A synthesis involving the data for the Nalati mountain region（NMR） in west Tianshan with a dataset including zircon U-Pb ages, Hf isotopic composition, major and trace elements of Paleozoic intrusions are presented ...A synthesis involving the data for the Nalati mountain region（NMR） in west Tianshan with a dataset including zircon U-Pb ages, Hf isotopic composition, major and trace elements of Paleozoic intrusions are presented to improve the understanding of regional geodynamic evolution. Paleozoic intrusive rocks in the NMR could be classified into four categories based on chronological and geochemical data： 480？5 Ma, 445–410 Ma, 345–320 Ma, and 295 Ma, which correspond to（1） closure of the Terskey Ocean and the opening of the south Tianshan back-arc basin, which was followed with the opening of the south Tianshan Ocean,（2） initial subduction of the south Tianshan oceanic crust,（3） major subduction stage, and（4） collision to post-collisional stage, respectively. Following the closure of the Terskey Ocean, the south Tianshan Ocean opened at Early Silurian and subducted under Yili-central Tianshan by the end of Early Carboniferous Period. The following breakoff of the subducted slab triggered partial melting of continental crust and formed voluminous granitic rocks in the NMR.展开更多
Ophiolitic peridotites exposed in the Eastern Desert(ED)of Egypt record multiple stages of evolution,including different degrees of partial melting and melt extraction,serpentinization,carbonatization and metamorphism...Ophiolitic peridotites exposed in the Eastern Desert(ED)of Egypt record multiple stages of evolution,including different degrees of partial melting and melt extraction,serpentinization,carbonatization and metamorphism.The present study deals with metaperidotites at two selected localities in the central and southern ED,namely Wadi El-Nabáand Wadi Ghadir,respectively.They represent residual mantle sections of a Neoproterozoic dismembered ophiolite that tectonically emplaced over a volcano-sedimentary succession that represents island–arc assemblages.The studied metaperidotites are serpentinized,with the development of talc-carbonate and quartz-carbonate rocks,especially along shear and fault planes.Fresh relics of primary minerals(olivine,orthopyroxene and Cr-spinel)are preserved in a few samples of partiallyserpentinized peridotite.Most of the Cr-spinel crystals have fresh cores followed by outer zones of ferritchromite and Crmagnetite,which indicates that melt extraction from the mantle protolith took place under oxidizing conditions.The protoliths of the studied metaperidotites were dominated by harzburgites,which is supported by the abundance of mesh and bastite textures in addition to some evidence from mineral and whole-rock chemical compositions.The high Cr#(0.62–0.69;Av.0.66)and low TiO_(2)(<0.3 wt%)contents of the fresh Cr-spinels,the higher Fo(89–92;Av.91)and NiO(0.24–0.54 wt%,Av.0.40)contents of the primary olivine relics,together with the high Mg#(0.91–0.93;Av.91)and low CaO,Al2 O3 and TiO_(2)of the orthopyroxene relics,are all comparable with depleted to highly depleted forearc harzburgite from a suprasubduction zone setting.The investigated peridotites have suffered subsequent phases of metasomatism,from oceanfloor hydrothermal alteration(serpentinization)to magmatic hydrothermal alteration.The enrichment of the studied samples in light rare earth elements(LREEs)relative to the heavy ones(HREEs)is attributed to most probably be due to the contamination of their mantle source with granitic source hydrothermal fluids after the obduction of the ophiolite assemblage onto the continental crust.The examined rocks represent mantle residue that experienced different degrees of partial melting(~10%to 25%for W.El-Nabárocks and~5%to 23%for W.Ghadir rocks).Variable degrees of partial melting among the two investigated areas suggest mantle heterogeneity beneath the Arabian-Nubian Shield(ANS).展开更多
In recent years,explosion of research in the early Tertiary mammals of India has attracted widespread interest because of the importance of this fauna in understanding biogeographic origins,early evolution,and dispers...In recent years,explosion of research in the early Tertiary mammals of India has attracted widespread interest because of the importance of this fauna in understanding biogeographic origins,early evolution,and dispersal patterns of several modern mammal orders as well for its paleogeographic implications.Although Paleocene mammals are yet to be discovered in the Indian subcontinent,Indian Early Eocene mammal faunas are now becoming increasingly important in debates concerning the origins of several modern terrestrial orders.展开更多
The distribution of Eocene-Oligocene turbidite facies in the Pindos foreland and the paleocurrent directions of submarine fan deposits,of the Peloponnesus area,document the proximal part of an underfilled foreland bas...The distribution of Eocene-Oligocene turbidite facies in the Pindos foreland and the paleocurrent directions of submarine fan deposits,of the Peloponnesus area,document the proximal part of an underfilled foreland basin.The definition of Pindos foreland basin attributes sediment accommodation solely to flexural subsidence driven by topographic load of the thrust belt and sediment loads in the foreland basin.The restriction of the coarse grained deposits and the basin underfilled conditions are related to the Pindos foreland evolution,and especially to the internal thrusting and produced intrabasinal highs.The presence of strike-slip faults can affect the geometry of a basin by causing changes in depth and width,resulting in the transformation from a uniform to non-uniform configuration.This change has an intensive impact on depositional environments along the basin axis.Strike-slip faults that cross-cut intrabasinal highs produce pathways for the sediment distribution on both sides of the highs.Distributary channels that discharge into the basin are perpendicular to its axis and shift axially at the basin floor.The strikeslip and thrust faulting operated contemporaneously for much of their active periods,although it appears that thrust faulting,initiated slightly earlier than strike-slip faulting.展开更多
This workshop and pre-workshop fieldtrip were organized by the Institute ofGeology and Mineralogy,Siberian Branch,Russian Academy of Sciences(SB RAS)andco-sponsored by the Presidium of the SiberianBranch of the Russia...This workshop and pre-workshop fieldtrip were organized by the Institute ofGeology and Mineralogy,Siberian Branch,Russian Academy of Sciences(SB RAS)andco-sponsored by the Presidium of the SiberianBranch of the Russian Academy of Science(SB RAS),Centre for Russian and CentralEurAsian Mineral Studies(CERCAMS),andTask Force 1(ERAS)of the InternationalLithosphere Program(ILP).This waspreceded by a field excursion to Gorny Altayin Southwestern Siberia(June 20-28,2010),which,in the literature,is also referred to asMountainous Altay or Russian Altay.Thefield excursion and the workshop attractedeighteen participants from 8 countries,namely Germany,England,Japan,China,France,Czech Republic,Poland and Russia.The main goal of this workshop was todiscuss the general evolution of the CentralAsian Orogenic Belt(CAOB)with a specialemphasis to the problems of continentalgrowth,evolution of palaeo-oceans and activecontinental margins,collisional tectonicsand metallogeny based on results of previousfield missions and analytical research.Thiswould contribute to our understanding of the Late Neoproterozoic to Palaeozoic evolutionof the Altay belt and to establish up-to-datemodels of ocean closure,continentalaccretion/assembly and intracontinentalorogeny.展开更多
Introduction Geology of the Indian subcontinent is not only diverse and interesting but also has been studied for a long period.Reflection of a rich geoscientific heritage may be illustrated by a couple of lesser know...Introduction Geology of the Indian subcontinent is not only diverse and interesting but also has been studied for a long period.Reflection of a rich geoscientific heritage may be illustrated by a couple of lesser known early or first“discoveries/descriptions”from the Indian subcontinent.Heinrich(1966)in his book“The Geology of Carbonatites”mentions that the first description of carbonatite was provided from India by Bose(1884)as quoted below(italics and bold for emphasis).展开更多
The Proterozoic metasedimentary rocks of the Yaounde Group on the northern edge of the Congo Shield in Central Africa were investigated to understand their provenance and depositional environment.Petrography,geochemis...The Proterozoic metasedimentary rocks of the Yaounde Group on the northern edge of the Congo Shield in Central Africa were investigated to understand their provenance and depositional environment.Petrography,geochemistry,and field evidence helped to subdivide the metasediments into paragneiss,mica schist,chlorite schist,and quartzite which were derived from greywacke,shale,quartz arenite,litharenite protoliths.They are immature with some mature samples,moderately weathered and reworked Neo-and Post-Archean metasediments.Rare earth element signatures(Chondrite Eu/Eu^(*)≤1),enrichment of light rare earth elements over the heavy ones,and the La/Sc ratio(>0.7)are compatible with those of the intermediate and felsic sources from the upper continental crust.These metasediments were deposited in the continental arc setting and have evolved during Proterozoic times according to the Wilson cycle to form the West Gondwana including NE Brazil.展开更多
The Tan-Lu fault zone(TLFZ)along the East China continental margin experienced sinistral movement at the beginning of Early Cretaceous(ca.145)due to fast oblique subduction of the Izanagi Plate in the Pacific Ocean.It...The Tan-Lu fault zone(TLFZ)along the East China continental margin experienced sinistral movement at the beginning of Early Cretaceous(ca.145)due to fast oblique subduction of the Izanagi Plate in the Pacific Ocean.It can展开更多
This paper summarizes recent data about magnesite and talc genesis in Carboniferous host rocks of Western Carpathians (Slovakia) , which occur in two distinct belts in tectonic superunit Veporicum and its contact zone...This paper summarizes recent data about magnesite and talc genesis in Carboniferous host rocks of Western Carpathians (Slovakia) , which occur in two distinct belts in tectonic superunit Veporicum and its contact zone with Gemericum. The northern Sinec magnesite and talc belt (with main deposits Kokava, Sinec, Samo, Hnust'a-Mutnik) contains economic accummulation of magnesite and talc, while in the southern Ochtina belt ( main deposits in Dubrava massif-Dubrava, Mikova, Jedl'ovec; Lubenik, Ochtina, Kosice-Bankov, Banisko, Medvedia) the magnesite is dominating.The magnesite genesis by successive replacement of Carboniferous calcite to dolomite and magnesite during metamorphic process Ml (northern belt 280-400℃; , southern belt 370-420℃: ; Radvanec & Prochaska, 2001; Kodera & Radvanec, 2002) , being supplied by Mg from Permoscythian evaporitic bittern brines, relates to Variscan post-collisional (post-VD) evolution. The extensional tectonics and the high heat flow facilitated the generation of a hydrothermal system.The time-separated later metamorphic and sourcely different fluid flow event (M2; 1. c. ) produced talc. Tectonic, microtectonic, metamorphic and geochronological data relate the talc origin with the Alpine Upper Cretaceous (88-84 Ma; Maluski in Kovacik et al. , 1996) tectonothermal event AD2. This event, being the consequence of Alpine collisional ( AD1 ) crustal thickening and metamorphic core complex origin, meant regional extension and pervasive fluid flow of open system in crustal discontinuities. This process was prominent in the northern belt ( Sinec shear zone) located more closely to Veporic thermal dome, while towards its peripheral parts (southern Ochtina belt) the M2 metamorphic process and steatitization gradually weakened.Studies from Sinec shear zone (being the prominent AD2 -AD3 structure of northern Sinec belt) , where the dolomite/magnesite lenses (replacement in M1) and their accompanying lithology were in AD1 sandwitched between more competent basement blocks, proved in AD2 the pervasite steatitization, the talc and dolomite 2 origin in extensional microstructures ( metamorphic process M2; 490 -540℃, 240-330 MPa, 1. c. ).The economic accummulations of talc in Sinec belt are the products of antithetic shearing during the AD3 phase, being the gradual continuation of AD2 ( change of kinematics from unroofing to regional transpressional shearing). Contrary to the northern Sinec belt having located the AD3 deformation into narrow shear zone with soft lithology surrounded by hard lithology, in southern Ochtina belt the deformation AD3 was accommodated by wide soft rock column with rigid carbonate blocks floating inside. The lower P-T ( M2)conditions and deformational gradient in Ochtina belt during AD2 and AD3 phases caused why no economic talc accummulations developed there.The results of presented study can be used as general criteria for magnesite and talc prospection in Alpine type terranes.展开更多
The Late Triassic to Paleogene （T3-E） basin occupies an area of 143100 km^2, being the sixth area of the whole of SE China; the total area of synchronous granitoid is about 127300 km^2; it provides a key for underst...The Late Triassic to Paleogene （T3-E） basin occupies an area of 143100 km^2, being the sixth area of the whole of SE China; the total area of synchronous granitoid is about 127300 km^2; it provides a key for understanding the tectonic evolution of South China. From a new 1：1500000 geological map of the Mesozoic-Cenozoic basins of SE China, combined with analysis of geometrical and petrological features, some new insights of basin tectonics are obtained. Advances include petrotectonic assemblages, basin classification of geodynamics, geometric features, relations of basin and range. According to basin-forming geodynamical mechanisms, the Mesozoic-Cenozoic basin of SE China can be divided into three types, namely： 1） para-foreland basin formed from Late Triassic to Early Jurassic （T3-J1） under compressional conditions; 2） rift basins formed during the Middle Jurassic （J2） under a strongly extensional setting; and 3） a faulted depression formed during Early Cretaceous to Paleogene （K1-E） under back-arc extension action. From the rock assemblages of the basin, the faulted depression can be subdivided into a volcanic-sedimentary type formed mainly during the Early Cretaceous （K1） and a red -bed type formed from Late Cretaceous to Paleogene （K2-E）. Statistical data suggest that the area of all para-foreland basins （T3-J1） is 15120 km^2, one of rift basins （J2） occupies 4640 km^2, and all faulted depressions equal to 124330 km^2 including the K2-E red-bed basins of 37850 km^2. The Early Mesozoic （T3-J1） basin and granite were mostly co-generated under a post-collision compression background, while the basins from Middle Jurassic to Paleogene （J2-E） were mainly constrained by regional extensional tectonics. Three geological and geographical zones were surveyed, namely： 1） the Wuyishan separating zone of paleogeography and climate from Middle Jurassic to Tertiary; 2） the Middle Jurassic rift zone; and 3） the Ganjiang separating zone of Late Mesozoic volcanism. Three types of basin-granite relationships have been identified, including compressional （a few）, strike-slip （a few）, and extensional （common）. A three-stage geodynamical evolution of the SE-China basin is mooted： an Early Mesozoic basin-granite framework; a transitional Middle Jurassic tectonic regime; intracontinental extension and red-bed faulted depressions since the Late Cretaceous.展开更多
Early Palaeozoic Cambrian A-type Kathalguri Granites in the Mikir Hills of northeastern (NE) India were studied to better understand the geodynamic settings in this region. This research presents new whole-rock geoche...Early Palaeozoic Cambrian A-type Kathalguri Granites in the Mikir Hills of northeastern (NE) India were studied to better understand the geodynamic settings in this region. This research presents new whole-rock geochemical and Sr, Nd, Pb isotopic data for the Cambrian granites in the Kathalguri Granite in Mikir Hills. The Kathalguri Granite shows geochemical characteristics of high SiO2, K2O and low FeOT, MgO, CaO, and P2O5 compositions. They belong to a high K Shoshonite to ultra-potassic series and display a weak metaluminous to peraluminous feature with A/CNK values of 0.83 to 1.02 with corundum and anorthite normative. FeOT/MgO varies from 2.93 - 7.49, is moderately oxidized and belongs to magnetite series. The rocks have a high ΣREE composition of 370.80 - 1353.23 ppm (average 568.55) and are enriched in LREE with flat HREE and (La/Yb)N values of 8.10 - 18.99, and display obvious strong negative Eu anomalies. Trace elements of the studied granites are characterized by enrichment in Rb, Th, U, Pb, Hf, and Sm, and depletion of Ba, Nb, Ta, and Sr. They display geochemical features of high Zr + Y + Nb + Ce values (241 - 934 ppm) and Ga/Al ratios 2.49 - 3.01 consistent with A-Type granites. Based on particular geochemical features, such as high Rb/Nb (3.10 - 19.53) and Low Y/Nb (0.09 - 2.28), Kathalguri Granite can be further classified as an A1-type subgroup. Granites display relatively low Sr (N ratio varying between 0.53 - 0.89 suggesting that the melts generated at greater depths (18 - 40 km), and fractionation at low pressures (−3 and total HGU 98.96 to 214.20. Kathalguri Granite dated by Rb-Sr isotopic isochrone as 489 ± 19 Ma with an initial 87Sr/86Sr 0.7199 ± 0.0017 and MSWD of 4.1, εSr(I) varied between 161.62 - 332.08 suggests that the Kathalguri Granite have originated from partial melting of ancient, evolved continental crustal material. The Sm-Nd Systematics has given a depleted mantle model (TDM) age ranging from 1733 - 2063 Ma with high negative εNd(t) values (−10.39 to −15.18) also hint at some heterogeneity or multiple source contributions in the melting process of the protolith. Xenoliths of older mafic rocks and Barapani arenites are seen within the Kathalguri Granite and are also supported by geochemical signatures of recycled crustal materials both mafic and sedimentary. It formed during the Cambrian reorganization of lithospheric plate motion related to the Pan-African-Braziliano event.展开更多
Prof.M.Jayananda has been elected as a Fellow of Indian Academy of Sciences in recognition of his research contributions on the Archean magmatism,continental growth and geodynamic evolution of Dharwar craton,southern ...Prof.M.Jayananda has been elected as a Fellow of Indian Academy of Sciences in recognition of his research contributions on the Archean magmatism,continental growth and geodynamic evolution of Dharwar craton,southern India.For the past 30 years he has carried out multidisciplinary research involving field based strain fabric analysis,elemental and isotope tracers.His research has significant impact on understanding the geological and tectonic evolution early earth into a habitable planet.展开更多
During the Late Mesozoic Middle Jurassic--Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacif...During the Late Mesozoic Middle Jurassic--Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic （Type I） and intra-continental extensional basins （Type II）. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tufts and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous-Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geo- dynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc exten- sional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range tectonics between both shores of the Pacific, such as mantle plume formation, scales of extensional and igneous rock assemblages and the age of basin and range tectonics, were caused mainly by the Yellowstone mantle plume in the eastern shore of the Pacific.展开更多
Regional metamorphic rocks preserve records of geodynamic evolution of orogenic belts.The Himalaya represents an evolving mountain belt with a complex geological history and is considered here as a composite of Trans...Regional metamorphic rocks preserve records of geodynamic evolution of orogenic belts.The Himalaya represents an evolving mountain belt with a complex geological history and is considered here as a composite of Trans–Himalaya and the Himalaya per se and the intervening Indus–Tsangpo Suture Zone.Each of these three tectonic domains is evaluated in the context of their metamorphic evolution.An episodic evolution is inferred and described.展开更多
Authored by earnestly active and deeply perceptive earth scientists who had their ears to the ground and eyes roving the panorama of landscape,the 42 papers encompassing this tome speak volume of the range of subjects...Authored by earnestly active and deeply perceptive earth scientists who had their ears to the ground and eyes roving the panorama of landscape,the 42 papers encompassing this tome speak volume of the range of subjects,the nature of the works and the depth of analyses attempted.There is no gainsaying that together these learned papers by those who worked with the rocks,some were among the rocks all their lives,present a coherent and comprehensive narratives of the geodynamic evolution of the Indian subcontinent—a collage of multiple geological provinces such as Proterozoic and Tertiary mobile belts,the Indian Shield riven with graben-forming faults that break the Shield into a number of cratons,the continental margin framing the subcontinent all around,the lava plateau that is now dissected by faults,the Tertiary foreland basin and its sedimentary plains,and the Andaman-Nicobar Island Arc.Also discussed is a chunk of Antarctica.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.41372062, 41330210, 41672047)
文摘A synthesis involving the data for the Nalati mountain region（NMR） in west Tianshan with a dataset including zircon U-Pb ages, Hf isotopic composition, major and trace elements of Paleozoic intrusions are presented to improve the understanding of regional geodynamic evolution. Paleozoic intrusive rocks in the NMR could be classified into four categories based on chronological and geochemical data： 480？5 Ma, 445–410 Ma, 345–320 Ma, and 295 Ma, which correspond to（1） closure of the Terskey Ocean and the opening of the south Tianshan back-arc basin, which was followed with the opening of the south Tianshan Ocean,（2） initial subduction of the south Tianshan oceanic crust,（3） major subduction stage, and（4） collision to post-collisional stage, respectively. Following the closure of the Terskey Ocean, the south Tianshan Ocean opened at Early Silurian and subducted under Yili-central Tianshan by the end of Early Carboniferous Period. The following breakoff of the subducted slab triggered partial melting of continental crust and formed voluminous granitic rocks in the NMR.
文摘Ophiolitic peridotites exposed in the Eastern Desert(ED)of Egypt record multiple stages of evolution,including different degrees of partial melting and melt extraction,serpentinization,carbonatization and metamorphism.The present study deals with metaperidotites at two selected localities in the central and southern ED,namely Wadi El-Nabáand Wadi Ghadir,respectively.They represent residual mantle sections of a Neoproterozoic dismembered ophiolite that tectonically emplaced over a volcano-sedimentary succession that represents island–arc assemblages.The studied metaperidotites are serpentinized,with the development of talc-carbonate and quartz-carbonate rocks,especially along shear and fault planes.Fresh relics of primary minerals(olivine,orthopyroxene and Cr-spinel)are preserved in a few samples of partiallyserpentinized peridotite.Most of the Cr-spinel crystals have fresh cores followed by outer zones of ferritchromite and Crmagnetite,which indicates that melt extraction from the mantle protolith took place under oxidizing conditions.The protoliths of the studied metaperidotites were dominated by harzburgites,which is supported by the abundance of mesh and bastite textures in addition to some evidence from mineral and whole-rock chemical compositions.The high Cr#(0.62–0.69;Av.0.66)and low TiO_(2)(<0.3 wt%)contents of the fresh Cr-spinels,the higher Fo(89–92;Av.91)and NiO(0.24–0.54 wt%,Av.0.40)contents of the primary olivine relics,together with the high Mg#(0.91–0.93;Av.91)and low CaO,Al2 O3 and TiO_(2)of the orthopyroxene relics,are all comparable with depleted to highly depleted forearc harzburgite from a suprasubduction zone setting.The investigated peridotites have suffered subsequent phases of metasomatism,from oceanfloor hydrothermal alteration(serpentinization)to magmatic hydrothermal alteration.The enrichment of the studied samples in light rare earth elements(LREEs)relative to the heavy ones(HREEs)is attributed to most probably be due to the contamination of their mantle source with granitic source hydrothermal fluids after the obduction of the ophiolite assemblage onto the continental crust.The examined rocks represent mantle residue that experienced different degrees of partial melting(~10%to 25%for W.El-Nabárocks and~5%to 23%for W.Ghadir rocks).Variable degrees of partial melting among the two investigated areas suggest mantle heterogeneity beneath the Arabian-Nubian Shield(ANS).
基金funded by the Department of Science and Technology(DST),Government of Indiafunding support by the Science and Engineering Research Board(SERB),New Delhi(No.SR/FTP/ES-49/2012).
文摘In recent years,explosion of research in the early Tertiary mammals of India has attracted widespread interest because of the importance of this fauna in understanding biogeographic origins,early evolution,and dispersal patterns of several modern mammal orders as well for its paleogeographic implications.Although Paleocene mammals are yet to be discovered in the Indian subcontinent,Indian Early Eocene mammal faunas are now becoming increasingly important in debates concerning the origins of several modern terrestrial orders.
文摘The distribution of Eocene-Oligocene turbidite facies in the Pindos foreland and the paleocurrent directions of submarine fan deposits,of the Peloponnesus area,document the proximal part of an underfilled foreland basin.The definition of Pindos foreland basin attributes sediment accommodation solely to flexural subsidence driven by topographic load of the thrust belt and sediment loads in the foreland basin.The restriction of the coarse grained deposits and the basin underfilled conditions are related to the Pindos foreland evolution,and especially to the internal thrusting and produced intrabasinal highs.The presence of strike-slip faults can affect the geometry of a basin by causing changes in depth and width,resulting in the transformation from a uniform to non-uniform configuration.This change has an intensive impact on depositional environments along the basin axis.Strike-slip faults that cross-cut intrabasinal highs produce pathways for the sediment distribution on both sides of the highs.Distributary channels that discharge into the basin are perpendicular to its axis and shift axially at the basin floor.The strikeslip and thrust faulting operated contemporaneously for much of their active periods,although it appears that thrust faulting,initiated slightly earlier than strike-slip faulting.
文摘This workshop and pre-workshop fieldtrip were organized by the Institute ofGeology and Mineralogy,Siberian Branch,Russian Academy of Sciences(SB RAS)andco-sponsored by the Presidium of the SiberianBranch of the Russian Academy of Science(SB RAS),Centre for Russian and CentralEurAsian Mineral Studies(CERCAMS),andTask Force 1(ERAS)of the InternationalLithosphere Program(ILP).This waspreceded by a field excursion to Gorny Altayin Southwestern Siberia(June 20-28,2010),which,in the literature,is also referred to asMountainous Altay or Russian Altay.Thefield excursion and the workshop attractedeighteen participants from 8 countries,namely Germany,England,Japan,China,France,Czech Republic,Poland and Russia.The main goal of this workshop was todiscuss the general evolution of the CentralAsian Orogenic Belt(CAOB)with a specialemphasis to the problems of continentalgrowth,evolution of palaeo-oceans and activecontinental margins,collisional tectonicsand metallogeny based on results of previousfield missions and analytical research.Thiswould contribute to our understanding of the Late Neoproterozoic to Palaeozoic evolutionof the Altay belt and to establish up-to-datemodels of ocean closure,continentalaccretion/assembly and intracontinentalorogeny.
文摘Introduction Geology of the Indian subcontinent is not only diverse and interesting but also has been studied for a long period.Reflection of a rich geoscientific heritage may be illustrated by a couple of lesser known early or first“discoveries/descriptions”from the Indian subcontinent.Heinrich(1966)in his book“The Geology of Carbonatites”mentions that the first description of carbonatite was provided from India by Bose(1884)as quoted below(italics and bold for emphasis).
文摘The Proterozoic metasedimentary rocks of the Yaounde Group on the northern edge of the Congo Shield in Central Africa were investigated to understand their provenance and depositional environment.Petrography,geochemistry,and field evidence helped to subdivide the metasediments into paragneiss,mica schist,chlorite schist,and quartzite which were derived from greywacke,shale,quartz arenite,litharenite protoliths.They are immature with some mature samples,moderately weathered and reworked Neo-and Post-Archean metasediments.Rare earth element signatures(Chondrite Eu/Eu^(*)≤1),enrichment of light rare earth elements over the heavy ones,and the La/Sc ratio(>0.7)are compatible with those of the intermediate and felsic sources from the upper continental crust.These metasediments were deposited in the continental arc setting and have evolved during Proterozoic times according to the Wilson cycle to form the West Gondwana including NE Brazil.
文摘The Tan-Lu fault zone(TLFZ)along the East China continental margin experienced sinistral movement at the beginning of Early Cretaceous(ca.145)due to fast oblique subduction of the Izanagi Plate in the Pacific Ocean.It can
文摘This paper summarizes recent data about magnesite and talc genesis in Carboniferous host rocks of Western Carpathians (Slovakia) , which occur in two distinct belts in tectonic superunit Veporicum and its contact zone with Gemericum. The northern Sinec magnesite and talc belt (with main deposits Kokava, Sinec, Samo, Hnust'a-Mutnik) contains economic accummulation of magnesite and talc, while in the southern Ochtina belt ( main deposits in Dubrava massif-Dubrava, Mikova, Jedl'ovec; Lubenik, Ochtina, Kosice-Bankov, Banisko, Medvedia) the magnesite is dominating.The magnesite genesis by successive replacement of Carboniferous calcite to dolomite and magnesite during metamorphic process Ml (northern belt 280-400℃; , southern belt 370-420℃: ; Radvanec & Prochaska, 2001; Kodera & Radvanec, 2002) , being supplied by Mg from Permoscythian evaporitic bittern brines, relates to Variscan post-collisional (post-VD) evolution. The extensional tectonics and the high heat flow facilitated the generation of a hydrothermal system.The time-separated later metamorphic and sourcely different fluid flow event (M2; 1. c. ) produced talc. Tectonic, microtectonic, metamorphic and geochronological data relate the talc origin with the Alpine Upper Cretaceous (88-84 Ma; Maluski in Kovacik et al. , 1996) tectonothermal event AD2. This event, being the consequence of Alpine collisional ( AD1 ) crustal thickening and metamorphic core complex origin, meant regional extension and pervasive fluid flow of open system in crustal discontinuities. This process was prominent in the northern belt ( Sinec shear zone) located more closely to Veporic thermal dome, while towards its peripheral parts (southern Ochtina belt) the M2 metamorphic process and steatitization gradually weakened.Studies from Sinec shear zone (being the prominent AD2 -AD3 structure of northern Sinec belt) , where the dolomite/magnesite lenses (replacement in M1) and their accompanying lithology were in AD1 sandwitched between more competent basement blocks, proved in AD2 the pervasite steatitization, the talc and dolomite 2 origin in extensional microstructures ( metamorphic process M2; 490 -540℃, 240-330 MPa, 1. c. ).The economic accummulations of talc in Sinec belt are the products of antithetic shearing during the AD3 phase, being the gradual continuation of AD2 ( change of kinematics from unroofing to regional transpressional shearing). Contrary to the northern Sinec belt having located the AD3 deformation into narrow shear zone with soft lithology surrounded by hard lithology, in southern Ochtina belt the deformation AD3 was accommodated by wide soft rock column with rigid carbonate blocks floating inside. The lower P-T ( M2)conditions and deformational gradient in Ochtina belt during AD2 and AD3 phases caused why no economic talc accummulations developed there.The results of presented study can be used as general criteria for magnesite and talc prospection in Alpine type terranes.
基金The support of the National Science Foundation of China （grant No. 40132010, No. 40634022, No. 40221301, No. 40572118） is gratefully acknowledged.
文摘The Late Triassic to Paleogene （T3-E） basin occupies an area of 143100 km^2, being the sixth area of the whole of SE China; the total area of synchronous granitoid is about 127300 km^2; it provides a key for understanding the tectonic evolution of South China. From a new 1：1500000 geological map of the Mesozoic-Cenozoic basins of SE China, combined with analysis of geometrical and petrological features, some new insights of basin tectonics are obtained. Advances include petrotectonic assemblages, basin classification of geodynamics, geometric features, relations of basin and range. According to basin-forming geodynamical mechanisms, the Mesozoic-Cenozoic basin of SE China can be divided into three types, namely： 1） para-foreland basin formed from Late Triassic to Early Jurassic （T3-J1） under compressional conditions; 2） rift basins formed during the Middle Jurassic （J2） under a strongly extensional setting; and 3） a faulted depression formed during Early Cretaceous to Paleogene （K1-E） under back-arc extension action. From the rock assemblages of the basin, the faulted depression can be subdivided into a volcanic-sedimentary type formed mainly during the Early Cretaceous （K1） and a red -bed type formed from Late Cretaceous to Paleogene （K2-E）. Statistical data suggest that the area of all para-foreland basins （T3-J1） is 15120 km^2, one of rift basins （J2） occupies 4640 km^2, and all faulted depressions equal to 124330 km^2 including the K2-E red-bed basins of 37850 km^2. The Early Mesozoic （T3-J1） basin and granite were mostly co-generated under a post-collision compression background, while the basins from Middle Jurassic to Paleogene （J2-E） were mainly constrained by regional extensional tectonics. Three geological and geographical zones were surveyed, namely： 1） the Wuyishan separating zone of paleogeography and climate from Middle Jurassic to Tertiary; 2） the Middle Jurassic rift zone; and 3） the Ganjiang separating zone of Late Mesozoic volcanism. Three types of basin-granite relationships have been identified, including compressional （a few）, strike-slip （a few）, and extensional （common）. A three-stage geodynamical evolution of the SE-China basin is mooted： an Early Mesozoic basin-granite framework; a transitional Middle Jurassic tectonic regime; intracontinental extension and red-bed faulted depressions since the Late Cretaceous.
文摘Early Palaeozoic Cambrian A-type Kathalguri Granites in the Mikir Hills of northeastern (NE) India were studied to better understand the geodynamic settings in this region. This research presents new whole-rock geochemical and Sr, Nd, Pb isotopic data for the Cambrian granites in the Kathalguri Granite in Mikir Hills. The Kathalguri Granite shows geochemical characteristics of high SiO2, K2O and low FeOT, MgO, CaO, and P2O5 compositions. They belong to a high K Shoshonite to ultra-potassic series and display a weak metaluminous to peraluminous feature with A/CNK values of 0.83 to 1.02 with corundum and anorthite normative. FeOT/MgO varies from 2.93 - 7.49, is moderately oxidized and belongs to magnetite series. The rocks have a high ΣREE composition of 370.80 - 1353.23 ppm (average 568.55) and are enriched in LREE with flat HREE and (La/Yb)N values of 8.10 - 18.99, and display obvious strong negative Eu anomalies. Trace elements of the studied granites are characterized by enrichment in Rb, Th, U, Pb, Hf, and Sm, and depletion of Ba, Nb, Ta, and Sr. They display geochemical features of high Zr + Y + Nb + Ce values (241 - 934 ppm) and Ga/Al ratios 2.49 - 3.01 consistent with A-Type granites. Based on particular geochemical features, such as high Rb/Nb (3.10 - 19.53) and Low Y/Nb (0.09 - 2.28), Kathalguri Granite can be further classified as an A1-type subgroup. Granites display relatively low Sr (N ratio varying between 0.53 - 0.89 suggesting that the melts generated at greater depths (18 - 40 km), and fractionation at low pressures (−3 and total HGU 98.96 to 214.20. Kathalguri Granite dated by Rb-Sr isotopic isochrone as 489 ± 19 Ma with an initial 87Sr/86Sr 0.7199 ± 0.0017 and MSWD of 4.1, εSr(I) varied between 161.62 - 332.08 suggests that the Kathalguri Granite have originated from partial melting of ancient, evolved continental crustal material. The Sm-Nd Systematics has given a depleted mantle model (TDM) age ranging from 1733 - 2063 Ma with high negative εNd(t) values (−10.39 to −15.18) also hint at some heterogeneity or multiple source contributions in the melting process of the protolith. Xenoliths of older mafic rocks and Barapani arenites are seen within the Kathalguri Granite and are also supported by geochemical signatures of recycled crustal materials both mafic and sedimentary. It formed during the Cambrian reorganization of lithospheric plate motion related to the Pan-African-Braziliano event.
文摘Prof.M.Jayananda has been elected as a Fellow of Indian Academy of Sciences in recognition of his research contributions on the Archean magmatism,continental growth and geodynamic evolution of Dharwar craton,southern India.For the past 30 years he has carried out multidisciplinary research involving field based strain fabric analysis,elemental and isotope tracers.His research has significant impact on understanding the geological and tectonic evolution early earth into a habitable planet.
基金funded by the National Basic Research Program of China(973 Program,No.2012CB416701)National Natural Science Foundation of China(Grant 40972132)was partly supported by the State Key Laboratory for Mineral Deposits Research of Nanjing University(No.2008-Ⅰ-01)
文摘During the Late Mesozoic Middle Jurassic--Late Cretaceous, basin and range tectonics and associated magmatism representative of an extensional tectonic setting was widespread in southeastern China as a result of Pacific Plate subduction. Basin tectonics consists of post-orogenic （Type I） and intra-continental extensional basins （Type II）. Type I basins developed in the piedmont and intraland during the Late Triassic to Early Jurassic, in which coarse-grained terrestrial clastic sediments were deposited. Type II basins formed during intra-continental crustal thinning and were characterized by the development of grabens and half-grabens. Graben basins were mainly generated during the Middle Jurassic and were associated with bimodal volcanism. Sediments in half-grabens are intercalated with rhyolitic tufts and lavas and are Early Cretaceous in age with a dominance of Late Cretaceous-Paleogene red beds. Ranges are composed of granitoids and bimodal volcanic rocks, A-type granites and dome-type metamorphic core complexes. The authors analyzed lithological, geochemical and geochronological features of the Late Mesozoic igneous rock assemblages and proposed some geodynamical constraints on forming the basin and range tectonics of South China. A comparison of the similarities and differences of basin and range tectonics between the eastern and western shores of the Pacific is made, and the geo- dynamical evolution model of the Southeast China Block during Late Mesozoic is discussed. Studied results suggest that the basin and range terrane within South China developed on a pre-Mesozoic folded belt was derived from a polyphase tectonic evolution mainly constrained by subduction of the western Pacific Plate since the Late Mesozoic, leading to formation of various magmatism in a back-arc exten- sional setting. Its geodynamic mechanism can compare with that of basin and range tectonics in the eastern shore of the Pacific. Differences of basin and range tectonics between both shores of the Pacific, such as mantle plume formation, scales of extensional and igneous rock assemblages and the age of basin and range tectonics, were caused mainly by the Yellowstone mantle plume in the eastern shore of the Pacific.
基金support of MoES funded project[‘Age Constraints on metamorphic evolution of the Trans-Himalayas’:‘MoES/P.O.(Geol/101(b)/2017)’]financial support under the INSA Honorary Scientist Program at the CSIR-Central Building research Institute,Roorkee.
文摘Regional metamorphic rocks preserve records of geodynamic evolution of orogenic belts.The Himalaya represents an evolving mountain belt with a complex geological history and is considered here as a composite of Trans–Himalaya and the Himalaya per se and the intervening Indus–Tsangpo Suture Zone.Each of these three tectonic domains is evaluated in the context of their metamorphic evolution.An episodic evolution is inferred and described.
文摘Authored by earnestly active and deeply perceptive earth scientists who had their ears to the ground and eyes roving the panorama of landscape,the 42 papers encompassing this tome speak volume of the range of subjects,the nature of the works and the depth of analyses attempted.There is no gainsaying that together these learned papers by those who worked with the rocks,some were among the rocks all their lives,present a coherent and comprehensive narratives of the geodynamic evolution of the Indian subcontinent—a collage of multiple geological provinces such as Proterozoic and Tertiary mobile belts,the Indian Shield riven with graben-forming faults that break the Shield into a number of cratons,the continental margin framing the subcontinent all around,the lava plateau that is now dissected by faults,the Tertiary foreland basin and its sedimentary plains,and the Andaman-Nicobar Island Arc.Also discussed is a chunk of Antarctica.
