Geochemistry of the Paleocene Clastic Rocks From the Southwestern Jianghan Basin, Central China Reveal Their Provenance, Tectonic Setting, and Palaeoenvironment

Abstract This paper intends to learn about the provenance, tectonic setting and paleoenvironment of the Paleocene Shashi Formation in the southern Jianghan Basin by the bulk-rock geochemistry. The K2O/Al2O3 and SiO2/Al2O3 ratios indicate that the major proportion of samples are litharenite. The chondrite-normalized REE distribution pattern of the Shashi Formation’s mudstones are characterized by enriched LREE and flat HREE similar to those of UC with negative Eu anomalies. Combined with the geochemical element ratio discriminant diagram, such as Al2O3-TiO2, Zr-TiO2, La/Sc-Co/Th, and Hf-La/Th, so on, these samples were sourced from mixed felsic/basic rock. Moreover, the discriminant diagrams of K2O/Na2O-SiO2/Al2O3, La-Th-Sc, and Th-Co-Zr/10 suggest that the samples were formed under the tectonic settings of active continental margin and continental island arc. The values of CIA, CIW, PIA, ICV, Zr/Sc-Th/Sc, and ternary diagrams of A-(CN)-K and Al2O3-Zr-TiO2 indicate that weathering in the source area was weak and source rocks have not been reformed by depositional recirculation and hydraulic sorting. And the palaeoenvironmental indicators of C-value, Ni/Co, V/Cr, V/(V+Ni) and Sr/Cu, Ga/Rb indicate that the climate was cool and arid during the evaporite deposition period in the southern Jianghan Basin, and the water was in the condition of oxidation.

Download Full-text

Tectonic setting of the middle-late cambrian deposits of isl. Bolshevik and isl. Troynoy (Russian Arctic): a case of clastic rocks from metaterrigeneous complexes

Геотектоника ◽

10.31857/s0016-853x2019665-77 ◽

2019 ◽

pp. 65-77

Author(s):

P. A. Fokin ◽

V. O. Yapaskurt ◽

A. M. Nikishin

Keyword(s):

Tectonic Setting ◽

Source Area ◽

Size Composition ◽

Orogenic Belt ◽

Clastic Rocks ◽

The North ◽

Late Cambrian ◽

Coastal Marine ◽

Tectonic Settings ◽

Severnaya Zemlya

Abstract The new data on the tectonic settings and sedimentational circumstances of the Middle-Late Cambrian deposits of the southern part of the North Kara terrane, presented in our research, the data induced from the studies of clastic rocks in the basement metaterrigeneous complexes of Troynoy island (archipelago Izvestia CEC) and the northern part of Bolshevik island (archipelago Severnaya Zemlya). The sandstones of both regions are similar in the lithic wacke composition and contain the same groups of rocks fragments. Clastic zircons and Cr-spinels from sandstones of both regions have the same Zr/Hf and TiO2/Al2O3 ratios, respectively. The similarity of even-aged sediments from both regions can be explained by their accumulation due to the demolition of detrital material from a single source eroded area, which is a segment of the accretionary uplift of the Timan‒Severnaya Zemlya orogenic belt, with the newly formed continental Neoproterozoic-Cambrian crust. The low and medium-grade metamorphosed terrigeneous complexes dominated in the structure of the source area. Presence of volcanic and intrusive complexes in the source area is marked by clastic Cr-spinels with geochemical signatures of volcanic arc and suprasubductional ophiolites origin. By the beginning of the Ordovician, the Middle Late Cambrian sediments were also crushed, metamorphosed, and included in the structure of the Timan‒ Severnaya Zemlya orogenic belt. Peculiarities of petrographic and grain-size composition and sorting of the sandstones from the north of Bolshevik island are more typical for the sediments of gravity turbidite flows, in deep or relatively deep water conditions. The deposits of Troynoy island could be formed at shallow and coastal-marine environments.

Download Full-text

Early Cretaceous redbeds from the Minle Basin, Hexi Corridor, northwest China: Mineralogy and geochemistry implications for paleoweathering, provenance, and tectonic settings

Interpretation ◽

10.1190/int-2018-0120.1 ◽

2019 ◽

Vol 7 (2) ◽

pp. T525-T545

Author(s):

Yaxiong Sun ◽

Wenlong Ding ◽

Yang Gu ◽

Gang Zhao ◽

Siyu Shi ◽

...

Keyword(s):

Early Cretaceous ◽

Lower Cretaceous ◽

Chemical Weathering ◽

Tectonic Setting ◽

Active Continental Margin ◽

Northwest China ◽

Hexi Corridor ◽

Sediment Supply ◽

Compositional Variation ◽

Tectonic Settings

Redbeds with a large thickness in the lower Cretaceous record abundant geologic information in the Minle Basin. We have conducted the paleoweathering conditions, provenance, and tectonic settings based on mineralogy and geochemistry. Our results indicate that mudstone samples are characterized by abundant illite with negligible amounts of K-feldspars and analcime. The lower part of the lower Cretaceous is rich in quartz, whereas the upper part is dominated by dolomite and analcime. We suggest that this is caused by the decreasing input of the clastic influx during the middle-late early Cretaceous. High index of compositional variation values (average 1.33) indicate first-cycle sediment supply, suggesting an overall compositional immaturity and short-distance transportation. These characteristics are consistent with an active regional extension tectonic setting. The [Formula: see text] system ([Formula: see text];[Formula: see text];[Formula: see text]) and Th/U versus Th consistently reveal that the lower Cretaceous experienced a positive gradient in chemical weathering from young to old formations. Although the patterns of trace elements in three formations of the lower Cretaceous are different, those of the rare earth elements (REEs) tend to be consistent. The significant enrichment of light REEs, heavy REEs fractionation, and distinctive negative Eu anomalies suggest derivation from an old, upper continental crust composed of predominantly felsic sediments. This interpretation is supported by several discrimination diagrams such as titanium dioxide-nickel ([Formula: see text]), which shows the characteristics of immature recycled sediments. A few sensitive elements, ratios, and normalized REE patterns indicate a provenance of an active continental margin and a continental island arc (CIA). The La-Th-Sc, Th-Co-Zr/10, and Th-Sc-Zr/10 discrimination plots further confirm the CIA signature. Thus, we conclude that the early Cretaceous redbeds in the Minle Basin, Hexi Corridor, were deposited in a dustpan-shaped half-graben basin in a CIA setting when northwest China was influenced by intense regional extension.

Download Full-text

Petrography and geochemistry of the siliciclastic Araba Formation (Cambrian), east Sinai, Egypt: implications for provenance, tectonic setting and source weathering

Geological Magazine ◽

10.1017/s0016756815000771 ◽

2015 ◽

Vol 154 (1) ◽

pp. 1-23 ◽

Cited By ~ 34

Author(s):

HOSSAM A. TAWFIK ◽

IBRAHIM M. GHANDOUR ◽

WATARU MAEJIMA ◽

JOHN S. ARMSTRONG-ALTRIN ◽

ABDEL-MONEM T. ABDEL-HAMEED

Keyword(s):

Tectonic Setting ◽

Source Area ◽

Xrd Analysis ◽

Climatic Conditions ◽

Source Rocks ◽

Northern Margin ◽

Rock Fragments ◽

Geochemical Parameters ◽

Clastic Sediments ◽

Chemical Index

AbstractCombined petrographic and geochemical methods are utilized to investigate the provenance, tectonic setting, palaeo-weathering and climatic conditions of the Cambrian Araba clastic sediments of NE Egypt. The ~ 60 m thick Araba Formation consists predominantly of sandstone and mudstone interbedded with conglomerate. Petrographically the Araba sandstones are mostly sub-mature and classified as subarkoses with an average framework composition of Q80F14L6. The framework components are dominated by monocrystalline quartz with subordinate K-feldspar, together with volcanic and granitic rock fragments. XRD analysis demonstrated that clay minerals comprise mixed-layer illite/smectite (I/S), illite and smectite, with minor kaolinite. Diagenetic features of the sandstone include mechanical infiltration of clay, mechanical and chemical compaction, cementation, dissolution and replacement of feldspars by carbonate cements and clays. The modal composition and geochemical parameters (e.g. Cr/V, Y/Ni, Th/Co and Cr/Th ratios) of the sandstones and mudstones indicate that they were derived from felsic source rocks, probably from the crystalline basement of the northern fringe of the Arabian–Nubian Shield. The study reveals a collisional tectonic setting for the sediments of the Araba Formation. Palaeo-weathering indices such as the chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) of the clastic sediments suggest that the source area was moderately chemically weathered. On the northern margin of Gondwana, early Palaeozoic weathering occurred under fluctuating climatic conditions.

Download Full-text

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

Open Geosciences ◽

10.1515/geo-2020-0260 ◽

2021 ◽

Vol 13 (1) ◽

pp. 1187-1225

Author(s):

Temitope Love Baiyegunhi ◽

Kuiwu Liu ◽

Oswald Gwavava ◽

Christopher Baiyegunhi ◽

Maropene Rapholo

Keyword(s):

South Africa ◽

Chemical Weathering ◽

Tectonic Setting ◽

Active Continental Margin ◽

Source Area ◽

Major And Trace Elements ◽

Rift System ◽

Moderate Degree ◽

East African Rift System ◽

Major Oxide

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.

Download Full-text

Relationships between Alluvial Facies/Depositional Environments, Detrital Zircon U-Pb Geochronology, and Bulk-Rock Geochemistry in the Cretaceous Neungju Basin (Southwest Korea)

Minerals ◽

10.3390/min10111023 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1023

Author(s):

Hyojong Lee ◽

Min Gyu Kwon ◽

Seungwon Shin ◽

Hyeongseong Cho ◽

Jong-Sun Kim ◽

...

Keyword(s):

Continental Margin ◽

Detrital Zircon ◽

Tectonic Setting ◽

Active Continental Margin ◽

Depositional Environments ◽

Source Rocks ◽

Bulk Rock ◽

Zircon Age ◽

Margin Setting ◽

Weathering Intensity

Zircon U-Pb geochronology and bulk-rock geochemistry analyses were carried out to investigate their relationship with depositional environments of the non-marine Neungju Basin sediments in South Korea. The Neungju Basin was formed in an active continental margin setting during the Late Cretaceous with associated volcanism. Detrital zircon age distributions of the Neungju Basin reveal that the source rocks surrounding the basin supplied sediments into the basin from all directions, making different zircon age populations according to the depositional environments. Mudstone geochemistry with support of detrital zircon U-Pb age data reveals how the heterogeneity affects the geochemical characteristics of tectonic setting and weathering intensity. The sediments in the proximal (alluvial fan to sandflat) and distal (playa lake) environments differ compositionally because sediment mixing occurred exclusively in the distal environment. The proximal deposits show a passive margin signature, reflecting their derivation from the adjacent metamorphic and granitic basement rocks. The distal deposits properly indicate an active continental margin setting due to the additional supply of reworked volcaniclastic sediments. The proximal deposits indicate a minor degree of chemical weathering corresponding to fossil and sedimentological records of the basin, whereas the distal deposits show lower weathering intensity by reworking of unaltered volcaniclastic detritus from unstable volcanic and volcaniclastic terranes. Overall, this study highlights that compositional data obtained from a specific location and depositional environments may not describe the overall characteristic of the basin.

Download Full-text

Geochemistry of Recent Brahmaputra River Sediments: Provenance, Tectonics, Source Area Weathering and Depositional Environment

Minerals ◽

10.3390/min10090813 ◽

2020 ◽

Vol 10 (9) ◽

pp. 813

Author(s):

Md Aminur Rahman ◽

Sudeb Chandra Das ◽

Mark I. Pownceby ◽

James Tardio ◽

Md Sha Alam ◽

...

Keyword(s):

Rare Earth ◽

Rare Earth Element ◽

Chemical Weathering ◽

Earth Element ◽

Tectonic Setting ◽

River Sediments ◽

Source Area ◽

Source Rocks ◽

Heavy Minerals ◽

Brahmaputra River

Sediments from stable sand bars along a 40 km section of the Brahmaputra River in northern Bangladesh were analyzed for their major, trace and rare earth element contents to determine their provenance, compositional maturity, source area weathering and tectonic setting. Geochemically, the sediments were classified as litharenites and the Index of Compositional Variability (ICV) varied between 1.4 and 2.0, indicating low compositional and mineralogical maturity. A high mean SiO2 concentration (72.9 wt.%) and low Al2O3 (11.1 wt.%) were consistent with a low abundance of shale and clay components. The depletion of the oxide components Na2O, CaO and K2O relative to average upper crustal compositions (UCC) reflected loss of feldspar during chemical weathering in the source region. Average TiO2 values for most samples were higher than average crustal levels, consistent with the northern section of the Brahmaputra River being a potential resource for valuable Fe-Ti oxide heavy minerals. Major and trace element ratios indicated the sediments represented erosional products from typical felsic upper continental crustal materials with contamination (30%–40%) from more intermediate/mafic compositions. The rare earth element patterns showed negative Eu anomalies (0.57–0.71), indicating they were derived mainly from fractionated felsic rocks. Resemblance of the sediment compositions to mean compositions from Higher Himalaya crystalline rocks pointed to these being potential source rocks but with components from a mafic source also present. Major element chemistries and low to intermediate weathering indices for all sediments indicated a lack of substantial chemical weathering. Evidence from tectonic discrimination diagrams suggested the Brahmaputra River sediments were derived from rock types that formed in a transitional tectonic setting ranging from an ancient passive margin to an active continental margin. Deposition occurred under cool to semi-arid climatic conditions in an oxic environment.

Download Full-text

Geochemistry and provenance of metasedimentary rocks from the Archean Golden Pond sequence (Casa Berardi mining district, Abitibi subprovince)

Canadian Journal of Earth Sciences ◽

10.1139/e96-051 ◽

1996 ◽

Vol 33 (5) ◽

pp. 676-690 ◽

Cited By ~ 10

Author(s):

M. R. Flèche ◽

G. Camiré

Keyword(s):

Chemical Weathering ◽

Volcanic Rocks ◽

Source Area ◽

Source Rocks ◽

Iron Formation ◽

Mining District ◽

Metasedimentary Rocks ◽

Clastic Rocks ◽

The North ◽

Volcanic Source

The Archean Golden Pond sequence is made up of deformed and metamorphosed conglomerates, greywackes, and mafic volcanic rocks, and is overlain by ferrugineous metasedimentary rocks of the North iron formation. The clastic rocks were derived mainly from a volcanic source that had undergone weak chemical weathering. Their source area was dominated by the presence of 60–80% high-Al2O3 felsic volcanics having strongly fractionated [La/Sm]N (= 3.7 ± 0.3) and very low Ta/Th ratios (= 0.09 ± 0.02), with lesser proportions of basaltic (10–30%) and ultramafic volcanic rocks (1–10%). The ferrugineous metasedimentary rocks can be modelled by mixing 20–40% siliciclastic material, of the composition of the average Golden Pond greywacke, with an Fe- and Si-rich precipitate (molecular Fe/Si = 0.6 ± 0.2). The high-Al2O3 felsic source rocks were most likely produced by subduction processes within an oceanic arc environment, but the mafic and ultramafic volcanic rocks were derived by different processes from an asthenospheric mantle source, possibly in an oceanic rift environment. Therefore, it is suggested that the ultramafic, mafic, and felsic volcanic rocks were brought to the same erosional level by dissection of the arc system and rapid exhumation of the felsic arc lithologies and the deeper ocean floor. Intrabasinal hydrothermal activity associated with contemporaneous mafic volcanism and (or) graben development may have also been responsible for the local production of the Fe-rich precipitates of the North iron formation.

Download Full-text

Reassessment of the Mesozoic metasedimentary rocks and tectonic setting of Taiwan and the adjacent continental margin of eastern Asia

Geological Magazine ◽

10.1017/s0016756816000741 ◽

2016 ◽

Vol 154 (5) ◽

pp. 1127-1154 ◽

Cited By ~ 2

Author(s):

YU WANG ◽

CHIN-HO TSAI ◽

LIYUN ZHOU ◽

YAN QIU ◽

GUIHUA SUN

Keyword(s):

Continental Margin ◽

Tectonic Setting ◽

Active Continental Margin ◽

Crystalline Basement ◽

Detrital Zircons ◽

Source Rocks ◽

Metamorphic Belt ◽

Late Mesozoic ◽

Sedimentary Sequences ◽

Se China

AbstractIt remains unclear whether a crystalline basement exists in SE China (including Taiwan), whether the formation of the Tananao metamorphic belt in Taiwan was linked to subduction of the Palaeo-Pacific Plate, and whether the source rocks of the sedimentary sequences in the metamorphic belts are late Mesozoic or Palaeozoic in age. Field investigations and zircon age data in the present study indicate that there is no pre-Palaeozoic gneiss (crystalline basement) in Taiwan (although orthogneisses were produced during deformation and metamorphism of Mesozoic granites), and investigations of the metasediments show that the sedimentary sequences in the Tailuko and Yuli belts are similar. Moreover, LA-ICP-MS dating of detrital zircons from the Pingtan–Dongshan belt in Fujian Province yields a cluster of 206Pb–238U ages at ~ 210–190 Ma, and the Tailuko and Yuli belts in Taiwan have similar clusters of detrital zircon ages at 200 Ma, 160 Ma, 120 Ma and 110 Ma, as well as a later overprinting caused by arc–continent collision. The cathodoluminescence images and trace-element characteristics of the zircons show that they were originally magmatic in origin. This finding, combined with the Hf isotope data, indicates that the sources of sediments in the Tananao belt (Tailuko and Yuli belts) were relatively close to an active continental margin, and that both the Tailuko and Yuli belts have similar sedimentary sources. From the margin of the Chinese mainland to Taiwan, the metasediments seem to represent a continuous sequence of deposits ranging in age from Jurassic to Cretaceous, but with the sediments becoming progressively younger towards the east. It can be inferred that the sediments in the Tailuko and Yuli belts were continental-shelf sequences with sources in SE China.

Download Full-text

Petrographic and geochemical interpretations of source provenance and tectonic setting of the Lokoja Sandstone, Bida Basin, Nigeria

International Journal of Advanced Geosciences ◽

10.14419/ijag.v8i2.31196 ◽

2020 ◽

Vol 8 (2) ◽

pp. 279

Author(s):

G. U. Ozulu ◽

A. U. Okoro ◽

V. O. Ndubueze

Keyword(s):

Trace Elements ◽

Inductively Coupled Plasma ◽

Tectonic Setting ◽

Source Area ◽

Climatic Conditions ◽

Source Rocks ◽

Heavy Minerals ◽

Petrographic Analysis ◽

Moderate Degree ◽

X Ray

The petrography and geochemistry of major and trace elements distribution pattern for the Lokoja Sandstones, Southern Bida Basin, Nigeria; were used to interpret their provenance, weathering conditions and paleotectonic setting. A total of seven (7) representative sandstone samples were selected for petrographic, heavy minerals and inorganic geochemical analyses; that is X- ray diffraction (XRD), X-ray fluorescence (XRF) and Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Results of the petrographic analysis showed 52.14 % quartz, 39.29 % feldspar, 2.00 % rock fragments, 5.14 % matrix and cement fraction as well as 1.43 % unfilled voids. Results of major elements and oxides suggests intermediate to felsic source rocks while the dominance of Na-rich feldspar to the k-feldspar and high value of Fe2O3+MgO shows contribution from ferromagnesian minerals of mafic igneous source provenance and oceanic island arc region. Average concentrations of designated trace elements in the studied sandstones are low in concentrations. The lower concentrations of Cr, Co, and Ni and higher concentrations of Zr, Ba, and Sr suggest a felsic progenitor rock. But significantly high values of Ni (7.02 ppm), La/Co (7.99), and Ni/Co (3.28) as well as the low concentration value of Y, (3.23 ppm) suggests contributions from mafic source rocks. Low average ratios for La/Co, Th/Co, Th/Sc, Ni/Co, Cr/Ni, Cr/Sc, Cr/Th, Ni/Co, Cr/Ni, Cr/Th, Cr/Sc, Th/Sc, La/Co and Th/Co also suggest a felsic source provenance. An average CIA value of 78.04% is indicative of an intense recycling in the source area while an average MIA value of 56.13% suggests a moderate degree of weathering. The high clay matrix and feldspar content have been used to classify the sandstones as feldspathic greywackes deposited in dry arid climatic conditions under a basement uplifted tectonic setting.

Download Full-text

Abstract title; Geology and geochemical characteristics of coal-bearing source rocks in Nariin sukhait deposit, southern Mongolia

10.5194/egusphere-egu2020-17731 ◽

2020 ◽

Author(s):

Norov Baigalmaa ◽

Takeyuki Ogata ◽

Luvsanchultem Jargal ◽

Bat-Orshih Erdenetsogt ◽

Jamsran Erdenebayar

Keyword(s):

Chemical Weathering ◽

Pore Space ◽

Sedimentary Environment ◽

Active Continental Margin ◽

Source Area ◽

Source Rocks ◽

Intergranular Porosity ◽

Epma Data ◽

Geological Features ◽

East West

The Nariin Sukhait mine is located in the southwest of Umnugobi province 50 kilometers from Mongolia's border with China at Shivee Khuren within the Nariin Sukhait deposit, which has relatively complex geological features. The most prominent feature relating to the Nariin Sukhait coal deposit is the arcuate, east-west trending Nariin Sukhait fault. The coal-bearing section, interpreted to be middle Jurassic in age, is exposed primarily in a window adjacent to this fault.The chemical composition of whole indicates (variable composition, values of the ratio Th/U > 3.8-4.2, values Th/Sc 0.3-0.8, values LaN/YbN > 5 and values Eu/Eu* 0.6-0.9) indicates components derived from the active continental margin type. The low CIA values (50&#8211;60) indicate the absence or poor chemical weathering in the source area.SEM-CL-imaging of sandstone quartz from Nariin sukhait show three types of quartz: &#160;early Q1 cementation has gray to slightly grey luminescences, postdated compaction, and reduced intergranular porosity associated with illite formed during eogenesis. Q2 is characterized by dark luminescence overgrowths and is more voluminous in the thinly bedded sandstones than in the thickly bedded sandstones filling most of the remaining pore space during mesogenesis. Q3 was formed during the early telogenesis stage fully cementing the sandstones and the fractures were filled by hydrothermal chlorite and sulfides. Significant amounts of trace elements Al, Ti, Ca, K and Fe has been detected in quartz overgrowths. Al varies consistently between each cement with averages of 1324, 1523, and 1352 ppm for the Q1, Q2, and Q3 generations, respectively.The geochemical, SEM-CL imaging and EPMA data results suggest a relatively igneous source, whit felsic composition. The sedimentary environment of the sandstone and argillite of these sedimentary rocks was the poor chemical weathering in the source area.

Download Full-text