Journal of Asian Earth Sciences最新文献

{"title":"Origin and evolution of the Qiangtang block, northern Tibetan Plateau: New insights from detrital zircon U-Pb geochronology and Lu-Hf isotopic compositions","authors":"Min Liu ,&nbsp;Xijun Liu ,&nbsp;Hao Wu ,&nbsp;Yao Xiao ,&nbsp;Zhenglin Li ,&nbsp;Hongxia Yu","doi":"10.1016/j.jseaes.2025.106499","DOIUrl":"10.1016/j.jseaes.2025.106499","url":null,"abstract":"<div><div>Detrital zircon age spectra analysis offers insights into tectonic and sedimentary environments. In the Paleozoic sedimentary rocks of the Qiangtang block, northern Tibetan Plateau, we measured U-Pb ages of detrital zircons to elucidate the blocks tectonic-sedimentary evolution and its relationship to the Tethyan regime. Our findings reveal zircon age peaks at approximately ca. 2500, ca. 1600, ca. 970, and ca. 550 Ma, closely resembling the Cimmerian continent and exhibiting paleogeographic affinities with the northern margin of Gondwanan India. Our new data, alongside existing geological data, indicate distinct tectonic pathways for the North and South Qiangtang blocks since the Neoproterozoic as a result of Rodinia breakup. Our sedimentological and geochronological evidence implies that the Longmu Co-Shuanghu suture zone is an in situ ophiolite mélange formed by the closure of the Paleo-Tethyan Ocean.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"281 ","pages":"Article 106499"},"PeriodicalIF":2.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A hybrid symbolic learning approach for Ground-Motion model Development","authors":"Xianwei Liu ,&nbsp;Su Chen ,&nbsp;Xiaojun Li ,&nbsp;Lei Fu ,&nbsp;Fabrice Cotton","doi":"10.1016/j.jseaes.2025.106498","DOIUrl":"10.1016/j.jseaes.2025.106498","url":null,"abstract":"<div><div>In earthquake engineering, ground-motion models (GMMs) constitute a research hotspot. They can be utilized for earthquake risk assessment, earthquake zoning maps, and seismic structural design. This paper put forward a hybrid symbolic learning (HSL) method, which combines the symbolic regression (SR) method (Chen et al, 2023) and random effect regression (RER), to construct a robust GMM for predicting peak ground acceleration (PGA), peak ground velocity (PGV), and pseudo-spectral acceleration (PSA) with different periods (0.01 s-4 s). To evaluate the effectiveness of HSL, we compared its predictive capacity and variability with those of the empirical regression models (ERM) and the SR model. The results demonstrate that HSL accurately captures magnitude and distance saturation, anelastic attenuation, and linear site amplification. It also produces comparable results to the ERM and SR models. Calculation of between- and within-event residuals and their standard deviations indicates that the HSL can obtain lower standard deviations than the SR model. As a new version of the symbolic learning method, HSL not only inherits the advantages of concise and interpretable equations as well as flexible parameter expansion of the model that SR possessed. In comparison with SR, HSL achieves lower standard deviations. Furthermore, HSL incorporates random effects regression, which upgrades SR to a partially non-ergodic GMM, i.e. considering the influence of ground motion characteristics on the results beyond the fixed effects component.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"281 ","pages":"Article 106498"},"PeriodicalIF":2.7,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry of late Miocene-Pleistocene basalts from a coastal area of Vietnam: Implication for small-scale mantle heterogeneities","authors":"Nguyen Hoang ,&nbsp;Tran Thi Huong ,&nbsp;Ryuichi Shinjo ,&nbsp;Le Duc Anh ,&nbsp;Le Duc Luong ,&nbsp;Phan Dong Pha","doi":"10.1016/j.jseaes.2025.106488","DOIUrl":"10.1016/j.jseaes.2025.106488","url":null,"abstract":"<div><div>This study presents a comprehensive analysis of late Miocene to Pleistocene basaltic samples collected from a coastal area of central Vietnam. The investigation involved various analytical methods, including eruption age determination, petrographic examination, geochemical characterization, and assessment of Sr-Nd-Hf-Pb isotopic compositions. The sampled basalt types include silica-undersaturated mantle xenolith-bearing basalts (∼1 Ma), olivine-bearing phyric alkaline, and sub-alkaline basalts (∼7 to 1 Ma). These basalt varieties display typical intraplate geochemistry and a wide range of radiogenic isotope variations, indicating mantle and crustal influences. Interestingly, despite these variations, there is no evidence of crustal contamination. Spatial analysis reveals distinct differences in geochemical and isotopic signatures across the sampled areas, suggesting spatial controls on mantle source composition. The isotopic compositions align with depleted mantle (DM) and enriched mantle types 1 and 2 (EM1 and EM2), closely associating with the Indian DUPAL lead isotopic signature. The localized heterogeneity within the subcontinental lithospheric mantle (SCLM) is attributed to metasomatism from mafic lenses or magmatic melts from the asthenosphere. Furthermore, elemental characteristics resembling typical ocean island basalts and elevated Pb and Sr isotopic ratios suggest a potential involvement of ancient, subducted sediments within the mantle.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"281 ","pages":"Article 106488"},"PeriodicalIF":2.7,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A model for the Semail ophiolite thrust duplex and a late out-of-sequence thrust, northern Oman/UAE Mountains","authors":"Jim Leanderson ,&nbsp;Mohammed Y. Ali","doi":"10.1016/j.jseaes.2025.106486","DOIUrl":"10.1016/j.jseaes.2025.106486","url":null,"abstract":"<div><div>The Cenomanian Semail ophiolite was obducted onto the Mesozoic shelf and into the foreland basin mostly as a single thrust sheet along the serpentinized Semail thrust, except for a ca. 65 km long thrust duplex. At least six, ca. 5 km thick, foreland-facing thrust sheets were thrust from east to west along intensely serpentinized mantle-crust transition zone rocks. The late out-of-sequence Fizh and Hilti Block thrust sheets concealed the hinterland. Nevertheless, the conditions that formed the duplex can be postulated. A fault system, like the one mapped in this study, cut the Hawasina and Haybi Complexes and overlying ophiolite duplex during obduction, forming fault scarps that interrupted obduction of the ophiolite and triggered deformation and uplift in the hinterland. When the taper angle of the wedge became supercritical, breakback thrusting created the first thrust sheet. Repetition of thrusting is explained by a continuous increase in the width of the wedge as the height was reduced by erosion and, possibly removal of ca. 5 km of crustal rocks during each deformation-erosion/thrusting cycle. The cycles continued until the wedge’s width was too great for uplift to raise the taper angle to a supercritical value. A deeper décollement then formed in the upper Hawasina and lower Haybi, creating the late out-of-sequence Hawasina-Haybi thrust sheet emplaced over the eroded(?) thrust duplex. Serpentinization played a key role in thrusting of the ophiolite and in the formation of the duplex and may be a prerequisite for thrusting of ophiolites.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"281 ","pages":"Article 106486"},"PeriodicalIF":2.7,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Early Jurassic sedimentary records in the Central Lhasa Terrane, southern Tibet: Implications for the subduction and accretion of the Tethys Ocean","authors":"Bo Li ,&nbsp;Wen-Guang Yang ,&nbsp;Zhen Yang ,&nbsp;Li-Dong Zhu ,&nbsp;Nan Li ,&nbsp;Yao Zhong ,&nbsp;Long Xie ,&nbsp;Yuan-Jun Mai","doi":"10.1016/j.jseaes.2024.106475","DOIUrl":"10.1016/j.jseaes.2024.106475","url":null,"abstract":"<div><div>The properties of the Middle Triassic to Early Jurassic basin in the Central Lhasa terrane are highly important for defining the relationship between the Zhikong-Sumdo Ocean and the Yarlung-Tsangpo Ocean. The Jialapu Formation in the Mailonggang-Xionglai Basin in the Central Lhasa terrane was studied utilizing petrology, zircon U–Pb chronology, and chromium spinel electron probe analysis on the basis of geological investigations in the field. The Jialapu Formation is a set of volcanic-sedimentary strata that are mainly composed of medium- to coarse-grained clastic rocks, with andesite and dacitic tuff interlayers. The U-Pb age spectrum of detrital zircon shows a primary age peak of 220–180 Ma and secondary age peaks of 650–500 Ma and 1250–1050 Ma. After weighted averaging, the maximum depositional age (MDA) of the Jialapu Formation was 184 ± 1 Ma, indicating that the Jialapu Formation was deposited mainly in the Early Jurassic. The provenance analysis revealed that the clastic materials of the Jialapu Formation were derived mainly from accretionary arcs in the Zhikong-Soumdo accretionary complex, and partly from the Gangdese basement and coetaneous magmatic arcs in the southern margin. On the basis of the results of the regional geological survey, the Lower Jurassic Jialapu Formation exhibits a transitional property from the wedge-top basin to the back-arc basin, which is a basin resulting from the continuous subduction-accretion of the Zhikong-Sumdo Ocean and Yarlung-Tsangpo Ocean.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"281 ","pages":"Article 106475"},"PeriodicalIF":2.7,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis of Early Cretaceous volcanic rocks in the Tuoyun Basin, western Central Asian Orogenic Belt: Implications for crust–mantle interaction","authors":"Xin Zhou ,&nbsp;Zhiguo Cheng ,&nbsp;Yan Zhang ,&nbsp;Zhaochong Zhang","doi":"10.1016/j.jseaes.2025.106485","DOIUrl":"10.1016/j.jseaes.2025.106485","url":null,"abstract":"<div><div>The petrogenesis of continental intraplate basalts has been widely debated, primarily due to the uncertainties surrounding their thermal state and the role of recycled materials. Herein, we focus on the Early Cretaceous basalts from the Tuoyun Meso-Cenozoic volcanic basin, located in the western Central Asian Orogenic Belt. The samples are porphyritic, with phenocrysts predominantly composed of olivine, clinopyroxene, and plagioclase. Primitive mantle-normalized incompatible trace element patterns and chondrite-normalized rare earth element patterns show a strong ocean island basalt affinity. The Zn/Fe, Mn/Zn, and Fe/Mn ratios in olivine suggest a mixed source of peridotite and pyroxenite. This is further supported by trends in the whole-rock CaO–MgO compositions, FeO/MnO ratios (42.1–106.5), and FCKANTMS values (0.52–0.82). Additionally, the basalts exhibit significantly lighter Mg and heavier Zn isotopic compositions compared to the normal mantle, suggesting the involvement of recycled sedimentary carbonates. However, the olivine SIMS <em>in situ</em> oxygen isotopes show reveal that the Early Cretaceous basalts in the Tuoyun Basin have normal mantle oxygen isotope compositions, with δ¹⁸O_V-SMOW values ranging from 5.12 ‰ to 5.76 ‰. Moreover, the absence of typical carbonate signatures, such as negative anomalies in Zr, Hf, and Ti in the trace elemental spider diagram, indicates that carbonates did not participate in the partial melting of the mantle source. The decoupling of O and Mg–Zn isotopic signatures suggests that recycled carbonates may have decomposed during subduction. Overall, this study implies that the formation of intraplate basalts may be significantly influenced by recycled oceanic crust derived from ancient subducted slabs.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106485"},"PeriodicalIF":2.7,"publicationDate":"2025-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Generation of the 2022 earthquake swarm in intersection of four geological units in the seismic experimental Site, southwest China","authors":"Zhi Chen ,&nbsp;Hongyi He ,&nbsp;Kezhen Zuo ,&nbsp;Xiaoxia Liu ,&nbsp;Weiwei Wu ,&nbsp;Zihan Gao ,&nbsp;Zhaofei Liu ,&nbsp;Maoliang Zhang ,&nbsp;Lu-Lu Hao","doi":"10.1016/j.jseaes.2024.106477","DOIUrl":"10.1016/j.jseaes.2024.106477","url":null,"abstract":"<div><div>Three adjacent and successive earthquakes with magnitude over 6.0 in the seismic experimental site, southwest China in 2022 were investigated mainly based on multi-disciplinary observation data combined with regional geology. The abnormal variations of GPS horizontal velocity field and cross-fault baselines, seismic activity, and also fluids geochemistry presented strong cascade and pre-, post-, and co-seismic consistency, suggesting these events could belong to one sequence of earthquakes motivated by a lateral expansion of the Tibetan Plateau. Based on comprehensive analysis, the progressive regional localization of deformation and strain in the intersection of the four geological units, subjected to the lateral expansion of the Tibetan Plateau due to the remote action of the India-Eurasia collision, was unveiled to be the tectonic driver controlling the earthquake swarm, and a “south-north–south cascade” model was proposed for the generation process of the earthquake sequence. According to this model, the possible southward stain transfer in the southeastern margin of the Tibetan Plateau should be considered for potential strong earthquakes in the future. Although this study is special for the seismic experimental site, China, it could be inferred that similar processes might be probable elsewhere, thus, prospective transfer direction forecasting for coming seismic activity could be envisaged in some intersections of multiple geological units.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"281 ","pages":"Article 106477"},"PeriodicalIF":2.7,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143173340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The role of magma mixing in generating the Eocene potassic quartz syenite and mafic microgranular enclaves in the Ailao Shan–Red River shear zone, SW China: Insights from in situ Sr isotopes of plagioclase","authors":"Peng Song ,&nbsp;Fengbao Ji","doi":"10.1016/j.jseaes.2025.106487","DOIUrl":"10.1016/j.jseaes.2025.106487","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Understanding the origins of potassic rocks and mafic microgranular enclaves (MMEs) can provide important information for revealing their petrogenesis and regional tectonic evolution. We studied the Shilicun quartz syenite and MME and their plagioclases to elucidate their origins and investigate crust–mantle interactions in the southern Ailao Shan–Red River (ASRR) shear zone. Zircon U–Pb ages indicate the coeval formation of the quartz syenite and MME during the Eocene (approximately 35 Ma). The MMEs exhibit spheroidal shapes and contain acicular apatites, indicating that they represent globules of the coeval mafic melt injected into and partly assimilated by the felsic magmas. They are characterized by high contents of MgO (2.9–5.1 wt%), Ni (90–172 ppm), and Cr (105–180 ppm), as well as high Ba–Sr contents. The MME samples yield ε&lt;sub&gt;Hf&lt;/sub&gt;(t) values of –2.2 to + 0.5 and ε&lt;sub&gt;Nd&lt;/sub&gt;(t) values of –5.7 to –6.4, with high (&lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr)&lt;sub&gt;i&lt;/sub&gt; ratios of 0.70734–0.70758. These features suggest that they were derived from metasomatized enriched lithospheric mantle. The quartz syenites are characterized by high SiO&lt;sub&gt;2&lt;/sub&gt; (68.5–69.0 wt%) and Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; (15.6–16.2 wt%) contents, Sr/Y ratios (40.6–73.3), and low MgO, Cr, and Ni contents, as well as low Mg# values. They have a low (&lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr)&lt;sub&gt;i&lt;/sub&gt; ratio of 0.70716 and an ε&lt;sub&gt;Nd&lt;/sub&gt;(t) value of –4.5. Type I plagioclase from the quartz syenite exhibits reverse zoning and shows sieve textures and resorption surfaces in the core, indicative of rapid cooling and disequilibrium mixing between mafic and felsic magmas. It has significantly different (&lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr)&lt;sub&gt;i&lt;/sub&gt; &lt;!--&gt;ratios (0.70666–0.70726) among the core (0.70666–0.70674), mantle (0.70692–0.70726), and rim (0.70714–0.70715), with the An content increasing from the core (An&lt;sub&gt;10–13&lt;/sub&gt;) to the mantle (An&lt;sub&gt;14–15&lt;/sub&gt;) and then decreasing to the rim (An&lt;sub&gt;9–10&lt;/sub&gt;). Type II plagioclase exhibits a normal zoning texture, with the An content decreasing from the core (An&lt;sub&gt;13–15&lt;/sub&gt;) to the rim (An&lt;sub&gt;12–13&lt;/sub&gt;). It has a small variation in (&lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr)&lt;sub&gt;i&lt;/sub&gt; ratios from 0.70708 in the core to 0.70722 at the rim. Type III plagioclase from the MME is normally zoned and has high (&lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr)&lt;sub&gt;i&lt;/sub&gt; ratios of 0.70719–0.70742, with the An content decreasing from the core (An&lt;sub&gt;17&lt;/sub&gt;) to the rim (An&lt;sub&gt;8&lt;/sub&gt;). The large variations in the Sr isotopes of different types of plagioclases record magma mixing processes. Therefore, we suggest that the quartz syenites were formed by partial melting of thickened lower crust, with the involvement of mantle-derived melts that are characterized by high (&lt;sup&gt;87&lt;/sup&gt;Sr/&lt;sup&gt;86&lt;/sup&gt;Sr)&lt;sub&gt;i&lt;/sub&gt; ratios. We propose that partial removal of the lower continental lithospheric mantle induced asthenosphere upwelling, which triggered ","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"281 ","pages":"Article 106487"},"PeriodicalIF":2.7,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143174428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Origin and distribution of Cambrian to Ordovician weathering crust dolostone reservoirs in the Ordos Basin, NW China","authors":"Chun Wu ,&nbsp;Bo Liu ,&nbsp;Liubin Wei ,&nbsp;Xinshe Liu ,&nbsp;Jin Lai ,&nbsp;Kaibo Shi ,&nbsp;Feifan Lu ,&nbsp;Qing He ,&nbsp;Senran Chen","doi":"10.1016/j.jseaes.2024.106476","DOIUrl":"10.1016/j.jseaes.2024.106476","url":null,"abstract":"<div><div>Recent advances in natural gas exploration have led to notable breakthroughs in weathering crust dolostone reservoirs. The Huaiyuan Epeirogeny, which occurred from the Cambrian to Ordovician periods, contributed to the formation of weathering crust dolostones in the southwestern Ordos Basin, NW China. A combination of core analysis, thin section microscopy, scanning electron microscopy, and conventional and image logs has been employed to characterize the karst features present in these reservoirs. Lithologies are classified based on crystalline size, with pore spaces including isolated pores, cavities, and fractures. Five distinct image log assemblages have been identified to describe the karst features. Vertically, the weathering crust is divided into four zones: the surface karst zone, the vertical vadose zone, the horizontal underflow zone, and the deep slow flow zone. These vertical zonations are predicted using image logs and conventional well logs. The majority of gas-producing intervals are located in the vertical vadose zone. The cavity and fracture systems in the surface zone are distributed locally, while fractures in the vertical vadose zone, especially those connected to vugs, considerably enhance hydrocarbon productivity. Based on these findings, a karstification model for the weathering crust has been developed, offering valuable insights into the karst features of these reservoirs. This research provides a reference for future oil and gas exploration in weathering crust dolostone reservoirs in similar basins.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106476"},"PeriodicalIF":2.7,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrological and geochemical characteristics of Ordovician cherts in the Qasim Formation, NW Saudi Arabia: Understanding the roles of biogenic and volcanic activities","authors":"Abdulwahab M. Bello ,&nbsp;Abduljamiu O. Amao ,&nbsp;Ardiansyah I. Koeshidayatullah ,&nbsp;Mahmoud Alnazghah ,&nbsp;Mohammad A. Alrowaie ,&nbsp;Adhipa Herlambang ,&nbsp;Khalid Al-Ramadan","doi":"10.1016/j.jseaes.2024.106483","DOIUrl":"10.1016/j.jseaes.2024.106483","url":null,"abstract":"<div><div>The Upper Ordovician Qasim Formation features bedded cherts with mudstone interbeds, which are overlain by Tertiary volcanic rocks. The origin and formation conditions of the cherts are almost completely unknown. To address these, this study employed thin-section petrography, XRF analysis, REE geochemistry, SEM analysis, and stable oxygen isotopes. Results of the study indicate that the cherts are primarily biogenic, derived from siliceous sponges, with contributions from terrestrial and river sources. Silica from marine upwelling and terrestrial sources enhanced biogenic activity, leading to the formation of the chert. Ratios of Si/(Si + Al + Fe) and Al/(Al + Fe + Mn) support a biogenic silica origin, while REEs suggest formation under oxic marine conditions (Ce/Ce* anomaly 0.3–1.0, avg. 0.7). The cherts also show an average Y/Ho value of 33.3, indicating marine influence with freshwater input. Diagenesis played a vital role in the formation of the cherts, with microcrystalline quartz replacing carbonate bioclasts and subsequently partly recrystallizing into blocky mega-quartz near chert-basalt contact. The microquartz cherts have δ ¹⁸O values of 26.7 to 33.7 ‰ (± 0.6 ‰), corresponding to formation temperatures of approximately 14 to 45 °C (avg. 38 °C; ±3 °C), whereas the mega-quartz chert has a δ ¹⁸O of 20.4 ‰ (±0.6 ‰), reflecting a formation temperature of approximately 115 ± 5 °C). These oxygen isotope values and temperatures reveal that the microquartz chert formed in cooler, shallow marine conditions, while the megaquartz chert was affected by a significant thermal event at the contact with the Tertiary basalt emplaced over the chert layers. These findings provide insights into paleoenvironmental conditions, thermal history, and the impact of later volcanic activity on chert recrystallization.</div></div>","PeriodicalId":50253,"journal":{"name":"Journal of Asian Earth Sciences","volume":"280 ","pages":"Article 106483"},"PeriodicalIF":2.7,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143097055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}