The basement of the Romanian Carpathians is made of Neoproterozoic to early Paleozoic peri- Gondwanan terranes variably involved in the Variscan orogeny, similarly to other basement terrains of Europe. They were hardl...The basement of the Romanian Carpathians is made of Neoproterozoic to early Paleozoic peri- Gondwanan terranes variably involved in the Variscan orogeny, similarly to other basement terrains of Europe. They were hardly dismembered during the Alpine orogeny and traditionally have their own names in the three Carpathian areas. The Danubian domain of the South Carpathians comprises the Dragsan and Lainici-Paiius peri-Amazonian terranes. The Dragsan terrane originated within the ocean surrounding Rodinia and docked with Rodinia at -800 Ma. It does not contain Cadomian magmatism and consequently it is classified as an Avalonian extra-Cadomian terrane, The Lainici-Pfiius terrane is a Ganderian fragment strongly modified by Cadomian subduction-related magmatism, It is attached to the Moesia platform. The TisoviD terrane is an ophiolite that marks the boundary between Drfagsan and Lainici-Paius terranes. The other basement terranes of the Romanian Carpathians originated close to the Ordovician North- African orogen, as a result of the eastern Rheic Ocean opening and closure. Except for the Sebes-Lotru terrane that includes a lower metamorphic unit of Cadomian age, all the other terranes （Bretila, Tulghes, Negrisoara and Rebra in the East Carpathians, Somes, Biharia and Baia de Aries in the Apuseni mountains, Fagaras, Leaota, Carat and Pades in the South Carpathians） represent late Cambrian-Ordovician rock assemblages. Their provenance, is probably within paleo-nortbeast Africa, close to the Arabian-Nubian shield. The late Cambrian-Ordovician terranes are defined here as Carpathian-type terranes. According to their lithostratigraphy and origin, some are of continental margin magmatic arc setting, whereas others formed in rift and back-arc environment and closed to passive continental margin settings. In a paleo- geographic reconstruction, the continental margin magmatic arc terranes were first that drifted out, followed by the passive continental margin terranes with the back-arc terranes in their front. They accreted to Laurussia during the Variscan orogeny. Some of them （Sebes-Lotru in South Carpathians and Baia de Aries in Apuseni mountains） underwent eclogite-grade metamorphism. The Danubian terranes, the Bretila terrane and the Somes terrane were intruded by Variscan granitoids.展开更多
Numerous geophysical studies have revealed the lithospheric structure of the Qiangtang and the Songpan-Ganzi terranes in the eastern Tibetan Plateau.However,crust-mantle evolution and crustal response to the Indian li...Numerous geophysical studies have revealed the lithospheric structure of the Qiangtang and the Songpan-Ganzi terranes in the eastern Tibetan Plateau.However,crust-mantle evolution and crustal response to the Indian lithospheric subduction are still controversial.Answering these questions requires additional information regarding crustal structure.In this study,the 2-D normalized full gradient(NFG)of the Bouguer gravity anomaly was used to investigate anomalous sources and interpret the crustal structure underneath the Qiangtang and Songpan-Ganzi terranes.The NFG-derived structures with loworder harmonic numbers(N=33 and N=43)showed that an anomalous source beneath the southern Qiangtang terrane had a characteristic northeastward-dipping shape,suggesting the northeastward motion of the crustal material induced by underthrusting Indian lithospheric mantle.The NFG images with harmonic number N=53 showed a large-scale anomalous source in the lower crust of the transformational zone from the Qiangtang terrane to the Songpan-Ganzi terrane,consistent with thickening crust and resistance of lower crustal flow.The anomalous source demonstrated by the NFG results with harmonic number N=71,located in the upper crust underneath the Ganzi-Yushu fault,suggested a seismogenic body of the 2010 M6.9 Yushu event.展开更多
Two terranes formed since the Late Palaeozoic can be distinguished in southwestern China. One is charac-terized by the Permo-Carboniferous ice-rafted marine gravel-bearing clastic formation and the cold-water faunaof ...Two terranes formed since the Late Palaeozoic can be distinguished in southwestern China. One is charac-terized by the Permo-Carboniferous ice-rafted marine gravel-bearing clastic formation and the cold-water faunaof the Gondwana facies, including the Gangmar Co, Lhasa, Sa' gya, Tengchong and Baoshan terranes and theother is marked by the Upper Palaeozoic of the Yangtze type with the Cathaysian flora and the Pacific-typefusulinids, comprising the Changning-Menglian, Shuangjiang-Lancang, Qamdo and Bayan Har terranes. TheLongmu Co-Shuanghu-Dengqen-North Lancang River-Kejie-Mengding suture zone between the two groups ofterranes is the boundary between Gondwana and Pacifica in southwestern China. On the grounds of thesedimentary formation and successive southwestward migration of the Asian nonmarine Jurassic-Cretaceousendemic bivalves, the ages of the suture and some terranes to the southwest of the suture zone are discussed.The Baoshan terrane and the Nyainrong-Sog terrane in the Lhasa composite terrane were firstly pieced togeth-er with the Asian continent in the early Early Jurassic. The northern Tibet-western Yunnan microplate, in-cluding the Gangmar Co, Lhasa and Tengchong terranes, collided with the Asian continent at the end of theEarly Cretaceous Neocomian.展开更多
The paper presents an overview of the relationships between the interior structures of tectonic terranes and the distribution of tectonic-metallogenic zones in Southeast Asia. Episodic tectonic activities occurred in ...The paper presents an overview of the relationships between the interior structures of tectonic terranes and the distribution of tectonic-metallogenic zones in Southeast Asia. Episodic tectonic activities occurred in this archipelagic area, generating metallogenic belts in multi-terranes. Since the Late Paleozoic, opening and closure of the Paleotethys and Neotethys led to multiple suture zones between different blocks, mainly between the Indochina terrane, the Nambung terrane, the Sibumasu terrane and the West Myanmar terrane. During the Mesozoic to Cenozoic, the formation of accreted terranes and their related islands was caused by subduction and collision processes between the Pacific and Australian plates toward the Eurasian Continent, forming Sundaland and its affiliated islands, the Philippines and its subsidiary islands, the Papua New Guinea terrane and its related islands and the Sunda epicontinental arc system. Within the margin of terranes resulted in the structural transfer zones, their secondary tectonic units can be divided into island arc belts, back-arc basins, suture zones, marginal fold belts and orogenic belts. The metallogenic assemblages are mainly distributed within these structural zones of the terranes. According to the relationship between these tectonic units and the distribution of mineral resources, the tectonic-metallogenic belts can be divided into 24 metallogenic belts in Southeast Asia. They are characterized by a diversity and frequency of metallogenic material combination which is likely to reflect the complexity of the material distribution during mineralization processes, mostly by the structural transformation during the dissociation-convergence process between multiple terranes. Therefore, the formation of ore deposits was not only restricted by the evolution(opening and closure) of Paleo-and Neotethys, but may also be controlled by the interaction of the terranes with different tectonic attributes which provided multiple sources of metallogenic material.展开更多
Abstract: Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the bord...Abstract: Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the border between China and Mongolia and its structure, composition and tectonic evolution have been revealed, and abundant information about the deep structures has been provided. Based on the research into the geotransect, it is suggested that the crust in this area was formed by the assembly of the terranes in different geological stages. Following the formation of the Palaeo-Asian continent, the north part of the corridor of the transect became a part of the huge unifying continent by the end of the Early Permian. In the Mesozoic and Cenozoic, as a result of the compression mainly by the push of the Qinghai-Tibet plateau on the south, the unique crustal structure and geomorphologic features on the northern Qinghai-Tibet plateau were formed. This geotransect together with the Yadong-Golmud geotransect constitutes a long geotransect which runs across the western Chinese continent.展开更多
It is one of hot issues in Tibetan research that is to study the mode,process and kinetics of the crustal shortening during Mesozoic-Cenozoic.In this paper, on the basis of systematic collection,analysis and research ...It is one of hot issues in Tibetan research that is to study the mode,process and kinetics of the crustal shortening during Mesozoic-Cenozoic.In this paper, on the basis of systematic collection,analysis and research of the existing data and results from Himalayas,Lhasa and Qiangtang terranes,we conducted the balanced cross-section study.In the north Qiangtang,the line-balanced cross-section展开更多
The extensive tracing of Nd, Sr and Pb isotopes has revealed that there exist high-degree heterogeneities in suboceanic mantle and mantle anomalies of the Southern Hemisphere on a large scale (DUPAL, high <sup>8...The extensive tracing of Nd, Sr and Pb isotopes has revealed that there exist high-degree heterogeneities in suboceanic mantle and mantle anomalies of the Southern Hemisphere on a large scale (DUPAL, high <sup>87</sup>Sr/<sup>86</sup>Sr, and HIMU, high μ value, i. e. <sup>238</sup> U/<sup>204</sup>pb). Recently, the isotopic tracing of the Cenozoic Volcanics from the continent of China has confirmed that there exists a general tendency that the subcontinental mantle of eastern China was en-展开更多
The Raohe area of Heilongjiang Province,Northeast China belongs to the Nadanhada Terrane,which was in low latitudes of Panthalassa during the Triassic.The composition of the Late Triassic conodont fauna,derived from l...The Raohe area of Heilongjiang Province,Northeast China belongs to the Nadanhada Terrane,which was in low latitudes of Panthalassa during the Triassic.The composition of the Late Triassic conodont fauna,derived from limestone lenses interpreted to formed on seamounts,provides important new information on the pelagic biota in this ocean.New conodont samples collected from sections at Minzhu,Minnan and Chigangbei sections belong to three Norian conodont zones.In ascending order,they are:Mockina postera Zone,Mockina bidentata Zone and Parvigondolella andrusovi Zone.The Norian conodont fauna in the Raohe area has distinct attributes:there are a lot of cosmopolitan species(e.g.,Mockina postera,Mockina bidentata,Parvigondolella andrusovi)which enable good global correlation;endemic conodont species are also present(e.g.,Mockina sakurae,Mockina shamiseni,Norigondolella nadanhadaensis)indicating that Panthalassa Ocean conodont populations also contained unique taxa;and some conodonts belong to taxa with much shorter ranges in surrounding epeiric seas(e.g.,Carnepigondolella pseudoechinata,Neocavitella cavitata and Epigondolella vialovi).The presence of the latter“relicts”indicates that the seamounts were persistently suitable habitats for many millions of years in the Late Triassic.展开更多
The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho...The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho-types from the quarries in Kabbaldurga reveal a complex geological history in the Archean and early Paleoprotero-zoic.Magmatic protoliths predominantly record Paleoar-chean ages between 3.4 and 3.2 Ga.Combined U-Pb and Lu-Hf signatures indicate a history of recurrent crustal anatexis,juvenile magmatic input,and felsic injections.Mesoarchaean magmatic charnockites were generated mainly from hornblende-dehydration melting of Paleoar-chaean mafic rocks.In addition,Peninsular Gneissic Com-plex of the Dharwar Craton,commonly described as TTG suites,are likely generated by melting of hydrated basalt.The new data are consistent with the idea of a convecting magmatic cycle and also support the proposal that the southern Dharwar Craton comprises a tilted cross-sec-tion through the Archaean crust.Paleoproterozoic high-temperature event is documented here as a complex unit involving juvenile mafic magmatism,granulite facies imprints and crustal anatexis as well as felsic injections,occurring within a short time period around 2.5 Ga.展开更多
Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc ...Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo-Tethys Ocean and its dynamic mechanism.Basalt samples from the Luobadui Formation in the Leqingla area,NW of Linzhou City in the central Lhasa subterrane,southern Xizang exhibit arc-like geochemical signatures in a subduction-zone tectonic setting characterized by high Al_(2)O_(3)and low TiO_(2)contents,fractionated REE patterns with low Nb/La ratios and high LREE concentrations,and negative HFSE anomalies.Based on their higher Th/Ce,Nb/Zr,and lower Ba/Th,Pb/Nd ratios,slightly negative to positiveε_(Nd)(t)values,and the relatively high Sr-Pb isotopic compositions,these samples were probably derived from partial melting of a depleted mantle source of garnet+spinel lherzolite,metasomatized by subducted sediments around 297 Ma.Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine,clinopyroxene and minor plagioclase during magma ascent and eruption.It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo-Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.展开更多
The Moon has been divided into three terranes:Procellarum KREEP Terrane(PKT),Feldspathic Highland Terrane(FHT),and South Pole-Aitken Terrane(SPAT),using globally measured Th and FeO.Many lunar evolu-tion models have p...The Moon has been divided into three terranes:Procellarum KREEP Terrane(PKT),Feldspathic Highland Terrane(FHT),and South Pole-Aitken Terrane(SPAT),using globally measured Th and FeO.Many lunar evolu-tion models have predicted that a lunar magma ocean will produce a residual layer enriched in incompatible elements such as K,REE,and P(i.e.,KREEP)in the late age of crys-tallization;and that the distribution of thorium can be used as a proxy for determining the global distribution of KREEP.The thorium distribution in these three terranes is inhomo-geneous.The highest concentration of thorium is in PKT,the medium concentration of thorium is in SPAT,and almost none in FHT.Then what is the specific distribution in each of the terrane and what enlightenment can it tell us?Here we present and describe the detailed thorium distribution in PKT,SPAT,and FHT and provide some information for the origin of asymmetries on the lunar surface.展开更多
Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb...Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb isotopic composition of feldspar hosted in granitic rocks(thirteen Archean and one Paleoproterozoic)from the northern Kongling terrane,Yangtze Craton,South China,is analyzed.The samples reveal a substantial variation in their Pb isotopic composition,spanning the gap between the 1.9 Ga and present-day geochrons,which indicates extensive resetting by later tectonothermal events.This resetting was interpreted to have likely resulted from Paleoproterozoic and Neoproterozoic tectonothermal events related to the assembly and breakup of the Columbia and Rodinia supercontinents.These results suggest that Pb isotopes should be used cautiously when tracing magma sources and petrogenesis in magmatic rocks that have experienced post-magmatic reworking.However,the in situ Pb isotopic composition of feldspar in ancient granitoids may also potentially be used to reveal later tectonothermal events.The extensive resetting of the Pb isotopic composition in feldspar by regional thermal events may also provide new insights into our understanding of the Pb isotope paradox.展开更多
Mafic granulites have been found as structural lenses within the huge thrust system outcropping about 10 km west of Nam Co of the northern Lhasa Terrane, Tibetan Plateau. Petrological evidence from these rocks indicat...Mafic granulites have been found as structural lenses within the huge thrust system outcropping about 10 km west of Nam Co of the northern Lhasa Terrane, Tibetan Plateau. Petrological evidence from these rocks indicates four distinct metamorphic assemblages. The early metamorphic assemblage (M1) is preserved only in the granulites and represented by plagioclase+hornblende inclusions within the cores of garnet porphyroblasts. The peak assemblage (M2) consists of garnet+clinopyroxene+hornblende+plagioclase in the mafic granulites. The peak metamorphism was followed by near-isothermal decompression (M3), which resulted in the development of hornblende+plagioclase symplectites surrounding embayed garnet porphyroblasts, and decompression-cooling (M4) is represented by minerals of hornblende+plagioclase recrystallized during mylonization. The peak (M2) P-T conditions of garnet+ clinopyroxene+plagioclase+hornblende were estimated at 769-905℃ and 0.86-1.02 GPa based on the geothermometers and geobarometers. The P-T conditions of plagioclase+hornblende symplectites (M3) were estimated at 720-800℃ and 0.55-0.68 GPa, and recrystallized hornblende+plagioclase (M4) at 594-708℃ and 0.26-0.47 GPa. It is impossible to estimate the P-T conditions of the early metamorphic assemblage (M1) because of the absence of modal minerals. The combination of petrographic textures, metamorphic reaction history, thermobarometric data and corresponding isotopic ages defines a clockwise near-isothermal decompression metamorphic path, suggesting that the mafic granulites had undergone initial crustal thickening, subsequent exhumation, and cooling and retrogression. This tectonothermal path is considered to record two major phases of collision which resulted in both the assemblage of Gondwanaland during the Pan-African orogeny at 531 Ma and the collision of the Qiangtang and Lhasa Terranes at 174 Ma, respectively.展开更多
We investigate the effect of the westerly rotation of the lithosphere on the active margins that surround the Americas and find good correlations between the inferred easterly-directed mantle counterflow and the main ...We investigate the effect of the westerly rotation of the lithosphere on the active margins that surround the Americas and find good correlations between the inferred easterly-directed mantle counterflow and the main structural grain and kinematics of the Andes and Sandwich arc slabs.In the Andes,the subduction zone is shallow and with low dip,because the mantle flow sustains the slab;the subduction hinge converges relative to the upper plate and generates an uplifting doubly verging orogen.The Sandwich Arc is generated by a westerly-directed SAM(South American) plate subduction where the eastward mantle flow is steepening and retreating the subduction zone.In this context,the slab hinge is retreating relative to the upper plate,generating the backarc basin and a low bathymetry single-verging accretionary prism.In Central America,the Caribbean plate presents a more complex scenario:(a) To the East,the Antilles Arc is generated by westerly directed subduction of the SAM plate,where the eastward mantle flow is steepening and retreating the subduction zone.(b) To the West,the Middle America Trench and Arc are generated by the easterly-directed subduction of the Cocos plate,where the shallow subduction caused by eastward mantle flow in its northern segment gradually steepens to the southern segment as it is infered by the preexisting westerly-directed subduction of the Caribbean Plateau.In the frame of the westerly lithospheric flow,the subduction of a divergent active ridge plays the role of introducing a change in the oceanic/continental plate’s convergence angle,such as in NAM(North American)plate with the collision with the Pacific/Farallon active ridge in the Neogene(Cordilleran orogenic type scenario).The easterly mantle drift sustains strong plate coupling along NAM,showing at Juan de Fuca easterly subducting microplate that the subduction hinge advances relative to the upper plate.This lower/upper plate convergence coupling also applies along strike to the neighbor continental strike slip fault systems where subduction was terminated(San Andreas and Queen Charlotte).The lower/upper plate convergence coupling enables the capture of the continental plate ribbons of Baja California and Yakutat terrane by the Pacific oceanic plate,transporting them along the strike slip fault systems as para-autochthonous terranes.This Cordilleran orogenic type scenario,is also recorded in SAM following the collision with the Aluk/Farallon active ridge in the Paleogene,segmenting SAM margin into the eastwardly subducting Tupac Amaru microplate intercalated between the proto-LiquineOfqui and Atacama strike slip fault systems,where subduction was terminated and para-autochthonous terranes transported.In the Neogene,the convergence of Nazca plate with respect to SAM reinstalls subduction and the present Andean orogenic type scenario.展开更多
The island of New Guinea is the mountainous margin of the Australian continent.Paleozoic and Proterozoic Australian craton extends northward beneath the shallow waters of the Arafura Sea to underlie the southern plain...The island of New Guinea is the mountainous margin of the Australian continent.Paleozoic and Proterozoic Australian craton extends northward beneath the shallow waters of the Arafura Sea to underlie the southern plains of New Guinea and,with overlying sediments,to form the dramatically sculpted southern slopes of the central range in a great fold and thrust belt.The fold and thrust belt marks the outer limit of the autochthon.Beyond,to the N,E and W,is an aggregation of terranes that have accreted since the Late Cretaceous,driven by oblique convergence between the Pacific and Indo-Australian plates.The terranes comprise continental fragments and blocks of oceanic volcanic arc and of oceanic crust and mantle origin,and include two great ophiolites.The plate boundary itself is a complex system of microplates,each with separate motion,and marked by every kind of plate boundary.In the E the opening of the Manus Basin is associated with rapid clockwise rotation of New Britain,and the opening of the Woodlark Basin causes extension of continental crust in the Papuan peninsula and islands.This has resulted in the development of low-angle extensional faults and domal structures in metamorphic rocks and the exhumation of Pliocene eclogite.Remarkably similar extensional structures and the exhumation of Pliocene eclogite are seen in the Bird’s Head area of western New Guinea(Wandamen Peninsula).展开更多
The Pilbara region of Western Australia is one of only two areas on Earth–the other being the Kaapvaal Craton of southern Africa–that contain well preserved,nearcontinuous geological records of crustal evolution fro...The Pilbara region of Western Australia is one of only two areas on Earth–the other being the Kaapvaal Craton of southern Africa–that contain well preserved,nearcontinuous geological records of crustal evolution from the Paleoarchean into the late Paleoproterozoic.The Pilbara is famous for hosting fossil evidence of early life(stromatolites and microfossils),and for containing a record of the early Archean atmosphere.The geological record extends from granite–greenstone terranes and overlying clastic basins of the 3.53–2.83 Ga Pilbara Craton,across a major unconformity,to a series of 2.78–1.79 Ga volcanic and sedimentary successions.Between 3.53–3.23 Ga,a succession of mantle plume events formed a thick volcanic plateau on older continental crust,remnants of which include enclaves of c.3.6 Ga granitic gneiss and abundant 3.8–3.6 Ga inherited and detrital zircons.During each of the plume events,the volcanic plateau was intruded by crustally-derived granitic rocks,leading to vertical deformation by partial convective overturn.By 3.23 Ga,these processes had established thick continental crust that was then rifted into three microplates separated by c.3.2 Ga basins of oceanic crust.Subsequent plate tectonic processes to 2.90 Ga included subduction,terrane accretion,and orogeny.From 2.78–2.63 Ga the northern Pilbara Craton was affected by minor rifting,followed by deposition of thick basaltic formations separated by felsic volcanic and sedimentary rocks(Fortescue Basin).Rifting in the southern Pilbara resulted in progressively deepening marginal basin sedimentation,including thick units of banded iron formation(Hamersley Basin:2.63–2.45 Ga).展开更多
The Earth Science Division of the School of Geography,Earth Science and Environmental(SGESE)of the University of the South Pacific(USP)in Suva Fiji in association with its International Research Office hosted an inter...The Earth Science Division of the School of Geography,Earth Science and Environmental(SGESE)of the University of the South Pacific(USP)in Suva Fiji in association with its International Research Office hosted an international meeting on“Subduction,Volcanism and the Evolution of Oceanic and Continental Crust”that was held on 9-16 February 2014 at the Tanoa International Hotel in Nadi,Fiji.The meeting was followed by a 2-day excursion to Eocene-Miocene arc terranes in the north and western parts of the island of Viti Levu including the early-arc Yavuna Group which is intruded by a large tonalite body.展开更多
A series of tight bends(oroclines)are recognised in the late Paleozoic–early Mesozoic southern New England Orogen between Brisbane and Newcastle,but their exact geometry and tectonic evolution are still debated.This ...A series of tight bends(oroclines)are recognised in the late Paleozoic–early Mesozoic southern New England Orogen between Brisbane and Newcastle,but their exact geometry and tectonic evolution are still debated.This contribution provides an outline of the different tectonic elements within the orogen and the relationships of these elements with the oroclinal structure.Pre-oroclinal tectonic elements were derived from a Devonian–Carboniferous subduction zone,and include forearc basin terranes and accretionary wedge rocks that are separated from each other by a narrow belt of serpentinites and high-pressure rocks.Rocks are predominantly steeply dipping and their map-view pattern delineates three bends:the Z-shaped Texas and Coffs Harbour oroclines in the north and the U-shaped Manning Orocline in the south.During the early Permian(298–288 Ma),the area was affected by widespread,mostly S-type,magmatism that heralded a period of crustal extension accompanied by the formation of sedimentary rift basins.The spatial distribution of early Permian granitoids mimics the shape of the oroclines,which further defines a fourth bend,the Nambucca Orocline.Whether these curvatures formed by bending of a quasi-linear belt,or as primary early Permian arcuate features,is an unresolved question that warrants further paleomagnetic,geochronological and structural investigations.展开更多
The Central Asian Orogenic Belt(CAOB),the Earth’s largest Phanerozoic accretionary orogenic belt,is located between the Siberian,Tarim and North China Cratons and the Kazakhstan composite continent(Fig.1a).It is ca.8...The Central Asian Orogenic Belt(CAOB),the Earth’s largest Phanerozoic accretionary orogenic belt,is located between the Siberian,Tarim and North China Cratons and the Kazakhstan composite continent(Fig.1a).It is ca.800 km wide and extends from the Ural Mountains in the west to the Pacific in the east(e.g.,Zonenshain et al.,1990;Mossakovsky et al.,1993;Jahn et al.,2000;Windley et al.,2007,Xiao et al.,2010;Safonova et al.,2011).In the past two decades,many studies have shown that the CAOB is composed of many terranes of different tectonic origins,and was formed by successive accretion of terranes,microcontinents,island arcs,seamounts,ophiolites,and accretionary prisms from the early Neoproterozoic to the late Palaeozoic(e.g.,Mossakovsky et al.,1994;Badarch et al.,2002;Xiao et al.,2003;Buslov et al.,2001;Kovalenko et al.,2004;Safonova,2009;Li,2006;Kröner et al.,2007,2014;Donskaya et al.,2013;Xu et al.,2013).展开更多
Based on geological, chronological, geochemical and Nd isotopic studies of the high-grade basement of the Qilian terrane, the authors have drawn the following main conclusions: (1) the high-grade basement of the Qilia...Based on geological, chronological, geochemical and Nd isotopic studies of the high-grade basement of the Qilian terrane, the authors have drawn the following main conclusions: (1) the high-grade basement of the Qilian terrane consists mainly of meta-argillo-arenaceous rocks and granites and its bulk part was formed in the period of 0.8–1.0 Ga (the Jinningian period); (2) most of the meta-argillo-arenaceous rocks and granitic rocks have strong negative Eu and Ba anomalies (Eu/Eu*= 0.47–0.71 and Ba/Ba*=0.16–0.64), with fDM and ENd (1.0 Ga) ranging from 1.87 to 2.26 Ga and from ?8.54 to ?4.06 respectively, showing relatively high maturity; and (3) the Jinningian granitic rocks are a typical product of continent-continent collision, being probably related to the formation of the supercontinent Rodinia. These studies, combined with the study of high-grade basement rocks near the Qilian terrane, suggest that before the Jinningian period, the Qilian-Qaidam northern-margin terrane and Dunhuang-Alxa terrane were separated from each other, belonging to different plate systems of the North China craton and Yangtze platform respectively. The Qilian orogenic belt was the same as or similar to the Qiling orogenic belt in terms of the geological evolution history at least before the Jinningian period.展开更多
基金grant IDEI-PN-II-ID-PCE-2011-30100 from the Romanian National Science Foundation(ANCS-CNCS)
文摘The basement of the Romanian Carpathians is made of Neoproterozoic to early Paleozoic peri- Gondwanan terranes variably involved in the Variscan orogeny, similarly to other basement terrains of Europe. They were hardly dismembered during the Alpine orogeny and traditionally have their own names in the three Carpathian areas. The Danubian domain of the South Carpathians comprises the Dragsan and Lainici-Paiius peri-Amazonian terranes. The Dragsan terrane originated within the ocean surrounding Rodinia and docked with Rodinia at -800 Ma. It does not contain Cadomian magmatism and consequently it is classified as an Avalonian extra-Cadomian terrane, The Lainici-Pfiius terrane is a Ganderian fragment strongly modified by Cadomian subduction-related magmatism, It is attached to the Moesia platform. The TisoviD terrane is an ophiolite that marks the boundary between Drfagsan and Lainici-Paius terranes. The other basement terranes of the Romanian Carpathians originated close to the Ordovician North- African orogen, as a result of the eastern Rheic Ocean opening and closure. Except for the Sebes-Lotru terrane that includes a lower metamorphic unit of Cadomian age, all the other terranes （Bretila, Tulghes, Negrisoara and Rebra in the East Carpathians, Somes, Biharia and Baia de Aries in the Apuseni mountains, Fagaras, Leaota, Carat and Pades in the South Carpathians） represent late Cambrian-Ordovician rock assemblages. Their provenance, is probably within paleo-nortbeast Africa, close to the Arabian-Nubian shield. The late Cambrian-Ordovician terranes are defined here as Carpathian-type terranes. According to their lithostratigraphy and origin, some are of continental margin magmatic arc setting, whereas others formed in rift and back-arc environment and closed to passive continental margin settings. In a paleo- geographic reconstruction, the continental margin magmatic arc terranes were first that drifted out, followed by the passive continental margin terranes with the back-arc terranes in their front. They accreted to Laurussia during the Variscan orogeny. Some of them （Sebes-Lotru in South Carpathians and Baia de Aries in Apuseni mountains） underwent eclogite-grade metamorphism. The Danubian terranes, the Bretila terrane and the Somes terrane were intruded by Variscan granitoids.
基金financially supported by the National Natural Science Foundation of China(Grant No.42074090)
文摘Numerous geophysical studies have revealed the lithospheric structure of the Qiangtang and the Songpan-Ganzi terranes in the eastern Tibetan Plateau.However,crust-mantle evolution and crustal response to the Indian lithospheric subduction are still controversial.Answering these questions requires additional information regarding crustal structure.In this study,the 2-D normalized full gradient(NFG)of the Bouguer gravity anomaly was used to investigate anomalous sources and interpret the crustal structure underneath the Qiangtang and Songpan-Ganzi terranes.The NFG-derived structures with loworder harmonic numbers(N=33 and N=43)showed that an anomalous source beneath the southern Qiangtang terrane had a characteristic northeastward-dipping shape,suggesting the northeastward motion of the crustal material induced by underthrusting Indian lithospheric mantle.The NFG images with harmonic number N=53 showed a large-scale anomalous source in the lower crust of the transformational zone from the Qiangtang terrane to the Songpan-Ganzi terrane,consistent with thickening crust and resistance of lower crustal flow.The anomalous source demonstrated by the NFG results with harmonic number N=71,located in the upper crust underneath the Ganzi-Yushu fault,suggested a seismogenic body of the 2010 M6.9 Yushu event.
文摘Two terranes formed since the Late Palaeozoic can be distinguished in southwestern China. One is charac-terized by the Permo-Carboniferous ice-rafted marine gravel-bearing clastic formation and the cold-water faunaof the Gondwana facies, including the Gangmar Co, Lhasa, Sa' gya, Tengchong and Baoshan terranes and theother is marked by the Upper Palaeozoic of the Yangtze type with the Cathaysian flora and the Pacific-typefusulinids, comprising the Changning-Menglian, Shuangjiang-Lancang, Qamdo and Bayan Har terranes. TheLongmu Co-Shuanghu-Dengqen-North Lancang River-Kejie-Mengding suture zone between the two groups ofterranes is the boundary between Gondwana and Pacifica in southwestern China. On the grounds of thesedimentary formation and successive southwestward migration of the Asian nonmarine Jurassic-Cretaceousendemic bivalves, the ages of the suture and some terranes to the southwest of the suture zone are discussed.The Baoshan terrane and the Nyainrong-Sog terrane in the Lhasa composite terrane were firstly pieced togeth-er with the Asian continent in the early Early Jurassic. The northern Tibet-western Yunnan microplate, in-cluding the Gangmar Co, Lhasa and Tengchong terranes, collided with the Asian continent at the end of theEarly Cretaceous Neocomian.
基金financially supported by the Natural Science Foundation of China (Nos. 41573039 41673040 U1603245)
文摘The paper presents an overview of the relationships between the interior structures of tectonic terranes and the distribution of tectonic-metallogenic zones in Southeast Asia. Episodic tectonic activities occurred in this archipelagic area, generating metallogenic belts in multi-terranes. Since the Late Paleozoic, opening and closure of the Paleotethys and Neotethys led to multiple suture zones between different blocks, mainly between the Indochina terrane, the Nambung terrane, the Sibumasu terrane and the West Myanmar terrane. During the Mesozoic to Cenozoic, the formation of accreted terranes and their related islands was caused by subduction and collision processes between the Pacific and Australian plates toward the Eurasian Continent, forming Sundaland and its affiliated islands, the Philippines and its subsidiary islands, the Papua New Guinea terrane and its related islands and the Sunda epicontinental arc system. Within the margin of terranes resulted in the structural transfer zones, their secondary tectonic units can be divided into island arc belts, back-arc basins, suture zones, marginal fold belts and orogenic belts. The metallogenic assemblages are mainly distributed within these structural zones of the terranes. According to the relationship between these tectonic units and the distribution of mineral resources, the tectonic-metallogenic belts can be divided into 24 metallogenic belts in Southeast Asia. They are characterized by a diversity and frequency of metallogenic material combination which is likely to reflect the complexity of the material distribution during mineralization processes, mostly by the structural transformation during the dissociation-convergence process between multiple terranes. Therefore, the formation of ore deposits was not only restricted by the evolution(opening and closure) of Paleo-and Neotethys, but may also be controlled by the interaction of the terranes with different tectonic attributes which provided multiple sources of metallogenic material.
基金This paper is one of the results of the project"The Golmud-Ejin Geoscience Transect Interdisciplinary Research".The project was supported by the former Ministry of Geology and Mineral Resources(MGMR)and the National Natural Science Foundation of China(NNSFC).The leaders of the Project are Profs.Wang Zeju,Wu Gongjian and Xiao Xuchang.
文摘Abstract: Through a study of the geotransect from Golmud to Ejin Qi published recently, the tectonics of the crust beneath the area from the northern Qinghai-Tibet plateau (Qaidam and the Qilian Mountains) to the border between China and Mongolia and its structure, composition and tectonic evolution have been revealed, and abundant information about the deep structures has been provided. Based on the research into the geotransect, it is suggested that the crust in this area was formed by the assembly of the terranes in different geological stages. Following the formation of the Palaeo-Asian continent, the north part of the corridor of the transect became a part of the huge unifying continent by the end of the Early Permian. In the Mesozoic and Cenozoic, as a result of the compression mainly by the push of the Qinghai-Tibet plateau on the south, the unique crustal structure and geomorphologic features on the northern Qinghai-Tibet plateau were formed. This geotransect together with the Yadong-Golmud geotransect constitutes a long geotransect which runs across the western Chinese continent.
文摘It is one of hot issues in Tibetan research that is to study the mode,process and kinetics of the crustal shortening during Mesozoic-Cenozoic.In this paper, on the basis of systematic collection,analysis and research of the existing data and results from Himalayas,Lhasa and Qiangtang terranes,we conducted the balanced cross-section study.In the north Qiangtang,the line-balanced cross-section
基金Project supported by the National Natural Science Foundation of China.
文摘The extensive tracing of Nd, Sr and Pb isotopes has revealed that there exist high-degree heterogeneities in suboceanic mantle and mantle anomalies of the Southern Hemisphere on a large scale (DUPAL, high <sup>87</sup>Sr/<sup>86</sup>Sr, and HIMU, high μ value, i. e. <sup>238</sup> U/<sup>204</sup>pb). Recently, the isotopic tracing of the Cenozoic Volcanics from the continent of China has confirmed that there exists a general tendency that the subcontinental mantle of eastern China was en-
基金supported by the National Natural Sciences Foundation of China(Nos.42372005,41830320,41972033)。
文摘The Raohe area of Heilongjiang Province,Northeast China belongs to the Nadanhada Terrane,which was in low latitudes of Panthalassa during the Triassic.The composition of the Late Triassic conodont fauna,derived from limestone lenses interpreted to formed on seamounts,provides important new information on the pelagic biota in this ocean.New conodont samples collected from sections at Minzhu,Minnan and Chigangbei sections belong to three Norian conodont zones.In ascending order,they are:Mockina postera Zone,Mockina bidentata Zone and Parvigondolella andrusovi Zone.The Norian conodont fauna in the Raohe area has distinct attributes:there are a lot of cosmopolitan species(e.g.,Mockina postera,Mockina bidentata,Parvigondolella andrusovi)which enable good global correlation;endemic conodont species are also present(e.g.,Mockina sakurae,Mockina shamiseni,Norigondolella nadanhadaensis)indicating that Panthalassa Ocean conodont populations also contained unique taxa;and some conodonts belong to taxa with much shorter ranges in surrounding epeiric seas(e.g.,Carnepigondolella pseudoechinata,Neocavitella cavitata and Epigondolella vialovi).The presence of the latter“relicts”indicates that the seamounts were persistently suitable habitats for many millions of years in the Late Triassic.
基金funded by the India-Brazil bilateral co-operation Project:INT/BRAZIL/P-02/2013by Indian Statistical Institute,Geoscience Institute of São Paulo University,Brazil and Department of Geology,University of Calcutta.M.Hueck thanks FAPESP for a post-doctoral fellowship(grant 2019/06838-2).
文摘The Southern Granulite Terrane(Dharwar Craton),South India,is a key unit for understanding the origin of charnockite.New U-Pb and Lu-Hf analyses in zircon crys-tals from 16 samples representing a wide variety of litho-types from the quarries in Kabbaldurga reveal a complex geological history in the Archean and early Paleoprotero-zoic.Magmatic protoliths predominantly record Paleoar-chean ages between 3.4 and 3.2 Ga.Combined U-Pb and Lu-Hf signatures indicate a history of recurrent crustal anatexis,juvenile magmatic input,and felsic injections.Mesoarchaean magmatic charnockites were generated mainly from hornblende-dehydration melting of Paleoar-chaean mafic rocks.In addition,Peninsular Gneissic Com-plex of the Dharwar Craton,commonly described as TTG suites,are likely generated by melting of hydrated basalt.The new data are consistent with the idea of a convecting magmatic cycle and also support the proposal that the southern Dharwar Craton comprises a tilted cross-sec-tion through the Archaean crust.Paleoproterozoic high-temperature event is documented here as a complex unit involving juvenile mafic magmatism,granulite facies imprints and crustal anatexis as well as felsic injections,occurring within a short time period around 2.5 Ga.
基金the National Key Research and Development Program of China(Grant No.2022YFF0800903)the National Natural Science Foundation of China(Grant Nos.42302107,92162322,42261144669,41922022,42003036)+4 种基金the China Geological Survey(Grant Nos.DD20243512,DD20230008)the National Postdoctoral Research Program of China(Grant No.GZC20232489)the Second Tibetan Plateau Scientific Expedition and Research(Grant No.2021QZKK0304)Xing Dian Youth Talent Plan of Yunnan Province(Grant No.XDYC-QNRC-2022-0136)the UNESCO:IUGS IGCP-662 Program。
文摘Basalts from the Late Carboniferous to Early Permian are extensively developed in the central Lhasa subterrane,southern Xizang.Studying the petrogenesis of these rocks may have implications for the late Paleozoic arc magmatism along the central Lhasa subterrane uncovering more of the evolution of the Sumdo Paleo-Tethys Ocean and its dynamic mechanism.Basalt samples from the Luobadui Formation in the Leqingla area,NW of Linzhou City in the central Lhasa subterrane,southern Xizang exhibit arc-like geochemical signatures in a subduction-zone tectonic setting characterized by high Al_(2)O_(3)and low TiO_(2)contents,fractionated REE patterns with low Nb/La ratios and high LREE concentrations,and negative HFSE anomalies.Based on their higher Th/Ce,Nb/Zr,and lower Ba/Th,Pb/Nd ratios,slightly negative to positiveε_(Nd)(t)values,and the relatively high Sr-Pb isotopic compositions,these samples were probably derived from partial melting of a depleted mantle source of garnet+spinel lherzolite,metasomatized by subducted sediments around 297 Ma.Modeling of the trace elements indicates that these basalts experienced fractional crystallization of olivine,clinopyroxene and minor plagioclase during magma ascent and eruption.It is proposed that these Late Carboniferous–Early Permian basalts are associated with the northward subduction of the Sumdo Paleo-Tethys Ocean seafloor along the southern margin of the central Lhasa subterrane.
基金This work was supported by National Key Research and Development Program of China(Grant No.2022YFF0503100)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB 41000000).
文摘The Moon has been divided into three terranes:Procellarum KREEP Terrane(PKT),Feldspathic Highland Terrane(FHT),and South Pole-Aitken Terrane(SPAT),using globally measured Th and FeO.Many lunar evolu-tion models have predicted that a lunar magma ocean will produce a residual layer enriched in incompatible elements such as K,REE,and P(i.e.,KREEP)in the late age of crys-tallization;and that the distribution of thorium can be used as a proxy for determining the global distribution of KREEP.The thorium distribution in these three terranes is inhomo-geneous.The highest concentration of thorium is in PKT,the medium concentration of thorium is in SPAT,and almost none in FHT.Then what is the specific distribution in each of the terrane and what enlightenment can it tell us?Here we present and describe the detailed thorium distribution in PKT,SPAT,and FHT and provide some information for the origin of asymmetries on the lunar surface.
基金supported by the Key Laboratory of Gold Mineralization Processes and Resource Utilization,MNRShandong Provincial Key Laboratory of Metallogenic Geological Process and Resource Utilization(Grant No.KFKT202103)National Natural Science Foundation of China(Grant No.41876037)。
文摘Feldspar Pb isotopes have been widely used to trace magmatic formation and evolution processes.However,it remains unclear whether post-magmatic thermal events can affect feldspar Pb isotopic ratios.Here,the in situ Pb isotopic composition of feldspar hosted in granitic rocks(thirteen Archean and one Paleoproterozoic)from the northern Kongling terrane,Yangtze Craton,South China,is analyzed.The samples reveal a substantial variation in their Pb isotopic composition,spanning the gap between the 1.9 Ga and present-day geochrons,which indicates extensive resetting by later tectonothermal events.This resetting was interpreted to have likely resulted from Paleoproterozoic and Neoproterozoic tectonothermal events related to the assembly and breakup of the Columbia and Rodinia supercontinents.These results suggest that Pb isotopes should be used cautiously when tracing magma sources and petrogenesis in magmatic rocks that have experienced post-magmatic reworking.However,the in situ Pb isotopic composition of feldspar in ancient granitoids may also potentially be used to reveal later tectonothermal events.The extensive resetting of the Pb isotopic composition in feldspar by regional thermal events may also provide new insights into our understanding of the Pb isotope paradox.
基金China Geological Survey(Grant No.20013000166) Natural Science Foundation of China(Grant No.49902006).
文摘Mafic granulites have been found as structural lenses within the huge thrust system outcropping about 10 km west of Nam Co of the northern Lhasa Terrane, Tibetan Plateau. Petrological evidence from these rocks indicates four distinct metamorphic assemblages. The early metamorphic assemblage (M1) is preserved only in the granulites and represented by plagioclase+hornblende inclusions within the cores of garnet porphyroblasts. The peak assemblage (M2) consists of garnet+clinopyroxene+hornblende+plagioclase in the mafic granulites. The peak metamorphism was followed by near-isothermal decompression (M3), which resulted in the development of hornblende+plagioclase symplectites surrounding embayed garnet porphyroblasts, and decompression-cooling (M4) is represented by minerals of hornblende+plagioclase recrystallized during mylonization. The peak (M2) P-T conditions of garnet+ clinopyroxene+plagioclase+hornblende were estimated at 769-905℃ and 0.86-1.02 GPa based on the geothermometers and geobarometers. The P-T conditions of plagioclase+hornblende symplectites (M3) were estimated at 720-800℃ and 0.55-0.68 GPa, and recrystallized hornblende+plagioclase (M4) at 594-708℃ and 0.26-0.47 GPa. It is impossible to estimate the P-T conditions of the early metamorphic assemblage (M1) because of the absence of modal minerals. The combination of petrographic textures, metamorphic reaction history, thermobarometric data and corresponding isotopic ages defines a clockwise near-isothermal decompression metamorphic path, suggesting that the mafic granulites had undergone initial crustal thickening, subsequent exhumation, and cooling and retrogression. This tectonothermal path is considered to record two major phases of collision which resulted in both the assemblage of Gondwanaland during the Pan-African orogeny at 531 Ma and the collision of the Qiangtang and Lhasa Terranes at 174 Ma, respectively.
文摘We investigate the effect of the westerly rotation of the lithosphere on the active margins that surround the Americas and find good correlations between the inferred easterly-directed mantle counterflow and the main structural grain and kinematics of the Andes and Sandwich arc slabs.In the Andes,the subduction zone is shallow and with low dip,because the mantle flow sustains the slab;the subduction hinge converges relative to the upper plate and generates an uplifting doubly verging orogen.The Sandwich Arc is generated by a westerly-directed SAM(South American) plate subduction where the eastward mantle flow is steepening and retreating the subduction zone.In this context,the slab hinge is retreating relative to the upper plate,generating the backarc basin and a low bathymetry single-verging accretionary prism.In Central America,the Caribbean plate presents a more complex scenario:(a) To the East,the Antilles Arc is generated by westerly directed subduction of the SAM plate,where the eastward mantle flow is steepening and retreating the subduction zone.(b) To the West,the Middle America Trench and Arc are generated by the easterly-directed subduction of the Cocos plate,where the shallow subduction caused by eastward mantle flow in its northern segment gradually steepens to the southern segment as it is infered by the preexisting westerly-directed subduction of the Caribbean Plateau.In the frame of the westerly lithospheric flow,the subduction of a divergent active ridge plays the role of introducing a change in the oceanic/continental plate’s convergence angle,such as in NAM(North American)plate with the collision with the Pacific/Farallon active ridge in the Neogene(Cordilleran orogenic type scenario).The easterly mantle drift sustains strong plate coupling along NAM,showing at Juan de Fuca easterly subducting microplate that the subduction hinge advances relative to the upper plate.This lower/upper plate convergence coupling also applies along strike to the neighbor continental strike slip fault systems where subduction was terminated(San Andreas and Queen Charlotte).The lower/upper plate convergence coupling enables the capture of the continental plate ribbons of Baja California and Yakutat terrane by the Pacific oceanic plate,transporting them along the strike slip fault systems as para-autochthonous terranes.This Cordilleran orogenic type scenario,is also recorded in SAM following the collision with the Aluk/Farallon active ridge in the Paleogene,segmenting SAM margin into the eastwardly subducting Tupac Amaru microplate intercalated between the proto-LiquineOfqui and Atacama strike slip fault systems,where subduction was terminated and para-autochthonous terranes transported.In the Neogene,the convergence of Nazca plate with respect to SAM reinstalls subduction and the present Andean orogenic type scenario.
文摘The island of New Guinea is the mountainous margin of the Australian continent.Paleozoic and Proterozoic Australian craton extends northward beneath the shallow waters of the Arafura Sea to underlie the southern plains of New Guinea and,with overlying sediments,to form the dramatically sculpted southern slopes of the central range in a great fold and thrust belt.The fold and thrust belt marks the outer limit of the autochthon.Beyond,to the N,E and W,is an aggregation of terranes that have accreted since the Late Cretaceous,driven by oblique convergence between the Pacific and Indo-Australian plates.The terranes comprise continental fragments and blocks of oceanic volcanic arc and of oceanic crust and mantle origin,and include two great ophiolites.The plate boundary itself is a complex system of microplates,each with separate motion,and marked by every kind of plate boundary.In the E the opening of the Manus Basin is associated with rapid clockwise rotation of New Britain,and the opening of the Woodlark Basin causes extension of continental crust in the Papuan peninsula and islands.This has resulted in the development of low-angle extensional faults and domal structures in metamorphic rocks and the exhumation of Pliocene eclogite.Remarkably similar extensional structures and the exhumation of Pliocene eclogite are seen in the Bird’s Head area of western New Guinea(Wandamen Peninsula).
文摘The Pilbara region of Western Australia is one of only two areas on Earth–the other being the Kaapvaal Craton of southern Africa–that contain well preserved,nearcontinuous geological records of crustal evolution from the Paleoarchean into the late Paleoproterozoic.The Pilbara is famous for hosting fossil evidence of early life(stromatolites and microfossils),and for containing a record of the early Archean atmosphere.The geological record extends from granite–greenstone terranes and overlying clastic basins of the 3.53–2.83 Ga Pilbara Craton,across a major unconformity,to a series of 2.78–1.79 Ga volcanic and sedimentary successions.Between 3.53–3.23 Ga,a succession of mantle plume events formed a thick volcanic plateau on older continental crust,remnants of which include enclaves of c.3.6 Ga granitic gneiss and abundant 3.8–3.6 Ga inherited and detrital zircons.During each of the plume events,the volcanic plateau was intruded by crustally-derived granitic rocks,leading to vertical deformation by partial convective overturn.By 3.23 Ga,these processes had established thick continental crust that was then rifted into three microplates separated by c.3.2 Ga basins of oceanic crust.Subsequent plate tectonic processes to 2.90 Ga included subduction,terrane accretion,and orogeny.From 2.78–2.63 Ga the northern Pilbara Craton was affected by minor rifting,followed by deposition of thick basaltic formations separated by felsic volcanic and sedimentary rocks(Fortescue Basin).Rifting in the southern Pilbara resulted in progressively deepening marginal basin sedimentation,including thick units of banded iron formation(Hamersley Basin:2.63–2.45 Ga).
文摘The Earth Science Division of the School of Geography,Earth Science and Environmental(SGESE)of the University of the South Pacific(USP)in Suva Fiji in association with its International Research Office hosted an international meeting on“Subduction,Volcanism and the Evolution of Oceanic and Continental Crust”that was held on 9-16 February 2014 at the Tanoa International Hotel in Nadi,Fiji.The meeting was followed by a 2-day excursion to Eocene-Miocene arc terranes in the north and western parts of the island of Viti Levu including the early-arc Yavuna Group which is intruded by a large tonalite body.
基金funded by the Australian Research Council(DP0986762).
文摘A series of tight bends(oroclines)are recognised in the late Paleozoic–early Mesozoic southern New England Orogen between Brisbane and Newcastle,but their exact geometry and tectonic evolution are still debated.This contribution provides an outline of the different tectonic elements within the orogen and the relationships of these elements with the oroclinal structure.Pre-oroclinal tectonic elements were derived from a Devonian–Carboniferous subduction zone,and include forearc basin terranes and accretionary wedge rocks that are separated from each other by a narrow belt of serpentinites and high-pressure rocks.Rocks are predominantly steeply dipping and their map-view pattern delineates three bends:the Z-shaped Texas and Coffs Harbour oroclines in the north and the U-shaped Manning Orocline in the south.During the early Permian(298–288 Ma),the area was affected by widespread,mostly S-type,magmatism that heralded a period of crustal extension accompanied by the formation of sedimentary rift basins.The spatial distribution of early Permian granitoids mimics the shape of the oroclines,which further defines a fourth bend,the Nambucca Orocline.Whether these curvatures formed by bending of a quasi-linear belt,or as primary early Permian arcuate features,is an unresolved question that warrants further paleomagnetic,geochronological and structural investigations.
文摘The Central Asian Orogenic Belt(CAOB),the Earth’s largest Phanerozoic accretionary orogenic belt,is located between the Siberian,Tarim and North China Cratons and the Kazakhstan composite continent(Fig.1a).It is ca.800 km wide and extends from the Ural Mountains in the west to the Pacific in the east(e.g.,Zonenshain et al.,1990;Mossakovsky et al.,1993;Jahn et al.,2000;Windley et al.,2007,Xiao et al.,2010;Safonova et al.,2011).In the past two decades,many studies have shown that the CAOB is composed of many terranes of different tectonic origins,and was formed by successive accretion of terranes,microcontinents,island arcs,seamounts,ophiolites,and accretionary prisms from the early Neoproterozoic to the late Palaeozoic(e.g.,Mossakovsky et al.,1994;Badarch et al.,2002;Xiao et al.,2003;Buslov et al.,2001;Kovalenko et al.,2004;Safonova,2009;Li,2006;Kröner et al.,2007,2014;Donskaya et al.,2013;Xu et al.,2013).
基金supported by China National Natural Science Foundation Grant 49732070.
文摘Based on geological, chronological, geochemical and Nd isotopic studies of the high-grade basement of the Qilian terrane, the authors have drawn the following main conclusions: (1) the high-grade basement of the Qilian terrane consists mainly of meta-argillo-arenaceous rocks and granites and its bulk part was formed in the period of 0.8–1.0 Ga (the Jinningian period); (2) most of the meta-argillo-arenaceous rocks and granitic rocks have strong negative Eu and Ba anomalies (Eu/Eu*= 0.47–0.71 and Ba/Ba*=0.16–0.64), with fDM and ENd (1.0 Ga) ranging from 1.87 to 2.26 Ga and from ?8.54 to ?4.06 respectively, showing relatively high maturity; and (3) the Jinningian granitic rocks are a typical product of continent-continent collision, being probably related to the formation of the supercontinent Rodinia. These studies, combined with the study of high-grade basement rocks near the Qilian terrane, suggest that before the Jinningian period, the Qilian-Qaidam northern-margin terrane and Dunhuang-Alxa terrane were separated from each other, belonging to different plate systems of the North China craton and Yangtze platform respectively. The Qilian orogenic belt was the same as or similar to the Qiling orogenic belt in terms of the geological evolution history at least before the Jinningian period.
