Radioactive element distribution and rare-metal mineralization in anorogenic acid volcano-plutonic rocks of the Neoproterozoic Malani Felsic Province,western Peninsular India     

A. Krishnakanta Singh  G. Vallinayagam 《Journal of the Geological Society of India》2009,73(6):837-853

The Anorogenic Malani Felsic Province (MFP) of western Peninsular India consists of peralkaline, metaluminous to mildly peraluminous A-type granites-acid volcanics with minor basic volcanics and dykes. The suite is bimodal in nature that characterized by volcano-plutonic ring structures and radial dykes. The granitoids of Siwana and Kundal areas of MFP are traversed by numerous quartz veins with fluoride, iron encrustations, druses and knots of pegmatite phases. Petrographically, they show cloudy, patchy perthitic textures; spherulite form of alkali amphibole and alkali pyroxenes; alteration of K-Na-feldspar to kaolin/sericite, magnetite to haematite; growth of granophyres/perthite/rapakivi like textures. They are enriched in SiO₂, Na₂O+K₂O, Fe/Mg, Rb, Zr, Y, Ga, REE (except Eu) and depleted in MgO, CaO, Mg#, P, Ti, Sr, Ni, Cr, Co and V. Uniform REE patterns, parallel to sub-parallel, LREE enriched over HREE and prominent negative Eu-anomalies are the characteristics of these granitoids. Geochemical parameters satisfy the A-type nature of granitoids and crustal origin of these rocks. These granitoids are high heat producing granitoids because of their high content of radioactive elements (U, Th, K), and can be classified as granite (Type I) (avg. 7.18 μWm⁻³), rhyolite and trachyte (Type II) (avg. 4.47 μWm⁻³) and acid dyke (Type III) (avg. 14.53 μ Wm⁻³). The average total heat generation unit (HGU) of Type I (17.10 HGU), Type II (10.64 HGU) and Type III (35.31 HGU) are much higher than the average value of continental crust (3.8 HGU), which imply a possible linear relationship among the surface heat generations in the MFP. Field, petrography and whole rock geochemical characteristics suggest potentiality for rare metals and rare earth elements mineralization in the studied granitoids of the MFP.  相似文献   

中上扬子印支运动的地层学效应及晚三叠世沉积盆地格局   总被引：6，自引：0，他引：6       下载免费PDF全文

梅冥相 《地学前缘》2010,17(4):99

发生在晚三叠世的印支运动,结束了中上扬子地区自伊迪卡拉纪以来以一个稳定的古地理单元、而且多数时间沉积浅水碳酸盐岩的漫长的地质历史。该地质事件受控于秦岭造山带的大规模造山隆升和华北板块的向南强烈挤压,并在华夏地块的北西向挤压,以及印支板块的向北挤压的共同作用下,在习称的"扬子地台"的相对较为稳定的基底上于晚三叠世形成一个从残留海相盆地到具有前陆性质的陆相磨拉石盆地的演变序列;而且,这个特别的盆地演变序列与松潘—甘孜地块上发育的晚三叠世前陆浊积盆地的形成和消亡过程存在时间上的对应性。因此,对中上扬子区印支运动的地层学效应以及由此而产生的沉积盆地格局演变的系统描述,为窥视古特提斯洋消亡过程提供了重要线索,而且为重新审视长期以来作为前陆盆地典型代表的、由龙门山造山带的造山隆升所形成的"四川盆地西部前陆盆地"假象提供了一个思考的途径。  相似文献   

Mesoproterozoic rift-related alkaline magmatism at Elchuru, Prakasam Alkaline Province, SE India   总被引：6，自引：0，他引：6  

D. Upadhyay  M.M. Raith  K. Mezger  K. Hammerschmidt 《Lithos》2006,89(3-4):447-477

The Elchuru alkaline complex in the Prakasam igneous province represents one occurrence of several alkaline bodies within the craton–Eastern Ghats Belt contact zone in Peninsular India. Nepheline syenites and associated mafic rocks intruded the cratonic crust at ≈1321 Ma and were deformed–metamorphosed to amphibolite facies condition during Pan-African times. Trace element compositions and Sr, Nd and Pb isotopic systematics indicate that the alkaline magma was derived from an enriched mantle source in the sub-continental lithosphere. The adjacent crusts of the Eastern Dharwar craton and the Eastern Ghats Belt were not involved either as source or as contaminants. The enriched mantle source was at least 1.9–2.1 Ga old as seen from the depleted mantle model ages of the rocks. The primary parent magma was a basanitic liquid that fractionated ferrokaersutite and clinopyroxene in the mantle, lowering the density sufficiently for the residual melt to intrude the crust. Magmatic differentiation in the suite can be explained by a two stage fractional crystallization model involving the removal of amphibole, clinopyroxene, allanite, titanite, apatite and zircon. The rift-related intra-continental setting of the complex indicates that alkaline magmatism represents the manifestation of a Mesoproterozoic continental breakup. Rifting along the cratonic margin may have led to the formation of several cratogenic basins (e.g., Chattisgarh basin, Indravati basin etc.) where stable shelf-type sediments could have been deposited on the passive margin during the Proterozoic. It could also have opened an ocean where some of the sediments of the Eastern Ghats Province may have been deposited.  相似文献   

INTERPRETATION OF COPPER AND ZINC CONTAMINATION IN THE AQUATIC ENVIRONMENT OF PENINSULAR MALAYSIA WITH SPECIAL REFERENCE TO A POLLUTED RIVER, SEPANG RIVER   总被引：2，自引：0，他引：2  

Chee Kong Yap Ahmad Ismail Ching How Low Soon Guan Tan 《湿地科学》2007,5(4):311-321

Three different aquatic ecosystems(an urban pond,Kelana Jaya Pond;a polluted river,Sepang River;and the intertidal and offshore areas of the west coast of Peninsular Malaysia)with different sets of ecological backgrounds and human activities were reviewed and assessed for the levels of Cu and Zn contamination with special reference to those found in polluted sediments collected from the Sepang River.The discussion on the contamination levels of Cu and Zn in the aquatic environment of Peninsular Malaysia was based on a comparison of the metal contamination of 4 kinds of aquatic environments.The comparison of 4 different areas was based on ① total concentrations of 2 metals;② the concentrations and percentages of the nonresistant(EFLE,acid-reducible and oxidisable-organic)and resistant geochemical fractions;and ③ correlation coefficients(R-values)based on data of 4 areas separately and a combination of 4 areas.The Sepang River recorded nonresistant fractions of 63.1% for Zn and 55.8% for Cu in addition to slightly lower metal concentrations when compared to those(60%-70%)reported before the shutting down of the piggery activities in that area.These nonresistant metal percentages(55%-63%)indicated that the metal concentrations were still dominated by anthropogenic sources since nonresistant fraction of metals were mostly contributed by anthropogenic sources.The positive results from the four different aquatic environments assessed here provided strong evidence to show that Malaysia's aquatic environment had received anthropogenic Cu and Zn.The present study also showed that the percentage of the nonresistant fraction and the R-values based on correlation analysis of Cu and Zn could be used as indicators of Cu and Zn pollution in the Malaysian aquatic ecosystem.Based on the present data,the correlation coefficients(R-values)are potential indicators of EFLE Cu and acid-reducible Cu of the sediments.The use of R-values as indicators of metal pollution is suggested and it is applicable to other heavy metal data although it should be improved in future studies.  相似文献   

Structural relations of charnockites of the Archaean Dharwar craton, southern India     

K. NAHA  R. SRNIVASAN  S. JAYARAM 《Journal of Metamorphic Geology》1993,11(6):889-895

Abstract Two varieties of charnockites are recognized in the Dharwar craton of southern India. The style and sequence of structures in one charnockite variety, and related intermediate to basic granulites, are similar to those in the supracrustal rocks of the Dharwar Supergroup and the adjacent Peninsular Gneiss. This style has isoclinal folds with long limbs and sharp hinges with an axial planar fabric in some instances. Additional evidence of flattening is provided by pinch-and-swell and boudinage structures, with basic granulites forming boudins in the more ductile charnockites/enderbites in the limbs of isoclinal folds. These folds are involved in near-coaxial upright folding resulting in the bending of the axial planes of the isoclinal folds and the associated boudins. All these structures are overprinted by non-coaxial upright folds with axial planes striking nearly N–S. The map pattern of charnockites suggests that this sequence of structures is present not only on a mesoscopic scale, but also on a macroscopic scale. Charnockites of this variety provide, in some instances, evidence of having been migmatized to give rise to hornblende–biotite gneiss and biotite gneiss, which form a part of the Peninsular Gneiss terrane.
The second variety comprises charnockite sensu stricto with an entirely different structural style. This type occurs in the tensional domains of the hinge zones of the later buckle folds, in the necks of foliation boudinage, in shear zones and in release joints parallel to the axial planes of the later folds in the Peninsular Gneiss. Because the non-coaxial later folds are associated with a strain pattern different from, and later than, that of the isoclinal folds of the first generation, it follows that charnockites of the Dharwar craton have evolved in at least two distinct phases, separate both in time and in process.  相似文献   

The Early Triassic Indosinian orogeny in Vietnam (Truong Son Belt and Kontum Massif); implications for the geodynamic evolution of Indochina   总被引：8，自引：0，他引：8  

C. Lepvrier  H. Maluski  Vu Van Tich  A. Leyreloup  Phan Truong Thi  Nguyen Van Vuong 《Tectonophysics》2004,393(1-4):87

New structural field data at various scale and ⁴⁰Ar–³⁹Ar geochronological results, from the basement rocks in the Truong Son belt and Kontum Massif of Vietnam, confirm that ductile deformation and high-temperature metamorphism were caused by the Early Triassic event of the Indosinian Orogeny in the range of 250–240 Ma. A compilation of isotopic data obtained in other countries along the Sibumasu–Indochina boundary broadly indicates same interval of ages. This tectonothermal event is interpreted as the result of a synchronous oblique collision of Indochina with both Sibumasu and South China, inducing dextral and sinistral shearing along E–W to NW–SE and N–S fault zones, respectively. The collision along Song Ma follows the northwards subduction of Indochina beneath South China and the subsequent development of the Song Da zone which in turn was affected by the Late Triassic Indosinian phase of shortening. Within the Indochina plate, internal collisions occurred coevally in the Early Triassic, as along the Poko suture, at the western border of the Kontum Massif.  相似文献   

胶东山后金矿床地质体微量元素特征及找矿意义   总被引：3，自引：0，他引：3  

徐述平  邓军  高帮飞  杨立强  江少卿 《地质与勘探》2008,44(5):23-29

对胶东招平断裂上的山后金矿34个钻孔进行了原生晕测量,分析了Au、Ag、cu、Pb、zn、As、Sb、Bi、Mo、Hg等10种元素,统计了胶东岩群、荆山群、玲珑花岗岩及招平断裂蚀变带中微量元素含量及变化.变质岩、花岗岩均富Bi、Ag,而贫Hg、Sb、Au、Cu、zn、As;胶东岩群、荆山群中金的丰度值相近,它们均为金矿的矿源岩;在招平断裂蚀变带中Au、Ag、Pb、Mo、Bi等元素出现了明显富集,而Cu、zn、Sb、Hg等元素没有富集,矿床多金属硫化物阶段不发育;根据聚类分析结果,Au与Ag、Cu、Pb、zn生成于不同的成矿期,招平断裂中的Au矿体形成于金成矿期,招平断裂上盘荆山群地层中的Au、Ag、cu、Pb、Zn多金属矿体形成于金银多金属成矿期;招平断裂北段的成矿条件要比南段好;根据As、Mo元素含量的变化,确定出山后金矿深部矿体预测的简单准则,并对金矿深部进行了简单成矿预测.  相似文献   

THE TIMING OF SOUTH-ASIAN HIGH ESTABLISHMENT AND ITS RELATION TO TROPICAL ASIAN SUMMER MONSOON AND PRECIPITATION OVER EAST-CENTRAL CHINA IN SUMMER     

王黎娟  郭帅宏  葛静 《热带气象学报(英文版)》2016,22(2):136-144

The timing of the South Asian High (SAH) establishment over the Indochina Peninsula (IP) from April to May and its relations to the setup of the subsequent tropical Asian summer monsoon and precipitation over eastern-central China in summer are investigated by using NCEP/NCAR daily reanalysis data, outgoing longwave radiation (OLR) data and the daily precipitation data from 753 weather stations in China. It is found that the transitions of the zonal wind vertical shear and convection establishment over tropical Asia are earlier (later) in the years of early (late) establishment of SAH. In the lower troposphere, anti-cyclonic (cyclonic) anomaly circulation dominates the equatorial Indian Ocean. Correspondingly, the tropical Asian summer monsoon establishes earlier (later). Furthermore, the atmospheric circulation and the water vapor transport in the years of advanced SAH establishment are significantly different from the delayed years in Asia in summer. Out-of-phase distribution of precipitation in eastern-central China will appear with a weak (strong) SAH and western Pacific subtropical high, strong (weak) ascending motion in the area south of Yangtze River but weak (strong) ascending motion in the area north of it, and cyclonic (anti-cyclonic) water vapor flux anomaly circulation from the eastern-central China to western Pacific. Accordingly, the timing of the SAH establishment at the upper levels of IP is indicative of the subsequent onset of the tropical Asian summer monsoon and the flood-drought pattern over eastern-central China in summer.  相似文献   

相山火山盆地南部印支期富铀岩体岩石学及主微量元素特征   总被引：1，自引：1，他引：0       下载免费PDF全文

周万蓬  范洪海刘林清  姜勇彪 《中国地质》2015,(6):1897-1897

通过对咸口岩体进行岩石学、主微量元素分析,发现其为一套印支期富铀复式岩体,具富硅、高钾、弱过铝质特征,属高钾钙碱性系列岩石;其稀土元素配分型式具右倾斜特征,富轻稀土,轻稀土分馏比重稀土明显,铕亏损明显;微量元素Nb、Ce、Pr、Zr、Ba明显亏损,而Rb、Th、U、Pb、Ta、Nd、Hf元素富集,Rb/Sr比值变化大(0.92~6.52);岩体平均铀含量为19.55×10-6,属富铀花岗岩体。由主微量元素构造环境判别,结合区域地质背景分析,咸口岩体为板内后造山构造环境下形成的富铀花岗岩体。相山南部咸口富铀岩体的发现为解决相山铀矿田的铀源问题提供了新的思路,也有望指引在相山南部寻找花岗岩型铀矿床。  相似文献   

胶东邢家山地区燕山早期钼钨成矿母岩锆石U-Pb年龄及其意义   总被引：2，自引：0，他引：2       下载免费PDF全文

丁正江  孙丰月李国华纪 攀  孔彦 《中国地质》2015,(2):556-569

对从幸福山花岗岩中挑出的岩浆锆石进行了LA-ICP-MS分析,得出了由15个点组成的加权平均值为(157±2)Ma的年龄。此15个测试点均处于岩浆锆石的振荡环带上,且此年龄与邢家山钼钨矿辉钼矿Re-Os年龄一致,代表该花岗岩的结晶年龄。本次测试所得到的另外2组捕获锆石年龄(2798±13)Ma和(2250±18)Ma暗示该岩浆源区可能存在的新太古代-古元古代侵入岩基底,(230±6)Ma则可能暗示着该区存在三叠纪的岩浆活动。中生代以来(190~110 Ma),中国东部构造岩浆活动特征较为一致,与之相对应存在多期成矿作用。胶东地区广泛出露的玲珑花岗岩与幸福山花岗岩岩石地球化学特征及年龄基本一致,可能该区也存在着大规模的钼多金属成矿作用,只是大部分为后期构造抬升所剥蚀,邢家山钼钨矿是保存下来的代表。也说明,栖霞—福山地区中生代以来剥蚀程度相对较小,矿床保存条件较好,故应重视该区中浅成矿床(斑岩-矽卡岩型、卡林型、造山型浅成矿床等)的寻找。  相似文献