The question of Tigranes II's coinage and its chronology is one of the main difficulties for Artaxiad numismatics.These coins account for over half of all coin types issued by all the kings of this dynasty over a ...The question of Tigranes II's coinage and its chronology is one of the main difficulties for Artaxiad numismatics.These coins account for over half of all coin types issued by all the kings of this dynasty over a period of almost two centuries(189 BC-AD 16).The abundance and wide range of types,monograms,legends,and tiara shapes have led to differing and sometimes contradictory classifications.展开更多
Based on the Rb-Sr isochron dating results, this paper suggests that the alkaline intrusive belt at the east foot of the Taihang-Da Hinggan Mountains were formed between 135 and 122 Ma. And the alkaline intrusives in ...Based on the Rb-Sr isochron dating results, this paper suggests that the alkaline intrusive belt at the east foot of the Taihang-Da Hinggan Mountains were formed between 135 and 122 Ma. And the alkaline intrusives in the north and south sections of this belt have entirely different Sr, Nd and Pb isotopic characteristics, i.e., all the rocks in the south section have positive εSr(t) and negative εNd(t) values and all those in the north have the opposite values. On the εSr(t) versus εNd(t) correlation diagram, the samples from the south are concentrated along the enriched mantle evolution trend lines and nearby, while those from the north fall along the depleted mantle trend lines and nearby. On the Pb isotope composition diagram, most of the samples from the south section fall on the mantle Pb evolution line and nearby, while those from the north lie between the Pb evolution lines of the mantle and the erogenic belt. The above-stated isotopic characteristics not only indicate that the source rocks展开更多
The Neoproterozoic Jiangnan orogen plays an important role in the study of the Precambrian tectonic evolution of South China. The tectonic nature of the Neoproterozoic sedimentary basins is still controversial, due to...The Neoproterozoic Jiangnan orogen plays an important role in the study of the Precambrian tectonic evolution of South China. The tectonic nature of the Neoproterozoic sedimentary basins is still controversial, due to poor understanding of the sedimentary sequences and the lack of geochronological data. Here, we present sedimentological, provenance and geochronological data from the Heshangzhen Group in the eastern Jiangnan orogen. Sedimentological analysis shows that the Luojiamen Formation was deposited in a submarine fan, and the overlying Hongchicun Formation was deposited in front of a fan delta. The youngest detrital zircons constrain the lower Luojiamen and Hongchicun formations with ages of 827.3 ± 8.4 Ma and 825 ± 12 Ma, respectively. The sandstones of the Luojiamen Formation are characterized by a large number of intermediate to felsic volcanic grains, suggesting a volcanic arc source. In contrast, quartz and sedimentary lithic grains increase in the Hongchicun Formation, showing a new input from a collisional orogenic source. Detrital zircon from six sandstone samples in the Luojiamen and Hongchicun formations yield similar age spectra of 930–820 Ma with a peak at ca. 845–860 Ma, with one main cluster at 930–820 Ma. Detrital zircons of 930–845 Ma show a positive value of εHf(t)(+2.4 to +11, mean +7.6), which is similar to the volcanic arc of the nearby Shuangxiwu Group. There are a minor group of zircons with U-Pb ages ranging from 820 Ma to 845 Ma from the middle part of the Luojiamen Formation and Hongchicun Formation, with εHf(t) values between-20 to +2.4, which are consistent with the characteristics of the Shuangqiaoshan Group. within light of the bidirectional paleocurrents in the Luojiamen Formation, it is speculated that the zircons of 820–845 Ma were recycled from the Shuangqiaoshan Group, which is derived from a continental arc to the northwest. Our data suggests that the Luojiamen Formation was formed in an inter-arc basin, while the Hongchicun Formation was formed in an accretionary wedge-top basin. When juxtaposed with the conglomeratic characteristics at the bottom of the Luojiamen Formation, it is believed that the unconformity represented by the ‘Shen Gong Movement' reflects the rapid erosion and accumulation process of island arc volcanic material. The disconformity between the Luojiamen and Hongchicun formations is the imprint of transition from inter-arc basin to accretionary wedge-top basin,which represents the collision between the Shuangxiwu arc and the Yangtze Plate.展开更多
A tree-ring width chronology of 442 years(1567-2008) was developed from Tibetan junipers(S.tibetica) derived from south Tibet in western China.Three versions of chronology were produced according to standard dendrochr...A tree-ring width chronology of 442 years(1567-2008) was developed from Tibetan junipers(S.tibetica) derived from south Tibet in western China.Three versions of chronology were produced according to standard dendrochronological techniques.The correlation and response analysis displays a high correlation between the standard tree ring-width chronology and observed annual mean precipitation series during the period 1961-2008.Based on a linear regression model,an annual(prior August to current July) precipitation for the past 229 years was reconstructed.This is the first well-calibrated precipitation reconstruction for the Nanggarze region,south Tibet.The results show that relatively wet years with above-average precipitation occurred in 1780-1807,1854-1866,1886-1898,1904-1949,1967-1981 and 2000-2008,whereas relatively dry years with below-average precipitation prevailed during 1808-1853,1867-1885,1899-1903,1950-1966 and 1982-1999.Common dry/wet periods during 1890s,1910s,1940s-1960s and 1980s were also identified from other moisture reconstructions of nearby regions,indicating a synchronous climatic variation in south Tibet.Abrupt change beginning in 1888 was detected,revealing a transition from wet to dry conditions in south Tibet.Power spectrum analysis reveals significant cycles of 28-year,5.5-5.6-year and 3.3-year during the past 200 years.展开更多
The timing of Palaeolithic human activities in South China is still controversial because of the lack of a reliable chronology of archaeological sites.The Longdengshan Palaeolithic site(LPS),located close to the Wuyi ...The timing of Palaeolithic human activities in South China is still controversial because of the lack of a reliable chronology of archaeological sites.The Longdengshan Palaeolithic site(LPS),located close to the Wuyi Mountain of South China,represents the first discovered and scientifically excavated Middle Palaeolithic site in the Fujian Province.This site is of considerable significance for studying the diffusion and cultural connotation of early Homo sapiens in southern China.In this study,we present optically stimulated luminescence(OSL)ages obtained from medium-grained quartz collected at the LPS.The single-aliquot regenerative-dose measurements of red soil deposits collected at the same site yielded internally and stratigraphically consistent ages and similar errors,indicating a potential ability of the technique,and also reflecting the influence of various sedimentary facies on the test results.Our results indicate that the 38–63µm quartz grains were generally partially-bleached and had large values of over-dispersion in the palaeo-reticulated laterites of west Fujian.Some samples yielded unsatisfactory results,suggesting that the degree of bleaching of diluvial and alluvial deposits should be properly assessed before dating.We did not detect any enrichment/depletion of U,Th and radioactive disequilibrium.The effect of chemical weathering on the dose rate estimation was negligible.Therefore,we used a central age model and the maximum age model to calculate the age of two samples,respectively,and the minimum age model to calculate the ages of the rest of the samples.The OSL ages of the samples ranged from 27.09±2.30 ka to 54.65±7.39 ka for the 38–63µm quartz size fraction,and roughly corresponded to the Marine Isotope Stage 3.In addition,three ages out of five are based on the calculation of minimum ages in this research,which needs to be further verified by other dating methods.展开更多
1 Introduction Hetai district,which is a mountainous area,situated on Guangning and Zhaoqing city,west Guangdong Province.Hetai district is generally located on southwest of South China Caledonian fold belt,east margi...1 Introduction Hetai district,which is a mountainous area,situated on Guangning and Zhaoqing city,west Guangdong Province.Hetai district is generally located on southwest of South China Caledonian fold belt,east margin of Yunkai post-Caledonian uplift.Multiple type granites are widely distributed in Hetai district,including Caledonian,Indosinian and Yanshanian granites.Based on展开更多
Geology setting and petrological features Qiangtang composite plate is located between Xijinwulan—Jinshajiang and Bangonghu—Nujiang suture zones, with the total area of several ten thousand square kilometers. The ex...Geology setting and petrological features Qiangtang composite plate is located between Xijinwulan—Jinshajiang and Bangonghu—Nujiang suture zones, with the total area of several ten thousand square kilometers. The exposed rocks are mainly Paleozoic, Mesozoic marine sedimentary rocks.. Around Zhabu—Shuanghu area, there exits a post late Triassic uplift, in which middle Devonian low\|intermediate degree metamorphic rocks with solid chronological evidence have been found. However, in central Qiangtang, debate is still there in several aspects, such as there is crystalline basement or not, basement features, and the pre\|Devonian evolution of Qiangtang plate, etc. (Cai Li et al.,1997)Duguer gneiss is the only proved gneiss in Qiangtang region upto now, which is exposed at Duguer mountain (peak, 6208m above sea level), Gaize county, and is confined by faults. An E—W oriented thrust fault zone is its south boundary, which is more than 200m wide and makes the gneiss overthrust on upper Carboniferous strata and Tertiary red beds southwardly. On the east and north sides of the gneiss are upper Carboniferous strata. The gneiss occurs as a triangle form with a long E—W trending bottom line (about 20km) and a height about 10km in S—N direction, which is the main part of Duguer Duguer mountain.Duguer gneiss consists of two rocks types, i.e. granitic gneiss (the dominant component) and amphibole\|plagioclase gneiss. The latter one occurs as a group of nearly E—W trending dikes with clear boundary, which are obviously late basic dikes that intruded into granite. Granitic gneiss is composed of porphyroclast granitic gneiss, banded granitic gneiss, gneissoid granite and granitic mylonite. Both granitic and amphibole\|plagioclase gneisses have been undergone same type and same degree metamorphism and deformation. The typical mineral assemblage of the former gneiss include quartz(30%), microcline(25%),plagioclase(30%), two mica (biotite +muscovite,13%) and the accessory minerals such as zircon, magnetite, and apatite etc. The main oxide contents of the granitic gneiss are (average of three samples) 73 53% SiO\-2, 12 9% Al\-2O\-3, 1 57% FeO, 0 52% MgO, 3 24%Na\-2O and 0 22% K\-2O. The REE distribution pattern shows typical features of granite, i.e. LREE enrichment, HREE depletion and rather strong negative Eu anomaly.展开更多
Objective The Altyn Tagh marks the northern margin of the Qinghai-Tibet Plateau and lies between the Tarim block to the north and the Qaidam block,Qilian Orogen,and Kunlun orogenic belt to the south.The Altyn Tagh reg...Objective The Altyn Tagh marks the northern margin of the Qinghai-Tibet Plateau and lies between the Tarim block to the north and the Qaidam block,Qilian Orogen,and Kunlun orogenic belt to the south.The Altyn Tagh region contains ophiolite,high-to ultrahigh-pressure metamorphic rocks,and igneous rocks.Previous research has virified the occurrence of continental rifting,subduction,slab roll-back,and collision between the Tarim block and Proto-Tethys oceanic plate.Moreover,Kaladaban volcanic rocks are mainly distributed in the north Altyn region.Studies of the magmatic evolution of this region have proposed that Altyn oceanic plate was subducted during the Ordovician(Han et al.,2012;Wang et al.,2017).However,the specific timing and other aspects of the subduction are debated,and an investigation of granite porphyry in the Kaladaban area would improve our understanding of this subduction event.In this study,we present new U-Pb zircon dating result and Sr-Nd isotope composition data for granite porphyry from the North Altyn region.The objective is to constrain the timing of subduction of the North Altyn oceanic plate and establish the petrogenesis and magma source of the granite porphyry.展开更多
Ⅰ. Goals
In connection with the history of science, the XiaShang-Zhou Chronology Project is one of the important projects of the National Key Science and Technology Research and Development Programme of the Ninth Fiv...Ⅰ. Goals
In connection with the history of science, the XiaShang-Zhou Chronology Project is one of the important projects of the National Key Science and Technology Research and Development Programme of the Ninth Five-Year Plan. It officially began in May 1996.After five years of effort by more than 200 scholars and experts from the Chinese Academy of Sciences,the Chinese Academy of Social Sciences, Peking University and other institutions, the project has attained its goal. The general goal of the project is to establish a chronological table for the three dynasties by means of combining the humanities and social sciences with the natural sciences. The concrete goals for different historical periods are:展开更多
October 1-7:The Potala Palace Repair Office organized Buddhist activities for the repair project in accor rdance with Buddhist tradition and Tibetan customs.Close to 60 lamas from various major monaster-ies recited Ga...October 1-7:The Potala Palace Repair Office organized Buddhist activities for the repair project in accor rdance with Buddhist tradition and Tibetan customs.Close to 60 lamas from various major monaster-ies recited Gangyur in the Potala Palace.On October 6,the people's govemment of the Tibet Autonom-ous Region issued the Notice on the Repair of the Potala Palace.展开更多
Twenty-nine isotopic ages, ranging from 41 to 27 Ma, are presented for the alkali-rich intrusive rocks and their coexisting alkaline volcanic rocks, lamprophyres and acidic porphyries, indicating that they are Tertiar...Twenty-nine isotopic ages, ranging from 41 to 27 Ma, are presented for the alkali-rich intrusive rocks and their coexisting alkaline volcanic rocks, lamprophyres and acidic porphyries, indicating that they are Tertiary in age. The alkali-rich intrusive rocks have 143Nd/144Nd ratios from 0. 512 415 to 0. 512 544, and 87Sr/86Sr ratios from 0.705 4 to 0.706 8, suggesting that their material originates from an enriched mantle source.展开更多
The present paper reports the research development in the timing and tectonic setting of the Xixiang Group, northwestern margin of the Yangtze block. U-Pb concordant ages of (946+-18) Ma and (904+-18) Ma of zircons we...The present paper reports the research development in the timing and tectonic setting of the Xixiang Group, northwestern margin of the Yangtze block. U-Pb concordant ages of (946+-18) Ma and (904+-18) Ma of zircons were obtained from the upper and lower units of the Xixiang volcanic succession, respectively. Elemental and Nd isotope characteristics show that the volcanic suite has the affinities of arc island magmatism as well as an evolution trend of tectonic setting from front-arc to back-arc. The volcanic rocks suffered from some extensive post-stage tectonothermal events, resulting in the resetting of their Rb-Sr isotopic system.展开更多
There are five major geological events in Precambrian complex, Taihangshan region determined by researching into geology and isotopic chronology of the complex. Basaltic magma erupted and quartz-dioritic to tonalitic ...There are five major geological events in Precambrian complex, Taihangshan region determined by researching into geology and isotopic chronology of the complex. Basaltic magma erupted and quartz-dioritic to tonalitic magma intruded in earlier neo-Archaean, which formed horn-blende-plagiogneiss of Fuping gneiss complex and metamorphic mafic rock enclaves in TTG gneiss complex. Granulite fades metamorphism and emplacement of biotite-plagiogneiss occurred in late neo-Archaean. Extension and uplifting from the end of neo-Archaean to Paleoproterozoic era formed Chengnanzhuang large extensional deformation zones and metamorphic mafic veins emplaced into the deformation zones. Remobilization of Precambrian complex and tectonic uplifting in late Paleoproterozoic era formed Longquanguan ductile shear zone and emplacement of Nanying gneiss. Occurrence of regional granite pegmatite at the end of Paleoproterozoic era means the end of the Luliang movement.展开更多
This paper introduced briefly the research results on lichenometry of the Holoceneglacial fluctuations in the headwater of the Urumqi River, in the central TianshanMountains and discussed the histories of the Holocene...This paper introduced briefly the research results on lichenometry of the Holoceneglacial fluctuations in the headwater of the Urumqi River, in the central TianshanMountains and discussed the histories of the Holocene glaciers and the climate. It isconsidered that lichenometry is one applicable method for dating the mid- and late-Holocene deposits in the cold and mountainous regions. Rhizocarpon geographicum (L.)DCand Xanthoria elegans (Link.) Th. Fr. could be used for dating the deposits of about 4500and 500 a B.P. respectively. There existed at least four periods of glacial advances whichoccurred before about 5700, 4100, 2800 and 403- 74 a B. P. respectively with the firstperiod the longest. Little Ice Age includes three stages of glacial advances which endedbefore about 403, 208 and 74 a B. P. respectively with the second stage the maximum.During the general Holocene warming processes, there existed at least four cold peri-ods which ended before about 5700, 4100, 2800 and 420- 91 a B.P. respectively,展开更多
Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5 ( 0.2 Ma. The tracing of elemental and Pb-Sr-Nd iso...Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5 ( 0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5 ( 0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. Et al., implying that they were formed in the same tectonic setting.展开更多
Chronology is the basis for using lacustrine sediments to reconstruct the history of en-vironmental change. Radioactive-nuclides such as 14C, 210Pb and 137Cs dating are mainly used to establish the chronology for rece...Chronology is the basis for using lacustrine sediments to reconstruct the history of en-vironmental change. Radioactive-nuclides such as 14C, 210Pb and 137Cs dating are mainly used to establish the chronology for recent several ten thousand years. Because of being mixed with “dead carbon”, the measured 14C age is always older than the actual age which is recognized as “reservoir effect”. Cs is a kind of active metal element, and easy to migrate vertically in the sediment that leads to the error of the time marker. 210Pb dating should make sure to select CIC model or CRS model. On the Tibetan Plateau, most of the lakes are alkaline closed lake where Cs is more moveable in the sediment and the reservoir effect caused by “dead carbon” on 14C dating is stronger. Based on the analysis on results of 14C, 210Pb and 137Cs of the lacustrine sediments from Co Ngoin, central Tibetan Plateau, we use the simple regression method to re-calculate the 14C calendar ages, and establish the time sequence for cores CE-1 and CE-2 with result of 210Pb CRS model for the upper 35 cm and re-calculated 14C calendar age for sediments bellow 35 cm. Since 1400 cal. a BP, sedimentation inter-rupted for more than 1000 years. According to this time sequence, variations of environmental proxies confidently reflect the major climatic events in Holocene.展开更多
The gneissic metagranites with Neoproterozoic protolith ages are widely exposed along the eastern margin of the Dabie ultra-high-pressure(UHP) metamorphic belt.In this paper,five representative plutons,including Huang...The gneissic metagranites with Neoproterozoic protolith ages are widely exposed along the eastern margin of the Dabie ultra-high-pressure(UHP) metamorphic belt.In this paper,five representative plutons,including Huangzhen,Daba,Shima,Shuanghe,and Sanzusi,were selected for a detailed chronological and geochemical study aiming to identify the nature of the protoliths and to reveal their implications for the Neoproterozoic tectono-magmatic evolution along the northeastern margin of the Yangtze Block.These gneissic metagranites consist mainly of quartz,albite(oligoclase) and K-feldspar,and minor amphibole and biotite,as well as some metamorphic minerals due to the UHP metamorphism,such as phengite,epidote and minor kyanite and garnet.Mafic alkaline minerals(e.g.,aegirine or aegirine-augite) have been observed in some of these plutons.Zircon LA-ICP-MS U-Pb dating results indicate that the protoliths of the gneissic metagranites have been generated in Mid-Neoproterozoic(770-780 Ma),and suffered both ultrahigh-pressure metamorphism in Early Mesozoic and subsequently high-pressure eclogite-facies recrystallization at about 215 Ma.Although the gneissic metagranites generally have high SiO2 contents(70.23%-77.23%) and show metaluminous-weakly peraluminous signatures(ASI=0.90-1.05),there are still some geochemical variances between different plutons.Compared with the Sanzusi pluton,the metagranites from the Huangzhen,Daba,Shima,and Shuanghe have high K2O+Na2O contents(7.76%-9.45%),FeOtotal/(FeOtotal+MgO) ratios(0.82-0.96),HFSEs and Ga concentrations with an average 104×Ga/Al ratio up to 3.07.Combined with the features that the four plutons commonly contain aegirine-augite and have high zircon saturation temperatures(816-918°C),it is suggested that their proto-liths belong to peralkaline A-type granites.The Sanzusi pluton generally contains biotite and epidote generated from metamorphic reaction of amphibole,and is chemically enriched in calcium and depleted in potassium with K2O/Na2O ratios ranging from 0.42 to 0.54,suggesting their protoliths should be ascribed to calc-alkaline granitoids(I-type).The gneissic metagranites in the eastern margin of Dabie Mountains show both arc-and rift-like geochemical signatures,and their protoliths likely have been generated by reworking of the preexisting arc-related crust under an extensional setting,suggesting that the northeastern margin of the Yangtze Block during the Middle Neoproterozoic likely have been under the initial stage of a passive rifting rather than in an active rifting setting typically induced by the upwelling of a mantle plume.展开更多
The reconstruction of high-resolution chronologies for prehistoric cultures is a prerequisite for understanding the history of human evolution and its relationship with environmental change, and is valuable for explor...The reconstruction of high-resolution chronologies for prehistoric cultures is a prerequisite for understanding the history of human evolution and its relationship with environmental change, and is valuable for exploring the trajectory of transcontinental cultural exchanges in prehistoric time. The Hexi Corridor of northwest China was one of the earliest centers for long-distance culture exchange in the prehistoric world. The timing and sequence of cultural changes in this area remains poorly understood resulting from the lack of radiometric age control. This paper presents a refined radiocarbon(14 C) chronology to resolve the timing of human occupation and cultural evolution in the Hexi Corridor. Radiocarbon dating of crop remains, which have an annual life cycle, has the advantage of eliminating problems such as the carbon stored in ‘old wood’. As a result,14C dates from crop remains are used to test the validity of the14C dates derived from charcoal, bone and plant remains. The resultant database of ages is modelled using the Bayesian approach. The updated chronology presented in this paper shows generally good agreement with the original dates used to constrain cultural evolution in the Hexi Corridor. However, the occupation of the corridor by the Shajing and Shanma Late Bronze Age-Early Iron Age cultures appears to have taken place ~300 years later than previously thought. On the basis of comparing this updated chronology of cultural evolution with palaeoclimatic and historical records, it is proposed that the collapse of the Shajing and Shanma cultures occurred as a result of geopolitical impact rather than climate change.展开更多
TREE-ring analysis is one of the important ways for paleoclimatic reconstruction because tree-ring series of several hundred or even thousands of years are available, and can be matched orextended and accurately dated...TREE-ring analysis is one of the important ways for paleoclimatic reconstruction because tree-ring series of several hundred or even thousands of years are available, and can be matched orextended and accurately dated, and the tree rings can record changes in climate. In China,several thousand paleoclimatic series of data are obtained from the historical documents,展开更多
文摘The question of Tigranes II's coinage and its chronology is one of the main difficulties for Artaxiad numismatics.These coins account for over half of all coin types issued by all the kings of this dynasty over a period of almost two centuries(189 BC-AD 16).The abundance and wide range of types,monograms,legends,and tiara shapes have led to differing and sometimes contradictory classifications.
文摘Based on the Rb-Sr isochron dating results, this paper suggests that the alkaline intrusive belt at the east foot of the Taihang-Da Hinggan Mountains were formed between 135 and 122 Ma. And the alkaline intrusives in the north and south sections of this belt have entirely different Sr, Nd and Pb isotopic characteristics, i.e., all the rocks in the south section have positive εSr(t) and negative εNd(t) values and all those in the north have the opposite values. On the εSr(t) versus εNd(t) correlation diagram, the samples from the south are concentrated along the enriched mantle evolution trend lines and nearby, while those from the north fall along the depleted mantle trend lines and nearby. On the Pb isotope composition diagram, most of the samples from the south section fall on the mantle Pb evolution line and nearby, while those from the north lie between the Pb evolution lines of the mantle and the erogenic belt. The above-stated isotopic characteristics not only indicate that the source rocks
基金supported by the Geological Survey Project of the Chinese Geological Survey(DD20190043,DD20160038)。
文摘The Neoproterozoic Jiangnan orogen plays an important role in the study of the Precambrian tectonic evolution of South China. The tectonic nature of the Neoproterozoic sedimentary basins is still controversial, due to poor understanding of the sedimentary sequences and the lack of geochronological data. Here, we present sedimentological, provenance and geochronological data from the Heshangzhen Group in the eastern Jiangnan orogen. Sedimentological analysis shows that the Luojiamen Formation was deposited in a submarine fan, and the overlying Hongchicun Formation was deposited in front of a fan delta. The youngest detrital zircons constrain the lower Luojiamen and Hongchicun formations with ages of 827.3 ± 8.4 Ma and 825 ± 12 Ma, respectively. The sandstones of the Luojiamen Formation are characterized by a large number of intermediate to felsic volcanic grains, suggesting a volcanic arc source. In contrast, quartz and sedimentary lithic grains increase in the Hongchicun Formation, showing a new input from a collisional orogenic source. Detrital zircon from six sandstone samples in the Luojiamen and Hongchicun formations yield similar age spectra of 930–820 Ma with a peak at ca. 845–860 Ma, with one main cluster at 930–820 Ma. Detrital zircons of 930–845 Ma show a positive value of εHf(t)(+2.4 to +11, mean +7.6), which is similar to the volcanic arc of the nearby Shuangxiwu Group. There are a minor group of zircons with U-Pb ages ranging from 820 Ma to 845 Ma from the middle part of the Luojiamen Formation and Hongchicun Formation, with εHf(t) values between-20 to +2.4, which are consistent with the characteristics of the Shuangqiaoshan Group. within light of the bidirectional paleocurrents in the Luojiamen Formation, it is speculated that the zircons of 820–845 Ma were recycled from the Shuangqiaoshan Group, which is derived from a continental arc to the northwest. Our data suggests that the Luojiamen Formation was formed in an inter-arc basin, while the Hongchicun Formation was formed in an accretionary wedge-top basin. When juxtaposed with the conglomeratic characteristics at the bottom of the Luojiamen Formation, it is believed that the unconformity represented by the ‘Shen Gong Movement' reflects the rapid erosion and accumulation process of island arc volcanic material. The disconformity between the Luojiamen and Hongchicun formations is the imprint of transition from inter-arc basin to accretionary wedge-top basin,which represents the collision between the Shuangxiwu arc and the Yangtze Plate.
基金funded by the National Basic Research Program of China (973 Program) (No.2010CB950104)the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists (Grant No.2009S1-38)+1 种基金the Chinese Academy of Sciences (CAS) 100 Talents Project (29082762)the NSFC (Grant no.40871091)
文摘A tree-ring width chronology of 442 years(1567-2008) was developed from Tibetan junipers(S.tibetica) derived from south Tibet in western China.Three versions of chronology were produced according to standard dendrochronological techniques.The correlation and response analysis displays a high correlation between the standard tree ring-width chronology and observed annual mean precipitation series during the period 1961-2008.Based on a linear regression model,an annual(prior August to current July) precipitation for the past 229 years was reconstructed.This is the first well-calibrated precipitation reconstruction for the Nanggarze region,south Tibet.The results show that relatively wet years with above-average precipitation occurred in 1780-1807,1854-1866,1886-1898,1904-1949,1967-1981 and 2000-2008,whereas relatively dry years with below-average precipitation prevailed during 1808-1853,1867-1885,1899-1903,1950-1966 and 1982-1999.Common dry/wet periods during 1890s,1910s,1940s-1960s and 1980s were also identified from other moisture reconstructions of nearby regions,indicating a synchronous climatic variation in south Tibet.Abrupt change beginning in 1888 was detected,revealing a transition from wet to dry conditions in south Tibet.Power spectrum analysis reveals significant cycles of 28-year,5.5-5.6-year and 3.3-year during the past 200 years.
基金supported by National Natural Science Foundation of China(Grant Nos.41301012,42077407 and 41771020),Natural Science Foundation of Fujian Province,China(Grant No.2020J01185),and the Innovation Research Team Fund of Fujian Normal University(Grant No.IRTL1705).
文摘The timing of Palaeolithic human activities in South China is still controversial because of the lack of a reliable chronology of archaeological sites.The Longdengshan Palaeolithic site(LPS),located close to the Wuyi Mountain of South China,represents the first discovered and scientifically excavated Middle Palaeolithic site in the Fujian Province.This site is of considerable significance for studying the diffusion and cultural connotation of early Homo sapiens in southern China.In this study,we present optically stimulated luminescence(OSL)ages obtained from medium-grained quartz collected at the LPS.The single-aliquot regenerative-dose measurements of red soil deposits collected at the same site yielded internally and stratigraphically consistent ages and similar errors,indicating a potential ability of the technique,and also reflecting the influence of various sedimentary facies on the test results.Our results indicate that the 38–63µm quartz grains were generally partially-bleached and had large values of over-dispersion in the palaeo-reticulated laterites of west Fujian.Some samples yielded unsatisfactory results,suggesting that the degree of bleaching of diluvial and alluvial deposits should be properly assessed before dating.We did not detect any enrichment/depletion of U,Th and radioactive disequilibrium.The effect of chemical weathering on the dose rate estimation was negligible.Therefore,we used a central age model and the maximum age model to calculate the age of two samples,respectively,and the minimum age model to calculate the ages of the rest of the samples.The OSL ages of the samples ranged from 27.09±2.30 ka to 54.65±7.39 ka for the 38–63µm quartz size fraction,and roughly corresponded to the Marine Isotope Stage 3.In addition,three ages out of five are based on the calculation of minimum ages in this research,which needs to be further verified by other dating methods.
基金co-funded by the China Geological Survey (No.12120114052801)the DREAM project of MOST, China (NO. 2016YFC0600401)
文摘1 Introduction Hetai district,which is a mountainous area,situated on Guangning and Zhaoqing city,west Guangdong Province.Hetai district is generally located on southwest of South China Caledonian fold belt,east margin of Yunkai post-Caledonian uplift.Multiple type granites are widely distributed in Hetai district,including Caledonian,Indosinian and Yanshanian granites.Based on
文摘Geology setting and petrological features Qiangtang composite plate is located between Xijinwulan—Jinshajiang and Bangonghu—Nujiang suture zones, with the total area of several ten thousand square kilometers. The exposed rocks are mainly Paleozoic, Mesozoic marine sedimentary rocks.. Around Zhabu—Shuanghu area, there exits a post late Triassic uplift, in which middle Devonian low\|intermediate degree metamorphic rocks with solid chronological evidence have been found. However, in central Qiangtang, debate is still there in several aspects, such as there is crystalline basement or not, basement features, and the pre\|Devonian evolution of Qiangtang plate, etc. (Cai Li et al.,1997)Duguer gneiss is the only proved gneiss in Qiangtang region upto now, which is exposed at Duguer mountain (peak, 6208m above sea level), Gaize county, and is confined by faults. An E—W oriented thrust fault zone is its south boundary, which is more than 200m wide and makes the gneiss overthrust on upper Carboniferous strata and Tertiary red beds southwardly. On the east and north sides of the gneiss are upper Carboniferous strata. The gneiss occurs as a triangle form with a long E—W trending bottom line (about 20km) and a height about 10km in S—N direction, which is the main part of Duguer Duguer mountain.Duguer gneiss consists of two rocks types, i.e. granitic gneiss (the dominant component) and amphibole\|plagioclase gneiss. The latter one occurs as a group of nearly E—W trending dikes with clear boundary, which are obviously late basic dikes that intruded into granite. Granitic gneiss is composed of porphyroclast granitic gneiss, banded granitic gneiss, gneissoid granite and granitic mylonite. Both granitic and amphibole\|plagioclase gneisses have been undergone same type and same degree metamorphism and deformation. The typical mineral assemblage of the former gneiss include quartz(30%), microcline(25%),plagioclase(30%), two mica (biotite +muscovite,13%) and the accessory minerals such as zircon, magnetite, and apatite etc. The main oxide contents of the granitic gneiss are (average of three samples) 73 53% SiO\-2, 12 9% Al\-2O\-3, 1 57% FeO, 0 52% MgO, 3 24%Na\-2O and 0 22% K\-2O. The REE distribution pattern shows typical features of granite, i.e. LREE enrichment, HREE depletion and rather strong negative Eu anomaly.
基金jointly supported by the National Key R&D Program of China(Grant No.2018YFC0603704)a Geological Survey Project of the China Geological Survey(DD20160050).
文摘Objective The Altyn Tagh marks the northern margin of the Qinghai-Tibet Plateau and lies between the Tarim block to the north and the Qaidam block,Qilian Orogen,and Kunlun orogenic belt to the south.The Altyn Tagh region contains ophiolite,high-to ultrahigh-pressure metamorphic rocks,and igneous rocks.Previous research has virified the occurrence of continental rifting,subduction,slab roll-back,and collision between the Tarim block and Proto-Tethys oceanic plate.Moreover,Kaladaban volcanic rocks are mainly distributed in the north Altyn region.Studies of the magmatic evolution of this region have proposed that Altyn oceanic plate was subducted during the Ordovician(Han et al.,2012;Wang et al.,2017).However,the specific timing and other aspects of the subduction are debated,and an investigation of granite porphyry in the Kaladaban area would improve our understanding of this subduction event.In this study,we present new U-Pb zircon dating result and Sr-Nd isotope composition data for granite porphyry from the North Altyn region.The objective is to constrain the timing of subduction of the North Altyn oceanic plate and establish the petrogenesis and magma source of the granite porphyry.
文摘Ⅰ. Goals
In connection with the history of science, the XiaShang-Zhou Chronology Project is one of the important projects of the National Key Science and Technology Research and Development Programme of the Ninth Five-Year Plan. It officially began in May 1996.After five years of effort by more than 200 scholars and experts from the Chinese Academy of Sciences,the Chinese Academy of Social Sciences, Peking University and other institutions, the project has attained its goal. The general goal of the project is to establish a chronological table for the three dynasties by means of combining the humanities and social sciences with the natural sciences. The concrete goals for different historical periods are:
文摘October 1-7:The Potala Palace Repair Office organized Buddhist activities for the repair project in accor rdance with Buddhist tradition and Tibetan customs.Close to 60 lamas from various major monaster-ies recited Gangyur in the Potala Palace.On October 6,the people's govemment of the Tibet Autonom-ous Region issued the Notice on the Repair of the Potala Palace.
基金Project supported by the National Natural Science Foundation of China and the Special Grant of the President of Chinese A.cademy of Sciences
文摘Twenty-nine isotopic ages, ranging from 41 to 27 Ma, are presented for the alkali-rich intrusive rocks and their coexisting alkaline volcanic rocks, lamprophyres and acidic porphyries, indicating that they are Tertiary in age. The alkali-rich intrusive rocks have 143Nd/144Nd ratios from 0. 512 415 to 0. 512 544, and 87Sr/86Sr ratios from 0.705 4 to 0.706 8, suggesting that their material originates from an enriched mantle source.
基金This work was supported by the NationalNatural Science Foundation of China (Grant Nos. 49873010, 49794043 and 49573138) the Ministry of National Land and Resources of China (Grant No. 20001010203).
文摘The present paper reports the research development in the timing and tectonic setting of the Xixiang Group, northwestern margin of the Yangtze block. U-Pb concordant ages of (946+-18) Ma and (904+-18) Ma of zircons were obtained from the upper and lower units of the Xixiang volcanic succession, respectively. Elemental and Nd isotope characteristics show that the volcanic suite has the affinities of arc island magmatism as well as an evolution trend of tectonic setting from front-arc to back-arc. The volcanic rocks suffered from some extensive post-stage tectonothermal events, resulting in the resetting of their Rb-Sr isotopic system.
文摘There are five major geological events in Precambrian complex, Taihangshan region determined by researching into geology and isotopic chronology of the complex. Basaltic magma erupted and quartz-dioritic to tonalitic magma intruded in earlier neo-Archaean, which formed horn-blende-plagiogneiss of Fuping gneiss complex and metamorphic mafic rock enclaves in TTG gneiss complex. Granulite fades metamorphism and emplacement of biotite-plagiogneiss occurred in late neo-Archaean. Extension and uplifting from the end of neo-Archaean to Paleoproterozoic era formed Chengnanzhuang large extensional deformation zones and metamorphic mafic veins emplaced into the deformation zones. Remobilization of Precambrian complex and tectonic uplifting in late Paleoproterozoic era formed Longquanguan ductile shear zone and emplacement of Nanying gneiss. Occurrence of regional granite pegmatite at the end of Paleoproterozoic era means the end of the Luliang movement.
文摘This paper introduced briefly the research results on lichenometry of the Holoceneglacial fluctuations in the headwater of the Urumqi River, in the central TianshanMountains and discussed the histories of the Holocene glaciers and the climate. It isconsidered that lichenometry is one applicable method for dating the mid- and late-Holocene deposits in the cold and mountainous regions. Rhizocarpon geographicum (L.)DCand Xanthoria elegans (Link.) Th. Fr. could be used for dating the deposits of about 4500and 500 a B.P. respectively. There existed at least four periods of glacial advances whichoccurred before about 5700, 4100, 2800 and 403- 74 a B. P. respectively with the firstperiod the longest. Little Ice Age includes three stages of glacial advances which endedbefore about 403, 208 and 74 a B. P. respectively with the second stage the maximum.During the general Holocene warming processes, there existed at least four cold peri-ods which ended before about 5700, 4100, 2800 and 420- 91 a B.P. respectively,
基金This work was jointly supported by the National Natural Science Foundation of China(Grant No.49972026)the Guangdong Natural Science Foundation(Grant No.990531)+1 种基金the project of the ChineseAcademy of Sciences(Grant No.KZCX2-SW-117)the Chinese National Key Project for Basic Research(Grant No.G1998040807)and US NSF.
文摘Our two newly obtained high-quality 40Ar/39Ar ages suggest that the high-K volcanic rocks of the Lawuxiang Formation in the Mangkang basin, Tibet were formed at 33.5 ( 0.2 Ma. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry indicates that they were derived from an EM2 enriched mantle in continental subduction caused by transpression. Their evidently negative anomalies in HFSEs such as Nb and Ta make clear that there is an input of continental material into the mantle source. The high-K rocks at 33.5 ( 0.2 Ma in the Mangkang basin may temporally, spatially and compositionally compare with the early one of two-pulse high-K rocks in eastern Tibet distinguished by Wang J. H. Et al., implying that they were formed in the same tectonic setting.
文摘Chronology is the basis for using lacustrine sediments to reconstruct the history of en-vironmental change. Radioactive-nuclides such as 14C, 210Pb and 137Cs dating are mainly used to establish the chronology for recent several ten thousand years. Because of being mixed with “dead carbon”, the measured 14C age is always older than the actual age which is recognized as “reservoir effect”. Cs is a kind of active metal element, and easy to migrate vertically in the sediment that leads to the error of the time marker. 210Pb dating should make sure to select CIC model or CRS model. On the Tibetan Plateau, most of the lakes are alkaline closed lake where Cs is more moveable in the sediment and the reservoir effect caused by “dead carbon” on 14C dating is stronger. Based on the analysis on results of 14C, 210Pb and 137Cs of the lacustrine sediments from Co Ngoin, central Tibetan Plateau, we use the simple regression method to re-calculate the 14C calendar ages, and establish the time sequence for cores CE-1 and CE-2 with result of 210Pb CRS model for the upper 35 cm and re-calculated 14C calendar age for sediments bellow 35 cm. Since 1400 cal. a BP, sedimentation inter-rupted for more than 1000 years. According to this time sequence, variations of environmental proxies confidently reflect the major climatic events in Holocene.
基金supported by National Natural Science Foundation of China (Grant No.40772036)the National Basic Research Program of China (Grant No.2006CB403508)
文摘The gneissic metagranites with Neoproterozoic protolith ages are widely exposed along the eastern margin of the Dabie ultra-high-pressure(UHP) metamorphic belt.In this paper,five representative plutons,including Huangzhen,Daba,Shima,Shuanghe,and Sanzusi,were selected for a detailed chronological and geochemical study aiming to identify the nature of the protoliths and to reveal their implications for the Neoproterozoic tectono-magmatic evolution along the northeastern margin of the Yangtze Block.These gneissic metagranites consist mainly of quartz,albite(oligoclase) and K-feldspar,and minor amphibole and biotite,as well as some metamorphic minerals due to the UHP metamorphism,such as phengite,epidote and minor kyanite and garnet.Mafic alkaline minerals(e.g.,aegirine or aegirine-augite) have been observed in some of these plutons.Zircon LA-ICP-MS U-Pb dating results indicate that the protoliths of the gneissic metagranites have been generated in Mid-Neoproterozoic(770-780 Ma),and suffered both ultrahigh-pressure metamorphism in Early Mesozoic and subsequently high-pressure eclogite-facies recrystallization at about 215 Ma.Although the gneissic metagranites generally have high SiO2 contents(70.23%-77.23%) and show metaluminous-weakly peraluminous signatures(ASI=0.90-1.05),there are still some geochemical variances between different plutons.Compared with the Sanzusi pluton,the metagranites from the Huangzhen,Daba,Shima,and Shuanghe have high K2O+Na2O contents(7.76%-9.45%),FeOtotal/(FeOtotal+MgO) ratios(0.82-0.96),HFSEs and Ga concentrations with an average 104×Ga/Al ratio up to 3.07.Combined with the features that the four plutons commonly contain aegirine-augite and have high zircon saturation temperatures(816-918°C),it is suggested that their proto-liths belong to peralkaline A-type granites.The Sanzusi pluton generally contains biotite and epidote generated from metamorphic reaction of amphibole,and is chemically enriched in calcium and depleted in potassium with K2O/Na2O ratios ranging from 0.42 to 0.54,suggesting their protoliths should be ascribed to calc-alkaline granitoids(I-type).The gneissic metagranites in the eastern margin of Dabie Mountains show both arc-and rift-like geochemical signatures,and their protoliths likely have been generated by reworking of the preexisting arc-related crust under an extensional setting,suggesting that the northeastern margin of the Yangtze Block during the Middle Neoproterozoic likely have been under the initial stage of a passive rifting rather than in an active rifting setting typically induced by the upwelling of a mantle plume.
基金supported by the National Key R&D Program of China(Grant No.2018YFA0606402)the Strategic Priority Research Program of the Chinese Academy of Sciences,Pan-Third Pole Environment Study for a Green Silk Road(Pan-TPE)(Grant No.XDA2004010101)the National Natural Science Foundation of China(Grant Nos.41825001&41620104007)
文摘The reconstruction of high-resolution chronologies for prehistoric cultures is a prerequisite for understanding the history of human evolution and its relationship with environmental change, and is valuable for exploring the trajectory of transcontinental cultural exchanges in prehistoric time. The Hexi Corridor of northwest China was one of the earliest centers for long-distance culture exchange in the prehistoric world. The timing and sequence of cultural changes in this area remains poorly understood resulting from the lack of radiometric age control. This paper presents a refined radiocarbon(14 C) chronology to resolve the timing of human occupation and cultural evolution in the Hexi Corridor. Radiocarbon dating of crop remains, which have an annual life cycle, has the advantage of eliminating problems such as the carbon stored in ‘old wood’. As a result,14C dates from crop remains are used to test the validity of the14C dates derived from charcoal, bone and plant remains. The resultant database of ages is modelled using the Bayesian approach. The updated chronology presented in this paper shows generally good agreement with the original dates used to constrain cultural evolution in the Hexi Corridor. However, the occupation of the corridor by the Shajing and Shanma Late Bronze Age-Early Iron Age cultures appears to have taken place ~300 years later than previously thought. On the basis of comparing this updated chronology of cultural evolution with palaeoclimatic and historical records, it is proposed that the collapse of the Shajing and Shanma cultures occurred as a result of geopolitical impact rather than climate change.
文摘TREE-ring analysis is one of the important ways for paleoclimatic reconstruction because tree-ring series of several hundred or even thousands of years are available, and can be matched orextended and accurately dated, and the tree rings can record changes in climate. In China,several thousand paleoclimatic series of data are obtained from the historical documents,
