The Early-Middle Devonian Shugouzi Formation in the Quruqtagh block consists mainly of clastic rocks.However,their provenance has been scarcely studied since it was named.Geochemistry of clastic rocks was commonly use...The Early-Middle Devonian Shugouzi Formation in the Quruqtagh block consists mainly of clastic rocks.However,their provenance has been scarcely studied since it was named.Geochemistry of clastic rocks was commonly used to interpret the provenance.Detrital heavy mineral analyses help frame the U-Pb age from zircon grains,integrated with geochemical data from detrital tourmaline and spinels.These techniques were used to characterize components of the sediment flux and define erosion areas in the Qurugtagh block,further providing evidence about the tectonic evolution of the South Tianshan and Tarim plate.The maximum depositional age constrained by detrital zircon dating was Early-Middle Devonian.Multiple diagrams for sedimentary provenance using major and trace elements indicate that continental island arc-related felsic rocks were the major source rocks for the Shugouzi Formation.Detrital tourmalines are dravite and schorl.The results of detrital tourmaline electron probe microanalysis(EPMA)show that the source rocks are mainly metasedimentary rocks and granitoids.The detrital chromian spinels within the sediments are characterized by high chroumium(Cr^(#))and varying magnesium(Mg^(#)).The discrimination plots reveal that these spinels were sourced from island arc magmatic rocks.The laser ablation inductively-coupled plasma mass spectrometry(LA-ICP-MS)U-Pb chronology of detrital zircons suggests that the sediments were derived mainly from 414-491 Ma and 744-996 Ma magmatic rocks.Paleocurrent restoration,sandstone geochemistry,EPMA,and detrital zircon geochronology indicate that the source rocks were predominantly derived from Late Ordovician and Devonian magmatic rocks and subordinately from recycled Neoproterozoic magmatic rocks.Comprehensive analyses of the source areas suggest that a remnant arc still existed in the Early Devonian and the Shugouzi Formation was deposited in a passive continental margin.展开更多
The Shichuanhe River,a major tributary of the lower Weihe River,is situated in Xi’an,Shaanxi Province,China.It holds signifi cant information regarding the evolution of the Northern Weihe River,making its study cruci...The Shichuanhe River,a major tributary of the lower Weihe River,is situated in Xi’an,Shaanxi Province,China.It holds signifi cant information regarding the evolution of the Northern Weihe River,making its study crucial for understanding environmental changes in the region.Despite its importance,research on the Shichuanhe River basin has thus far been primarily focused on riverbank construction,with limited exploration of its sediment characteristics.Although river sediments hold potential for guiding agricultural practices in the area,comprehensive studies on their composition and provenance remain scarce.To address this gap,a systematic sediment sampling campaign was conducted in the lower reaches of the Shichuanhe River,and detailed mineralogical analyses were performed.The results show that the sediment is predominantly composed of detrital quartz and feldspar(albite and orthoclase),with heavy minerals constituting approximately 10%–12%of the total sediment volume.The analysis of the heavy mineral assemblage reveals an absence of signifi cant contributions from igneous rocks in the sedimentary profi le.Furthermore,the distribution patterns of major,trace,and rare-earth elements in the Shichuanhe River’s argillaceous sediments exhibit similarities to those found in the Weihe River’s sediments.Elemental fractionation patterns suggest that the Shichuanhe River sediments are primarily derived from Loess Plateau sediments,aligning with fi ndings from both the Weihe River and the middle reaches of the Yellow River.展开更多
The Erlian Basin is one of the most important multi-energy basins in China.The Baiyanhua area of the Chuanjing depression in the western Erlian Basin has recently become a favorable area for new progress in sandstone-...The Erlian Basin is one of the most important multi-energy basins in China.The Baiyanhua area of the Chuanjing depression in the western Erlian Basin has recently become a favorable area for new progress in sandstone-type uranium prospecting.However,the Cretaceous source-to-sink evolution of the Chuanjing depression in the Erlian Basin is poorly known.This paper presents the systematic geochemical and zircon U-Pb studies on the Saihantala Formation and Erlian Formation in the Baiyanhua area.The data obtained are functionally important for revealing the provenance and tectonic setting of the source rocks.The results show that the upper part of the Saihantala Formation and the lower part of the Erlian Formation are mainly composed of felsic sedimentary rocks.The source rocks originated from a continental margin arc environment in terms of tectonic setting.The detrital zircons ages have the dominant populations at ca.250-270 Ma,with two subdominant age groups at ca.1400-1800 and 1900-2100 Ma,respectively.Combined with the tectono-sedimentary evolution of the Chuanjing depression,we conclude that:(1)the provenance of the Cretaceous strata was mostly sourced from the Baiyanhua uplift;(2)the water depth became shallow in the Southern Sangendalai sag during the middle period of Saihantala,further preventing the formation of coal beds;(3)the formation of Baiyanhua uplift might provide the beneficial tectonic condition for uranium mineralization in the upper Saihantala Formation in southern Sangendalai sag.This is significant for us to understand the space allocation of coal and uranium in Chuanjing depression and evaluate the uranium metallogenic prospects in southern Sangendalai sag.展开更多
Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics,provenance,and tectonic implications.Petrographi...Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics,provenance,and tectonic implications.Petrographic features show that the sandstones are characterized by low-medium compositional maturity and textural maturity.The CIA and CIW values reveal weak and moderate weathering history in the source area.The geochemical characteristics together with palaeocurrent data show that the northwestern sediments were mainly derived from the Alxa Block with a typical recycled nature,while the provenance of the western and southwestern sediments were mainly from the Qinling-Qilian Orogenic Belt.The tectonic setting discrimination diagrams signify that the parent rocks of sandstones in the western and southern Ordos Basin were mainly developed from continental island arc,which is closely related to the evolution of the QinlingQilian Orogenic Belt.However,the sandstones in the northwestern Ordos Basin show complex features,which may be resulted from a typical recycling process.Overall evidence from petrography,geochemistry and sedimentology,together with previous researches suggest the Kongtongshan and Helanshan areas were the southwestern and northwestern boundary of the Ordos Basin,respectively,and there was no clear boundary between the Hexi Corridor Belt and Ordos Basin,where a large,uniform sediment dispersal system developed during the Late Triassic.展开更多
A combined inorganic and organic geochemical study was carried out on marls and mudstones collected from the Lower Miocene Lopare Basin,Bosnia and Herzegovina.A total of 46 samples collected from two boreholes,Pot 1(d...A combined inorganic and organic geochemical study was carried out on marls and mudstones collected from the Lower Miocene Lopare Basin,Bosnia and Herzegovina.A total of 46 samples collected from two boreholes,Pot 1(depth of 193 m)and Pot 3(depth of 344 m),showed that element abundances like boron(B),lithium(Li),strontium(Sr),uranium(U),chromium(Cr),nickel(Ni),magnesium(Mg),sodium(Na)and calcium(Ca)are much higher than average than in the upper continental crust(UCC).Chemical composition indicates at least two sources:(i)Mesozoic ophiolites occurring in the north of the investigated area,and(ii)dacito-andesitic pyroclastics(Mesozoic to Cenozoic).Lopare Basin sedimentation was influenced by strong evaporation resulting in a partly hypersaline lake,which formed during a warm climatic period,probably during the Miocene Climatic Optimum.A brief episode of humid climate conditions resulted in the basin fillingup and deposition of felsic sediments enriched in thorium(Th).Organic geochemistry shows that the majority of studied sediments contains predominantly immature to marginally mature algal organic matter(OM).The biomarker patterns are generally in agreement with the geological history of the Lopare Basin and inorganic and mineralogical data.Conversely,the molecular distribution of n-alkanes as reliable climatic andδ-MTTC as paleosalinity indicators do not support this conclusion.展开更多
In this study, whole-rock geochemical and Nd isotopic data, as well as detrital zircon Hf isotopes of Palaeoproterozoic metasedimentary rocks from the Jiangxian Group are presented to evaluate the characteristics of t...In this study, whole-rock geochemical and Nd isotopic data, as well as detrital zircon Hf isotopes of Palaeoproterozoic metasedimentary rocks from the Jiangxian Group are presented to evaluate the characteristics of their provenance and the tectonic history. The major and trace element compositions are comparable to Post-Archean upper continental crust （PA-UCC）, but have slight enrichment in the LILE, with the exception of Cs and Sr, and a slight depletion in ferromagnesian elements, HFS elements, such as Nb and Ta, and some major elements, such as CaP and Na2O. The geochemical data reveal that the collected metasedimentary rocks have experienced intermediate source weathering with chemical index of alteration values ranging from 72 to 78, varying degrees of K- metasomatism, and post-depositional loss of Na, as well as negligible sorting, and are derived from the weathering of mostly felsic and non-mafic rocks. The selected Lu-Hf isotopic analysis on detrital zircon points to both the Trans-North China Orogen and Eastern Block of the north China craton as the most likely sources for the metasedimentary rocks of the Jiangxian Group. However, a contribution of detritus from the Western Block of the north China craton can be ruled out. The sediments were probably deposited in a back-arc basin within an active continental margin setting.展开更多
Geochemical analysis of sandstones from the Sardar Formation （from two stratigraphic successions） in east-central Iran were used for identification of geochemical characterization of sandstones, provenance and tecto...Geochemical analysis of sandstones from the Sardar Formation （from two stratigraphic successions） in east-central Iran were used for identification of geochemical characterization of sandstones, provenance and tectonic setting. Sandstones in the two lithostratigraphic successions have similar chemical compositions suggesting a common provenance. Bulk-rock geochemistry analysis of Carboniferous sandstones from Sardar Formation indicates that they are mainly quartz dominated and are classified as quartzarenites, sublitharenites and subarkoses, derived from acid igneous to intermediate igneous rocks. Discrimination function analysis indicates that the sandstones of Sardar Formation were derived from quartzose sedimentary provenance in a recycled orogenic setting. Also, major and trace elements in sandstones of Sardar Formation （e.g., K2O/Na2O vs. SiO2 ） indicate deposition in a stable passive continental margin （PM）. Chemical index of alteration （CIA） for these rocks （65%） suggests a moderate to relatively high degree of weathering in the source area.展开更多
The Lishui Sag, in the East China Sea Shelf Basin, is rich in hydrocarbons, with the major hydrocarbon-bearing layers being the Paleocene Mingyuefeng clastic rocks. Analysis of the implicit geologic background informa...The Lishui Sag, in the East China Sea Shelf Basin, is rich in hydrocarbons, with the major hydrocarbon-bearing layers being the Paleocene Mingyuefeng clastic rocks. Analysis of the implicit geologic background information of these Paleocene clastic rocks using petrological and geochemical methods has significant practical importance. These Paleocene sandstones are mainly lithic arenite, lithic arkose and greywacke, composed of K-feldspar, plagioclase, authigenic clays, silica and carbonates. As continental deposits, Yueguifeng clastic rocks have high aluminosilicate and mafic detritus contents, while the Lingfeng and Mingyuefeng Formations are rich in silica due to an oscillating coastal marine depositional environment. The major element contents of these Paleocene sandstones are low and have a concentrated distribution, indicating that the geochemical composition is non-epigenetic, transformed by sedimentary processes and diagenesis. The Yueguifeng detritus comprises recycled sediments, controlled by moderate weathering and erosion, while the Lingfeng and Mingyuefeng detritus is interpreted as primarily first-cycle materials due to low chemical weathering. In the Late Cretaceous to Early Paleocene, the Pacific Plate began subducting under the Eurasian Plate, causing an orogeny by plate collision and magma eruption due to the melting of subducted oceanic crust. This resulted in the dual tectonic settings of ＂active margin＂ and ＂continental island arc＂ in the East China Sea Shelf Basin. During the Late Paleocene, the Pacific Plate margin migrated eastward along with development of the Philippine Ocean Plate, and the tectonic setting of the Lishui Sag gradually turned into a passive continental margin. Detrital sources included both orogenic continental blocks and continental island arcs, and the parent rocks are primarily felsic volcanic rocks and granites.展开更多
The purpose of this paper is to determine the provenance and tectonic setting of the Phu Khat Formation and get a better understanding of the tectonic evolution of the Nakhon Thai region using the petrography and whol...The purpose of this paper is to determine the provenance and tectonic setting of the Phu Khat Formation and get a better understanding of the tectonic evolution of the Nakhon Thai region using the petrography and whole-rock geochemistry integrated with the U-Pb detrital zircon dating. The sandstone of the Late Cretaceous to Early Tertiary Phu Khat Formation is chiefly characterized by unsorted texture and highly unstable volcanic lithic fragments. The formation overlies unconformably on a high textural and mineral maturity of clastic sandstone of the Late Cretaceous Khao Ya Puk Formation. Geochemically, the tectonic setting discrimination（K2O/Na2O-SiO2, Al2O3/SiO2-Fe2O3＋Mg O, and Th-Sc-Zr/10） and the petrography indicate that the Phu Khat Formation was accumulated in a passive margin tectonic setting which is the same as the Khao Ya Puk Formation but with a different depositional environment. The plots of geochemical provenance discrimination（La/Th-Hf, Th/Sc-Zr/Sc, Eu anomaly Eu/Eu＊ 0.42 to 0.74） and the petrography reveal that the provenance of the Khao Ya Puk Formation is mainly recycled sedimentary rocks while the Phu Khat Formation consists primarily of recycled sedimentary rocks associated with minor felsic volcanic rocks from the old continental island arc of the uplifted either western or eastern continental terranes or both. However, the U-Pb detrital zircon dating indicates a unique provenance of the Phu Khat Formation from the terrane west of the Nakhon Thai region where the volcanic continental arc is active predominantly in the Middle to Late Triassic. The results indicate that while the Phu Khat Formation was accumulated in Nakhon Thai region, the western terrane was uplifted by reactivation of the preexisting structure probably since the Maastrichtian time to be the source area of sediments. Meanwhile, the eastern terrane（mainly Loei-Phetchabun fold belt） had not been uplifted probably until, the accumulation of the Phu Khat Formation terminated. Subsequently, the whole region began to uplift forming a high mountainous area since the Ypresian time when the Greater India collided with the Eurasia.展开更多
The Asmari Formation deposited in the Zagros foreland basin during the OligoceneMiocene.Lithologically,the Asmari Formation consists of limestone,dolomitic limestone,dolomite,argillaceous limestone,some anhydrite （Ka...The Asmari Formation deposited in the Zagros foreland basin during the OligoceneMiocene.Lithologically,the Asmari Formation consists of limestone,dolomitic limestone,dolomite,argillaceous limestone,some anhydrite （Kalhur Member） and sandstones （Ahwaz Member）.This study is based on the analysis of core samples from four subsurface sections （wells Mn-68,Mn-281,Mn-292 and Mn-312） in the Marun Oilfieid in the Dezful embayment subzone in order to infer their provenance and tectonic setting of the Ahwaz Sandstone Member.Petrographical data reveal that the Ahwaz Sandstone comprises 97.5% quartz,1.6% feldspar,and 0.9% rock fragments and all samples are classified as quartz arenites.The provenance and tectonic setting of the Ahwaz Sandstone have been assessed using integrated petrographic and geochemical studies.Petrographic analysis reveals that mono-and poly-crystalline quartz grains from metamorphic and igneous rocks of a craton interior setting were the dominant sources.Chemically,major and trace element concentrations in the rocks of the Ahwaz Sandstone indicate deposition in a passive continental margin setting.As indicated by the CIW index （chemical index of weathering） of the Ahwaz Sandstone （average value of 82） their source area underwent ＂intense＂ recycling but ＂moderate to high＂ degree of chemical weathering.The petrography and geochemistry results are consistent with a tropical,humid climate and low-relief highlands.展开更多
Major, trace and rare earth element （REE） concentrations of Late Triassic sediments （fine- grained sandstones and mudstones） from Hongcan Well 1 in the NE part of the Songpan-Ganzi Basin, western China, are used t...Major, trace and rare earth element （REE） concentrations of Late Triassic sediments （fine- grained sandstones and mudstones） from Hongcan Well 1 in the NE part of the Songpan-Ganzi Basin, western China, are used to reveal weathering, provenance and tectonic setting of inferred source areas. The Chemical Index of Alteration （CIA） reflects a low to moderate degree of chemical weathering in a cool and somewhat dry climate, and an A-CN-K plot suggests an older upper continental crust prove- nance dominated by felsic to intermediate igneous rocks of average tonalite composition. Based on the various geochemical tectonic setting discrimination diagrams, the Late Triassic sediments are inferred to have been deposited in a back-arc basin situated between an active continental margin （the Kunlun- Qinling Fold Belt） and a continental island arc （the Yidun Island Arc）. The Triassic sediments in the study area underwent a rapid erosion and burial in a proximal slope-basin environment by the petrographic data,while the published flow directions of Triassic turbidites in the Aba-Zoige region was not supported Yidun volcanic arc source. Therefore, we suggest that the Kunlun-Qinling terrane is most likely to have supplied source materials to the northeast part of the Songpan-Ganzi Basin during the Late Triassic.展开更多
The contribution of substance from Yellow River, Yangtze River, and Korean rivers to the sedimentation of Yellow Sea is studied through geochemical analysis and through characterization of the source of the substance ...The contribution of substance from Yellow River, Yangtze River, and Korean rivers to the sedimentation of Yellow Sea is studied through geochemical analysis and through characterization of the source of the substance about sediment from Core NT1 among the lutaceous area in Central South Yellow Sea. The research finds out that the sediment in Core NT1 mainly comes from Yangtze River and Yellow River, the sediment between 0-7.70 m in upper Core NT1 mainly belongs to Yangtze River source; the sediments between 7.70-16.60 m and 42.0-54.80 m in middle Core NT1 are mainly from Yellow River, the 26 m thick sediment interlayer in it mainly comes from Yangtze River; and the sediment between 54.80-69.76 m in the bottom of Core NT1 is mainly from Yangtze River. The results demonstrate that Yangtze River has been playing a main role in the lutaceous area in the Central South Yellow Sea since early Late Pleistocene, and Yellow River started to influence the continental sedimentation of Yellow Sea from early Warm Glaciation of late Late Pleistocene.展开更多
The Palaeo–Mesoproterozoic Tadapatri formation of the Cuddapah basin is comprised of clastic sedimentary rocks with minor carbonates and mafic–ultramafic sill bodies. Geochemistry of the shale is used to study the p...The Palaeo–Mesoproterozoic Tadapatri formation of the Cuddapah basin is comprised of clastic sedimentary rocks with minor carbonates and mafic–ultramafic sill bodies. Geochemistry of the shale is used to study the provenance, paleoweathering and paleoredox conditions of this Tadpatri formation in order to better understand the development of the Cuddapah basin during Palaeo–Mesoproterozoic time. The higher CIA(average 74.39), PIA(average 85.94) and CIW(average 87.59) values of the Tadpatri shales suggest intensely weathered sources.Higher Al2_ O_3/TiO_2(average 30.78) and LREE/HREE ratio(average 8.80) with negative europium anomaly indicate derivation of the clastic sediments from a felsic source rock. The geochemical parameters like U, U/Th, Cu/Zn,Ni/Co, V/Cr ratios reveal that the Tadpatri shales are mainly deposited in an oxic condition.展开更多
Petrographical and geochemical methods were combined to investigate the provenance, geodynamic and weathering history of the Shurijeh sandstones, Kopet-Dagh Basin. The point-counting method and XRF technique are used ...Petrographical and geochemical methods were combined to investigate the provenance, geodynamic and weathering history of the Shurijeh sandstones, Kopet-Dagh Basin. The point-counting method and XRF technique are used for modal and geochemical analyses. Based on petrographical examinations, it seems that the Shurijeh sandstones are mainly deposited in the craton interior and recycled orogen belts. In addition to petrographical investigation, geochemical analyses （major oxides and trace elements） of Late Jurassic-Early Cretaceous rocks reveal that the sedimentation processes are performed in a passive continental margin. Such interpretation is supported with geodynamic and paleogeographical studies of the Kopeh-Dagh basin during this time. The geochemical investigations suggested that the composition of probable source rocks mostly was acidic-intermediate with minor mafic igneous rocks. Based on the above, Paleo-Tethys remnants and their collision-related granitoids, in the south and west of Mashhad, may have been the source area for these rocks. CIA values, which range from 63.8 to 94.9 in samples, are suggesting a moderate to relatively high degree of alteration （weathering） in the source area. Therefore, petrographical and paleogeographical studies of siliciclastic rocks can be used for the provenance, tectonic setting and paleoweathering studies in the source area.展开更多
Tertiary sandstones collected from southwest Sarawak, Malaysia, were analyzed to decipher their provenance, weathering, and tectonic setting. The studied sandstones have a sublitharenite composition and are dominantly...Tertiary sandstones collected from southwest Sarawak, Malaysia, were analyzed to decipher their provenance, weathering, and tectonic setting. The studied sandstones have a sublitharenite composition and are dominantly composed quartz with little mica and feldspar, and a small amount of volcanic fragments. These sand- stones were generally derived from quartz-rich recycled orogenic sources. They have relatively high SiO2 content with low Na20, CaO, MnO, and MgO contents. Values of Chemical Index of Alteration （CIA） of these rock samples vary from 71 to 93, with an average of 81, implying intense chemical alteration during weathering. A felsic igneous source is suggested by a low concentration of TiO2 com- pared to CIA, enrichment of Light Rare Earth Elements, depletion of Heavy Rare Earth Elements, and negative Eu anomalies. A felsic origin is further supported by a Eu/Eu＊ range of 0.65-0.85 and high Th/Sc, La/Sc, La/Co, and Th/ Co ratios. This work presents the first reported geochemical data of Tertiary sandstones of the Sarawak Basin. These data led us to conclude that the sandstones were dislodged from recycled orogenic sources and deposited in a slowly subsiding rifted basin in a passive continental tectonic setting.展开更多
The sedimentary record of mud areas is an important carrier of information on the Holocene evolution of marine environments. Based on fine interpretations of the shallow stratigraphic section data, a small mud deposit...The sedimentary record of mud areas is an important carrier of information on the Holocene evolution of marine environments. Based on fine interpretations of the shallow stratigraphic section data, a small mud deposit area has been found in the southern coastal waters off Shandong Peninsula. This mud area is mainly distributed in coastal waters north of Laoshantou to the vicinity of Rushan Estuary. Overall, it is parallel to the coastline and spreads in a banded pattern, gradually thinning from offshore to the sea. The isopach map of depth distribution is parallel with the shoreline, and the depocenter lies in coastal waters of the Aoshan Bay where the maximum thickness is up to 22.5 m. Accelerator mass spectrometry（AMS） ^（14）C dating shows that the mud area was formed in the Holocene. The test data of surface sediments from the mud area, including particle size, mineral characteristics, and rare earth element contents, are used in comparisons with the composition of materials from the major surrounding medium and small rivers flowing into the sea and the Huanghe（Yellow） River. In this paper, the sedimentary characteristics and provenance of the mud deposit area are discussed. The results show that the formation of this mud area resulted from the joint action of the Huanghe River and surrounding rivers flowing into the sea.展开更多
The geochemical composition of sandstones in the sedimentary basin is controlled mainly by the tectonic setting of the provenance, and it is therefore possible to reveal the tectonic setting of the provenance and the ...The geochemical composition of sandstones in the sedimentary basin is controlled mainly by the tectonic setting of the provenance, and it is therefore possible to reveal the tectonic setting of the provenance and the nature of source rocks in terms of the geochemical composition of sandstones. The major elements, rare\|earth elements and trace elements of the Mesozoic\|Cenozoic sandstones in the Lanping Basin are studied in this paper, revealing that the tectonic settings of the provenance for Mesozoic\|Cenozoic sedimentary rocks in the Lanping Basin belong to a passive continental margin and a continental island arc. Combined with the data on sedimentary facies and palaeogeography, it is referred that the eastern part of the basin is located mainly at the tectonic setting of the passive continental margin before Mesozoic, whereas the western part may be represented by a continental island arc. This is compatible with the regional geology data. The protoliths of sedimentary rocks should be derived from the upper continental crust, and are composed mainly of felsic rocks, mixed with some andesitic rocks and old sediment components. Therefore, the Lanping Mesozoic\|Cenozoic Basin is a typical continental\|type basin. This provides strong geochemical evidence for the evolution of the paleo\|Tethys and the basin\|range transition.展开更多
Generalized the use of neutron activation analysis(NAA)in the investigations of unique processes occurring in early stages of formations and evolution of bodies in solar system Out of them the formation of chondrules,...Generalized the use of neutron activation analysis(NAA)in the investigations of unique processes occurring in early stages of formations and evolution of bodies in solar system Out of them the formation of chondrules,emergence of ultra refractory inclusions in carbonaceous chondrites,formation of metallic and silicate phases of iron and stone meteorites,and formation of iron meteorites of different chemical groups Changes in regolite and lunar rock contents,differentiation in the upper mantle matter, identification of earthly meteoritic craters,transportation of cosmic(meteoritic)materials on to the Earth, investigations of unique events like Tunguska fall of the year 1908 and also ore formation studies and processes taking place on geochemical barrier type river-sea,ocean-atmosphere and so on Prospectives of NAA are pointed out展开更多
In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of th...In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of the rocks.Petrographic and geochemical analyses of major and minor elements of the samples were used for this purpose.This Formation is composed of three major facies including conglomerate,fine sandstone,and mudstone.The source formations which were recognized to be supplying sediments to the Cheleken Formation depositional basin include Lalun,Ziarat,Tizkuh,Dalichai,and Cretaceous formations.According to the discrimination diagrams and other ratios for minor elements of the studied samples,a complex of felsic to intermediate igneous rocks in the source region was deciphered.The depositional environment of the rocks experienced humid and semi-arid climatic conditions during deposition.According to the CIW index,the samples underwent a high level of weathering(97%)in the source area or during transportation.From a tectonic point of view,the Cheleken Formation was deposited in an Active Continental Margin setting.展开更多
This study was conducted on the Ngaoundaba Crater Lake sediments to infer provenance,weathering conditions,organic matter accumulation,and trace metal concentrations.Ngaoundaba Lake sediments were collected using a ma...This study was conducted on the Ngaoundaba Crater Lake sediments to infer provenance,weathering conditions,organic matter accumulation,and trace metal concentrations.Ngaoundaba Lake sediments were collected using a manual core sampler at 5 to 8 m water depth.Two sediment cores from the littoral and center of the lake were analyzed for grain size distribution,water content(WC),organic matter content,mineralogy,and major and trace element concentrations.The Ngaoundaba sediments were classified as silt and sandy silt.Sediments show high content in organic matter,which is more to the littoral than to the center of the lake,varying from 14.6%to 24%and21.2%to 40.8%,respectively.The grain surface features identified by Scanning Electron Microscopy(SEM)show both chemical and mechanical microtextures with subrounded to angular shape suggesting both proximal and distal sources.The lake sediments are composed of quartz,kaolinite,and hematite,with low amounts of feldspars,rutile,calcite,illite,and ilmenite.Weathering indices such as the chemical index of alteration(CIA),chemical index of weathering(CIW),and index of compositional variability(ICV)indicate moderate to intense chemical weathering in the source area and immature to mature sediments.The geochemical composition indicates that the sediments were derived from felsic to intermediate igneous rocks,such as granitoids,and mafic alkali lavas like basanites.The environmental risk assessment of trace metals obtained by enrichment factor(EF)and geo-accumulation index(I-geo)shows low contamination of the lake sediments.展开更多
基金financially supported by Deep Resources Exploration and Mining Project(Grant No.2019YFC0605202)Chinese Geological Survey(Grant No.DD20221684)。
文摘The Early-Middle Devonian Shugouzi Formation in the Quruqtagh block consists mainly of clastic rocks.However,their provenance has been scarcely studied since it was named.Geochemistry of clastic rocks was commonly used to interpret the provenance.Detrital heavy mineral analyses help frame the U-Pb age from zircon grains,integrated with geochemical data from detrital tourmaline and spinels.These techniques were used to characterize components of the sediment flux and define erosion areas in the Qurugtagh block,further providing evidence about the tectonic evolution of the South Tianshan and Tarim plate.The maximum depositional age constrained by detrital zircon dating was Early-Middle Devonian.Multiple diagrams for sedimentary provenance using major and trace elements indicate that continental island arc-related felsic rocks were the major source rocks for the Shugouzi Formation.Detrital tourmalines are dravite and schorl.The results of detrital tourmaline electron probe microanalysis(EPMA)show that the source rocks are mainly metasedimentary rocks and granitoids.The detrital chromian spinels within the sediments are characterized by high chroumium(Cr^(#))and varying magnesium(Mg^(#)).The discrimination plots reveal that these spinels were sourced from island arc magmatic rocks.The laser ablation inductively-coupled plasma mass spectrometry(LA-ICP-MS)U-Pb chronology of detrital zircons suggests that the sediments were derived mainly from 414-491 Ma and 744-996 Ma magmatic rocks.Paleocurrent restoration,sandstone geochemistry,EPMA,and detrital zircon geochronology indicate that the source rocks were predominantly derived from Late Ordovician and Devonian magmatic rocks and subordinately from recycled Neoproterozoic magmatic rocks.Comprehensive analyses of the source areas suggest that a remnant arc still existed in the Early Devonian and the Shugouzi Formation was deposited in a passive continental margin.
基金supported by the Key Project of Natural Science Basic Research Program of Shaanxi Province(2023-JC-ZD-16).
文摘The Shichuanhe River,a major tributary of the lower Weihe River,is situated in Xi’an,Shaanxi Province,China.It holds signifi cant information regarding the evolution of the Northern Weihe River,making its study crucial for understanding environmental changes in the region.Despite its importance,research on the Shichuanhe River basin has thus far been primarily focused on riverbank construction,with limited exploration of its sediment characteristics.Although river sediments hold potential for guiding agricultural practices in the area,comprehensive studies on their composition and provenance remain scarce.To address this gap,a systematic sediment sampling campaign was conducted in the lower reaches of the Shichuanhe River,and detailed mineralogical analyses were performed.The results show that the sediment is predominantly composed of detrital quartz and feldspar(albite and orthoclase),with heavy minerals constituting approximately 10%–12%of the total sediment volume.The analysis of the heavy mineral assemblage reveals an absence of signifi cant contributions from igneous rocks in the sedimentary profi le.Furthermore,the distribution patterns of major,trace,and rare-earth elements in the Shichuanhe River’s argillaceous sediments exhibit similarities to those found in the Weihe River’s sediments.Elemental fractionation patterns suggest that the Shichuanhe River sediments are primarily derived from Loess Plateau sediments,aligning with fi ndings from both the Weihe River and the middle reaches of the Yellow River.
基金funded by the project initiated by the China Geological Survey“Investigation of sandstone-type uranium deposits in the Ordos and Qaidam Basins”(No.DD20190119)the National Key Research and Development Project(No.2018YFC0604200)from the Ministry of Science and Technology of the International Geoscience Programme(No.IGCP675),which is a joint endeavor of UNESCO and IUGS。
文摘The Erlian Basin is one of the most important multi-energy basins in China.The Baiyanhua area of the Chuanjing depression in the western Erlian Basin has recently become a favorable area for new progress in sandstone-type uranium prospecting.However,the Cretaceous source-to-sink evolution of the Chuanjing depression in the Erlian Basin is poorly known.This paper presents the systematic geochemical and zircon U-Pb studies on the Saihantala Formation and Erlian Formation in the Baiyanhua area.The data obtained are functionally important for revealing the provenance and tectonic setting of the source rocks.The results show that the upper part of the Saihantala Formation and the lower part of the Erlian Formation are mainly composed of felsic sedimentary rocks.The source rocks originated from a continental margin arc environment in terms of tectonic setting.The detrital zircons ages have the dominant populations at ca.250-270 Ma,with two subdominant age groups at ca.1400-1800 and 1900-2100 Ma,respectively.Combined with the tectono-sedimentary evolution of the Chuanjing depression,we conclude that:(1)the provenance of the Cretaceous strata was mostly sourced from the Baiyanhua uplift;(2)the water depth became shallow in the Southern Sangendalai sag during the middle period of Saihantala,further preventing the formation of coal beds;(3)the formation of Baiyanhua uplift might provide the beneficial tectonic condition for uranium mineralization in the upper Saihantala Formation in southern Sangendalai sag.This is significant for us to understand the space allocation of coal and uranium in Chuanjing depression and evaluate the uranium metallogenic prospects in southern Sangendalai sag.
基金the National Natural Science Foundation of China [Grant No. 41802119 and 41602212]Natural Science Foundation of Shaanxi [Grant No. 2019JQ-088]+1 种基金Special Projects of China Geological Survey [Grant No. 12120113039900 and 12120114009201]Doctor’s fund of Xi’an University of Science and Technology [Grant No. 2017QDJ051]
文摘Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics,provenance,and tectonic implications.Petrographic features show that the sandstones are characterized by low-medium compositional maturity and textural maturity.The CIA and CIW values reveal weak and moderate weathering history in the source area.The geochemical characteristics together with palaeocurrent data show that the northwestern sediments were mainly derived from the Alxa Block with a typical recycled nature,while the provenance of the western and southwestern sediments were mainly from the Qinling-Qilian Orogenic Belt.The tectonic setting discrimination diagrams signify that the parent rocks of sandstones in the western and southern Ordos Basin were mainly developed from continental island arc,which is closely related to the evolution of the QinlingQilian Orogenic Belt.However,the sandstones in the northwestern Ordos Basin show complex features,which may be resulted from a typical recycling process.Overall evidence from petrography,geochemistry and sedimentology,together with previous researches suggest the Kongtongshan and Helanshan areas were the southwestern and northwestern boundary of the Ordos Basin,respectively,and there was no clear boundary between the Hexi Corridor Belt and Ordos Basin,where a large,uniform sediment dispersal system developed during the Late Triassic.
基金partly financed by the Ministry of Education,Science and Technological Development,Republic of Serbia(Grant No.451-03-68/2020-14/200026 and Project 176006)。
文摘A combined inorganic and organic geochemical study was carried out on marls and mudstones collected from the Lower Miocene Lopare Basin,Bosnia and Herzegovina.A total of 46 samples collected from two boreholes,Pot 1(depth of 193 m)and Pot 3(depth of 344 m),showed that element abundances like boron(B),lithium(Li),strontium(Sr),uranium(U),chromium(Cr),nickel(Ni),magnesium(Mg),sodium(Na)and calcium(Ca)are much higher than average than in the upper continental crust(UCC).Chemical composition indicates at least two sources:(i)Mesozoic ophiolites occurring in the north of the investigated area,and(ii)dacito-andesitic pyroclastics(Mesozoic to Cenozoic).Lopare Basin sedimentation was influenced by strong evaporation resulting in a partly hypersaline lake,which formed during a warm climatic period,probably during the Miocene Climatic Optimum.A brief episode of humid climate conditions resulted in the basin fillingup and deposition of felsic sediments enriched in thorium(Th).Organic geochemistry shows that the majority of studied sediments contains predominantly immature to marginally mature algal organic matter(OM).The biomarker patterns are generally in agreement with the geological history of the Lopare Basin and inorganic and mineralogical data.Conversely,the molecular distribution of n-alkanes as reliable climatic andδ-MTTC as paleosalinity indicators do not support this conclusion.
基金supported by a NSFC project(no.:40602022)a China Postdoctoral Science Foundation Grant,a NSFC MajorInternational Joint Research Project(no.:40420120135)the Ministry of Science and Technology of People's Republic of China(no.:2006BAB01A11 and2002CB412608)
文摘In this study, whole-rock geochemical and Nd isotopic data, as well as detrital zircon Hf isotopes of Palaeoproterozoic metasedimentary rocks from the Jiangxian Group are presented to evaluate the characteristics of their provenance and the tectonic history. The major and trace element compositions are comparable to Post-Archean upper continental crust （PA-UCC）, but have slight enrichment in the LILE, with the exception of Cs and Sr, and a slight depletion in ferromagnesian elements, HFS elements, such as Nb and Ta, and some major elements, such as CaP and Na2O. The geochemical data reveal that the collected metasedimentary rocks have experienced intermediate source weathering with chemical index of alteration values ranging from 72 to 78, varying degrees of K- metasomatism, and post-depositional loss of Na, as well as negligible sorting, and are derived from the weathering of mostly felsic and non-mafic rocks. The selected Lu-Hf isotopic analysis on detrital zircon points to both the Trans-North China Orogen and Eastern Block of the north China craton as the most likely sources for the metasedimentary rocks of the Jiangxian Group. However, a contribution of detritus from the Western Block of the north China craton can be ruled out. The sediments were probably deposited in a back-arc basin within an active continental margin setting.
基金supported by a grant to the senior author from Faculty of Sciences, Ferdowsi University of Mashhad
文摘Geochemical analysis of sandstones from the Sardar Formation （from two stratigraphic successions） in east-central Iran were used for identification of geochemical characterization of sandstones, provenance and tectonic setting. Sandstones in the two lithostratigraphic successions have similar chemical compositions suggesting a common provenance. Bulk-rock geochemistry analysis of Carboniferous sandstones from Sardar Formation indicates that they are mainly quartz dominated and are classified as quartzarenites, sublitharenites and subarkoses, derived from acid igneous to intermediate igneous rocks. Discrimination function analysis indicates that the sandstones of Sardar Formation were derived from quartzose sedimentary provenance in a recycled orogenic setting. Also, major and trace elements in sandstones of Sardar Formation （e.g., K2O/Na2O vs. SiO2 ） indicate deposition in a stable passive continental margin （PM）. Chemical index of alteration （CIA） for these rocks （65%） suggests a moderate to relatively high degree of weathering in the source area.
基金supported by the Fundamental Research Funds for the Central Universities of Ocean University of China(201413005)a China National Science and Technology Major Project(2011ZX05023003)Shanghai Branch,China National Offshore Oil Co.,Ltd.(CNOOC)
文摘The Lishui Sag, in the East China Sea Shelf Basin, is rich in hydrocarbons, with the major hydrocarbon-bearing layers being the Paleocene Mingyuefeng clastic rocks. Analysis of the implicit geologic background information of these Paleocene clastic rocks using petrological and geochemical methods has significant practical importance. These Paleocene sandstones are mainly lithic arenite, lithic arkose and greywacke, composed of K-feldspar, plagioclase, authigenic clays, silica and carbonates. As continental deposits, Yueguifeng clastic rocks have high aluminosilicate and mafic detritus contents, while the Lingfeng and Mingyuefeng Formations are rich in silica due to an oscillating coastal marine depositional environment. The major element contents of these Paleocene sandstones are low and have a concentrated distribution, indicating that the geochemical composition is non-epigenetic, transformed by sedimentary processes and diagenesis. The Yueguifeng detritus comprises recycled sediments, controlled by moderate weathering and erosion, while the Lingfeng and Mingyuefeng detritus is interpreted as primarily first-cycle materials due to low chemical weathering. In the Late Cretaceous to Early Paleocene, the Pacific Plate began subducting under the Eurasian Plate, causing an orogeny by plate collision and magma eruption due to the melting of subducted oceanic crust. This resulted in the dual tectonic settings of ＂active margin＂ and ＂continental island arc＂ in the East China Sea Shelf Basin. During the Late Paleocene, the Pacific Plate margin migrated eastward along with development of the Philippine Ocean Plate, and the tectonic setting of the Lishui Sag gradually turned into a passive continental margin. Detrital sources included both orogenic continental blocks and continental island arcs, and the parent rocks are primarily felsic volcanic rocks and granites.
文摘The purpose of this paper is to determine the provenance and tectonic setting of the Phu Khat Formation and get a better understanding of the tectonic evolution of the Nakhon Thai region using the petrography and whole-rock geochemistry integrated with the U-Pb detrital zircon dating. The sandstone of the Late Cretaceous to Early Tertiary Phu Khat Formation is chiefly characterized by unsorted texture and highly unstable volcanic lithic fragments. The formation overlies unconformably on a high textural and mineral maturity of clastic sandstone of the Late Cretaceous Khao Ya Puk Formation. Geochemically, the tectonic setting discrimination（K2O/Na2O-SiO2, Al2O3/SiO2-Fe2O3＋Mg O, and Th-Sc-Zr/10） and the petrography indicate that the Phu Khat Formation was accumulated in a passive margin tectonic setting which is the same as the Khao Ya Puk Formation but with a different depositional environment. The plots of geochemical provenance discrimination（La/Th-Hf, Th/Sc-Zr/Sc, Eu anomaly Eu/Eu＊ 0.42 to 0.74） and the petrography reveal that the provenance of the Khao Ya Puk Formation is mainly recycled sedimentary rocks while the Phu Khat Formation consists primarily of recycled sedimentary rocks associated with minor felsic volcanic rocks from the old continental island arc of the uplifted either western or eastern continental terranes or both. However, the U-Pb detrital zircon dating indicates a unique provenance of the Phu Khat Formation from the terrane west of the Nakhon Thai region where the volcanic continental arc is active predominantly in the Middle to Late Triassic. The results indicate that while the Phu Khat Formation was accumulated in Nakhon Thai region, the western terrane was uplifted by reactivation of the preexisting structure probably since the Maastrichtian time to be the source area of sediments. Meanwhile, the eastern terrane（mainly Loei-Phetchabun fold belt） had not been uplifted probably until, the accumulation of the Phu Khat Formation terminated. Subsequently, the whole region began to uplift forming a high mountainous area since the Ypresian time when the Greater India collided with the Eurasia.
基金the Ferdowsi University of Mashhad for their logistic support during this study
文摘The Asmari Formation deposited in the Zagros foreland basin during the OligoceneMiocene.Lithologically,the Asmari Formation consists of limestone,dolomitic limestone,dolomite,argillaceous limestone,some anhydrite （Kalhur Member） and sandstones （Ahwaz Member）.This study is based on the analysis of core samples from four subsurface sections （wells Mn-68,Mn-281,Mn-292 and Mn-312） in the Marun Oilfieid in the Dezful embayment subzone in order to infer their provenance and tectonic setting of the Ahwaz Sandstone Member.Petrographical data reveal that the Ahwaz Sandstone comprises 97.5% quartz,1.6% feldspar,and 0.9% rock fragments and all samples are classified as quartz arenites.The provenance and tectonic setting of the Ahwaz Sandstone have been assessed using integrated petrographic and geochemical studies.Petrographic analysis reveals that mono-and poly-crystalline quartz grains from metamorphic and igneous rocks of a craton interior setting were the dominant sources.Chemically,major and trace element concentrations in the rocks of the Ahwaz Sandstone indicate deposition in a passive continental margin setting.As indicated by the CIW index （chemical index of weathering） of the Ahwaz Sandstone （average value of 82） their source area underwent ＂intense＂ recycling but ＂moderate to high＂ degree of chemical weathering.The petrography and geochemistry results are consistent with a tropical,humid climate and low-relief highlands.
基金supported by the SINOPEC Exploration Southern Company(the National Oil and Gas Special Projects XQ-04)the Special Fund for Basic Scientific Research of Central Colleges, Chang'an University(CHD2011JC185)
文摘Major, trace and rare earth element （REE） concentrations of Late Triassic sediments （fine- grained sandstones and mudstones） from Hongcan Well 1 in the NE part of the Songpan-Ganzi Basin, western China, are used to reveal weathering, provenance and tectonic setting of inferred source areas. The Chemical Index of Alteration （CIA） reflects a low to moderate degree of chemical weathering in a cool and somewhat dry climate, and an A-CN-K plot suggests an older upper continental crust prove- nance dominated by felsic to intermediate igneous rocks of average tonalite composition. Based on the various geochemical tectonic setting discrimination diagrams, the Late Triassic sediments are inferred to have been deposited in a back-arc basin situated between an active continental margin （the Kunlun- Qinling Fold Belt） and a continental island arc （the Yidun Island Arc）. The Triassic sediments in the study area underwent a rapid erosion and burial in a proximal slope-basin environment by the petrographic data,while the published flow directions of Triassic turbidites in the Aba-Zoige region was not supported Yidun volcanic arc source. Therefore, we suggest that the Kunlun-Qinling terrane is most likely to have supplied source materials to the northeast part of the Songpan-Ganzi Basin during the Late Triassic.
基金This paper is supported by the National Land Resources Survey Project (No. 200211000001).
文摘The contribution of substance from Yellow River, Yangtze River, and Korean rivers to the sedimentation of Yellow Sea is studied through geochemical analysis and through characterization of the source of the substance about sediment from Core NT1 among the lutaceous area in Central South Yellow Sea. The research finds out that the sediment in Core NT1 mainly comes from Yangtze River and Yellow River, the sediment between 0-7.70 m in upper Core NT1 mainly belongs to Yangtze River source; the sediments between 7.70-16.60 m and 42.0-54.80 m in middle Core NT1 are mainly from Yellow River, the 26 m thick sediment interlayer in it mainly comes from Yangtze River; and the sediment between 54.80-69.76 m in the bottom of Core NT1 is mainly from Yangtze River. The results demonstrate that Yangtze River has been playing a main role in the lutaceous area in the Central South Yellow Sea since early Late Pleistocene, and Yellow River started to influence the continental sedimentation of Yellow Sea from early Warm Glaciation of late Late Pleistocene.
基金the Department of Science and Technology (DST), Government of India for financial support vide PURSE (Phase-Ⅱ) program (No. F4/SC/20/15)University Grants Commission (UGC), New Delhi for the scholarship of the first author
文摘The Palaeo–Mesoproterozoic Tadapatri formation of the Cuddapah basin is comprised of clastic sedimentary rocks with minor carbonates and mafic–ultramafic sill bodies. Geochemistry of the shale is used to study the provenance, paleoweathering and paleoredox conditions of this Tadpatri formation in order to better understand the development of the Cuddapah basin during Palaeo–Mesoproterozoic time. The higher CIA(average 74.39), PIA(average 85.94) and CIW(average 87.59) values of the Tadpatri shales suggest intensely weathered sources.Higher Al2_ O_3/TiO_2(average 30.78) and LREE/HREE ratio(average 8.80) with negative europium anomaly indicate derivation of the clastic sediments from a felsic source rock. The geochemical parameters like U, U/Th, Cu/Zn,Ni/Co, V/Cr ratios reveal that the Tadpatri shales are mainly deposited in an oxic condition.
文摘Petrographical and geochemical methods were combined to investigate the provenance, geodynamic and weathering history of the Shurijeh sandstones, Kopet-Dagh Basin. The point-counting method and XRF technique are used for modal and geochemical analyses. Based on petrographical examinations, it seems that the Shurijeh sandstones are mainly deposited in the craton interior and recycled orogen belts. In addition to petrographical investigation, geochemical analyses （major oxides and trace elements） of Late Jurassic-Early Cretaceous rocks reveal that the sedimentation processes are performed in a passive continental margin. Such interpretation is supported with geodynamic and paleogeographical studies of the Kopeh-Dagh basin during this time. The geochemical investigations suggested that the composition of probable source rocks mostly was acidic-intermediate with minor mafic igneous rocks. Based on the above, Paleo-Tethys remnants and their collision-related granitoids, in the south and west of Mashhad, may have been the source area for these rocks. CIA values, which range from 63.8 to 94.9 in samples, are suggesting a moderate to relatively high degree of alteration （weathering） in the source area. Therefore, petrographical and paleogeographical studies of siliciclastic rocks can be used for the provenance, tectonic setting and paleoweathering studies in the source area.
基金the project (PPP) PG003-2013A of the University of Malaya, Kuala Lumpur, Malaysia in carrying out this research work is gratefully acknowledgedthe project RP002C-13AFR of the University of Malaya is also gratefully acknowledged
文摘Tertiary sandstones collected from southwest Sarawak, Malaysia, were analyzed to decipher their provenance, weathering, and tectonic setting. The studied sandstones have a sublitharenite composition and are dominantly composed quartz with little mica and feldspar, and a small amount of volcanic fragments. These sand- stones were generally derived from quartz-rich recycled orogenic sources. They have relatively high SiO2 content with low Na20, CaO, MnO, and MgO contents. Values of Chemical Index of Alteration （CIA） of these rock samples vary from 71 to 93, with an average of 81, implying intense chemical alteration during weathering. A felsic igneous source is suggested by a low concentration of TiO2 com- pared to CIA, enrichment of Light Rare Earth Elements, depletion of Heavy Rare Earth Elements, and negative Eu anomalies. A felsic origin is further supported by a Eu/Eu＊ range of 0.65-0.85 and high Th/Sc, La/Sc, La/Co, and Th/ Co ratios. This work presents the first reported geochemical data of Tertiary sandstones of the Sarawak Basin. These data led us to conclude that the sandstones were dislodged from recycled orogenic sources and deposited in a slowly subsiding rifted basin in a passive continental tectonic setting.
基金The National Natural Science Foundation of China(NSFC)under contract Nos 41376079 and 41276060the Marine Geology Survey Project under contract Nos GZH200900501 and GZH201400204the Foundation of the Shandong Provincial Key Laboratory of Marine Ecology and Environment&Disaster Prevention under contract No.201304
文摘The sedimentary record of mud areas is an important carrier of information on the Holocene evolution of marine environments. Based on fine interpretations of the shallow stratigraphic section data, a small mud deposit area has been found in the southern coastal waters off Shandong Peninsula. This mud area is mainly distributed in coastal waters north of Laoshantou to the vicinity of Rushan Estuary. Overall, it is parallel to the coastline and spreads in a banded pattern, gradually thinning from offshore to the sea. The isopach map of depth distribution is parallel with the shoreline, and the depocenter lies in coastal waters of the Aoshan Bay where the maximum thickness is up to 22.5 m. Accelerator mass spectrometry（AMS） ^（14）C dating shows that the mud area was formed in the Holocene. The test data of surface sediments from the mud area, including particle size, mineral characteristics, and rare earth element contents, are used in comparisons with the composition of materials from the major surrounding medium and small rivers flowing into the sea and the Huanghe（Yellow） River. In this paper, the sedimentary characteristics and provenance of the mud deposit area are discussed. The results show that the formation of this mud area resulted from the joint action of the Huanghe River and surrounding rivers flowing into the sea.
文摘The geochemical composition of sandstones in the sedimentary basin is controlled mainly by the tectonic setting of the provenance, and it is therefore possible to reveal the tectonic setting of the provenance and the nature of source rocks in terms of the geochemical composition of sandstones. The major elements, rare\|earth elements and trace elements of the Mesozoic\|Cenozoic sandstones in the Lanping Basin are studied in this paper, revealing that the tectonic settings of the provenance for Mesozoic\|Cenozoic sedimentary rocks in the Lanping Basin belong to a passive continental margin and a continental island arc. Combined with the data on sedimentary facies and palaeogeography, it is referred that the eastern part of the basin is located mainly at the tectonic setting of the passive continental margin before Mesozoic, whereas the western part may be represented by a continental island arc. This is compatible with the regional geology data. The protoliths of sedimentary rocks should be derived from the upper continental crust, and are composed mainly of felsic rocks, mixed with some andesitic rocks and old sediment components. Therefore, the Lanping Mesozoic\|Cenozoic Basin is a typical continental\|type basin. This provides strong geochemical evidence for the evolution of the paleo\|Tethys and the basin\|range transition.
文摘Generalized the use of neutron activation analysis(NAA)in the investigations of unique processes occurring in early stages of formations and evolution of bodies in solar system Out of them the formation of chondrules,emergence of ultra refractory inclusions in carbonaceous chondrites,formation of metallic and silicate phases of iron and stone meteorites,and formation of iron meteorites of different chemical groups Changes in regolite and lunar rock contents,differentiation in the upper mantle matter, identification of earthly meteoritic craters,transportation of cosmic(meteoritic)materials on to the Earth, investigations of unique events like Tunguska fall of the year 1908 and also ore formation studies and processes taking place on geochemical barrier type river-sea,ocean-atmosphere and so on Prospectives of NAA are pointed out
文摘In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of the rocks.Petrographic and geochemical analyses of major and minor elements of the samples were used for this purpose.This Formation is composed of three major facies including conglomerate,fine sandstone,and mudstone.The source formations which were recognized to be supplying sediments to the Cheleken Formation depositional basin include Lalun,Ziarat,Tizkuh,Dalichai,and Cretaceous formations.According to the discrimination diagrams and other ratios for minor elements of the studied samples,a complex of felsic to intermediate igneous rocks in the source region was deciphered.The depositional environment of the rocks experienced humid and semi-arid climatic conditions during deposition.According to the CIW index,the samples underwent a high level of weathering(97%)in the source area or during transportation.From a tectonic point of view,the Cheleken Formation was deposited in an Active Continental Margin setting.
基金generously sponsored by the German Federal Ministry of Education and Researchsupported by the Alexander von Humboldt Foundation。
文摘This study was conducted on the Ngaoundaba Crater Lake sediments to infer provenance,weathering conditions,organic matter accumulation,and trace metal concentrations.Ngaoundaba Lake sediments were collected using a manual core sampler at 5 to 8 m water depth.Two sediment cores from the littoral and center of the lake were analyzed for grain size distribution,water content(WC),organic matter content,mineralogy,and major and trace element concentrations.The Ngaoundaba sediments were classified as silt and sandy silt.Sediments show high content in organic matter,which is more to the littoral than to the center of the lake,varying from 14.6%to 24%and21.2%to 40.8%,respectively.The grain surface features identified by Scanning Electron Microscopy(SEM)show both chemical and mechanical microtextures with subrounded to angular shape suggesting both proximal and distal sources.The lake sediments are composed of quartz,kaolinite,and hematite,with low amounts of feldspars,rutile,calcite,illite,and ilmenite.Weathering indices such as the chemical index of alteration(CIA),chemical index of weathering(CIW),and index of compositional variability(ICV)indicate moderate to intense chemical weathering in the source area and immature to mature sediments.The geochemical composition indicates that the sediments were derived from felsic to intermediate igneous rocks,such as granitoids,and mafic alkali lavas like basanites.The environmental risk assessment of trace metals obtained by enrichment factor(EF)and geo-accumulation index(I-geo)shows low contamination of the lake sediments.
