0 INTRODUCTION Changbaishan volcanism,located on the border of China and North Korea,has been a subject of extensive research due to its unique geological features and active volcanic history(Wan et al.,2024).Two prim...0 INTRODUCTION Changbaishan volcanism,located on the border of China and North Korea,has been a subject of extensive research due to its unique geological features and active volcanic history(Wan et al.,2024).Two primary models have been proposed to explain the origin of Changbaishan volcanism(CV).展开更多
The Ordos Basin was recognized as the earliest terrestrial aquatic ecosystem to recover following Permian-Triassic mass extinction,significantly contributing to organic carbon sequestration during the early Mesozoic e...The Ordos Basin was recognized as the earliest terrestrial aquatic ecosystem to recover following Permian-Triassic mass extinction,significantly contributing to organic carbon sequestration during the early Mesozoic era.Volcanic activity has increased the organic carbon burial capacity of the third submember of Ch7(Ch7_(3))within this basin,although it has both positive and negative effects on organic carbon burial.In this study,we quantitatively characterized the organic carbon burial process by calculating the organic carbon accumulation rate(OCAR)and proposed an optimal sedimentary model influenced by volcanic activity.We conducted time series analysis on gamma ray(GR)data from Ch7_(3) to determine sedimentation rates(SRs) while measuring the density of each sample via hydrostatic methods.By integrating these measurements with the total organic carbon(TOC)content,we established a dynamic OCAR for Ch7_(3)(χ=0.68 g/(cm^(2)·kyr))and estimated that it sequestered 0.27 Tt of organic carbon.Our findings indicate that the OCAR under eunixic conditions(χ=1.02 g/(cm^(2)·kyr))is 2.49 times greater than that under ferruginous conditions(χ=0.41 g/(cm^(2)·kyr)).The geochemical identification fingerprints of volcanism suggest that the top of Ch7_(3) is influenced by volcanoes of appropriate intensity.In this sedimentary model,the dilution of organic matter(OM)by rapidly deposited volcanic ash is relatively low.Additionally,the cumulative effect of chemical weathering intensity due to volcanic activity leads to the input of nutrients from continental sources into the lake basin.This process promotes increased productivity,resulting in a significant increase in the OCAR(χ=0.76 g/(cm^(2)·kyr)).This study provides new insights for dynamically assessing the impact of geological events on the OCAR.展开更多
A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associate...A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associated with both passive and active mechanisms,but it remains a source of ongoing debate among geoscientists.Here,we show that seismic whole-mantle tomography models consistently identify two extensive low-velocity anomalies beneath the Canary Islands(CEAA)and Western-Central Europe(ECRA)at mid-mantle depths,merging near the core-mantle boundary.These low-velocity features are interpreted as two connected broad plumes originating from the top of the African LLSVP,likely feeding diapir-like upwellings in the upper mantle.The CEAA rises vertically,whereas the ECRA is tilted and dissipates at mantle transition zone depths,possibly due to the interaction with the cold Alpine subducted slab,which hinders its continuity at shallower depths.While plate-boundary forces are considered the primary drivers of rifting,the hypothesis that deep mantle plumes play a role in generating volcanic activity provides a compelling explanation for the European rift-related alkaline volcanism,supported by geological,geophysical,and geochemical evidence.展开更多
The latest Carboniferous to lower Permian volcanism of the southern Variscides in Sardinia developed in a regional continental transpressive and subsequent transtensile tectonic regime.Volcanism produced a wide range ...The latest Carboniferous to lower Permian volcanism of the southern Variscides in Sardinia developed in a regional continental transpressive and subsequent transtensile tectonic regime.Volcanism produced a wide range of intermediate-silicic magmas including medium-to high-K calc-alkaline andesites,dacites,and rhyolites.A thick late Palaeozoic succession is well exposed in the four most representative Sardinian continental basins(Nurra,Perdasdefogu,Escalaplano,and Seui-Seulo),and contains substantial stratigraphic,geochemical,and geochronological evidence of the area's complex geological evolution from the latest Carboniferous to the beginning of the Triassic.Based on major and trace element data and LA-ICP-MS U-Pb zircon dating,it is possible to reconstruct the timing of postVariscan volcanism.This volcanism records active tectonism between the latest Carboniferous and Permian,and post-dates the unroofing and erosion of nappes in this segment of the southern Variscides.In particular,igneous zircon grains from calc-alkaline silicic volcanic rocks yielded ages between299±1 and 288±3 Ma,thereby constraining the development of continental strike-slip faulting from south(Escalaplano Basin)to north(Nurra Basin).Notably,andesites emplaced in medium-grade metamorphic basement(Mt.Cobingius,Ogliastra)show a cluster of older ages at 332±12 Ma.Despite the large uncertainty,this age constrains the onset of igneous activity in the mid-crust.These new radiometric ages constitute:(1)a consistent dataset for different volcanic events;(2)a precise chronostratigraphic constraint which fits well with the biostratigraphic data and(3)insights into the plate reorganization between Laurussia and Gondwana during the late Palaeozoic evolution of the Variscan chain.展开更多
A growing body of evidence shows that volcanism near the Permian-Triassic boundary（PTB） may be crucial in triggering the Permian–Triassic（P–Tr） mass extinction. Thus, the ash beds near the PTB in South China may...A growing body of evidence shows that volcanism near the Permian-Triassic boundary（PTB） may be crucial in triggering the Permian–Triassic（P–Tr） mass extinction. Thus, the ash beds near the PTB in South China may carry information on this event. Three volcanic ash layers, altered to clay, outcropped in the PTB beds in Zunyi Section, Guizhou Province, Southwest China. The U-Pb ages, trace elements, and Hf-isotope compositions of zircon grains from these three ash beds were analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons are mainly magmatic in origin（241-279 Ma） except for two inherited/xenocrystic zircons（939 and 2 325 Ma）. The ages of these magmatic zircons indicate three episodes of magmatism which occurred around the MiddleLate Permian boundary（-261.5 Ma, MLPB）, the Wuchiapingian-Changhsingian boundary（-254.5 Ma, WCB）, and the PTB（-250.5 Ma）, respectively. The first two episodes of magmatism near the MLPB and WCB may be attributed to magmatic inheritance or re-deposition. All magmatic zircons share similar trace-element and Hf-isotope compositions. They have Y, Hf, Th and U contents and Nb/Ta ratios are typical of zircons from silicic calc-alkaline magmas. These zircons also exhibit enriched Hf-isotope compositions with _（εHf）（t） values of-11.4 to ＋0.2, which suggests that the three magmatic episodes involved melting of the continental crust. The more enriched Hf-isotope composition （_（εHf）（t）=-11.4--4.8） of Bed ZY13（-250.5 Ma） implies more input of ancient crustal material in the magma. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggest that these three episodes of magmatism may take place along the convergent continent margin in or near southwestern South China as a result of the closure of the Palaeo-Tethys Ocean.展开更多
Some of the islets in the eastern Beibu Gulf are covered by Quaternary volcano strata. The rock samples from these islets mainly consist of quartz tholeiites （at Shenjiandao）, olivine tholeiites （at Linshidao and X...Some of the islets in the eastern Beibu Gulf are covered by Quaternary volcano strata. The rock samples from these islets mainly consist of quartz tholeiites （at Shenjiandao）, olivine tholeiites （at Linshidao and Xieyang- dao） and alkali basalts （at Yangpubi and Jianshidao）, and basically represent four periods of the Quaternary volcanism of Hainan Island and its adjacent regions. Except for the samples from Shenjiandao, most of the Quaternary volcanics of these islets belong to alkali magma series. The trace element characteristics of all of these samples show they are OIB （oceanic island basalt） -like, which implies that their deep geodynamic setting may be related to a mantle plume. The Sr-Nd-Pb isotopic compositions show that the mantle source beneath the Quaternary strata can be regarded as a result of binary mixing between a depleted, DMM （de- pleted MORB mantle）-like source and an enriched mantle type 2 （EM2）. The EM2 may be originated from the Hainan mantle plume, and has been metasomatized by carbonaceous fluids released from ancient re- cycled oceanic crust at an asthenospheric mantle level. These features, together with typical trace element ratios, reflect that the parent magma was not subjected to crustal contamination during its ascent to the surface. This study provides further petrological and geochemical evidence for the existence of the Hainan mantle plume.展开更多
This paper discusses the clayrocks widespread at the Permian-Triassic boundary, which are mostly of volcanic origin. Volcanogenetic textures, structures and minerals such as high-temperature quartz are found in clayro...This paper discusses the clayrocks widespread at the Permian-Triassic boundary, which are mostly of volcanic origin. Volcanogenetic textures, structures and minerals such as high-temperature quartz are found in clayrocks at the Permian-Triassic boundary in many places. Thousands of microspherules have been collected from the Boundary clayrocks, many of which exhibit the typical features of the process from melting to cooling and solidification. indicating that they were formed by volcanic eruption or extraterrestrial impact. Volcanic effects on the Permian-Triassic mass extinction may be reflected in conodonts, algae and ammonoids. The Boundary clayrocks are found in many Permian-Triassic sections along the coast of Tethys. Their orighin remains to be studied.展开更多
Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposi...Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposits at the southern margin of the Junggar Basin,based on petrology,geochronology and geochemical analyses.The results show that a massive collapse of unstable sediments from the slope was triggered by volcanism,resulting in the formation of slumping gravity flows.The occurrence of volcanic beds in the slump deposits confirm that synchronous volcanism likely affected sediment instability,triggering gravity flows.The Th/Yb,Ta/Yb and Th/Ta elemental ratios,U-Pb ages of detrital zircons and paleocurrent directions indicate that the North Tianshan(NTS)island arc represents the provenance of the Qianxia Formation.Moreover,statistical data on the pyroclastic components in the gravity flow deposits reveal an intensity index of volcanism,indicating that volcanism is strongly related to gravity flow deposits,especially in terms of the type and distribution of the deposits.A model for volcanically-triggered deep-water gravity flow deposits is established,in order to provide a more in-depth understanding of the co-evolution of volcanism and gravity flow deposits within the depositional setting of the late Paleozoic NTS oceanic subduction margin in the Junggar Basin.展开更多
The rock series, rock types and Sr-Nd isotopic dating of the Cenozoicvolcanic rocks in the South China Sea are similar to those in its vicinity. On the basis of thespreading age of the South China Sea, the Cenozoic vo...The rock series, rock types and Sr-Nd isotopic dating of the Cenozoicvolcanic rocks in the South China Sea are similar to those in its vicinity. On the basis of thespreading age of the South China Sea, the Cenozoic volcanic rocks are divided into three stages: thepre-spreading stage, the spreading stage and the post-spreading stage. The deep processcharacteristics of the asthenosphere and lithosphere may be inferred from the study on primarybasaltic magma. The top layers of the asthenosphere both in the spreading stage and in thepre-spreading stage are closer to the earth surface than that in the post-spreading stage. From thepre-spreading stage to the spreading stage, the top layer of the asthenosphere decreased in depth,while the amount of interstitial partial melts increased. The evolution of the primary basalticmagma shows a progressive evolution sequence of the rifting volcanism and a faster lithosphericspreading velocity. From the spreading stage to the post-spreading stage, the top layer of theasthenosphere gradually increased in depth, but the amount of interstitial partial melts decreased.The evolution of primary basaltic magma shows a retrogressive evolution sequence of the riftingvolcanism and a gradual decrease in the lithospheric spreading velocity. The depth recognized by thestudy on the Cenozoic volcanism demonstrates the deep environment for the formation and evolutionof the South China Sea.展开更多
Sanjiang area in Southwestern China is tectonically situated at the east end of Himalaya-Tethys tectonic domain and at the conjunction of Tethyan Mountain Chain and Circum-Pacific Mountain Chain. It is one of the key ...Sanjiang area in Southwestern China is tectonically situated at the east end of Himalaya-Tethys tectonic domain and at the conjunction of Tethyan Mountain Chain and Circum-Pacific Mountain Chain. It is one of the key areas to understand the global tectonics and also one of gigantic metallogenic provinces in China and even in the world . Volcanism had occurred during the period of time from Proterozoic to Cenozoic . The most important and active periods of volcanism , however , are Carboniferous , Permian and Triassic . The pattern of spatial distribution of Sanjiang volcanic rocks and ophiolites can essentially be described as that several intra - continental micro-massif volcanic districts are respectively sandwiched between each two of four coupling ophioh'te - arc volcanic belts , which are successively from west to east : Dingqing - Nujiang belt , Lancangjiang belt , Jinshajiang belt and Ganzi-Litang belt . Four tectono - magma tic types of volcanic rocks have been rec-ognized in Sanjiang area as follows: mid -ocean- ridge/ para - mid - ocean - ridge type , arc type , collision type and intra - continent type . The petrotectonic assemblages within suture zones , such as oceanic assemblage , subduction - related assemblage , collision - related assemblage etc ., have been paid more attention to because of their significant importance in reconstruction of the history of Sanjiang Tethyan orogenic belt and plate tectonics .Couph'ng ophiolite - arc volcanic belt, para-mid - ocean - ridge volcanism and volcanic rocks, post -collision arc volcanism and volcanic rocks and tensional volcanic arc are newly defined in the present work . These new facts and concepts will be greatly beneficial to understanding the history of Sanjiang Tethyan plate tectonics and the complexity of the volcanism in orogenic belts and of the evolution of the continental lithosphere . A preliminary model of the evolution of Sanjiang Tethys under petrotectonic constraints was presented . It consists of the following four successive stages : (1) Late Paleozoic ocean spreading - dominant stage , (2 ) Early Mesozoic subduction and closing - dominant stage , (3) Late Mesozoic collisional orogenic stage characterized by crust shortening and compression , and (4 ) Cenozoic intra - continent orogenic stage characterized by crustal slipping - out and strike - slipping .展开更多
This paper is concentrated on Cenozoic volcanism and geothermal resources in Northeast China. There are a lot of Cenozoic volcanoes, a large area of volcanic rocks, a large number of active faults and rich geothermal ...This paper is concentrated on Cenozoic volcanism and geothermal resources in Northeast China. There are a lot of Cenozoic volcanoes, a large area of volcanic rocks, a large number of active faults and rich geothermal resources in Northeast China. The time and space characteristics of Cenozoic volcanism and the space distribution characters of hot springs and high geothermal flux regions in Northeast China are described and discussed on the basis of geological, geothermal, drilling and volcanological data. It is revealed that the hot springs and high geothermal flux regions are related to the Cenozoic volcanism, rifting and faulting in Northeast China. It is especially emphasized that the hot springs and high geothermal anomaly areas are controlled by active deep faults. It is proposed that the Cenozoic volcanism regions, rift basins, active fault belts, activated plate suture zones and large earthquake occurrence points are the best areas for prospecting geothermal resources. The geothermal resources in younger volcanic zones are richer than those in older volcanic belts. The hot springs and active or activated faults might be a very good clue for looking for geothermal resources.展开更多
This paper summarizes the history of tectono magmatic evolution, the types and backgrounds of mineralization prior to the orogenic period of North Qilian Mountains. It points out that: during the process of Paleozoic...This paper summarizes the history of tectono magmatic evolution, the types and backgrounds of mineralization prior to the orogenic period of North Qilian Mountains. It points out that: during the process of Paleozoic ocean basin opening and closing, the large scale marine volcanism and massive sulfide deposits controlled by sea floor hydrothermal circulation systems are the two sharpest features in the geological developing history of the orogenic belt, which are also the most two important aspects related to each other and should be given a special attention in the geological studies in the region.展开更多
Oceanic plateaus are large igneous provinces in the oceans,created by massive underwater eruptions,but their late-stage volcanism is poorly understood.With the addition of recent high-quality bathymetric data to exist...Oceanic plateaus are large igneous provinces in the oceans,created by massive underwater eruptions,but their late-stage volcanism is poorly understood.With the addition of recent high-quality bathymetric data to existing data,286 secondary cones were discovered over Shatsky Rise oceanic plateau.These cones with steeper flank slopes(mean 6.1°±4.4°)and smaller sizes(102–1923 m in height)are morphologically distinct from the plateau,and they are thought to have formed after the main volcanic episodes.Cone height and characteristic height(420 m)are close to seamounts in the Pacific Ocean,whereas greater than those in the Atlantic Ocean.Mean flatness of Shatsky Rise’s cones(0.25±0.20)are similar to that of seamounts in both Pacific and Atlantic Oceans,but notably density in cone distribution(0.56 km^-3)and their mean slope are significantly lower than those of seamounts in the two oceans.Lower slopes of secondary cones within Shatsky Rise may be explained by higher effusion rates of remaining magma.Although cone formation was expected to have a link to rifting by seafloor spreading,weak relationship between cone orientation and magnetic anomaly pattern implies that the expectation is negative.Moreover,weak correlation between the cone height and depth indicates it is not true that volcanic cones grow taller when they occur closer to the massif summits with thicker oceanic crust,which was suggested as the increase in hydraulic pressure.Cone height and flatness are also not strongly related,implying that remaining magma supply was too limited to foster the cones to critical height.展开更多
Intraplate processes,such as continental surface uplift and intraplate volcanism,are enigmatic and the underlying mechanisms responsible are not fully understood.Central Mongolia is an ideal natural laboratory for stu...Intraplate processes,such as continental surface uplift and intraplate volcanism,are enigmatic and the underlying mechanisms responsible are not fully understood.Central Mongolia is an ideal natural laboratory for studying such processes because of its location in the continental interior far from tectonic plate boundaries.展开更多
The Ordovician marine volcanic rocks in the north Qilian mountains are discussed in this paper. According to geology, petrotectonic assemblage and geochemistry, a new model about plate tectonic evolution of the north...The Ordovician marine volcanic rocks in the north Qilian mountains are discussed in this paper. According to geology, petrotectonic assemblage and geochemistry, a new model about plate tectonic evolution of the north Qilian mountains is set up. The Ordovician marine volcanic rocks in the north Qilian mountains which characterized by the geological features of tectonic melange of continent to continent collision underwent complicated tectonic movement, and can be classified into three main kinds of petrotectonic assemblages. During Ordovician period, north Qilian area was a polyisland ocean which consisted of three ocean basins separated by the middle microcontinental blocks.展开更多
The principle prerequisite for the formation of a volcano is the generation of a channel for magma transportation. There is little research on the deep mechanical mechanism for the formation of a magma transportation ...The principle prerequisite for the formation of a volcano is the generation of a channel for magma transportation. There is little research on the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan plateau. Based on the subcrustal mantle convectiongenerated stress field inversed by gravity anomalies, together with its relationship to the Cenozoic volcanism in the plateau, and the mechanism of crustal fracture formation, as well as the numerical results of the evolution of mantle convection beneath the plateau, this paper investigates the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan plateau. There are two significant extensional convection-generated stress zones beneath the plateau, in which the volcanic rocks in the central and northern parts of the plateau are distributed. The Linzizong volcanism in southern Tibet correlates the upwelling mantle flow prior to the India-Asia collision or during the early stage of the collision. The magnitude of the stress is - 100 MPa, which is the same order of force that causes crustal fractures. The evidence implies that the mantle convection-generated stress is one of the principle causes of crustal fractures, and furthermore, the formation of the magma transportation channel in the Tibetan plateau.展开更多
The Palaeoproterozoic-Mesoproterozoic transition （ -1600 Ma） is a significant event in the Earth history as a global thermal perturbation affected the pre-1600 Ma landmasses. Like other cratonic blocks of the world,...The Palaeoproterozoic-Mesoproterozoic transition （ -1600 Ma） is a significant event in the Earth history as a global thermal perturbation affected the pre-1600 Ma landmasses. Like other cratonic blocks of the world, lithospheric thinning, sedimentation, magmatism, metamorphism and crustal melting/anatexis are associated with this significant geological event in the Singhbhum cratonic province of India. This paper is a review of sedimentological, magmatic and tectono-thermal events in the Singhbhum craton at 1600 Ma. The Palaeo-Mesoproterozoic sedimentation and volcanism in the Singhbhum craton took place in a terrestrial intracontinental rift setting. The available geochronological data are indicative of late Palaeoproterozoic to Neoproterozoic tectono-thermal events in the Chhotanagpur Granite Gneissic Complex （CGGC）, an east-west trending arcuate belt of granite gneisses, migmatites and metasedi- mentary rocks. A detailed multidisciplinary geo-scientific investigation of the Dalma volcanic belt and the area to its north （Chandil Formation） and further north in CGGC will enable us to constrain the extant surface processes and crust-mantle interactions, the collision events between the North and South Indian cratonic blocks, and the position of India in the Columbia supercontinent.展开更多
This paper deals with indirect effects of major impacting throughout the Early Paleozoic resp. with those of super plume activity during the Early Cretaceous, both applied to the siliciclastic series of Jordan deposit...This paper deals with indirect effects of major impacting throughout the Early Paleozoic resp. with those of super plume activity during the Early Cretaceous, both applied to the siliciclastic series of Jordan deposited on the Arabian Platform, Arabian Plate. Its focus is mainly directed on gases released by both processes (CO2, SO2, NOx, HCl, HF) and the relating acids, challenged by experiments and microscopic analysis of grain mounts and thin sections that reveal chemical instability of quartz and ultrastable heavy minerals (i.e. tourmaline) under high acidity (pH °C - 90°C). According to Lopatin’s Time/Temperatur-Index the Lower Cambrian reached the onset of hydrocarbon generation (liquid window) during the Lower Early Cretaceous. Unstable heavy minerals (apatite, garnet, hornblende, epidote, zoisite/clinozoisite) are generally absent in quartz arenites while in arkosic sandstones of marine environment carbonate cement and primary clay minerals (illite) provide conservation. As known since the eighties, the K/T-event’s indirect effects had global influence on Earth’s surface sediments and atmospheric chemistry by wildfires, hot whirl storms, acidic “sturz rain”, dust, soot, darkness, loss of photosynthesis, toxic metals, gases and relating acids. All of them are here concerned and applied to major impacting throughout the Early Paleozoic using the impact data of Price (2001);while superplume volcanism during Cretaceous led to the opening of the South Atlantic accompanied by the cyclic outflow of the Para?a/Etendeka Flood Basalts and relating gases in a gigantic scale (137 - 127 Ma). Assuming that the gases cause similar global effects on Earth’s surface sediments, an according result may be expected in form of quartz arenites and their sequence-analytical patterns (cyclic SBs, MFSs).*展开更多
Eruptions of lava flows of Deccan large igneous province straddled the Cretaceous-Palaeogene boundary (K-Pg). Sediments associated at different stratigraphic levels within the lava piles of Deccan volcanic sequences (...Eruptions of lava flows of Deccan large igneous province straddled the Cretaceous-Palaeogene boundary (K-Pg). Sediments associated at different stratigraphic levels within the lava piles of Deccan volcanic sequences (DVS) are mainly terrestrial. We studied the sediments of Eastern and Central Deccan Volcanic Province, and the Malwa Plateau for tracking changes in reptilian tetrapods across the volcanism. The reptiles are mainly represented by abelisaurid-titanosaurid dinosaurs, Alethinophidia madtsoiia snakes, Notosuchian crocodylomorph Simosuchus, bothremydid Kurmademydinae turtles and Anguimorph and Scincomorphs lizards. The evidences suggest that the non-avian dinosaurs were adversely affected by the arrival of the first volcanic flows locally in the province either within C30N or C29R Maastrichtian. The abelisaurid theropods became extinct whereas a single or two species of titanosauriforme dinosaurs survived but eventually became extinct at least 350 ky before the K-Pg boundary with increasing volcanism. The madtsooid snakes and crocodylimorphs were also adversely affected with decline in their diversity and abundance, whereas the Bothremydid turtles survived the initial onslaught of Deccan volcanism and continued across the K-Pg boundary.展开更多
The article presents new views on volcanism and earthquakes. The problem of the scientific basis for the interpretation of geotectonic theories was discussed. The interpretation of the mantle plume phenomenon accordin...The article presents new views on volcanism and earthquakes. The problem of the scientific basis for the interpretation of geotectonic theories was discussed. The interpretation of the mantle plume phenomenon according to the theory of expansion and the theory of primal forces of nature is presented. The heat source in the Earth’s core <span style="font-family:;" "="">is</span><span style="font-family:;" "=""> thermonuclear reactions. The cause of earthquakes is not collisions of lithospheric plates, but plasma eruptions. The stre<span>sses in the rock mass, causing global fractures, arise due to the increase in the size of nuclides in the process of plasma recombination. The oldest ba</span>salts that make up the oceanic plates remain invariably along the shores of continents.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "="">The widespread view of the subduction of lithospheric plates and vertical convection cells of rock matter should be regarded as </span><span style="font-family:;" "="">a </span><span style="font-family:;" "="">scientific fiction.</span>展开更多
基金support from the National Natural Science Foundation of China(No.42276049)。
文摘0 INTRODUCTION Changbaishan volcanism,located on the border of China and North Korea,has been a subject of extensive research due to its unique geological features and active volcanic history(Wan et al.,2024).Two primary models have been proposed to explain the origin of Changbaishan volcanism(CV).
基金supported by the National Natural Science Foundation of China(Grant No.42090025)the National Key R&D Program of China(2023YFF0806200).
文摘The Ordos Basin was recognized as the earliest terrestrial aquatic ecosystem to recover following Permian-Triassic mass extinction,significantly contributing to organic carbon sequestration during the early Mesozoic era.Volcanic activity has increased the organic carbon burial capacity of the third submember of Ch7(Ch7_(3))within this basin,although it has both positive and negative effects on organic carbon burial.In this study,we quantitatively characterized the organic carbon burial process by calculating the organic carbon accumulation rate(OCAR)and proposed an optimal sedimentary model influenced by volcanic activity.We conducted time series analysis on gamma ray(GR)data from Ch7_(3) to determine sedimentation rates(SRs) while measuring the density of each sample via hydrostatic methods.By integrating these measurements with the total organic carbon(TOC)content,we established a dynamic OCAR for Ch7_(3)(χ=0.68 g/(cm^(2)·kyr))and estimated that it sequestered 0.27 Tt of organic carbon.Our findings indicate that the OCAR under eunixic conditions(χ=1.02 g/(cm^(2)·kyr))is 2.49 times greater than that under ferruginous conditions(χ=0.41 g/(cm^(2)·kyr)).The geochemical identification fingerprints of volcanism suggest that the top of Ch7_(3) is influenced by volcanoes of appropriate intensity.In this sedimentary model,the dilution of organic matter(OM)by rapidly deposited volcanic ash is relatively low.Additionally,the cumulative effect of chemical weathering intensity due to volcanic activity leads to the input of nutrients from continental sources into the lake basin.This process promotes increased productivity,resulting in a significant increase in the OCAR(χ=0.76 g/(cm^(2)·kyr)).This study provides new insights for dynamically assessing the impact of geological events on the OCAR.
基金supported by grant D86-RALMI23CIVIE_01 awarded by the Italian Ministry of University and Research under the Program for Young Researchers“Rita Levi Montalcini”.
文摘A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associated with both passive and active mechanisms,but it remains a source of ongoing debate among geoscientists.Here,we show that seismic whole-mantle tomography models consistently identify two extensive low-velocity anomalies beneath the Canary Islands(CEAA)and Western-Central Europe(ECRA)at mid-mantle depths,merging near the core-mantle boundary.These low-velocity features are interpreted as two connected broad plumes originating from the top of the African LLSVP,likely feeding diapir-like upwellings in the upper mantle.The CEAA rises vertically,whereas the ECRA is tilted and dissipates at mantle transition zone depths,possibly due to the interaction with the cold Alpine subducted slab,which hinders its continuity at shallower depths.While plate-boundary forces are considered the primary drivers of rifting,the hypothesis that deep mantle plumes play a role in generating volcanic activity provides a compelling explanation for the European rift-related alkaline volcanism,supported by geological,geophysical,and geochemical evidence.
基金substantially supported by the University of Genova(PRA 2012 grant to Laura Gaggero)University of Pavia(PRIN 2008 to Ausonio Ronchi)
文摘The latest Carboniferous to lower Permian volcanism of the southern Variscides in Sardinia developed in a regional continental transpressive and subsequent transtensile tectonic regime.Volcanism produced a wide range of intermediate-silicic magmas including medium-to high-K calc-alkaline andesites,dacites,and rhyolites.A thick late Palaeozoic succession is well exposed in the four most representative Sardinian continental basins(Nurra,Perdasdefogu,Escalaplano,and Seui-Seulo),and contains substantial stratigraphic,geochemical,and geochronological evidence of the area's complex geological evolution from the latest Carboniferous to the beginning of the Triassic.Based on major and trace element data and LA-ICP-MS U-Pb zircon dating,it is possible to reconstruct the timing of postVariscan volcanism.This volcanism records active tectonism between the latest Carboniferous and Permian,and post-dates the unroofing and erosion of nappes in this segment of the southern Variscides.In particular,igneous zircon grains from calc-alkaline silicic volcanic rocks yielded ages between299±1 and 288±3 Ma,thereby constraining the development of continental strike-slip faulting from south(Escalaplano Basin)to north(Nurra Basin).Notably,andesites emplaced in medium-grade metamorphic basement(Mt.Cobingius,Ogliastra)show a cluster of older ages at 332±12 Ma.Despite the large uncertainty,this age constrains the onset of igneous activity in the mid-crust.These new radiometric ages constitute:(1)a consistent dataset for different volcanic events;(2)a precise chronostratigraphic constraint which fits well with the biostratigraphic data and(3)insights into the plate reorganization between Laurussia and Gondwana during the late Palaeozoic evolution of the Variscan chain.
基金supported by an aid grant from Chengdu Center, China Geological Survey (No. 12120113049100-1)the National Natural Science Foundations (Nos. 40572068, 40839903 and 41272044)+1 种基金the "111" Program (No. B08030)an aid grant (No. GBL11206) from the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Wuhan), China
文摘A growing body of evidence shows that volcanism near the Permian-Triassic boundary（PTB） may be crucial in triggering the Permian–Triassic（P–Tr） mass extinction. Thus, the ash beds near the PTB in South China may carry information on this event. Three volcanic ash layers, altered to clay, outcropped in the PTB beds in Zunyi Section, Guizhou Province, Southwest China. The U-Pb ages, trace elements, and Hf-isotope compositions of zircon grains from these three ash beds were analyzed using LA-ICPMS and LA-MC-ICPMS. The zircons are mainly magmatic in origin（241-279 Ma） except for two inherited/xenocrystic zircons（939 and 2 325 Ma）. The ages of these magmatic zircons indicate three episodes of magmatism which occurred around the MiddleLate Permian boundary（-261.5 Ma, MLPB）, the Wuchiapingian-Changhsingian boundary（-254.5 Ma, WCB）, and the PTB（-250.5 Ma）, respectively. The first two episodes of magmatism near the MLPB and WCB may be attributed to magmatic inheritance or re-deposition. All magmatic zircons share similar trace-element and Hf-isotope compositions. They have Y, Hf, Th and U contents and Nb/Ta ratios are typical of zircons from silicic calc-alkaline magmas. These zircons also exhibit enriched Hf-isotope compositions with _（εHf）（t） values of-11.4 to ＋0.2, which suggests that the three magmatic episodes involved melting of the continental crust. The more enriched Hf-isotope composition （_（εHf）（t）=-11.4--4.8） of Bed ZY13（-250.5 Ma） implies more input of ancient crustal material in the magma. Integration of the Hf-isotope and trace-element compositions of magmatic zircons suggest that these three episodes of magmatism may take place along the convergent continent margin in or near southwestern South China as a result of the closure of the Palaeo-Tethys Ocean.
基金The National Natural Science Foundation of China under contract Nos 41322036,41230960,40906034 and 41276003China Ocean Mineral Resources R&D Association (COMRA) under contract No.DY125-12-R-05+1 种基金China Postdoctoral Science Foundation under contract No.201104616the Taishan Scholar Program of Shandong Province
文摘Some of the islets in the eastern Beibu Gulf are covered by Quaternary volcano strata. The rock samples from these islets mainly consist of quartz tholeiites （at Shenjiandao）, olivine tholeiites （at Linshidao and Xieyang- dao） and alkali basalts （at Yangpubi and Jianshidao）, and basically represent four periods of the Quaternary volcanism of Hainan Island and its adjacent regions. Except for the samples from Shenjiandao, most of the Quaternary volcanics of these islets belong to alkali magma series. The trace element characteristics of all of these samples show they are OIB （oceanic island basalt） -like, which implies that their deep geodynamic setting may be related to a mantle plume. The Sr-Nd-Pb isotopic compositions show that the mantle source beneath the Quaternary strata can be regarded as a result of binary mixing between a depleted, DMM （de- pleted MORB mantle）-like source and an enriched mantle type 2 （EM2）. The EM2 may be originated from the Hainan mantle plume, and has been metasomatized by carbonaceous fluids released from ancient re- cycled oceanic crust at an asthenospheric mantle level. These features, together with typical trace element ratios, reflect that the parent magma was not subjected to crustal contamination during its ascent to the surface. This study provides further petrological and geochemical evidence for the existence of the Hainan mantle plume.
文摘This paper discusses the clayrocks widespread at the Permian-Triassic boundary, which are mostly of volcanic origin. Volcanogenetic textures, structures and minerals such as high-temperature quartz are found in clayrocks at the Permian-Triassic boundary in many places. Thousands of microspherules have been collected from the Boundary clayrocks, many of which exhibit the typical features of the process from melting to cooling and solidification. indicating that they were formed by volcanic eruption or extraterrestrial impact. Volcanic effects on the Permian-Triassic mass extinction may be reflected in conodonts, algae and ammonoids. The Boundary clayrocks are found in many Permian-Triassic sections along the coast of Tethys. Their orighin remains to be studied.
基金jointly funded by the National Natural Science Foundation of China(Grant Nos.41972120,42172129)the State Key Laboratory of Paleobiology and Stratigraphy(Nanjing Institute of Geology and Paleontology,CAS)(Grant No.173131)+1 种基金the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX050103)the China Postdoctoral Science Foundation(Grant No.2021M702720)。
文摘Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposits at the southern margin of the Junggar Basin,based on petrology,geochronology and geochemical analyses.The results show that a massive collapse of unstable sediments from the slope was triggered by volcanism,resulting in the formation of slumping gravity flows.The occurrence of volcanic beds in the slump deposits confirm that synchronous volcanism likely affected sediment instability,triggering gravity flows.The Th/Yb,Ta/Yb and Th/Ta elemental ratios,U-Pb ages of detrital zircons and paleocurrent directions indicate that the North Tianshan(NTS)island arc represents the provenance of the Qianxia Formation.Moreover,statistical data on the pyroclastic components in the gravity flow deposits reveal an intensity index of volcanism,indicating that volcanism is strongly related to gravity flow deposits,especially in terms of the type and distribution of the deposits.A model for volcanically-triggered deep-water gravity flow deposits is established,in order to provide a more in-depth understanding of the co-evolution of volcanism and gravity flow deposits within the depositional setting of the late Paleozoic NTS oceanic subduction margin in the Junggar Basin.
文摘The rock series, rock types and Sr-Nd isotopic dating of the Cenozoicvolcanic rocks in the South China Sea are similar to those in its vicinity. On the basis of thespreading age of the South China Sea, the Cenozoic volcanic rocks are divided into three stages: thepre-spreading stage, the spreading stage and the post-spreading stage. The deep processcharacteristics of the asthenosphere and lithosphere may be inferred from the study on primarybasaltic magma. The top layers of the asthenosphere both in the spreading stage and in thepre-spreading stage are closer to the earth surface than that in the post-spreading stage. From thepre-spreading stage to the spreading stage, the top layer of the asthenosphere decreased in depth,while the amount of interstitial partial melts increased. The evolution of the primary basalticmagma shows a progressive evolution sequence of the rifting volcanism and a faster lithosphericspreading velocity. From the spreading stage to the post-spreading stage, the top layer of theasthenosphere gradually increased in depth, but the amount of interstitial partial melts decreased.The evolution of primary basaltic magma shows a retrogressive evolution sequence of the riftingvolcanism and a gradual decrease in the lithospheric spreading velocity. The depth recognized by thestudy on the Cenozoic volcanism demonstrates the deep environment for the formation and evolutionof the South China Sea.
文摘Sanjiang area in Southwestern China is tectonically situated at the east end of Himalaya-Tethys tectonic domain and at the conjunction of Tethyan Mountain Chain and Circum-Pacific Mountain Chain. It is one of the key areas to understand the global tectonics and also one of gigantic metallogenic provinces in China and even in the world . Volcanism had occurred during the period of time from Proterozoic to Cenozoic . The most important and active periods of volcanism , however , are Carboniferous , Permian and Triassic . The pattern of spatial distribution of Sanjiang volcanic rocks and ophiolites can essentially be described as that several intra - continental micro-massif volcanic districts are respectively sandwiched between each two of four coupling ophioh'te - arc volcanic belts , which are successively from west to east : Dingqing - Nujiang belt , Lancangjiang belt , Jinshajiang belt and Ganzi-Litang belt . Four tectono - magma tic types of volcanic rocks have been rec-ognized in Sanjiang area as follows: mid -ocean- ridge/ para - mid - ocean - ridge type , arc type , collision type and intra - continent type . The petrotectonic assemblages within suture zones , such as oceanic assemblage , subduction - related assemblage , collision - related assemblage etc ., have been paid more attention to because of their significant importance in reconstruction of the history of Sanjiang Tethyan orogenic belt and plate tectonics .Couph'ng ophiolite - arc volcanic belt, para-mid - ocean - ridge volcanism and volcanic rocks, post -collision arc volcanism and volcanic rocks and tensional volcanic arc are newly defined in the present work . These new facts and concepts will be greatly beneficial to understanding the history of Sanjiang Tethyan plate tectonics and the complexity of the volcanism in orogenic belts and of the evolution of the continental lithosphere . A preliminary model of the evolution of Sanjiang Tethys under petrotectonic constraints was presented . It consists of the following four successive stages : (1) Late Paleozoic ocean spreading - dominant stage , (2 ) Early Mesozoic subduction and closing - dominant stage , (3) Late Mesozoic collisional orogenic stage characterized by crust shortening and compression , and (4 ) Cenozoic intra - continent orogenic stage characterized by crustal slipping - out and strike - slipping .
基金Financed by the National Natural Science Foundation of China(No.49471013).
文摘This paper is concentrated on Cenozoic volcanism and geothermal resources in Northeast China. There are a lot of Cenozoic volcanoes, a large area of volcanic rocks, a large number of active faults and rich geothermal resources in Northeast China. The time and space characteristics of Cenozoic volcanism and the space distribution characters of hot springs and high geothermal flux regions in Northeast China are described and discussed on the basis of geological, geothermal, drilling and volcanological data. It is revealed that the hot springs and high geothermal flux regions are related to the Cenozoic volcanism, rifting and faulting in Northeast China. It is especially emphasized that the hot springs and high geothermal anomaly areas are controlled by active deep faults. It is proposed that the Cenozoic volcanism regions, rift basins, active fault belts, activated plate suture zones and large earthquake occurrence points are the best areas for prospecting geothermal resources. The geothermal resources in younger volcanic zones are richer than those in older volcanic belts. The hot springs and active or activated faults might be a very good clue for looking for geothermal resources.
文摘This paper summarizes the history of tectono magmatic evolution, the types and backgrounds of mineralization prior to the orogenic period of North Qilian Mountains. It points out that: during the process of Paleozoic ocean basin opening and closing, the large scale marine volcanism and massive sulfide deposits controlled by sea floor hydrothermal circulation systems are the two sharpest features in the geological developing history of the orogenic belt, which are also the most two important aspects related to each other and should be given a special attention in the geological studies in the region.
基金supported by the National Key R&D Program of China (No. 2018YFC0309800)the National Natural Science Foundation of China (Nos. 91628301, U1606401, 41606069, 41776058)+2 种基金the Natural Science Foundation of Guangdong Province in China (No. 2017A030313243)the Chinese Academy of Sciences (Nos. Y4SL021001, QYZDY-SSWDQC005)the China Association of Marine Affairs (No. CAMAZD201714)
文摘Oceanic plateaus are large igneous provinces in the oceans,created by massive underwater eruptions,but their late-stage volcanism is poorly understood.With the addition of recent high-quality bathymetric data to existing data,286 secondary cones were discovered over Shatsky Rise oceanic plateau.These cones with steeper flank slopes(mean 6.1°±4.4°)and smaller sizes(102–1923 m in height)are morphologically distinct from the plateau,and they are thought to have formed after the main volcanic episodes.Cone height and characteristic height(420 m)are close to seamounts in the Pacific Ocean,whereas greater than those in the Atlantic Ocean.Mean flatness of Shatsky Rise’s cones(0.25±0.20)are similar to that of seamounts in both Pacific and Atlantic Oceans,but notably density in cone distribution(0.56 km^-3)and their mean slope are significantly lower than those of seamounts in the two oceans.Lower slopes of secondary cones within Shatsky Rise may be explained by higher effusion rates of remaining magma.Although cone formation was expected to have a link to rifting by seafloor spreading,weak relationship between cone orientation and magnetic anomaly pattern implies that the expectation is negative.Moreover,weak correlation between the cone height and depth indicates it is not true that volcanic cones grow taller when they occur closer to the massif summits with thicker oceanic crust,which was suggested as the increase in hydraulic pressure.Cone height and flatness are also not strongly related,implying that remaining magma supply was too limited to foster the cones to critical height.
基金part of the research project"Crustmantle interactions beneath the Hangai Mountains in western Mongolia"the financial support of the DFG and the SNF,awarded through the DACH program
文摘Intraplate processes,such as continental surface uplift and intraplate volcanism,are enigmatic and the underlying mechanisms responsible are not fully understood.Central Mongolia is an ideal natural laboratory for studying such processes because of its location in the continental interior far from tectonic plate boundaries.
文摘The Ordovician marine volcanic rocks in the north Qilian mountains are discussed in this paper. According to geology, petrotectonic assemblage and geochemistry, a new model about plate tectonic evolution of the north Qilian mountains is set up. The Ordovician marine volcanic rocks in the north Qilian mountains which characterized by the geological features of tectonic melange of continent to continent collision underwent complicated tectonic movement, and can be classified into three main kinds of petrotectonic assemblages. During Ordovician period, north Qilian area was a polyisland ocean which consisted of three ocean basins separated by the middle microcontinental blocks.
文摘The principle prerequisite for the formation of a volcano is the generation of a channel for magma transportation. There is little research on the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan plateau. Based on the subcrustal mantle convectiongenerated stress field inversed by gravity anomalies, together with its relationship to the Cenozoic volcanism in the plateau, and the mechanism of crustal fracture formation, as well as the numerical results of the evolution of mantle convection beneath the plateau, this paper investigates the deep mechanical mechanism for the formation of a magma transportation channel in the Tibetan plateau. There are two significant extensional convection-generated stress zones beneath the plateau, in which the volcanic rocks in the central and northern parts of the plateau are distributed. The Linzizong volcanism in southern Tibet correlates the upwelling mantle flow prior to the India-Asia collision or during the early stage of the collision. The magnitude of the stress is - 100 MPa, which is the same order of force that causes crustal fractures. The evidence implies that the mantle convection-generated stress is one of the principle causes of crustal fractures, and furthermore, the formation of the magma transportation channel in the Tibetan plateau.
基金Financial support for this research came from the Department of Science and Technology,Government oF India(to RM,SD and PC)the Yokohama National University,Japan(to MR and MA)the School of Biology,Earth and Environmental Sciences.the University of New South Wales,Australia(to RM)
文摘The Palaeoproterozoic-Mesoproterozoic transition （ -1600 Ma） is a significant event in the Earth history as a global thermal perturbation affected the pre-1600 Ma landmasses. Like other cratonic blocks of the world, lithospheric thinning, sedimentation, magmatism, metamorphism and crustal melting/anatexis are associated with this significant geological event in the Singhbhum cratonic province of India. This paper is a review of sedimentological, magmatic and tectono-thermal events in the Singhbhum craton at 1600 Ma. The Palaeo-Mesoproterozoic sedimentation and volcanism in the Singhbhum craton took place in a terrestrial intracontinental rift setting. The available geochronological data are indicative of late Palaeoproterozoic to Neoproterozoic tectono-thermal events in the Chhotanagpur Granite Gneissic Complex （CGGC）, an east-west trending arcuate belt of granite gneisses, migmatites and metasedi- mentary rocks. A detailed multidisciplinary geo-scientific investigation of the Dalma volcanic belt and the area to its north （Chandil Formation） and further north in CGGC will enable us to constrain the extant surface processes and crust-mantle interactions, the collision events between the North and South Indian cratonic blocks, and the position of India in the Columbia supercontinent.
文摘This paper deals with indirect effects of major impacting throughout the Early Paleozoic resp. with those of super plume activity during the Early Cretaceous, both applied to the siliciclastic series of Jordan deposited on the Arabian Platform, Arabian Plate. Its focus is mainly directed on gases released by both processes (CO2, SO2, NOx, HCl, HF) and the relating acids, challenged by experiments and microscopic analysis of grain mounts and thin sections that reveal chemical instability of quartz and ultrastable heavy minerals (i.e. tourmaline) under high acidity (pH °C - 90°C). According to Lopatin’s Time/Temperatur-Index the Lower Cambrian reached the onset of hydrocarbon generation (liquid window) during the Lower Early Cretaceous. Unstable heavy minerals (apatite, garnet, hornblende, epidote, zoisite/clinozoisite) are generally absent in quartz arenites while in arkosic sandstones of marine environment carbonate cement and primary clay minerals (illite) provide conservation. As known since the eighties, the K/T-event’s indirect effects had global influence on Earth’s surface sediments and atmospheric chemistry by wildfires, hot whirl storms, acidic “sturz rain”, dust, soot, darkness, loss of photosynthesis, toxic metals, gases and relating acids. All of them are here concerned and applied to major impacting throughout the Early Paleozoic using the impact data of Price (2001);while superplume volcanism during Cretaceous led to the opening of the South Atlantic accompanied by the cyclic outflow of the Para?a/Etendeka Flood Basalts and relating gases in a gigantic scale (137 - 127 Ma). Assuming that the gases cause similar global effects on Earth’s surface sediments, an according result may be expected in form of quartz arenites and their sequence-analytical patterns (cyclic SBs, MFSs).*
文摘Eruptions of lava flows of Deccan large igneous province straddled the Cretaceous-Palaeogene boundary (K-Pg). Sediments associated at different stratigraphic levels within the lava piles of Deccan volcanic sequences (DVS) are mainly terrestrial. We studied the sediments of Eastern and Central Deccan Volcanic Province, and the Malwa Plateau for tracking changes in reptilian tetrapods across the volcanism. The reptiles are mainly represented by abelisaurid-titanosaurid dinosaurs, Alethinophidia madtsoiia snakes, Notosuchian crocodylomorph Simosuchus, bothremydid Kurmademydinae turtles and Anguimorph and Scincomorphs lizards. The evidences suggest that the non-avian dinosaurs were adversely affected by the arrival of the first volcanic flows locally in the province either within C30N or C29R Maastrichtian. The abelisaurid theropods became extinct whereas a single or two species of titanosauriforme dinosaurs survived but eventually became extinct at least 350 ky before the K-Pg boundary with increasing volcanism. The madtsooid snakes and crocodylimorphs were also adversely affected with decline in their diversity and abundance, whereas the Bothremydid turtles survived the initial onslaught of Deccan volcanism and continued across the K-Pg boundary.
文摘The article presents new views on volcanism and earthquakes. The problem of the scientific basis for the interpretation of geotectonic theories was discussed. The interpretation of the mantle plume phenomenon according to the theory of expansion and the theory of primal forces of nature is presented. The heat source in the Earth’s core <span style="font-family:;" "="">is</span><span style="font-family:;" "=""> thermonuclear reactions. The cause of earthquakes is not collisions of lithospheric plates, but plasma eruptions. The stre<span>sses in the rock mass, causing global fractures, arise due to the increase in the size of nuclides in the process of plasma recombination. The oldest ba</span>salts that make up the oceanic plates remain invariably along the shores of continents.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "="">The widespread view of the subduction of lithospheric plates and vertical convection cells of rock matter should be regarded as </span><span style="font-family:;" "="">a </span><span style="font-family:;" "="">scientific fiction.</span>
