scholarly journals Sedimentary environment and provenance of sandstones from the Qadir member in the Nayband Formation, Tabas block, east-central Iran

2021 ◽  
Vol 73 (1) ◽  
pp. A140920
Author(s):  
Ehsan Zamaniyan ◽  
Mohammad Khanehbad ◽  
Reza Moussavi-Harami ◽  
Asadollah Mahboubi
Keyword(s):  
Continental Margin ◽  
Chemical Weathering ◽  
Sedimentary Environment ◽  
Active Continental Margin ◽  
Central Iran ◽  
Geochemical Data ◽  
Delta Front ◽  
Field Evidence ◽  
Nayband Formation ◽  
The Impact

Qadir Member of Nayband Formation, located in East of Central Iran, has developed to a great extent. Investigation of the lithofacies and sedimentary environment, resulted in identification of the deltaic and marine deposits. Based on field evidence and facies features, Qadir Member consists of two lithofacies, including carbonate and siliciclastic facies. The siliciclastic facies were identified as having four sandstone facies including Sr, Sh, Sp, St, three fine-grained lithofacies, including FI, Fm, Fl (Sr) / Sr (FI) and one coal facies. Also, regarding the field, laboratory studies, and identification of lithofacies, the coastal plain, deltaic (including deltaic plain, proximal delta front, distal delta front, and prodelta) and open marine environments were identified for Qadir Member which is is under the impact of tidal currents. The chemical weathering index (71%) indicated semi-arid to semi-humid conditions and plotting the geochemical data showed the provenance of re-cycling and active continental margin and because of Chemical Index of Alteration, the weathering rate was found to be rather medium to high. The geochemical diagrams also showed a probable source of the intermediate igneous and sedimentary rocks. The active continental margin conditions for this deposit could suggest the Neotethys subduction under Iran’s plate and volcanic activity at the end of Triassic, which coincided with the early Cimmerian orogeny in Alborz and Central East Iranian Microcontinent.

scholarly journals Neoproterozoic Nafun Group Sediments from Oman Affected by an Active Continental Margin

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 511
Author(s):  
Liang Yue ◽  
Veerle Vandeginste
Keyword(s):  
Continental Margin ◽  
Water Oxidation ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Trace Element Analysis ◽  
Deep Ocean ◽  
Geochemical Data ◽  
Ocean Water ◽  
Element Analysis ◽  
Deep Ocean Water

The Neoproterozoic era is a time of major environmental change in Earth history. The Ediacaran period (635–541 Ma), the uppermost division of Precambrian time, is characterized by the remarkable Shuram excursion (largest C isotope negative excursion), a deep ocean water oxidation event, and Ediacaran biota. The Nafun Group of Oman provides a well-preserved and mostly continuous section of an Ediacaran succession. Based on geochemical data from the Nafun Group, the Shuram excursion (SE) and deep ocean oxidation hypotheses were proposed. Now, we sampled this section at high stratigraphic resolution, and present here the petrographical and geochemical analysis of the Khufai, Shuram and Buah Formations. The major and trace element analysis of shales from the Shuram Formation indicates that northern Oman was an active continental margin environment in Neoproterozoic times. The provenance of the Shuram Formation was primarily mafic and intermediate igneous rocks. With the unsteady tectonic setting, the development of the Nafun Group was influenced by hydrothermal supply and volcaniclastic input. Based on the V/Cr and U/Th ratio of the samples from the Nafun Group, our study reveals the transition of the ocean water redox environment, which is connected to the rise and fall of the Ediacaran biota. Our study constrains the tectonic setting of northern Oman and the petrography and geochemical data from the Nafun Group for the hydrothermal and volcaniclastic supply. Thus, our study acknowledges more factors for the explanation of the Ediacaran conundrums.

Distribution Characteristics of Nanopores and Discriminant Characteristics of Sedimentary Environment of the Longmaxi Formation in the Southern Sichuan Basin

2021 ◽  
Vol 21 (1) ◽  
pp. 431-437
Author(s):  
Xin Tang ◽  
Yuanchen Guo ◽  
Tingqiang Zhou ◽  
Sen Guo
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Continental Margin ◽  
Sichuan Basin ◽  
Tectonic Setting ◽  
Sedimentary Environment ◽  
Active Continental Margin ◽  
Vertical Direction ◽  
Simulation Method ◽  
Longmaxi Formation

Shale contains a large number of nanopores. The nanopores control the reservoir structure. The formation of nanopores in shale is closely related to the sedimentary environment. The palaeosedimentary structural background determines the provenance and sedimentary diagenesis of mud shale during shale deposition, refines the palaeo-shale and palaeo-sedimentary-tectonic environments of the Longmaxi Formation in the southern Sichuan Basin by elemental geochemical means, and determines the palaeo-deposition of the Longmaxi Formation. The tectonic setting and a numerical simulation method are used to explore the sedimentary tectonic evolution characteristics of the Longmaxi Formation. The results show that the parent rock of the Longmaxi Formation is relatively enriched with light rare earth elements, and the distribution of heavy rare earth elements is relatively stable. The vertical direction shows a trend of increasing from the bottom of the formation to the top of the formation, showing a mixed genesis; the tectonic setting is a passive continental margin, and the active continental margin is the main margin.

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

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

<p>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.</p><p>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 (50–60) indicate the absence or poor chemical weathering in the source area.</p><p>SEM-CL-imaging of sandstone quartz from Nariin sukhait show three types of quartz:  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.</p><p>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.</p>

scholarly journals Geochemistry, Depositional and Tectonic setting of the Barail Group of the Indo-Myanmar Ranges

2021 ◽  
Vol 38 (1) ◽  
pp. 13-22
Author(s):  
Salam Ranjeeta Devi
Keyword(s):  
Continental Margin ◽  
Chemical Weathering ◽  
Depositional Environment ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Source Rocks ◽  
Humid Climate ◽  
Geochemical Study ◽  
High Degree ◽  
Semi Arid

The present paper deals with the study of the depositional environment and tectonic setting during the sedimentation of the Barail Group of rocks of the Indo-Myanmar Ranges (IMR). The Barail Group (Oligocene) consist of sandstone intercalated with shale and siltstone. Geochemical study suggests low to high degree of chemical weathering. ICV vs. CIA, Al2O3 vs. TiO2 diagrams indicate that the sediments were derived from the multiple source rocks dominantly of mafic composition. Arid to semi-arid/semi-humid climate prevailed during the deposition of the Barail Group sediments. Sedimentation occurred in a tectonic setting of overlap of passive to active continental margin under marine environment.

scholarly journals The Chemical Composition and Surface Texture of Transparent Heavy Minerals from Core LQ24 in the Changjiang Delta

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 454 ◽  
Author(s):  
Yue ◽  
Yue ◽  
Panwar ◽  
Zhang ◽  
Jin
Keyword(s):  
Grain Size ◽  
Surface Texture ◽  
Chemical Weathering ◽  
Environmental Changes ◽  
Sedimentary Environment ◽  
Heavy Minerals ◽  
Sediment Provenance ◽  
Geochemical Data ◽  
Geochemical Composition ◽  
Changjiang Delta

The assessment of textural and compositional modifications of detrital sediments is required to reconstruct past source to sink dynamics. The Changjiang Delta is an ideal location to study the sedimentary environment from the Pliocene to Quaternary transition. In the present study, we aim to decipher the response of heavy minerals to mechanical wear and chemical weathering since the Pliocene. With the application of a scanning electron microscope and an electron probe, the geochemistry and surface texture of different heavy minerals (amphibole, epidote, and tourmaline groups) with grain-size fractions of 32–63 µm and 63–125 µm were studied. The result shows that the surface texture of unstable minerals (amphibole, epidote) changed under strong chemical weathering in the Pliocene sediments. By contrast, unstable minerals of the Pleistocene sediments are relatively fresh and similar to those of the modern Changjiang sediment. The stable mineral tourmaline does not exhibit morphology changes in different chemical weathering conditions. No effect of grain size on geochemical composition is noticed. The single minerals of very fine sand and coarse silt show similar geochemical and morphological features. The integration of mineralogy, geochemical data, and grain size parameters yield a more precise understanding of the physical and chemical response of heavy minerals to different weathering conditions. The outcome of the study is also helpful in deciphering sediment provenance changes and environmental changes in the Changjiang basin.

Geochemical characterization and dating of R tephra, a postglacial marker bed in Mount Rainier National Park, Washington, USA

2016 ◽  
Vol 53 (2) ◽  
pp. 202-217 ◽  
Author(s):  
Mary A. Samolczyk ◽  
James W. Vallance ◽  
Joel F. Cubley ◽  
Gerald D. Osborn ◽  
Douglas H. Clark
Keyword(s):  
National Park ◽  
Chemical Weathering ◽  
Geochemical Data ◽  
Sedimentary Records ◽  
Multidisciplinary Study ◽  
Field Evidence ◽  
Weathering Indices ◽  
Mount Rainier ◽  
Mount Rainier National Park ◽  
Glass Compositions

The oldest postglacial lapilli–ash tephra recognized in sedimentary records surrounding Mount Rainier (Washington State, USA) is R tephra, a very early Holocene deposit that acts as an important stratigraphic and geochronologic marker bed. This multidisciplinary study incorporates tephrostratigraphy, radiocarbon dating, petrography, and electron microprobe analysis to characterize R tephra. Tephra samples were collected from Tipsoo Lake and a stream-cut exposure in the Cowlitz Divide area of Mount Rainier National Park. Field evidence from 25 new sites suggests that R tephra locally contains internal bedding and has a wider distribution than previously reported. Herein, we provide the first robust suite of geochemical data that characterize the tephra. Glass compositions are heterogeneous, predominantly ranging from andesite to rhyolite in ash- to lapilli-sized clasts. The mineral assemblage consists of plagioclase, orthopyroxene, clinopyroxene, and magnetite with trace apatite and ilmenite. Subaerial R tephra deposits appear more weathered in hand sample than subaqueous deposits, but weathering indices suggest negligible chemical weathering in both deposits. Statistical analysis of radiocarbon ages provides a median age for R tephra of ∼10 050 cal years BP, and a 2σ error range between 9960 and 10 130 cal years BP.

scholarly journals Geochemical Characteristics, Palaeoenvironment and Provenance of Uranium-Bearing Sandstone in the Sifangtai Formation, Northern Songliao Basin, Northeast China

Minerals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1019
Author(s):  
Yan Li ◽  
Feng-Jun Nie ◽  
Li-Cheng Jia ◽  
Sheng-Jun Lu ◽  
Zhao-Bin Yan
Keyword(s):  
Continental Margin ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Thick Layer ◽  
Songliao Basin ◽  
Geochemical Characteristics ◽  
Source Rocks ◽  
Geochemical Data ◽  
Water Medium ◽  
Semi Arid

During the Cretaceous period of the northern Songliao Basin (northeast of China), a 100 m thick layer of fluvial-phase sandstone (Sifangtai Formation) with uranium potential was widely deposited, but its geochemical characteristics, paleoenvironment, and provenance remain unknown. This research proposes a new set of relevant geochemical data for sandstones to investigate their paleoenvironment, provenance and tectonic setting. The results revealed that: (1) The sandstone of the Sifangtai Formation was dominated by feldspar lithic sandstone. Geochemical signatures demonstrate that these sandstones have a high silicon content (SiO2 = 68.30~83.60 wt%) and total alkali content, but are poor in magnesium and calcium. They are also enriched in Rb, Th, U, K and LREE, and depleted HFSE (e.g., Nb, Ta), with crustal magmatic source. (2) The paleoclimate discriminant indicated that the rocks of the Sifangtai Formation might that the climate of Sifangtai Formation is semi-arid, and the chemical weathering of the source rocks is weak under the semi-arid climate environment. (3) The combination of element Sr/Ba, 100 MgO/Al2O3 and the combination of v/v + Ni, V/Cr, Ni/Co, and Sr/Cu indicated that the paleo-water medium was deposited in an oxygen-rich freshwater environment when the Sifangtai Formation was deposited. (4) The discriminate diagrams showed that almost all the sandstones of the Sifangtai Formation fell in the range of the active continental margin, indicating that the source area of the sandstones of Sifangtai Formations is an active continental margin tectonic environment, and the source is a felsic rock developed in the Xiaoxing’an Ridge and Zhangguangcailing area.

THE IMPACT OF PHYSICAL AND CHEMICAL WEATHERING ON IRON SLAG FROM STANDISH, NY

2019 ◽  
Author(s):  
Maria L. Leonard ◽  
◽  
Rachel M. Kelk ◽  
Dori J. Farthing
Keyword(s):  
Chemical Weathering ◽  
Iron Slag ◽  
Physical And Chemical ◽  
The Impact

Nature and origin of the volcanic ash beds near the Permian–Triassic boundary in South China: new data and their geological implications

2019 ◽  
Vol 157 (4) ◽  
pp. 677-689 ◽  
Author(s):  
Binsong Zheng ◽  
Chuanlong Mou ◽  
Renjie Zhou ◽  
Xiuping Wang ◽  
Zhaohui Xiao ◽  
...  
Keyword(s):  
Trace Element ◽  
Continental Margin ◽  
South China ◽  
Volcanic Ash ◽  
Active Continental Margin ◽  
Main Body ◽  
Early Triassic ◽  
Late Permian ◽  
Triassic Boundary ◽  
Permian Triassic Boundary

AbstractPermian–Triassic boundary (PTB) volcanic ash beds are widely distributed in South China and were proposed to have a connection with the PTB mass extinction and the assemblage of Pangea. However, their source and tectonic affinity have been highly debated. We present zircon U–Pb ages, trace-element and Hf isotopic data on three new-found PTB volcanic ash beds in the western Hubei area, South China. Laser ablation inductively coupled plasma mass spectrometry U–Pb dating of zircons yields ages of 252.2 ± 3.6 Ma, 251.6 ± 4.9 Ma and 250.4 ± 2.4 Ma for these three volcanic ash beds. Zircons of age c. 240–270 Ma zircons have negative εHf(t) values (–18.17 to –3.91) and Mesoproterozoic–Palaeoproterozoic two-stage Hf model ages (THf2) (1.33–2.23 Ga). Integrated with other PTB ash beds in South China, zircon trace-element signatures and Hf isotopes indicate that they were likely sourced from intermediate to felsic volcanic centres along the Simao–Indochina convergent continental margin. The Qinling convergent continental margin might be another possible source but needs further investigation. Our data support the model that strong convergent margin volcanism took place around South China during late Permian – Early Triassic time, especially in the Simao–Indochina active continental margin and possibly the Qinling active continental margin. These volcanisms overlap temporally with the PTB biocrisis triggered by the Siberian Large Igneous Province. In addition, our data argue that the South China Craton and the Simao–Indochina block had not been amalgamated with the main body of Pangea by late Permian – Early Triassic time.

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