Heavy Mineral Species Research Articles

Heavy Minerals Distribution and Provenance in Modern Beach and Fluvial Sands of the Betic Cordillera, Southern Spain

This study uses heavy detrital minerals to determine actualistic fluvial and beach sand provenance across the Betic Cordillera (Spain), along the coast from Almeria to Marbella. The Betic Cordillera, primarily composed of metamorphic rocks to the east, supply an assemblage dominated by almandine and graphite, with a longshore dispersal from Almeria to Malaga. Buergerite and hypersthene indicate the provenance of calcalkaline lavas east of Cabo de Gata. The western part of the Betic Cordillera, which comprises the Ronda Peridotite Complex, supplies a chromite and diopside assemblage, with a dispersal from Marbella to Algeciras. Considering these mineralogical suites, the effects of source rock compositions and weathering are evaluated. The heavy mineral species mirror the mineralogy of the source rocks of local outcrops and wider source terranes. The fluvial heavy mineral suites do not differ significantly from those in the beaches except for some unstable species. Unstable species such as olivine, pyroxene, and amphibole do not show evidence of loss because of elevated topography and semiarid climate, which do not affect heavy minerals. This contribution also evaluates the potential of some heavy detrital species as ideal pathfinders in searching for diamonds.

Sedimentary Patterns and Spatial Distributions of Heavy Minerals along the Continental Shelf in the Espírito Santo State, Brazil

Heavy minerals can be used as tools to better understand sedimentary patterns across continental shelves, in addition to their economic importance, where they form marine placers. This study investigates the spatial distributions of heavy minerals in sand deposits along the three different morpho-sedimentary compartments (i.e., Paleovalley Shelf, Doce river Shelf, and Abrolhos Shelf) of the Espírito Santo Continental Shelf, which presents distinct sedimentary regimes. A mineralogical characterization of 180 surface sediment samples allowed to identify fifteen different heavy mineral species across the study area, with a predominance of ilmenite. The qualitative characterization shows similar heavy mineral patterns among the three compartments, while their mineral proportion (quantitative analysis) is heterogeneous. Also, the supply and accommodation regimes do not responsible by influence the heavy mineral assemblages and sediment maturity. However, there is a significant relationship between supply regime (delta sedimentation) and higher average abundances of each heavy mineral species. With results found here is possible to affirm that marine placers are closely related to Holocene sedimentation.

Heavy Mineral Assemblage Variation in Late Cenozoic Sediments from the Middle Yangtze River Basin: Insights into Basin Sediment Provenance and Evolution of the Three Gorges Valley

The Three Gorges valley is one of the two key capture points of the evolution of the Yangtze River, yet the formation of this valley—from the pre-Miocene to the late Pleistocene—remains uncertain. The Jianghan Basin, a late Mesozoic–Cenozoic basin located just downstream of the Three Gorges valley, is a crucial area for understanding the formation of the valley. In this study, we used heavy mineral assemblages to trace the provenance of Pliocene–Pleistocene sediments obtained from the 300-m-depth Zhoulao drillcore in the Jianghan Basin. Results show that heavy mineral concentrations, compositions, and species display a clear change at a depth of 110 m in the studied core, consistent with the change in values of magnetic indexes and trace-element geochemical indicators. The heavy mineral assemblage deposited below a depth of 110 m (lower section of the core) comprises zircon, epidote, leucoxene, rutile, anatase, pyrite, and titanite, whereas that deposited above 110 m (upper section) consists of hornblende, pyroxene, garnet, hematite-limonite, and magnetite. In addition, the heavy mineral assemblage of the upper section is similar to that of the modern surface fluvial sediments of the Yangtze, which indicates that materials of the upper core section of the Jianghan Basin were sourced from the upper Yangtze River Basin, west of the Three Gorges. After incision of the Three Gorges valley, sediments from the upper Yangtze were transported to the Jianghan Basin and deposited. Combining the results of this study with the known paleomagnetic chronology of the Jianghan Basin, we propose that the Three Gorges valley was incised at ca. 1.1 Ma.

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.

Multimineral Fingerprinting of Transhimalayan and Himalayan Sources of Indus-Derived Thal Desert Sand (Central Pakistan)

As a Quaternary repository of wind-reworked Indus River sand at the entry point in the Himalayan foreland basin, the Thal Desert in northern Pakistan stores mineralogical information useful to trace erosion patterns across the western Himalayan syntaxis and the adjacent orogenic segments that fed detritus into the Indus delta and huge deep-sea fan throughout the Neogene. Provenance analysis of Thal Desert sand was carried out by applying optical and semi-automated Raman spectroscopy on heavy-mineral suites of four eolian and 11 fluvial sand samples collected in selected tributaries draining one specific tectonic domain each in the upper Indus catchment. In each sample, the different types of amphibole, garnet, epidote and pyroxene grains—the four dominant heavy-mineral species in orogenic sediment worldwide—were characterized by SEM-EDS spectroscopy. The chemical composition of 4249 grains was thus determined. Heavy-mineral concentration, the relative proportion of heavy-mineral species, and their minerochemical fingerprints indicate that the Kohistan arc has played the principal role as a source, especially of pyroxene and epidote. Within the western Himalayan syntaxis undergoing rapid exhumation, the Southern Karakorum belt drained by the Hispar River and the Nanga Parbat massif were revealed as important sources of garnet, amphibole, and possibly epidote. Sediment supply from the Greater Himalaya, Lesser Himalaya, and Subhimalaya is dominant only for Punjab tributaries that join the Indus River downstream and do not contribute sand to the Thal Desert. The detailed compositional fingerprint of Thal Desert sand, if contrasted with that of lower course tributaries exclusively draining the Himalaya, provides a semi-actualistic key to be used, in conjunction with complementary provenance datasets and geological information, to reconstruct changes in paleodrainage and unravel the relationship between climatic and tectonic forces that controlled the erosional evolution of the western Himalayan-Karakorum orogen in space and time.

Heavy Mineral Variability in the Yellow River Sediments as Determined by the Multiple-Window Strategy

In this study, heavy mineral analysis was carried out in different size fractions of the Yellow River sediment to extract its end-members. It shows that heavy mineral contents, species, and compositions vary in different grain sizes. Distribution curve of heavy mineral concentration (HMC) and particle size frequency curve are in normal distribution. In most samples, the size fraction of 4.5–5.0 Φ contains the maximum HMC (18% on average). Heavy mineral assemblages of the Yellow River are featured by amphibole + epidote + limonite + garnet. Amphibole content is high in coarse fraction of >3.0 Φ and reaches its peak value in 3.5–4.5 Φ. Epidote is rich in a size fraction of >3.5 Φ, and increase as the particle size becomes fine. Micas content is high in coarse subsamples of <3.0 Φ, but almost absent in fine grains of >4.0 Φ. Metallic minerals (magnetite, ilmenite, hematite, and limonite) increase as the sediment particle size become fine, and reach the peak in silt (>4.0 Φ). Other minerals such as zircon, rutile, tourmaline, garnet, and apatite account for about 15%, and mainly concentrate in fine sediment. Further analysis reveals that similarity value between the most abundant grain size group and wide window grain size group is high (0.978 on average). The grain size of 4.0–5.0 Φ ± 0.5 Φ is suitable to carry out detrital mineral analysis in the Yellow River sediments. Our study helps to eliminate cognitive bias due to narrow grain size strategy, and to provide heavy mineral end-members of the Yellow River sediment for provenance discrimination in the marginal seas of East China.

Combined magnetic, electrostatic, and gravity separation techniques for recovering strategic heavy minerals from beach sands

ABSTRACTA combination of unit operations like gravity, magnetic, and electrostatic separation techniques were applied to separate strategic heavy minerals from bulk samples taken from two coastal stretches of Kappil-Varkala (KV) and Shanghumugham-Kovalam (SK) in Thiruvananthapuram, south Kerala, India. On processing the feed, the concentrate obtained contains 67.3% THM for KV and 65.15% THM for SK, out of which ilmenite predominantly exists with a yield of 45.55 and 43.6% in weight followed by other minerals like sillimanite, monazite, zircon, rutile, leucoxene, and garnet. Analysis indicates that judicious combination of unit operations like gravity, magnetic, and electrostatic separation techniques can efficiently recover heavy mineral species even from placers of smaller deposit.

Heavy mineral analysis by ICP-AES a tool to aid sediment provenancing

Correlation and provenancing of sediments/sedimentary rocks can be achieved by several techniques; a common approach is through the identification and quantification of heavy minerals using a petrological microscope. This can be time consuming, the analysis of heavy minerals by inductively coupled plasma atomic emission spectroscopy offers a faster alternative, by determining key elements associated with specific heavy minerals. Here we outline a method for determining heavy mineral species though ICP-AES using high temperature fusion with a lithium metaborate flux to ensure complete dissolution of resistate minerals. The method was tested in a provenance study of desert sands from the United Arab Emirates. The results are compared with those derived from traditional optical microscopy. These show good agreement for minerals with specific geochemical signatures, whilst the overall geochemistry of the heavy mineral concentrate was diagnostic of potential sediment sources. This geochemical approach is capable of processing large numbers of samples rapidly and is advocated as a screening technique. A combination of geochemical and mineralogical data produced by these techniques provides a powerful diagnostic tool for studies of heavy mineral signatures in sediments frequently used in mineral reconnaissance, paleogeographic reconstruction and reservoir characterisation in the petroleum industry.

Late Pleistocene aeolian dust provenances and wind direction changes reconstructed by heavy mineral analysis of the sediments of the Dehner dry maar (Eifel, Germany)

The study presents the results of a heavy mineral analysis from a 38m long record of lacustrine Eifel maar sediments from a core section of the Dehner dry maar. The record encompasses the period from 29,000 to about 12,500 b2k. Statistical analyses enabled the distinction of local and regional source areas of aeolian material and revealed pronounced changes in the amounts of different heavy mineral species and corresponding changes in the grain size Index (GSI and CSI). The results indicate that during the early stages of MIS2 (39 to 30m depth) aeolian sediments were supplied mostly from local sources. This period is characterized by low GSI and CSI ratios resulting from a reduced mobility of material due to a vegetation cover. The period between 23,000 and 12,900 b2k is characterized by a higher supply of heavy minerals from regional and more distant sources. Changes in the provenance areas are indicated in inverse relationships between zircon, rutile, tourmaline (ZRT) and carbonate particles. Shifts in the wind direction are documented in pronounced peaks of carbonate particles indicating easterly winds that have crossed the limestone basins in the Eifeler North South Zone. ZRT-group minerals on the other hand suggest a westerly source area from Palaeozoic clastic sedimentary rocks. The heavy mineral assemblage of the LGM section at 23,000 to 15,000 b2k displays a close correspondence with the stratigraphic relationships that have been obtained for the Landscape Evolution Zone 4 of the ELSA-Vegetation Stack of Sirocko et al. (2016). From the Heinrich 2 event onwards the analyses indicate an increasing degree of mixing of heavy minerals from various provinces. This suggests the existence of a presumably incomplete, thin cover of deflated loess-like sediments that has been repeatedly reworked on the elevated surfaces of the Eifel.

Sorting of heavy minerals in sediments deposited at a high accumulation rate, with examples from sandurs and an ice-marginal valley in NW Poland

Density differences among the various heavy-mineral species appear to be the main factor responsible for their sorting in glaciofluvial and fluvial environments. Sediments from two sandurs (stretching perpendicular to the Weichselian ice-sheet front) and a terrace of the Toruń-Eberswalde ice-marginal valley (extending parallel to the Weichselian ice-sheet front) in NW Poland support this idea clearly. The deposits investigated were formed during the Pomeranian phase of the Weichselian glaciation. Heavy-mineral and sedimentological analyses of these sediments indicate that most changes in the proportion of the various heavy-mineral species in gravelly and sandy sediments can be ascribed to changes in the flow regime, which is, in turn, related to the density of the various heavy-mineral species. In addition, the turbulence of the current and the bedform played a role in the sorting. The sedimentation rate also affected the heavy-mineral composition of the sandur and ice-marginal valley sediments. Furthermore, the proportions of some heavy minerals depend on the transport distance, which is well expressed by differences that occur over the investigated distance of 90 km of the ice-marginal valley. It appears that some heavy-mineral species are good tools for reconstructing sorting processes. Heavy minerals deposited by streams with a fast-changing discharge and a high accumulation rate (which is common for glaciofluvial streams) can, by combining data about the composition of the assemblages with data about the characteristics (size, rounding, colour, etc.), help in reconstructing palaeo-flow regimes and in estimating the turbulence, transport distance and mode of sediment transport in the streams.

Raman spectroscopy in heavy-mineral studies

Abstract Raman spectroscopy is an innovative tool with tremendous potential, serving as a fundamental complement to a variety of provenance methods including heavy-mineral analysis and detrital geochronology. Because of its accuracy, efficiency and versatility, the results of the Raman technique are indispensable for fully reliable identification of heavy minerals in grain mounts or thin sections. Thorny long-standing problems that cannot be solved confidently with a polarizing microscope alone, such as the determination of opaque and altered heavy minerals, of detrital grains as small as a few microns, or of colourless crystals with uncertain orientation and rounded morphology, can finally be addressed. Although the method can be highly automatized, the full ability and experience of the operator is required to combine Raman data with the optical information obtained under the microscope on the same grains, which is essential for the efficient application of the method in provenance studies. This article provides exemplary Raman spectra useful for the comparison and determination of over 70 different opaque and transparent heavy-mineral species commonly found in sediments, conveying specific information on the genesis of their source rocks, and thus is particularly useful in provenance diagnoses and palaeotectonic reconstructions. Supplementary material: Detailed information on the lasers used and the origin of the analysed minerals is available at http://www.geolsoc.org.uk/SUP18615 .

Unravelling the enigmas of the ‘silver sands’ in the Dutch/German/Belgian border area

AbstractBright white sands consisting almost exclusively of quartz (sometimes called ‘silver sands’) occur throughout the world; those in Europe commonly date from the late Paleogene and early Neogene. They have a clearly sedimentary origin, and they may have originated in various types of environments, but precise data are lacking because sedimentary research into these deposits (that have a high economic value) has been scarce. It is most likely that diagenetic processes are largely responsible for their exceptional appearance, but it is highly unlikely that all silver sands were subject to the same diagenetic conditions.The precise origin of most of the silver sands is still enigmatic. In the case of the silver sands in the Dutch/German/Belgian border area, it appears that long-lasting in situ leaching by humic acids (resulting in an extremely low percentage of heavy minerals), in combination with differential cementation (and later partial dissolution of the cement), must be held responsible for the wide variety of the characteristics of these sands, including locally sharp boundaries with the underlying sands, lack of precipitates at the contact plane with the underlying sands, and the joint occurrence of strongly weathered and fresh specimens of the same heavy-mineral species.

The Upper Miocene Injana (Upper Fars) Formation of Iraq: insights on provenance history

Petrographic, geochemical, and scanning electron microscope analyses of the sandstone and mudstone units of the Upper Miocene Injana Formation are presented. Furthermore, microprobe analysis for amphiboles, pyroxenes, garnet, and chromian spinels as common heavy mineral species present is done to support other results for better understanding of the provenance history of the Injana Formation. The sandstones of the Injana Formation consist of terrigenous carbonate lithic fragments as common type of sedimentary rock fragments in addition to chert, argillaceous, and rare sandstone fragments. They also include metamorphic and igneous lithic fragments, quartz, feldspars, and mica and generally, the sandstones are lithic arenites and immature. Scanning electron microscopic analysis for the heavy minerals shows that they have been affected by dissolution due to chemical etching and mechanical abrasion through several surface texture generated either in arid and semihumid environment or in diagenetic environment. Clay mineralogy of the mudstone units indicates the presence of illite, chlorite, kaolinite, palygorskite, and illite–smectite mixed layers. Bulk-rock and mineral phase geochemistry in addition to petrographic data suggest the derivation of the Injana Formation from a nearby sources with contribution from igneous, metamorphic, and sedimentary provenance mainly from the high lands in the northeastern parts of Iraq which comprise mainly the Zagros mountains and the older sedimentary formations.

Erosion and accretion rates and their associated sediment characters along Ras El Bar coast, northeast Nile Delta, Egypt

Beach profile data, covering the coast of Ras El Bar, northeast Nile Delta, collected during the years from 1990 to 2002 combined with landsat images for the area and sedimentological investigation have been used to identify beach and nearshore seafloor sediment changes. Along the coast of Ras El Bar, two accretion sectors and one of erosion have been recognized. The first accretion sector is located west of Damietta harbour, where the harbour jetties have halted the littoral transport, while the second one is behind a system of detached breakwaters protecting Ras El Bar resort. Both the two sectors are characterized by growing shoreline with maximum rates ∼15 and 10 m/year, respectively. Also, they have maximum nearshore seafloor accretion rates of ∼18 and 22 cm/year, respectively. The erosion sector is located east of Damietta port and has a maximum rate of shoreline retreat ∼−10 m/year. Erosion of its nearshore seafloor is indicated recording a maximum rate of ∼−20 cm/year. The rate of net sediment volume change in the area indicates shifting of the accretion sector (II) westward, responding to installation of the new breakwaters unit. The two accretion sectors are characterized by dominance of moderately sorted fine sands in their shore area which change seaward into less sorting very fine sands. Beach sands of the eroded sector are poorly sorted medium grain size. The dominant constituents of heavy mineral species in beach and sea-bottom sands are the characteristic assemblages of the Nile deposits. The sands of the eroded zone are relatively enriched in monazite, zircon, tourmaline, garnet, and rutile.

Late Quaternary sediments from Nal Sarovar, Gujarat, India: Distribution and provenance

A 54-m long core was raised from the bed of the Nal Sarovar, a large shallow lake located in the middle of the low-lying region linking the Gulfs of Kachchh and Khambhat, in western India. A three-layer sequence comprising: Zone-1 (top 3 m), predominantly silty-clay/clayey; Zone-2 (3–18 m), sandy; and Zone-3 (18–54 m), dominated by sticky silty-clay/clayey-silt with occasional thin sand layers and basalt fragments was identified. Smectite and illite are the dominant clay minerals with minor amounts of kaolinite and chlorite. Very high content of smectite (53–97%) in the clays of the lowermost zone (18–54 m) and the geomorphic features of the surrounding region suggested that the sediments were derived from the basaltic terrain of Saurashtra and/or via the Gulf of Khambhat. The clay content in the middle zone (3–18 m), dominantly sandy, is very low. Therefore, provenance for this zone was derived using heavy minerals in the sand fraction. The heavy mineral species in this zone suggested the mixed metamorphic and igneous terrain of Aravallis as the major source. The grain-size distribution of this zone closely matched with the sediments underlying the modern Sabarmati riverbed at Ahmedabad, suggesting fluvial depositional environment. Clays also dominate sediments of the topmost (0–3 m) zone with illite as the dominant (74–81%) specie followed by smectite suggesting derivation from the mixed metamorphic and igneous terrain of Aravallis.

Provenance of the Sardona Flysch, eastern Swiss Alps: example of high-resolution heavy mineral analysis applied to an ultrastable assemblage

The Sardona Flysch of eastern Switzerland was deposited in the northern sector of the embryonic Alpine Foreland Basin, the so-called North Penninic Trough, during the Late Cretaceous-Early Tertiary. The flysch sediments consist of quartz arenites, sublitharenites and arkosic arenites, plus polygenic, pebble to boulder conglomerates. The Sardona Flysch was sourced by a single petrologic province composed of plutonic, Variscan granitoids, gneisses and low-grade, quartzo-feldspathic schists, plus associated cover sediments throughout its sedimentary history. Its heavy mineral suite principally comprises zircon, tourmaline, rutile and varying amounts of apatite, whose distribution cannot be used to characterise the various lithostratigraphic units. However, recording the diagnostic varieties of ultrastable heavy minerals using a ‘high-resolution heavy mineral analysis’ (HRHMA) yielded conclusive results. The varietal distribution of zircon proved especially informative, demonstrating that changes in its distributional trends coincide remarkably well with lithostratigraphic subdivisions and reveal subtle variations in the provenance of the flysch. The limited number of heavy mineral species was predetermined by the low diversity of parent rock lithologies in the hinterland, rather than resulting from high sediment maturity, or progressive removal of unstable species during diagenesis. The basin was structurally confined by the South Helvetic and North Penninic Prättigau Swells, which defined its northern and southern margins, respectively; these structural highs may represent Mesozoic normal fault-blocks reactivated under compressive stresses within the European foreland. They provided detritus to the Sardona flysch basin and prevented the influx of material from the orogenic thrust wedge. Hence, garnet and unstable heavy minerals recycled from medium-grade metamorphic rocks within the mineralogically more diverse Austroalpine thrust wedge are absent from the flysch sediments.

Separation of heavy minerals from mudrocks

The non-clay-mineral fraction of mudrocks is receiving increased attention. The heavy-mineral fraction in fine-grained rocks, however, has largely been neglected, partially because of the difficulty in separating heavy minerals from the host mudrock. We propose a technique that will separate some heavy minerals from a clay matrix. This method was developed initially by soil scientists for separating quartz and feldspar from clays, and later modified for mudrocks. The technique involves fusing the rocks with sodium bisulfate, making clay minerals soluble in basic solutions. We have tested this procedure on nine common heavy minerals: andradite, almandine, grossular, zircon, magnetite, schorl, apatite, rutile, and a gem variety of tourmaline. Each mineral was fused and the mass reduction and resultant chemical changes observed. Physical grain alterations were examined by SEM and chemical changes analyzed by electron microprobe. Almandine, grossular, and zircon survived the fusion process in high percentages and showed little chemical change. Andradite, although it showed small mass loss, was highly etched by the precess. Schorl, gem tourmaline, magnetite, and ruffle showed a high mass loss with some chemical change to the residue. Apatite was totally dissolved. The chemical resistance of several heavy-mineral species makes this technique useful for provenance studies of mudrocks, especially when combined with chemical studies of heavy minerals.

The Heavy Mineral Population Within the Beach Sand Facies of the Meridian Sand Exposed in Mississippi

ABSTRACT The Meridian Sand outcrop exposed across Neshoba, Newton, Lauderdale and Clarke counties, Mississippi, contains sedimentary characteristics which indicate deposition within a mainland or barrier beach setting. Based on the standard deviation of sample means and the sample coefficient of samples from 17 localities, the Meridian Sand can be considered a moderate to well sorted, medium- to fine-grained quartz sand. Sedimentary structures such as bidirectional cross stratification, tabular cross stratification alternating with plane beds, and a dominant Skolithos ichnofacies suggest shoreface to foreshore deposition. The heavy mineral population of the Meridian Sand in this area of Mississippi is 1.43% of the total sand population and occurs within the Wentworth interval of 0.5 mm to 0.125 mm. Opaque minerals, mainly ilmenite and leucoxene, comprise 43.5% of the total heavy mineral population. The dominant nonopaque minerals are staurolite and kyanite, which comprise 22% and 13% of the heavy mineral population respectively. Other nonopaque species include zircon (8.9%), rutile (4.0%), tourmaline (3.6%), sillimanite (0.8%), hornblende (0.4%), and anatase (0.35%). Nonopaque species, found only in trace amounts (<0.1%), include garnet, spinel, andalusite, monazite, fluorite, chloritoid, and mica. The heavy mineral content of the Meridian Sand is mainly concentrated in what appears, from field observation, to be foreshore and upper to middle shoreface placer deposits. High concentrations, up to 5%, occur as localized accumulations in what might be considered back beach or even washover deposits. Variation does occur in the quantity of individual heavy mineral species throughout the exposed Meridian Sand. There is no indication, however, of stratigraphic or lateral variation of the total heavy mineral population.

Sourcelands for the Carboniferous Pennine river system: constraints from sedimentary evidence and U-Pb geochronology using zircon and monazite

Abstract Petrographic and U-Pb isotopic data are presented for Carboniferous sandstones from the Pennine basin ranging from Chadian to Westphalian B in age. Variations in the petrography of these samples, particularly the greater abundance of feldspar in Namurian sandstones reported qualitatively by previous authors, are confirmed by modal analyses. The influx of coarse feldspathic sandstones into the Pennine and Southern North Sea basins in the early Namurian is attributed to a marked increase of sediment yields and discharge due to increased precipitation in the hinterlands. The same detrital heavy mineral species occur throughout the Carboniferous. Zircons are petrographically variable both in colour and degree of rounding. Two major sub-populations are recognized; pink-purple grains and colourless-brown grains. U-Pb isotopic analyses of multi-grain fractions of zircon from five of the samples show very similar age patterns; the sixth sample, a Yoredale sandstone appears to be distinct. Single grain analyses of zircons were used to investigate one sample of late Namurian (Rough Rock) sandstone in detail. Concordant or slightly discordant results demonstrate the presence of: rounded brown grains &gt; 3.5 Ga, rounded purple grains 2.8–3.2 Ga, euhedral purple grains ≥2.9 Ga and clear euhedral grains c . 0.41–0.43 Ga. Monazites are shown to be very suitable for single grain analysis, yielding concordant results more often than zircon. Most of the monazite in the Rough Rock and a Westphalian sandstone are Caledonian (0.41–0.43 Ga) but two individual grains have ages of 0.947 and 2.70 Ga. The isotopic results appear to exclude large areas of the North Atlantic region as potential sourcelands and no presently exposed rocks provide a close match with the inferred sourceland geology; rocks now under the northern North sea and/or between Scotland and Greenland are possible, as yet untested, sources.

THE CHEMICAL AND MINERALOGICAL COMPOSITION OF SOIL PARENT MATERIALS IN NORTHEAST ALBERTA

Seven major parent materials from the Athabasca oil sands area were investigated for detailed mineralogy and chemistry. The clay mineral species identified and quantified were mica, smectite, kaolinite, chlorite and vermiculite. The fine (50–250 μm) sand mineralogical suite was dominated by quartz, with lesser amounts of Na-, K-, and Ca-feldspars, and minor amounts of individual heavy mineral species. Electronoptical examination indicated that the feldspar grains in the parent materials have undergone extensive preglacial weathering. Regional mean levels of all analyzed elements (Al, Ca, Fe, K, Mg, Na, Mn, P, Cr, Co, Cu, Ni, Pb, Sr, V, and Zn), with the exception of Ca, are related to textural variability. The variability of Ca levels within the study area is related to the occurrence of calcareous parent materials. The highest levels of all major, minor, and trace elements were associated with either the Legend unit derived largely from Cretaceous bedrock or with the modern sediments of the Athabasca delta. Key words: Soil parent materials, clay mineralogy, trace element levels, sand mineralogy, feldspar morphology