期刊文献+
共找到6,400篇文章
< 1 2 250 >
每页显示 20 50 100
Proto-Adamastor ocean crust(920 Ma)described in Brasiliano Orogen from coetaneous zircon and tourmaline 预览
1
作者 Léo A.Hartmann Mariana Werle +4 位作者 Cassiana R.L. Michelin Cristiano Lana Gláucia N. Queiroga Marco P. Castro Karine R. Arena 《地学前缘:英文版》 CAS CSCD 2019年第4期1623-1633,共11页
Proto-Adamastor ocean bathed Rodinia and successor continental fragments from 1.0-0.9 Ga up to0.75 Ga,and evolved into world Adamastor Ocean at 0.75-0.60 Ga.Mesoproterozoic oceanic crust is poorly preserved on contine... Proto-Adamastor ocean bathed Rodinia and successor continental fragments from 1.0-0.9 Ga up to0.75 Ga,and evolved into world Adamastor Ocean at 0.75-0.60 Ga.Mesoproterozoic oceanic crust is poorly preserved on continents,only indirect evidence registered in Brasiliano Orogen.We report first evidence of ophiolite originated in proto-Adamastor.We use multi-technique U-Pb-Hf zircon andδ^11B tourmaline isotopic and elemental compositions.The host tourmalinite is enclosed in metaserpentinite,both belonging to the Bossoroca ophiolite.Zircon is 920 Ma-old,εHf(920 Ma)=+12,HfTDM=1.0 Ga and has’oceanic’composition(e.g.,U/Yb<0.1).Tourmaline is dravite withδ^11B=+1.8‰(Tur 1),0‰(Tur 2),-8.5‰(Tur 3).These characteristics are a novel contribution to Rodinia and associated world ocean,because a fragment of proto-Adamastor oceanic crust and mantle evolved at the beginning of the Brasiliano Orogen. 展开更多
关键词 Coeval ZIRCON and TOURMALINE Bossoroca OPHIOLITE Early Brasiliano OROGEN ZIRCON U-Pb-Hf ISOTOPES ZIRCON trace elements TOURMALINE boron ISOTOPES
在线阅读 下载PDF
Geochronology and Petrochemistry of Volcanic Rocks in the Xaignabouli Area, NW Laos
2
作者 Meifeng Shi Zhenbo Wu +4 位作者 Shusheng Liu Zhimin Peng Linnan Guo Fei Nie Siwei Xu 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第1期37-51,共15页
An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesi... An integrated study of zircon U-Pb geochronology and petrochemistry, together with zircon Lu-Hf isotopes, has been carried out on the basaltic-andesitic tuff and volcanic breccia from the Nam Hang Formation and andesitic tuff from the Muang-Nan Formation in the Xaignabouli area, which had been mapped as the Permian–Early Triassic on the 1 : 1 000 000 geological map or Late Carboniferous on the 1 : 200 000 geological maps. Zircon U-Pb dating of three samples yielded weighted mean ages of 235±2.6, 232±1.4 and 278±2.8 Ma, respectively, suggesting a Late Triassic origin for the Nam Hang Formation and an Early Permian origin for the Muang-Nan Formation. Geochemically, they are characterized by depletions in HFSEs(e.g., Nb, Ta, Ti) and high LILE/HFSE ratios, and they have positive zircon εHf(t) values of 8.7–15.9, which exhibits the continental arc volcanic affinity and partial melting of subducting oceanic slab in the magma source. Combined with spatial occurrence of the volcanic rock and existing geochronological and geochemical data, we suggest that the Xaignabouli-Luang Prabang volcanic belt can be linked to the Loei-Phetchabun belt. The Permian–Triassic volcanic rocks in this belt might be a product of the Nan back-arc basin eastward subduction. 展开更多
关键词 VOLCANIC rock ZIRCON U-Pb GEOCHRONOLOGY geochemistry ZIRCON LU-HF isotope Xaignabouli Laos
Timming of Lithospheric Extension in Northeastern China:Evidence from the Late Mesozoic Nianzishan A-Type Granitoid Complex
3
作者 Jinhua Qin Cui Liu +1 位作者 Yuchuan Chen Jinfu Deng 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第4期689-706,共18页
New zircon U-Pb dates obtained by laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS),whole-rock geochemical data and Sm-Nd and Rb-Sr isotopic data are presented for miarolitic alkaline granites,por... New zircon U-Pb dates obtained by laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS),whole-rock geochemical data and Sm-Nd and Rb-Sr isotopic data are presented for miarolitic alkaline granites,porphyritic syenite and rhyolites of the Nianzishan A-Type granitoid complex(NAGC)in the Great Xing'an Range-Songliao Basin in Northeast(NE)China.New crystallization ages of 112.95±0.93 and 114.1±1.71 Ma for granite and 118.6±0.51 Ma for porphyritic syenite were determined by high-precision LA-ICP-MS.The εNd(t)of the rocks range from +1.85 to+2.06,with Nd model ages(T(DM1))from 671 to 821 Ma,indicating that the NAGC originated from juvenile source rocks and exhibits geochemical characteristics of A1-and A-Type granite which formed in an extensional setting.We attribute the magmatism to regional extension and lithospheric thinning caused by the subduction of the western Pacific Plate about 120 to 100 Ma. 展开更多
关键词 A-TYPE granitee new ZIRCON UU-Pb ZIRCON agees NE China LITHOSPHERIC exxtension
Metallogenic controls on the granite-related W–Sn deposits in the Hunan–Jiangxi region, China:evidence from zircon trace element geochemistry
4
作者 Yuannan Feng Tingguang Lan +2 位作者 Lichuan Pan Tingting Liu Shaohua Dong 《中国地球化学学报:英文版》 EI CAS CSCD 2019年第4期530-540,共11页
The Nanling Range in South China is well known for its rich granite-related W–Sn deposits.To elucidate the controls of different granite-related W–Sn metallogenesis in the region,we chose five representative orerela... The Nanling Range in South China is well known for its rich granite-related W–Sn deposits.To elucidate the controls of different granite-related W–Sn metallogenesis in the region,we chose five representative orerelated granites(Yanbei,Mikengshan,Tieshanlong,Qianlishan,and Yaogangxian intrusions)in the Hunan–Jiangxi region,and studied their magmatic zircon ages and trace element geochemistry.Our new zircon data showed the differences in ages,temperatures and oxygen fugacity of the ore-forming magmas.Zircon U–Pb ages of the Yanbei and Mikengshan intrusions are characterized by 142.4±2.4 and 143.0±2.3 Ma,respectively,whereas the Tieshanlong and Qianlishan intrusions are 159.5±2.3and 153.2±3.3 Ma,respectively.The Sn-related intrusions were younger than the W-related intrusions.The Tiin-zircon thermometry showed that there was no systematic difference between the Sn-related Yanbei(680–744℃)and Mikengshan(697–763℃)intrusions and the W-related Tieshanlong(730–800℃),Qianlishan(690–755℃)and Yaogangxian(686–751℃)intrusions.However,the zircon Ce^4+/Ce^3+ratios of the Yanbei(averaged at 18.3)and Mikengshan(averaged at 18.8)intrusions are lower than those of the Tieshanlong(averaged at 36.9),Qianlishan(averaged at 38.4)and Yaogangxian(averaged at 37)intrusions,indicating that the Sn-related granitic magmas might have lower oxygen fugacities than those of the W-related.This can be explained by that,in more reduced magmas,Sn is more soluble than W and thus is more enriched in the residual melt to form Sn mineralization.The difference in source materials between the Sn-related and the W-related granites seems to have contributed to the different redox conditions of the melts. 展开更多
关键词 W–Sn DEPOSITS South China ZIRCON trace element chemistry Ti-in-zircon thermometry Oxygen FUGACITY
Late Mesozoic magmatism in the East Qinling Orogen,China and its tectonic implications 预览
5
作者 Fan Yang Fei Xue +5 位作者 M. Santosh Gongwen Wang Sung Won Kim Zhiwei Shen Wenjuan Jia Xuhuang Zhang 《地学前缘:英文版》 CAS CSCD 2019年第5期1803-1821,共19页
The Qinling Orogen in Central China records the history of a complex geological evolution and tectonic transition from compression to extension during the Late Mesozoic,with concomitant voluminous granitoids formation... The Qinling Orogen in Central China records the history of a complex geological evolution and tectonic transition from compression to extension during the Late Mesozoic,with concomitant voluminous granitoids formation.In this study,we present results from petrological,geochemical,zircon U-Pb-Lu-Hf isotopic studies on the Lengshui felsic dykes from Luanchuan region in the East Qinling Orogen.We also compile published geochronological,geochemical,and Hf isotopic data from Luanchuan region and present zircon Hf isotopic contour maps.The newly obtained age data yield two group of ages at w145 Ma and 140 Ma for two granite porphyries from the Lengshui felsic dykes,with the w145 Ma interpreted as response to the peak of magmatism in the region,and the w140 Ma as the timing of formation of the felsic dykes.The corresponding Hf isotopic data of the granite porphyries display negative εHf(t) values of e16.67 to e4.61,and Hf crustal model ages (TDM^C) of 2255e1490 Ma,indicating magma sourced from the melting of Paleo- to Mesoproterozoic crustal materials.The compiled age data display two major magmatic pulses at 160e130 Ma and 111e108 Ma with magmatic quiescence in between,and the zircon Hf isotopic data display εHf(t) values ranging from e41.9 to 2.1 and TDM^C values of 3387e1033 Ma,suggesting mixed crustal and mantle-derived components in the magma source,and correspond to multiple tectonic events during the Late Mesozoic.The Luanchuan granitoids are identified as I-type granites and most of these are highly fractionated granites,involving magma mixing and mingling and crystal fractionation.The tectonic setting in the region transformed from the Late Jurassic syn-collision setting to Early Cretaceous within-plate setting,with EeW extension in the Early Cretaceous.This extension is correlated with the NeS trending post-collisional extension between the North China Craton and Yangtze Craton as well as the EeW trending back-arc extension triggered by the westward Paleo-Pacific Plate subduction,eventually leading to lithos 展开更多
关键词 PETROLOGY Geochemistry ZIRCON U-Pb-Lu-Hf isotopes ZIRCON Hf isotopic mapping Luanchuan region East QINLING OROGEN
在线阅读 下载PDF
Magmatic and hydrothermal zircon growth during multiple orogenic cycles in an evolving mantle wedge 预览
6
作者 Jingyi Wang M.Santosh +1 位作者 Shanshan Li Sung Won Kim 《地学前缘:英文版》 CAS CSCD 2019年第2期439-452,共14页
The Hongseong area of the Hongseong-Imjingang Belt in the central-western Korean Peninsula forms part of a subduction-collision system that is correlated with the Qinling-Dabie-Sulu Belt in China. Several serpentinize... The Hongseong area of the Hongseong-Imjingang Belt in the central-western Korean Peninsula forms part of a subduction-collision system that is correlated with the Qinling-Dabie-Sulu Belt in China. Several serpentinized ultramafic bodies carrying blocks of metamorphosed mafic rocks occur in this area. Here we investigate zircon grains in serpentinites from Bibong(BB) and Wonnojeon(WNJ), and high-pressure(HP) mafic granulite from Baekdong(BD) localities based on U-Pb, REE and Lu-Hf analyses. The zircons from BD HP mafic granulite show distinct age peaks at 838 Ma, 617 Ma and 410 Ma, with minor peaks at1867 Ma, 1326 Ma and 167 Ma. The Neoproterozoic age peaks in these rocks as well as in the serpentinites suggest subduction-related melt-fluid interaction in the mantle wedge at this time. The older zircon grains ranging in age from the Early to Middle Paleoproterozoic might represent detrital grains from the basement rocks transferred to the wedge mantle through sediment subduction. The BD HP mafic granulite shows a Middle Paleozoic age peak(Devonian;410 Ma). The 242-245 Ma age peaks in the compiled age data of zircon grains serpentinites from BB and WNJ correspond to a major Triassic event that further added melts and fluids into the ancient mantle wedge to crystallize new zircons. In the chondrite normalized rare earth element diagram, the magmatic zircon grains from the studied rocks show LREE depletion and HREE enrichment with sharply negative Eu and Pr anomalies and positive Ce and Sm anomalies. The REE patterns of hydrothermal zircons show LREE enrichment, and relatively flat patterns with negative Eu anomaly. Zircon Hf signature from the WNJ serpentinite show negative εHf(t)(-18.5 and-23.5) values indicating an enriched mantle source with TDM in the range of 1614 Ma and1862 Ma. Zircons from the BD HP mafic granulite also show slightly negative εHf(t)(average-4.3) and TDM in the range of 1365-1935 Ma. Our study provides evidence for multiple zircon growth in an evolving mantle wedge that witnessed melt and fl 展开更多
关键词 ZIRCON geochronology ZIRCON REE and LU-HF isotopes EVOLVING mantle wedge CONVERGENT margin tectonics Central Korean PENINSULA
在线阅读 下载PDF
The significance of U-Pb zircon ages in zoned plutons: the case of the Flamenco pluton, Coastal Range batholith, northern Chile 预览
7
作者 Natalia Rodriguez Juan Diaz-Alvarado +3 位作者 Carlos Fernandez Paulina Fuentes Christoph Breitkreuz Colombo Celso Gaeta Tassinari 《地学前缘:英文版》 CAS CSCD 2019年第3期1073-1099,共27页
Compositionally zoned plutons, both layered and concentrically arranged, provide granitic exposures where the mechanisms and timing of the magmatic emplacement processes can be studied. The importance of in-situ geoch... Compositionally zoned plutons, both layered and concentrically arranged, provide granitic exposures where the mechanisms and timing of the magmatic emplacement processes can be studied. The importance of in-situ geochemical differentiation and the magma replenishment rates are revealed by geochemistry and field relations, together with the increasingly accurate U-Pb geochronology, which has promoted the knowledge about the pluton incremental assembly theories. The Flamenco pluton, located in the Coastal Range of northern Chile, is part of the Upper Triassic to Early Cretaceous Andean intrusives formed in the western active margin of South America, and present a normal zoned structure with mafic magmatic facies (mostly gabbros and Qtz-diorites) close to the contacts with the host metasediments, and tonalites, granodiorites and granites in the inner areas. A combined study of the field relations, geochemistry and zircon geochronology of the magmatic facies was applied to determine the emplacement sequence of the Flamenco pluton, revealing three distinguishable domains separated by metasedimentary septa. The SW area is constituted by mostly homogeneous leucocratic granodiorites that yielded an age of 213 Ma as the best estimation for their emplacement age. Distinctive geochemical characteristics, such as the absence of an Eu anomaly, the depletion in HREE, or the highest Sr, Sr/Y and Ce/Yb values among the granodioritic facies of the pluton, involve lower T and/or higher P conditions at the magmatic source according to experimental studies. These conditions were established during an early stage of the Andean magmatic arc building that is firstly defined here as Upper Triassic. The NW and E domains of the pluton were sequentially emplaced between 194 Ma and 186 Ma and both the field relations and the detailed geochronological results suggest that the mafic facies intruded latter in the emplacement sequence. To the NW, Qtz-dioritic and gabbroic externally emplaced pulses gave a younger crystallization age of 186.3±1 展开更多
关键词 ZIRCON U-Pb geochronology Zoned PLUTONS Andean MAGMATIC arc Sequential EMPLACEMENT Individual and statistical ZIRCON ages
在线阅读 下载PDF
测点相对位置对离子探针锆石U-Pb定年的影响
8
作者 凌潇潇 李秋立 +2 位作者 刘宇 唐国强 李娇 《岩石学报》 SCIE EI CAS CSCD 北大核心 2019年第8期2615-2624,共10页
离子探针得益于高空间分辨率的特点,在复杂变质锆石的微区原位年代学研究中,其常被作为首选技术手段。对具有复杂环带结构的锆石进行原位分析,通常可以得到岩石多期次地质演化信息,因此在一颗有核(幔)边结构的锆石上进行多点分析是常见... 离子探针得益于高空间分辨率的特点,在复杂变质锆石的微区原位年代学研究中,其常被作为首选技术手段。对具有复杂环带结构的锆石进行原位分析,通常可以得到岩石多期次地质演化信息,因此在一颗有核(幔)边结构的锆石上进行多点分析是常见现象。为了定量地评估多点分析时测点的相对位置对离子探针测量结果的影响,本研究采用目前报道最为均一的锆石标样M257为测试对象,分为四种情况,即同一测点重复测试年龄、同一测点先氧同位素分析后年龄测试、在首个测点的上/下/左/右方且预剥蚀区域有部分重叠的范围内测试、距首个测点有显著距离测试等,进行了系统性U-Pb定年对比实验。结果显示,相对一个颗粒上的首个测点,第二个测点的测试深度和预剥蚀区域的变化会给测试结果带来-5%到+11%的系统偏差,尤以与首个测点的预剥蚀区域有重叠且位于一次离子入射方向后侧的分析点会产生最为显著的系统偏差。因此,在采用离子探针进行副矿物U-Pb测试的时候,当需要原位重复分析或在临近区域多点分析时,需要特别注意多个测点的相对位置和分析顺序。本实验结果指示,以往通过离子探针方法对变质锆石进行过核边多点分析,通过变质锆石边部所获得的年龄结果值得重新审视,有将变质时代持续时间扩大化的隐忧。 展开更多
关键词 离子探针 锆石 U-PB年龄 测试位置 系统偏差
Diffusion of helium in FCT zircon
9
作者 Shun YU Wen CHEN +1 位作者 Jingbo SUN Ze SHEN 《中国科学:地球科学英文版》 SCIE EI CAS CSCD 2019年第4期719-732,共14页
To gain a better quantitative understanding of zircon(U-Th)/He ages and evaluate the applicability of zircon(U-Th)/He dating, the diffusion characteristics, He diffusion kinetics, helium partial retention zone(HePRZ),... To gain a better quantitative understanding of zircon(U-Th)/He ages and evaluate the applicability of zircon(U-Th)/He dating, the diffusion characteristics, He diffusion kinetics, helium partial retention zone(HePRZ), closure temperature, and(U-Th)/He ages were investigated using high-precision laboratory step heating experiments based on the thermally activated diffusion process. The ln(D/a^2) in Fish Canyon Tuff(FCT) zircons determined from laboratory step heating experiments was negatively correlated with reciprocal temperature, as expected for thermally activated volume diffusion. The zircon activation energies ranged from 144 to 184 kJ mol^-1 with a mean of 169±12 kJ mol^-1. The closure temperatures ranged from 144 to 216℃(a cooling rate of 10℃ Ma^-1 and an effective grain radius of 38–60 μm) with an average of 176±18℃. The calculated closure temperature increased with increasing cooling rate, yielding an average zircon He closure temperature of ~136℃ at a slow cooling rate of 0.1℃ Ma^-1, whereas the closure value was ~199℃ at a cooling rate of 100℃ Ma^-1. The closure temperature increased with the equivalent spherical radius assuming a constant cooling rate. The He ages from FCT zircons were negligibly affected by grain size because of the rapid cooling. He preserved in the zircon was sensitive to temperature and holding time, and the temperature range for zircon HePRZ gradually decreased with increasing holding time. The(U-Th)/He ages from 26 FCT zircons yielded an algorithmic mean of 28.3±0.3 Ma(S.E.) and a geometric mean of 28.4±0.3 Ma(S.E.), consistent with the ages of 28.4±1.9 Ma reported by other laboratories. The FCT zircons were characterized by rapid cooling, young(U-Th)/He ages with good reproducibility, and low alpha doses. Weak correlations between the He ages and effective uranium(eU) concentrations from the FCT zircons indicated radiation damage did not significantly affect He diffusivity. 展开更多
关键词 ZIRCON HELIUM DIFFUSION (U-Th)/He CLOSURE TEMPERATURE THERMOCHRONOMETRY
Geochronology and Geochemistry of the Granites from the Longtoushan Hydrothermal Gold Deposit in the Dayaoshan Area,Guangxi:Implication for Petrogenesis and Mineralization
10
作者 Lihua Qian Jianqing Lai +3 位作者 Lifang Hu Rong Cao Shilong Tao Bei You 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第2期309-322,共14页
The gold mineralization in the Longtoushan hydrothermal gold deposit is concentrated within the contact zone of the granitic complex. Whole rock geochemistry and in-situ U-Pb and Hf isotopic data were used to constrai... The gold mineralization in the Longtoushan hydrothermal gold deposit is concentrated within the contact zone of the granitic complex. Whole rock geochemistry and in-situ U-Pb and Hf isotopic data were used to constrain the genesis and age of the granites and related Cu-Au mineralization in the Longtoushan Deposit. The granites mainly consist of the granite porphyry, rhyolite porphyry, porphyritic granite and quartz porphyry. LA-ICP-MS U-Pb dating of zircons from the granite porphyry, rhyolite porphyry and quartz porphyry indicates that they intruded from ca. 94 to 97 Ma. These intrusions exhibit similar trace element characteristics, i.e., right-dipping REE patterns, depletion of Ba, Sr, P and Ti, and enrichment of Th, U, Nd, Zr and Hf. The εHf(t) values of zircons from the granite porphyry, rhyolite porphyry and quartz porphyry range from-26.81 to-8.19,-8.12 to-5.33, and-8.99 to-5.83, respectively, suggesting that they were mainly derived from the partial melting of the Proterozoic crust. The Cu-Au mineralization is mainly related to the rhyolite porphyry and porphyritic granite, respectively. The Longtoushan granites were most likely formed in a post-collisional extensional environment, and the deposit is a part of the Late Yanshanian magmatism related mineralization in the Dayaoshan area and its adjacent areas. 展开更多
关键词 Longtoushan gold deposit RHYOLITE PORPHYRY zircon U-Pb dating Hf ISOTOPES PETROGENESIS CU-AU mineralization
南盘江盆地八渡辉绿岩斜锆石和锆石U-Pb年龄及其地质意义 预览
11
作者 夏文静 闫全人 +5 位作者 向忠金 夏磊 江文 李晓剑 周斌 邓莉 《地球学报》 EI CAS CSCD 北大核心 2019年第2期265-278,共14页
南盘江盆地是华南板块西南缘最大的沉积盆地之一。它的构造属性、形成时间及机制长期存在争议,影响着对华南印支造山过程的准确理解。南盘江盆地内除三叠系填充物外,断续出露着古生代碳酸盐岩。这些古生代碳酸盐岩实为三叠纪盆地下伏地... 南盘江盆地是华南板块西南缘最大的沉积盆地之一。它的构造属性、形成时间及机制长期存在争议,影响着对华南印支造山过程的准确理解。南盘江盆地内除三叠系填充物外,断续出露着古生代碳酸盐岩。这些古生代碳酸盐岩实为三叠纪盆地下伏地层在盆地伸展张开过程中形成的断隆,在这些断隆周边发育有似层状或脉状辉绿岩,记录了南盘江盆地发育初期或早期的地质演化信息。本文用Cameca IMS 1280二次离子质谱仪对南盘江盆地东南部八渡辉绿岩中的斜锆石和锆石进行了U-Pb同位素测试,分别获得206Pb/238U年龄加权平均值(269.3±4.2)Ma(95%置信度,N=15,MSWD=0.27)和(265.0±2.9)Ma(95%置信度,N=8,MSWD=0.02),表明八渡辉绿岩侵位于中二叠世沃德期(Wordian;265.1~268.8 Ma),指示了南盘江盆地在此时处于伸展构造体制。这与南盘江盆地内广泛发育晚二叠世—早三叠世(258~248 Ma)基性岩浆活动,以及南盘江盆地晚二叠世—早三叠世时期沉积环境由碳酸盐岩台地相沉积快速转变为以浊积扇相为主的深水沉积等地质事实,共同表明南盘江盆地在中二叠世—早三叠世处于伸展构造体制。 展开更多
关键词 南盘江盆地 八渡辉绿岩 斜锆石 锆石 SIMS U-PB年龄 动力学背景
在线阅读 下载PDF
The Tashisayi nephrite deposit from South Altyn Tagh,Xinjiang,northwest China 预览
12
作者 Kong Gao Guanghai Shi +6 位作者 Meili Wang Gen Xie Jian Wang Xiaochong Zhang Ting Fang Weiyan Lei Yan Liu 《地学前缘:英文版》 CAS CSCD 2019年第4期1597-1612,共16页
The Tashisayi nephrite deposit is located in South Altyn Tagh.in Qiemo County,Xinjiang Province,northwest China.It is a recent discovery in the vast,well-known Kunlun-Altyn nephrite belt distributed along the south of... The Tashisayi nephrite deposit is located in South Altyn Tagh.in Qiemo County,Xinjiang Province,northwest China.It is a recent discovery in the vast,well-known Kunlun-Altyn nephrite belt distributed along the south of the Tarim Basin,producing more than half of the nephrite from the whole belt in 2017.Field investigations revealed that it is a dolomitic marble-related(D-type)nephrite deposit,but little is known about its age of formation and relationships between the granites and marble.Here we report field investigations,petrography of the neph rite,as well as petrography,geochemistry,geochronology of the zoisite-quartz altered intrusive rock and adjacent granites.An A-type granite is identified with a SHRIMP U-Pb zircon age of 926±7 Ma,suggesting it was emplaced in an extensional tectonic environment at that time.The altered intrusive rock has a cluster of U-Pb zircon age of 433±10 Ma.with similar trace element features to the A-type granite,suggesting it was formed in an extensional regime at this later time.Nephrite formed because of the metasomatism of dolomite marble by hydrothermal fluids.It is inferred that Ca^2+was released from the dolomitic marble by metasomatism forming Ca-rich fluids,which caused alteration of both the intrusive rocks(6.00-8.22 wt.%CaO)and granite(1.76-3.68 wt.%CaO)near the nephrite ore bodies.It is also inferred that Fe^2+from the granite migrated towards the dolomite marble.The fluids gave rise to the formation of Ca-minerals.such as zoisite,in the nephrite and altered intrusive rock,and epidote in the granite.Based on the contact relationships.similarity in hydrothermal processes,and consumption of Ca^2+,the Tashisayi nephrite is considered to have formed at the same time as the alteration of the intrusive rocks,i.e.~433 Ma.The geochronological similarity(~926 Ma.433 Ma)of South Altyn and North Qaidam may suggest that tectonically they belong to one single complex in the past,which was offset by the Altyn Tagh fault(ATF).The similar formation ages of the nephrites from Altyn Tag 展开更多
关键词 NEPHRITE DOLOMITE MARBLE A-TYPE granite Altyn Tagh fault ZIRCON U-Pb dating
在线阅读 下载PDF
Late Jurassic to Early Cretaceous volcanism of Hong Kong:Insights from the Ping Chau Formation 预览
13
作者 Lulin Wang Longlong Zhao +2 位作者 Mingzhong Tian Fadong Wu Xujiao Zhang 《地学前缘:英文版》 CAS CSCD 2019年第2期553-568,共16页
The vast expanse of Mesozoic igneous rocks in Hong Kong contain important geological records of late Mesozoic magmatic events and tectonic processes from the coastal region of Southeast China. Of these,the Ping Chau F... The vast expanse of Mesozoic igneous rocks in Hong Kong contain important geological records of late Mesozoic magmatic events and tectonic processes from the coastal region of Southeast China. Of these,the Ping Chau Formation in the northwestern New Territories is the youngest known stratum. We perform a detailed study of the volcanic rocks of the Ping Chau Formation utilizing zircon U-Pb dating,with major and trace elements geochemistry. LA-ICP-MS zircon U-Pb data reveal Early Cretaceous age from two volcanic rock samples, with zircon crystallization from magmas at 140.3 ± 0.8 Ma and 139.3 ± 0.9 Ma,respectively. These rocks have high contents of total alkalis(Na2O + K2O = 5.58-9.45 wt.%), high-field-strength elements and light rare earth elements, conspicuous negative Eu anomalies, and depletions in Nb, Ta, Ti, Sr, Ba and P. Using this data, in combination with previous studies on the late Mesozoic volcanic belt in Southeast China, we propose that the volcanic rocks of the Ping Chau Formation probably originated from deep melting of the crust in a back-arc extensional setting induced by the subduction of the paleo-Pacific Plate. This formation represents the final stages of Early Cretaceous volcanic activity in Hong Kong, as associated with large-scale lithospheric extension, thinning and magmatism. Our results provide new information that can be used in evaluating the significance of Early Cretaceous volcanism and tectonics in Southeast China. 展开更多
关键词 Hong Kong PING Chau FORMATION Zircon U-Pb dating Geochemistry Early CRETACEOUS SOUTHEAST China
在线阅读 下载PDF
Oligocene subduction-related plutonism in the Nodoushan area,Urumieh-Dokhtar magmatic belt:Petrogenetic constraints from U-Pb zircon geochronology and isotope geochemistry 预览
14
作者 Badieh Shahsavari Alavijeh Nematollah Rashidnejad-Omran +2 位作者 Fatma Toksoy-Koksal Wenliang Xu Jalil Ghalamghash 《地学前缘:英文版》 CAS CSCD 2019年第2期725-751,共27页
Geochemical data and SreNd isotopes of the host rocks and magmatic microgranular enclaves(MMEs)collected from the Oligocene Nodoushan Plutonic Complex(NPC)in the central part of the Urumieh eDokhtar Magmatic Belt(UDMB... Geochemical data and SreNd isotopes of the host rocks and magmatic microgranular enclaves(MMEs)collected from the Oligocene Nodoushan Plutonic Complex(NPC)in the central part of the Urumieh eDokhtar Magmatic Belt(UDMB)were studied in order to better understand the magmatic and geodynamic evolution of the UDMB.New U-Pb zircon ages reveal that the NPC was assembled incrementally over ca.5 m.y.,during two main episodes at 30.52±0.11 Ma and 30.06±0.10 Ma in the early Oligocene(middle Rupelian)for dioritic and granite intrusives,and at 24.994±0.037 Ma and 24.13±0.19 Ma in the late Oligocene(latest Chattian)for granodioritic and diorite porphyry units,respectively.The spherical to ellipsoidal enclaves are composed of diorite to monzodiorite and minor gabbroic diorite(SiO2=47.73-57.36 wt.%;Mg#=42.15-53.04);the host intrusions are mainly granite,granodiorite and diorite porphyry(SiO2=56.51-72.35 wt.%;Mg#=26.29-50.86).All the samples used in this study have similar geochemical features,including enrichment in large ion lithophile elements(LILEs,e.g.Rb,Ba,Sr)and light rare earth elements(LREEs)relative to high field strength elements(HFSEs)and heavy rare earth elements(HREEs).These features,combined with a relative depletion in Nb,Ta,Ti and P,are characteristic of subduction-related magmas.Isotopic data for the host rocks display ISr=0.705045-0.707959,εNd(t)=-3.23 to+3.80,and the Nd model ages(TDM)vary from 0.58 Ga to 1.37 Ga.Compared with the host rocks,the MMEs are relatively homogeneous in isotopic composition,with ISr ranging from 0.705513 to 0.707275 andεNd(t)from-1.46 to 4.62.The MMEs have TDM ranging from 0.49 Ga to 1.39 Ga.Geochemical and isotopic similarities between the MMEs and their host rocks demonstrate that the enclaves have mixed origins and were most probably formed by interactions between the lower crust-and mantle-derived magmas.Geochemical data,in combination with geodynamic evidence,suggest that a basic magma was derived from an enriched subcontinental lithospheric mantle(SCLM),presumably trigger 展开更多
关键词 Urumieh-Dokhtar MAGMATIC BELT Granitoid rocks SUBDUCTION Zircon U-Pb ages Radiogenic isotopes Central Iran
在线阅读 下载PDF
Petrogenesis of the Payangazu Complex in Southern Mandalay, Central Myanmar and Its Tectonic Implications
15
作者 KaixuanLi Huaying Liang +3 位作者 Zhiwei Bao Wenting Huang Jian Zhang Long Ren 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第1期20-36,共17页
The Payangazu complex in the central Myanmar is composed mainly of quartz diorite,granodiorite,and some synplutonic mafic dikes.The quartz diorite and granodiorite have zircon U-Pb ages of 130.5±4.0(MSWD=3.5)and ... The Payangazu complex in the central Myanmar is composed mainly of quartz diorite,granodiorite,and some synplutonic mafic dikes.The quartz diorite and granodiorite have zircon U-Pb ages of 130.5±4.0(MSWD=3.5)and 118.4±2.5 Ma(MSWD=2.4),respectively.Rock samples of the quartz diorite and granodiorite are metaluminous,enriched in large-ion lithophile elements like LREE,Rb,Th,and U,and depleted in high field-strength elements such as HREE,Nb,Ta,P,and Ti,indicative of arc-type magmatic affinities.Whole rock samples of the quartz diorite haveεHf(t)value of+0.6,initial^87Sr/^86Sr ratios of 0.708 6 to 0.710 0,andεNd(t)values of-4.8 to-4.9;whereas rocks of the granodiorite are relatively isotopically enriched,withεHf(t)values of-5.1 to-7.2,initial ^87Sr/^86Sr ratios of 0.711 7 to 0.711 8,andεNd(t)values of-8.7 to-8.8.The isotopic data together with the high Mg#(both the quartz diorite and granodiorite have Mg#values of>40)suggest a strong involvement of mantle materials in the genesis of the parent magmas.The possible petrogenetic process may be that the ascending of melts from partial melting of metasomatized mantle wedge triggered by dehydration of subducted slab resulted in partial melting of the lower crust and mixed with the latter.These Early Cretaceous intrusions from the complex are older than those found in the eastern Wuntho-Popa arc in western Myanmar,eastern Himalaya,and western Yunnan which are interpreted to be related to the Neo-Tethyan subduction,and haveεNd(t),εHf(t)values lower than the latter.On the contrary,the ages and geochemical characteristics of the Payangazu complex are consistent with some of the intrusions in the northern magmatic belt in Tibet,eastern Himalaya,and western Yunnan which are believed to be associated with the subduction of the Bangong-Nujiang Ocean crust.Thus,we propose that the Early Cretaceous intrusions in the central Myanmar are most likely related to the southward subduction of an ocean slab that was possibly an extension of the Bangong-Nujiang Ocean. 展开更多
关键词 CENTRAL Myanmar ZIRCON U-PB age isotope Early CRETACEOUS SUBDUCTION
Piaoac Granites Related W-Sn Mineralization, Northern Vietnam: Evidences from Geochemistry, Zircon Geochronology and Hf Isotopes
16
作者 Tuan Anh Nguyen Xiaoyong Yang +2 位作者 Hien Vu Thi Lei Liu Insung Lee 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第1期52-69,共18页
Piaoac granites exposed in the Cao Bang region, northern Vietnam, are S-type granite, which are associated with W-Sn-Mo-Be-F mineralization. Zircon U-Pb ages, major and trace elements, mineral chemical and Hf isotopic... Piaoac granites exposed in the Cao Bang region, northern Vietnam, are S-type granite, which are associated with W-Sn-Mo-Be-F mineralization. Zircon U-Pb ages, major and trace elements, mineral chemical and Hf isotopic compositions of the W-Sn-bearing granites from the Piaoac District have been investigated in detail. LA-ICP-MS U-Pb dating of zircon grains from these granites yielded ages of 82.5±2.3 and 82±1.8 Ma, representing an episode of Late Cretaceous magmatic event. These granites are characterized by high peraluminous and have typical S-type geochemical signatures with high SiO2(72.37 wt.%–73.07 wt.%), high A/CNK values(1.61–1.65) and Al2O3(14.4 wt.%–15 wt.%). They are enriched in Rb, U, K, Th, Ta and Pb and display pronounced negative Ba, Sr, Nb, Ti and Eu(Eu/Eu*=0.19–0.24) anomalies. The high degree of fractional crystallization is characterized by low Rb, Sr, Ba and Eu concentrations with high ratios of La/Sm and Eu/Eu*. Zircon grains show εHf(t) values from-9.69 to-0.9 and the corresponding TDM2 range from 1.2 to 1.7 Ga, indicating that these granites could be derived from the Proterozoic basement rocks with minor input from mantle-derived magmas. The calculation of Fe3+ and Fe2+ of biotites indicates a low oxygen fugacity condition(log fO2 ranging from 10-17 to 10-18 bars, below MH), which is favorable for the W-Sn mineralization. Tungsten and tin have been enriched in granitic magmas through fractionation, and low oxygen fugacity conditions have promoted the accumulation and transportation of W-Sn in the hydrothermal fluids, leading to deposition of mineral phases. The geochemical data suggest that Piaoac granites formed in an extensional setting related with the Late Cretaceous magmatism occurring large-scale lithospheric extensional in South China Block. 展开更多
关键词 GEOCHEMISTRY ZIRCON U-PB age Hf isotope Piaoac GRANITE W-Sn mineralization Northern Vietnam
沉积物锆石示踪研究进展 预览
17
作者 张硕 杨立辉 +1 位作者 董有进 赵亚军 《西昌学院学报:自然科学版》 2019年第1期58-63,共6页
锆石是指示沉积物物质来源的重要矿物,通过几个典型指标来揭示物源区域与搬运过程。晶体形态反映锆石形成的酸碱环境与结晶温度,粒度指示源区距离与搬运力的变化,微量元素记录物源地地球化学信息与迁移过程,U-Pb同位素的示踪测定锆石的... 锆石是指示沉积物物质来源的重要矿物,通过几个典型指标来揭示物源区域与搬运过程。晶体形态反映锆石形成的酸碱环境与结晶温度,粒度指示源区距离与搬运力的变化,微量元素记录物源地地球化学信息与迁移过程,U-Pb同位素的示踪测定锆石的年龄特征及物源区在时间尺度上的变化特征和空间尺度上的多样性。结合最新的研究理论成果,重点探讨锆石物源示踪原理在沉积物研究中的应用,并对锆石示踪技术在应用过程中出现的问题及研究方向提出一些看法。 展开更多
关键词 锆石 示踪原理 同位素 应用
在线阅读 免费下载
广东玉水铜多金属矿床岩浆活动对永梅坳陷带构造演化的约束:来自花岗斑岩和辉绿岩锆石年龄的证据 预览
18
作者 李莎莎 陈华勇 +2 位作者 彭永新 汪礼明 罗志荣 《地球化学》 CAS CSCD 北大核心 2019年第4期313-324,共12页
众所周知,矿床是地球动力学研究的有效探针。广东省梅州玉水铜铅锌多金属矿床是以产出特富铜铅锌矿石、易采和经济价值高等为特点的中型矿床,前人对该矿床的研究主要集中于矿床成因上,但对矿区分布的花岗斑岩和辉绿岩岩脉及其所指示的... 众所周知,矿床是地球动力学研究的有效探针。广东省梅州玉水铜铅锌多金属矿床是以产出特富铜铅锌矿石、易采和经济价值高等为特点的中型矿床,前人对该矿床的研究主要集中于矿床成因上,但对矿区分布的花岗斑岩和辉绿岩岩脉及其所指示的构造意义缺乏关注。本文在前人研究的基础上,运用激光剥蚀-电感耦合等离子质谱仪(LA-ICP-MS)对矿区内脉状花岗斑岩和辉绿岩进行锆石U-Pb定年,获得花岗斑岩206Pb/238U协和年龄为(128.4±1.0)Ma(MSWD=2.6,n=26);辉绿岩锆石年龄范围分别为1776~1114Ma、533~437Ma、282~255Ma、226~209Ma、186~154Ma、141~125Ma和87~56Ma。结合锆石成因、野外辉绿岩切穿花岗斑岩和黄铜矿脉的关系,认为辉绿岩的结晶年龄为(59.3±2.5)Ma(n=13,MSWD=3.1),形成于晚古新世,其动力学背景为陆缘拉张环境。辉绿岩中继承锆石年龄表明玉水矿区深部不仅存在新元古代的基底物质,还经历了中晚侏罗世、白垩世的中酸性岩浆活动和早古近世的基性岩浆活动,这些岩浆活动与华南地区晚中生代以来发育的多期地壳拉张活动相耦合。本研究也为中国东南部存在50~60Ma地壳拉张事件提供了新的年龄证据。 展开更多
关键词 辉绿岩 花岗斑岩 锆石 LA-ICP-MSU-Pb定年 玉水铜矿
在线阅读 下载PDF
Ore mineral characteristics and zircon U-Pb geochronology of Yuanjiacun iron deposit in Shanxi 预览
19
作者 TONG Yuepeng PENG Xiaolei +2 位作者 LIU Guoqing YUE Liping MA Dongmei 《世界地质:英文版》 2019年第1期9-20,共12页
In order to further understand the ore characteristics and metallogenic age of Yuanjiacun iron deposit in Shanxi, the mineral composition characteristics of iron ore were studied on the basis of field investigation an... In order to further understand the ore characteristics and metallogenic age of Yuanjiacun iron deposit in Shanxi, the mineral composition characteristics of iron ore were studied on the basis of field investigation and microscopic observation. Magnetite, hematite, goethite and pyrite of different stages were identified according to their texture and structure features. Two sets of 207Pb/206Pb ages have been obtained by ICPMS isotope dating of magnetite quartzite, of which the zircon age with metamorphic origin is 1 916±88 Ma, representing the main metamorphic age of iron deposit. Another group of magmatic zircons with rhythmic zones are of 2 280±30 Ma age, representing the diagenetic age of iron formation. In addition, scattered age records after metamorphism indicate frequent hydrothermal events after mineralization. Based on the mineral fabric characteristics and the age data of zircons of different origins, it is known that the deposit has undergone sedimentary mineralization period, metamorphic mineralization period, hydrothermal mineralization period and weathering mineralization period. 展开更多
关键词 Yuanjiacun mineral CHARACTERISTICS ZIRCON U-PB GEOCHRONOLOGY BIF
在线阅读 下载PDF
Late Triassic–Cenozoic Thermochronology in the Southern Sanjiang Tethys, SW China, New Insights from Zircon Fission Track Analysis
20
作者 Li Yang Wanming Yuan +1 位作者 Xiaoyong Zhu Zhen Shi 《地球科学学刊:英文版》 SCIE CAS CSCD 2019年第5期996-1004,共9页
The Sanjiang Tethys orogenic belt is located in the southeast side of the Qinghai-Tibet Plateau. It has undergone the opening and closing movements in different periods of Tethys oceans, complex accretive orogeny and ... The Sanjiang Tethys orogenic belt is located in the southeast side of the Qinghai-Tibet Plateau. It has undergone the opening and closing movements in different periods of Tethys oceans, complex accretive orogeny and strong mineralization from Paleozoic to Mesozoic. Using zircon fission track(ZFT) thermochronology, this study reveals the Sanjiang Tethys has experienced multi-stage tectonic activities during the Late Triassic–Cenozoic. The 15 ZFT ages with their decomposition components obtained from Sanjiang Tethysian region range from 212 to 19 Ma, which not only shows 6 age groups of 212, 179–172, 156–133, 121–96, 84–70 and 50–19 Ma, but also constrains the age limit of the tectonothermal events. These age groups recorded the Paleo-Tethys main and branches ocean opening/closure time. The age-elevation plot indicates the Sanjiang region had differential uplifting and exhumation and fast uplifting times of ca. 133, 116 and 80 Ma, coinciding with the age groups mentioned above. These results show new geochronological evidences and viewpoints. 展开更多
关键词 tectonic events ZIRCON FISSION track analysis TETHYS evolution Sanjiang region Qinghai-Tibet Plateau THERMOCHRONOLOGY
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈