Heavy Mineral Analysis Research Articles

Multiple provenance of rift sediments in the composite basin-mountain system: Constraints from detrital zircon U-Pb geochronology and heavy minerals of the early Eocene Jianghan Basin, central China

Zircon U-Pb geochronology and heavy minerals are used in combination to provide valuable insights into the provenance of the early Eocene Jianghan Basin, central China. Five samples for zircon U-Pb dating and eighty-five samples for heavy mineral analysis were collected from drill cores or cuttings of the Xingouzui Formation. Most analyzed zircons are of magmatic origin, with oscillatory zoning. Detrital zircons from sample M96 located on eastern basin have two dominant age groups of 113–158Ma and 400–500Ma, and the other samples located on southern basin have three prominent age populations at 113–158Ma, 400–500Ma and 700–1000Ma. Samples on different parts of the basin show distinct differences in heavy mineral compositions and they apparently divide into two groups according to the content of rutile (higher or lower than 4%). The spatial variations of zircon-tourmaline-rutile (ZTR) indices are marked by some noticeable increasing trends from basin margins to the inner part of the basin. Compared with the potential source areas, this study clarifies the multiple source characteristics of the Jianghan basin in the composite basin-mountain system. The majority of clastic material was supplied from the north source area through rift-trough sediment-transport pathways, and the eastern, southern and northwestern source areas also contributed detritus to the basin. This clastic material is broadly dispersed in the basin. The early Eocene paleogeography implies that rift architecture and rifting process had an important influence on sediment dispersal. This study shows that integrated zircon U-Pb geochronology and heavy mineral analysis is a useful and powerful method to identify sediment provenance.

What generated the Late Permian to Triassic unconformities in the southern Junggar Basin and western Turpan Basin; tectonic uplift, or increasing aridity?

The Upper Permian to Triassic sedimentary successions of the southern Junggar Basin and western Turpan Basin are characterized by widespread unconformities. However, the origin of these unconformities remains highly controversial. Three sections, namely the Jimsar section in the southern Junggar Basin and the Aiweiergou and Yuergou sections in the western Turpan Basin, have been systematically studied using detrital zircon U-Pb geochronology, heavy mineral assemblages, and whole-rock geochemical analyses. Detrital zircon ages show that both Upper Permian and Triassic samples from each section have similar age distributions, with a major age group at 250–380Ma, a subordinate age group at 380–540Ma, and sporadic Precambrian ages, suggesting that the main provenance areas were the North Tian Shan and the northern margin of the Yili-Central Tian Shan, with a secondary source area in the Yili-Central Tian Shan. REE distributions and trace element crossplots also indicate that Upper Permian and Triassic samples display similar characteristics in both basins; all were sourced from felsic or mixed mafic/felsic rocks, with only a minor component of ancient or recycled sediments. Detrital provenance and geochemical analyses agree in showing no significant changes in the source-to-sink sediment transport system from the Late Permian to the Triassic. However, field observations, heavy minerals analysis, and geochemistry do suggest that both the southern Junggar Basin and western Turpan Basin experienced an arid climate during this interval. Both Upper Permian and Triassic sediments in the two basins contain abundant hematite, display low CIA values and Th/U ratios, and have mudcracks, redbeds, and other indicators of arid climate. Therefore, we suggest that the regional unconformities in the two basins were not generated by regional tectonic uplift, but most likely resulted from an increasingly arid climate.

Provenance of the Upper Triassic siliciclastics of the Mecsek Mountains and Villány Hills (Pannonian Basin, Hungary): constraints to the Early Mesozoic paleogeography of the Tisza Megaunit

The Tisza Megaunit in the Southern Pannonian Basin formed part of the southern margin of the European Plate in the Early Mesozoic era. Its exact paleo-position and relation to other structural blocks is disputed for a long time. Detrital zircon U–Pb dating, heavy mineral analysis and petrographical examination of Carnian to Pliensbachian sandstone members lead to better understanding of the provenance of clastic deposits after the Ladinian–Carnian carbonate to siliciclastic facies shift in the Southwestern Tisza Megaunit. Investigations allow for constraining its paleogeographic relation to adjacent units. The Carnian and Pliensbachian siliciclastics of the Villany Hills derive from inside the Southwestern Tisza Megaunit, i.e. the medium-grade polymetamorphic rocks of the adjacent Slavonian Mountains or similar basement fragments. The Upper Triassic clastic deposits of the Mecsek Mountains most likely derive from Variscan felsic plutonic rocks of the local basement or partially from the Southern/Southwestern Bohemian Massif. About 200 Ma zircon U–Pb ages are tentatively interpreted as traces of synsedimentary distal volcanism in the Central Atlantic Magmatic Province.

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.

Provenance of Triassic sandstones on the southwest Barents Shelf and the implication for sediment dispersal patterns in northwest Pangaea

Thick Triassic siliciclastic units form major reservoir targets for hydrocarbon exploration on the Barents Shelf; however, poor reservoir quality, possibly associated with variation in provenance, remains a key risk factor in the area. In this study, sandstone dispersal patterns on the southwest Barents Shelf are investigated through petrographic and heavy mineral analysis, garnet and rutile geochemistry and zircon U-Pb geochronology. The results show that until the Early Norian Maximum Flooding Surface, two contrasting sand types were present: (i) a Caledonian Sand Type, characterised by a high compositional maturity, a heavy mineral assemblage dominated by garnet and low chrome-spinel:zircon (CZi) values, predominantly metapelitic rutiles and mostly Proterozoic and Archaean detrital zircon ages, interpreted to be sourced from the Caledonides, and (ii) a Uralian Sand Type, characterised by a low compositional maturity, high CZi values, predominantly metamafic rutiles and Carboniferous zircon ages, sourced from the Uralian Orogeny. In addition, disparity in detrital zircon ages of the Uralian Sand Type with contiguous strata on the northern Barents Shelf reveals the presence of a Northern Uraloid Sand Type, interpreted to have been sourced from Taimyr and Severnaya Zemlya. As such, a coincidental system is inferred which delivered sand to the Northern Barents Shelf in the late Carnian/early Norian. Following the Early Norian Maximum Flooding Surface, a significant provenance change occurs. In response to Late Triassic/Early Jurassic hinterland rejuvenation, supply from the Uralian Orogen ceased and the northern Scandinavian (Caledonian) source became dominant, extending northwards out on to the southwest Barents Shelf. The data reveal a link between reservoir quality and sand type and illustrate how provenance played an important role in the development of clastic reservoirs within the Triassic of the Barents Shelf.

GRAIN SIZE AND HEAVY MINERAL ANALYSES OF TWO BOREHOLES IN RECENT TO MIOCENE AQUIFER IN BENIN FORMATION

Recent studies have revealed that groundwater contamination is dependent on the porosity and permeability of the overlying and underlying bed rocks and the mineral composition of the aquifer geometry with respect to depth. This study became important due to several reports on groundwater contamination and in order to understand the mineral composition and the grain sizes of the aquifer in the study areas. Two boreholes were drilled 4.2km apart; one at Okabere and the other at Evbuabogun community both in Ikpoba-Okha Local Government Area of Edo State. The communities have been merged with the capital city as a result of urbanization and population growth. Grain size and heavy mineral analyses were carried out on the soil samples collected from the boreholes at an interval of 15ft. The results obtained indicate that the heavy minerals in Okabere borehole is dominated by Zircon, Tourmaline, Rutile, Biotite and Garnet while Evbuababegun borehole is mainly of Zircon, Kyanite, Rutile, Staurolite, Garnet and Tourmaline which indicate that the sediments were of igneous and metamorphic origin. Grain size analysis of both wells show that mean, inclusive standard deviation, skewness and kurtosis generally indicates very coarse sand to medium sand; very well sorted to moderately sorted and very platykurtic in nature. The foregoing revealed that the aquifer geometry of the study areas is unconfined and vulnerable to contamination. It is recommended that groundwater quality assessment study should be carried out in order to determine the potability of the groundwater bodies. http://dx.doi.org/10.4314/njt.v35i4.37

Sedimentology, diagenesis and reservoir quality of the upper Abu Gabra Formation sandstones in the Fula Sub-basin, Muglad Basin, Sudan

Successful hydrocarbon exploration of the Lower Cretaceous Abu Gabra Formation has established the need to understand the diagenesis and reservoir quality of the sandstones reservoirs in the area. Therefore, this study contains a subsurface facies analysis based on description of three conventional cores from the Moga21-2 well. Methods include wireline log analysis, a petrographic study with both thin sections and scanning electron microscope investigations, grain-size, X-ray diffraction (XRD), and heavy minerals analysis of the Abu Gabra sandstone.Sedimentary composition and facies sequences of the well logs indicate a complex fluvial channel paleo-environment. Grain-size analysis revealed that the sandstone is a mixture of mainly sand-size (<0.01–2.00 mm) along with minor amount of silt and clay size (<0.063 mm). Alternation of coarse to medium-grained, massive to cross-bedded sandstones with fine-grained ripple laminated sandstones shows a sequence of fluvial channel fill or sand deposits of channel bars. The finer-grained facies association, predominantly mudstone and siltstone, represents overbank deposits or floodplain sediments.Petrographically, the sandstones are classified (based on standard rock classification schemes) into, subfeldspathic arenites, and feldspathic arenite lithofacies. Quartz grains are the most abundant detrital components in the samples (both polycrystalline and monocrystalline), followed by feldspars (mainly K-feldspar), micas, and detrital and authigenic clays with carbonatic detritus. Although, lithic fragments, iron oxides and heavy minerals occur in minor amounts, presence of sillimanite, epidote and hornblende (compared to zircon, tourmaline and rutile), as well as the presence of chlorite, the dominance of polycrystalline quartz and high crystallinity of kaolinite could be responsible for the low grade metamorphism. Kaolinite is an authigenic component, while quartz overgrowths occur in variable quantity and carbonates (calcite and siderite) in a relatively minor amount. Pore types are basically primary and secondary interparticle, with few secondary intraparticle pores due to the dissolution of feldspars. Although porosity ranges from 9.20 to 31.20%, the presence of kaolinite, carbonate, and quartz overgrowth cement reduce the porosity of the samples.Analyzed samples are characterized by poor to very good pore interconnectivity. Despite the fact that most of the sandstones display point, concavo-convex, and long contacts with poor to good compaction, few sutured grain contacts (which reflect a higher degree of compaction) still exist. XRD and SEM analyses show that kaolinite, chlorite, illite, smectite, and illite/smectite mixed layer clay are the common clay minerals in the studied samples. The presence of vermiform morphology, besides the sharp peak pattern of the kaolinite, in most of the XRD pattern indicates that part of the kaolinite was authigenically formed.

Heavy mineral and zircon age constraints on provenance of the Sherwood Sandstone Group (Triassic) in the eastern Wessex Basin, UK

Heavy mineral and zircon age data demonstrate that in the Sherwood Sandstone Group of the Marchwood-1 and Southampton-1 boreholes, on the eastern margin of the Wessex Basin, sediment was supplied from both the south (Variscan highlands) and the east (recycled Old Red Sandstone). Interplay of these two sources led to a well-defined heavy mineral stratigraphy in the area. However, the Sherwood Sandstone Group in the Wytch Farm oilfield, towards the centre of the Wessex Basin, contains only sandstones derived from the Variscan highlands to the south and lacks significant amounts of recycled Old Red Sandstone detritus. The equivalent sandstones (Otter Sandstone Formation) on the western margin of the Wessex Basin have a different provenance to both the central and eastern parts of the basin, since they almost entirely lack input from Variscan granitoids. Heavy mineral and zircon provenance data therefore demonstrate sediment input from a number of discrete source areas into the Wessex Basin during the Early and Middle Triassic, and that the ‘Budleighensis River’ system may not have been a single river, at least in the southern Wessex Basin area. It is also evident that provenance-based correlation schemes such as heavy mineral analysis or whole-rock geochemistry should be used with caution over long distances and require careful evaluation of lateral changes in provenance.

Heavy-mineral analysis and provenance of Yellow River sediments around the China Loess Plateau

In its upper-middle reaches the Yellow River has high sand contents after traversing through large areas of desert and the China Loess Plateau. Understanding riverbed sediment composition in the channel is critical for the interpretation of the potential provenance, aeolian sand transport and the linkage between the Loess Plateau and the Yellow River. To address these issues, we collected 52 samples from the modern riverbed, proximal deserts, and major tributaries and used analyses of grain size, grain morphology, and heavy-mineral compositions, to establish the spatial distribution and characteristics of source regions and riverbed sediments. The heavy-mineral assemblages demonstrate significant variations for the different sections of the Yellow River. The riverbed samples from the upper reach are dominated by opaque minerals (limonite and magnetite), amphibole and epidote, with minor zircon, tourmaline and rutile. Riverbed sediments from the middle reach are garnet-rich, reflecting the widespread distribution of Mesozoic sandstones. This variability closely reflects the source regions. Our data show that seasonal tributaries (the “Ten Great Gullies”) carrying detritus from the Ordos Plateau may account for the localized high garnet concentrations in the Inner Mongolia section of the upper reach. Scanning electron microscope (SEM) imaging of quartz grains show that the river sediments are characterized by composite microtextures acquired in both fluvial and eolian environments of the Hedong, Ulan Buh and Kubuq Deserts. The mineralogical composition in the upper reach (Lanzhou–Yinchuan) is similar to that of sediments in the Loess Plateau and Northeast Tibet Plateau (Western Lanzhou). However, the composition differs markedly from that in the Inner Mongolia section of the upper and middle reaches. This variation indicates that in the upper reach the Northeast Tibet Plateau contributes significant volumes of sediment to the Yellow River and Loess Plateau, but compositions change across the Inner Mongolia section of the upper and middle reaches owing to local sediment supply from arid desert areas and seasonal tributaries.

Provenance of middle to late Palaeozoic sediments in the northeastern Colombian Andes: implications for Pangea reconstruction

ABSTRACTGlobal-scale Palaeozoic plate tectonic reconstructions have suggested that Laurentia was obliquely approaching against the northwestern margin of Gondwana until the final agglutination of Pangea. In this contribution integrated petrographic analysis, heavy mineral analysis, and tourmaline geochemistry were done, and U–Pb detrital zircon geochronology was obtained, in late Palaeozoic sedimentary and meta-sedimentary units from the Floresta and Santander Massifs in the Eastern Colombian Andes in order to constrain their provenance and related it with the magmatic, sedimentary, and deformational record of the Gondwana–Laurentia convergence until the late Carboniferous to Permian formation of Pangea. Late Devonian to early Carboniferous sandstones from the Floresta Massif changed from sublithoarenites to lithoarenites, tracking the progressive uplift and unroofing of sedimentary and metamorphic rocks, with associated volcanic activity. The U–Pb detrital zircon geochronology from the sedimentary and metasedimentary of Floresta and Santander documents Mesoproterozoic and Palaeoproterozoic sources, and younger Ordovician to Silurian age populations, that can be related to the early to middle Palaeozoic plutonic rocks and the Amazon Craton. The limited Silurian to Early Devonian detrital ages that contrast with the more significant Middle to Late Devonian zircons that document the erosion of contemporaneous magmatic sources formed after a late Silurian to Early Devonian reduction on the magmatic activity along the proto-Andean margin. These rocks were apparently deformed and metamorphosed between the late Carboniferous and the early Permian. It is suggested that the filling and deformation record of these rocks documented the changes in plate convergence obliquity at the western margin of Gondwana associated with the migration of Laurentia until its final position in Pangea. Between the late Carboniferous and the early Permian, peri-Gondwanan continental terranes also collided with the continental margin. Over-imposed Mesozoic tectonics have contributed to the final redistribution of these terranes to their current position.Abbreviations:LA: laser ablation inductively couple mass spectrometer; CL: cathodoluminiscence

Depositional Features in Tourist Beaches of Chennai Metropolis, SE Coast of India: Inferences from Grain Size Studies

Abstract: The present study was undertaken to examine the depositional and transportation pattern in the tourist beaches of Chennai in SE coast of India. Twenty four samples were analyzed for textural parameters, Linear discriminate function (LDF), C-M plots and heavy/light minerals from beach, berm and dune regions. Results of textural parameters indicate that they are coarse grained in the three regions. Majority of the samples indicate that they are moderately well sorted, symmetrically skewed and leptokurtic. The LDF analysis allowed in identifying areas that are characterized by: (1) beach, (2) shallow agitated environment and (3) fluvial deposits. C-M plots indicate that the sediments in the beaches were deposited from the near shore environment. Heavy mineral analysis suggests that the heavy and light minerals were in the range of 0.5 to 16.9% and 82.08 to 98.14% and the light/dark layers are controlled by the prevailing tidal conditions in the coastal region. It is observed that sand is accumulating from the shallow agitated environment, while the transportation and deposition of sediments is mainly due to the interaction of tidal activities at the same time. C-M plots suggest that the sediments fall in the graded suspension and the saltation activities in the region also facilitate to understand the hydrodynamics of the region suggesting that they are deposited by high-energy activities.

Sedimentological Study and Heavy Mineral Analysis of Sediment Samples from Well-S, Niger Delta, Nigeria

Sedimentological study and petrographic analyses were carried out on thirty ditch cutting samples from well-S, Niger Delta, Nigeria, with the aim of determining the provenance and depositional environment of the sediments. The samples were subjected to soxhlet extraction for the removal of soluble organic matter from them and particle size analyses using Pipette and Emery sedimentation techniques in order to determine the grain size distribution of the sediments. Separation of heavy of mineral from the samples was done with the aid of bromoform to enable petrographic analyses of the heavy mineral suite, under the polarising microscope. The data obtained from the grain size analysis were used in preparing histograms, from which some simple statistical parameters were derived. Graphic mean values obtained range between 0.74 and 2.64 O, which implies that the sediments are predominantly fine-medium grained. The inclusive standard deviation values ranges from 0.53 to 1.24 O, indicating that the sediments are moderately well sorted to moderately sorted. Inclusive graphic skewness values of 0.29 to 0.70 indicate that the sediments ranges from finely skewed to strongly finely skewed and the graphic kurtosis values of 0.61 to 1.54 shows that the sediments are predominately very platykurtic which implies a low energy environment of deposition. The polymodal nature displayed by the histograms indicates that the sediments have been derived from various sources. The study concluded that the sediments were deposited in a fluvial environment. It also established that the sediments originate from metamorphic and acid igneous rocks of the Nigeria Basement Complex and mineralogically mature to sub-mature.

The early Paleozoic sedimentary–tectonic evolution of the circum-Mangar areas, Tarim block, NW China: Constraints from integrated detrital records

The Mangar depression, located in the eastern part of the Tarim basin, had deposited extremely-thick lower Paleozoic sediments, which yields great scientific value and hydrocarbon resource potential. Due to the lack of enough outcrop and core studies, many issues, e.g., early Paleozoic geographical evolution, basin nature and tectonic affinity, are still poorly understood. In this study, we selected circum-Mangar areas (i.e., the South Quruqtagh, Tabei and Tazhong areas), and carried out comprehensive detrital provenance analysis including detrital modal analysis, heavy mineral and trace element analysis, and detrital zircon U–Pb dating on the Middle–Upper Ordovician and Silurian sandstones. The results show that Upper Ordovician–Lower Silurian detrital provenances of the South Quruqtagh and Tabei areas were primarily derived from the intracontinental uplifts in Tarim. Meanwhile, Upper Silurian detrital provenances of the above two areas were mainly derived from the mix of intracontinental uplifts and continental-margin arcs. Dramatic Late Silurian provenance-change suggests the evident tectonic transition of the northern Tarim margin, which is the opening of the South Tianshan back-arc oceanic basin. Combining the previous studies, an integral redefinition model for the Mangar depression has been made. The evolution process of the Mangar depression could be divided into four stages: graben stage (late Neoproterozoic), transitional stage (Cambrian to Middle Ordovician), downwarp stage (Late Ordovician to Early Silurian) and extinction stage (Late Silurian). Hence, the Mangar depression evolved as an aulacogen. Significantly, the evolutional scenario of the Mangar aulacogen was consistent with that of the North Altyn Tagh and the North Qilian, suggesting that the Mangar aulacogen was involved mainly in the Proto-Tethys tectonic realm south to the Tarim block. However, the Late Silurian tectonic activity in the northern Tarim margin did produce massive detrital sources for northern part of the Mangar aulacogen and aggravated the extinction process of the Mangar aulacogen.

Late Pleistocene river migrations in response to thrust belt advance and sediment-flux steering — The Kura River (southern Caucasus)

One reaction of rivers toward allogenic triggers is the large-scale river channel migration in the form of avulsions or progressive lateral migrations (combing) that are widespread phenomena around the world during the late Quaternary. Because they potentially cause significant human and economic losses and significantly change geomorphic processes in the affected regions, a deeper knowledge about causes and rates is essential and furthermore helps to identify the dominant drivers of regional landscape evolution during different periods. One possible cause for river channel migrations is sediment-flux steering, i.e. the shift of rivers in sedimentary basins against a tectonically driven trend caused by transverse sediment discharge. During the last 30years, sediment-flux steering has been investigated by field and experimental studies in extensional half-grabens with generally small-sized transverse catchments and/or volcaniclastic sedimentation.This study presents geomorphologic, geochronologic, and heavy mineral analyses together with complementary tectonomorphometric and earthquake data to investigate late Quaternary channel migrations of the Kura River in the southern foreland basin of the Greater Caucasus, a region where the late Quaternary landscape evolution is rather fragmentarily understood so far. Special emphasis of this study is given to the interplay between axial river flow and transverse sediment supply leading to sediment-flux steering. Large-scale migrations of the course of the Kura River during the late Quaternary reflect the interplay between tectonic processes leading to the southwestward advance of the Kura Fold-and-Thrust-Belt and climatically-triggered sediment-flux steering caused by aggradation phases of transverse rivers with comparatively large catchment areas in the Lesser Caucasus. During generally warmer periods such as the Holocene with fluvial incision and low sediment supply from the transverse rivers, the main Kura River could follow its tectonically driven trend toward the southwest. In contrast, during generally colder periods such as the upper late Pleistocene, sediment-flux steering caused by aggradation of the transverse rivers forced the main Kura River to migrate >10km against that tectonically induced trend toward the northeast. Apart from giving information about the main drivers of the late Quaternary landscape evolution in this part of the southern Caucasus region, this study also helps to understand the cause of a permanent threat of settlements and the loss of fertile agricultural land in the intensively labored Marneuli Depression of southern Georgia.

Detrital zircon and provenance analysis of Late Cretaceous–Miocene onshore Iranian Makran strata: Implications for the tectonic setting

A multidisciplinary provenance study, including sandstone framework, heavy mineral analysis, in situ U-Pb dating of detrital zircon, and Hf isotopic ratio analysis of dated zircons, was undertaken on Late Cretaceous−Miocene deep-marine turbiditic and deltaic sandstones of Makran accretionary wedge, SE Iran, to determine their sedimentary provenance and tectonic setting. Sandstone framework modes reveal both magmatic arc rocks as a source of Late Cretaceous−Oligocene detritus and recycling of Miocene sandstones. Heavy mineral assemblages, Cr-spinel, and blue amphibole indicate ophiolite and high-pressure−low-temperature metamorphic rocks (blueschists) as a supplementary provenance. In total, 2931 laser-ablation−inductively coupled plasma−mass spectrometry (ICP-MS) U-Pb detrital zircon ages on 21 sandstone samples yielded three major age peaks at ca. 167 Ma, 88.7 Ma, and 48.9 Ma. Also, 241 in situ Hf isotope analyses of dated zircons provide evidence for dominantly igneous source rocks. Two main detrital zircon ages are identified: (1) abundant Middle Jurassic grains with Hf isotopic compositions of continental crust, suggesting a rifting-related magmatic provenance; and (2) Late Cretaceous−Eocene grains with Hf isotopic compositions of continental crust and nondepleted mantle, suggesting a continental magmatic arc provenance. This change in provenance is attributed to the Late Cretaceous convergence between Arabia and Eurasia.

Yerdi sand dunes (Erfoud area, southeastern of Morocco): color, composition, sand’s provenance, and transport pathways

This study aims to prove sand dunes’ color difference across Ziz riversides at Yerdi and then to investigate sand’s origin and transport pathways. We have opted for remote sensing and Geographic Information System tools as a methodology, in addition to laboratory analyses, that included mineralogy, grain size, and shape investigation of samples collected from studied dunes. The results reveal the following: (i) variation in grain size and shape of the studied sand. A high concentration of quartz and a low amount of carbonates and iron oxide were recorded in the studied dunes. Heavy mineral analyses have shown a similar mineralogical concentration in both samples, yet sand in the left side appears to be richer in hematite and goethite than the right one. (ii) Band ratios 6:4 and 5:7 of Landsat TM allowed the mineralogical distinction of mafic minerals, carbonates, and quartz, while Landsat 3:1 band ratio and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) 2:1 band ratio were the most suitable for iron oxide distinction. The results confirm the dominance of quartz in both sides. However, iron oxide III (Fe3+) concentration is much important in the left side, which explains the difference in sand color. (iii) The studied dunes are potentially supplied from Quaternary, Cretaceous, and Paleozoic formations. The abundance of ferruginous conglomerate among potential formations supplying dunes and the abundance of hematite and goethite in sand from the left bank more than the right explain the red color marking these dunes. While, dunes’ morphodynamic explains the pal color observed in dunes located in the right bank.

Triassic to Early Jurassic climatic trends recorded in the Jameson Land Basin, East Greenland: clay mineralogy, petrography and heavy mineralogy

AbstractDuring the Early Triassic the Jameson Land Basin (Central East Greenland) was located around 30° N, in the Northern arid belt, but by the Early Jurassic was positioned at a latitude of approximately 50° N. This study examines the record of this transition through a largely continental succession using clay mineralogy, sedimentology, petrography and heavy mineralogy. The Jameson Land Basin is aligned north–south and is 280 km long and 80 km wide. Following an Early Triassic marine phase the basin was filled by predominantly continental sediments. The Early‐to‐Late Triassic succession comprises coarse alluvial clastics (Pingo Dal Formation) overlain by a succession of fine‐grained evaporite‐rich playa/lacustrine sediments (Gipsdalen Formation), indicative of arid climatic conditions. The overlying buff, dolomitic and then red lacustrine mudstones with subordinate sandstones (Fleming Fjord Formation) record reduced aridity. The uppermost Triassic grades into dark organic‐rich, and in places coaly, mudstones and buff coarse‐grained sandstones of lacustrine origin that belong to the Kap Stewart Group, which spans the Triassic–Jurassic boundary, and appear to record more humid climatic conditions. Clay mineralogy analyses highlight significant variations in the kaolinite/illite ratio, from both mudstone and sandstone samples, through the Triassic and into the earliest Jurassic. Complementary heavy mineral analyses demonstrate that the variations recognised in clay mineralogy and sandstone maturity through the Triassic–Early Jurassic succession are not a product of major provenance change or the effect of significant diagenetic alteration. The observed variations are consistent with sedimentological evidence for a long‐term trend towards more humid conditions through the Late Triassic to Early Jurassic, and the suggestion of a significant pluvial episode in the mid‐Carnian.

A comparison of heavy mineral assemblage between the loess and the Red Clay sequences on the Chinese Loess Plateau

Abstract QEMSCAN-based (Quantitative Evaluation of Minerals by Scanning Electron Microscopy) heavy mineral analysis has recently been demonstrated an efficient way to allow a rapid extraction of provenance information from sediments. However, one key issue to correctly obtain a provenance signal using this technique is to clearly separate effects of diagenetic alteration on heavy minerals in sediments, especially in fine-grained loess. Here we compare heavy mineral assemblages of bottom Quaternary loess (L33) and upper Pliocene Red Clay of three sites on the Chinese Loess Plateau (CLP). Two sites (Chaona and Luochuan) with similar modern climate conditions show similar heavy mineral assemblages but contain much less of the unstable heavy mineral amphibole than the drier Xifeng site. This result provides strong evidence supporting that climate-caused diagenesis is an important factor controlling heavy mineral assemblages of fine-grained loess. However, heavy mineral assemblages are similar for loess and paleosol layers deposited after 0.5 Ma on the Chinese Loess Plateau regardless of climate differences, suggesting that time is also a factor controlling heavy mineral assemblages of loess and Red Clay. Our high resolution sampling of the upper Miocene-Pliocene Chaona Red Clay sequence reveals similar heavy mineral compositions with a minor amphibole content, different from the drier Xifeng site results of the same age. This result indicates that the monsoonal climate pattern might have been maintained since the late Miocene. Furthermore, it indicates that the heavy mineral method is promising in tracing provenance for sites northwest of the Xifeng site on the Loess Plateau.

Erosion patterns in the Changjiang (Yangtze River) catchment revealed by bulk-sample versus single-mineral provenance budgets

The Changjiang, the fourth longest river on Earth and the largest in Eurasia, has a complex sediment-routing system presently interrupted by the Three Gorges Dam, the world's largest hydroelectric engineering project. To study sediment-generation processes in the huge catchment and compare the different erosion patterns obtained by different methodological approaches, high-resolution petrographic and heavy-mineral analyses were performed on sands from the trunk river and its major tributaries. The frequency distributions of diverse groups of detrital amphiboles were also investigated. Rigorous statistical methods were used to define end-members, evaluate mineralogical variability, assess similarities among samples, and eventually calculate the relative contributions from each major tributary to the trunk river by forward end-member modelling of integrated compositional data. The litho-quartzose sand with few heavy minerals generated in Tibetan headwaters evolves downstream to feldspatho-litho-quartzose with medium-rank metamorphic rock fragments and moderately rich amphibole-epidote suites. Sand across the Sichuan basin and as far as the Three Gorges Dam is enriched in mafic volcanic, clinopyroxene, and carbonate grains eroded from Permian basalts and Paleozoic strata of the South China Block. The final (Yangtze) tract is characterized by litho-feldspatho-quartzose sand with moderately poor, amphibole-dominated suites with epidote, clinopyroxene, and garnet. The orogenic compositional signature acquired in the upper part of the basin is thus carried all the way to the Chinese passive margin, as observed also for the Yellow River in the north. Even after long-distance transport across wide continental areas, detrital modes thus reveal the tectonic character of the source rather than the geodynamic environment of the sink.Quantitative provenance analysis indicates that left-bank tributaries draining the Longmen and Qinlin mountains supply most of the sand reaching the East China Sea. Contributions from Tibetan headwaters are negligible, as those from right-bank tributaries in the middle-lower part of the basin. Sediment budgets and erosion patterns inferred from our integrated petrographic and heavy-mineral data set contrast with those based on detrital-zircon geochronology but agree with stream-profile analysis, revealing close correspondence with slope steepness, precipitation, stream power, tectonic activity, and frequency of major earthquakes. Sediment budgets based on amphibole groups are poorly constrained. We conclude that provenance budgets based on single-mineral species are typically unrobust, particularly because they suffer from inaccurate estimates of mineral concentration in the end-member sources. Exploring in detail a millesimal part of the sediment (typically 1/5000 in the case of zircon) is a risky strategy that may return a distorted picture of reality.

Heavy mineral analysis to identify sediment provenance in the Dan River drainage, China

Identifying the provenance of sediments carried by modern rivers can provide information on earth surface processes and help us to interpret geological history more clearly. The types and distribution patterns of surface sediments deposited in river systems are determined mainly by the fluvial flux and weathering of the proximal source rocks. In this paper, analysis of the heavy mineral content of 99 surface sediment samples was used to identify the source of the sediments carried by the Dan River in China. The objectives of this study are to: (1) determine the characteristics and distribution of the sediments, and (2) identify and classify the various depositional areas according to their differing source areas. The Dan River is divided into the lower, middle, and upper reaches to investigate the spatial distribution of heavy minerals. The main minerals detected were amphiboles, pyroxene, epidote, garnet, tourmaline, zircon, apatite, rutile, sphene, anatase, pyrite, and ilmenite. Generally, ilmenite (0.7% to 69.1%), amphibole (0% to 93.6%), epidote (0% to 53.3%), garnet (0% to 36.7%) and pyroxene (0% to 42.0%) were the most frequent detrital heavy minerals in the studied river sections. The Dan River and its tributaries are characterized with respect to their heavy mineral assemblages and heavy mineral indexes. Six depositional areas are distinguished and classified as Depositional area A (the Laoguan, Qi, and Xian rivers), Depositional area B (the Qingyou and Wuguan rivers), Depositional area C (the Laojun River), Depositional area D (the upper reaches of the Dan River), Depositional area E (the Yinhua River), and Depositional area F (the Tao River). The provenance study indicated that the sediments were derived mainly from the proximal exposed rocks. Sediments in the middle reaches of the Dan River were derived from Depositional areas B, C, and E, whereas sediments in the lower reaches were derived mainly from the local rocks along the river. Similar heavy mineral assemblages were obtained from Danjiangkou Reservoir and Depositional area A, especially for the Laoguan River, indicating the significant influence of Depositional area A on the reservoir.