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The study of coral fossils with clear growth lines inShiqiantan Formation (310 Ma) in China showed the growth line increments of a single coral growing in this area is related to the sunlight illumination time. Moreover, the daily increment of the growth line caused by calcium carbonate depositions has an unusual bimodal curve. The study of this bimodal curve indicated Shiqiantan had evident four-season changes in the Late Carboniferous period, and the climate at that time was similar to that of modern North China. The present paper updates the oldest existing record of climate analysis materials and provides important information for the study of Late Paleozoic climate, as well as the ancient obliquity of ecliptic. [ABSTRACT FROM AUTHOR]

In our recent publication on the biodiversity of Paleozoic phytoplankton (Kroeck et al., 2022) we cited several works of Martin (Martin, 1996; Martin and Quigg, 2012; Martin and Servais, 2020) to present the hypothesis that during the late Paleozoic nutrient availability in the oceans increased significantly from a rather (super-) oligotrophic early to middle Paleozoic. We put this view in contrast to the notion, based on data on terrestrial sediment input, that nutrient availability generally decreased over the course of the Paleozoic. In his discussion paper, Martin (2022) expands on this hypothesis and the role of nutrients for biodiversification, and clarifies the use of the term "superoligotrophy" (Martin, 1996) for the early to middle Paleozoic interval. Martin (2022) highlights factors we neglected in our review of marine phytoplankton diversity in the Paleozoic. We largely agree with the arguments presented, and therefore consider this discussion as an excellent addition to our review. [ABSTRACT FROM AUTHOR]

The paper presents first data on isotopic U–Pb study (LA-ICP-MS method) of zircon from intrusive rocks of the Adyrtor intrusions – a group of small intrusives situated in the easternmost part of the deep-seated fault system of the "Nikolaev Line." Here, these intrusions cut through one of the oldest (1.8–2.6 Ga) complexes of the basement rocks of Tien Shan (metamorphic rocks of the "Kuilyu suite"). These intrusive rocks belong to the high-potassic calc-alkaline to shoshonitic series, with some geochemical signatures also of anorogenic (A-type) magmatism. These intrusions are accompanied by skarn and porphyry W–Mo–Cu–Au mineralization. Together with the other Au, W, and Cu deposits and occurrences, they are parts of the extended metallogenic belt of Tien Shan. The concordant isotopic U–Pb age data for zircon autocrysts indicate the crystallization of quartz syenite (330.7 ± 4.3 Ma) and quartz monzonite (329.5 ± 5.8 Ma) in the latest Early Carboniferous. The distinct W–Mo specialization of ore mineralization related to the intrusions studied is in agreement with the post-collisional tectonic setting during their emplacement, despite their older or similar age compared to the ore-bearing plutons in more western segments of the Middle Tien Shan, which corresponded to a subduction-related setting. This supports the possibility of the "scissor-like" (from east to west) closure of the Turkestan paleoocean that resulted in the earlier cessation of subduction in the eastern Tien Shan compared to the western Tien Shan. The rocks also contain zircon xenocrysts with older (on the order of 1.7–2.6 Ga) age, which is in agreement with the age of the host metamorphic rocks of the Tarim craton basement. This highlights the possibility of magma chamber development in the continental crust, together with the magma chambers in the metasomatically-enriched subcontinental upper mantle, the latter being common for high-potassic magmatism. [ABSTRACT FROM AUTHOR]

Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin (Western Desert, Egypt) necessitate a thorough oil-source correlation investigation. This objective is achieved through a meticulous analysis of well-log responses, Rock-Eval pyrolysis, and biomarker data. The analysis of Total Organic Carbon across 31 samples representing Paleozoic formations in the Siwa A-1X well reveals a spectrum of organic richness ranging from 0.17 wt% to 2.04 wt%, thereby highlighting diverse levels of organic content and the presence of both Type II and Type III kerogen. Examination of the fingerprint characteristics of eight samples from the well suggests that the Dhiffah Formation comprises a blend of terrestrial and marine organic matter. Notably, a significant contribution from more oxidized residual organic matter and gasprone Type III kerogen is observed. Contrarily, the Desouky and Zeitoun formations exhibit mixed organic matter indicative of a transitional environment, and thus featuring a pronounced marine influence within a more reducing setting, which is associated with Type II kerogen. Through analysis of five oil samples from different wellsdSIWA L-1X, SIWA R-3X, SIWA D-1X, PTAH 5X, and PTAH 6X, it is evident that terrestrial organic matter, augmented by considerable marine input, was deposited in an oxidizing environment, and contains Type III kerogen. Geochemical scrutiny confirms the coexistence of mixed terrestrial organic matter within varying redox environments. Noteworthy is the uniformity of identified kerogen Types II and III across all samples, known to have potential for hydrocarbon generation. The discovery presented in this paper unveils captivating prospects concerning the genesis of oil in the Jurassic Safa reservoir, suggesting potential links to Paleozoic sources or even originating from the Safa Member itself. These revelations mark a substantial advancement in understanding source rock dynamics and their intricate relationship with reservoir oils within the Siwa Basin. By illuminating the processes of hydrocarbon genesis in the region, this study significantly enriches our knowledge base. [ABSTRACT FROM AUTHOR]

This paper describes the in situ spores of the Calamospora type, macerated from sixty-one specimens of calamitean cones belonging to sixteen species of genera, such as the Palaeostachya, Macrostachya, Calamostachys, and Huttonia from the Pennsylvanian Czech Republic period, specifically from the Moscovian/Kasimovian ages (i.e., Duckmantian-Stephanian). The in situ spores were compared to twenty dispersed species of Calamospora. The majority of spores were microspores; however, some cones yielded both micro- and megaspores. Morphological variations of the in situ spores, including the diameter, labrum, contact area, ontogenetic stages, and secondary folds of the exine, are described, including their importance for the classification of calamospores. The relationships of Elaterites, Pteroretis, Vestispora, and some monopseudosaccate spores are discussed. All Paleozoic Calamospora-producing parent plants are summarized. [ABSTRACT FROM AUTHOR]

Simple Summary: In this study, we provide descriptions of three fossil species, Calamites cistii, Macrostachya sp., and Punctatisporites punctatus, discovered in the Cisuralian of the eastern Hexi Corridor, northwestern China. Our findings offer insights into the evolution of Calamitaceae strobili during the Late Paleozoic. Calamitaceae was the predominant arborescent element of the Late Paleozoic plant assemblages. However, there is currently controversy surrounding the evolutionary relationships of their four reproductive organs, and there is no unified understanding of the geographical distribution and species richness characteristics. This paper is based on the detailed description of the macro- and microstructures of Calamites and Macrostachya discovered in the Shanxi Formation of the Cisuralian in the eastern Hexi Corridor of northwestern China, and it discusses the evolutionary patterns of calamitean reproductive organs. The results indicate that the current specimens can be identified as the Calamites cistii and Macrostachya sp., and the in situ spores should exhibit distinct trilete marks, indicating that they belong to the Punctatisporites punctatus. The abundant fossil records suggest that the "Calamostachys" type should be considered as the ancestral type of strobili. Additionally, Calamitaceae was widely distributed in mid to low latitudes globally from the Pennsylvanian to the Cisuralian and coupled with paleogeographic distribution characteristics. [ABSTRACT FROM AUTHOR]

The Transantarctic Mountains (TAMs), a 3500 km long chain that subdivides East Antarctica from West Antarctica, are important for reconstructing the tectonic, glacial, and climatic history of Antarctica. With an ice-free area of 24 200 km2 (50% of the total in Antarctica), the TAMs contain an unusually high proportion of paleosols, including relict and buried soils. The unconsolidated paleosols range from late Quaternary to Miocene in age, the semi-consolidated paleosols are of early Miocene to Oligocene age, and the consolidated paleosols are of Paleozoic age. Paleosols on unconsolidated deposits are emphasized in this study. Examples are given from the McMurdo Dry Valleys (78° S) and two outlet glaciers in the central and southern TAMS, including the Hatherton-Darwin Glacier region (80° S) and the Beardmore Glacier region (85°300 S). Relict soils constitute 73% of all of the soils examined; 10% of the soils featured burials. About 26% of the soils examined are from the last glaciation (< 117 ka) and have not undergone any apparent change in climate. As an example, paleosols comprise 65% of a mapped portion of central Wright Valley. Paleosols in the TAMs feature recycled ventifacts and buried glacial ice in excess of 8Ma in age; and volcanic ash of Pliocene to Miocene age has buried some soils. Relict soils are more strongly developed than nearby modern soils and often are dry-frozen and feature sand-wedge casts when ice-cemented permafrost was present. The preservation of paleosols in the TAMs can be attributed to cold-based glaciers that are able to override landscapes while causing minimal disturbance. [ABSTRACT FROM AUTHOR]

The development of trench-arc-backarc (TABA) systems is uniquely associated with modern-style plate tectonics on Earth. The Qilian orogenic belt in NW China records the evolution history of the Proto-Tethys Ocean at the transition time from the Proterozoic to Phanerozoic. This paper presents systematic studies of petrography, U–Pb chronology and geochemistry on various rocks from a middle-ocean ridge (MOR)-type ophiolite belt, active continental margin and back-arc basin in the Qilian orogenic belt to address the development of a modern-style TABA system. Arc magmas include felsic intrusions with ages of 531 to 477 Ma and felsic-mafic arc volcanic rocks with ages of 506 to 439 Ma, showing distinctive features of typical magmatic rocks formed at an Andean-type continental margin. The back-arc basin is recorded by a 490- to 448-Ma suprasubduction zone (SSZ)-type ophiolite with boninite, and Silurian turbidite flysch formation. We establish a three-stage tectonic history from the initiation of subduction to the formation of a mature Japan-Sea-type back-arc basin at the active continental margin in the Early Paleozoic era. (1) Northward subduction of Proto-Tethys Ocean initiated and the Andean-type continental arc developed at ~530 to 500 Ma with continual crustal thickening; (2) a tectonic transition occurred from an Andean-type active continental margin to a West Pacific-type active continental margin at ~500 to 490 Ma with rapid thinning of crust to ~35 km; and (3) mature ocean basins and back-arc-basin (BAB) ophiolites were formed in the back-arc extensional environment at ~490 to 450 Ma. [ABSTRACT FROM AUTHOR]

The genetic types and evolution characteristics of pores are the important basis for evaluating the quality of unconventional shale reservoirs. In this paper, taking the Lower Cambrian Marine shales in southern China as an example, the microscopic pore structure, genetic types and evolutionary characteristics of shales are systematically studied. The results show that circular and oval organic pores with good connectivity and non-fixed inorganic pores with poor connectivity are mainly developed in marine shale. The marine shales mostly have laminar sedimentary structures, the thickness of which is several millimeters to several centimeters. Siliceous laminae, clay laminae, organic laminae and carbonate laminae were identified. Lamination can also be retained in oxygen-rich environments with rapid sediment inflow, which may be related to high turbidity fluid. The Lower Paleozoic marine shales in southern China have experienced a complex tectonic-thermal evolution history, which aggravated the complex distribution of laminar structures. Some shale sections show very low resistivity, and resistivity has a significant negative correlation with TOC content. Organic matter is the main factor that causes the extremely low resistivity of shale. This study is of great significance to accelerate the process of Marine shale exploration and development. [ABSTRACT FROM AUTHOR]

The Prototethyan Ocean has been suggested as an Early Paleozoic Ocean developed at the Gondwana northern margin. However, its spatial pattern, subduction style and closure time in SW Yunnan and SE Asia still remain unknown. The Prototethyan evolution in SW Yunnan and SE Asia and its internal connection with the South China Kwangsian (Ordo-Silurian) intracontinental orogenesis are also poorly constrained. By summarizing and analyzing the Early Paleozoic geological records in the Sibumasu and Indochina blocks, the eastern South China and SW Japan, this paper proposes the existence of a giant Ordo-Silurian igneous belt along the Gondwana northern margin. A preliminary limitation has been obtained regarding the source nature and migration pattern of the igneous belt. Our data allow us to propose a model of the Early Paleozoic Andean-type active continental margin along the East Gondwana northern margin. This is the foundation to determine the southward subduction of the southern branch of the eastern Prototethyan Ocean underneath the Sibumasu and Indochina blocks along the Yunxian-Menghai (SW Yunnan)-Thailand Peninsula and the Tam Ky-Phouc Son suture in Central Vietnam, respectively, and the eastward linkage with the Early Paleozoic Osaka subduction zone in SW Japan across the peripheral Sanya area. These data synthetically indicate an easterly-diachronous and propagating Andean-type Cambrian (Furongian)-Silurian (Llandovery) orogenesis along the Gondwana northern margin from Nepal, NW India, South Tibet, Qiangtang to Central Vietnam across South Indochina and Sibumasu. This paper reconstructs the Early Paleozoic locations of the Sibumasu and Indochina fragments, as well as SW Japan and South China continent in the Gondwana northern margin, and proposes the far-field effect on the South China Kwangsian intra-continental orogenesis from the subduction of the Early Paleozoic Prototethyan southern branch. [ABSTRACT FROM AUTHOR]

This paper records the results of a pioneering exploration borehole drilled in 1984 to a depth of 403.84 m in the London Basin and underlying London–Brabant basement high. The key objectives of the project were to measure the equilibrium temperature in the Paleozoic basement, estimate the temperature gradient after climate impact corrections and assess the heat flow in the area. From this, estimates of temperature at depths of 2000 m could be made with a view to evaluating potential geothermal resources. From the downhole measurements, a temperature gradient of 16°C km−1 was estimated with a temperature range between 46°C and 51°C at a depth of 2000 m, considered to be consistent with other UK sites where there is no contribution from high heat production granites. The results of the Thamesmead exploration borehole suggested that the geothermal potential of the Devonian and the Paleozoic basement below London is poor, and no further work was carried out. The work has remained unpublished until now but in view of the current renewed interest in geothermal resources it is appropriate to make the work public. Although the results were not encouraging, they do remain as a contribution to the revitalized assessment of geothermal resources in the London area and the UK in general. [ABSTRACT FROM AUTHOR]

The Yong'an-Meixian Late Paleozoic Hercynian depression, located in western Fujian-eastern Guangdong, is an important metallogenic belt in China. The Yushui copper-polymetallic massive sulfide deposit from the middle part of the depression, with extremely high copper grades, has attracted considerable attention and research interest from geologists for years. In most previous research, the ore-forming material source and metallogenic process were inferred from indirect evidence (i.e., using H-O-C-S isotopic systematics as geochemical tracers). In this paper, the ore-forming process of the Yushui deposit has been studied directly by using nontraditional stable (Fe–Cu) isotopes for the first time, providing new evidence for the genesis of this deposit. The results show that there is a relatively negative Fe-Cu isotopic composition in the Yushui deposit, with δ56Fe values ranging from −0.519 to −1.063‰ and δ65Cu values ranging from −1.539 to −1.609‰, respectively. The fractionation of Fe isotopes is primarily attributed to hydrothermal leaching of the basement strata by ore-forming fluids, along with rapid precipitation of sulfides during the ore-forming process. On the other hand, the fractionation of Cu isotopes is probably controlled by the relatively low temperature of ore formation, sulfide precipitation and the involvement of organic matter in mineralization. Combining our findings with previous studies, the ore-forming materials of the Yushui deposit are likely derived from the basement ore-bearing strata (pre-Devonian strata) through leaching by hydrothermal fluids. Moreover, some of the ore bodies might have been locally overprinted by late-stage hydrothermal reworking and alteration. [ABSTRACT FROM AUTHOR]

Hoshino (1991) argued that the sea-level in the Jurassic period was at the present depth of 6,000 m, and that the sealevel rise was caused by the uplift of the sea floor including the volcanic activity of flood basalts as well as the uplift of the crust after the Jurassic period. In order to provide evidence for Hoshino's sea-level rise theory, this paper investigates the sites where shallow-water sediments and volcanic rocks of subaerial eruption were found in the drilling records from DSDP to ODP. As a result, 256 sites were recovered with sediments and rocks indicating such shallow-water or land. Based on their distribution and assuming that they did not subsident we can estimate that the sea-level was about 6,000 m in the Late Jurassic period, 5,200 m in Barremian, 4,100 m at the end of Albian, 3,800 m in Early Eocene, 3,400 m in Late Oligocene, 3,400 m in Middle Miocene, and 3,000 m lower at the end of Miocene, or even lower in respectively. This supports the Hoshino's sea-level rise theory. However, the thickness of the coral reef limestone at each period suggests that the sea-level position at each period was lower than the past sea-level position estimated from the results of deep-sea drilling. Therefore, a sea-level rise curve was created by accumulating the amount of coastal onlap in the Haq’s curve and assuming that the sea-level was 3,000 m lower than the present sea-level at the end of Miocene epoch. According to the new sea-level rise curve proposed in this paper, the position of the sea-level at the end of the Jurassic period may have been considerably lower, about 12 km below present sea-level. In other words, the sea-level may have risen by 12 km since the Jurassic period. Based on the drilling records and the geological structure of each area, the deep-sea floor of the Atlantic and Indian Oceans is thought to have been composed of the Proterozoic and Hercynian basement rocks until the end of the Paleozoic Era, submerged by sea-level rise due to flood basalts since Triassic, and deepened by large-scale sea-level rise since Cretaceous. On the other hand, the base of the deep-sea floor of the Pacific Ocean is likely to be composed of the Archean basements, which were submerged more than 6,000 m by volcanic activity of basaltic lava of the Large Igneous Provinces (LIPs) mainly after the Late Jurassic period. [ABSTRACT FROM AUTHOR]

The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project aims to characterise the structure and orogenic processes involved in a major collisional mountain belt by multidisciplinary geoscientific research. Located in western central Sweden, the project has drilled two fully cored deep boreholes into the bedrock of the deeply eroded Early Paleozoic Caledonide Orogen. COSC-1 (2014) drilled a subduction-related allochthon and the associated thrust zone. COSC-2 (2020, this paper) extends this section deeper through the underlying nappes (Lower Allochthon), the main Caledonian décollement, and the upper kilometre of basement rocks. COSC-2 targets include the characterisation of orogen-scale detachments, the impact of orogenesis on the basement below the detachment, and the Early Paleozoic palaeoenvironment on the outer margin of palaeocontinent Baltica. This is complemented by research on heat flow, groundwater flow, and the characterisation of the microbial community in the present hard rock environment of the relict mountain belt. COSC-2 successfully, and within budget, recovered a continuous drill core to 2276 m depth. The retrieved geological section is partially different from the expected geological section with respect to the depth to the main décollement and the expected rock types. Although the intensity of synsedime ntary deformation in the rocks in the upper part of the drill core might impede the analysis of the Early Paleozoic palaeoenvironment, the superb quality of the drill core and the borehole will facilitate research on the remaining targets and beyond. Protocols for sampling in the hard rock environment and subsequent sample preservation were established for geomicrobiological research and rock mechanical testing. For the former, a sparse sample series along the entire drill core was taken, while the target of the latter was the décollement. COSC-2 was surveyed by a comprehensive post-drilling downhole logging campaign and a combined borehole/land seismic survey in autumn 2021. This paper provides an overview of the COSC-2 (International Continental Scientific Drilling Project – ICDP 5054_2_A and 5054_2_B boreholes) operations and preliminary results. It will be complemented by a detailed operational report and data publication. [ABSTRACT FROM AUTHOR]

Abstract—In the paper, we present the results of paleomagnetic studies on numerous intrusive bodies of the Bashkirian megazone, a major tectonic zone of the Southern Urals. More than 70 intrusions in various parts of the Bashkirian megazone (in the northern, central, and southern part of the structure) were sampled. The studied intrusions have Riphean age. However, as a significant part of the rocks of the Southern Urals, these intrusive bodies were remagnetized during the Late Paleozoic collision within the Urals fold belt. Here, we discuss the secondary Late Paleozoic component of natural remanent magnetization. According to the obtained paleomagnetic data, the secondary Late Paleozoic component in most of the Bashkirian megazone is post-folding, i.e., formed after the completion of the main phase of fold deformations in the Southern Urals. A comparison of paleomagnetic directions obtained from intrusions in different parts of the Bashkirian megazone showed that there were no significant movements of individual parts of the Bashkirian megazone relative to each other after the formation of the Late Paleozoic component. The Late Paleozoic remanence component yielded a paleomagnetic pole of Plong = 171.6°, Plat = 39.9°, α95 = 5.9°, and N = 6 from six regions (38 sites) in the Bashkirian megazone. The obtained pole is statistically indistinguishable from the mean of 15 poles for Stable Europe with ages of 280–301 Ma. Thus, the secondary Late Paleozoic component in the Bashkirian megazone formed approximately 280–301 million years ago, after which the Bashkirian megazone did not experience any relative motions with respect to the East European craton. [ABSTRACT FROM AUTHOR]

Controversy over the geodynamic interpretation of the early Paleozoic granites in the South China Block constrains understanding of tectonic–magmatic evolution. In this paper, we present zircon U-Pb age, Hf isotope, and major and trace element data of the early Paleozoic granites in the Jilongjie region, south-central Hunan Province. A sample that yielded a weighted average 206Pb/238U age of 425 ± 3 Ma falls into the post-collisional granite field in the classification discriminant of magmatic rocks. Geochemical features indicate that the Jilongjie pluton is a shoshonitic metaluminous rock. The Jilongjie pluton's chondrite-normalized rare earth element patterns exhibit a slight enrichment of light rare earth elements (LREEs) relative to heavy rare earth elements (HREEs) with (La/Yb)N ratios of 15.1–23.7 and weak Eu anomalies (Eu/Eu* = 0.68–0.78). Zircon Hf isotope results show εHf(t) ranging from −9.94 to −0.69. Jilongjie granite's parent magma originated from a mixing of crust-derived felsic and mantle-derived mafic magmas, which then underwent fractional crystallization during its ascent. Jilongjie granite was generated through a post-collisional extensional setting associated with delamination of the thickened lithosphere. [ABSTRACT FROM AUTHOR]

The variations in source rocks and melting conditions of granites can provide essential clues for the crustal magmatic response in orogenic process. Based on geochronology, whole‐rock and mineral chemistry, this paper reveals two different granites in the Northern Qinling migmatite complex, which reveal obvious differences in source region and melting condition. The older granodiorite (402 ± 0.8 Ma) displays typical Na‐rich adakite affinity, i.e., high Na2O/K2O (2.04 to 2.64) and Sr/Y (96 to 117) ratios, they have relative evolved isotopic compositions (εNd(t) = –0.52 to –0.04; zircon εHf(t) = –0.06 to +7.78). The younger leucogranite (371 ± 2 Ma) displays higher SiO2 (72.32 to 73.45 wt%), lower (TFeO + MgO + CaO + TiO2) contents (<2 wt%) and depleted Sr‐Nd‐Hf isotopic compositions (i.e., εNd(t) = +2.6 to +3.0; zircon εHf(t) = +5.94 to +14.12), as well as high 10000 × Ga/Al and TFeO/MgO ratios, indicating that they represent highly fractionated I‐type granites that derived from melting of juvenile crust. The variations in source rocks and melting condition of the two granites indicating a tectonic switch from compression to extension in 400 to 370 Ma, this switch is later than that in the eastern section of the North Qinling, indicating a scissor collision process between the South Qinling and North China Craton (NCC) in Devonian era. [ABSTRACT FROM AUTHOR]

With the targets of petroleum exploration transferred to the deep and ancient strata, abundant oil and gas resources have been found in Lower Paleozoic and older strata in central and western China. Due to complex evolutionary processes including multiple episodes of hydrocarbon accumulation and ubiquitously accompanied by secondary alterations, significant uncertainties remain concerning the generation time and accumulation processes of these revealed petroleum sources. In this paper, relative pure Re and Os elements existing in the asphaltene fractions of Lower Cambrian solid bitumen collected from the Guangyuan area, western Sichuan Basin, SW China and Middle–Lower Ordovician heavy oils in the Aiding area of the Tahe oilfield in the Tarim Basin, NW China were successfully obtained by sample pretreatments, and Re–Os isotopic analysis was subsequently carried out for the dating of these. The Re–Os isotopic composition indicates a generation time of Guangyuan bitumen to between 572 Ma and 559 Ma, corresponding to the late Sinian period of the Neoproterozoic era. By the means of Re–Os isochron aging, initial 187Os/188Os ratios, and carbon isotopic compositions, the Lower Cambrian bitumen is supposed to originate from source rocks of the Doushantuo Formation in the Sinian strata and subsequently migrated into the reservoirs of the Dengying Formation. This previously reserved petroleum was transformed into its present bitumen state by the destruction of reservoirs caused by tectonic uplift. The Re–Os dating results of Middle–Lower Ordovician heavy oil of Tarim Basin suggest that it was formed between 450 Ma to 436 Ma, corresponding to the Late Ordovician–Early Silurian system, and the generated petroleum likely migrate into the Middle–Lower Ordovician karst reservoirs to form early oil reservoirs. With tectonic uplift, these oil reservoirs were degraded and reformed to the heavy-oil reservoirs of today. [ABSTRACT FROM AUTHOR]

On the basis of elaborating on the regional geological background, this paper analyzes the lithological and sedimentary characteristics and explorative prospects of new strata with oil and gas in the southern and surrounding areas of Dayangshu Basin. Based on the latest high-precision airborne gravity and magnetic comprehensive survey data, combined with the latest data from geological explorations, physical surveys, and drilling, and the use of basin structure layering combination methods, we clarified the characteristics of the bottom of the Jurassic–Cretaceous and the occurrence characteristics of the Upper Paleozoic in the study area and revealed the determinative effect of multi-period structures on the most important sedimentary layers. Then, we summarized the accumulation conditions and prediction methods of hydrocarbons and proposed the oil and gas prospects of these deep new strata. The results show that the Liuhe Sag in Dayangshu Basin, the depression in the northeast of Longjiang Basin, and the northern parts of the Taikang swell have good source–reservoir–cap combination conditions and favorable structural characteristics for oil and gas, where there is a high potential for exploration. [ABSTRACT FROM AUTHOR]

Abstract—The paper demonstrates the possibility of application of the 143Nd/144Nd–Sm/Nd and Nb/Y–Zr/Y diagrams to systematics of basic–ultrabasic complexes of different age: Paleozoic Kalinovsky, Cambrian Sergeevsky and Vladimiro-Aleksandrovsky, and Jurassic and Paleocene ones. The position of data points of the Kalinovsky, Sergeevsky, and Vladimiro-Aleksandrovsky complexes in the diagrams indicates their derivation from a primitive mantle-type (BSE) source, the derivatives of which are frequently associated with Cu, Ni, Co, and PGE mineralization. The position of data points of metabasic rocks of the Avdokimovsky complex and peridotite rocks of the Dalny Kut massif in these diagrams suggests that they have originated from depleted mantle and are promising for the discovery of PGE-bearing chromite mineralization. Data points of Paleocene explosive structures of Sikhote-Alin in the Nb/Y–Zr/Y diagram fall on the trend of recycled crust as a source. This explains the alkaline (to subalkaline) type of magmatism and the high gas saturation of magmas. The explosive structures resemble lamproite pipes, while their rocks are geochemically and mineralogically close both to lamproites and kimberlites. [ABSTRACT FROM AUTHOR]

Heart Mountain, Wyoming, USA, is a geological puzzle. "Paleozoic" carbonates overlie "much younger Mesozoic and Cenozoic" rock. The implication is that several mountain-sized blocks broke from a detachment fault and slid up to 45 km. Part 1 of this series critiqued recent models that propose low-friction cushions to move the Heart Mountain blocks. This paper compliments that study by examining how the proposed movement started and was sustained over uneven terrain via seven questions raised by uniformitarian researchers. Current models, uniformitarian and creationist, cannot explain the location of Heart Mountain as a detachment and slide. Unless fresh ideas are forthcoming, the implication that these "Paleozoic" rocks of Heart Mountain are younger, not older, than the underlying "Mesozoic" rocks needs exploring. [ABSTRACT FROM AUTHOR]

The paper presents results of detailed geological research of quartzite in the wider area of Smrĉevice, southeastern of Gornji Vakuf-Uskoplje. Based on the defined boundaries of surface distribution and research results, geological reserves of about 12 million tons have been determined in the wider area of Smrcevica. The quartzite reserves that have been so far determined in this area are at a low level of geological research. The paper contains an overview of the geological characteristics of the area, qualitative and quantitative characteristics of quartzite, and the mineral raw material potential of quartzite in the Smrĉevice area according to the PERC standard. The results of the conducted research indicate that the general geological and technical-exploitation factors are relatively favorable and indicate a possible profitable exploitation of the deposit. Taking into account the significant raw material potential, and the possibility of expanding the existing raw material base, this area has special importance for the perspective development of quartzite exploitation and its use in the production of ferrosilicon and silico-metals. [ABSTRACT FROM AUTHOR]

The western part of the Central Asian Orogenic Belt, which comprises folded areas in Kazakhstan, Kyrgyzstan, and northwestern China, includes a number of large Precambrian sialic massifs that are framed by deformed and dismembered Paleozoic ophiolites and by island arc and flysch formations. The basements of the massifs are commonly made up of diverse metamorphic complexes, some of which were metamorphosed under high and ultrahigh pressures in the Early Paleozoic at ~480–530 Ma. These metamorphic formations are the Zerendy Group of the Kokchetav massif in northern Kazakhstan; Akdzhon Group of the Issyk-Kul massif in the northern Tien Shan); Aktyuz, Kemin, and Koyandy complexes of the Chu-Kendyktas and Zheltau massifs in southern Kazakhstan and the northern Tien Shan; and the Kassan Group of the Ishim–Naryn massif in the central Tien Shan. The paper reviews data on the structures, compositions, and metamorphic evolutions of the high- and ultrahigh-, and medium-pressure metamorphic rocks of these massifs. Numerous P–T assessments have been made for the near-peak and/or post-peak retrograde metamorphism, and some prograde P–T paths have been calculated for the key rock types over the past three decades of the studies. Near-peak and/or post-peak metamorphic ages and some ages of retrograde metamorphism are estimated for most of the high- and ultrahigh-pressure rocks. The paper discusses problems faced by the researcher when building geodynamic models for the high- and ultrahigh-pressure complexes in various massifs of the western part of the Central Asian Orogenic Belt. It is shown that any reliable model shall be underlain by detailed information on the compositions, ages, and formation environments of the protoliths for the ultrahigh-, high-, and medium-pressure rocks and complexes. Moreover, the structures and compositions of Paleozoic complexes surrounding the Precambrian massifs shall also be taken into consideration. [ABSTRACT FROM AUTHOR]

Heart Mountain, Wyoming, USA, is a geological puzzle. Paleozoic carbonates overlie much younger Lower Cenozoic rock. So, either several mountain-sized blocks broke apart and slid up to 45 km from where they were originally deposited onto the younger rock or the way the relative ages of the base layer and the blocks are assessed is wrong. This paper, with its partner, examines the issues and problems explaining this proposed event. Part 1 examines three (uniformitarian) models of a low-angle slide on a low-friction cushion. In Part 2, another six essential issues, including how the movement started and was sustained over uneven terrain, are examined. The joint conclusion is that present models are seriously inadequate. [ABSTRACT FROM AUTHOR]

Understanding of the geodynamic evolution of the Tethyan realm cannot be complete without paleogeographical reconstructions of the North Qiangtang Block (NQB) that occupies a central position in Tibet. However, the reliability of such a reconstruction for the Paleozoic still requires substantial improvement. In this paper, we present paleomagnetic results obtained from the Middle Permian limestones and Upper Permian volcanic rocks in the Tanggula area, aiming to provide precise constraints on the NQB kinematics during the geodynamic evolution of the Tethys realm. Combined with other available paleomagnetic data from the NQB, our results suggest that the block was stably located at ~24°S for a long time before the Middle Permian, started to drift rapidly northward in the Middle Permian, and reached ~8.4°S in the Late Permian. The NQB continued drifting rapidly northward during the Triassic until merging with the southern margin of Eurasia in the Late Triassic. We reviewed new and available paleomagnetic and geological data and proposed a revised model for the tectonic evolution of the eastern Tethys realm. The NQB likely belonged to a ribbon-like separate continental archipelago in the middle of the Paleo-Tethys Ocean during the early--late Paleozoic. The Cimmerian continent, including the South Qiangtang Block (SQB), rifted away from the northern margin of Gondwana and drifted northward to ~22°S in the Middle Permian. The continent approached or partially collided with the NQB, resulting in the rapid northward movement of the NQB and the formation of the Longmuco--Shuanghu suture between the NQB and SQB. [ABSTRACT FROM AUTHOR]

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With the popularization of natural gas and the requirement of environmental protection, the development and utilization of natural gas are particularly important. The status of natural gas in China's oil and gas exploration and development is constantly improving, and the country pays more and more attention to the exploitation and utilization of natural gas. The tight sandstone of Upper Paleozoic in Ordos Basin has the characteristics of low porosity, low permeability, and large area of concealed gas reservoirs. With the increasing demand for natural gas in China, systematic analysis and research on the geological conditions and enrichment law of large area gas reservoirs of tight sandstone of Upper Paleozoic in Ordos Basin to guide exploration and production also pose a great challenge to the current level of natural gas exploration and development in China. In order to solve this problem, this paper takes the Upper Paleozoic tight sandstone in Hangjinqi area in the north of Ordos Basin as the research object, summarizes the natural gas accumulation conditions of tight sandstone according to the geological characteristics of Ordos Basin, determines the main control factors of gas accumulation by superposition method in combination with the distribution characteristics of natural gas, simulates the dynamic process of gas accumulation, establishes the gas accumulation model, analyzes the conditions of gas accumulation and enrichment by statistical methods, summarizes the accumulation and enrichment rules of natural gas, and predicts the favorable exploration areas for natural gas. The results show that the relationship between hydrocarbon source rocks, traps, migration and transportation, and other reservoir-forming conditions and the distribution characteristics of natural gas is summarized, and the main controlling factors of reservoir-forming are determined by superposition method. We simulate the evolution process of faults, strata, oil, gas, and water flows in the study area and establish the dynamic reservoir-forming process of natural gas. By combining the reserve data with the reservoir source distance, reservoir facies type, and gas filling times, the reservoir-forming and enrichment conditions are studied by statistical analysis method, and the reservoir-forming and enrichment rules are summarized by combining the main controlling factors. The enrichment of natural gas is controlled by the development degree of source rocks, favorable tight sandstone combination, confluence channel, and local structure. According to the law of accumulation and enrichment, the division standards of favorable areas in different horizons are established, and the favorable exploration areas in the study area are predicted. The results provide theoretical data support for natural gas exploration in the study area. [ABSTRACT FROM AUTHOR]

This paper presents the data on the geological structure of the Lower Paleozoic complexes of the Omulevka and Rassokha terranes, which occur in the western part of the Kolyma–Omolon microcontinent. The Lower Paleozoic rocks of both terranes are mostly terrigenous and terrigenous-volcanic, respectively. The U–Pb dating of detrital zircons allowed the determination of the provenances of clastic material and paleogeographical position of terranes for the Early Paleozoic. The age of detrital zircons indicates that the main sources of clastic material for the Ordovician–Silurian sedimentary rocks of the Omulevka Terrane were located at the northern and northeastern passive margin of the Siberian Craton. For the entire Early Paleozoic, the Rassokha Terrane occurred close to a northeastern margin of Laurentia and the northwestern margin of Baltica. [ABSTRACT FROM AUTHOR]

This paper reports geological–structural and mineralogical data on the relationships of Paleozoic ore veins with Carboniferous and Mesozoic rocks at the Kubaka gold–silver deposit in the Omolon cratonic terrane. The presented observations are inconsistent with an Upper Carboniferous upper age limit of the deposit, which was inferred by Akinin et al. (2020) on the basis of isotope–geological studies of ores and rocks sampled in an outcrop of the ore body in the quarry of the Tsokol'naya Zone. [ABSTRACT FROM AUTHOR]

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The tectonic evolution of the Qinling orogen is key to understanding the process of convergence between the North China Block (NCB) and the South China Block (SCB). The Wuguan Complex and Liuling Group, situated along the southern margin of the Shangnan–Danfeng suture zone (SDSZ) between the North Qinling Terrane (NQT) and the South Qinling Terrane (SQT), are important indicators of the late Paleozoic tectonic evolution of the Qinling orogen. In this paper, the detrital zircon U–Pb geochronology and geochemical analysis of the Wuguan Complex and Liuling Group are carried out. Detrital zircons from two metasedimentary rock samples of the Liuling Group yield a major age peak at 460 Ma and two subordinate peaks at 804 Ma and 920 Ma, with a few older grains having formed between 1000–2549 Ma. One metasedimentary rock sample of the Wuguan Complex has a similar age spectrum as that of the Liuling Group, which shows the main age peak at 440 Ma and two subordinate peaks at 786 and 927 Ma, indicating all detrital zircon age results have the same source area. Geochemical analyses suggest that the sedimentary rocks of the Liuling Group and part of the Wuguan Complex were deposited in the tectonic setting of the continental island arc (CIA), while the geochemical characteristics of the other group of sedimentary rocks of the Wuguan Complex indicate the mixing of basic rock sources. The protolith of garnet amphibolite and hornblende schist, which were collected from the Wuguan Complex, were classified as andesite and basalt, with the nature of arc andesite and oceanic island basalt, respectively. In combination with regional data, we suggest that the Liuling Group and the Wuguan Complex were deposited in a fore-arc basin. Additionally, the Wuguan Complex was subsequently incorporated into the tectonic mélange by the northward subduction of the Paleo-Qinling Ocean. Zircons from the subduction-related metamorphic igneous rocks in the Wuguan Complex yielded a weighted mean age of 365 ± 19 Ma, indicating that the Paleo-Qinling Ocean between the SQT and NQT was still subducted at the end of Devonian. [ABSTRACT FROM AUTHOR]

The Truong Son orogenic belt (TSOB) is one of the most important orogenic belts in the Indochina block. There are numerous mafic to felsic intrusions in the Early Paleozoic caused by the Tethyan orogeny. However, the tectono-magmatic evolution of the TSOB in the Early Paleozoic is still unclear. In this paper, zircon U-Pb dating, whole-rock geochemistry, and the Sr-Nd isotopic data of the Early Paleozoic magmatic rocks have been systematically investigated to explore the petrogenesis and tectonic significance of these rocks in the TSOB. Based on our new results integrated with previous geological data, four major tectono-magmatic episodes are identified. (1) The Middle Cambrian (~507 Ma) is the early stage of northward subduction of the Tamky-Phuoc Son Ocean. (2) The Early Ordovician to Middle Ordovician (483–461 Ma) is the main subduction stage of the Tamky-Phuoc Son Ocean. The intrusive rock associations imply the closure of the Tamky-Phuoc Son Ocean. (3) The Late Ordovician to Early Silurian (461–438 Ma) is the collision stage of the Kontum massif and Truong Son terrane. (4) The Early Silurian to Late Silurian (438–410 Ma) is the late stage of collision accompanied by slab roll-back. [ABSTRACT FROM AUTHOR]

The provenance of the upper Cambrian to Upper Ordovician sedimentary rocks of Tasmania and Waratah Bay in southern Victoria provides information about the complex and dynamic tectonic environment present during their deposition. This paper uses U–Pb detrital zircon data to constrain stratigraphic comparisons and tectonic reconstructions of these rock sequences. Multivariate statistics are used to investigate the similarity between the U–Pb ages and quantify the disparity among different samples from various locations. In western and central Tasmania, the Tyennan region supplied most detrital zircons during the late Cambrian and Early Ordovician. The overlying Middle Ordovician Pioneer Sandstone records a switch in provenance with zircons derived from the Mount Read Volcanics (MRV) mixed with zircons similar to those from continental-derived Paleozoic sedimentary rocks deposited throughout east Gondwana. The Middle to Upper Ordovician Gordon Group in western and central Tasmania lacks detrital zircons younger than 1.2 Ga, which indicates a return to a local provenance from Precambrian rocks. In southern Tasmania, the switch to zircons derived from the MRV and east Gondwana-like sources occurred earlier within the Cambrian Deadmans Bay Formation, which is dominated by the east Gondwana Paleozoic zircon age signature. In the East Tasmania Terrane, Ordovician sedimentary rocks from Lefroy have detrital zircon populations dominated by Neoproterozoic and earliest Paleozoic sources similar to the Ordovician sedimentary rocks in the Lachlan Orogen. In southern Victoria, the Bear Gully Chert from Waratah Bay exhibit both Tyennan and distal Gondwana detrital sources. The switching of detrital zircon sources in the west Tasmanian sedimentary sequences implies the docking of Tasmania with mainland Australia during the Cambrian Tyennan Orogeny. The arrival of the distal zircons into these basins occurred at different times in the different areas, reflecting a complex local topography and paleogeography. Paleozoic sedimentary rocks in Tasmanian exhibit multisource detrital U–Pb age signatures that change over time, implying tectonic activity during their deposition. Paleozoic sedimentary rocks in northeastern Tasmania show Gondwana-wide detrital signatures similar to Lachlan Orogen. The Ordovician Bear Gully Chert at Waratah Bay in southern Victoria shows mixed Tasmanian and distal Gondwana detrital populations. The change in detrital zircon signature in western Tasmania suggests that VanDieland docked with the Australian continent during the Cambrian Tyennan Orogeny. [ABSTRACT FROM AUTHOR]

The Western Carpathians and Himalayas belong to the same global Alpidic orogenic system, which is the result of Euroasian plate collision with the continental fragments of Gondwana after closing of the Tethys ocean. Having the field experiences from both distant mountain ranges of the same orogenic system and applying the principles of comparative tectonics, they were evaluated and compared in the paper. Generaly, they have the same collisional structural-tectonic style, but there are as well many peculiarities and differences resulting from the specific conditions of collision in the Western Carpathian and Himalayan areas. The Western Carpathians structure is a result of gradual alternation of Variscan (Hercynian; Paleozoic), Paleo-Alpine (Mesozoic) and Neo-Alpine (Cenozoic) convergent and divergent plate tectonic processes, while the Himalayas represents purely Neo-Alpine Cenozoic structure evolved during the continual long lasting and rapid plate convergence. Despite the geosutures from the earlier orogenic evolutions are known in the parallel north-located zone, too. As the most important factors, influencing character of collision, seems to be the geometry of converging plate margins and the rate of the ocean floor spreading/subduction, driving the orogenesis. Paper gives a brief overview of tectonic architecture and evolution of both mountain ranges and compares their common features and contrasts. [ABSTRACT FROM AUTHOR]

The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain. The abundant, well-preserved geologic records make it an ideal area for studying the tectonic evolution of Proto- and Paleo-Tethys. In this paper, we focus on several major tectonic units in SW Yunnan and reconstruct the Tethyan evolution from the early Paleozoic to the early Mesozoic, based on stratigraphic, sedimentologic, and magmatic evidences. The recently discovered early Paleozoic Yunxian-Menghai ophiolitic belt in the Lincang Terrane situated east of the Changning-Menglian Belt represents the suture zone of the Proto-Tethys. The oceanic basin of Proto-Tehtys opened in the latest Neoproterozoic and subsequently began subducting in the late Miaolingian of the Cambrian (about 505 Ma). From the late Late Ordovician to the ealiest Silurian (about 450–442 Ma), the Proto-Tethys basin gradually closed resulting in the collision of the continental plates on both sides of the Proto-Tethyan ocean. The main collision stage occurred in the early Silurian (about 442–430 Ma) and the post-collision stage lasted from the mid-Silurian to the early Carboniferous (430–355 Ma). The earliest record of Paleo-Tethyan oceanic crust was generated in the late Devonian, and the ocean was then subducted in an eastward direction in the middle Late Carboniferous (about 310 Ma). The initial collision stage in the Paleo-Tethys took place at the end of the Permian (about 253 Ma), and the main stage of the collision persisted into the early Ladinian (about 253–238 Ma). This was followed by post-collision extension from the late Ladinian to the early Jurassic (ca. 238–196 Ma). We suggest that the opening of Paleo- Tethyan Ocean in SW Yunnan was a result of the extensional rift basin of the Proto-Tethys. Additionally, the activity of the Manxin mantle plume was likely a crucial factor in the rapid expansion of the Paleo-Tethyan Ocean. [ABSTRACT FROM AUTHOR]

The paper presents a reconstruction of metamorphic stages in the Moren and Erzin metamorphic complexes in the Khan-Khuhay block of northern Mongolia. This reconstruction is used as a basis for discussing the general geodynamic history of the Sangilen terrain of the Tuva–Mongolia Massif. The calculated clockwise P–T path shows two stages of metamorphism: (1) collisional metamorphism at 9 kbar, 740°C; and (2) metamorphism related to a regional magmatic episode, at 6–7 kbar, 860–880°C. Geochemical and petrological features of rocks in the Khan-Khuhay block demonstrate that these rocks are similar to those of the metamorphic block of Western Sangilen in southeastern Tuva. Quartz monzodiorite intrusive bodies first found in the Khan-Khuhay block show geochemical features similar to those of Ordovician gabbro–monzodiorite intrusions in the western Sangilen. The Khan-Khuhay quartz monzodiorite intrusions may be small apophyses of an intermediate deep crustal magma chamber and could be a probable thermal source of metamorphic stage M2 in the Khan-Khuhay block. The numerical thermo-mechanical model of metamorphism in the Khan-Khuhay block explains the heating in the thickened crust during collision by a higher (relative to the average crustal) radiogenic heat production of 1.52 μW/m3. Computer modeling indicates that the P–T parameters of the second metamorphic stage could be reached only with the involvement of magmatic heat from the monzodiorite intrusion. The P–T metamorphic parameters calculated using mineral thermobarometry, similarity of geochemical characteristics, and results of the thermomechanical modeling allow us to conclude that the Erzin and Moren complexes have undergone a joint tectono-metamorphic evolution. [ABSTRACT FROM AUTHOR]

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High-Mg andesites (HMAs) and their cognate intrusive rocks constitute volumetrically very small proportions of the total earth, and are mainly distributed along the edges of convergent plates. Petrogenetic studies can provide possible solutions for discrepancies in the geodynamics and subduction zone evolution. This paper presents the first ever reports of the newly discovered high-Mg diorite in Akechukesai area, the western part of the East Kunlun Orogenic Belt, and provides a reference for the evolutionary history and subduction mechanism of the Proto-Tethys Ocean. Akechukesai high-Mg diorites yielded a weighted mean zircon U-Pb dating age of 427.3 ± 2.3 Ma (Middle Silurian). Results of the geochemical analyses show that the high-Mg diorites were high-K calc-alkaline series with the SiO2 content ranging 50.40 to 55.41 wt%. They are characterized by high values of Mg# (67–77), high MgO (6.92–10.58 wt%), TiO2 (0.53–0.87 wt%), Cr (286–615 ppm), Ni (61–124 ppm), Ba (570–927 ppm) contents, and low FeOtotal/MgO ratios (0.54–0.89). Furthermore, they exhibit nearly flat right-declined rare-earth element (REE) patterns with slight LREE enrichment. The samples are enriched in large ion lithophile elements (e.g., Ba, Rb, and Th) and depleted in high field strength elements (e.g., Ta, Nb, and Ti). These geochemical features are analogous to the sanukitic high-Mg andesites. The mean value of the initial εHf(t) is −1.3, indicating that the source is enriched mantle. The values of Rb/Cs, Ba/La, and La/Sm ratios suggest that subducting sediments formed an important component of the magmatic source. The presence of water-bearing minerals such as amphibole and biotite indicate a water-rich and oxygen-rich primitive magma system. Petrogenetic analysis indicates that the Akechukesai high-Mg diorites probably formed by melts and aqueous fluids produced from partial melting of the subducting sediments interacting with mantle peridotites. We hypothesize that, after the closure of the Proto-Tethys Ocean Basin in the Middle Silurian, the deep subducted slab broke-off and formed a slab window, asthenospheric material upwelled heating the subducting sediments and causing them to melt. Thus, we suggest that the emplacement of the Akechukesai high-Mg diorites mark the commencement of post-collisional magmatism. [ABSTRACT FROM AUTHOR]

The geodynamic mechanism responsible for the generation of Early Paleozoic magmatism within the Qilian Block, northwest China, remains controversial. In this paper, we present new geochronological, mineralogical, and geochemical data for the Hejiashan (HJS) granite and Lajishan (LJS) quartz diorite from the eastern Qilian Block, to constrain their origin and the regional evolutionary history. Laser abalation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U–Pb dating results show that the HJS granites and LJS quartz diorites were emplaced between 445 and 438 Myr ago. The HJS granites are high-K calc-alkaline, metaluminous to weakly peraluminous, with K2O/Na2O weight ratios of 0.84–1.12. The LJS quartz diorites are calc-alkaline and metaluminous with K2O/Na2O weight ratios of 0.34–0.46. Both have similar whole-rock Sr–Nd isotopic compositions. They are characterized by low heavy rare earth elements (HREEs) and Y concentrations, and high Sr/Y and La/Yb ratios, similar to adakitic rocks. Notably, the LJS quartz diorites are more depleted in HREEs and Y, and have much higher Mg# [= 100 × Mg/(Mg + Fe)], La/Yb, Sr/Y, and zircon εHf(t) values, and MgO, Cr, Co and Ni concentrations than those of the HJS granites. The HJS granites were most likely derived from partial melting of a thickened juvenile lower crust with amphibole and minor plagioclase as residual phases in the magma source. Conversely, the LJS quartz diorites were produced by partial melting of the subducted oceanic slab and minor sedimentary materials in the garnet and rutile stability field. Combined data from this and previous studies suggest that the Early Paleozoic magmatism within the Qilian Block mainly occurred ca. 464–402 Myr ago as a response to post-collisional extension. Break-off of the northward subducted South Qilian oceanic slab after continental collision between the Qaidam and Qilian Blocks was the primary dynamic mechanism responsible for the Early Paleozoic extensive crust-mantle interaction and magmatism within the Qilian Block. [ABSTRACT FROM AUTHOR]

Ichnology is fundamental to understanding characteristics of paleoenvironments such as hydrodynamic energy, oxygenation, salinity and substrate consistency. The Itararé Group is a Mississippian-Cisuralian lithostratigraphic unit of the Paraná Basin, in which trace fossils have been increasingly employed in paleoenvironmental reconstructions during the Late Paleozoic Ice Age in western Gondwana. The upper unit of the Itararé Group, the Rio do Sul Formation, exhibits a diverse trace fossil assemblage preserved in fine-grained rhythmites deposited in glacially related aquatic environments. In these rhythmites, trackways and trails produced by terrestrial and aquatic organisms were previously described. In this paper we report a new trace fossil collected from a rhythmite quarry near Trombudo Central, Santa Catarina state, and discuss potential paleoenvironmental implications. The studied specimen consists of an arthropod jumping trackway which could indicate a subaerial paleoenvironmental setting corroborating previous ichnological studies. [ABSTRACT FROM AUTHOR]

The mechanics of crustal growth in the Altaids during the Phanerozoic is still not well understood. This paper reports new geochronological, geochemical, and isotopic data from Paleozoic adakitic intrusions in the Dananhu arc in the Chinese Eastern Tianshan with the aim of better understanding the specific mechanisms of crustal growth. Our new LA-ICPMS U–Pb zircon age data show that four phases of adakitic intrusions formed at 410–413 Ma, 385–387 Ma, 335 Ma, and 313–311 Ma. Combined with previous data of ours and from the literature, there were seven phases of adakitic intrusions from the Silurian to early Permian. All these adakitic intrusions have distinctive geochemical-isotopic signatures with high Na and Al, high Sr, low Yb and Y, high Sr/Y and (La/Yb)N values, relatively high MgO contents and Mg numbers (Mg# = 41–70), high abundances of compatible elements (Cr = 1.66–46.30 ppm, Ni = 2.40–26.96 ppm), and positive high εHf (t) (+ 7.1 to + 15.6) and a TDM (Ma) range from 325 to 670 Ma. These adakitic intrusions were associated with essential Cu polymetallic mineralization in the Dananhu arc. The above chemical data and relations indicate that the processes of oceanic slab melting generated these adakitic rocks. Our new geochronological, geochemical and isotopic data, integrated with the geology of the Dananhu intra-oceanic arc, lead us to conclude that multiphase of hot/young oceanic crust subduction and melting generated the massive crustal growth in the Silurian–early Permian. Our results indicate that the magmas were derived by slab melting of hot/young oceanic crust, which was one of the most critical mechanisms of continental crustal growth in the Paleozoic accretionary orogen of the Altaids. [ABSTRACT FROM AUTHOR]

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Research on tight gas reservoirs in the eastern margin of the Ordos Basin, China, has recently become a hot spot. This paper mainly studies the reservoir characteristics of tight sandstone in the north-central area close to the provenance in eastern Linxing. Cast thin section, scanning electron microscopy, high-pressure mercury injection, and X-ray diffraction (XRD) were applied to discriminate the tight sandstone reservoir differences between the Permian Taiyuan and Shanxi formations in the study area. The results show that the deltaic tight sandstones in the Shanxi Formation are dominated by lithic quartz sandstone and lithic sandstone with an average porosity of 2.3% and permeability of 0.083 mD. The epicontinental tight sandstones in the Taiyuan Formation are mainly lithic sandstone and lithic quartz sandstone, with average porosities and permeabilities of 6.9% and 0.12 mD, respectively. The pore type is dominated by secondary dissolution pores, containing a small number of primary pores, and fractures are not developed. The capillary pressure curves of the Taiyuan Formation sandstone are mainly of low displacement pressure, high mercury saturation, and mercury withdrawal efficiency, while the Shanxi Formation sandstone is mainly of high displacement pressure, low mercury saturation, and withdrawal efficiency. The diagenetic evolution of sandstone in the Shanxi Formation is in meso-diagenesis stage A, and the Taiyuan Formation has entered meso-diagenesis stage B. The siliceous cement in the Taiyuan Formation sandstone enhanced the sandstone resistance to compaction and retained some residual intergranular pores. The pore types in the Shanxi Formation sandstone are all secondary pores, while secondary pores in the Taiyuan Formation sandstone account for approximately 90%. The results can be beneficial for tight gas production in the study area and similar basins. [ABSTRACT FROM AUTHOR]

International chronostratigraphic chart showing division of geological time and its numerical ages is regularly updated by the International Commission on Stratigraphy (ICS). The Slovak chronostratigraphic chart has not been updated since the end of the 1980s. This paper provides an overview of standard procedures for deriving Slovak terms; introduces Slovak translation of the latest version of International chronostratigraphic chart (v2021/10), and encourages the use of the new and/or updated chronostratigraphic terminology in all publications written in Slovak language. [ABSTRACT FROM AUTHOR]

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The Uralian foredeep is a classical marginal structure located on the foreland of the Late Paleozoic Uralian Orogen. It is subdivided into several depressions/sedimentation basins. This paper presents the analysis of the REE and Th distribution in the Middle Carboniferous and Lower Permian clay rocks of the Yuryuzan–Sylva Depression. This structure, like other depressions of the foredeep, is made up of diverse associations of the first sedimentation cycle clastic and clay rocks, which were formed during the orogen erosion. In the (La/Yb)N–Eu/Eu* and (La/Yb)N–Th diagrams, individual and average data points are confined to the field of bottom sediments of mouths of modern rivers draining volcanic provinces. This likely suggests a homogeneous composition of orogen provenance in the Carboniferous and Early Permian. [ABSTRACT FROM AUTHOR]