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Sample records for adamellite

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

    Martín Patino, M. T.; Guijarro, J.; Casas, J; Martín de Vidales, J. L.

    1988-01-01

    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...

  2. Lead isotope systematics of some igneous rocks from the Egyptian Shield

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

    1983-01-01

    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.

  3. The Geochemical Characteristics of Zheduoshan Super-Unit in Kangding County Sichuan Province%四川康定折多山超单元地球化学特征

    牟业龙; 王永智; 王建军

    2015-01-01

    According to the comagmatic evolution succession of granite,Zheduoshan super-unit granite in Kangding County is divided into three units. The rock association characteristics are coarse grained monzonitic granite ,middle granularity adamellite and fine-grained adamellite. Granite has obvious composition-texture evolutionary character. Its isotopic age is 3.75-15.4 Ma,and it belongs to Himalayan S-type granite. By analyzing the data of petrochemistry, rare earth element and microelement,we discussed the material source,structural setting and structural origin of Zheduoshan in pluton.%根据花岗岩同源岩浆演化序列,将康定县折多山超单元花岗岩体划分为3个单元,岩石组合特征为粗粒似斑状二长花岗岩、中粒二长花岗岩、细粒二长花岗岩,具有明显的成分-结构演化特征,同位素年龄为3.75~15.4 Ma,时代属喜马拉雅期的S型花岗岩. 通过岩石化学、稀土元素、微量元素等数据的分析,论述了折多山岩体的物质来源、构造环境及其成因.

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

    ZHANG BangTong; WU JunQi; LING HongFei; CHEN PeiRong

    2007-01-01

    The U-Th-40K concentrations of granite are on 1-2 orders of magnitude greater than those of basaltic-ultrabasic rocks. Radiogenic heat of a granitic melt has significant influence on the cooling-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 formula and radioactive element concentrations (U=5.31x10-6; Th=23.1x10-6; 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.

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

    2007-01-01

    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. Finding of 192 Ma granitic cobbles from the cape shiretoko area, eastern Hokkaido, Japan

    Goto, Y. (Hokkaido University, Sapporo (Japan). Fauclty of Agriculture); Gouchi, N. (Shiretoko Musen, Hokkaido (Japan)); Itaya, T. (Okayama University of Science, Okayama (Japan))

    1991-09-05

    Cobbles of granitic rocks were found from the seashore of the Cape Shiretoko area, Shiretoko Peninsula, eastern Hokkaido, Japan. They exhibit rounded to subrounded shape, and are 5 to 20 cm in length. The petrographical study, chemical analysis of major elements of bulk rocks, and K-Ar dating were carried out to clarify the origin of the granitic cobbles. The cobbles are composed of adamellite, granodiorite and quartz monzonite. Most of them show a hypidiomorphic texture, and some granodiorite and quartz monzonite have a mylonitic texure. K-Ar ages are 191.8 for biotite in adamellite, 114.6 Ma for K-feldsper in mylonitized granodiorite and 124.2 Ma for muscovite in mylonitized quartz monzonite. The granitic cobbles found at Cape Shiretoko are similar in age and petrography to the granitic rocks dredged from the Sea of Okhotsk. this fact indicates that the granitic cobbles were derived from granitic rocks forming the continental crust in the okhotsk region. 20 refs., 3 figs., 2 tabs.

  7. Distribución de uranio y torio en la apófisis adamellítica de Logrosán (Cáceres, España

    Guijarro Galiano, J.

    1986-12-01

    Full Text Available Logrosan apophyses (Cáceres, España has two differents petrographic types: a porphyritic two mica adamellite and a porphyritiv two mica microadamellite. It's an alkaline with silico-sodic trend and peraluminous granitoid. A greisen alteration has been produced by the tin-veins in the host-rock.
    The moderatly high content values of uranium are ranged between 6.9 and 11.9 ppm, with a mean of 9.5 ppm. Thorium has lower concentrations levels. The Th/U ratio has an average value of 0.8.
    The fact that thorium ís correlated positivels with ferromagnesian elements indicates that is probably contained within the boitites.
    Higher thorium and uranium values are founded in the adamellite type.
    Greisen has produced an uranium leaching that would be important as uranium mineralization source outside the apophyses. Although has not been observed uranium mineralizations in the geological area study.

    La apófisis de Logrosán (Cáceres, España está constituida por una adamellita y una microdamellita, ambas de dos micas. Geoquímicamente presenta un carácter marcadamente alcalino, con una tendencia silicosódica clara, y peraluminoso. Los filones estanníferos existentes han producido una greisenificación en la roca encajante.
    El fondo geoquímico del uranio está comprendido entre 6,9 y 11,9 ppm, con un valor medio de 9,5 ppm, y es ligeramente superior al habitual para estos materiales. El fondo del torio es inferior y el valor medio de la relación Th/U es de 0,8.
    Existe una buena correlación positiva entre el torio y los elementos ferromagnesianos. Probablemente se encuentra asociado a las biotitas.
    Los fondos geoquímicos más altos, en torio y uranio, corresponden a la facies adamellítica.
    La greisenificación ha provocado una lixiviación de uranio que ha podido actuar como fuente para posibles mineralizaciones extraplutónicas, aunque en el estudio geológico de la zona no han sido

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

    2006-01-01

    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.

  9. Geologic Characteristics and Genesis of the Jinghou Molybdenum Deposit in Jianyang City, Fujian Province%福建建阳井后钼矿地质特征及成因探讨

    章振国

    2011-01-01

    建阳井后钼矿位于闽西北隆起带东缘,浦城一永泰南北向构造岩浆活动带中部。矿床形成于燕山晚期,主要受区域上南北向断裂构造带控制的隐伏斑岩体控制。矿体以线脉一细脉及石英大脉型为主,围岩为中一晚元古代马面山群大岭组变质岩与加里东期二长花岗岩。%The Jinghou molybdenum deposit in Jianyang City is situated at the east fringe of Northwestern Fujian mole track, in the middle of the Pucheng-Yongtai north-south-trend fault zone. It was formed in late Yenshanian, and controlled by blind porphyry body, Which was controlled by Pucheng-Yongtai north-south-trend fault zone. There are three typical types of ore: line-vein Type, veinlet type, quartz vein type. ; quartz vein type and structurally altered rock type. The wall-rock lithology was metamorphic of the Daling Formation of Mamianshan Group in Mid-Proterozoic and adamellite in Caledonian epoch.

  10. Rare earth elements content in geological samples from eastern desert, Egypt, determined by instrumental neutron activation analysis

    Twenty representative geological samples (tonalite, granodiorite, adamellite, syenogranite, rapakivi syenogranite, alkali feldspar granite and monzogranite) were collected from G. Kattar area in Eastern Desert, Egypt, for analysis by instrumental neutron activation as a sensitive nondestructive analytical tool for the determination of 14 rare earth elements (REEs) and to find out the following: (1) what information could be obtained about the REEs and distribution patterns of REEs in geological samples under investigation, (2) to estimate the accuracy, reproducibility and detection limit of the INAA method in case of the given samples. The samples were properly prepared together with standard reference material and simultaneously irradiated in a neutron flux of 7x1011 n/cm2 s in the TRIGA Mainz research reactor facilities. The gamma spectra were collected by an HPGe detector and the analysis was done by means of a computerized multichannel analyzer. The choice of the nuclear reaction, irradiation and decay times, and of the proper gamma radiation in counting are presented and discussed. The results are found to be in good agreement with certified values.

  11. Mantle influence on the character of I-type granitoids of the New England batholith: evidence from Sr and Nd isotopes

    Granitoid samples, together with an array of mafic to felsic dyke rocks, were collected from both the southern members of the high-K Moonbi Suite (Moonbi district) and the southern members of the low-K Clarence River Suite (Barrington Tops Granodiorite). These constitute the two most divergent compositions in the spectrum of I-type granitoids in the New England Batholith. Mafic plutonic rocks (quartz diorites) also coexist with granitoids at Barrington Tops (Eggins and Hensen 1987), and mafic dykes (high-K lamprophyres) have been observed in association with Moonbi Suite granitoids in the Hillgrove area (Kent 1994). Kent (1994) noted that lamprophyres in the Rockvale area extend the linear trends of the Moonbi granitoids on Harker plots, and the petrographic and chemical similarities between mafic and felsic intrusives at Barrington Tops have been described by Eggins and Hensen (1987). Shaw et al. (1992) also noted that lamprophyre dykes at Tulcumba Ridge (to the west of Tamworth) have similar ages and initial Sr isotopic compositions to Moonbi Suite granitoids (87Sr/86Sri 0.7042-0.7048). Lamprophyre dykes and felsic dykes of dacitic composition within the Moonbi Adamellite and the surrounding area were analysed for their Sr and Nd isotopic compositions, in an attempt to determine a link between mafic, mantle derived magmas and their granitoid hosts. Although isotopic and geochemical evidence provides a clear link between mantle-derived mafic magmas and granitoids within both the Moonbi and Clarence River suites, a clear explanation of the mechanisms and source rocks involved in magma generation remains elusive. Of critical importance is identification of the character of the lower crustal sources involved in each case, and clarification of the mechanism of interaction between the mantle and crustal sources. In particular, although the lamprophyres associated with the Moonbi Suite appear partly responsible for the isotopic and geochemical character (in particular

  12. Geological Characteristics and Genesis of the Spodumene Deposit in Dangba, Barkam, Sichuan Province%四川省马尔康党坝锂辉石矿床地质特征及成因研究

    庞博; 古城会; 李良波; 罗伟; 李剑

    2015-01-01

    马尔康党坝锂辉石矿位于松潘-甘孜造山带、巴颜喀拉造山带之马尔康复式向斜之南端.矿区出露三叠系地层,断裂、褶皱构造较发育,岩浆岩以燕山晚期二云二长花岗岩为主,是花岗伟晶岩脉的母岩.锂辉石矿体呈大脉状产出,矿石矿物有锂辉石、钽铌铁矿、锰锂矿等,脉石矿物有石英、微斜长石、钠-更长石.矿石结构为细粒-中粒结构,次为交代结构、熔蚀结构.矿石构造以块状构造为主,次为似斑状、浸染状和条带状构造.围岩蚀变主要为锂云母化、白云母化和黑云母化,成因类型为伟晶岩矿床.%Barkam county Dangba spodumene deposit is located in Songpan-Ganzi orogenic belt, the southern tip of the Barkam of the Bayan Har orogenic belt. The mining area outcrops of Triassic strata. Fractures and fold structures are developed. Magmatic rocks contains mostly the late Yanshanian the dimicaceous adamellite, that is parent rocks of granitic pegmatite veins. The orebodies are the large vein outputs. The ore minerals are spodumene, tantalum-niobium-iron ore, lithium manganese ore, and so on. Gangue minerals are quartz, feldspar, albite-oligoclase. The ore structures have fine-grained-medium-grained structure, and then account structure, corrosion structure. Ore constructed to massive structure based, and then porphyritic, disseminated and banded structure. Wall rocks alteration mainly includes lepidolitization, muscovitization and biotitization. Genetic type is pegmatite deposits.

  13. 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

    武昱东; 王宗起; 罗金海; 程家孝; 闫全人; 张英利; 王师迪

    2014-01-01

    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

  14. 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

    武昱东; 王宗起; 罗金海; 程家孝; 闫全人; 张英利; 王师迪

    2014-01-01

    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 8.85, an average(La/Yb)N value of 9.54 and an average δEu value of 0.31. The chondirte-normalized REE patterns display right-oblique curves. The large ion lithophile elements, such as Rb, Th, U and K, are rel- atively enriched, whereas high HFSE such as Nb, Ta, Sr and Ti are relatively depleted, which indicates the existence of residual plagio-clase in the granite source area. Calculation also shows that the melt of Xiatianba granites was formed in an intraplate extension environ-ment with temperatures between 724℃and 786℃. These characteristics show that the Xiatianba granites are typical A-type granite. LA-ICP-MS U-Pb dating of zircon from biotite adamellite yielded a granite age of 801.1±6.6Ma (MSWD=0.84, n=14) and a ther-mal event age of 762.1 ± 6.2Ma (MSWD=0.72, n=14), which are highly in accordance with the time of breakup of Rodinia super-continent in the western Yangtze block, and are also consistent with the metallogenic epoch of the Dongchuan copper deposit, sug-gesting that the magmatism of the Neoproterozoic rift environment affected Dongchuan area and probably triggered hydatogenesis mineralization.%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%

  15. 吉林和龙地区主要金属矿床成矿地质特征及找矿方向%Metallogenic Geological Characteristics and Prospecting Potential of Main Metal Deposits in Helong Area,Jilin

    胡春廷

    2016-01-01

    deposit;the main deposit methods are geological mapping,geological rock section,trenching,geophysical prospecting (induced electrical)and drilling. Based on looking for deep and hidden mines,the prospecting should be explored regionally along the NW fault and secondary fault,different lithological contact surface of the northern Huifa River.Especially, the exploration work should pay attention to the intersection part of EW fault structure and NE and NW fault structure,strong silicified altered rocks or quartz veins outcropping site,invasion section of adamel-lite or granodiorite porphyry or granite-porphyry,ploymetallic abnormal development section,etc.

  16. Zircon U-Pb ages and geological significance of the granitoids in the Yi'ershi region,Daxing′anling%大兴安岭伊尔施地区花岗岩锆石U-Pb 年龄及其地质意义

    郭峰; 白志达; 李路路

    2014-01-01

    伊尔施花岗岩位于大兴安岭中段,出露面积约260km2,由中细粒二长花岗岩、中粗粒斑状正长花岗岩和中粗粒正长花岗岩三期侵入体构成。岩体侵入于石炭-二叠系地层,被晚侏罗世火山岩不整合所覆。锆石LA-ICP-MS U-Pb年龄为(226.3±1.4) Ma ,表明为晚三叠世花岗岩。花岗岩具有高硅、富碱、低钙的特征,属于弱过铝质岩石。稀土元素总量较高,轻稀土相对富集,重稀土相对亏损,Eu负异常明显。强不相容元素富集,亏损Ba、S r、P和T i。总体属于高钾钙碱性系列向碱性系列过渡的花岗岩,具有后造山花岗岩类(POG )的特征,形成于挤压造山向拉张体制转变阶段的构造环境,暗示该区受西伯利亚板块和华北板块碰撞造山作用的影响持续到三叠纪。%Yi’ershi granite located in the middle of Daxing ’anling area ,about 260 km2 .It consists of three phase intrusions , the middle-fine grained adamellite ,coarse-grained grained porphyritic orthoclase granite and coarse-grained orthoclase granite ,respectively .Pluton intruded into the Carboniferous-Permian strata ,and the Late Jurassic volcanic rocks are unconformably overlying them .Zircon LA-ICP-MS U-Pb dating ages of the pluton is (226 .3 ± 1 .4) Ma ,indicates that the Late Triassic granite .The granitoid has the characteristics of high silica ,alkali-rich ,low calcium ,belongs to the weakly peraluminous rocks .Total REE abundance is variable ,rich of HREE ,and the fractionation of LREE is more than that of HREE relatively ,and by obivious Eu anomalies .Strong incompatible elements are enrichment ,lack of Ba ,Sr ,P and Ti .Overall belong to the transition series from high-K series to calc-alkaline series granite ,shows the characteristics of typical post-orogenic granite (POG ) .It mainly formed in the transition phase from the extrusion orogenic to extensional regime tectonic environment , which suggesting the

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

    Martín Patino, M. T.

    1988-08-01

    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

  18. 西藏山南地区明则斑岩钼矿床蚀变矿化特征与成矿时代%Characteristics of Alteration and Mineralization and Chronology of the Mingze Porphyry Mo Deposit in the Shannan Area of Southern Tibet

    范新; 李光明; 黄树峰; 琚宜太; 陈雷; 秦克章; 肖波; 李金祥; 李秋平; 陈玉水; 陈金标; 赵俊兴

    2011-01-01

    The Mingze porphyry Mo deposit is located in the southeastern margin of the Candese metallogenic belt,north of the Yarlung Zangbo River suture zone. A variety of intrusions outcrop such as moyite, biotite monzogranite, granodiorite, porphyaceous adamellite and granite porphyry. The granite porphyry is the ore-fronting related intrusion which is completely mineralized. Wall rocks suffered extensive alteration, mainly as potassic, silicification, chloritization, kaolinization and skam alteration. Various types of alteration have the characteristics of vertical variations, and skarn formed where the intrusions interact with carbonate wall rocks. Potassic and silicification alteration occurred at deeper levels. Mineralization of the Mingze deposit also shows vertical variation. Cu and W mineralization in skarn formed in the relatively shallow subsurface, and Mo (Cu) mineralization in porphyry occurred at larger depths. Porphyry mineralization has vertical zoning characteristics. Texture of ores mainly includes massive, veinlet and disseminated form. Ore minerals mainly consist of molybdenite,chalcopyrite,pyrite and a little of bomites and scheelit. We selected pure biotite for the 40Ar-39Ar dating from the biotite-pyrite vein. The results show the plateau age is 28. 2±0. 33Ma,which coincides with the age of Re-Os. Combined with metallogenetic age previously reported, this age represents the metallogentic age of the southern belt of Cangdese between 30. 26Ma - 23. 62Ma. Which is obviously different from the northern or middle belt of the Candese metallogenic belt Dating of the metallogenic epoch of the Mingze deposit provides sound evidence for the multi-stage mineralization and the evolution of ore-forming related to the extensive tectono-magmatic activities.%明则斑岩钼矿床位于冈底斯成矿带的东南缘,雅鲁藏布江缝合带北侧.矿区内主要出露有钾长花岗岩、黑云母二长花岗岩、花岗闪长岩、似斑状二长花岗岩及花岗

  19. Post-Collision Related Late Indosinian Granites of Gangdise Terrane:Evidences from Zircon U-Pb Geochronology and Petrogeochemistry%冈底斯印支晚期后碰撞花岗岩:锆石 U-Pb年代学及岩石地球化学证据

    王程; 魏启荣; 刘小念; 丁鹏飞; 卜涛; 孙骥; 张小强; 王敬元

    2014-01-01

    The lithology,LA-ICP-MS zircon U-Pb age,major and trace element geochemistry,Sr-Nd-Pb isotope compositions of Dabula pluton from the middle part of the Gangdise granitoid belt are systematically studied in the paper.Results suggest that the rock type is adamellite,and the pluton is composed of middle-fine grained border facies and middle-coarse grained cen-tral facies.The two facies yield weighted mean ages of 230.6±4.3 Ma-228.2±3.5 Ma,with the corresponding age of Late Triassic.The rocks are relatively rich in SiO2 and kalium,with SiO2 content between 71.79%-77.27%;relatively high K(w (K2 O)=4.06%-5.26%)and low Ti(w(TiO2 )=0.06%-0.40%)contents;A/CNK varies from 1.16-1.19,displaying strong peraluminous characteristics and sharp negative Eu anomalies (δEu=0.06-0.35).Trace element ratio spider diagram displays apparent enrichments of Rb,Th elements,and marked depletions of Ba,Nb,Sr,P and Ti The Sr-Nd isotopes show the granite bodies have the high initial 87 Sr/86 Sr ratios (0.712 7-0.720 1)and the negativeεNd (t)(-10.6)results.Pb isotope feature shows the enrichment of radiogenic Pb.It is concluded that the Dabula pluton was formed by partial melting of mature crustal materials from Gangdise resulted from the underplating of the subduction-related basaltic magmas during the post-colli-sional extention in the dynamic background associated with the southward Bangong-Nujiang Tethyan seafloor subduction trig-gered by the collision between the northern Australia and Lhasa terranes.%对出露在冈底斯中带的达布拉岩体进行了系统的岩石学研究、LA-ICP-MS 锆石 U-Pb 定年、岩石地球化学分析、Sr-Nd-Pb 同位素组成的讨论.结果显示,达布拉岩体的岩石类型为二长花岗岩,由中细粒的边缘相和中粗粒的中央相组成,成岩年龄为230.6±4.3 Ma~228.2±3.5 Ma,属晚三叠世.岩体具高 Si(w(SiO2)=71.79%~77.27%)、高 K(w(K2 O)=4.06%~5.26%)、低 Ti