentrations of such elements as Th, Ti, Nb, Ba, Ca, Fe, P, S, and the rare earths, and by their abundance of carbonates, chiefly calcite. These deposits occur as structurally controlled replacements of crystalline limestones, amphibolites, and porphyroblastic gneisses which form part of the complex metamorphic border zone of the Idaho batholith. Most of the deposits, which are small and tabular, show a sporadic and irregular distribution of minerals, the most abundant of which are actinolite, allanite, apatite, monazite, calcite, barite, ilmenorutile (Nb-bearing rutile), ilmenite, and magnetite. Other minerals, some of them sparse, include biotite, phlogopite, garnet, epidote, glaucophane, ancylite, bastnaesite, sphene, rutile, chlorite, pyrite, pyrrhotite, chalcopyrite, and quartz. Silicates, except sphene, were deposited first and were followed successively by phosphates, carbonates, sulfates, oxides, and sulfides. Most of the Th entered the allanite instead of the somewhat later monazite. The deposits possess all the compositional characteristics of the carbonatites, but differ from the type carbonatites in their seeming lack of association with alkalic igneous rocks. Although the deposits were regarded by others as replacements of marble beds and as products of metamorphic differentiation, the unique association and concentration of elements so characteristic of the carbonatites, coupled with the paragenetic development, suggests that they, like the carbonatites, are of magmatic rather than of metamorphic origin.