Heavy Mineral Grains Research Articles

A powerful tool for assessing distribution and fate of potentially toxic metals (PTMs) in soils: integration of laser ablation spectrometry (LA-ICP-MS) on thin sections with soil micromorphology and geochemistry.

The dynamic behavior and inherent spatial heterogeneity, at different hierarchic levels, of the soil system often make the spatial distribution of potentially toxic metals (PTMs) quite complex and difficult to assess correctly. This work demonstrates that the application of laser ablation spectrometry (LA-ICP-MS) to soil thin sections constitutes an ancillary powerful tool to well-established analytical methods for tracing the behavior and fate of potential soil contaminants at the microsite level. It allowed to discriminate the contribution of PTMs in distinct soil sub-components, such as parent rock fragments, neoformed, clay-enriched or humified matrix, and specific pedogenetic features of illuvial origin (unstained or iron-stained clay coatings) even at very low contents. PTMs were analyzed in three soil profiles located in the Muravera area (Sardinia, Italy), where several, now abandoned mines were exploited. Recurrent trends of increase of many PTMs from rock to pedogenic matrix and to illuvial clay coatings, traced by LA-ICP-MS compositional data, revealed a pedogenetic control on metal fractionation and distribution, based on adsorption properties of clay minerals, iron oxyhydroxides or organic matter, and downprofile illuviation processes. The main PTMs patterns coupled with SEM-EDS analyses suggest that heavy metal-bearing mineral grains were sourced from the mine plants, in addition to the natural sedimentary input. The interplay between soil-forming processes and geomorphic dynamics significantly contributed to the PTMs spatial distribution detected in the different pedogenetic horizons and soil features.

Gamma-ray dose rate surveys help investigating century-scale beach ridge progradation in the wave-dominated Catumbela delta (Angola)

A strandplain at the downdrift side of the wave-dominated Catumbela delta (Angola) includes distinguishable deposits with very high natural radioactivity (up to 0.44 microSv/hour). In order to establish the geometry of these sedimentary units and understand their genetic processes, dose rate surveys were performed with the portable equipment Rados RDS-40WE. In addition, grain-size distribution, heavy-mineral composition and gamma-ray mass spectra of the high dose rate deposits were analysed. High dose rate values are found in ribbon units aligned parallel to the shoreline, which are a few tens of meters wide and up to approximately 3 km long. These units reflect the concentration of Th-bearing grains in coastal deposits enriched in heavy minerals. An integrated analysis of the high dose rate ribbons in GIS environment with aerial photography and topographic maps suggests that parts of the high dose rate units formed during the last two centuries may be related with the erosion of older shoreline deposits, due to updrift displacements of the Catumbela river outlet and recycling of shoreline accumulations with downdrift deposition. Simple gamma-ray surveys carried out with a portable detector can unravel depositional units characterised by significant enrichment in heavy-mineral grains that are likely to correspond to key events in the evolution of wave-dominated accumulations. The location of such deposits should be taken into account when planning future work using more expensive or time-consuming techniques.

Sedimentary Provenance and Depositional History of Cadiz Bay (SW Spain) Based on the Study of Heavy Minerals Surface Textures

Mineralogical and Scanning Electron Microscope (SEM) analysis was used to study heavy mineral grains present in recent marine sediments from Cadiz Bay (SW Spain) and the adjacent continental shelf, in order to establish the provenance of sediments and to determine physical and chemical processes which took place during their depositional history. Surface features analysis has been used to detect mechanical and chemical textures; euhedral, sub-euhedral and anhedral grain morphologies have been observed. Different phases or stages in the sedimentary evolution of these heavy mineral grains can be differentiated. The oldest one corresponds to eolian environments, followed by fluvial and coastal environments. The third phase is represented by chemical alterations acquired in shallow marine environments. The recent phase is characterized by presence of textures generated in pedogenic environments. Heavy mineral assemblages established in this work were compared with those found in the nearby continental areas; they are used to identify likely sediment sources. The most important source is the Iberian Massif, which provided euhedral and sub-euhedral metamorphic minerals, while the secondary sediment sources correspond to pre-orogenic formations of the Betic Cordilleras with predominance of anhedral grains of high degree of maturity. Other sediment sources are the post-orogenic Tertiary deposits present in the Guadalquivir basin and the plio-quaternary and fluvial deposits outcropping along coastal and continental areas near the bay of Cadiz.

A review of the Birimian Supergroup- and Tarkwaian Group-hosted gold deposits of Ghana

Ghana is the largest producer of gold in West Africa, a region with over 2,500 years of history with regards to gold production and trade. Modern exploration for and mining of gold in Ghana dates from 1874 with the establishment of the British Gold Coast Colony, which was followed in 1957 by the independence of Ghana and increased gold production since the early 1980s through Ghana's Economic Recovery Plan. At the time of writing, gold production (108.2 tonnes or 3.48 million ounces [Moz] in 2014) accounted for approximately one-third of Ghana's export revenues, with 36% of gold production coming from small-scale mining. The majority of the gold occurs in two styles of mineralisation, namely mesothermal quartz vein-hosted and associated gold in metavolcanics and metasediments and modified palaeoplacer gold in conglomerates. These styles of mineralisation occur in the Palaeoproterozoic Birimian Supergroup and Tarkwaian Group that make up Ghana's mainly southwest to northeast trending Birimian belts. Significant gold resources also occur as hydrothermal mineralisation in basement-type granitoids which show some geological association with the Birimian Supergroup-hosted mesothermal mineralisation. The majority of the gold mineralisation is believed to have formed between approximately 2.15 and 2.06 Ga during the Eburnean orogeny. The mesothermal quartz vein gold mineralisation is usually confined to tectonic corridors within the Birimian belts and is strongly associated with shear zones and fault systems. The quartz veins show multiple stages of formation and are steeply dipping, with the gold mineralisation occurring either as free gold within fractures in the veins or as invisible gold within disseminated sulphides in the host rocks surrounding the veins. The vein- and sulphide-hosted gold is strongly associated with deformational fabrics formed by the Eburnean extensional and compressional events, respectively, suggesting that disseminated sulphide mineralisation predates quartz vein-hosted mineralisation. The fluid from which the gold precipitated is believed to have been of metamorphic origin and carbon dioxide (CO 2 ) dominated, with lesser water (H 2 O) and nitrogen (N 2 ) and minor methane (CH 4 ). Gold precipitation was probably caused by decrease in pressure, temperature and CO 2 -H 2 O immiscibility, at depths of between 7 and 11 km. The palaeoplacer gold mineralisation shows some hydrothermal modification and occurs mostly within the conglomerates and to a lesser extent within the interbedded quartzite of the Banket Series of the Tarkwaian Group. The gold occurs as free gold in the matrix of the conglomerates and as intergrowths and overgrowths on and inclusions in, other heavy mineral grains. Based on strong evidence for palaeoplacer mineralisation, the gold was likely deposited with the conglomerates in alluvial fans and braided tributary channels. Because the Eburnean compressional event associated with the Birimian Supergroup-hosted mesothermal gold mineralisation also overprinted the gold-bearing Banket conglomerates, the former gold occurrences could not have acted as the source for the palaeoplacer gold. Hydrothermal gold mineralisation occurs in the Palaeoproterozoic belts and basin granitoids that intrude the Birimian belts, as well as in the sedimentary basins occurring between the belts. Gold mineralisation within the granitoids occurs as micro-inclusions in sulphides in small, steeply dipping stockworks and as sulphide disseminations concordant with regional faults and shears. A gold-bearing fluid similar to that for the Birimian Supergroup-hosted quartz vein gold mineralisation, but with a larger H2O component, is proposed to have formed the granitoid-hosted gold mineralisation.

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.

Hydraulic evolution of high-density turbidity currents from the Brushy Canyon Formation, Eddy County, New Mexico inferred by comparison to settling and sorting experiments

Hydraulic transformations in turbidity currents are commonly driven by or reflected in changes in suspended sediment concentrations, but changes preceding transformations can be difficult to diagnose because they do not produce qualitative changes in resultant deposits. This study integrates particle settling experiments and in situ detection of hydraulically contrasting particles in turbidites in order to infer changes in suspended sediment concentration during deposition of massive (Bouma Ta) sandstone divisions. Because grains of contrasting density are differentially sorted during hindered settling from dense suspensions, relative grading patterns can be used to estimate suspended sediment concentrations and interpret hydraulic evolution of the depositing turbidity currents.Differential settling of dense particles (aluminum ballotini) through suspensions of hydraulically coarser light particles (silica ballotini) with volumetric concentration, Cv, were studied in a thin vessel by using particle-image-velocimetry. At high Cv, aluminum particles were less retarded than co-sedimenting silica particles, and effectively settled as hydraulically coarser grains. This was because particles were entrained into clusters dominated by the settling behavior of the silica particles. Terminal settling velocities of both particles converged at Cv≥25%, and particle sorting was diminished.The results of settling experiments were applied to understand settling of analogous feldspar and zircon grains in natural turbidity flows. Distributions of light and heavy mineral grains in massive sandstones, Bouma Ta divisions, of turbidites from the Middle Permian Brushy Canyon Formation were observed in situ by X-ray fluorescence microscopy (μXRF). Hydraulic sorting of these grains resulted in characteristic patterns of zirconium abundance that decreased from base to top within Ta divisions. These profiles resulted from upward fining of zircon grains with respect to co-occurring feldspar grains. Although calculated settling velocity distributions for zircon grains in structureless sandstones were slower than those for feldspar grains at infinite dilution, calculated settling velocity distributions for zircon and feldspar grains in overlying black siltstone layers were identical. This evidence suggests that these sandstone divisions were deposited from hyperconcentrated suspensions where particle segregation was diminished and hydraulically fine grains were entrained with hydraulically coarse particles. Hydraulic fining of zircon grains during deposition implies that the suspended sediment concentration at the bases of turbidity currents increased even as the overall current evolved toward lower density as reflected by cessation of Ta deposition and by hydraulic equivalence of zircon and feldspar grains in overlying low-density turbiditic siltstones. This evolution likely resulted from volumetric collapse of the turbidity currents.

Heavy minerals in the late Eocene sandstone of Medicine Pole Hills, southwestern North Dakota

Late Eocene sandstone capping hills and small buttes in the Medicine Pole Hills in southwestern North Dakota has been correlated with the Chalky Buttes Member of the Chadron Formation. Heavy-mineral analysis was used to assess this correlation. Optical microscopy and chemical analysis using a scanning electron microscope/energy dispersive spectrometer (SEM/EDS) system were used to determine abundances and compositions of heavy minerals separated from 0.25–0.30 mm fractions of nine samples from seven depositional units (353–602 grains per sample). The 0.063–0.125 mm fraction was also studied for one of these samples. Samples ranged from coarse- to medium- to fine-grained poorly consolidated sandstone. Total heavy mineral recovery (0.4–14.1%) generally corresponded with the grain-size distribution of samples, with higher recoveries in coarser samples. Opaque grains (ferruginous aggregates, Fe-Ti oxides, and leucoxene) comprised 0.8–15.6 percent of heavy mineral grains. Non-opaque grains were dominated by amphibole (24.4–52.2%) and epidote-clinozoisite (10.6–38.1%), with variable diopside (0–51.1%). Generally less abundant minerals included garnet, apatite (bone fragments), biotite, and muscovite. One sample was biotite-rich (36.5%). Chemical compositions of heavy minerals showed no significant stratigraphic variations, suggesting the nature of the sources did not vary. Diopside, biotite, and approximately 1/3 of the amphibole grains were interpreted as derived from Tertiary volcanic sources. The majority of the amphibole grains (tremolite and blue-green hornblende), epidote, and garnet were derived from Precambrian metamorphic sources. The relative contribution of volcanic sources was variable (19–64%), being highest in those samples with more diopside and (with the exception of the biotite-rich sample) highest in those samples with higher overall heavy-mineral abundances. Individual heavy-mineral abundances also correlated fairly well with grain size. Overall, variations in heavy minerals were explained by variable volcanic source contributions and variations in grain-size distributions of the samples. Despite the variability found, cluster analysis showed that the samples from Medicine Pole Hills were consistently different than the generally much more stable heavy-mineral assemblages found in the Chalky Buttes Member. They were also consistently different when volcanic heavy minerals were ignored. The differences could not be explained by variable volcanic contributions, grain-size effects, and/or differences in heavy mineral stabilities alone. They require differences in provenance, suggesting that the sandstone of Medicine Pole Hills should not be correlated with the Chalky Buttes Member, or, at the very least, it should be considered a distinct facies of the Chalky Buttes Member.

Early Miocene Antarctic glacial history: new insights from heavy mineral analysis from ANDRILL AND-2A drill core sediments

The present study deals with heavy mineral analysis of late Early Miocene marine sediments recovered in the McMurdo Sound region (Ross Sea, Antarctica) during the ANDRILL—SMS Project in 2007. The main objective is to investigate how heavy mineral assemblages reflect different source rocks and hence different provenance areas. These data contribute to a better understanding of East Antarctica ice dynamics in the Ross Sea sector during the Early Miocene (17.6–20.2 Ma), a time of long-term global warming and sea level rise. The AND-2A drill core recovered several stratigraphic intervals that span from Early Miocene to Pleistocene and it collected a variety of terrigenous lithologies. The heavy mineral assemblages of the lower 650-m-thick sedimentary succession were analyzed through SEM observations and SEM–EDS microanalyses on heavy mineral grains. The heavy mineral analysis shows that the sediments are a mix of detritus dominated by McMurdo Volcanic Group sources most likely located in the present-day Mount Morning area (Proto-Mount Morning) with minor contribution from Transantarctic Mountains source rocks located west of the drill site. The heavy mineral assemblages in Interval 1 indicate that between 20.2 and 20.1 Ma, the grounding line of the ice sheet advanced to a position near the present-day Mount Morning volcanic center. During deposition of Interval 2 (20.1–19.3 Ma), the ice sheet most likely experienced a dynamic behavior with interval of ice advance alternating with periods of ice retreat, while Interval 3 (19.3–18.7 Ma) records further retreat to open water conditions. A dynamic behavior is noted in Interval 4 (18.7–17.6 Ma) with a decreasing contribution of materials derived from the basalts of the Mount Morning volcanic center located to the south of the drill site and a consequent increasing contribution of materials derived from the Transantarctic Mountains to the west of the drill site.

Tectonic constraints to Cretaceous magmatic arc deduced from detrital heavy minerals in northeastern Japan – evidence from detrital garnets, tourmalines and chromian spinels

Tectonic histories of sedimentary basins in the Cretaceous Japan arc have been assessed to understand the response of the Asian continental margin to the oblique subduction of the Paleo-Pacific (i.e. Kula or Izanagi) Plate beneath the Asian continent during the Early Cretaceous and that which subducted orthogonally in the Late Cretaceous. In the Lower Cretaceous Kuji Group (Santonian–Campanian) of the Kitakami Massif in northern Japan, sandstone petrography and chemistry of detrital heavy mineral grains were performed on sandstones to assess the tectonic environment on the basis of provenance analysis.Sandstone petrography results suggest that the material of the Kuji Group was derived mainly from areas of a Cretaceous volcanic belt (Rebun-Kabato Belt) and from a Jurassic accretionary complex (North Kitakami Terrane), which was intruded by Cretaceous granite, adjacent to the depositional basin. The chemical composition of detrital garnets suggests a North Kitakami Terrane origin, and detrital tourmalines are considered to have been derived mainly from meta-sedimentary rocks. The composition of detrital chromian spinels are compositionally diverse and mainly derived from tholeiitic and intra-plate basalts showing high TiO2 (>about 1.0 wt%) and island arc basalts with moderately low TiO2 (1.0 > TiO2 > 0.5 wt%) and high Cr#. Latter chromian spinels can be considered as a record of island arc activity including high Mg-andesite in Early Cretaceous time. Because adequate source rocks of the spinels are elusive near the basin compared with those of detrital garnets and tourmalines, these rocks are believed to have been disturbed by Cenozoic tectonics and eroded and covered by newly formed volcanic and sedimentary rocks.Comparison of chemical composition of the chromian spinels between Lower and Upper Cretaceous deposits in northern Japan indicates that chromian spinels with very low TiO2 (<0.5 wt%) prevail in the Lower Cretaceous (Aptian–Albian). In contrast, chromian spinels showing moderately low TiO2 predominated in the Upper Cretaceous (Santonian–Campanian). This clear difference suggests the change of oceanic plate motion around Japan arc promoted the change of source rock assemblage and the arc volcanic activity in mid-Cretaceous time. Thus the characteristics of detrital heavy mineral composition of the Kuji Group give the key to clarify the interaction between the swaying of young and hot plate and development of the Cretaceous island arc in eastern Asian margin.

Petrography of alluvial sands as a past and present environmental indicator: Case of the Loire River (France)

Four sample sets of the Upper and Middle Loire river sands were analyzed in order to study the impact of natural and anthropogenic factors on their petrographic composition in space (on an 800 km stretch) and time. Composition was determined by modal analysis of three sand-size fractions using a polarizing optical microscope and calculated for each sample (“standard sand” = Sst). The watershed is composed mainly of endogenic (Massif Central) and sedimentary (southern Parisian Basin) rocks. B-set sands collected in channels for different water flows in 1996 show that Sst compositions vary by only 5 %. Present-day sands in the Upper Loire and Middle Loire have very high petrographic immaturity comparing to others worldwide fluvial sands, although bio-climatic conditions favor sand maturation by source-rock weathering in the watershed. This shows the strong impact of the Massif Central on sediment yield due to relief rejuvenation as a consequence of the formation of the Alps during the Quaternary. Fluvial sands stored during the Weichselian and the Holocene in the Middle Loire floodplain, although partly weathered since their deposition, show higher inputs from the endogenic rocks of the Massif Central than present-day deposits. This can be explained by Weichselian periglacial conditions and the development of crop farming since the Neolithic, which favored mechanical erosion, particularly in the Massif Central which is characterized by a cold, humid climate and steep slopes. The upstream-downstream change in the composition of presently deposited sand is low in the diked area. It shows however that basalt and some heavy mineral grains are vulnerable to abrasion during transport and indicates a marked sediment yield from ancient sediment stored in the floodplain. This is in line with the high incision of the river bed over the last 150 years partly due to dam construction and aggregate mining.

Garnet and tourmaline as provenance indicators of terrigenous material in epicontinental carbonates (Middle Triassic, S Poland)

Heavy mineral grains contained in epicontinental carbonates are very rarely used for provenance analysis. This study deals with detrital heavy minerals separated from marly limestones and marlstones of the Gogolin Formation (GF; Middle Triassic), S Poland, to determine their source rocks and alimentary areas. The GF carbonates typically contain ≤1wt.% of heavy minerals within the very fine sand fraction. The heavy mineral assemblages consist predominantly of garnets (53.0–92.2%), and tourmalines (3.8–30.4%). EPMA analyses reveal four groups of garnets: low-Grs almandines with 30–50mol% Prp, almandines with 20–35mol% Prp and up to 35mol% Grs, almandines with up to 20mol% Sps, and rare pyrope grains (~60mol% Prp). The composition of the garnets indicates that HP felsic granulites were their main source rocks, but more mafic HP rocks (eclogites, retrograded eclogites, and mafic granulites), gneisses, mica schists, and garnet peridotites also contributed. The detrital tourmalines are represented mainly by dravite, and less frequently by schorl, which were derived mostly from paragneisses and mica schists, and in minor part from granitoids and pegmatites. The E–NE part of the Bohemian Massif is the most probable location of the source rocks. The presumed source rocks presently outcrop in the Moldanubian Zone, the Kutná Hora Unit, the Svratka Unit, and the Góry Sowie Massif. Nowadays, the bodies formed by the HP rocks within these units are insufficiently large to act as sources for delivering detrital material in the determined proportions. The high content of HP metamorphic grains thus indicates the past existence of extensively exposed and abundant high-pressure metamorphic rocks, eroded during and/or after the Middle Triassic.

HEAVY MINERAL DIAGNOSIS OF RAS BAGHDADY BLACK BEACH SAND: ACCUMULATIONS AND SIGNIFICANCE

A total of 30 samples each weighs 5 kg were collected from digging boreholes at 2 m depth at constant intervals across three profiles from Ras Baghdady beach sands, Red Sea coast, Egypt. Sieving, heavy mineral separation using Wilfy Shaked table and heavy liquid, magnetic separation using Lift type separator, mineral picking, mineral identifications, XRD, EDX and BSE have been performed to reveal the different mineral groups and the economic potentials. The separated grain size sub-samples arranged in their p order of abundance are 0.25-0.125 mm (10-60%), 0.5-0.25 mm (<10 to 20%), and 0.125-0.063 mm (<5 to 10%). Moreover, less than 1% to 10% are randomly distributed between grain size fractions < 0.063 and 1-0.5 mm. The most promising fraction based on the microscopic investigations containing mineral varieties and groups is very fine sand size. 60 gm of pure heavy minerals produced from 600 gm very fine sand size (0.125-0.063 mm). The light minerals are mainly detrital quartz grains and feldspars with mica flakes while the heavy minerals submitted to magnetic separation. Four separated magnetic sub-fractions (magnetite, ilmenite I, ilmenite II and ilmenite III) and one non-magnetic sub-fraction are obtained. The separated heavy minerals from Ras Baghdady very fine sand size (0.125-0.063 mm) contain 90 % of green silicates and 10 % of other heavy minerals in which ilmenite reaches 52 %, magnetite up to 15 %, garnet up to 11 %, goethite up to 11 %, zircon up to 5 %, rutile up to 3 %, sphene up to 3 % and other recorded traces of combined minerals up to 2 %. Based on the stereoscopic vision, XRD, BSE and SEM investigations, most of the studied heavy mineral grains are angular to sub-angular and homogenous in composition with a few variations to reflect short distance transportation and low energy deposition as depicted from the magnetically separated ilmenite grade III. The relative abundance and lateral distribution of the economic heavy mineral assemblages in the studied area are mainly controlled by hydraulic effects and beach topography. The estimated reserve of the economic heavy minerals within Ras Baghdady beach very fine sand can be summed up as follows; ilmenite 23490 tons, magnetite 6710 tons, garnet 5070 tons, goethite 5140 tons, zircon 2170 tons, rutile 1220 tons, sphene 1490 tons and leucoxene 10 tons. In addition to first record of ruby and sapphire, rare metal and radioactive bearing minerals such as monazite in which rare earth elements range is 61.2%, ~ 6.70 % Th, and ~ 5.4 % U as well as high content of Nd (17. 3%) and Sm (4.37%) are also recorded. Furthermore, the semi-quantitative EDX analyses of the picked uranothorite grains show high content of Th (40.12 %), U (11.77 %), and Y (11.9 %) while xenotime contains high content of Y2O3 (25.53 %), Yb2O3 (4.97 %), Nd2O3 (4.19 %) and Ce2O3 (3.46 %) as well.

A preliminary study on fingerprinting approach in marine sediment dynamics with the rare earth elements

Locating the quantitized natural sediment fingerprints is an important work for marine sediment dynamics study. The total of 146 sediment samples were collected from the Shelf of the East China Sea and five rivers, including Huanghe (Yellow), Changjiang (Yangtze), Qiantang, Ou and Min River. The sediment grain size and the contents of rare earth elements (REEs) were measured with laser particle size analyzer and ICP-MS technology. The results show that absolute REE content (Sigma REE) and the concentration ratio of light REEs to heavy REEs (L/HREE) are different in the sediments among those rivers. There are higher REE contents in being less than 2 m and 2-31 mu m fractions in the Changjiang Estuary surface sediments. The REE contents of bulk sediment are dominated by the corresponding values of those leading size-fractions. Sigma REE of sediment is higher close to the estuaries and declines seaward on the inner shelf of the East China Sea (ECS). The L/HREE ratio has a tendency of increase southward from 28 degrees N. Hydrodynamic conditions plays a predominate role on spacial distributions of the surficial sediment's REE parameters. In some situations, the currents tend to remove the coarser light grains from initial populations, as well as the deposit of the finer heavy mineral grains. In other situations, the currents will change the ratio of sediment constituents, such as ratio between silts and clays in the sediments. As a result, the various values of Sigma REE or L/HREE ratio in different bulk sediments are more affected by the change of size-fractions than source location. Under the long-term stable hydrodynamic environment, i.e., the East China Sea Shelf, new sediment transport model based on the size and density gradation concept may help to understand the spatial distribution patterns of REE parameters.

Heavy mineral-based provenance analysis of Mesozoic continental-marine sediments at the western edge of the Bohemian Massif, SE Germany: with special reference to Fe–Ti minerals and the crystal morphology of heavy minerals

During the Mesozoic, the epicontinental Germanic Basin and the Regensburg Strait the latter being an embayment of the Tethys Ocean that had subsided into the Moldanubian Zone of the Central European Variscides were filled with terrigenous continental-marine sediments. Both sediments’ heavy mineral (HM) grains and aggregates have been studied in a drill section in the Wackersdorf area, SE Germany. The majority of them belong to the (semi)opaque group of Fe–Ti minerals. In Wackersdorf, the entire stratigraphy of the basin fill, which occurred between the Triassic and the Late Cretaceous, is well exposed. In addition to the chemical composition of HM, the morphology and texture of zircon, apatite and Fe–Ti compounds have been studied in a provenance-related mineral classification. Provenance analysis has yielded five discrete source rock lithologies: (1) Moldanubian H-T-metamorphics, (2) late Paleozoic (sub)volcanic rocks, (3) gneisses of the Tepla-Barrandian unit, (4) ophiolites of the Tepla-Barrandian unit, (5) silicified shear zones and quartz cores of pegmatites. The detrital minerals include zircon, tourmaline (dravite-schoerl), apatite, monazite (Ce–Th–La–Nd), xenotime, biotite, rutile, ilmenite, “nigrine” (ilmenite-rutile intergrowth), sphene, amphibole, staurolite, garnet and spinel (Cr–Mg–Al). Based on the allogenic Ti and Fe minerals, a magnetite-type source area (Eh > 0, near-surface felsic to intermediate (sub)volcanic rocks) was distinguished from an ilmenite-type source area (Eh < 0), deeply eroded crystalline basement rocks (gneiss, granite, shear zones). The latter may be subdivided into “nigrine –I” (deep) and “nigrine-II” (intermediate) subtypes, according to the level of erosion in the source area. At the Jurassic–Cretaceous transition, extrabasinal erosion provoked a noticeable variation of allogenic heavy minerals with the incisions of rivers into source rock lithologies (4) and (5). Uplift and erosion along the western edge of the Bohemian Massif took place contemporaneously with spreading and closure in the central parts of the adjacent Tethys Ocean.

Radiometric ages of monazite from the Kwabonambi and Sibaya Formations (Maputaland Group) of northern KwaZulu-Natal, South Africa and the provenance implications

Radiometric analyses and ages for 96 monazite grains from the five subunits of the Kwabonambi and Sibaya Formations (Cenozoic Era; Maputaland Group) package of heavy-mineral rich sands on the KwaZulu-Natal coastal plain are presented. Although the ages range from 445 to 2366 Ma, and the different sub units and magnetic fractions show slight variations, there is a clearly defined pattern. The larger, and older, subgroup of grains (800–1299 Ma) encompasses, but shows a greater age range than, the rocks of the Natal Structural and Metamorphic Province; while the younger subgroup (400–699 Ma) can be correlated with the Saldanhian or Mozambican Orogeny. The presence of monazite grains with ages that are clearly not primarily related to stratigraphic units present within the modern (post Cretaceous) drainage basin, but reflect their initial provenance, indicates that the derivation history of the heavy minerals in the heavy mineral-rich Cenozoic sediments of the Kwazulu-Natal coastal plain is more complex than generally accepted. A polycyclic history is therefore envisaged with an intermediate sedimentary host (the Natal Group and/or Karoo Supergroup) for most, if not all of the heavy mineral grains in the Kwabonambi and Sibaya Formations.

Provenance from Chemical Composition of Heavy Mineral Grains of Neogene Sandstone in Otari-Sasagamine area of Northern Fossa Magna

Provenance from Chemical Composition of Heavy Mineral Grains of Neogene Sandstone in Otari-Sasagamine area of Northern Fossa Magna

The Provenance of the Varzaneh Aeolian Sand Field Regarding to Lithology and Texture, SW Esfahan, Iran

The main mineralogical/lithological composition of the Varzaneh aeolian sands is sedimentary and igneous lithics. The minor one is metamorphic lithics and mineral grains (such as quartz, feldspar and heavy mineral grains) respectively. The origin of the sedimentary lithics (mainly carbonates) mostly is from sedimentary rocks exposed in the west and the southwest of the study area. These rocks belong to Cretaceous and Jurassic outcrops. The origin of the igneous lithic grains chiefly belongs to Tertiary highlands, located to the north and the northeast of the study area. The main origin of the metamorphic lithic grains is from the mountain ranges located in the north-western and the western part of the drainage basin of the Zayandeh river. Texture of the aeolian sand grains is similar to the Zayandeh river sediments. Concentration of the aeolian sands at the west of the Zayandeh river delta, variation of their mineralogical/lithological composition from north to south, and textural characterizations of sand grains indicate that the water laid sediments of the Zayandeh river, widespread to the north of the aeolian sands, are the main supply of the aeolian sands and sediments deposited by the two ephemeral streams in the south and the southwest of the sand dunes are minor one.

Soil stratigraphy and plant–soil interactions on a Late Glacial–Holocene fluvial terrace sequence, Sierra Nevada National Park, northern Venezuelan Andes

Analysis of a flight of alluvial terraces in the Sierra Nevada National Park near Pico Mucuñuque in the Eastern Mérida Andes has yielded information on geomorphic, pedogenic, and vegetational changes from Late Glacial time to the present. The terraces formed in large part due to stream incision/migration triggered by neotectonic uplift (>7000 yr BP) of a Late Glacial/Early Holocene glaciolacustrine lithosequence and, with the exception of the oldest/highest terrace, exhibit near-uniform lithology/parent materials. Soils developed in the terrace materials range from thin, weakly developed profiles (O/C/Cu horizons) to Entisols with O/Ah/Cox/Cu horizons and similar buried counterparts representing former short periods of floodplain stability or slow aggradation. The buried soils provide organic-rich material that yields radiocarbon ages, which provide time constraints on individual pedons and the geomorphic development of the site. Iron and aluminum extracts of soil matrix material provide information on the formation and accumulation of goethite and hematite, the relative accumulation of ferrihydrite (gain/loss), and the downward translocation of organically complexed Al as a function of soil development and age. SEM analysis of heavy mineral grains indicates varying material sources and degrees of weathering in the soil chronosequence. A qualitative study of plant functional types across the terrace sequence shows that older surfaces support greater plant diversity. The study also suggests ways in which the plant communities influence soil development at the site through varying organic matter inputs and varying soil moisture use by specific species (e.g., ferns on the oldest terrace), which may explain the absence of B horizons in the Late Pleistocene/Early Holocene soils.

The Pliocene and Quaternary fluvial archives of the Rhine system

The River Rhine is one of the few major fluvial systems that connect the areas of the Alpine glaciers and Scandinavian ice sheet and so provides a key for correlating the two glacial areas in northern and middle Europe. The fluvial sequences of the Rhine Valley include at least 11 Pleistocene terraces in the Lower Rhine area, 2 Pliocene and 12 Pleistocene terraces in the Middle Rhine area resulting in 15 different Pliocene and Pleistocene terraces based on the correlation between Lower and Middle Rhine. The formation of fluvial terraces is significantly influenced by climatic and tectonic processes. The terrace staircases are a result of uplift in the Middle Rhine area and the southern part of the Lower Rhine area, whereas subsidence in the northern part of the Lower Rhine area resulted in buried stacked sequences. Magnetostratigraphic data provide chronological constraints for the terrace deposits in the Lower Rhine embayment and Middle Rhine region. The Matuyama/Brunhes boundary is a reliable marker horizon for the Upper Terrace fluvial deposits exposed in the Kärlich clay pit in the Middle Rhine area. The first appearance of volcanic heavy mineral grains in the terrace sediments, in loess and soils can be correlated from the Middle Rhine area through the Lower Rhine embayment to the Netherlands. The first occurrence of Nordic components in terrace sediments of the Lower Rhine area is known from gravel on top of the Kempen-Krefeld beds and so are younger than the Holsteinian but older than the penultimate glaciation. In the lower Middle Rhine area, 40Ar/ 39Ar dating of tephra layers intercalated in the aeolian and fluvial sediments provide age constraints. The Upper Pleistocene aeolian sediments overlying the terrace deposits have been dated by luminescence methods, and the tephra from the Laacher See eruption (12,860 BP) is present in the Younger Lower Terrace deposits.

Surface textures of heavy-mineral grains: a new contribution to provenance studies

The study zone is geologically very complex and corresponds to the western limits of the Betic Cordilleras (SW Spain); materials from the Triassic to Holocene are found here. This study demonstrates that most of the surface textures seen on quartz are present on the seven selected heavy minerals. SEM analysis of heavy-mineral grains reveals that certain morphologies are, in part, associated with particular surface textures. This textural analysis enables the source areas to be differentiated more clearly. Equally, it contributes to a deeper knowledge of the various stages of the grains provenance. A good example is the study of the heavy minerals of the Guadalete River terraces.