Provenance Discrimination Diagrams Research Articles

Mineralogy and Major Element Geochemistry of the Oligocene Barail Group Sandstones from the Sylhet Trough, Bengal Basin: Provenance and Tectonic Implications

The origin of Oligocene sediments in the Bengal Basin and associated tectonic setting remain poorly understood. This study investigates the framework mineralogy and major element geochemistry of the Barail Group sandstones from the Sylhet Trough within the Bengal Basin to clarify the provenance and tectonic history of the Oligocene. Modal analysis (Q83F7L10) and geochemical data support a classification of sublitharenite to subarkose, some with Fe enrichment. The heavy mineral assemblage is dominated by opaque minerals, followed by ultrastable minerals with zircon > tourmaline > rutile. The sub-angular to sub-rounded sand grains with a compositionally moderate mature nature suggest that the sediments were deposited close to the source area. The mineralogical and geochemical provenance discrimination diagram suggests contributions from felsic igneous, sedimentary/metasedimentary, and low-grade metamorphic sources, with detritus derived from the Indian craton and proto-Himalaya region. Data suggest moderate to intense chemical weathering, indicative of low relief and a sub-humid to humid climate in the source area. The tectonic analyses indicate that the Bengal Basin transitioned from a predominantly passive margin to an active tectonic margin setting during the Oligocene.

Provenance of sediments and environmental risk assessment of heavy metals in the “Mis Amores” beach, Veracruz, Gulf of Mexico, Mexico

In this study, grain-size, mineralogy, and geochemistry of Mis Amores (MA) beach sediments, Tuxpan, Veracruz State, Gulf of Mexico are analyzed. The textural parameters reveal that the sediments are fine-grained and vary from well-sorted to very well-sorted nature. The SEM-EDS analysis reveal that the sediments are abundant in minerals such as quartz, alkali feldspars, zircon, ilmenite, and pyroxene. Geochemically, the sediments are classified as sub-arkose type. The Chondrite normalized rare earth elements (REE) pattern suggest that the source area is dominated by felsic and intermediate igneous rocks (Eu/Eu* = 0.90 - 1.19, number of samples n = 16). The provenance discrimination diagrams indicated that the MA sediments were derived by the weathering of felsic igneous rocks, probably from the Trans Mexican Volcanic Belt. The results of this study reveal that the Tuxpan River played an important role in delivering sediments to the MA beach area. The environmental indices suggest that the sediments are moderately contaminated by Zn and moderate to extremely contaminated by Cu and As. The Cu (> 84%) and Zn (> 82%) concentrations are predominantly associated with the exchangeable fraction, which are readily bioavailable. Cu, As, and Zn in the MA sediments were derived from the agricultural activities and waste water discharges from the sanitary network of the Tuxpan town and port.

Geochemistry and mineralogy of beach sediments in the northern Gulf of Mexico, Tamaulipas state, Mexico: implication for provenance

Geochemical and mineralogical studies were performed in the La Pesca (LP) and Tesoro Altamira (TA) beach sediments, located in the Tamaulipas state, northern Gulf of Mexico. The main aim of this study is to infer the weathering history and provenance and to discriminate the tectonic environment of the beach sediments. The sediments are composed of quartz with small amounts of accessory minerals such as plagioclase, calcite, orthoclase, microcline, and zircon. Both beach sediments are classified as fine-grained and very well sorted, however LP has coarse skewed and leptokurtic sediments, whereas TA has fine-skewed and very leptokurtic sediments. The chemical index of weathering (CIW’) indicates intense weathering in the source area. The quartz grain microtextures in the LP and TA are classified into mechanical, chemical, and mechanical/chemical origin. Mechanical features such as fractures, pits, percussion marks, abrasion fatigue, and V-shaped marks favor high-energy littoral, fluvial, subaqueous-marine, and aeolian environments. The chemical features indicate solution pits and crystalline overgrowth, which suggests a silica saturated marine environment. The mechanical/chemical features display adhering particles and elongated depressions suggest formation in a sub-aqueous nearshore marine environment. Major and trace elements-based provenance discrimination diagrams indicate a felsic source derived from the Mesa Central (MC), Sierra Madre Oriental (SMOr) and Oaxaquia terranes. The major and trace element concentrations imply a passive margin setting for the northern Gulf of Mexico, which is consistent with the general geology.

Geochemical compositions and provenance of Late Holocene core sediments from Mullipallam Creek, southeast coast of India

Geochemical analyses of major oxides (SiO2, Al2O3, Fe2O3, Na2O, K2O, CaO, MgO, P2O5 and TiO2) were carried out on the Late Holocene core sediments in the Mullipallam Creek, Southeast coast of India to infer their texture, sediment classification and provenance for paleoweathering conditions. Based on their major oxides compositions, the sediments were classified as Fe-Shale. Bivariate plots of grain size parameters (mean against sorting) are distinguished between open and closed-basin conditions. Chemical Index of Alteration (C1-70.21; C2-69.02), Chemical Index of Weathering (C1-75.25; C2-74.68), Plagioclase Index of Alteration (C1-73.32; C2-72.44) indices and A-CN-K plot suggests moderate chemical weathering in the source area, which was favoured and accelerated under the existing humid conditions of the tropical climate. Al2O3 /TiO2 ratio also proposes the intermediate to felsic source rocks and some of the sediments are derived from mafics. The provenance discrimination diagram explains that the plots appeared in mafic provenance fields indicating that they are derived from different environments.

Provenance, Tectonic Setting and Paleoclimate of the Bhuban Formation Exposed in Jampui Hills, Tripura Fold Belt, Tripura, India: Insights from Petrography and Clay Mineralogy

Abstract The sandstones of the Bhuban Formation (Miocene) exposed in the Jampui hills of Tripura Fold Belt, India has been studied for provenance, tectonic setting and paleoclimate using the petrography, heavy mineral assemblage and clay mineral studies. The detrital mode of the sandstones indicate that the sediments consists predominantly of detrital quartz (avg. 92.19%), with subordinate proportions of feldspar (avg. 4.55%) and rock fragments (avg. 3.25%). The provenance discrimination diagrams depict the derivation of the detritus from both plutonic and metamorphic source rocks having affinity to continental block provenance. The plots of QFR and semi quantitative weathering index of the clastics support a moderate degree of paleoweathering in the source area under humid climatic condition. The presence of zircon, tourmaline, rutile, kyanite, epidote, sillimanite and garnet in the Bhuban sandstones is ascribed to the provenance of plutonic and metamorphic rocks. Dominance of zircon in the heavy mineral assemblage and the ZTR index values (75.13% avg.) indicate towards moderate degree of maturity with long distance of transport. The study of the shale samples by XRD and SEM analyses shows the dominance of illite over kaolinite and montmorillonite. The presence of minor amount of montmorillonite may suggest the addition of tuff and volcanic ash in the sediments under alkaline environment.

Geochemical and paleoenvironmental characteristics of upper Neoproterozoic ore-hosting black shales in the Bafq metallogenic zone, Central Iran

The black shales of the Koushk series in the Bafq metallogenic zone, which are part of the upper Neoproterozoic shales of Central Iran, are typically comparable with the Proterozoic Shale signature but comprehensive information about formational conditions and geochemical characteristics is scarce. In this study, the chemical composition, provenance, tectonic setting, climatic conditions during the weathering of source rocks and paleoredox depositional environments for Koushk shales are investigated. Compared with ‘Post Archean Average Shale’, the samples are depleted in Fe2O3, MgO, TiO2, K2O, Na2O, Sc, Co, Th, V and Cr, owing to the chemical composition and degree of weathering of the source rocks. The provenance study implies that the sediments originated from felsic igneous rocks with a moderate degree of weathering in a semiarid to arid climate. The ratios of redox-sensitive elements [e.g. V/Cr, V/(V + Ni)] revealed that the studied black shales were deposited under moderately anoxic conditions. Furthermore, trace-element ratios (e.g. La–Th–Sc) suggest a continental arc setting for the provenance, which is consistent with the tectonic evolutionary history of Central Iran throughout the late Neoproterozoic. KEY POINTS Neoproterozoic black shales of the Koushk series in the Bafq metallogenic zone host a Zn–Pb SEDEX deposit with 13 Mt, averaging 7 wt% Zn and 3 wt%. The provenance discrimination diagram of the black shales suggests their derivation from felsic source rocks. The black shales were deposited under a moderately anoxic environment. Trace-element ratios reveal a continental arc setting for the source rocks.

Provenance, source weathering, and tectonic setting of the lower Cambrian Shuijingtuo Formation in the Middle Yangtze area, China

The organic-rich shale of the Lower Cambrian Shuijingtuo Formation is an important hydrocarbon source rock in South China. The geochemical characteristics of this shale were investigated to determine the provenance, weathering conditions, sedimentary recycling, paleoclimate, and tectonic setting of the Shuijingtuo Formation in Yichang in the Middle Yangtze area. The shale is relatively enriched in CaO, P2O5, Mo, U, V, Cd, and Cu. The rare earth element (REE) patterns of the shale exhibit light rare earth element (LREE) enrichment and heavy rare earth element (HREE) depletion. It has weak negative Eu and Ce anomalies, which are similar to the characteristics of passive margin deposition. The analysis of the carbonate dilution effect conducted in this study reveals that carbonate dilution has a greater effect on the MgO, Ba, Sc, and Zr contents. The provenance discrimination diagrams suggest that the shale is primarily derived from a mixture of intermediate and felsic igneous source rocks, which were similar to Tonalite-trondhjemite-granodiorites (TTGs) in composition. The chemical index of alteration (CIA) values and the A–CN–K ternary diagram indicate that the source area of the shale experienced a low degree of chemical weathering under a cold and arid climate in the early period and a moderate degree of chemical weathering under a warm and humid climate in the later period. The relationship between Zr/Sc and Th/Sc indicates that the shale was deposited by the first cycle of sedimentation rather than via reworking. The discriminant function diagrams, major element ratios, immobile trace element ratios, and ternary relationships between La, Th, Sc, Zr, and Co indicate that the source rocks were deposited in a passive margin tectonic setting. It is suggested that the Ezhong old land, which is predominantly composed of the Huangling granite and the Kongling complex (composed of intermediate and felsic igneous rocks) was the source area.

Composition, weathering, and provenance of beach sands adjacent to volcanic rocks in the northern Gulf of Guinea, SW Cameroon

The southern coastal portion of the Tertiary Cameroon Volcanic Line (CVL), in the Gulf of Guinea, is bordered by Pan-African granitoids, metamorphic rocks, and Cretaceous sedimentary successions, which are prone to contribute sediments to the nearby Limbe beach. To better constrain the weathering intensity and provenance of the beach sediments, the mineralogy and chemical composition of these sediments were analyzed. The low values of SiO2/Al2O3 ratios and Zircon-Tourmaline-Rutile (ZTR) index, coupled with high Index of Compositional Variability (ICV) indicate compositionally immature sediments. This is further supported by the presence of rock forming minerals such as olivine, pyroxene, and amphibole. The Th/Sc versus Zr/Sc binary and Al2O3–TiO2–Zr ternary diagrams suggest that the studied sediments have not experienced recycling. The Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), the A–CN–K and (A-K)-C-N triangular diagrams indicate that the Limbe beach sediments were undergone moderate to intense weathering. Several provenance discrimination diagrams based on Al2O3, TiO2, Zr, TiO2, La/Sc, and Th/Co, and the ternary plot of V–Ni–Th*10, and the comparison of chondrite normalized rare earth elements (REE) patterns of the studied sediments with potential source rocks suggest that the source area is composed of mafic rocks of CVL. This indicates that the granitic, metamorphic, and sedimentary rocks close to the volcanic structure do not significantly contribute to the sedimentation of the studied beach. In addition, the results of this study indicate that longshore currents do not influence the chemical composition of the sediments.

Geochemistry of the mudrocks and sandstones from the Bredasdorp Basin, offshore South Africa: Implications for tectonic provenance and paleoweathering

Abstract An inorganic geochemical investigation of mudrocks and sandstone from the southern Bredasdorp Basin, off the south coast of South Africa was carried out to unravel the provenance, paleoweathering, and tectonic setting of the basin. Seventy-seven representative samples from exploration wells E-AH1, E-AJ1, E-BA1, E-BB1, and E-D3 underwent geochemical analysis involving major and trace elements. The major oxide compositions show that the sandstones could be classified as sub-arkose and sub-lithic arenite. The provenance discrimination diagrams based on major oxide geochemistry revealed that the sandstones are mainly of quartzose sedimentary provenance, while the mudrocks are of quartzose sedimentary and intermediate igneous provenances. The discrimination diagrams indicate that the Bredasdorp sediments were mostly derived from a cratonic interior or recycled orogen. The bivariate plots of TiO2 versus Ni, TiO2 against Zr, and La/Th versus Hf as well as the ternary diagrams of V–Ni–Th∗10 suggest that the mudrocks and sandstones were derived from felsic igneous rocks. The tectonic setting discrimination diagrams support passive-active continental margin setting of the provenance. Also, the closely similar compositions of the analysed samples and recent sedimentary rocks of the East African Rift System perhaps suggest a rifted basin tectonic setting for the Bredasdorp Basin. Chemical index of alteration (CIA) indices observed in the sandstones suggest that their source area underwent low to moderate degree of chemical weathering. However, the mudrocks have high CIA indices suggesting that the source area underwent more intense chemical weathering, possibly due to climatic and/or tectonic variations.

Provenance, source weathering, and tectonics of the Yarlung Zangbo River overbank sediments in Tibetan Plateau, China, using major, trace, and rare earth elements

This paper studies the major, trace, and rare earth elements (REEs) in fluvial sediments from the Yarlung Zangbo River (YZR) on the Tibetan Plateau, China, with the aim of investigating their provenances, sediment maturity, weathering conditions, and tectonic settings. All samples and analytical techniques are based on Environmental Geochemical Monitoring Networks, which are a crucial part of IGCP259/360 (Global Geochemical Baseline). The results show that the YZR sediments consist of greywacke and litharenite with low‐moderate maturities of textures and minerals. The chemical index of alteration (CIA) (49–71), plagioclase index of alteration (49–77), and index of compositional variability (ICV) values (0.82–1.54) indicate that both mature and immature sediments are present in the YZR and have experienced weak to moderate weathering with little intense weathering in the source area, which is also confirmed by the ICV‐CIA, A‐CN‐K, A‐CNK‐FM, and MFW plots. Moreover, the provenance discrimination diagrams suggest that the YZR sediments are predominantly derived from felsic rocks that are close to the upper continental crust and from acid intermediates, and the tectonic settings of the YZR source rocks were associated with active continental margins and continental island arcs. The overall sediment types, weathering conditions, and tectonics of the YZR were consistent with those of the Brahmaputra River and Meghna River during the Himalayan–Tibetan orogeny, while the sediments of the Brahmaputra River are characterized by recycled‐quartzose sources when compared with the other two Himalayan rivers due to the contributions of quartzolithic composition.

Petrography and geochemistry of the Lower Carboniferous Abu Durba sandstones, West Central Sinai, Egypt

Petrographically, the Lower Carboniferous Abu Durba sandstones are classified as quartz arenites reflecting their high maturity and have an average framework composition of Q96F2L2. The sandstones are rich in SiO2, Zr, Sr, and Ba and depleted in most other major and trace elements, compared with the average upper continental crust. The positive correlation between Al2O3 and most trace elements signifies that trace elements are associated with clay minerals rather than with source rocks. Provenance discrimination diagrams, major elemental ratios (Al2O3/TiO2 and K2O/Na2O), and SiO2, Cr, Ni, V, and Zr contents in sandstones reveal that the sandstones are mainly derived from quartzose recycled sedimentary rocks with subordinate felsic plutonic sources. The chemical index of alteration (avg. 88.21) and Rb/Sr ratio (> 0.8) values for the Abu Durba Sandstone indicate an intensive degree of weathering either of the original source or during transport before deposition, and may reflect intense recycling in the source area. Also, low index of compositional variability values and high SiO2/Al2O3 ratios indicate high mineralogical maturity of Abu Durba Sandstone. The discriminant function-based multidimensional diagrams reveal that the Abu Durba Sandstone was deposited in a rift basin, which is consistent with the general geology of West Central Sinai during the Lower Carboniferous. The older sandstones of Naqus (Lower Cambrian) and Abu Thora (Lower Carboniferous) formations in addition to the Precambrian basement rocks are probably the sources of the Abu Durba Sandstone.

Petrography and geochemistry of siliciclastic rocks of the Middle Eocene Gercus Formation, northern Iraq: Implications for provenance and tectonic setting

Red coloured Middle Eocene Gercus Formation is a widely exposed rock unit in northern Iraq, southeastern Turkey, and northwestern Iran. Siliciclastic rocks (mudstones and sandstones) are the predominant rocks of this formation which were studied petrographically and geochemically. The Gercus Formation also contains a few beds of limestone, gypsum, and conglomerate. The sandstones are of two types, red and white, mostly immature litharenites, consisting of lithics (85%), quartz (12%), and feldspars (3%). The rock fragments consist dominantly of angular chert and rounded limestone and smaller amounts of sedimentary, magmatic, volcanic, and metamorphic lithics indicating proximity of their source rocks. The provenance discrimination diagrams of the detrital grain counts in sandstones show recycled and collision orogen sources. Petrographic, heavy minerals and major and immobile trace element (e.g. La, Th, Sc, Zr, Hf, and Ti) discrimination diagrams indicated that the Gercus Formation was originated under a collision tectonic setting above a subduction zone as part of an Oceanic Island Arc (OIA), where its sediments were derived from mixed sources, including recycled sediments of chert‐ and carbonate‐rich formations and igneous‐metamorphic ophiolitic complexes of north to north‐east Iraq and adjacent Iranian and Turkish counterparts. The results also indicated a mixed marine (lacustrine and deltaic) and non‐marine (fluviatile) origin for the Gercus Formation. The red sandstones, white sandstones, and mudstones show minor differences in their major, trace, and rare‐earth element (REE) contents and have generally similar Post Archean Australian Shale (PAAS)‐, Upper Continental Crust (UCC)‐, and CI‐chondrite‐normalized distribution patterns indicating their common origin. The average of elements in the siliciclastic rocks is depleted in the high‐field‐strength elements (HFSE), the large‐ion lithophile elements (LILE), and REE; and enriched in some rock‐forming elements (RFE) and mantle rock‐forming elements (MRFE) (Mg, Ca, Cr, Co, Ni) and depleted in others (Si, Al, Fe, Cu, Zn, Ga) relative to PAAS and UCC; whereas, they are depleted in Fe, Mn, Mg, Co, Ni, Cu, Zn, Ga, Na, and P, and enriched in all other RFE, MRFE, LILE, HFSE, and REE compared to CI‐Chondrite. The REE content of these rocks is very low (23–34 ppm) and their LREEs are enriched six times relative to HREEs. These geochemical characteristics suggest a provenance dominated by basic/ultrabasic rocks. The U/Th, V/Cr ratios and the authigenic U values show an oxic depositional environment for the studied siliciclastic rocks.

Petrography, geochemistry, and provenance of Jurassic sandstones from the Sakarya Zone, NW Turkey

The Jurassic sandstones exposed in the western part of the Sakarya Zone are yellowish to brown, moderate to well sorted, medium to coarse-grained, grain-supported, and cemented by calcareous and minor silica. Sandstones are mainly classified as litharenite, subarkose, and arkose according to the relative proportions of quartz, feldspar and rock fragments, and major element ratios. On the SiO2 variation diagram, Na2O and K2O show slight positive correlations, which could reflect abundance of sodic plagioclase and K-feldspar with quartz within high Si-content sandstones. Sandstones generally exhibit slight LREE enrichment with respect to HREEs. The REE plots are characteristic for sedimentary rocks derived from the upper continental crust. Combining the results of several provenance discrimination diagrams, elemental ratios (Th/Sc, Zr/Sc, La/Th), and REE contents in sandstones, they reveal that the sandstones originated from intermediate to felsic source rocks. Accordingly, the probable source of the Jurassic sandstones is the crystalline basement of the Sakarya Zone consisting of Devonian, Carboniferous, and Permian granitoids, and high-grade metamorphic basement rocks. The Jurassic sandstones mostly have characteristic features of passive continental margin basins. It can be noted that the sandstones may have been deposited in a marginal basin that began to open in Early Jurassic time. CIA and CIW values for the Jurassic sandstones suggest that the source area was subject to low to moderate chemical weathering under semihumid to semiarid climatic conditions.

Provenance of upper Paleozoic siliciclastics rocks from two high-latitude glacially influenced intervals in Bolivia

The Toregua Formation in northern Bolivia comprises a continuous succession of sedimentary rocks containing two glacial intervals related to the onset of the Late Paleozoic Ice Age (LPIA). The provenance and depositional tectonic setting of the Upper Devonian–Mississippian (lower) and Pennsylvanian (upper) glacial intervals are separated by non-glacial deposits observed in the Manuripi X-1 and Pando X-1 drill cores, from which petrography, geochemistry, detrital zircon UPb and monazite ThU-total Pb dating are described. Zircon age spectra of sandstone clasts and diamictite indicate an upward change in provenance. Zircon age data from the lower glacial interval yielded age groups at 700–500 Ma, 1300–900 Ma and 2200–1820 Ma, while the monazite gave ages in the range of 600-500 Ma. These age populations correspond to the Guaporé Shield and/or the Arequipa Massif. Detrital zircon from the upper glacial interval has a significant age population at 330–300 Ma that reflects prominent input from the Eastern Cordillera. The maximum depositional age of the upper glacial interval was constrained to ca. 308 Ma. Provenance discrimination diagrams, based on major element geochemistry and trace element ratios, suggest that the glacial and non-glacial sediments were mainly sourced from felsic source rocks. The moderate to high chemical index of alteration (CIA <81) and mineralogical index of alteration (MIA = 81–90 values), abundance of siderite clasts and dominance of kaolinite and abraded zircon grains (without correlation between age and zircon roundness) indicate that the lower glacier incorporated material from older sedimentary covers. In the upper glacial interval, the lower CIA (70) and MIA (71) values and the abundance of plagioclase and detrital zircon grains with preserved euhedral shape <400 Ma suggest that local volcanic rocks in addition to sedimentary covers were eroded.

Compositional variations, chemical weathering, and provenance of sands from the Cox’s Bazar and Kuakata beach areas, Bangladesh

The modal and chemical composition of sands from Cox’s Bazar beach (CBB) and Kuakata beach (KB) areas of Bangladesh has been investigated to infer their maturity, chemical weathering, and provenance signatures. The CBB and KB sands are typically high quartz, low feldspar, and lithic fragments, representing a recycled orogen source. Major element compositions of CBB sands are characterized by high SiO2 (83.52–89.84 wt%) and low Al2O3 (4.39–6.39 wt%), whereas KB sands contained relatively low SiO2 (63.28–79.14 wt%) and high Al2O3 (9.00–11.33 wt%) contents. The major, trace and rare earth element (REE) compositions of beach sands display comparable distribution patterns with enriched Th and SiO2 for both sands relative to upper continental crust (UCC). Pb, Rb, Y, and Fe for KB sands are little higher than UCC and the rest of the elements are marked depleted for both suites reflecting destruction of plagioclase and K-feldspar during fluvial transportation. The CBB and KB sands are compositionally low mature to immature in nature subsequently classified as subarkose and litharenite, respectively. Chondrite-normalized REE patterns for CBB and KB sands show LREE enrichment and nearly flat HREE (LaN/YbN, 7.64–9.38 and 5.48–8.82, respectively) coupled with prominent Eu anomalies (Eu/Eu*, 0.51–0.72 and 0.52–0.76, respectively), suggesting felsic source provenance. The provenance discrimination diagrams, immobile trace element ratios (Th/Sc, Zr/Sc, Ce/Sc, and Ti/Zr), and REE (∑LREE/HREE, Eu/Eu* and GdN/YbN) parameters indicate that CBB and KB sands were largely derived from felsic source rocks, with compositions close to average rhyolite, granodiorite, granite, and UCC.

Geochemical Signatures of Karlad Lake Sediments, North Kerala: Source Area Weathering and Provenance

ABSTRACT In the present study, the lake floor sediments of the Karlad lake, located at higher elevation in Wayanad region of north Kerala, were analyzed for textural characteristics, organic matter, calcium carbonate, major oxides and trace elements. This study was carried out to infer the chemical composition, provenance and intensity of chemical weathering of the source rocks in the lake catchment area. Textural studies signify that lake floor sediments are predominantly as clays (38.75%) followed by sand (36.36%) and silt (25.19%) fractions. The C/N ratio of the lake sediments signify that the sediments are both autochthonous and allochthonous in origin. The major oxides average content reveals the order of abundance as follows; SiO2 &amp;gt; Al2O3 &amp;gt; Fe2O3 &amp;gt; TiO2 &amp;gt; MgO &amp;gt; CaO &amp;gt; K2O &amp;gt; P2O5 &amp;gt; Na2O &amp;gt; MnO. Moreover, the various weathering indices such as Chemical Index of Alteration (CIA-Avg. 93.5%), PlagioclaseIndex of Alteration (PIA-Avg. 95.6%) and Chemical Index of Weathering (CIW-Avg. 95.76%) suggest an intense chemical weathering of the source area. The A-CN-K diagram is also corroborating the same. Various provenance discrimination diagrams reveal that the sediments are derived from the mafic source rocks.

Geochemistry and weathering history of the Balfour sandstone formation, Karoo basin, South Africa: Insight to provenance and tectonic setting

Geochemical analysis on sandstones from clastic sediments was carried out to understand the tectonic setting and subsequent post-depositional change in the Karoo basinal fill of the fluvial deposits of the Balfour Formation during the Late Permian to Early Triassic period. The major and trace element analysis reveal a relatively homogeneous provenance for the sandstones. The geochemical analysis shows that these rocks are first order mature sediments, derived from igneous and/or meta-igneous rocks of a felsic composition. The results show that the sandstone consists of SiO2 (71.58 wt. %), followed by Al2O3 (14.48 wt. %), but with low contents of Fe2O3+MgO (4.09 wt. %) and TiO2 (0.47 wt. %). These sandstones are classified as litharenites and arkoses based on the elements constituent ratio of various schemed adopted. The sandstone in the provenance discrimination diagram plots in the dissected and transitional arc fields suggesting an active margin and continental island arc provenance, preserving the signature of a recycled provenance. The Chemical Index of Alteration (CIA) ranging from 63.56 to 67.10% suggests recycling processes, and that the source area has undergone a moderate degree of chemical weathering. The geochemical characteristics of the sediment suggest the source area of uplifted terrane of folded and faulted strata with detritus of sedimentary and metasedimentary origin.

Provenance, weathering, and paleoenvironment of the Upper Cretaceous Duwi black shales, Aswan Governorate, Egypt

The mineralogy and geochemistry of the Upper Cretaceous Duwi black shales of Nile Valley district, Aswan Governorate, Egypt, have been investigated to identify the source rock characteristics, paleoweathering, and paleoenvironment of the source area. The Duwi Formation consists mainly of phosphorite and black shales and is subdivided into three members. The lower and upper members composed mainly of phosphorite beds intercalated with thin lenses of gray shales, while the middle member is mainly composed of gray shale, cracked, and filled with gypsum. Mineralogically, the Duwi black shales consist mainly of smectite and kaolinite. The non-clay minerals are dominated by quartz, calcite, phosphate, dolomite, feldspar, with little gypsum, anhydrite, iron oxides, and pyrite. Based on the CIA, PIA, and CIW values (average = 84, 94, 95, respectively), it can be concluded that the litho-components of the studied shales were subjected to intense chemical weathering and reflect warm/humid climatic conditions in the depositional basin. The provenance discrimination diagram indicates that the nature of the source rocks probably was mainly intermediate and mafic igneous sources with subordinate recycled sedimentary rocks (Nubia Formation). Geochemical characteristics indicate that the Duwi black shales in Nile Valley district were deposited under anoxic reducing marine environments.

Provenance of aeolian sands in the Hetao Plain, northwestern China

Abstract Patches of aeolian sand are distributed throughout the Hetao Plain, which pose threats to farming and agriculture. Identification of the provenance of the aeolian sands may help with efforts to alleviate ecological stress in Inner Mongolia and in the paleoenvironmental interpretation of sandy sequences. This study uses geochemical data to determine the provenance of aeolian sands from the Hetao Plain. Provenance discrimination diagrams revealed that the aeolian sands were mainly derived from mixed source felsic granites and granodiorites, which have undergone weak sedimentary recycling. The chemical index of alteration and A–CN–K data indicated that the aeolian sediments were transported over a short distance. Comparison of trace element and rare earth element (REE) ratios of the aeolian sands with rock samples from potential source areas has revealed that aeolian sand deposits in the Hetao Plain were mainly derived from Sertengshan and Yellow River sediments. The Langshan and Ordos Plateau may represent additional sand sources for the Hetao Plain.

Geochemistry of loess deposits in northeastern China: constraint on provenance and implication for disappearance of the large Songliao palaeolake

The Harbin loess, typical of the loess in NE China, is located in the easternmost margin of the Eurasian loess belt, and was recently investigated from the perspective of an Asian aeolian dust system. Before this study, the geochemical composition and provenance of the Harbin loess remained poorly understood. More importantly, the study of the Harbin loess also provides a unique opportunity to understand the geomorphological evolution process of the large Songliao palaeolake in the Northeast Plain. This study presents the results on the geochemical characteristics (major elements, trace elements, rare earth elements and Sr–Nd isotope) of the Harbin loess. There are markedly consistent geochemical compositions in and between the loess and palaeosol sediments, revealing stable dust sources and identical sources for the loess and palaeosol. Various indicators illustrating weathering and recycling indicate that the Harbin loess–palaeosol sediments were derived from sources with a low degree of weathering and from material with first-cycle alluvial–lacustrine deposits. Combinations of various provenance tracing indicators indicate that the Harbin loess has a strong geochemical affinity with the Songnen Sandy Land and to a certain extent the Horqin Sandy Land but not with the Hulun Buir Sandy Land, which indicates that these loess deposits are derived from a mixed provenance, with the dominant source being the neighbouring Songnen Sandy Land and a second, distal source being the Horqin Sandy Land. Finally, we advocate that the Harbin loess accumulation could serve as the direct record of the Songliao palaeolake disappearance. Supplementary material: Data for the NE Sandy Lands of China, and full provenance discrimination diagrams are available at https://doi.org/10.6084/m9.figshare.c.3835009 .