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1.
SHRIMP U-Pb zircon ages for the UHP metamorphosed granitoid gneiss in Altyn Tagh and their geological significance 总被引:3,自引:0,他引:3
ZHANG Anda LIU Liang SUN Yong CHEN Danling WANG Yan & LUO Jinhai Key Laboratory of Continental Dynamics of the Ministry of Education Department of Geology Northwest University Xi’an China Correspondence should be addressed to Liu Liang 《科学通报(英文版)》2004,49(23):2527-2532
Different types of UHP metamorphic rocks havebeen recently discovered in the Altyn Tagh[1—4], the north-ern margin of Qadam Basin[5—7], the southwestern Tian-shan Mountains[8,9] and the northern Qinling Moun-tains[10,11] in Central and Western China. And these areashave attracted focus attention of geologists at home andabroad to the studying of UHP metamorphism and conti-nental deep subduction. However, as newly discoveredUHP metamorphic terranes, some questions have beenarisen abou… 相似文献
2.
Identification of 3.5 Ga detrital zircons from Yangtze craton in south China and the implication for Archean crust evolution 总被引:5,自引:0,他引:5
The LA-ICP-MS U-Pb dating of hundreds of detrital zircon grains from the Sinian sandstones of Liantuo formation and tillites of Nantuo formation at Sanxia area in Yichang identified 3319?3508 Ma zircon grains. Their 207Pb/206Pb and 206Pb/238U ages show excellent agreement (concordia degree 99%?100%). Their CL images exhibit well-developed oscillatory zoning and the Th/U ratios are within 0.46?0.76, implying that they are igneous zircons which formed during middle-early Archean. These zircons are the oldest ones discovered in Yangtze craton until now. However, the detrital zircons with ages older than 3.3 Ga in the metamorphic rocks of Kongling group were not found by further investigation, which suggests the presence of crust older than high-grade metamorphic Kongling terrain in Yangtze craton. 相似文献
3.
Simultaneous in-situ determination of U-Pb age and trace elements in zircon by LA-ICP-MS in 20 μm spot size 总被引:18,自引:0,他引:18
LIU XiaoMing GAO Shan DIWU ChunRong YUAN HongLin HU ZhaoChu 《科学通报(英文版)》2007,52(9):1257-1264
Simultaneous in-situ determination of U-Pb ages and 20 trace elements of three international zircon standards (91500, GJ1 and TEMORA 1) and one laboratory zircon standard (SK10-2) separated from Cenozoic fine-grained gabbro was carried out on quadrupole ICP-MS equipped with 193 nm excimer laser in 20 μm spot size. The weighted mean ^206Pb/^238U ages of 91500, GJ1 and TEMORA 1 are 1064.4±4.8 Ma (2σ), 603.2±2.4 Ma (2σ) and 418.2±2.4 Ma (2σ), respectively. The relative standard deviations (RSDs) of ^206Pb/^238U ages (2σ) are less than 2.2% for single measurements and 0.6% for weighted means. The obtained weighted mean ^206Pb/^238U ages of three standard zircons agree with the recommended values within 2σrerror. The weighted mean ^206Pb/^238U age of SK10-2 is 31.42=0.25 Ma (2σ) and the RSDs of ^206Pb/^238U ages (2σ) are between 2.4% and 5.7% for single measurements and less than 0.8% for weighted mean. The obtained weighted mean ^206Pb/^238U age is in good agreement with the age obtained by Yuan (2004). Trace element concentrations of NIST612 and NIST614 obtained under the same LA-ICP-MS operating conditions agree with the recommended values within analytical error. The results indicate that it is possible to measure U-Pb age and trace elements simultaneously by LA-ICP-MS in a small spot size of 20μm. 相似文献
4.
Chien-Yuan Tseng Houng-Yi Yang WAN Yusheng LIU Dunyi Da-Jen Wen Tzung-Chi Lin Kuo-An Tung 《科学通报(英文版)》2006,51(8):963-970
The Qilian Mountain is considered a part of the Cen- tral Orogenic Belt of China[1]. The Central Orogenic Belt of China, extending for a distance of about 4000 km long in the E-W direction from the east coast west- ward through the mainland China all the … 相似文献
5.
LA-ICP-MS zircon U-Pb dating for high-pressure basic granulite from North Qinling and its geological significance 总被引:11,自引:0,他引:11
CHEN Danling LIU Liang SUN Yong ZHANG Anda LIU Xiaoming & LUO Jinhai Key Laboratory of Continental Dynamics of the Ministry of Education Department of Geology Northwest University Xi’an China 《科学通报(英文版)》2004,49(21):2296-2304
Inrecentyears,discoveriesofhightoultrahighpressuremetamorphicrocksatthenorthandsouthsidesoftheQinlingGroupinthenorthernpartoftheQinlingMountains(hereafterNorthQinling)haveattractedfocusattentionofgeologistsworldwide.Thenorthhigh-pressure(HP)metamorphicbelt,distributedintheareafromGuanpotoShuanghuaishunorthwardtoShizipin,LushCountyinHenanProvince,consistsmainlyofeclogiteoutcroppedaslenticularmassesofdifferentsizesinthegneissesoftheQinlingGroupclosetothesouthsideofZhuyangguan-Xiaguanfault… 相似文献
6.
The U-Pb isotope compositions of rutile, omphacite and garnet in the eclogite from the Jinheqiao area in the Southern Dabie ultrahigh-pressure metamorphic zone were analyzed. The consistent high precision U-Pb age (218 ± 1.2) Ma of rutile in eclogite from the Dabie Mountains was obtained by two ways of isochron and common Pb correction based on the composition of omphacite. This proves that the omphacite in eclogite has a U/Pb ratio (m = 2.8) low enough to be used for common Pb correction in the analyses of rutile. Under the rapid cooling condition (40℃/Ma) the closure temperature for U-Pb diffusion in rutile is about 470℃. Thus, this U-Pb age of rutile proves that 218 Ma should be the cooling age of eclogite at 470℃ instead of the peak metamorphic age. 相似文献
7.
Garnet Sm-Nd and U-Pb systems: A case study of a granulite from the European Variscan belt 总被引:1,自引:0,他引:1
Fukun Chen 《科学通报(英文版)》2002,47(15):1284-1288
This study presents zircon and garnet ages of a mafic granulite from the high-grade Variscan basement of the Black Forest, Germany and discuss isotope closure temperature of garnet Sm-Nd and U-Pb systems. Zircon grains yield 207Pb/206Pb ages between ~340 and ~414 Ma by the U-Pb and evaporation methods. In contract, garnet dating gives Sm-Nd and Pb-Pb isochron ages of (398±3) Ma and (411±14) Ma, respectively, which are older than most of zircon ages. These data imply that most of zircons lost radiogenic Pb, probably due to metamictization or recrystallisation during the granulite-facies metamorphism (~800℃) at ~340 Ma. Garnet Sm-Nd and U-Pb systems preserve chronological information of pro-grade metamorphism, probably profiting from a fluid-absence metamorphic environment. These results demonstrate that garnet mineral can be a better candidate than zircon mineral to date high-grade metamorphism by the U-Pb and Sm-Nd methods in some cases. 相似文献
8.
WU YuanBao TANG Jun ZHANG ShaoBing ZHAO ZiFu 《科学通报(英文版)》2007,52(13):1836-1842
Zircon CL imaging and SHRIMP U-Pb dating were carried out for migmatite in the Dabie orogen. Zircons from the Manshuihe migmatite show clear core-rim structures. The cores display sector or weak zoning and low Th/U ratios of 0.01 to 0.17, indicating their precipitation from metamorphic fluid. They yield a weighted mean age of 137±5 Ma. By contrast, the rims exhibit planar or nebulous zoning with relatively high Th/U ratios of 0.35 to 0.69, suggesting their growth from metamorphic melt. They give a weighted mean age of 124±2 Ma. Zircons from the Fenghuangguan migmatite also display core-rim structures. The cores are weakly oscillatory zoned or unzoned with high Th/U ratios of 0.21 to 3.03, representing inherited zircons of magmatic origin that experienced different degrees of solid-state recrystallization. SHRIMP U-Pb analyses obtain that its protolith was emplaced at 768±12 Ma, consistent with middle Neoproterozoic ages for protoliths of most UHP metaigneous rocks in the Dabie-Sulu orogenic belt. By contrast, the rims do not show significant zoning and have very low Th/U ratios of 0.01 to 0.09, typical of zircon crystallized from metamorphic fluid. They yield a weighted 206Pb/238U age of 137±4 Ma. Taking the two case dates together, it appears that there are two episodes of zircon growth and thus migmati-tization at 137±2 Ma and 124±2 Ma, respectively, due to metamorphic dehydration and partial melting. The appearance of metamorphic dehydration corresponds to the beginning of tectonic extension thus to the tectonic switch from crustal compression to extension in the Dabie orogen. On the other hand, the partial melting is responsible for the extensional climax, resulting in formation of coeval migmatite, granitoid and granulite. They share the common protolith, the collision-thickened continental crust of mid-Neoproterozoic ages. 相似文献
9.
In situ U-Pb dating of xenotime by laser ablation (LA)-ICP-MS 总被引:1,自引:0,他引:1
Xenotime is an ideal mineral for U-Th-Pb isotopic dating because of its relatively high U and Th contents, but typically low concentration of common Pb. These characteristics, and the fact that it is widespread throughout various types of rocks, suggest that the U-Th-Pb dating of xenotime has broad applications. Studies of U-Pb dating on xenotime by ion microprobe (such as SHRIMP) have increased in recent years, whereas studies by laser ablation (LA)-ICP-MS are still rare. In this study, we developed a technique for U-Pb dating of xenotime using the 193 nm ArF laser-ablation system and Agilent 7500a Q-ICP-MS. To evaluate the reliability of our method, a xenotime standard, BS-1, was analyzed and calibrated against another xenotime standard, MG-1. The weighted mean 206 Pb/ 238 U ages of 510.1 ± 5.2 Ma (2 n = 21), 509.8 ± 4.3 Ma (2 n = 21) and 510.0 ± 4.6 Ma (2 n = 21) were obtained using beam diameters of 16, 24 and 32 m, respectively. These ages are identical to those determined by ID-TIMS method (weighted mean 206 Pb/ 238 U age of 508.8 ± 1.4 Ma), which supports the reliability of our LA-ICP-MS method. We also analyzed xenotimes in leucogranites from South Tibet and granites from Xihuashan in southern China, and obtained accurate and precise ages. Nevertheless, we observed systematic differences in Pb/U fractionation among xenotime, monazite and zircon. The matrix-effect resulted in either under-correction or over-correction of fractionation, and thus led to inaccurate ages. Thus, a matrix-matched material is required for U-Pb dating of xenotime by LA-ICP-MS. 相似文献
10.
DONG ChunYan LIU DunYi LI JunJian WAN YuSheng ZHOU HongYing LI ChengDong YANG YueHeng XIE LieWen 《科学通报(英文版)》2007,52(21):2984-2994
Zircom U-Pb age and Hf isotope analyses were made on gneissic granite and garnet-mica two-feldspar gneiss from the Helanshan Group in the Bayan Ul-Helan Mountains area, the western block of the North China Craton (NCC). Zircons from the gneissic granite commonly show core-mantle-rim structures, with magmatic core, metamorphic mantle and rim having ages of 2323±20 Ma, 1923±28 Ma and 1856±12 Ma, respectively. The core, mantle and rim show similar Hf isotope compositions, with single-stage depleted mantle model ages (TDM1) of 2455 to 2655 Ma (19 analyses). Most of the detrital zircons from the garnet-mica two-feldspar paragneiss have a concentrated U-Pb age distribution, with a weighted mean 207Pb/206Pb age of 1978±17 Ma. A few detrital zircons are older (2871 to 2469 Ma). The age for metamorphic overgrown rim was not determined because of strong Pb loss due to their high U content. The zircons show large variation in Hf isotope composition, with TDM1 ages of 1999 to 3047 Ma. In com- bination with previous studies, the main conclusions are as follows: (1) protolith of the khondalite se- ries in the Helanshan Group formed during Palaeoproterozoic rather than the Archaean as previously considered; (2) The results lend support to the contention that there is a huge Palaeoproterozoic Khondalite (metasedimentary) Belt between the Yinshan Mountains Block and the Ordos Block in the Western Block of NCC; (3) The widely-distributed bodies of early Palaeoproterozoic orthogneisses in the Khondalite Belt might be one of the important sources for detritus material in the khondalite series; (4) Collision between the Yinshan Block, the Ordos Block and the Eastern Block occurred in the same tectonothermal event of late Palaeoproterozoic, resulting in the final assembly of the NCC. 相似文献
11.
The U-Pb isotope compositions of rutile, omphacite and garnet in the eclogite from the Jinheqiao area in the Southern Dabie ultrahigh-pressure metamorphic zone were analyzed. The consistent high precision U-Pb age (218 ±(1.2) Ma of rutile in eclogite from the Dabie Mountains was obtained by two ways of isochron and common Pb correction based on the composition of omphacite. This proves that the omphacite in eclogite has a U/Pb ratio (μ = 2.8) low enough to be used for common Pb correction in the analyses of rutile. Under the rapid cooling condition (40℃/Ma) the closure temperature for U-Pb diffusion in rutile is about 470℃. Thus, this U-Pb age of rutile proves that 218 Ma should be the cooling age of eclogite at 470℃ instead of the peak metamorphic age. 相似文献
12.
A UV laser ablation microprobe-inductively coupled plasma mass spectrometry (LAMICPMS) is used to determine the Pb/Pb and
Pb/U ages of several zircon grains whose ages have been measured by the conventional U-Pb thermal ionization mass spectrometry
(TIMS) method. The mass fractionation factor of Pb isotope ratio was typically between 0.010-0.012 and corrected by NIST610
glass standard. Several factors that influence the stability of Pb/U ratio have been investigated and optimized. The precision
of207Pb/206Pb and206Pb/238U from each sampling crater is within 0.6%—2.4% and 1%—10% respectively, while the precision for the average of mean ratios
from different craters is 0.7% and 6% correspondingly. The207Pb/206Pb and206Pb/238U age differences compared with TIMS results are ≪ 1% and < 3% respectively. 相似文献
13.
SHRIMP U-Pb zircon age of tuff at the bottom of the Lower Cambrian Niutitang Formation,Zunyi, South China 总被引:2,自引:0,他引:2
Zhou MingZhong Luo TaiYi Li ZhengXiang Zhao Hui Long HanSheng Yang Yong 《科学通报(英文版)》2008,53(4):576-583
A SHRIMP U-Pb zircon geochronology study of the tuff at the bottom of the Lower Cambrian Niutitang Formation at Songlin, Zunyi, South China yielded a mean ^206Pb/^238U age of 518±5 Ma. It is significantly younger than the Re-Os ages of 537--542 Ma for the overlying polymetallic Ni-Mo-PGE-rich layer in the basal Niutitang Formation at Songlin, suggesting that the Re-Os ages might represent that of the original magma chamber for the Ni-Mo-PGE-rich layer rather than the formation age of the strata. The intra-basinal stratigraphic correlation also implies that the absolute age of the Chengjiang biota should be younger than 518±5 Ma. Our new result, together with the SHRIMP U-Pb zircon age for the K-bentonite in the Zhongyicun member of the Zhujiaqing Formation at the Meishucun section, Yunnan Province, provides a temporal constraint for the Lower Cambrian of the Yangtze Platform in South China. 相似文献
14.
Forming age and tectono-petrogenises of the Jiugequan ophiolite in the North Qilian Mountain, NW China 总被引:11,自引:0,他引:11
The Jiugequan ophiolite is one of the representative ophiolite fragments in the Early Paleozoic orogenic belt of the North Qilian Mountain. It has been drawn much attention and extensively studied in recent years. In this study, ion microprobe (SHRIMP) U-Pb dating was carried out for zircons from isotropic gabbro from the Jiugequan ophiolite. Eighteen analyses yield a relatively consistent apparent 206Pb/238U ages from 480 to 508 Ma with a weighted mean age of 490±5 Ma (MSWD=1.06), which is believed to be the crystallization age of the gabbro and thus the forming age of the Jiugequan ophiolite. Major and trace element geochemical study indicates that the diabase-basalts from the Jiugequan ophiolite have N-MORB and E-MORB characteristics with some subduction-related signatures. The petrological, geochemical and chronological data enable us to conclude that the Jiugequan ophiolite is most likely to be formed at a spreading center of back-arc basin during the early Ordovician, while the ancient Qilian oceanic plate subducted northwards. The acquisition of forming age and determination of tectonic setting for Jiugequan ophiolite provide significant constraints on the evolution of intra-oceanic subduction system in the North Qilian orogenic belt during the Early Paleozoic era. 相似文献
15.
Mineralizing age of the Rushan lode gold deposit in the Jiaodong Peninsula:SHRIMP U-Pb dating on hydrothermal zircon 总被引:29,自引:0,他引:29
HU Fangfang FAN Hongrui YANG Jinhui WAN Yusheng LIU Dunyi ZHAI Mingguo & JIN Chengwei .Key Laboratory of Mineral Resources Institute of Geology Geo- physics Chinese Academy of Sciences Beijing China .Beijing SHRIMP Centre Institute of Geology Chinese Academy of Geological Sciences Beijing China Correspondence should be addressed to Fan Hongrui 《科学通报(英文版)》2004,49(15):1629-1636
Knowledge of the mineralizing timing is fundamen-tal to understand the genesis of mineral deposits, and ex-act time spectrum of mineralization is essential to com-prehending the relationship among the genesis of en-dogenic hydrothermal deposits, regional tectonic-magma-tism event and the geodynamics of mineral deposits. The Jiaodong or eastern Shandong gold province islocated in the southeastern margin of the North Chinacraton, and belongs to the Mesozoic circum-Pacific oro-genic gold system… 相似文献
16.
Zircon U-Pb dating for the earliest Neoproterozoic mafic magmatism in the southern margin of the North China Block 总被引:7,自引:2,他引:7
LIU Yongqing GAO Linzhi LIU Yanxue SONG Biao WANG Zongxiu 《科学通报(英文版)》2006,51(19):2375-2382
Geological records of Neoproterozoic magmaticevents have recently been identified in the central Phanerozoic orogenic belts of China[1]. In regions of east Qinling orogen[2], Dabie-Sulu orogen[3], north Qaidam Basin orogen[4―6], and southwest Tarim Basin… 相似文献
17.
U-Pb zircon dating constraints on formation time of Qilian high-grade metamorphic rock and its tectonic implications 总被引:5,自引:2,他引:5
XU WangChun ZHANG HongFei LIU XiaoMing 《科学通报(英文版)》2007,52(4):531-538
In order to constrain the formation time of high-grade metamorphic rocks in the Qilian Mountains, U-Pb zircon dating was carried out by using LA-ICPMS technique for a paragneiss of the Hualong Group in the Qilian Mountains basement series and a weakly foliated granite that intruds into the Hualong Group. Zircons from the paragneiss consist dominantly of detrital magma zircons with round or sub-round shape. They have 207Pb/206Pb ages mostly ranging from 880 to 900 Ma, with a weighted mean age of 891 ±9 Ma, which is interpreted as the magma crystallization age of its igneous provenance and can be taken as a lower age limit for the Hualong Group. Magma crystallization age for the weak-foliated granite is 875±8 Ma, which can be taken as an upper age limit for the Hualong Group. Accordingly, the formation time of the Hualong Group is constrained at sometime between 875 and 891 Ma. A few zir- cons from both paragneiss and weak-foliated granite display old inherited ages of 1000 to 1700 Ma and young metamorphic ages of Early Paleozoic. The zircon age distribution pattern confirms that the Qilian Mountains and the northern margin of Qaidam Basin had a united basement, with geotectonic affinity to the Yangtze Block. The results also reveal that sediments of the Hualong Group formed by rapid accumulation due to rapid crustal uplift-erosion. This process may result from intensive Neoproterozoic orogenesis due to assembly of the suppercontinent Rodinia. 相似文献
18.
Ar-Ar and U-Pb geochronology of Late Paleozoic basalts in western Guangxi and its constraints on the eruption age of Emeishan basalt magmatism 总被引:6,自引:0,他引:6
FAN Weiming WANG Yuejun PENG Touping MIAO Laicheng & GUO Feng .Guangzhou Institute of Geochemistry Chinese Academy of Sci- ences Guangzhou China .Institute of Geology Geophysics Chinese Academy of Sci- ences Beijing China 《科学通报(英文版)》2004,49(21):2318-2327
~~Ar-Ar and U-Pb geochronol-ogy of Late Paleozoic basalts in western Guangxi and its constraints on the eruption age of Emeishan basalt magmatism1. GXBGMR (Guangxi Bureau Geological Mineral Resource), Regional Geology of Guangxi, Beijing: Geol. Pub. House, 1985, 1-853.
2. GZBGMR (Guizhou Bureau Geological Mineral Resource), Regional Geology of Guizhou Province, Beijing: Geol. Pub. House, 1987, 1-698.
3. YNBGMR (Yunnan Bureau Geological Mineral Resource), Regional … 相似文献
19.
Zircon U-Pb and Hf isotopes of volcanic rocks from the Batamayineishan Formation in the eastern Junggar Basin 总被引:4,自引:0,他引:4
YuPing Su JianPing Zheng William L. Griffin HuaYun Tang Suzanne Y. O’Reilly XiangYang Lin 《科学通报(英文版)》2010,55(36):4150-4161
An internal structural study was conducted to investigate U-Pb age, trace elements and Hf isotopes of basaltic zircons from
the Batamayineishan Formation. The basalt was obtained from drill well San-Can 1 on the eastern Luliang uplift within the
Junggar Basin. Trace element data of zircons show that all samples are magmatic, with similar REE patterns, including positive
Ce (δCe=5.06–134), but negative Eu (δEu=0.06⦒0.55) anomalies and enrichment in heavy rare earth elements. Among 25 grains, the concordant ages were subdivided
into three groups; ages of 300.4±1.3 Ma (n=11), 339.2±2.7 Ma (n=3) and 392.0±1.7 Ma (n=8). Three remaining grains were nearly concordant, with 206Pb/238U ages of 510±7, 488±6 and 453±6 Ma, respectively. The youngest concordant age (i.e., 300.4±1.3 Ma) could be interpreted as
the formation age of the studied basaltic rock; this is consistent with the sampling position at the upper part of the Batamayineishan
Formation. On the other hand, ages such as Ordovician and early Devonian are consistent with the ages of island-arc volcanic
rocks (enrichment in Pb) or ophiolites around the basin. Moreover, the positive ɛ
Hf(t) values of the early and middle Paleozoic zircons (+3.6–+10.5) may suggest that the basement traversed by the studied volcanic
rocks may be Paleozoic in age, formed from the residual oceanic crust and island-arc complex. The ɛ
Hf(t) values (+4.2–+17.1) of the late Paleozoic (∼300.4 Ma) zircons suggest that the basaltic magmas were derived from partial
melting of the asthenospheric mantle or depleted lithospheric mantle. These magmas were slightly contaminated by the existence
of early-middle Paleozoic materials. The late Carboniferous basalts represent direct eruption of mantle-derived magmas at
the upper crustal level during a post-collisional tectonic setting. We therefore consider that extensive vertical growth of
the continental crust to have occurred before the late Carboniferous. 相似文献
20.
SHRIMP U-Pb zircon geochronology of granulites at Rimana (Southern Tibet) in the central segment of Himalayan Orogen 总被引:2,自引:0,他引:2
LI Dewei LIAO Qunan YUAN Yanming WAN Yusheng LIU Demin ZHANG Xionghua YI Shunhua CAO Shuzhao & XIE Defan . Faculty of Earth Sciences China University of Geosciences Wuhan China . Institute of Geology Chinese Academy of Geosciences Beijing China Correspondence should be addressed to Li Dewei 《科学通报(英文版)》2003,48(23):2647-2650
TheCenozoicHimalayanorogenisimportantinun-derstandingcontinentaldynamicprocesses.Lowercrustal,high-grademetamorphicrockshaverecentlybeendiscov-eredinNamcheBarwaandParmir,i.e.therespectivere-gionsofeasternandwesternsyntaxisoftheorogen[1—4].Eclogitesthatunderwentgranulite-faciesmetamorphismhaverecentlybeenreportedintheCadaareatotheeastofMountEverestinthecentralsegmentoftheHimalayanorogen[5].WiththehelpofthegeologicalsurveyofDing-gyeCountyandChentangSheets(scale1︰250000),high-pressuremafic… 相似文献