Sample records for adamellite

  1. Discussion on the Geochemical Characteristics and Mmechanism of Rock Formation of the Giant Phenocryst Adamellite in Southeast Mongolia%蒙古国东南部巨斑状二长花岗岩地球化学特征与岩石成因机制探讨

    Institute of Scientific and Technical Information of China (English)

    郭志华; 张宝林; 沈晓丽; 贾文臣; 黄雪飞


    The giant phenocryst adamellite is an important magmatism record of the Mongol Ocean plate in the late period of the Early Paleozoic Era.Their formation age and geochemical characteristics are significant to reveal the tectonic framework and evolution history of the Mongol Ocean plate at that period.The paper presents the zircon U-Pb age of the giant phenocryst adamellite in Southeast Mongolia by LA-ICP MS method.The U-Pb age of zircon of adamellite given is (454.3±3.8) Ma,belonging to the Late Ordovician.The geochemical data of granite show its high-K calc-alkaline nature.The granite is also characterized with high silicon,with SiO2 being 69.82%-75.16%,Al2O3 12.91%-14.49%,and Na2O/K2O 0.60%-0.77%,peraluminous,with aluminum saturation index being in the range of 1.11-1.22,and Mg# index of 39-44.The total content ofREEis 43.47×10-6-158.11×10-6,δEu=0.26-0.49.The REE distribution pattern of adamellite is demonstrated by a significant negative Eu anomaly and a “swallow-type" shape.The spider diagrams of trace elements standardized by primitive mantle show apparent enrichment of Rb,Th,U,K,Zr,Hf,strong depletion of Ba,Sr,P,Ti and medium to slight depletion of Nb and Ta.The initial 143 Nd/144 Nd values are high (0.512 449-0.512 507),and the average value is 0.512 477.The eNd (t) values are all positive (0.2-1.3).The characters of major elements,trace elements,and isotopes show that the giant phenocryst adamellite in the Southeast Mongolia was formed at an extensional geotectonic environment during the transitional period from syn-collision to post-orogenic tectonic systems.The extensional tectonics and the underplating of mantle-derived basic magmas are suggested to be the main dynamic mechanism to form the granite.Since the adamellite is the important magma record of the Mongol Ocean plate subduction in the early Paleozonic,the present research is helpful to reveal the tectonic evolution and the characters in the Palaeo-Mongolia Ocean plate area.%巨

  2. Geochemistry of Rare Earth Elements in Aktishikan Gold Deposit,Xinjiang

    Institute of Scientific and Technical Information of China (English)

    袁峰; 周涛发; 等


    The characteristics and the models of rare earth elements in the geological bodies and the hydrothermal water balancel with the adamellite were comprehensivealy studied in Aktishikan gold deposit,Nurt area of Altay,Xinjiang,And the behavior of rare earth elements during metasomatic alteration was discussed by using the isocon method of Grant,The results show that the rare earth elements are inert during metasomatic alteration,the hydrotheraml water has no relation to the magmatic water,and the gold material sources mainly stem from the wall rock.

  3. Lead isotope systematics of some igneous rocks from the Egyptian Shield (United States)

    Gillespie, J. G.; Dixon, T. H.


    Lead isotope data on whole-rock samples and two feldspar separates for a variety of Pan-African (late Precambrian) igneous rocks for the Egyptian Shield are presented. It is pointed out that the eastern desert of Egypt is a Late Precambrian shield characterized by the widespread occurrence of granitic plutons. The lead isotope ratios may be used to delineate boundaries between Late Precambrian oceanic and continental environments in northeastern Africa. The samples belong to three groups. These groups are related to a younger plutonic sequence of granites and adamellites, a plutonic group consisting of older tonalites to granodiorites, and the Dokhan volcanic suite.

  4. Geochemistry of Rare Earth Elements in Aktishikan Gold Deposit, Xinjiang

    Institute of Scientific and Technical Information of China (English)

    袁峰; 周涛发; 岳书仓


    The characteristics and the models of rare earth elements in the geolo gical bodies and the hydrothermal water balanced with the adamellite were compre h ensively studied in Aktishikan gold deposit,Nurt area of Altay,Xinjiang.And th e behavior of rare earth elements during metasomatic alteration was discussed by using the isocon method of Grant.The results show that the rare earth elements a re inert during metasomatic alteration,the hydrothermal water has no relation t o the magmatic water,and the gold material sources mainly stem from the wall rock.

  5. Estimate of influence of U-Th-K radiogenic heat on cooling process of granitic melt and its geological implications

    Institute of Scientific and Technical Information of China (English)


    The U-Th-40K concentrations of granite are on 1―2 orders of magnitude greater than those of basal- tic-ultrabasic rocks. Radiogenic heat of a granitic melt has significant influence on the cool- ing-crystallization period of the melt. In this paper we derived a formula to calculate prolongation period (tA) of cooling-crystallization of a granitic melt caused by radiogenic heat. Calculation using this for- mula and radioactive element concentrations (U=5.31×10-6; Th=23.1×10-6; K=4.55%) for the biotite adamellite of the Jinjiling batholith shows that the tA of the adamellite is 1.4 times of the cooling period of the granitic melt without considering radiogenic heat from the initial temperature (Tm=960℃) to crystallization temperature (Tc=600℃) of the melt. It has been demonstrated that the radiogenic heat produced in a granitic melt is a key factor influencing the cooling-crystallization process of the granitic melt, and is likely one of the reasons for inconsistence between emplacement ages and crystallization ages of many Meso-Cenozoic granitoids.

  6. Estudio petrológico del plutón de Trujillo (Cáceres. España

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    Guijarro, J.


    Full Text Available From the petrogenetic study is established that pluton of Trujillo is an porphyritic adamellite, crystallised in three phases with an alteration one. Later, the porphyritic microadamellite crystallised in three petrogenetic facies: biotitic, leucocratic and turmaline. Each facies has three crystalitation phases and an alteration one. The major elements were analysed in adamellites, microadamellites and contacts between tugsten veins and porphyritic adamellite. From Harker, AFM and CaO-Na2O-K2O diagrams is emphasized an alcaline and peraluminic character. The distribution of trace elements is agree with the material evolution; Rb, Cs. Sr. Ba y Li settle better this connection.

    En función del estudio petrológico, el plutón de Trujillo está constituido por una adamellita porfídica que ha cristalizado en tres fases, presentando una cuarta de alteración. Posteriormente consolidó la microadamellita porfídica, bajo tres facies petrogenéticas, en el siguiente orden: Biotítica, leucocrática y turmalinizada. Cada una de estas tres facies comportan tres fases de cristalización y una de alteración. El análisis de elementos mayores ha sido realizado en las adamellitas, microadamellitas y en los contactos de: los filones volframíferos con la adamellita porfídica. De la interpretación del los diagramas de Harker y de los triangulares AFM y CaO-Na2-K2O se deduce un marcado carácter alcalino y peraluminoso en los tres grupos de muestras. Se han analizado también numerosos elementos traza, observándose una cIara concordancia entre el grado de diferenciación del material y el contenido en dichos elementos; siendo Rb, Cs, Sr, Ba y Li los que mejor reflejan dicha evolución.

  7. Late Triassic syn-exhumation magmatism in central Qiangtang, Tibet: Evidence from the Sangehu adakitic rocks (United States)

    Liu, Han; Wang, Bao-di; Ma, Long; Gao, Rui; Chen, Li; Li, Xiao-bo; Wang, Li-quan


    The geodynamic setting of Late Triassic magmatic activity along the Longmu Co-Shuanghu suture zone (LSSZ) in central Qiangtang, Tibet is a matter of debate. This paper presents zircon LA-ICP-MS U-Pb ages, zircon Hf isotopic compositions, and whole-rock geochemical data for the Sangehu (SGH) granitic intrusion in central Qiangtang, and addresses the petrogenesis of Late Triassic magmatism, and the history of collision between the northern and southern Qiangtang terranes. The SGH pluton consists mainly of biotite adamellite with mafic microgranular enclaves (MMEs), and small amounts of K-feldspar granite. The biotite adamellite, MMEs, and K-feldspar granite give ages of 207.8 ± 3.0 Ma, 212.4 ± 31 Ma, and 211.6 ± 3.8 Ma, respectively. The MMEs show magmatic textures and acicular apatite, and are coeval with the host biotite adamellite, suggesting they were produced by magma mixing. All samples from the SGH pluton show high Sr and low Y contents, and positive Eu anomalies, similar to adakitic rocks. The high K2O contents and low Mg#, Cr, and Ni contents, and enriched Hf isotopic characteristics of the zircons indicate that these magmas were derived from the partial melting of thickened crust. However, the whole-rock geochemical data and zircon Hf isotopic compositions also reveal heterogeneity at the source. The combined magmatic and metamorphic records suggest that Triassic magmatic activity in central Qiangtang was closely related to the collision of the northern and southern Qiangtang terranes. The large-scale Late Triassic (225-200 Ma) magmatic event in central Qiangtang may have resulted from the breakoff of the Longmu Co-Shuanghu Tethys Ocean lithospheric slab in the early Late Triassic (236-230 Ma). The Late Triassic magmatic rocks, including adakitic rocks, are coeval with retrograde high-pressure (HP) to ultrahigh-pressure (UHP) metamorphic rocks in central Qiangtang, and show characteristics of syn-exhumation magmatism. The early adakitic rocks (>220 Ma

  8. Geological features and prospecting criteria of Wangkaigou silver deposit in Helong City%和龙市王开沟银矿床地质特征及找矿标志

    Institute of Scientific and Technical Information of China (English)

    陶胜辉; 单贺; 张天瑞; 陶立新


    王开沟银矿床位于和龙市南约55 km,隶属龙城镇管辖。银矿体赋存于晋宁期二长花岗岩之中,呈脉状分布,该文总结了矿床地质特征,确定了该区银矿床的找矿标志。%Wangkaigou silver deposit is located in south 55 km away from Helong City, in the Longcheng Town’s jurisdiction. Silver ore bodies occur in adamellite of Jinningian, nervation distribution. This paper summarized the deposit’s geological features, determined the prospecting criteria of the silver deposit.

  9. Petrogenesis and tectonic setting of the early Mesozoic Xitian granitic pluton in the middle Qin-Hang Belt, South China: Constraints from zircon U-Pb ages and bulk-rock trace element and Sr-Nd-Pb isotopic compositions (United States)

    Wu, Qianhong; Cao, Jingya; Kong, Hua; Shao, Yongjun; Li, Huan; Xi, Xiaoshuang; Deng, Xuantong


    The Xitian pluton in southeast Hunan province is one of the early Mesozoic (Indosinian) granitic plutons in the South China Block. It is composed of biotite adamellite with K-feldspar megacrysts, biotite adamellite, and biotite granite that have U-Pb zircon ages of 229.9 ± 1.4 Ma, 223.6 ± 1.3 Ma, and 224.0 ± 1.4 Ma, respectively. The Indosinian granitoids in the Xitian pluton belong to S-type granites, with highly radiogenic initial 87Sr/86Sr ratios (0.71397-0.71910), negative εNd(t) values ranging from -10.1 to -9.4, and old Nd model ages (1858-1764 Ma). They are enriched in radiogenic Pb isotopes, with (206Pb/204Pb)t ranging from 18.130 to 18.903, (207Pb/204Pb)t from 15.652 to 15.722, and (208Pb/204Pb)t from 38.436 to 39.037, respectively. These features indicate that the granitoidswithin the Xitian pluton were formed from magmas generated by remelting of metapelite and metapsammite of the Paleoproterozoic metamorphic basement at temperatures of ca. 800 °C, with low oxygen fugacity. The Sr-Nd isotopic compositions of the rocks from Xitian pluton indicate that the granitic magmas were mixed with less than 10% mantle-derived magmas. We suggest that the Xitian pluton was emplaced in an extensional tectonic setting related to release of compressional stresses within the thickened crust during the early Mesozoic.

  10. The New England Batholith, eastern Australia: Geochemical variations in time and space (United States)

    Shaw, S. E.; Flood, R. H.


    The New England Batholith, Australia, is part of the Upper Paleozoic New England Fold Belt, with most plutons intruded into the deformed trench-complex metasedimetary rocks in the southeast part of the Fold Belt. The Batholith was emplaced in two major periods of plutonism, the first during the Upper Carboniferous and the second during the Upper Permian and Triassic, with a major phase of metamorphism and deformation including westward overthrusting of the trench-complex sedimentary rocks between the two periods. On the basis of petrography, geochemistry and isotopic characteristics, the granitoids of the Batholith are subdivided into five named intrusive suites and a group of leucoadamellites. The differences between the six groups are considered to reflect differences in their source-rock types. The Carboniferous granitoids are peraluminous S-type and are divided into the Bundarra Plutonic Suite, a belt of very coarse-grained adamellites with cordierite ± garnet, and the Hillgrove Plutonic Suite, a belt of biotite-rich ± garnet deformed adamellites and granodiorites. Both suites have δ 18O greater than 10, negative δ34S, 87Sr/86Sr initial ratios about 0.706, are ilmenite-bearing and have low FeO3 ratios. The Bundarra Plutonic Suite, however, is consistently SiO2-rich (greater than 70%), contains cordierite and has higher δ18O than the Hillgrove Plutonic Suite. The two S-type suites are inferred to have formed by partial melting of the deepest parts of a wedge of trench-complex sedimentary rocks oceanwards of an `Andean' volcanic chain to the west, analagous to the lower Tertiary S-type plutons of the Sanak-Baranof plutonic belt of southern Alaska. Of the remaining four groups of plutons emplaced during the Upper Permian and Triassic, two are metaluminous I-type granitoids, one the Clarence River Plutonic Suite (new name), a group of K-poor granodiorites and tonalites with low 87Sr/86Sr initial ratios (average 0.7035), and the other the Moonbi Plutonic Suite

  11. Records of Indosinian Orogenesis in Lhasa Terrane, Tibet

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    Li Huaqi; Xu Zhiqin; Yang Jingsui; Cai Zhihui; Chen Songyong; Tang Zemin


    Based on the deformation characteristics of the ductile shear zones in Sumdo (松多) Group, the quartz fabric by EBSD (electron backscatter diffraction), the data of muscovite 40Ar-39Ar geochronology (220-230 Ma) from ductile shear zones and the zircon SHRIMP U-Pb chronology (190 Ma) of granites in Snmdo region, Lhasa (拉萨) terrane is thought to have experienced an important Indosinian orogenic event at 220-230 Ma, which caused the closure of the paleo-Tethys Ocean along the tectonic zone of eclogite and the collision between northern part and southern part of the Lhasa terrane. The zircon SHRIMP U-Pb chronology of 190 Ma for biotite adamellite, with the distributing characteristics of the granite massif intruding in Sumdo Group, indicates that the biotite adamellitc should be the late orogenic or post-orogenic granite resulting from the lndosinian orogenesis. The discovery of Indosinian orogenic belt in Lhasa terrane expansed the southern boundary of lndosinian orogenic belt in Qinghai (青海)-Tibet plateau to Lhasa terrane from Qiangtang (羌塘) terrane, which changed the understanding about the distribution of Indosinian orogenic belt in Qinghai-Tibet plateau and extended the "T" type lndosinian orogenic belt in China. The study is very important for the formation and distribution of paleo-Tethys Ocean in Tibet. The ancient terrane framework and evolution of Qinghai-Tibet plateau need further research.

  12. Magma mixing in the Kalaqin core complex, northern North China Craton: Linking deep lithospheric destruction and shallow extension (United States)

    Fu, Lebing; Wei, Junhao; Tan, Jun; Santosh, M.; Zhang, Daohan; Chen, Jiajie; Li, Yanjun; Zhao, Shaoqing; Peng, Lina


    The widespread Mesozoic magmatism in the North China Craton (NCC) has received considerable attention as a trigger for large scale lithospheric destruction. Here we investigate the Early Cretaceous Jiguanzi adamellite from the northern part of the NCC which is contemporaneous with shallow extensional deformation and deep lithospheric destruction. This intrusion emplaced at ca. 133 Ma is located in the foot wall of the Kalaqin metamorphic core complex (MCC), and occurs as a synextensional ring complex with numerous magmatic equigranular (Group 1) and porphyritic (Group 2) enclaves. Hornblende and plagioclase from the host adamellite and xenocrysts of Group 2 enclaves show distinct inverse zoning with Mg- and Ca-rich mantle. The Group 2 enclaves are characterized by plagioclase xenocrysts hosting hornblende, biotite and apatite inclusions, quartz ocelli with fine-grained rim enriched in biotite and hornblende, and poikilitic biotite surrounded by hornblende. Geochemically, the host intrusion is calc-alkaline to alkaline and metaluminous with variable contents of SiO2 (60.70-72.20 wt.%), Al2O3 (14.19-17.22 wt.%), Na2O + K2O (6.16-9.42 wt.%), and Mg# values (28.0-47.7), whereas the Group 2 enclaves exhibit low SiO2 (54.05-55.55 wt.%), high Fe2O3 (8.18-8.64 wt.%) and TiO2 (2.08-2.28 wt.%), and moderate Mg# (44.0-44.1). Both the host intrusion and Group 2 enclaves are enriched in large-ion lithophile and light rare earth elements, and depleted in high field strength elements and heavy rare earth elements except that the latter has lower Ba and high Nb, Ta and Ti contents. The major and trace element contents of the Group 1 enclaves are broadly similar to those of the host intrusion. Analyses of Sr-Nd-Hf isotopes in the host intrusion, and in Group 1 and Group 2 enclaves show (87Sr/86Sr)ihost = 0.70600-0.70618, εNd(t)host = - 8.2 to - 9.6, T2DM(Nd)host = 1592-1706 Ma, εHf(t)host = - 9.2 to - 12.0, (87Sr/86Sr)iGroup 1 = 0.70590-0.70635, εNd(t)Group 1 = - 9.6 to - 10

  13. Abundances of chemical elements of the granitoids in different geotectonic units of China and their characteristics

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    SHI Changyi; YAN Mingcai; CHI Qinghua


    On the basis of actual analytical data of 767 composited samples collected mainly from about 750 large to middle representative granitoid bodies all over China, the average chemical compositions and element abundances of about 70 chemical elements of SiO2, Al2O3, Fe2O3, FeO, MgO,CaO, Na2O, K2O, H2O+, CO2, TFe2O3, Ag, As, Au, B, Ba, Be,Bi, Cd, Cl, Co, Cr, Cs, Cu, F, Ga, Ge, Hf, Hg, Li, Mn, Mo, Nb,Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ta, Th, Ti, Tl, U, V, W, Zn,Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y in alkalifeldspar granite, syenogranite and adamellite in 7 geotectonic units in China such as Tianshan-Xing'an orogenic series, Sino-Korean metaplatform, Kunlun-Qilian-Qinling orogenic series, Yunnan-Tibet orogenic series,Yangtze metaplatform, South China-Youjiang orogenic zone and Himalayan orogenic belt, are calculated and presented in this paper. In addition, the characteristics of petrochemical parameters, trace element contents and rare earth element dis-tributions of different rock types of the granitoids in different geotectonic units are also sufficiently discussed.

  14. Petrogenesis of Paleoproterozoic Luyashan charnockitic rocks in Shanxi Province: Constraints from Geochemistry and Nd isotope

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    Luyashan charnockite pluton mainly consists of monzonite, adamellite, charnockite and syenogranite, which are characterized by the enrichment of TiO2, P2O5, K2O, Zr, Nb, Y, Pb, La, Ce, Ba and a higher K2O/Na2O and depletion of MgO, CaO,Mg#, Th, U and lower Sr/Ba and Rb/Ba. The negative correlations between Zr, Nb, Ce and SiO2 are distinct from Ⅰ-type granites. Isotopically Luyashan charnockite plutons are relatively uniform in Nd isotope, displaying initial εNd( t ) ( - 5.93 to - 6.97) and Nd depleted mantle model ages (2.67 Ga to 2.78 Ga). These features indicate that Luyashan charnockitic magma derived from pre-existing late Archean crustal sources and the partial melting of mafic granulites probably under exceptionally high temperature with CO2-rich fluid. The garnet is a main residual phase during the partial melting. The original dry charnockitic magma experienced crystal fractionation of pyroxene, plagioclase, apatite and ilmenite during early crystallization. The geochemical evidence suggests that the Luyashan charnockitic magma was probably generated in the post-collision thermal relaxation and uplift tectonic setting after the main collision ( - 1850 Ma) between the Eastern and Western continental blocks.

  15. 藏东类乌齐地区始新世钾玄质侵入岩特征及构造环境%Characteristics and tectonic environment of Eocene shoshonitic intrusive rocks in Leiwuqi region of eastern Tibet, China

    Institute of Scientific and Technical Information of China (English)

    邱军强; 强巴扎西; 丁希国; 李虎; 拉巴次仁


    Wangguotong Pluton is located in Wangguotong, Leiwuqi region of eastern Tibet The rock type is porphyritic biotite adamellite, the biotite K-Ar isotopic age is 35 Ma, and the rock is Eocene in age. Wangguotong granite is rich in silicon, aluminum and alkali, has high potassium and poor titanium content, and low in iron, magnesium and calcium. In the diagram of the SiO2-K2O and K2O-Na2O, the samples all belong to the series of shoshonitic rocks, shoshonitic granite in rock series. The rock shows high concentration of large ion lithophile elements and light rare earth elements, and negative Eu abnormality, and it also shows Th strong concentration on the original cobweb diagram, Sr low negative abnormality, and losses of high-field strength elements Nb, Ta and Ti. These all indicate the geochemical characteristics of shoshonitic rock. By using the discrimination diagram of tectonic environment, it is proved that the Wangguotong granite is formed in post-collisional tectonic environment.%往过同岩体位于藏东类乌齐地区往过同,岩石类型为斑状中粒黑云母二长花岗岩,黑云母K-Ar同位素年龄为35 Ma,时代为始新世.往过同花岗岩富硅、铝、碱,高钾贫钛,低铁、镁、钙,在SiO2-K2O和K2ONa2O图解中样品均落在钾玄岩系列区,岩石系列为钾玄质花岗岩.岩石富集大离子亲石元素和轻稀土元素,负Eu异常;在原始地幔蛛网图上Th强烈富集,Sr呈现低谷负异常,高场强元素Nb、Ta、Ti亏损,表现出钾玄岩的地球化学特征.经分析,并应用构造环境判别图解,往过同花岗岩形成于后碰撞的构造环境.

  16. Geological features and prospecting criteria of Binghugou cryptoexplosive breccia type gold deposit,Huadian City of Jilin Province%吉林省桦甸市冰湖沟隐爆角砾岩型金矿床地质特征及找矿标志

    Institute of Scientific and Technical Information of China (English)

    曹建锋; 宁林; 孟祥秋; 牛庭瑞


    Binghugou gold deposit is located in well-known Jiapigou gold-ifeld SE fringe in our country, exposed rocks are principally Archean ~ Phanerozoic high metamorphic granitoid,and then are Sandaolliuhe TTG petrofabrics and felsic gneiss and metamorphic crustose. Binghugou gold deposit occurred in adamellite and cryptoexplosive breccia pipe controlled byNE ductile shear zone and NW compresional fault.Gold is mainly in gold-silver ores and silver-gold ores, showing micro granulate and distributing over quartz and pyrite and limonite mineral grains or crystal face. Metallogenic epoch is approximately divided into endogenous hydrothermal stage and supergene oxidation stage, among them, endogenous hydrothermal stage is the main ore–forming stage. Cryptoexplosive breccia is main prospecting criteria, silication , pyritization and limonitization are main mineralized alteration indicator.%冰湖沟金矿床位于我国著名的夹皮沟金矿田南东缘,出露岩石主要为太古宙—显生宙高级变质的花岗岩类,其次是三道溜河TTG岩组、长英质片麻岩和变质表壳岩。冰湖沟金矿床赋存于二长花岗岩与NE向韧性剪切带NW向压性断裂控制的隐爆角砾岩筒中。金以金银矿和银金矿为主,呈显微粒状分布于石英、黄铁矿、褐铁矿等矿物颗粒中或晶面上。成矿期大致可分为内生热液期和表生氧化期,其中内生热液期为主成矿期。隐爆角砾岩为主要的找矿标志,硅化、黄铁矿化、褐铁矿化是主要的矿化蚀变标志。

  17. 黑龙江多宝山古生代海盆闭合的岩石学证据%Petrological evidence of Paleozoic marine basin closure in Duobaoshan of Heilongjiang

    Institute of Scientific and Technical Information of China (English)

    赵焕利; 刘旭光; 刘海洋; 朱春艳


    The Paleozoic sedimentary strata, fossils, geochemistry of intrusive rocks and the zircon U-Pb isotopic dating of Duobaoshan in Heilongjiang Province have been comprehensively studied. They are the marine sedimentary strata from Early Ordovician to the early Late Devonian, sea-land interbeddind sediments in the late Late Devonian, and the continental fluvial and lacustrine deposits in Early Carboniferous. It is exposed a set of granites with (300 ± 3 ~ 357 ±4) Ma in southeastern Duobaoshan marine basin. Syenite fine-grained and adamellite finegrained mylonites are post-orogenic granites, and alkali granites are post-orogenic granites in A-type. That means the Duobaoshan marine basin closed from Late Devonian, became continental sedimentary in Early Carboniferous,and in uplift and erosion stage in Late Carboniferous-Early Permian. The fact performed that the orogeny of Duobaoshan area began in Early Carboniferous, and post-organic extension continued from Late Carboniferous to Late or Early Permian.%综合研究黑龙江多宝山地区古生代沉积地层、生物化石,通过分析侵入岩岩石地球化学及其锆石U-Pb同位素测年资料,表明该地区早奥陶世至晚泥盆世早期为海相沉积地层,晚泥盆世晚期为海陆交互相沉积地层,早石炭世为陆相河湖沉积地层.多宝山海盆东南侧出霉一套年龄为(300±3~357±4) Ma的花岗岩,其中正长、二长花岗质糜棱岩为后造山花岗岩,碱长花岗岩为造山后A型花岗岩.表明多宝山海盆于晚泥盆世开始闭合,至早石炭世为陆相河湖沉积,晚石炭世一早二叠世为抬升剥蚀阶段.表现为多宝山地区于早石炭世开始造山,晚石炭世晚期或延至早二叠世发生造山后伸展作用.

  18. 滇东北东川下田坝A型花岗岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及其构造意义%LA-ICP-MS zircon U-Pb age and geochemistry of Xiatianba A-type granites in Dongchuan, Northeast Yunnan, and their tectonic significance

    Institute of Scientific and Technical Information of China (English)

    武昱东; 王宗起; 罗金海; 程家孝; 闫全人; 张英利; 王师迪


    通过对滇东北东川下田坝地区黑云母二长花岗岩和似斑状钾长花岗岩2种岩体的地球化学分析及对黑云母二长花岗岩的U-Pb同位素测试,得到如下认识:黑云母二长花岗岩和似斑状钾长花岗岩总体地球化学特征相似,主量元素表现出高SiO2(平均71.7%)、过铝质(A/CNK指数在1.03~1.52)的特征,过碱指数在0.95~1.37之间,总体属于钙碱系列;稀土元素总量较高(ΣREE平均313×10-6),(Ce/Yb)N均值为8.85,(La/Yb)N均值为9.54,呈现轻稀土元素(LREE)富集,仅Eu亏损(δEu均值0.31)的海鸥型右倾模式;大离子亲石元素Rb、Th、U、K等相对富集,高场强元素Nb、Ta、Sr、Ti等呈明显负异常,说明岩浆源岩以陆壳成分为主;Ga/Al均值为2.69,(Zr+Nb+Ce+Y)均值为383;微量元素Sr、Eu低,富集Nb、Zr等元素,反映其源区存在斜长石的残留;锆石饱和温度为724~786℃,表明初始岩浆温度较高。上述特征说明,下田坝花岗岩为典型的A型花岗岩,形成于中上地壳的板内伸展背景。黑云母二长花岗岩LA-ICP-MS锆石U-Pb年龄为801.1±6.6Ma,同时受到762.1±6.2Ma热事件的影响,与新元古代Rodinia超大陆裂解事件在时间上一致,亦与东川铜矿成矿时代相符,说明新元古代裂谷环境的岩浆事件范围可扩大至滇东北东川,并可能引发热液成矿作用。%Geochemical analysis and LA-ICP-MS zircon U-Pb dating of Xiatianba granites of two granitic bodies in Dongchuan of northeast Yuannan were conducted in this study. The general geochemical characteristics of biotite adamellite and porphyraceous moy-ite are similar to each other, characterized by high SiO2(71.7% on average)and belonging to the peraluminous (A/CNK value be-tween 1.03~1.52) and alkaline series (AI value between 0.95~1.37). They have highΣREE content with an averageΣREE value of 313 × 10-6, an average(Ce/Yb)N value of 8

  19. Origen de arcillas alumínicas en horizontes de alteración de materiales graníticos del borde sur de la sierra de Guadarrama

    Directory of Open Access Journals (Sweden)

    Martín Patino, M. T.


    Full Text Available Three weathering profiles of granitic rocks and two arkoses in the NW of Madrid Province have been studied. Rocks are granodiorites and adamellites with albites showing variable degrees of sericitization, and no-weathered potassic feldspars. Clay fraction in the weathered horizons from these rocks displays high content in beidellite, and minor amounts of illite and 7 Ǻ-halloysite. On the other hand, beidellite, illite and well crystallized kaolinite are clay minerals in the arkosic rocks. Microfabric characteristics from SEM studies show abundant weathered albites with clean surfaces and formation of beidellite in all areas of the samples. Moreover, spatial relations between albite and beidellite are not observed. In pedochemical weathering of albite, sodium from this mineral should be exchanged with protons from soil solution with very quick kinetics. This initial alkalinization produces an increase in the silica solubility released from albite network. In these environments, a continued contact between weathering solution and albite causes a silica and alumina enrichment and beidellite or 7 Ǻ-halloysite precipitation. Microclimatic variations in weathering environment may cause fluctuations in silica and alumina activities with resultant pH changes. So, when silica activities are high, beidellite neoformation is favoured; on the contrary, 7 Ǻ-halloysite is precipitated.Se han estudiado tres perfiles de alteración de rocas graníticas y dos muestras de arcosas en la zona NO de la provincia de Madrid. Las rocas, clasificadas como granodioritas y adamellitas, presentan albitas con sericitización variable, y escasos feldespatos potásicos muy poco alterados. La fracción arcilla de los horizontes de alteración de estas rocas presenta un alto contenido en beidellita, así como porcentajes menores de ilita y haloisita-7Ǻ. Por otra parte, los minerales de la arcilla presentes en las arcosas son ilita, beidellita y caolinita bien

  20. Zircon U-Pb geochronology, geochemistry and its geological implications for the Precambrian granitoids in Zhongtiao Mountain, Shanxi Province%中条山前寒武纪花岗岩地球化学、年代学及其地质意义

    Institute of Scientific and Technical Information of China (English)

    张瑞英; 张成立; 第五春荣; 孙勇


    Complex. Henglingguan and Xiezhou biotite adamellites are similar in the petrography and geochemistry feature, and have almost same forming age ( with a zircon age of 2609 ±31 Ma and 2620 ± 14Ma), suggesting that the two granitoid instrusions are the product of the same magmatism. Yanzhuang K-feldspar granite was formed in Paleoproterozoic (2351 ±37Ma). In-situ zircon Lu-Hf isotopic analyses for three granitoids show that their εHf(t) range from -2.3to +4.8, +4.4to +7.6and -1.8to +7. 8, and the corresponding two-stage model age are 2791 ~3222Ma, 2628 -2823Ma and 2408 ~2996Ma, respectively. Through multidisciplinary analysis lithology, litho-chemistry and Hf isotopic of the granites and combined with the setting regional structure, we suggested that the two Neoarchean granitic rocks belong to high-potassium cala-alkaline I-type granites and probably the result of the partial melting of ~ 2.7Ga TTG rocks and mafic lower crust. The Paleoproterozoic Yanzhuang granite is typically characterized by low Sr and Yb and similar to Himalayan-type granitic rocks, which is related to the partial melt of continental crust caused by crustal thickening. The paper, based on previous and the author' s own research results, summarizes that there is no obvious episodic character of crustal growth of the central North China Craton in the long period of 1.0Ga between ~ 2. 8Ga and ~ 1. 8Ga, but displays a feature of small frequency persistent pulsing growth, indicating that the eastern and western NCC and the Trans-North China Orogen should be a unified continental block in the Late Archaean.

  1. 青藏高原冈底斯带南缘泽当多金属矿田多期岩浆活动及年代意义%Multistage Magmatism of the Zetang Polymetallic Orefield on the Southern Margin of the Gangdise Belt in the Tibetan Plateau and Its Chronological Significance

    Institute of Scientific and Technical Information of China (English)

    赵珍; 吴珍汉; 胡道功; 陆露


    Five-phase acidic magmatism was identified though nearly three years’ field observation, test analysis and study in the Zetang orefield on the southern margin of the Gangdise belt. The LA-MC-ICPMS (laser probes) method was used to determine the zircon U-Pb isotope magma formation age and analyze the magma-forming tectonic background and the effects of natural resources. The zircon U-Pb isotope age of trondhjemites in the west of Zetang County is (156±1.0)~(152.5±1.3) Ma. The rocks are adakites, suggesting that the Paleo-Tethy ocean plate subducted northward and formed an intra-oceanic arc tectonic setting in Jurassic. The zircon U-Pb isotope age of host granodiorite rocks (adakites) of the Sangbujiala deposit located in the north of Zetang County is (94.1±0.96) Ma. The magma probably originated from melting of subduction block, and was contaminated by mantle wedge material. Magmatic evolution was closely related to the intra-oceanic subduction of Sangri Island Arc. There existed two phases of magmatic activities in the east of Zetang County, with the zircon isotope age of granodiorite being (63.0±1.0) Ma and (50.2±1.3)~(45.93±0.21) Ma respectively, both of them exhibited continental margin arc features, which indicates initial India-Asian collision. The zircon isotope age of adamellite in the east of Zetang Country is (31.64±0.47)~(29.88±0.39) Ma, and the petrogeochemistry of these two kinds of rocks shows different characteristics. The Chongmuda granites are adakitic rocks, while the Mingze granites are potassium-rich rocks. It is estimated that the adakitic magma came from the melting of India plate underneath the Lhasa Block. However, the two intrusive rocks are probably exotic blocks or are not original magma, whose geochemistry can not represent the tectonic and magmatic evolution of the Zetang polymetallic orefield. Based on the zircon isotope ages, petrology and geochemistry, the authors have reached the conclusion that the first four phases of

  2. Petrogenesis and geological significance of highly frac-tionated A-type granites in Kalasayi, East Junggar%东准噶尔喀拉萨依高分异A型花岗岩岩石成因及其地质意义

    Institute of Scientific and Technical Information of China (English)

    吴魏伟; 廖群安; 陈帅; 胡朝斌; 田健; 王富明; 樊光明


    Kalasayi granites are located in the westernmost part of the Kalamaili alkaline granite belt in East Junggar and are composed of moyite and adamellite. The LA-ICP-MS zircon U-Pb ages of Kalasayi granites are 307.7±3.2Ma~309.6±2.0Ma. The rocks have high silicon(SiO2 average of 77.25%), rich alkali(K2O+Na2O=7.50%~9.23%), low aluminum(A/CNK=0.922~1.084), and poor calcium and magnesium. They are also enriched in Rb, K, Th and other LILEs as well as in Zr, Hf and other high field strength ele⁃ments and rare earth elements, but are depleted in Ba, Sr, Eu. 10000Ga/Al values vary from 7.00 to 10.35. On the whole,Kalasayi granites exhibit characteristics of A-type granites and are highly fractionated products of the Laoyaquan-Huangyangshan A-type granites batholith on the eastern side instead to S-type granites as previously thought. Nd isotopic compositions of the Kalasayi gran⁃ites are positive(εNd(t)=3.5~6.0)and show young Nd model ages(TDM2=520~630Ma), with Pb isotope located near the orogenic evolution line, suggesting that the possible magma source might have been the lower part of the young fresh orogenic crust. The re⁃sults of the 1:50000 regional survey show that Kalamaili ocean basin was closed before the Late Devonian, and then entered into an extensional environment after collision and eventually into the rift stage in the Late Carboniferous. Kalasayi granites should be the products of rift environment rather than the products of post-collisional stage as previously thought.%喀拉萨依岩体位于东准噶尔卡拉麦里碱性花岗岩带西端,由钾长花岗岩和二长花岗岩组成。LA-ICP-MS锆石U-Pb年龄为307.7±3.2Ma~309.6±2.0Ma,岩石高硅(SiO2平均含量为77.25%)、富碱(K2O+Na2O=7.50%~9.23%)、低铝(A/CNK=0.922~1.084),贫钙、镁;富集Rb、K、Th等大离子亲石元素及Zr、Hf等高场强元素和稀土元素,亏损Ba、Sr、Eu。10000Ga/Al值变化于7.00~10.35之间,总体上具碱性A

  3. Tectonic Setting and Provenance Analysis of Late Paleozoic Sedimentary Rocks in the Ordos Basin%鄂尔多斯盆地晚古生代沉积岩源区构造背景及物源分析

    Institute of Scientific and Technical Information of China (English)

    陈全红; 李文厚; 胡孝林; 李克永; 庞军刚; 郭艳琴


    The provenances of Ordos Basin and its surrounding regions, which all comes from the upper crust, are dominated by felsic rocks, which consist of ancient metamorphic rocks, such as metamorphic volcanic rocks and sedimentary rock of Archaeozoic and Proterozoic, and certain amount of granite and alkali basalt. But compositions of source and structural setting of provenances in the north and south are different. Compositions of major and rare earth elements suggest that sedimentary rocks in both north and south show some differences in area and stratum, and the changes of major element, REE and Eu anomaly are in accordance with the variation trend from oceanic island arc, continental island arc, and active continental margin to passive continental margin. Analysis of major elements indicates that the north provenance derived mainly from plate subduction zones and were related to active continental margin and passive continental margin, with minor related to the island arc of passive continental margin, and were related to tectonic setting of active continental margin and passive continental margin until middle-late Paleozoic. REE contrast analysis shows that the source for the northern basin has affinities to Archeozoic and Proterozoic metamorphotic rocks, such as granitic gneiss, diorite gneiss, adamellite, metamorphotic litharenite, phyllite, etc; that for the southern basin was deeply affected by passive continental margin source, characterized by high SiO2, low Na2 O features, and K2 O/Na2 O > 1. All these features are consistent to those (high SiO2 and K2O/Na2O>l) of rocks of Archean-Proterozoic Taihua Group, Qinling Group and Kuanping Group. Until the end of Late Paleozoic, the provenance was not affected gradually by active continental margin. Beiqinling intermontane basins characterized by rapid accumulation m langes belong to the outer margin of Ordos Basin and have continuous transitional relationship with the basin. Therefore, both show some inherited

  4. Geochemical and Sr-Nd-Pb isotopic characteristics of the granitoids of Xiaoshan Mountain area on the southern margin of North China Block and its geological significance%华北陆块南缘崤山地区燕山期花岗岩地球化学、Sr-Nd-Pb同位素特征及其地质意义

    Institute of Scientific and Technical Information of China (English)

    李磊; 孙卫志; 孟宪锋; 杨小芬; 张灯堂; 冯建之


    Mountain area,China.Petrologically,adamellite is domain.Geochemically,according to major elements,eight granites are silicate and belong to high K-shoshonite series; all granites have similar trace element patterns (including REE),obvious partition of LREE from HREE (La/Yb) N =9.52 ~ 41.21 (avg.26.16),and weakly abnormal Eu (δEu =0.82 ~ 1.35),and enrich in Rb,Ba,Th,K,Pb,Hf and Y,and deplete in Ta,Nb,Zr,P and Ti.High Sr (392.8 ×10-6 ~916.9 ×10-6,avg.678.8 ×10-6),lowY (8.12 ×10-6 ~21.34 ×10-6,avg.14.86×10-6)and Yb (0.503 × 10-6 ~ 1.756 × 10-6,avg.1.26 × 10-6) characterize a garnet-bearing magma source in a thick lower crust under North China Block.Initial isotopic Sr ratio (Isr =0.70645 ~ 0.71022,avg.O.70828) and initial epsilon Nd (εNd (t) =-19.7 ~-3.4,avg.-14.6) disclose a crustal magma source.The proterozoic Nd depleted mantle model ages (t2DM) of the granites are concentrated in 1827 ~2372Ma,and present high radiogenic Pb and initial Pb ratios (206pb/204pb =17.728 ~ 18.720 (avg.17.905) ;207Pb/204pb =15.444 ~ 15.656 (avg.15.544) ; 208pb/204pb =37.519 ~ 38.707 (avg.38.187).All isotopic data suggest that the batholith was problebly formed by partial melting of the South Qinling crystalline basement with the participatioin of Taihua Group,Xiong'er Group and mantle materials.When extension environment substitute compression conditions caused by subduction of Yangtze Block with Qinling micro-block under North China Block,delamination of thick garnet-beating crust and asthenosphere upwelling provide heat to melt the thick bottom crust,and forward,to form magma.This suggests that the crystalline basement under South Qinlin Orogen through detachment in north direction into the crystalline basement of Xiaoshan Mountain area,and the north of Xiaoshan Mountain area probably is the northern margin of East Qinling Orogen.