Heavy Mineral Studies Research Articles

Minerais pesados de saprólitos de pegmatitos intrusivos no ortognaisse Resende Costa: caracterização e correlação com a Província Pegmatítica de São João del Rei, Minas Gerais, Brasil

O estudo de minerais pesados representa uma importante ferramenta para a correlação entre pegmatitos, pois corpos espacialmente próximos e com mineralogia semelhante são normalmente interpretados como cogenéticos e provenientes de uma mesma fonte. Os minerais pesados dos pegmatitos intrusivos no ortognaisse Resende Costa foram descritos por estereomicroscopia, espectroscopia Raman, difratometria de raios X e a partir de imagens de elétrons retroespalhados em microscópio eletrônico de varredura. Esses se encontram mineralizados em minerais de Sn (cassiterita) e Nb-Ta (grupo da columbita-euxenita), semelhantemente aos pegmatitos intrusivos no metagranitoide Ritápolis, enquanto os corpos intrusivos no ortognaisse Cassiterita só exibem minerais do grupo da microlita e não apresentam cassiterita. Um intercrescimento entre fases de Nb-Ta-Ti se mostra determinante para caracterizar os pegmatitos intrusivos no ortognaisse Resende Costa e diferenciá-los dos corpos relacionados tanto ao metagranitoide quanto ao ortognaisse. Sugere-se a presença de pelo menos três gerações de corpos pegmatíticos na Província Pegmatítica de São João del Rei, sendo eles correlatos aos protólitos do ortognaisse Cassiterita, do ortognaisse Resende Costa e do metagranitoide Ritápolis.

Seasonal variations of textural and heavy minerals of the Karamana river sediments and beach sediments of Trivandrum, Southern Kerala

Kerala, south western state of India is known for its abundant heavy mineral deposits along the coast. Beach placer deposits in Kerala is known for ilmenite, rutile, zircon, monazite, sillimanite and garnet. The grain size study of the sediments from Karamana river, flowing in the southern part of Kerala. Sediments from different parts of the river basin is studied, which enabled to understand the grain size variations with course of the river from the Peppara dam to Thiruvallam, very near to coast. Mineralogy of the river vary from one place to another depending different factors like host rocks in the province, climate conditions of the area, agents of transport and hydraulic condition during deposition, also can predict the actual source area associated with heavy mineral. Textural and heavy mineral studies of the placers of beach and Karamana river basins indicating the river is one of the important contributors of sediments to the western coast of the southern part of Kerala. Samples from various parts of the river indicate that the sediment is medium sand, moderately sorted, fine skewed and platykurtic. The characteristics of grain size distribution are related to the source rocks, process of weathering, and different sorting processes during transportation and deposition. The total heavy mineral percentage shows it is prominently enrichment in fine sand and very fine sands.

Sedimentologic, Heavy Mineral and Provenance Studies of the Cretaceous Sediments in the Auchi Area of the Anambra Basin

The Upper Cretaceous Deposits of the Anambra Basin has a part of its sedimentary rock deposited in the Auchi area of Edo State. Geologic field and Sedimentological studies carried out on twenty eight (28) selected samples from a section of a road–cut show that the sediments range from fine through medium to coarse grained. Morphoscopic studies reveal subangular to subrounded outline of sand particles. These coupled with the various colours observed in the sediment, ranging from whitish sand through yellowish brown, pink and reddish brown possibly indicate a non–marine environment and a fluviatile to deltaic environment of sedimentation is suggested. Heavy mineral assemblage made up mainly of opaque, andalusite, zircon, hornblend, sphene and epidote suggest derivation from the Precambrian Igneous and medium to high grade metamorphic rocks of the underlying Basement Complex of Nigeria. 
 Keywords: Sedimentology, Cretaceous, Morphoscopic, Heavy Mineral, Provenance

Granulometry, heavy mineral and geochemical studies of stream sediments around Bula, Dass District, Northeast Nigeria

Active stream sediments generally consist of broken-down fragments of pre-existing rocks by the action of river (stream) flow. This makes them target materials for routine geochemical surveys and provenance analysis. Fifteen (15) stream sediment samples were collected in some parts of Bula and its environs, northeastern Nigeria, in order to determine their textural characteristics, heavy mineral and elemental composition. The sediments were subjected to granulometric, heavy mineral and elemental analyses. The result of granulometric analysis show that the streamsediments are poorly to moderately well sorted, very platykurtic to leptokurtic, fine to medium grained and positively skewed. Zircon, rutile and tourmaline are the dominant heavy mineral species occurring in the sediments. The computed Zircon-Tourmaline-Rutile (ZTR) index values for the samples range from 59.18 - 83.53, indicating mineralogical maturity. The geochemical data of the stream sediment samples show that the mean contents of the trace elements [Ti (0.73 ± 0.74%), Fe (0.39±0.19%), Cr (816±639ppm), Ni (258±108ppm), Pb (48±12.37ppm) and Zn (502±126ppm)] were higher than their respective average crustal values except for Fe. Computed threshold values indicate possible mineralization containing Fe and Ti. The elements have variable spatial distribution. The study shows that the trace elements composition of the stream sediments is majorly lithogenic. Because mineralization in rocks and sediments are often characterized by considerable variation in their trace elements contents, the metal concentrations in these sediments are large enough for Ilmenite and Rutile mineralization to be suspected within the study area.

Gravimetric Separation of Heavy Minerals in Sediments and Rocks

The potential of heavy minerals studies in provenance analysis can be enhanced conspicuously by using a state-of-the-art protocol for sample preparation in the laboratory, which represents the first fundamental step of any geological research. The classical method of gravimetric separation is based on the properties of detrital minerals, principally their grain size and density, and its efficiency depends on the procedure followed and on the technical skills of the operator. Heavy-mineral studies in the past have been traditionally focused on the sand fraction, generally choosing a narrow grain-size window for analysis, an approach that is bound to introduce a serious bias by neglecting a large, and sometimes very large, part of the heavy-mineral spectrum present in the sample. In order to minimize bias, not only the largest possible size range in each sample should be considered, but also, the same quantitative analytical methods should be applied to the largest possible grain-size range occurring in the sediment system down to 5 μm or less, thus including suspended load in rivers, loess deposits, and shallow to deep-marine muds. Wherever the bulk sample cannot be used for practical reasons, we need to routinely analyze the medium silt to medium sand range (15–500 μm) for sand and the fine silt to sand range (5–63 or > 63 μm) for silt. This article is conceived as a practical handbook dedicated specifically to Master and PhD students at the beginning of their heavy-mineral apprenticeship, as to more expert operators from the industry and academy to help improving the quality of heavy-mineral separation for any possible field of application.

GIS Based Index Overlay Method in Targeting Heavy Mineral Deposits, Southern Kerala Coast, India

Owing to the strategic importance in defence and the other industrial applications, the heavy minerals have attracted the attention of the geoscientists since long time. But they have been using mostly the traditional techniques for a long time for targeting the heavy mineral deposits. Later, the scientists have started employing modern techniques like scintillometer based field surveys, remote sensing and the laboratory based sedimentological and heavy mineral studies. But since the traditional techniques are more cumbersome and would be very difficult to cover the vast length of the Indian coasts of over 7500 km, faster and effective techniques are necessary. So, the information value method was accomplished in the present study to demonstrate the targeting of heavy minerals in parts of Kerala extending from 76° 41' - 08° 53' in NNW and 77° 13' - 08° 17' in SSE (1,811sqkm). In this study five geosystem maps, viz; Lithology, Lineament Frequency, Lineament Density, Lineament Intersection density and Geomorphology were prepared using the raw and digitally processed LANDSAT ETM 7 and IRS LISS IV FCC data sets. These geosystem maps were firstly prepared as vector GIS layers and then converted into raster maps using ARC GIS software with the pixel size of 100sq.m and the total pixels of 1,64,358. On the basis of the contribution of the above five main geosystem variables towards the heavy mineral potentials, weightages were assigned (Wi) to each of them. Similarly, depending upon the heavy mineral possibilities of the sub variables of the above five main geosystem variables, scores were assigned (Si) to each sub variables of the 5 main geosystem variables. Then, the Wi values were multiplied with the corresponding Si values of each of the sub variables of the 5 main geosystem variables and those were considered as final weightages (HMP-Heavy Mineral potentials) and assigned the same to the corresponding pixels of each sub variables of the five main variables. Followingly, the each WiSi weighted values of the 1,64,358 pixels of the lithology main geosystem variable were added with corresponding pixels of the remaining 4 main geosystem variables using ADD function menu of ARC GIS and integrated raster GIS database was generated with all the 1,64,358pixels having the cumulative WiSi values (ΣWiSi). Then, on the dynamic range of the ΣWiSi values, these pixels were classified into Very High, High, Moderate, Low and Very Low zones of heavy mineral concentrations. This was validated with heavy mineral weight percentage data derived from the field samples collected from the study area during survey. This study was basically undertaken to replicate it for the rapid appraisals of the probable heavy mineral target areas along the Indian coasts. However this can be replicated anywhere.

Source area evolution and thermal record of an Early Cretaceous back-arc basin along the northwesternmost Colombian Andes

Identifying the provenance signature and geodynamic setting on which sedimentary basins at convergent margins grow is challenging since they result from coupled erosional and tectonic processes, which shape the evolution of source areas and the stress regime. The Early Cretaceous evolution of the northern Andes of Colombia is characterized by extensional tectonics and the subsequent formation of a marginal basin. The Abejorral Formation and coeval volcano-sedimentary rocks are exposed along the western flank and axis of the Central Cordillera. They comprise an Early Cretaceous transgressive sequence initially accumulated in fluvial deltaic environments, which switched towards a deep-marine setting, and are interpreted as the infilling record of a marginal back-arc basin. Available provenance data suggest that Permian-Triassic metamorphic and less abundant Jurassic magmatic rocks forming the basement of the Central Cordillera sourced the Abejorral Formation. New detailed volcanic and metamorphic lithics analyses, conventional and varietal study of heavy minerals, detrital rutile mineral chemistry, allowed us to document changes in the source areas defined by the progressive appearance of both higher-grade and more distal low-grade metamorphic sources, which switched from pelitic to dominantly mafic in composition. Crystallochemical indexes of clay minerals of fine-grained rocks of the Abejorral Formation suggest that samples located close to the Romeral Fault System show characteristics of low-medium P-T low-grade metamorphism, whereas rocks located farther to the northeast preserve primary diagenetic features, which suggest a high heat-flow accumulation setting. We interpret that the Abejorral Formation records the progressive unroofing of the Central Cordillera basement that was being rapidly exhumed, as well as the incorporation of distal subduction-related metamorphic complexes to the west in response either to the widening of extensional front or the reactivation of fault structures on the oceanward margin of the basin. Although the deformational record of the Abejorral Formation would have resulted from over-imposed episodes, our new geochronological constraints suggest that this sedimentary sequence must have been deformed before the Paleocene due to the presence of arc-related intrusive non-deformed magmatic rocks with a crystallization age of ca. 60 Ma.

Sedimentological Studies of Alluvium Deposits along Ngovayang-Bipindi of Lokoundje River, Southwestern Cameroon

In an area of about 305 km2, Seventeen stream sediment samples were taken from alluvium on the banks and floodplain of the Lokoundje River and its tributaries. Sand samples after being dried in an oven, are subjected to sedimentological analyses in laboratory. Amongst the analysis carried out; the particle size analysis helped to establish a precise textural description of the sediment and to understand the active mechanisms which occur during transport and particle deposition. The morphoscopy of quartz grains consists in determining the mode and duration of transport of the grains, thus allowing reconstructing the geological history of the latter. Heavy minerals are suitable to know the nature of the rock in which they come from and equal to specify their distributing province. The morphometry of pebble makes contributes for a better understanding to apprehension of the agents responsible for the transport of these materials. It appears that the alluvium of the Lokoundje and its Bipindi tributaries are very fine to coarse. They are well segregated, classified, and homometric. It is the result of the actions of a hydrodynamic turbulent which is sometimes abrupt. From a morphoscopic point of view, using a binocular microscope, grains mainly belong to three categories based on their surface appearance: Grain unworn, the sub-dull and dull shiny. From the morphometric point of view, there is evidence of flattening and dissymmetry of pebbles which are slightly worn to form sub-spherical shapes. With regard to the study of heavy minerals, it has identified two mineralogical processions, which include a metamorphic process with the presence of Sillimanite and Andalusite. In addition, there is the presence of minerals such as green’s Hornblende, Tourmaline, and reflecting magmatic distribution. However, there are specific minerals such as zircon, which can be economically viable where the contents sometimes exceed 10 kg/m3. In the same vein, it has been noted the presence of gems like Topaze and Monazite which are real precursor auriferous accumulation.

Integrated heavy mineral study of Jurassic to Paleogene sandstones in the Mandawa Basin, Tanzania: Sediment provenance and source-to-sink relations

This paper concerns the heavy mineral composition of Jurassic, Cretaceous and Paleogene sedimentary successions in the Mandawa Basin. The nature of the heavy mineral assemblages in 38 samples was investigated to assess changes in sediment provenance through time. Further, the geochemistry of detrital amphiboles and garnets and the detrital zircon populations were used to determine possible sediment source terranes. Based on the heavy mineral compositions the sandstones were grouped into four heavy mineral assemblages: garnet-dominated, amphibole-dominated, epidote-dominated and zircon-dominated. Garnet-dominated sandstones are abundant in most Middle Jurassic to Middle Eocene samples and represent the main sediment input into the Mandawa Basin. Amphibole-dominated sandstones occur in a few Lower Cretaceous samples deposited in close proximity to their sediment source in the Masasi Spur area. A change in provenance is observed in the epidote-dominated sandstones of Middle Eocene and Early Oligocene age. This change coincides with a climatic shift towards a wetter and cooler climate associated with an uplift phase in East Africa. The detrital zircon population in the investigated samples share the same age fractions and are indistinguishable within analytical error. Mineral chemistries and zircon ages imply that the sediments deposited in the Mandawa Basin were mainly derived from several high-grade sources within the Neoproterozoic Mozambique Belt to the west of the basin.

Provenance of Jurassic-Cretaceous siliciclastic rocks from the northern Siberian Craton: an integrated heavy mineral study

Provenance of Jurassic-Cretaceous siliciclastic rocks from the northern Siberian Craton: an integrated heavy mineral study

Sedimentology and Depositional Environment of part of Lokoja Formation Exposed at Felele Junction, Southern Bida Basin

The exposed Campanian sedimentary sequence at Felele junction around Lokoja has been mapped, logged and sampled. The total thickness of the section is approximately 21.48m. The sediments consist of conglomeratic sandstones, coarse sandstones and mudstones. Grain size analysis performed on nineteen sandstone samples revealed the average values of mean, sorting, skewness and kurtosis as 0.6, 1.03, 0.53 and 0.76 respectively. These results show that the sandstones are coarse grained, poorly sorted, strongly fine skewed and platykurtic. This characteristic is typical of fluvial depositional environment. The plots of skewness against sorting, sorting versus kurtosis and mean against sorting suggest a fluvial depositional environment. Petrographic analysis of selected sandstones reveals the presence of quartz, feldspars (plagioclase and microcline) and mica (biotite and muscovite). Quartz (especially monocrystalline) dominates followed by feldspar with minor muscovite and biotite. Heavy mineral study revealed the presence of non-opaque mineral suites suggesting that the sediments are derived from the basement complex of igneous and metamorphic rocks. The heavy minerals observed include staurolite, rutile, kyanite, zircon and sphene. The samples are dominated by stauronite which signifies low grade metamorphism in the area. Integration of sedimentological and petrographical characteristics in this study suggest that the sandstone samples are derived from mixed origin and deposited in fluviatile environment under high energy setting not too far from the source. Hence it is a proximal deposit.

Provenance of the Gondwana sediments, Palar Basin, Southern India

Palar Basin is considered as one of the pericratonic rift basins of East Coast of India. An integrated petrography, clay mineralogy, and heavy mineral studies of sandstone and shale from the Palar Basin South India, Tamil Nadu, have been carried out to decipher their provenance, palaeoclimate, and tectonic setting. The mineralogical make-up of the clastic rocks is largely composed of quartz followed by feldspar, rock fragments with minor amounts of chlorite, glauconite, zircon, garnet, and opaque. Palar sandstones are coarse to medium-grained and mineralogically immature (poorly sorted and few are moderately sorted). The detrital quartz grains consist of well rounded and rounded quartz, monocrystalline quartz with uniform or straight extinction, and polycrystalline grains with five crystals of straight to slightly curved intercrystalline boundaries. Few of the monocrystalline quartz contain inclusions of sillimanite, rutile, and zircon needles and low content of plagioclase and k-feldspar. These petrographic analyses of the sandstone suggest derivation from metamorphic, igneous, and reworked sediments of different grades which infer that the recycling and the clasts were subjected to both long and short transport distances. The recycled orogen provenance suggests that the sandstone has been derived predominantly from low-lying granite and gneissic sources. The framework petrography exhibits (a) higher percentage of quartz, (b) predominance of monocrystalline grains, (c) feldspar affinity, and (d) paucity of rock fragments, and low F/R ratio suggests that the sediments deposited were in a passive continental margin tectonic setting. The presence of euhedral, angular, and subrounded grains of zircon, rutile with reddish and dark boundaries, the high and moderate ZTR Index (zircon-tourmaline-rutile) and the ratio of RuZi (rutile/zircon) and GZi (garnet/zircon) low values reveal that the Palar Basin sediments were sourced from the combination of metamorphic and igneous (granite and gneisses) rock types. The presence of high amount of rock derived clay (illite, chlorite) is predominant than soil derived (kaolinite, smectite) clay minerals. The high content of illite indicates the source of the clay minerals from pre-existing rocks of granite and gneisses, subjected to physical weathering over chemical weathering in a temperate climate (hot/humid) with moderate hydrolysis.

Late Cenozoic palaeogeography of Sulawesi, Indonesia

Sulawesi has a remarkable biodiversity, an unusually rich endemic fauna, and is the largest island in Wallacea, just west of the Wallace Line. Alfred Russel Wallace himself suggested it could perhaps be the most remarkable island on the globe because of its peculiar fauna. It was home to extinct fossil fauna such as dwarf proboscideans, records significant Pleistocene faunal turnover, and evidence of early human occupation suggests an important role in hominid migration through the Sunda-Sahul region. Information on Neogene palaeogeography is essential for understanding biogeographic patterns, biodiversity and faunal changes. New palaeogeographic maps reflecting recent work on Sulawesi's complex geology and changes in tectonic interpretations are presented for intervals from the Early Miocene to Pleistocene, at 20, 15, 10, 8, 6, 5, 4, 3, 2, and 1Ma. Additional maps illustrate the effects of glacially-driven sea level change in the last 1Myr. They are based on a field-based investigation of sedimentary rocks in Sulawesi, accompanied by palaeontological, petrological and heavy mineral studies and U-Pb dating of detrital zircons, to date and determine depositional environments. The new results have been supplemented by re-evaluation of previous studies, including reports from oil company wells and seismic lines. Igneous rocks provided ages, indications of surface environment of eruptions, and location of magmatic activity. For most of the Neogene from the Early Miocene Sulawesi was a shallow marine area with a number of small islands, surrounded by relatively deep marine areas. Deep inter-arm bays began to form in the Late Miocene and the islands became larger. The most significant palaeogeographic change began in the Pliocene with an increase in the area and elevation of land accompanied by major subsidence of the inter-arm bays. The separate islands gradually coalesced in the Pleistocene to form the distinctive K-shaped island known today.

Evolution of the northern Albertine Rift reflected in the provenance of synrift sediments (Nkondo-Kaiso area, Uganda)

Rift sediments are important archives for the evolution of the East African Rift System. We present a source-to-sink study of the Nkondo-Kaiso area in the northern Albertine Rift from a ∼200 m thick late Miocene to early Pleistocene sediment succession. The multi-proxy provenance analysis includes framework petrography, heavy mineral studies and single grain studies of garnet and rutile. Mineral textures and provenance signatures indicate two major stages. Sediment of Stage 1 (late Miocene - late Pliocene; ∼6.5–2.6 Ma) is less mature with quartz contents of 58–81%, K-feldspar of 9–15%, plagioclase of 4–15%, and rock fragments of 1–9%. Heavy mineral spectra are dominated by epidote and amphibole with minor abundances of zircon, sillimanite and garnet. Garnet is almandine-rich and can be grouped according to grossular contents (<10% and >10%). Rutile exhibits a wide range of Nb and Cr concentrations, most of them typical for a metapelitic origin. Zr-in-rutile formation temperatures range between ∼570 and 940 °C. Garnet and rutile geochemistry mainly correspond to amphibolite-to granulite-facies igneous and metasedimentary rocks, which exist in the Mesoarchean Karuma Group and the Neoarchean granitoid gneiss of the North Uganda Terrane. Both are part of the adjacent eastern rift flank of the Albertine Rift. A slight change of the heavy mineral composition at ∼4.5 Ma can be correlated with the onset of the synrift stage ∼0.5–1.0 Ma later than in the southern Albertine Rift. Sediment of Stage 2 (early Pleistocene ∼2.6–1.0 Ma) shows a higher quartz content of 82–93%, and lower contents of K-feldspar of 5–11%, plagioclase of 1–7%, and rock fragments of 1–2%. Stable heavy minerals (ZTR index: 19–63) and epidote dominate with minor amphibole and garnet. Rutile and garnet chemical compositions remain largely unchanged to Stage 1 pointing to the same primary source. Obviously, Pleistocene sediment was mainly recycled from sedimentary rocks of the Neoproterozoic Bunyoro Group, which originate from identical Archean rock assemblages. Ongoing river incision reactivated the primary Archean source in the upper part of Stage 2. In conclusion, Miocene to Pleistocene sediment of the Nkondo-Kaiso region is supplied from local sources of the rift flank and the adjacent Ugandan plateau. Tectonic pulses at ∼4.5 Ma, ∼2.6 Ma, and ∼1.5 Ma led to river incision and moderate expansion of drainage basins towards the east. These pulses are roughly coincident with other parts of the EARS but also show regional time lag and delayed response of the source-to-sink system.

Heavy mineral studies of Gondwana sandstones of Eastern Arunachal Himalaya and implications for provenance

A thin linear belt of Permian Lower Gondwana rocks occur in the Eastern Himalayas from Arunachal Pradesh to Sikkim. The Lower Gondwana Group of rocks consists of shale, siltstone, sandstone, carbonaceous shale and coaly matter and is sandwiched between Miri Group and Siwalik Group of rocks. Heavy mineral composition of sandstones is extensively used in the provenance studies as they are the surviving remnants of the rather abundant but unstable mafic components of the source rock. The sandstones of Lower Gondwana Group bear the heavy mineral assemblage of chlorite, biotite, zircon, ilmenite, epidote, garnet, amphibole, chloritoid, brown tourmaline, magnetite, staurolite, rutile, and opaques which is indicative of a provenance of metamorphic rocks with input of igneous rocks. Provenance sensitive mineral index ratios were also calculated to see the variation in the ratio of two or more stable minerals with the same characteristics.

Provenance of the Lunz Formation (Carnian) in the Western Carpathians, Slovakia: Heavy mineral study and in situ LA–ICP–MS U–Pb detrital zircon dating

The Middle Carnian (Julian) detritic sediments of the Lunz Formation were deposited during of the so-called Carnian Pluvial Event. They are the only siliciclastic sediments embedded in purely carbonatic formations. The paper brings the first provenance analysis of this formation from the Western Carpathians (Slovakia), where it occurs in the Hronic, Fatric and Veporic zones. Sandstones of the Lunz Formation belong to feldspatic greywackes and less to lithic greywackes. Modal analyses indicate that the sand material was derived from dissected arc and less from a recycled orogen. The heavy mineral assemblage is dominated by zircon and by apatite, slightly lesser amount of garnet, Cr-spinels and tourmaline. Analysis of tourmalines (schorl and dravite) shows their primary provenance mainly from the metapelites and metapsammites coexisting, or not coexisting with an Al-saturating phase; some were also derived from Fe3+-rich quartz–tourmaline rocks, calc-silicate rocks and metapelites, and a slightly smaller group of grains was derived from Li-poor granitoid rocks and their associated pegmatites and aplites. Most of the garnet grains belong to almandine, less to spessartine. All of them have a wide spectrum of potential primary source rocks from low- to medium-grade metamorphic rocks and magmatites. The analysed spinel grains (Cr-rich spinel, chromite and magnesiochromite) match mostly the podiform chromitites, harzburgite and cumulate fields or supra-subduction zone peridotites field, whereas Al-depleted spinel best match the arc volcanic field. Some spinels were affected by alteration or metamorphism. The in-situ LA–ICP–MS isotopic U–Pb dating shows a wide age interval of detrital zircon crystals in the Lunz Formation. Concordant zircon data show a wide interval of Late Triassic (Carnian) to Early Proterozoic ages (~230–2500Ma). Majority of zircons shows Paleozoic (pre-Variscan and Variscan) ages, whereas Neoproterozoic to Paleoproterozoic age populations are relatively scarce. Age populations and chemical composition of zircon reveal their dominant primary provenance from various suites of magmatic rocks, including Variscan granitic rocks and pre-Variscan metaigneous lithologies. Characteristic is big scatter in zircon ages and the dominance of ultrastable minerals, as zircon, tourmaline, rutile and Cr-spinels, and quite a good correlation between zircons and Cr-spinels. This indicates that most of the heavy minerals were not directly derived from some distinct primary magmatic or metamorphic sources, but as recycled particles from older sediments, or metasediments. In the context with the previously published palaeogeographic reconstructions, the provenance analysis indicates that the source area was most likely situated outside the Alpine-Carpathian shelf. They are most likely related to the coeval, mostly fluvial Stuttgart Formation in the Central European Basin (Germanic Triassic Basin).

Heavy mineral studies on late quaternary red sediments of Bhimunipatnam, Andhra Pradesh, East coast of India

Thirty one sediment samples from different varieties viz. yellow, reddish brown, brick red and light yellow sands from red sediments of Bhimunipatnam, Andhra Pradesh were studied to understand the heavy mineral assemblage, their fractionwise distribution and concentration. The heavy mineral assemblage in red sediments is ilmenite, magnetite, sillimanite, garnet, zircon, rutile, kyanite, monazite etc. Total heavy minerals (THM) wt. % varies from 16.67 to 23.99% and their concentration is not uniform in all the sedimentary samples. The higher THM wt% in brick red sands (23.99%) followed by reddish brown sands (20.24%), light yellow sands (17.10%) and yellow sands (16.67%). The finer fractions have more concentration of THM wt% than coarse fraction. The vertical distribution of heavy minerals in each sedimentary unit indicates that these units are not formed in single phase of deposition. Less concentration of garnets in yellow and light yellow sedimentary units indicates that the garnets might be chemically altered into iron hydroxide–limonite which gives yellow colour to the sediments under slightly oxidizing environment. Low concentration of garnets in brick red and reddish brown sediments indicates that garnets might have been undergone chemical decomposition under acidic conditions leads to produce iron oxides (Hematite) causes for red colorization of these units. The heavy mineral assemblage in different sand units indicates that they are derived from Eastern Ghat Group of rocks (khondalites and charnockites).

Origin of placer gold and other heavy minerals from fluvial Cenozoic sediments in close proximity to Rote Fäule-related Au mineralisation in the North Sudetic Trough, SW Poland

Detailed morphological and geochemical studies of placer gold grains and other heavy minerals from Cenozoic fluvial clastic sediments in the area of the Zimnik Creek drainage basin (North Sudetic Trough, Lower Silesia) allowed the description of their specific features: shape and morphology, flatness index, internal textural features and chemical composition of the gold grains. It enables an estimation of the distance from the source area and determination of the source of the ore mineralisation, along with establishing the feeder areas for placer mineralisation including Rote Faule-related gold hosted by Rotliegend-Zechstein transitional sediments. The comparison of the heavy mineral contents of placer grains from the Zimnik Creek drainage basin makes it possible to identify the area of origin for the gold particles. The crystalline Au-Ag-Pd-Hg (polymetallic) alloy grains of fluvial gold are assumed to come from the transitional sediments between the Rotliegend and the Zechstein in the North Sudetic Basin. The morphological and geochemical features of the polymetallic grains strongly suggest that the grains from the upper course of the Zimnik Creek valley sediments represent what has eroded from the local gold mineralisation and this mineralisation is probably in the vicinity of the upstream sampling site. The bimodal chemical composition of the Au-Ag-Pd-Hg alloy grains with electrum and medium-Ag grains (<15 wt.% Ag) found in the study area is typical of the Rote Faule and Kupferschiefer-related gold mineralisation on the southern side of the North Sudetic Trough and the Sieroszowice-Polkowice copper mining district of the Fore-Sudetic Monocline. The study of the Ag contents of placer grains from the Zimnik Creek drainage basin highlights the contrast between the placer gold grains derived from Paleozoic orogenic gold mineralisation in the Sudetes (typically simple Au-Ag alloys containing between 5 and 20 wt.% of Ag) and the one formed by the oxidizing chloride hydrothermal systems. The grains identified in this manner as originating from the oxidizing hydrothermal system of the transitional zone can be distinguished from the placer gold derived from other styles of mineralisation, which are not Rote Faule-related. It is particularly important considering the ongoing reconnaissance exploration in the North Sudetic Trough (SW Poland), which employs gold grain analyses as a prospecting tool for the detection of potentially economic primary gold mineralisation.

Preliminary Study of Heavy Minerals in the Central Yellow Sea Mud

We studied the heavy minerals in 46 surface sediments collected from the Central Yellow Sea Mud (CYSM) to characterize the type, abundance, mineralogical properties and distribution pattern using the stereo-microscopy, field-Emission scanning electron microscopy (FE SEM) and chemical analysis through the energy dispersive spectrometer (EDS). Heavy mineral assemblages are primarily composed of epidote group, amphibole group, garnet group, zircon, rutile and sphene in descending order. Epidote group and amphibole group minerals account for more than 50% of total heavy minerals. The minerals in epidote group, amphibole group and garnet group in studied area are epidote, edenite and almandine, respectively. When we divided the CYSM into two regions by , the eastern region contain higher contents of epidote and (zircon + rutile), which are more resistant to weathering but lower of amphibole, which is less resistant to weathering than the western region. Based on this results, it is possible to estimate that the eastern region sediments are transported for a long distance while western region sediments are transported for a short distance from the source area. In the future, the additional study on the heavy minerals in river sediments flowing into the Yellow Sea and much more samples for marine sediments must be carried out to interpret exactly the provenance and sedimentation process.

Provenance of sandstone on the western flank of Anambra Basin, Southwestern Nigeria

Petrographic and heavy mineral studies were carried out on clastic deposits that crop out in Ikpeshi, Auchi and Fugar localities in order to determine the provenance of the sediments and the tectonic setting of the source area. The localities are in the western flank of the Anambra basin, southwestern Nigeria. Petrographic study shows that the sandstone deposits are composed of variable amounts of quartz, feldspars and lithic fragments with minor occurrence of authigenic silica and chlorite cements. Quartz is the predominant detrital mineral in all the samples accounting for over 87 % of the total framework composition. The representative samples from all the localities contain 88-94 % quartz, 1-8 % lithic fragment, 1-4 % cement and 0-4 % matrix. Feldspar is present in small amount only in samples from Fugar locality. The sandstones each classify as quartz arenites and sublitharenites. Both opaque and transparent heavy minerals occur in the sandstones. The opaques are magnetite, ilmenite and leucoxene. Together, they account for 35 – 55 % of the total heavy mineral abundance. The transparent heavy minerals are zircon, tourmaline, rutile, staurolite, and apatite listed in order of decreasing abundance. The heavy mineral assemblages in the localities are similar except for the absence of rutile from the sediments of Ikpeshi locality. The heavy mineral grains are subangular to rounded. The zircon-tourmaline-rutile (ZTR) index for the sediments from the three localities are generally high and range from 90.5 to 100% indicating high degree of mineralogical maturity of the sandstones. The heavy mineral suites and the petrographic signatures of the sandstones suggest derivation mainly from acid igneous rocks, gneisses and older sandstones in both stable tectonic and recycled orogenic settings. However, the absence of rutile in sandstone from Ikpeshi may suggest derivation from lithologically more restricted provenance.