Heavy Mineral Composition Research Articles

Vendian of the Southern Urals: a review of research at the beginning of the 21st century

Research subject. The author investigates sections of the Vendian stratigraphy in the West Bashkirian subzone, written for an Explanatory Note to sheet N-40 – Ufa of the State Geological Map 1000/3 of the Russian Federation, as well as the results obtained with various thematic (stratigraphic, paleontological, lithogeochemical, paleomagnetic, etc.) studies of theVendian sedimentary sequences of the indicated subzone of the Bashkirian meganticlinorium. Materials and methods. A comparison and analysis of research materials was conducted. The research materials included facts, ideas and arguments in favor of certain conclusions and ideas of various authors. Results. A suggestion was made that studies into the architecture of the Vendian deposits of the Southern Urals, apparently, had almost reached perfection. At the same time, the affiliation of different formations to the regional stages of the Vendian of the East European Platform is still interpreted differently. Studies into the Vendian macro- and microfauna on the western slope of the Southern Urals can only be considered at their nascent stage. The dating of detrital zircons from sandstones of the Asha Group should undoubtedly be continued. For the Vendian of the western slope of the Southern Urals, the first steps have been taken regarding the dating of zircons from volcanic tuffs/ashes. These works are still far from being completed. The peak of paleomagnetic studies into the sedimentary sequences of the Vendian, to a certain extent, may have been passed; nevertheless, these research works should also be continued. Finally, only preliminary steps were taken more than 20 years ago in the study of the chemical composition of heavy minerals, which made it possible to obtain fundamentally new information on the composition and evolution of the sources of clastic material for the sedimentary sequences of the Asha Group. Works of this kind also needs to be continued. Conclusion. The conducted analysis of the studies into the Vendian sedimentary sequences of the Southern Urals published in the first two decades of the 21st century made it possible to identify their strengths and weaknesses, as well as to outline directions for further work.

Detrital zircon geochronology and heavy mineral composition constraints on provenance evolution in the western Pearl River Mouth basin, northern south China sea: A source to sink approach

Investigating the provenance evolution of sedimentary basins with complex tectonic histories is challenging because of the continuously evolving tectonic framework and changing source areas. Pearl River Mouth Basin (PRMB) in the northern South China Sea preserves a large volume of Cenozoic sediments derived from both intrabasinal and extrabasinal sources. However, rare study has been conducted to investigate the provenance evolution of the western PRMB. In this study, we report new detrital zircon U–Pb geochronological and heavy mineral data from the western PRMB, attempting to identify its potential sources and provenance evolution from Eocene to early Miocene. Our data from distinct structural units and formations reveal spatial-temporal differences in provenance. In the northern part, a similar age pattern with a major peak at ∼425 Ma and a subordinate peak at ∼230 Ma is preserved in the Eocene-late Oligocene sediments and suggests that sediments were mainly derived from the Yunkai Massif via Nanduhe River. By contrast, in the southern part, the Eocene-late Oligocene sediments display a dominant age population ranging from 100 Ma to 300 Ma, which implies that the sediments were mainly eroded from nearby Shenhu Uplift and Hainan Island. The heavy mineral data also record such spatial differences in provenance. However, during the early Miocene, the northern and southern parts show similar detrital zircon age patterns with multiple clusters at ∼245 Ma, ∼450 Ma, ∼850 Ma, 970–980 Ma, 1825–1845 Ma, and ∼2500 Ma, indicating that the Miocene sediments across the whole basin were mainly provided by the Pearl River system. The increase of Paleozoic and Precambrian zircons in the lower Miocene sediments suggests a profound provenance shift from multiple nearby sources to the South China Block via the Pearl River between Oligocene and Miocene in the western PRMB, and its timing is posterior to other regions of the PRMB. Finally, four-stage source-to-sink evolution for the PRMB is proposed, showing that sediment provenance in the PRMB is controlled by regional tectonic movement, drainage evolution, and basin architecture. This study suggests that the small-scale drainage system Nanduhe River sourced by Yunkai Massif contributed significantly to the PRMB between Eocene and Oligocene, and highlights its complex processes of provenance evolution that are relevant to the evolution of marginal sea basins globally.

Carbonation of municipal solid waste gasification fly ash: Effects of pre-washing and treatment period on carbon capture and heavy metal immobilization

Carbon capture has become an important technology to mitigate ever-increasing CO2 emissions worldwide, and alkali waste is a potential source of CO2 capture material. Slagging-gasification is a novel technology for treating municipal solid waste (MSW), and the gasification fly ash (GFA) is the only solid residue that is not reused at present due to its high heavy metal content. GFA contains high amounts of Ca(OH)2 and Ca(OH)Cl, making it protentional for CO2 capture. In this study, GFA and washed gasification fly ash (WGFA) were treated with CO2 for different treatment periods. Weight changes of samples were recorded to evaluate the efficiency of CO2 capture. To assess the properties of treated GFA, pH value, leached heavy metal concentration, mineral composition, and microscopic morphology were studied. The results revealed that GFA and WGFA could adsorb 18.8% and 23.7% CO2 of their weights, respectively. Carbonation could immobilize heavy metals including Pb, Zn, and Cu when a proper treatment period was applied. An excessive treatment period decreased the efficiency of heavy metal immobilization. Pre-washing is recommended as a pre-treatment method for GFA carbonation, which increased the efficiency to adsorb CO2, improved the pH of carbonated GFA, and enhanced the effect to immobilize heavy metals.

Effects of Provenance, Transport Processes and Chemical Weathering on Heavy Mineral Composition: A Case Study From the Songhua River Drainage, NE China

Understanding the heavy mineral composition of the Songhua River basin in NE China and the influencing factors (e.g., provenance, transport processes and chemical weathering) is crucial for the study of both the source-to-sink processes and the drainage evolution in the region. To this end, a total of 43 samples were collected from the river bars and terraces of the main and tributary streams of the Songhua River, and analyzed for heavy minerals in different grain-size fractions based on the novel automated TESCAN Integrated Mineral Analyzer (TIMA) combined with standard optical method. The results show that the tributaries originating from different mountains have significantly different heavy mineral composition. The locally occurring basic source signal in the tributaries of the Nenjiang River (the largest tributary of the Songhua River) are not well preserved in the Nenjiang River and the Songhua River trunk streams, indicating that the control of sources on heavy mineral composition is influenced by fluvial processes. Additionally, significant differences in the heavy mineral composition of different reaches of the same river also indicate that the heavy mineral composition is significantly influenced by fluvial processes. Influenced by hydraulic sorting during river processes, heavy minerals are enriched in different size fractions with the low-density minerals systematically overestimated in a wide window, suggesting an advantage of multi-window policy over wide window policy. In contrast to modern river sediments, the original heavy mineral composition of river terrace sediments has been severely damaged due to chemical weathering, so the degree of chemical weathering of terrace sediments needs to be evaluated first in provenance tracing and paleo-drainage evolution studies. TIMA has an irreplaceable role in identifying mineral species, additional images and elemental composition, and however, it performs poorly in identifying polycrystalline minerals, thus the combination with traditional methods can obtain more complete and accurate information.

Geochemical characteristics of Jurassic sandstones on the southern margin of the Junggar Basin: Constraints on provenance and sandstone-type uranium mineralization

Jurassic strata in the southern margin of the Junggar Basin are located in the piedmont zone of the North Tianshan Mountains in Xinjiang, China. Due to multiple tectonic movements, the basin has a complicated history of structural deformation. Accurate reconstructions of the tectonic setting, provenance attributes and paleoclimatic characteristics of the Jurassic strata in the area are vital to facilitate mineral resources prospecting (such as coal, oil, natural gas and uranium) in the basin. Here we used scanning electron microscopy, major and trace elements analyses (including rare earth elements; REE), clay mineralogy and heavy mineral composition in outcrop samples, to analyze the paleoclimate, tectonic setting, source rock properties and provenance characteristics in the southern margin of the Junggar Basin during the Jurassic period. The results are as follows: (1) according to major and trace elements and clay mineral assemblages, the degree of drought increased slightly from the Early Jurassic to the Late Jurassic concomitant increase. (2) Major and minor element discrimination and REE patterns indicate that the material was sourced from continental island arc and active continental margin environments, primarily from upper crustal felsic source rocks (mainly greywacke and arkose). (3) Heavy mineral and whole rock analyses show that the provenances of the Lower Jurassic sandstones were mainly from the primarily Zaire Mountain, North Tianshan Mt.-Middle Tianshan Mt., while the Upper Jurassic sediments were sourced from the primarily North Tianshan Mountain, Zaire Mountain, Middle Tianshan Mountain.

No major temporal provenance variation on the Chinese Loess Plateau since the late Miocene — insight from stable heavy mineral ratios

Heavy mineral assemblages have been demonstrated effective in tracking the dust provenance younger than 500 ka on the Chinese Loess Plateau (CLP). However, prior to 500 ka, diagenetic alternation has proven to affect the validity of heavy mineral assemblage in indicating loess provenance. In order to circumvent this caveat, here we use several previously-proposed ratios of stable heavy minerals to study the dust provenance on the CLP since the late Miocene. These provenance tracers reveal that dust on the CLP is dominantly sourced from the Northeastern Tibetan Plateau with some input from the North China Craton, without significant changes across the late Miocene-Pliocene to Pliocene-Quaternary boundaries. This result is different from previous results based on Sr, Pb isotopes, and transparent heavy mineral composition, but is consistent with Nd and Hf isotopes and detrital zircon U-Pb age results. We argue that the changes based on Sr, Pb isotopes, and heavy mineral assemblages are caused by factors other than provenance changes. We conclude that the CLP has been sourcing dominantly from the Northeastern Tibetan Plateau since the late Miocene and formation of the CLP is genetically linked with existence of a high plateau near its western margin.

New strategy for exploring the accumulation of heavy metals in soils derived from different parent materials in the karst region of southwestern China

Heavy metals with high average background values in soils from karst regions of China have been reported previously. However, the accumulation mechanism of heavy metals in karst soils derived from different parent materials related to the molecular soil chemistry is still unclear. In this study, six soil cores (0–100 cm) from three locations were collected from Hengxian County, a typical karst basin of Guangxi, among which soils of Maling (ML1 and ML2) were derived from the weathering and leaching residues of carbonate rocks, and soils of Yunbiao (YB1 and YB2) and Dengxu (DX1 and DX2) were mainly developed from deposits of Quaternary formations. Soil heavy metal quantification, X-ray diffraction (XRD) analysis, synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectroscopy, and two-dimensional correlation spectroscopy (2DCOS) analysis were combined to study the contents of heavy metals, mineral compositions, and functional assignments in the karst soils. The results showed that the total concentrations of As, Cr, Cd, Cu, Ni, Pb, and Zn in the soils from ML exceeded the risk screening values from the agricultural soil quality standard in China (GB15618-2018), while the contents in the soils from YB and DX were below the risk screening values. The mineral components were significantly different in soils and their clay minerals. ML soils contained more Fe and Mn oxides than YB and DX soils. Furthermore, it was interesting to find extensive existence of chlorite in ML soils (36.73%-39.07%) and their clay minerals (90.49%-90.97%). While illite was the dominant mineral in YB and DX clay fractions (75.08%-100%) and its percentages decreased to 6.06%-35.23% in the soil samples. In addition, ML soils contained the hydroxyl groups with hydrogen bonds (vO-H: 3523, 3450, and 3378 cm−1) and the hydroxyl groups without hydrogen bonds (vO-H: 3698, 3623 cm−1), while YB and DX soils only had the hydroxyl groups without hydrogen bonds (vO-H: 3695, 3622 cm−1). Our study indicated that the accumulation of heavy metals in karst soils from different parent materials was significantly attributed to their molecular soil chemistry. For instance, the higher contents of Fe-Mn oxides and more reactive vO-H (3523, 3450, and 3378 cm−1) and vSi-O (1000 cm−1) assignments could contribute to the higher contents of heavy metals in ML soils compared to the soils from YB and DX.

Provenance and tectonic setting of the Gudongjing Group in Beishan Orogen

增生造山带中陆源碎屑岩物源区特征的研究可为解剖造山带结构甚至大陆地壳的形成和演化提供关键证据。北山造山带中部的古硐井群被认为是前寒武纪稳定沉积盖层，是北山造山带存在微陆块的重要依据。本文围绕古硐井群的物源区特征，进行了碎屑颗粒和重矿物统计、全岩主微量元素地球化学分析、碎屑锆石U-Pb年代学和Hf同位素测试。古硐井群碎屑岩的碎屑颗粒多呈棱角状，主要为石英、长石，同时含大量硅质岩碎屑和一定数量的火山岩碎屑；重矿物组成以褐铁矿、锆石、白钛石、尖晶石为主，角闪石、电气石、辉石次之，暗示物源区可能存在蛇绿岩、增生杂岩。全岩主量元素以高硅、高铝、富碱、低锰为特征，结合REE、Cr、Co、Sc和Th等惰性元素含量特征共同指示了长英质的物源区。最年轻的碎屑锆石年龄为443.9±13Ma，表明古硐井群最大沉积时限为晚奥陶世。碎屑锆石的年龄高度集中于470Ma附近，且该区间锆石ε_Hf（t）值多为正值，指示物源区存在大量新生地壳物质。本文推测古硐井群可能形成于增生楔楔顶盆地；研究结果支持北山造山带是古生代持续增生造山的产物这一认识。;The clastic sedimentary rocks in an accretionary orogenic belt may preserve key evidence for understanding the architecture of orogenic belts and even the crustal evolution. The clastic sedimentary rocks of the Gudongjing Group in the middle of the Beishan Orogen is considered to be a set of stable sedimentary caprocks of the Precambrian, and it is also an important basis for the existence of micro-continents in the Beishan Orogen. In this paper, statistics on clastic particle grain sizes and heavy mineral compositions, the whole rock geochemical composition analyses, detrital zircon U-Pb dating, and Hf isotope testing are carried out on the clastic rocks of the Gudongjing Group to reveal their prevenances and tectonic settings. The clastic components of the rocks are mainly composed of quartz, feldspar and rock fragments which are mainly siliceous rock fragments together with a certain amount of volcanic ones. Heavy mineral analysis reveals they mainly consist of limonite, zircon, ilmenite and spinel, followed by hornblende, tourmaline and pyroxene, which indicates the contribution of the accretionary complex materials and ophiolites to their provenance. The whole rock major element compositions are characterized by high contents of silicon, aluminum and alkali, while low in manganese. The contents of the inert elements, such as REE, Cr, Co, Sc, Th, etc., show characteristics of a felsic source area. The youngest detrital zircon age obtained in this study is 443.9±13Ma, indicating that the maximum deposition age of the Gudongjing Group is Late Ordovician. The age of detrital zircons is highly concentrated around 470Ma, and the corresponding zircon ε_Hf(t) values are mostly positive, indicating a large number of new crustal materials have developed in their provenance area. Based on the comparative analysis, it is suggested that these clastic rocks are possiblely formed in a slope basin on the top of an accretionary wedge. The results support the point that the Beishan orogenic belt is the product of a continuous accretion of a Paleozoic orogenic belt.

Clay mineralogy fingerprinting of loess-mantled soils on different underlying substrates in the south-western Poland

Loess may be integrated into slope deposits at different soil depths and may influence related physical, chemical and mineralogical soil properties. Therefore, tracking the border between deposited loess and underlying materials and estimating the depth of loess penetration is a challenge. Five soils from the Lower Silesia province in south-western Poland having different types of geologic substrate and being covered by loess deposits of various thicknesses were chosen to: 1) trace the origin of phyllosilicates in these heterogeneous soils (loess vs. underlying bedrock); 2) determine the influence of the geologic substrate and the loess mantle on clay mineral transformation in the soil; and 3) relate clay mineralogical traits to soil morphology. The loess consisted of long-distance and local aeolian sources as shown by the Ti/Zr ratios and heavy mineral composition. Geochemical and mineralogical traces of loess were easily detected in the mixed zone and in part also in the basal layer. The loess deposits are characterised by mica, chlorite, kaolinite, interstratified mica-vermiculite or hydroxy-interlayered vermiculite, vermiculite and a minor amount of smectite. Aeolian silt admixture was an important source of chlorite at all sites. The vertical distribution of mica indicated two types of sources — loess input and substrate. Smectite, however, has mostly been inherited from the underlying bedrock (serpentinite, glacio-fluvial deposits and basalt slope sediment) or was formed in the soils from mica or chlorite. Where present in the loess, smectite was only found in small amounts. The presence of kaolinite, HIV and mixed layered mica-vermiculite could be derived either from aeolian input or neoformation and thus actively occurring mineral (trans)formation reactions. Similar to mica, vermiculite was derived from both aeolian input and the geological substrate. The widespread loess deposits in this region rejuvenated the soil formation process, as evidenced by their mineralogical and chemical composition.

Heavy Mineral Compositions of Sediments in the Southern Okinawa Trough and Their Provenance-Tracing Implication

Heavy mineral assemblages have been widely used to effectively trace sediment sources. Heavy mineral assemblages are rarely used in research to trace sediment sources in the southern Okinawa Trough compared with geochemical proxies. In this study, the TESCAN Integrated Mineral Analyzer (TIMA) revealed the full-size heavy mineral assemblages in the five layers of the core sediment H4-S2 in the southern Okinawa Trough. During the past 700 years, the heavy mineral assemblages in the sediments of the southern Okinawa Trough were very similar to the East China Sea shelf/Yangtze River, mainly composed of mica and chlorite; dolomite; actinolite; and hematite/magnetite. The grain size distribution of heavy minerals is in the clay–sand range and mainly in silt. Actinolite and hornblende can indicate the supply of sediments from the East China Sea shelf/Yangtze River to the southern Okinawa Trough. Due to their complex sources, pyrite, epidote, and hematite/magnetite are not adequate indicators for distinguishing between the different provenance areas. Because previous studies have used a variety of analytical methods, especially using heavy liquids with different densities, dolomite cannot be used as a marker for sediments on the Yangtze River/East China Sea shelf. Therefore, the East China Sea shelf/Yangtze River is a vital provenance of sediments from the southern Okinawa Trough since the late Holocene period.

Detrital Zircon Perspectives on Heavy Mineral Sand Systems, Eucla Basin, Australia

Abstract Southern Australia’s Cenozoic Eucla basin contains world-class strandline heavy mineral deposits. This study links detrital zircon U-Pb geochronology and heavy mineral compositions from four mineral sand prospects, and a suite of published deposits, to bounding Archean to Neoproterozoic crustal areas. A variable number of distinct sediment sources is recorded from each prospect’s detrital zircon age spectrum. This variability in zircon ages, quantified using a Shannon-Weaver test, serves as a metric of source region heterogeneity. Greater zircon age heterogeneity correlates with heavy mineral enrichment. Enhanced heavy mineral yields reflect retention of resistate over labile minerals—a function of greater sediment transport, reworking, and upgrading processes that parallel those that result in detrital zircon age polymodality. In this case study, greater reworking in intermediate storage sites and transport by longshore processes, eastward along the ~1,000 km spanned by the study sites, corresponds to the direction of progressive heavy mineral enrichment identified in zircon ages and mineral compositions. This approach is a proxy for the duration minerals have spent in the sedimentary system and provides an important perspective for understanding heavy mineral sands.

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.

Chemical Properties of Heavy Metal-Contaminated Soils from a Korean Military Shooting Range: Evaluation of Pb Sources Using Pb Isotope Ratios

In this study, the geochemical properties of heavy metal-contaminated soils from a Korean military shooting range were analyzed. The chemical behavior of heavy metals was determined by analyzing the soil pH, heavy metal concentration, mineral composition, and Pb isotopes. In total, 24 soil samples were collected from a Korean military shooting range. The soil samples consist of quartz, albite, microcline, muscovite/illite, kaolinite, chlorite, and calcite. Lead minerals, such as hydrocerussite and anglesite, which are indicative of a transformation into secondary mineral phases, were not observed. All soils were strongly contaminated with Pb with minor concentrations of Cu, Ni, Cd, and Zn. Arsenic was rarely detected. The obtained results are indicated that the soils from the shooting range are contaminated with heavy metals and have evidences of different degree of anthropogenic Pb sources. This study is crucial for the evaluation of heavy metal-contaminated soils in shooting ranges and their environmental effect as well as for the establishment of management strategies for the mitigation of environmental risks.

Heavy mineral composition and texture of the recently formed fluvial delta sediment of Lake Nasser/Nubia, Egypt and Sudan

Surficial sediment samples collected from the recently formed fluvial delta in Lake Nasser/Nubia (Egypt and Sudan) in conjunction with data on bottom current and depth soundings are examined to interpret hydraulic-sorting processes and transport/depositional patterns. The ~500 km long northeastward-trending lake, lies within Egypt and Sudan, is created as a result of the construction of the Aswan High Dam in 1964. The original grain-size distribution and heavy mineral compositions of these samples help to characterize the classical depositional features of the recently formed underwater delta-front and prodelta depocenters. Starting from the south, those delta-front deposits, which floor most of the narrow-shallow basin of Lake Nubia, are characterized by thick coarse-grained sandy deposits, rich in heavy minerals (averaged 12.8%). This delta-front is followed to the northeast by thin layers of prodelta mud, poor in heavy mineral contents (averaged 0.6%). These layers cover the entire broad basin of Lake Nasser. The northeasterly downslope fining-trend, along with a continuous decrease in heavy mineral composition, along the length of the lake, are attributable to processes of grain sorting, which take place due to contrasting densities and grain sizes. These processes lead to the concentration of heavy mineral placer, mostly in the delta-front samples. The sorting mechanism, in turn, is controlled by the interplay of unidirectional-directed northeastward current, physiographic characteristics of the lake, including topographic configuration, geometry (cross-section), and floor topography (slope gradient). In terms of mineral exploration, the highest proportion of mineral grades in the delta-front sediments is likely to be considered as a viable source for economic placers that require more planning initiatives for industrial and commercial evaluation.

Heavy mineral record from the east China sea inner shelf: Implications for provenance and climate changes over the past 1500 years

The heavy mineral composition and sensitive grain size changes from core SS4 retrieved from the mud wedge on the East China Sea inner shelf have been studied for better understanding provenance variations in the sediment and climate changes during the last ~1500 yr. High dolomite content and occurrence of ubiquitous polysynthetic mica indicate that the sediments in core SS4 were mainly derived from the Yangtze River, while the relatively high epidote content represent the contribution of small local rivers from Zhejiang and Fujian provinces. The substantial decrease in the epidote/hornblende ratio since ~730 yr BP manifests a decline in the relative contribution of sediment from the small local rivers to the core. We propose that the changes in drought/flood conditions in response to the East Asian winter monsoon (EAWM) and human activities might have been mainly responsible for changes in sedimentary characteristics. During 1400–730 yr BP, the core sediments were characterized by relatively finer sensitive grain size and high epidote/hornblende ratio, due to a possibly weaker EAWM (i.e., less Yangtze River-derived sediment transported by the southward coast current). This time interval coincides with the Sui-Tang Warm Period (1400–1130 yr BP) in China and the Medieval Warm Period (1000–730 yr BP) on a broader regional scale. The prolonged warm periods were, however, interrupted by three short cold phases at 1350–1280 yr BP, 1130–1000 yr BP and 870–750 yr BP, characterized by coarse sensitive grain size and decreased epidote/hornblende ratio. Between 360 and 150 yr BP, the sensitive grain size significantly coarsened, which corresponded to the Little Ice Age. Our new findings suggest that sedimentation processes of mud wedge formation are responsive to natural environmental change and human activity.

Provenance of the Phuquoc Basin fill, southern Indochina: Implication for Early Cretaceous drainage patterns and basin configuration in Southeast Asia

Cretaceous basins cover large parts of mainland SE Asia. Yet, the development during the Cretaceous is poorly understood including the establishment of the Cretaceous basin configuration. Based on detrital zircon and heavy mineral analysis, this study investigates the provenance of Lower Cretaceous deposits in the Phuquoc Basin, exposed in Cambodia and SW Vietnam and extending into the Gulf of Thailand. Our results document five major zircon populations with 130–145 Ma, 145–200 Ma, 200–270 Ma, 420–470 Ma, 1800–1900 Ma ages and two subordinate 2400–2700 Ma, 750–1000 Ma age clusters. These ages resemble those of the Qinling-Dabie and the Songpan-Ganzi orogenic belts and differ from other Asian terranes. These ages suggest that the Qinling-Dabie and Songpan-Ganzi orogenic belts were major sources of sediment for the Phuquoc Basin in the Early Cretaceous. Heavy mineral compositions including the presence of almandine, often co-occurring with silimanite and epidote, suggest metamorphic and granitic constituents in the hinterland, compatible with these orogenic belts being the source.The detrital zircon age pattern of the Phuquoc Basin closely resembles the zircon ages in Khorat and the Sichuan basins, suggesting a common sediment source, and bears great similarities with mid-Cretaceous strata in the Lanping-Simao Basin. These basins share a remarkable lithostratigraphic similarity and are confined by erosion. Taken altogether, this supports that the Phuquoc, Khorat, Sichuan, and probably the Lanping-Simao basins, formed part of a Cretaceous basin covering much of central SE Asia segregated by Late Cretaceous and Cenozoic denudation and translation. The absence of 130–145 Ma and 145–200 Ma aged zircons in the Lanping-Simao Basin suggests that another drainage system sprang from the Songpan-Ganzi Orogenic Belt and fed into this basin before merging with the Qinling-Dabie Orogenic Belt drainage system south of the Sichuan Basin. The combined drainage system likely passed through the Khorat Basin before entering the Phuquoc Basin.

Heavy Metal Content and Physico-Chemical Analyses of Soils under the Litter of some Medicinal Taxa in the Luki Biosphere Reserve, Democratic Republic of the Congo

Aim: The aim of this study was to compare the texture, mineral element and heavy metal content of the soil under the litter of different selected species in relation to the plan of their pedogenesis.
 Methods: The granulometric analysis of the various samples based on laser diffraction, measurements of Total Nitrogen and Total Organic Carbon were performed using the Elemental Analyzer, the Organic Matter content is estimated by the loss of ignition method using a Salvis furnace, In order to estimate the CaCO3 content. The same samples were heated in the oven at 1000°C for 60 minutes and reweighed. The carbonate content is estimated by the loss in mass during this second firing, multiplied by 2.274 which is the molecular weight ratio between CaCO3 and CO2. The heavy metal and mineral composition was evaluated by ICP-AES and AAS.
 Results: The granulometric analyses show a sandy texture, according to the FAO classification. The organic matter content thus observed in the soils under the litter of these four species did not show any significant difference. The concentration of major mineral elements recorded in soils under the litter of Blighia welwitchii, Oncoba welwitschii, Zanthoxylum gilletii and Harungana madagascariensis did not show any significant difference. However, potassium, phosphorus, and magnesium have a high concentration compared to calcium and sodium. This study showed that the levels of cadmium, lead, arsenic and aluminum in the various samples of litter soils of all plant species including nickel for B. welwitschii are above the standards set by the Canadian Council of Ministers of the Environment for soil quality. Pollution factors for aluminum are the highest. This indicates that aluminum is the most polluting metal. The low pollution factors for lead and nickel are due to the low fixation of these metals by soils.
 Conclusions: Our study took place in the Luki Biosphere reserve and showed that the different soils under litter are polluted by very toxic and persistent heavy metals such as cadmium, lead, aluminum, arsenic and nickel. This study has revealed new aspects of heavy metal pollution. This pollution represents a serious threat to the environment in general and to humans in particular through the food chain.

ТЯЖЕЛЫЕ ОБЛОМОЧНЫЕ МИНЕРАЛЫ КАК ИНДИКАТОР ГЕОДИНАМИЧЕСКИХ ОБСТАНОВОК НАКОПЛЕНИЯ И ИСТОЧНИКОВ ПИТАНИЯ МЕЛОВЫХ ОТЛОЖЕНИЙ ЗАПАДНО-САХАЛИНСКОГО ТЕРРЕЙНА

The article discusses the results of studying heavy clastic minerals from the Cretaceous sandy rocks of the West Sakhalin Terrane, and also presents their paleogeodynamic interpretation. It is shown that in terms of mineralogical and petrographic parameters, the terrane sandstones correspond to typical graywackes and are petrogenic rocks formed mainly by destruction of igneous rocks of the source areas. The sediments were found to contain both sialic, granite-metamorphic association minerals, and femic, formed by products of the destruction of basic and ultrabasic volcanic rocks. The interpretation of the entire set of data on the content, distribution and microchemical composition of heavy minerals was carried out by comparing them with minerals from older rocks and modern sediments accumulated in known geodynamic settings. The results obtained indicate that during the Cretaceous, sedimentation occurred along the continent-ocean boundary in a basin associated with large-scale left-lateral transform movements of the Izanagi Plate relative to the Eurasian continent. The source area that supplied clastic material to that basin combined a sialic landmass composed of granite-metamorphic and sedimentary rocks, a mature deeply dissected ensialic island arc, and fragments of accretion prisms, in the structure of which involved ophiolites.

Detrital zircon geochronology and heavy mineral analysis as complementary provenance tools in the presence of extensive weathering, reworking and recycling: the Neogene of the southern North Sea Basin

AbstractHeavy mineral analysis is a long-standing and valuable tool for sedimentary provenance analysis. Many studies have indicated that heavy mineral data can also be significantly affected by hydraulic sorting, weathering and reworking or recycling, leading to incomplete or erroneous provenance interpretations if they are used in isolation. By combining zircon U–Pb geochronology with heavy mineral data for the southern North Sea Basin, this study shows that the classic model of sediment mixing between a northern and a southern source throughout the Neogene is more complex. In contrast to the strongly variable heavy mineral composition, the zircon U–Pb age spectra are mostly constant for the studied samples. This provides a strong indication that most zircons had an initial similar northern source, yet the sediment has undergone intense chemical weathering on top of the Brabant Massif and Ardennes in the south. This weathered sediment was later recycled into the southern North Sea Basin through local rivers and the Meuse, leading to a weathered southern heavy mineral signature and a fresh northern heavy mineral signature, yet exhibiting a constant zircon U–Pb age signature. Thus, this study highlights the necessity of combining multiple provenance proxies to correctly account for weathering, reworking and recycling.

Sediment provenance and tidal current-driven recycling of Yellow River detritus in the Bohai Sea, China

A detailed sediment-provenance study is presented on the modern Bohai Sea, China, the innermost gulf of the Yellow Sea, using framework petrography, heavy-mineral and grain-size analyses. A series of subaqueous river deltas, characteristic of multisource, is distinguished along the coastal zone. First-cycle fluviodeltaic sediments are attributed principally to three large source areas: the Loess Plateau, the Yanshan highlands, and the Horqin sandland. Coastal sands along eastern Liaodong Bay are produced by weathering and physical erosion of near-source Mesozoic granitoid rocks during Quaternary lowstands. Apart from subaqueous deltas and coastal sands, sediment provenance is only attributed to two end-member mixing with various proportions between recycled Holocene Yellow River sediments and ancient fluvial sediments of the Liaohe river system, even though detrital sources are multiple along the coast. Relative contributions are quantified on a ternary diagram of heavy-mineral compositions, using the proportion of relative distances between a given mixed area and the two end-member deltas. The eastern Bohai flood-tidal delta, characterized by abundant garnet and ilmenite, is regarded as a large repository of ancient Liaohe sediments, which had been intermittently accumulated during Quaternary lowstands and reworked during multiple transgressions. As a secondary sediment source detached from the present-day Liaohe River delta, it is remobilized and involved in the modern sedimentation. A complete tidal current-dominated depositional pattern is proposed throughout the Bohai Sea to explain sediment accumulation and recycling. We suggest that dominant ebb tidal currents, prevailing in the southern Bohai Strait, are a primary driver carrying fine-grained Yellow River sediments eastward to the Yellow Sea. In contrast, the recycling of Yellow River sediments is driven by flood tidal currents, prevailing in the northern Bohai Strait. The internal recycling process in the Bohai Sea builds the sand sheet and its terminal lobe, i.e., the eastern Bohai mud belt, whereas the external recycling process that involves the depocenters of Yellow River sediments in the outside North Yellow Sea builds the sand ridges and its terminal lobe, i.e., the quartz-rich area. This study improves our understanding on the Yellow River dispersal system. It also provides a typical example that demonstrates how ancient alluvial sediments accumulated during eustatic lowstands are reactivated and join the modern sedimentation processes.